Human Health Soil Investigation Guidance Remediation Division Minnesota Pollution Control Agency
September 2016
Minnesota Pollution Control Agency 520 Lafayette Road North | Saint Paul, MN 55155-4194 | 651-296-6300 | 800-657-3864 | Or use your preferred relay service. |
[email protected] This report is available in alternative formats upon request, and online at www.pca.state.mn.us. Document number: c-r1-14
Contents Contents ............................................................................................................................................ i Acronyms .........................................................................................................................................iii 1.0
Introduction .........................................................................................................................1
2.0
Soil investigation ..................................................................................................................2
2.1
Information investigation ...................................................................................................................... 3
2.2
Initial soil investigation .......................................................................................................................... 4
2.3
Remedial soil investigation .................................................................................................................... 6
3.0
Field screening .....................................................................................................................9
3.1
Physical screening methods .................................................................................................................. 9
3.2
Photoionization detectors ..................................................................................................................... 9
3.3
Flame Ionization Detectors ................................................................................................................. 10
3.4
Portable gas chromatography detectors ............................................................................................. 10
3.5
Electron capture detector ................................................................................................................... 10
3.6
Electrolytic conductivity detector ....................................................................................................... 10
3.7
Surface acoustic wave sensors ............................................................................................................ 11
3.8
Spectrophotometry ............................................................................................................................. 11
3.9
Test kits/Immunoassays ...................................................................................................................... 12
3.10 Direct push platform ........................................................................................................................... 13 3.11 Mobile lab ............................................................................................................................................ 13
4.0
Soil sampling ......................................................................................................................14
4.1
Sample collection tools........................................................................................................................ 14
4.2
Sampling methods ............................................................................................................................... 14
4.3
Sampling design ................................................................................................................................... 16
4.4 Sampling Design Considerations .............................................................................................................. 19 4.5
5.0
Quality assurance/Quality control....................................................................................................... 20
Using soil reference values .................................................................................................21
5.1
Exposure pathways and receptors ...................................................................................................... 21
5.2
Sampling .............................................................................................................................................. 22
5.3
Exposure concentrations ..................................................................................................................... 23
5.4
Applicable LUC SRVs ............................................................................................................................ 23
5.5
Risk characterization ........................................................................................................................... 24
5.6
Uncertainty .......................................................................................................................................... 28
5.7
Conclusion ........................................................................................................................................... 28
6.0
Additional soil considerations .............................................................................................30
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7.0
Site specific background .....................................................................................................31
7.1
Site dataset vs. BTV using proportions test ......................................................................................... 31
7.2
Comparing site and background dataset............................................................................................. 33
8.0
Site specific soil cleanup values...........................................................................................37
8.1
Conceptual site model ......................................................................................................................... 37
8.2
Contaminants of concern .................................................................................................................... 37
8.3
Exposure pathways and receptors ...................................................................................................... 37
8.4
Sampling .............................................................................................................................................. 38
8.5
Exposure concentrations ..................................................................................................................... 39
8.6
Soil reference values ........................................................................................................................... 40
8.7
Applicable LUC SRVs ............................................................................................................................ 41
8.8
Risk characterization ........................................................................................................................... 41
8.9
Uncertainty .......................................................................................................................................... 46
8.10 Conclusion ........................................................................................................................................... 47
9.0
References .........................................................................................................................48
Tables ..............................................................................................................................................49 Appendix A – Calculating 95 UCL of the mean ...................................................................................64 Appendix B – Calculating TCDD and B[a]P equivalents.......................................................................70
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Acronyms 95 UCL
95% upper confidence level of the mean
AA
atomic absoption
B[a]P
Benzo[a]pyrene
bgs
below ground surface
BTEX
Benzene, Toluene, Ethylbenzene, Xylene
BTV
Background Threshold Value
CERCLA
Comprehensive Environmental Response, Compensation and Liability Act
Com/Ind
Commercial/Industrial
COC
contaminant of concern
COPC
contaminant of potential concern
cPAH
Carcinogenic Polycyclic Aromatic Hydrocarbon
Csat
soil saturation limit
CSM
conceptual site model
DNAPL
dense non-aqueous phase liquid
DPP
direct push platform
DRO
diesel range organics
DU
decision unit
ECD
electron capture detector
ELCD
electrolytic conductivity detector
ELCR
excess lifetime cancer risk
EPA
U.S. Environmental Protection Agency
ESA
Environmental Site Assessment
ETV
equivalent threshold value
FID
Flame Ionization Detector
FOCS
fiber optic chemical sensor
FSP
Field Sampling Plan
GC
gas chromatography
GC/MS
gas chromatography/mass spectrometery
GIS
geographic information system
GOF
goodness of fit
GRO
gasoline range organics
H0
null hypothesis
H1
alternative hypothesis
HASP
Health and Safety Plan
HI
Hazard Index
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HQ
hazard quotient
ICP/MS
inductively coupled plasma mass spectrometery
IDW
investigation derived waste
IRS
infrared spectrophotometry
LIF
laser induced fluorescence
LNAPL
light non-aqueous phase liquid
LUC
Land Use Category
MAW
mean annual windspeed
MERLA
Minnesota Environmental Response and Liability Act
MDH
Minnesota Department of Health
MIP
membrane interface probe
MPCA
Minnesota Pollution Control Agency
OSHA
Occupational Safety and Health Administration
PA
Preliminary Assessment
PAH
polycyclic aromatic hydrocarbon
PCB
polychlorinated biphenyl
PCP
pentachlorophenol
PID
photoionization detector
PUG
Property Use Guidance
QAPP
Quality Assurance Project Plan
QA/QC
quality assurance/quality control
Q-Q
Quantile-Quantile
RCRA
Resource Conservation and Recovery Act
Res-Rec
Residential/Recreational
RFA
RCRA Facility Assessment
RFI
RCRA Facility Investigation
RI
Remedial Investigation
RSC
relative source contribution
SAP
Sampling and Analysis Plan
SAWS
surface acoustic wave sensors
SCAPS
Site Characterization and Analysis Penetrometer System
SI
Site Inspection or Site Investigation
SIG
Soil Investigation Guidance
SLV
soil leaching value
SRV
soil reference values
SVOC
semi-volatile organic compound
TCDD
2,3,7,8-tetrachlorodibenzo-p-dioxin
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TEF
Toxicity Equivalency Factors
TPH
total petroleum hydrocarbon
T-W
Tarone-Ware
UTL
upper tolerance limit
UV-Vis, UV/VIs
ultraviolet visible spectrophotometry
VIC
Voluntary Investigation and Cleanup
VOC
volatile organic compound
WMW
Wilcoxon-Mann-Whitney
XRF
X-ray fluorescence
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1.0 Introduction The Soil Investigation Guidance (SIG) provides guidance for investigating potential human health risks from soil contamination for the following Minnesota Pollution Control (MPCA) Remediation programs under the Minnesota Environmental Response and Liability Act (MERLA): · · ·
Superfund Voluntary Investigation and Cleanup (VIC) Resource Conservation and Recovery Act (RCRA)
It provides guidance regarding: · · · · · · · · · ·
Soil contaminants Soil exposure pathways Potential human receptors Field screening Soil sampling Risk characterization Soil reference values (SRVs) Risk management options Site specific background Site specific risk assessments
It is intended to provide useful information that can be used to conduct a human health soil investigation which is only part of the site investigation. This document does not provide guidance for investigating other types of media or for evaluating risks to ecological receptors, which are often included in a site investigation. Guidance for evaluating human health risks associated with other types of media (groundwater, surface water, soil vapor, sediment) and the evaluation of risks to ecological receptors may be found on MPCA’s website. In addition to the Soil Investigation Guidance, each MPCA Remediation program (Superfund, VIC, RCRA) may have program specific requirements. Soil leaching values (SLVs) evaluate potential risks to groundwater from contaminants present in soil. SLVs are used when evaluating the groundwater exposure pathway. This guidance does not include discussion regarding SLVs. Guidance regarding this evaluation is available on MPCA’s website (MPCA 2013). A site investigation may include some or all of the following: · · · ·
Information investigation Initial soil investigation Remedial soil investigation Site specific risk assessment
Agricultural soil investigations are not included in this guidance since they are conducted by the Minnesota Department of Agriculture.
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2.0 Soil investigation This section is intended to provide a general overview of the soil investigation. It is not intended to contain all of the items necessary to complete a specific program’s site investigation. Soil investigation is required at any site where a release or potential release of hazardous substances to the environment has been identified. Hazardous substances include but are not limited to those within the scope of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). It is intended to determine the extent and magnitude of contaminated soil and evaluate the associated human health and ecological risks. This guidance only covers evaluation of human health risks associated with contaminated soil. MPCA Remediation programs (VIC, Superfund, RCRA) conduct soil investigations with a specific interest in mind. For example, phased Environmental Site Assessments (ESAs) are generally conducted to obtain innocent landowner liability protection and define exposure risks for a property prior to development, Preliminary Assessments (PAs) are conducted to identify sites with significant releases that need to be addressed by state or federal remediation programs to support listing on the National Priorities List (NPL) and RCRA Facility Assessments are conducted to gather information on releases at RCRA facilities. Regardless of the MPCA program involved, soil investigations are generally accomplished using some or all of the following three investigations: · · ·
Information investigation Initial soil investigation Remedial soil investigation
In some cases a site specific risk assessment may also be accomplished (please refer to Section 8.0). The table below displays the different soil investigation approaches MPCA programs use. MPCA program soil investigation approaches Soil investigation phases
VIC/Brownfields
RCRA
Superfund
Information investigation
Phase I ESA
Preliminary review and visual site inspection components of RCRA Facility Assessment (RFA)
Preliminary assessment (PA)
Initial soil investigation
Phase II ESA, and/or limited site investigation
Sampling visit component of RFA
Site inspection or site investigation (SI)
Remedial soil investigation
Phase II ESA, site investigation
RCRA facility investigation (RFI)
Remedial investigation (RI)
Additional information regarding program investigation approaches is available in the following guidance: ·
ASTM 2013. ATSM E1527-13, Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process
·
ASTM 2008. ATSM E2247-08, Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process for Forestland or Rural Property
·
ASTM 2011. ATSM E1903-11, Standard Practice for Environmental Site Assessments: Phase II Environmental Site Assessment Process
·
40 CFR Part 312 All Appropriate Inquiry
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·
40 CFR Part 300, Appendix A, “Hazard Ranking System; Final Rule”
·
EPA 1991. 9345.0-01A, EPA Guidance for Performing Preliminary Assessments Under CERCLA
·
EPA 1992. 9345.1-05, EPA Guidance for Performing Site Inspections Under CERCLA
·
EPA 1986. PB87-107769, RCRA Facility Assessment Guidance
·
EPA 1989. 9502.00-6D, Interim Final RCRA Facility Investigation (RFI) Guidance
·
EPA 1988. 9355.3-01, EPA Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA, Interim Final
2.1 Information investigation The information investigation determines if a site might pose a potential threat to human health and the environment. It should accomplish the following: ·
·
· ·
Obtain desktop information for review (ex: maps, geologic information, aerial photographs, city directory listings, fire insurance maps, topographic maps, geographic information systems (GIS) information, chain of title documents, plat maps, etc.) Review regulatory listings and conduct file searches (ex: regulatory files available with EPA and/or MPCA, records and permits on file with local government units, information from public health agencies, files and plans available on-site/in-house, etc.) Conduct interviews with current/former property owners and/or building occupants Complete a site visit to observe conditions at the property
Typically, this information is collected to determine if soil testing is necessary.
2.1.1 Report An information investigation report should discuss the following items: · · · · · · · · ·
Historical and current chemical storage, use management and waste generation and disposal practices Any existing site data Geologic/hydrogeologic information Land uses/operations and whether they have created or have the potential to create a release Known hazardous substance releases and potential sources of hazardous substances Important migration pathways and affected media Likelihood of a release to occur or have occurred Comprehensive survey of receptors Critical sample locations where soil sampling is warranted based on current and historical site information
Even though soil sampling may occur during a combined background and initial soil investigation (such as in a combined PA/SI, a RCRA Facility Assessment, or a combined Phase I/Phase II ESA), soil sampling is not part of the information investigation.
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2.1.2 Conclusion There are two potential conclusions from the information investigation: · ·
If sufficient information is collected to indicate no release has occurred or is likely to occur, no additional soil investigation is necessary. If the potential for soil contamination to be present has been identified, an initial soil investigation should be conducted.
2.2 Initial soil investigation The initial soil investigation determines whether or not soil contamination is present at a site. It is typically the first investigation where soil samples are collected to determine whether or not contaminants have been released to the environment and whether they have a potential to cause harm to human health or the environment. It is not intended to define the full extent and magnitude of contamination since this is accomplished during the Remedial Investigation. It should accomplish the following: · · · ·
Review available information (including analytical data) Develop site-specific plans (work plans, sample plans, health and safety plans, investigationderived waste [IDW] plans, etc.) Perform field work to collect samples Evaluate results and prepare report
2.2.1 Soil sampling Site history and available information obtained during the information investigation should be used to develop a soil sampling scope of work. Soil sampling may be conducted to accomplish the following: · · · ·
Support a determination that no additional assessment is needed Confirm whether or not a release has occurred Identify specific contaminants of concern Determine nature of the release
2.2.2 Sampling work plan Once the need for soil sampling has been identified, it is important to clearly specify the data that is required as well as the rationale behind it. Choosing the appropriate sampling and analysis methods is important to ensure a meaningful release determination can be made. Sampling and work plans should be developed to collect data at locations of concern (example: above or around a surface impoundment, near an area of soil staining, in chemical storage or operational areas). They should be clear, concise and easy to understand. All sampling plans should include: · · · · · ·
Investigation goals and scope Sequence of field activities Sampling design and rationale Sampling locations, depths and rationale Sampling methods and operating procedures Analytical methods and requirements
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· · · · · · ·
Sample handling Quality assurance/Quality control Equipment decontamination Investigation derived waste management and disposal Chain of custody procedures Contingency plans in case unexpected contamination is encountered Reference to site health and safety plan
2.2.3 Potential contaminants Soil samples should be analyzed for any potential contaminants identified during the information investigation. Positive field screening results can also be used as a preliminary indicator of contaminants to include for analysis (please refer to Section 3.0). Many sites have insufficient data or no data regarding potential contaminants that have been historically generated. When insufficient information is available, a responsible or non-responsible party can use the land uses identified during the background investigation to identify potential contaminants. A list of some common site uses with contaminants typically found at these sites is included in Table 1. Note that the table is not intended to be all inclusive, and it may not be relevant for every site.
2.2.4 Report An initial soil investigation report should generally provide the following: · · · · · ·
Narrative of the site (history, hydrogeological conditions, known hazardous substances, pathways of concern, etc.) Sampling objectives Sampling plan scope of work Results of sampling and quality assurance of data Conclusions and recommendations for additional action at areas of concern Attachments (maps/figures denoting sampling locations, tables with analytical data and qualifiers, logbook/field notes, photos, analytical reports, geologic boring logs, standard operating procedures)
2.2.5 Conclusion The final task in the initial soil investigation is to evaluate sample results and make final recommendations concerning the need for further soil investigation. There are two potential conclusions from the initial soil investigation: ·
·
If sampling and site information provides sufficient evidence that no release has occurred, or if the contaminated soil does not pose a potential risk to human health or the environment, no additional soil investigation is necessary. If the potential for soil contamination is present and a risk to human health or the environment has been identified, a remedial soil investigation is required.
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2.3 Remedial soil investigation The remedial soil investigation defines the full extent and magnitude of contamination. It determines where contamination is present and what areas need to be remediated. Soil samples may be collected to determine whether or not contaminants have been released to the environment and whether they have a potential to cause harm to human health or the environment. It should accomplish the following: · · · · ·
Characterize nature, extent and magnitude of soil contamination Determine if the soil contamination presents a potential risk to human health and the environment Identify source(s) of soil contamination, including ongoing sources, that need to be addressed so a sustainable remedy can be developed and implemented Determine whether response actions are needed Determine physical and chemical characteristics of site that will influence development, evaluation and selection of remedial cleanup options
The following sections comprise a general overview of the process. For more detailed information please refer to the following guidance: · ·
EPA 2016a. EPA Website Regarding Superfund Remedial Investigation/Feasibility Study (Site Characterization) EPA RFI. EPA Guidance Regarding RCRA Facility Investigation (RFI) (equivalent of an RI in Superfund)
2.3.1 Scope of work The Remedial Investigation scope of work is developed based on data and information from the information and initial soil investigation and should be submitted for MPCA review and approval. The MPCA’s Property Use Guidance (PUG) document should also be consulted since it provides guidance on incorporating current, planned and future land use into project decisions (MPCA 2016a). Initial scoping activities include: · · · ·
Conduct site planning meeting (optional) Evaluate existing data Develop conceptual site model (CSM) Identify initial data needs and data quality objectives
After completing the initial scoping activities, project plans are developed. The primary project plans for the scope of work may include: · ·
· ·
Work Plan Sampling and Analysis Plan (SAP) · Quality Assurance Project Plan (QAPP) · Field Sampling Plan (FSP) Health and Safety Plan (HASP) Community Relations Plan
Information regarding field screening and soil sampling are included in Sections 3.0 and 4.0.
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2.3.2 Site soil characterization During site characterization field data are collected and analyzed in accordance with the project plans to evaluate the potential risk to human health and the environment. The major site soil characterization activities include: · · · ·
Collection of soil samples Analysis of soil samples at an MDH certified fixed base laboratory Evaluation of laboratory analytical results, quality assurance results and field observations Determine whether extent and magnitude has been adequately defined
Soil sampling should characterize the extent and magnitude of soil contamination in both the vertical and horizontal directions for all release areas at the site. If the extent and magnitude of soil contamination are not characterized within the first round of sampling, additional rounds of site characterization are required, which may require updating the primary project plans. To characterize soil contamination and evaluate human health risk, soil concentrations are compared to soil reference values (SRVs) (please refer to Section 5.0). Site characterization activities should provide the following: · · · · ·
·
Contamination present Vertical and horizontal extent of contamination Spatial patterns (example: hot spots) Identification of source area(s) Potential receptors and exposure pathways based on · Current and future land use · Contaminant extent and depth · Contaminant properties and migration pathways · Site geology and hydrogeology Exposure areas (location of potential contact between a human or environmental receptor and contaminants) · Exposure point concentration for each exposure area
2.3.3 Report A remedial soil investigation report should provide the following: · ·
·
Site history and background including previous investigation work Physical characteristics of the study area · Surface features · Geology · Soils · Demography and land use Results of the site characterization · Known and potential release sources and source areas · Migration pathways · Contaminants of potential concern · Fate and transport mechanisms
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Vertical and horizontal extent of soil contamination · Deviations from the SAP · Quality control/quality assurance of analytical data and sampling methods Human health risk evaluation · Exposure pathways · Toxicity (using SRVs and/or background threshold values) · Risk characterization · Environmental evaluation (outside the scope of this guidance) Summary and conclusions · Nature and extent of contamination · Fate and transport · Risk evaluation Data limitations and recommendations for future work Recommended remedial action objectives SRV spreadsheet comparing soil concentrations to SRVs Site figures illustrating · Site location · Sampling locations · Cross sections Field documentation Laboratory analytical reports including quality assurance data Outcomes and risk determination ·
·
·
· · · ·
· · ·
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3.0 Field screening Field screening is useful when segregating excavated soils, identifying releases and estimating the extent of contamination. It can be used to evaluate soil conditions in real time (such as whether or not soil needs to be excavated), but it is not intended to replace sampling and laboratory analysis. It should NOT be the sole source of data to compare to risk based values that drive a mitigation decision. Methods provided in this section include some, but not all of the available field screening methods. There may be several sources of equipment, methods or test kits available which may be important when selecting the appropriate soil screening technology for your site. New and/or improved methods that are available when the site is being evaluated should also be considered. These methods can be used as a means to identify locations that should be sampled during an initial soil investigation since positive verification of contamination being present at specific levels of concern is a priority. Field screening methods are extensively used during the remedial soil investigation to define the extent of a release. Field screening methods have limitations concerning the applicable ranges of concentrations they can detect. The user should identify project specific data quality objectives and identify the method(s) that can obtain those objectives. Advantages and limitations of the methods described below (generally due to their mobility, low cost, and wide range of contaminant analysis) are included in Table 2. The additional guidance listed below may also be helpful · · · · ·
EPA 2007. SW846, EPA Test Methods for Evaluating Solid Waste, Physical/Chemical Methods ASTM 1992. STP1158, Field Screening Procedures Applied to Soils for use in Risk Assessments EPA 2015. ClU-IN Website with Characterization and Monitoring Guidance MPCA 2008. Soil Sample Collection and Analysis Procedures Specific manufacturer’s guidance
3.1 Physical screening methods Physical screening methods include visual (i.e. staining) and olfactory (i.e. odors) observation. The methods are qualitative and only provide basic information related to the presence or absence of contamination. As a result, these methods should be used in conjunction with additional screening methods (i.e. physical screening with a PID, immunoassay, etc.).
3.2 Photoionization detectors Photoionization detectors (PID) are commonly used to detect organic vapors (some non-chlorinated volatile organic compounds (VOCs) such as solvents, fuels, degreaser, plastics, and lubricants) and some inorganic gases (such as phosphane, hydrogen sulfide, or ammonia). PIDs do NOT work well for all chlorinated VOCs, especially those present at low levels. Samples are placed in a sealed container and bombarded with high energy photons emitted from an energy source (lamp). The two most common lamps used are 10.6 electron volts (eV) and 11.7 eV. The 11.7 eV lamp measures the broadest range of compounds while the 10.6 eV lamp is more selective. Because the 11.7 eV lamp is manufactured in a way to measure the broadest range of compounds, it typically is more expensive, and has a shorter lifespan than the 10.6 eV lamp.
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Contaminants present in the sample with ionization potentials below the photon energy are ionized and attracted to an electrode. A signal is generated and measured indicating the presence of the contaminant. The results are qualitative to semi-quantitative and are limited to compounds that readily volatilize.
3.3 Flame Ionization Detectors Flame Ionization Detectors (FID) are commonly used to detect organic vapor (most commonly VOCs such as solvents, fuels, degreasers, and methane). FIDs operate in a similar fashion as a PID; however, samples are placed in a sealed container and burned in a hydrogen-air flame. Ions generated are attracted towards a collector. Specific contaminants are detected by the quantity of ions contacting the collector. FIDs can be used to detect organics.
3.4 Portable gas chromatography detectors Gas chromatography (GC) is an analytical technique used to separate and analyze environmental matrices for contaminants. This technique includes injection of a sample, separation using a carrier gas and detection of a contaminant. When used with various types of detectors, it can be used to measure halogenated and non-halogenated VOCs, semi-volatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pentachlorophenol (PCP), total petroleum hydrocarbons (TPH), pesticides, and dioxins. Each portable GC detector takes advantage of a unique molecular characteristic to generate a measureable electrical signal. Some portable GC detectors can be combined with mass spectrometers into a portable GC/MS unit which may be capable of providing similar analyses as fixed laboratory instruments. Some SW-846 methods that can be adapted for field use include SVOCs, VOCs, PAH, and PCBs.
3.5 Electron capture detector An electron capture detector (ECD) consists of a sealed stainless steel cylinder containing radioactive nickel-63 and a carrier gas (ECD cell). Nickel 63 emits electrons that collide with the carrier gas molecules, ionizing them. This produces a stable cloud of free electrons in the ECD cell (current). When an electronegative molecule (ex: halogenated molecule) enters the ECD cell, it immediately combines with one of the free electrons, temporarily reducing the number of free electrons (or reducing the current in the ECD cell). The detector measures the remaining electrons (loss of current) in the ECD cell. ECD can be used to detect chlorinated pesticides, halogenated solvents, and PCBs.
3.6 Electrolytic conductivity detector An electrolytic conductivity detector (ELCD or Hall detector) is a halogen-specific detector which works using electrolytic conductivity principles. Samples are reacted with a gas in a tube then mixed with a solvent to result in a specific product based on what contaminant is present in the sample. The product is passed through a conductivity cell where a signal is generated that is specific to the contaminant present. Both the temperature of the tube and the solvent used determines what type of contaminants can be detected. ELCD can be used to detect chlorinated pesticides, halogenated solvents, and PCBs.
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3.7 Surface acoustic wave sensors Surface acoustic wave sensors (SAWS) are chemical sensors based on piezoelectric effect. They consist of an input transducer (piezoelectric crystal), polymer film and an output transducer. Contaminants adsorb to the polymer film resulting in an increase in the mass of the polymer. This increase causes a change in the phase of the acoustic signal which is translated into an electrical signal at the output transducer and measured as a detection for a specific contaminant. SAWS can be used to detect VOCs, SVOCs, PCBs and nitroaromatic explosives.
3.8 Spectrophotometry Spectrophotometry encompasses a number of techniques involving measurement of the absorption spectra of narrow band widths of radiation. A simple spectrophotometer consists of a radiation source, a monochromator (used to disperse light), and a detector used to measure the amount of light.
3.8.1 Infrared spectrophotometry Infrared spectrophotometry (IRS) is typically used to measure the carbon-hydrogen bonds (C-H bonds) present in all petroleum hydrocarbon mixtures through use of their infrared absorption spectra. Infrared spectrometry can be used to detect gasoline, diesel fuel, and heavier fuels or oils.
3.8.2 Ultraviolet visible spectrophotometry Ultraviolet visible spectrophotometry (UV-Vis or UV/Vis) refers to absorption spectroscopy in the ultraviolet-visible spectral region. The absorption (or reflection) in the visible range directly affects the perceived color of the chemical involved and measures the electron transition from a lower to higher energy state when excited by UV radiation. Ultraviolet visible spectrophotometry can be used to detect transition metal ions, highly conjugated organic compounds, and biological macromolecules.
3.8.3 Ultraviolet fluorescence Ultraviolet fluorescence is complementary to UV-Vis, in that it measures the electron transition from a higher to lower energy state when excited by UV radiation. The technique is used in a number of field screening applications including: semi-quantitative analysis of solvent extracted PAHs, in conjunction with fiber optic sensors, and as a surface contamination detector (a non-fluorescing substance sprayed on the ground surface reacts chemically with the contaminant of interest to form a substance that fluoresces with UV excitation). Ultraviolet fluorescence can be used to detect THP, PCBs and PAHs.
3.8.4 Fiber optic chemical sensors/Laser induced fluorescence Fiber optic chemical sensors (FOCS) operate by transporting light by wavelength or intensity to provide information about analytes in the environment surrounding the sensor. FOCS can be categorized as extrinsic (using an optical fiber to transport light) or intrinsic (the fiber is used directly as the detector). Intrinsic FOCS can be used to detect volatile petroleum constituents (ex: BTEX – Benzene, Toluene, Ethylbenzene, Xylene) and chlorinated VOCs. Extrinsic FOCS can be used to detect fluorescing hydrocarbons including TPH and PAHs. Laser induced fluorescence (LIF) is an example of an extrinsic FOC used for real-time, in-situ field screening of hydrocarbons. The technology is intended to provide highly detailed, qualitative to semiquantitative information.
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3.8.5 X-ray fluorescence X-ray fluorescence (XRF) is a non-destructive analytical technique used to determine the metals composition of environmental samples. The sample is bombarded with high energy x-rays causing the emission of secondary fluorescent x-rays from the sample based on the contaminants present. X-ray fluorescence can be used to detect heavy metals such as mercury, chromium, lead, cadmium, copper, nickel, and arsenic in both in situ and ex situ soils.
3.8.6 Mercury vapor analyzers This technology is a specific tool used to measure mercury vapors emitted from soil. A number of technologies exist to detect mercury including the use of gold film sensors, atomic fluorescence spectroscopy, and atomic absorption spectroscopy. Gold film sensors rely on gold’s high affinity for mercury, and measures the change in electrical resistance from mercury accumulated on the film. In atomic absorption spectroscopy, a light source of known intensity and wavelength is radiated through an air sample and the light ultimately encounters a detector. When mercury is present, electrons in the mercury atoms will take up some part of this energy from the light source. The variation between the energy determined by the detector and the initial energy of the light source provides an indirect measurement of the number of mercury atoms present. Atomic fluorescence spectroscopy works similarly to fluorescence described above. It measures the amount of energy as the excited electron comes back to its ground state.
3.9 Test kits/Immunoassays Test kits are self-contained analytical tests that generally use a chemical reaction that produce a color to identify contaminants. Test kits are generally a type of immunoassay, which is a technique for detecting and measuring a target compound through the use of an antibody or antigen that binds only to that substance. Quantitation is performed by monitoring color change, either visually or with a spectrophotometer. The method generates semi-quantitative and quantitative results.
3.9.1 Colorimetric test kits Colorimetric test kits use a wet chemistry non-immunoassay test to detect single contaminants in soil. The intensity of the color formation determined by visual comparison or with spectrophotometric equipment indicates whether the contaminant is present or not. These methods result in semiquantitative or quantitative results. Test kits can be used to detect petroleum hydrocarbons, TPH halogenated VOCs, PCBs, PAHs, organic pesticides, PCP, dioxin, and mercury.
3.9.2 Shake tests Shake tests are a qualitative sampling test used to identify the presence of hydrocarbons including light non-aqueous phase liquid (LNAPL) and dense non-aqueous phase liquid (DNAPL) in soil. The kit typically includes a bottle and dye, to which soil is added. After vigorously shaking the bottle, the dye is released and the solution changes color if the contaminant is present. In some cases, the resulting color may be used to provide a semi-quantitative analysis.
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3.10 Direct push platform Direct push platform (DPP) units use hydraulic pressure to advance sampling devices and geotechnical and analytical sensors into the subsurface. DPPs use one of two sampling modes: a specific tool string that performs downhole measurements or gathers sample at a specific depth (no soil is removed), or a dual tube arrangement used to take continuous soil samples for evaluation at the surface.
3.10.1 Cone penetrometer mounted sensor Cone penetrometer mounted sensors offer real-time, in situ, field screening methods for field screening and site characterization. Cone penetrometer mounted sensors can detect VOCs, SVOCs, TPH, PAHs and non-aqueous phase liquids (LNAPL, DNAPL). One notable example is the Site Characterization and Analysis Penetrometer System (SCAPS). It consists of a truck mounted cone penetrometer that pushes an instrumented probe into the subsurface. Different sensors can be attached to the probe such as LIF to detect TPH and PAHs or XRF to detect metals.
3.10.2 Membrane interface probe Membrane interface probe (MIP) is a semi-quantitative, field screening device used in connection with a DPP. The device is advanced to the depth of interest to collect samples of vaporized compounds in soil. The probe captures vapor sample and a carrier gas transports the sample to the surface for analysis. MIP can be used to detect VOCs and SVOCs.
3.11 Mobile lab Mobile laboratories offer a self-contained laboratory capable of mobilizing to a site, and come equipped with a wide range of instrumentation including: gas chromatography and mass spectrometry (GC/MS), inductively coupled plasma mass spectrometry (ICP/MS), atomic absorption (AA) spectroscopy, and XRF. Mobile labs can detect a wide range of contaminants such as VOCs, SVOCs, pesticides, PCBs, metals, and TPH. While mobile labs are able to offer real-time sampling, use of a mobile laboratory is not approved for all situations and must be pre-approved by MPCA staff prior to use.
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4.0 Soil sampling This section provides guidance on common sample collection methods and general investigation approaches for evaluating human exposure to soil contamination. This guidance does not provide a detailed step by step description of how to collect soil samples and how to perform a comprehensive soil investigation. It is intended to be used with flexibility by competent environmental professionals for evaluating human health risk.
4.1 Sample collection tools Table 3 includes some widely used, but not an all-inclusive list of available sampling tools that can be used to collect soil samples for field screening, field analytical and laboratory analytical purposes. The choice of the most appropriate way to conduct soil sampling is based on many factors, including the types of contaminants, how the release occurred, accessibility and the type of data required.
4.2 Sampling methods 4.2.1 Surface soil sampling Surface soil samples, generally collected between zero to four feet below ground surface (bgs), can usually be collected using hand tools (example: hand augers, hand scoop, shovel) without the use of mechanical drilling, coring or excavating equipment. Below is a list of best practices to consider when collecting surface soil samples. Additional measures necessary to follow when sampling for VOCs are included in Section 3.2.3. · · ·
· · ·
· ·
Determine and document sample locations (UTMS, NAD83) and depths in accordance with sampling plan. Always provide a description of soil appearance and physical properties. The type of sample container used and amount of sample material to be collected for each type of analysis should be determined by the laboratory prior to sampling. Sample containers supplied by the laboratory are recommended to ensure the use of appropriate containers with adequate volumes that are clean and pre-weighed if necessary. Prior to collecting sample, carefully remove the top layer of vegetation or debris to expose the top layer of bare soil or target sample layer using a dedicated or pre-cleaned tool. Clean latex or nitrile gloves should be used by all personnel handling samples and sampling tools and sample containers during the collection and process. Stainless steel tools are generally the most appropriate to use for extracting surface or near surface samples. Tools should be made from materials that will not cause cross contamination that may interfere with the analysis of target contaminants. For example, tools plated with chrome, brass, or nickel should not be used if sampling for RCRA metals and certain types of plastics should be avoided when sampling for organic compounds. Use dedicated sampling equipment and tools for homogenizing and splitting samples to prevent cross contamination. Dedicated equipment for each sample is preferred. If this is not practical, sampling equipment must be thoroughly cleaned and decontaminated with an appropriate detergent and rinsed with distilled or deionized water between each sample.
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·
·
·
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Screen out debris and large fragments. A #10 sieve may be used to remove fragments larger than two millimeters. Samples that will be analyzed for VOCs should be placed directly in the sample container immediately after being collected and should not be screened or disturbed in anyway. In most cases, samples for non-VOC analytes should be homogenized by thoroughly mixing prior to splitting into laboratory-supplied sample containers per individual sample. This does NOT apply to samples that will be tested for VOC contaminants. Samples that will be analyzed for VOCs should be placed directly in the sample container immediately after being collected and should not be screened or disturbed in any way. Sample heterogeneity is frequently an issue that results in variability of sample results. This can often be reduced by collecting larger volumes of sample and thoroughly homogenizing and screening out larger particle before splitting into sample containers. Chemical preservation of soil samples analyzed for non VOC contaminants is not generally recommended; however, most samples should be cooled on ice or refrigerated and protected from sunlight to minimize the potential for reactions. In accordance with EPA RCRA and Hazardous Waste Test (SW-846) sampling methods, most types of soil samples must be preserved by storing samples at a cool stable temperature of less than or equal to six degrees Celsius until they are analyzed.
4.2.2 Sub-surface soil sampling Many of the same practices listed in the section above also apply to collecting subsurface samples obtained using mechanical drilling or excavating equipment. Sub-surface soil samples, generally collected greater than four feet bgs, usually require the use of mechanical drilling, coring, or excavating equipment. Below are some items to consider when collecting sub-surface soil samples. · ·
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Subsurface samples are often targeted to depths or sub-surface layers with a specific soil type or with field evidence of contamination. Soil cores are often obtained from the sub-surface by driving split spoon sampling tools or thinwall sampling sleeves into the target sampling layer. Mechanical excavating can also be used to acquire subsurface samples. Samples for VOC analysis should always be collected from the target interval of the sample core first before performing field screen tests and collecting samples intended for non-VOC laboratory analysis. The specific sample sent to the laboratory for VOC analysis is often chosen based on field screening results. After performing appropriate field screening tests, the remaining target layer should be homogenized by thoroughly mixing in a decontaminated or dedicated bowl to ensure a representative sample is obtained before splitting into additional sample containers. It may be difficult to obtain an adequate volume of soil for all required physical tests and laboratory analyses when using drilling and coring methods. This should be anticipated before sampling and addressed in the sampling work plan. For example, the work plan may be written to include multiple cores from borings near the same location or prioritizing tests to be performed when a limited volume is recovered. Using a mechanical excavator to obtain subsurface samples allows for the recovery of large volumes of material for observation and sampling. Entering a trench or excavation to observe sub-surface soil layers or to collect samples is unsafe and is not allowed by OSHA safety regulations. Because of safety concerns, all samples collected from excavation must be obtained from material removed from the excavation.
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After soil is excavated from the appropriate layer, the surface of removed soil should be scrapped away with a dedicated or decontaminated tool to provide a fresh surface from which to collect the samples.
4.2.3 Sampling VOCs Significant loss of VOC contaminants can occur through volatilization resulting in a loss of VOCs into the air or headspace of the sampling container during collection and storage. Soil samples for analysis of VOCs should be collected in accordance with an appropriate EPA Method as identified in the site specific sampling plan. Coordination with the laboratory is necessary to ensure the use of proper containers, preservatives, storage and analyses. Composite sampling should NOT be used for VOCs since the required mixing step may lead to potential VOC losses. Separate samples should be collected for headspace screening, physical description of soil characteristics, laboratory testing of physical properties and laboratory testing for chemical parameters.
4.3 Sampling design This section provides information on some of the most commonly used sampling design approaches and general information on what types of situations or sampling objectives may be appropriate for each approach. Since site conditions and sampling objectives can vary widely, a good sample design should be tailored to meet site-specific objectives. For example, targeting samples to a specific location based on site information may be best for determining if a release has occurred, while randomly located samples may be the best design for estimating the average contaminant concentration in a defined exposure area. A sampling design should always begin with describing the investigation objectives and an explanation of the plan for meeting the objectives. In general, a sampling design should also include: · · · ·
Number and type of samples Sample locations Sample depths Rationale for choice of locations and depths
Appropriately designed sampling accomplishes the following: · · · · · · · · · ·
Determines presence or absence of contamination Identifies contaminants present Provides a range of contaminants concentrations Provides physical and chemical nature of contaminants Delineates both lateral and vertical extent of contamination Identifies hot spots Provides background concentrations when necessary Adequately represents site conditions Establishes site geological or hydrogeological conditions Provides defensible evidence
Commonly used sampling designs are listed below. Please refer to EPA’s Guidance on Choosing a Sampling Design for Environmental Data Collection for additional guidance (EPA 2002).
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4.3.1 Target sampling Target sampling is often used during an initial investigation when small potential areas of concern and site features are targeted for sampling to identify whether a contaminant release has occurred. It is used for sites where the history is known and confirmation of the extent and magnitude is needed. Target sampling involves locating samples based on site history and available information. Data obtained by this method is NOT appropriate to use in statistical calculations or to define contamination spatially. The following types of site specific information are commonly considered when using this sampling design to determine appropriate sample locations: · · · · · · · ·
Potential contaminant sources Known or potential patterns of chemical storage, use, management and disposal Characteristics of potential contaminants of concern, including mobility, persistence, degradation products Expected depth of fill, groundwater and bedrock and soil types Underground structures (utility lines, buried stormwater control structures, underground storage tanks) Redevelopment plans, including planned locations and depths of excavations Type and location of potential current and future receptors Property boundaries for redevelopment sites
Target sampling is referred to as judgmental sampling in EPA’s guidance.
4.3.2 Probabilistic sampling Probabilistic sampling designs apply sampling theory and random or systematic selection of sample locations instead of site history and available information. It is generally appropriate to use statistical methods to analyze this type of sample data. The most commonly used probabilistic sampling designs are discussed below.
4.3.2.1 Simple random sampling A simple random sampling design involves randomly located samples within an investigation area. This type of design uses a random process for selecting sample locations that gives all locations of the investigation area an equal chance of being sampled. This type of design is often used when estimating average concentrations within a defined exposure area. Some things to consider about this type of sampling design are: · · ·
· · · ·
Easy to understand and determine sample locations. Most appropriate when no contaminant spatial patterns or hot spots are expected in the investigation area. May be used for calculating sample data set statistics for investigation area; provides unbiased estimates of mean concentrations, variance, and other statistical parameters within a defined area. Can be used when calculating the minimum sampling size needed to achieve a level of statistical confidence for an investigation area. Accessing all randomly selected locations may be difficult at some sites. Likely will not provide even spatial coverage of an area when sample sizes are small. Does not take into account site information regarding areas or features being investigated.
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May not provide adequate information for revealing spatial patterns or applying spatial statistics.
4.3.2.2 Systematic/Grid sampling Systematic/grid sampling involves sampling at regularly spaced intervals across an investigation area with sample locations arrayed in one, two or three dimensions. Although the density of sample locations can vary, it is generally intended to provide even spatial coverage across a sampling area. It is often used because it can provide better spatial coverage of an area with a smaller number of samples than if samples were randomly located. This type of sampling design is most appropriate to use in the circumstance listed below: · · · · · ·
During an initial soil investigation Little information available regarding location of contaminant targets in a larger area Identify multiple separate areas of contamination over a larger area Identify hot spots Define extent of known impacted areas Identify spatial patterns of contamination
4.3.2.3 Stratified sampling Using some form of a stratified sampling design is common for investigations of larger sites with multiple areas of concern. Stratified sampling separates a site into separate investigation areas (strata) that are thought to have different soil characteristics. Each stratum is sampled and evaluated independently using an appropriate design and methods for the area. Stratification may be especially useful when different sampling procedures and/or designs are needed for different portions of a project area, possibly based on conditions such changing soil types, land use, surface cover or sampling depths. More reliable estimates of contaminant types and concentrations within each separate stratum may be achieved with this method.
4.3.2.4 Composite sampling Composite sampling involves combining and mixing soil from multiple locations to form a single homogeneous sample for a single set of analyses. This can be a cost effective way to incorporate information from multiple locations. Compositing is often used along with other types of sampling designs when the objective is to estimate contaminant concentrations of an area or volume of soil and information on spatial variability is not needed. Sampling can be designed to retain individual subsamples that can be analyzed separately at a later time if necessary. Several concepts to consider for composite sampling are: · · · · · · ·
NOT appropriate to use to analyze for VOCs NOT appropriate to use when evaluating acute human health risks NOT appropriate to use to delineate hot spots Individual subsamples should be the same size and composed of the same type of material Results should represent an average concentration of the subsamples if mixing is thorough Variability among groups of composite samples should be less than the variability of all individual subsamples used to form the group of composites Retesting aliquots from individual subsamples is possible
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Composite sampling is most appropriate for the following situations: · · ·
Estimate overall mean concentration while information about individual samples or spatial variability within the sampling unit are not important Identify if the average concentration of a contaminant within an area exists above or below a specific threshold Project threshold concentration objectives are high compared to detection levels
Homogenizing both the subsamples and then the composite sample itself is important following the procedures for sample collection. This is important to ensure the composite sample represents a true average of the subsamples it is formed from and/or the split portions of the subsamples are consistent and can be resampled. Composite sampling should only be performed when individual subsamples can be homogenized without affecting sample integrity or resulting in safety issues. For example, composite sampling for VOC contaminants is not acceptable because volatile contaminants will likely be lost during sample mixing.
4.3.2.5 Incremental sampling Incremental sampling is intended to provide a reasonably unbiased estimate of the average contaminant concentration over an area. This method involves collection of multiple discrete soil samples (typically 30 to 100) within each decision unit (DU). The samples are combined, processed and subsampled according to a specific procedure. Please refer to ITRC’s Incremental Sampling Guidance for additional details (ITRC 2012).
4.3.3 Other sampling designs In some cases a modified version of one of the sampling designs described above or a combination of designs may be appropriate to use. Other types of innovative sampling designs, such as ranked set sampling and adaptive cluster sampling might also be considered when designing a sampling plan.
4.4 Sampling Design Considerations Sampling plans for large areas usually involve using a systematic grid or random sampling to ensure adequate spatial coverage. The number of lateral soil sampling locations will be determined by the surface area of the site and the level of desired confidence in detecting areas of contamination if present. General guidelines regarding the number of sampling locations for an area with no apparent discrete areas of soil contamination are listed in the table below. These general guidelines are intended to provide a starting point and can be modified if sufficient rationale is provided. Individual features or operational areas suspected to be associated with higher concentrations of contaminants such as discrete source areas or previously identified hot spots should not be included in area-wide sampling. These areas should be investigated as separate areas. Recommended Minimum Preliminary Soil Sampling Density Surface Area of Site
Number of Lateral Sample Locations
less than 2 acres
6 sample locations per 0.5 acre (12/acre)
2-5 acres
sample locations placed on 75’ centers (~ 8 /acre)
5-40 acres
sample locations placed on 100’ centers (~ 4 /acre)
40+ acres
sample locations placed on 130’ centers (~ 3 /acre)
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4.5 Quality assurance/Quality control Laboratory analyses should be conducted for all contaminants calculated on a total, dry weight basis. Appropriate quality assurances and quality control procedures and methods with detection limits below the SRVs and background threshold values (BTVs) should be used. Appropriate QA/QC procedures should be included in the approved site quality assurance plan. For general considerations when designing a sampling plan please refer to Minnesota Pollution Control Agency Quality Assurance Project Plan Guidance and MPCA’s Data Quality Objectives (MPCA 2016b). Additional information can be found in EPA’s SW-846 (EPA 2007).
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5.0 Using soil reference values Soil Reference Values (SRVs) are a screening tool used to evaluate potential human health risks from soil exposure. They are derived based on EPA Superfund methodology using exposure assumptions based on land use categories (LUC) depicting a specific soil land use scenario and set of receptors. For some chemicals, SRVs derived based on exposure parameters and toxicity values calculate to be below background soil concentrations. An evaluation was conducted to determine if specific SRVs were below soil background and if necessary establish appropriate background values (Background Threshold Values or BTVs) that could be used instead of the health based SRV. Additional detail regarding SRVs and BTVs, including descriptions of the LUCs, SRV methodology and exposure parameters and a list of chemical with BTVs may be found in the following MPCA guidance: · · · · ·
Soil Reference Value (SRV) Technical Support Document (MPCA 2016c) SRV spreadsheet (MPCA 2016d) SRV spreadsheet – Site specific (MPCA 2016e) Background Threshold Value (BTV) Evaluation (MPCA 2016f) Soil reference values (SRVs) evaluate chronic non-cancer and cancer risks as well as acute noncancer risks for a limited number of chemicals.
5.1 Exposure pathways and receptors All potential exposure pathways and receptors should be identified. For an exposure pathway to be complete, the following three conditions must exist: · · ·
Source of contamination Exposure route Potential receptor
Possible routes of human health exposure to contaminants in soil include: · · · · · · ·
Incidental soil ingestion Ingestion via produce Ingestion via food chain Dermal contact with soil Inhalation via fugitive dust Inhalation via volatilization – outdoor air Inhalation via volatilization – indoor air
Routes of exposure included in the derivation of SRVs are bolded. The inhalation via volatilization – indoor air route of exposure is evaluated during the vapor intrusion investigation. If any of the routes of exposure that are not bolded in the list apply to a site (except for the inhalation of volatilization – indoor air), it may be necessary to conduct a site specific risk assessment (please refer to Section 8.0 for additional information). Potential receptors on or off site that may be exposed to site soil contamination should be identified. It is also important to identify the most sensitive receptor that may be exposed. In some cases, if there is no completed current or future exposure pathway for a contaminant, it may not need to be investigated. Soil Investigation Guidance • September 2016
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5.2 Sampling Data obtained from sampling is used to estimate exposure concentrations to evaluate potential risks (please refer to Section 4.0). The default soil depth a receptor is likely to be exposed to will vary by LUC. Exposure concentrations to evaluate any potential risks from ingestion, dermal or inhalation via fugitive dust should be calculated from samples obtained from the surface to the depth a receptor is likely to have exposure to (Table 1 and Figures 1 through 6 in the Soil Reference Value (SRV) Technical Support Document). If a situation exists on site that does not meet the assumptions used to establish the applicable LUC depth of exposure, the exposure concentration is required to be obtained from the site specific depth the receptor is likely to have exposure to. When VOCs or SVOCs are present, exposure concentrations to evaluate potential outdoor inhalation risk from vapor should be calculated from subsurface samples obtained from an appropriate depth below the soil surface based on the specific contaminant present and site characteristics.
5.2.1 Data presentation Sampling data should be presented in a clear and concise manner in tables and include the following information and statistics (when possible) used in the soil investigations to characterize potential human health risks: · · · · · · · · · · ·
Sample date, identification and depth Results of each individual sample Detection limit Number of observations Frequency of detection Maximum Minimum Median Arithmetic mean and standard deviation 95% upper confidence level (95 UCL) of the mean (when possible) Identification of samples designated with J to reflect an estimated concentration
To determine the 95 UCL of the mean, EPA’s ProUCL software should be used. This software is available on EPA’s website (please refer to Appendix A for detailed instructions, EPA 2011). This calculation can only be accomplished on datasets consisting of eight or more samples. Maximum concentrations should be used for composite or incremental samples. It is not appropriate to report the items bolded in the list above for composite or incremental samples.
5.2.2 Non-detect data The Kaplan Meier method available in EPA’s ProUCL software is recommended to evaluate non-detect data, including 2,3,7,8-TCDD and Benzo[a]pyrene equivalents. Please refer to Appendix B for instructions of how to accomplish this using.
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5.3 Exposure concentrations An exposure concentration refers to the concentration of a chemical in soil that a receptor is expected to be exposed to at a contaminated site. There are two types of exposure concentrations used to reflect a receptors contact with contaminated soil: ·
·
Exposure point concentration · Used to evaluate acute exposures · Exposure points are defined by discrete samples with one exposure concentration · Samples used should be representative of the depth to which the potential receptor may be exposed Exposure area concentration · Used to evaluate chronic, subchronic and short-term exposures · Exposure areas § Consists of areas with similar contamination § Do NOT contain uncontaminated soil § Do NOT contain hot spots · Samples from an exposure area are averaged over the entire exposure area to define an exposure area concentration · Samples used should be representative of the area and depth to which the potential receptor may be exposed · Must be determined in a way that reasonably reflects a receptors potential exposure across the entire site
Due to the possible transport of contamination off site, exposure areas or points may be located on or off site. Information regarding the conceptual site model (CSM) gathered during the soil investigation regarding site use should be taken into consideration when determining appropriate exposure area and exposure point concentrations. Areas containing significantly higher concentrations of contamination than surrounding areas are referred to as hot spots. These areas may have been subject to larger releases or contaminated in different ways than other areas of the site. All hot spots should be defined as distinct exposure areas and evaluated separately. It is not appropriate to use composite or incremental sampling to evaluate acute risks.
5.4 Applicable LUC SRVs Information regarding the CSM gathered during the soil investigation should be used to determine the appropriate soil land use category (LUC) of SRVs applicable to the site. There are two sets of LUC SRVs: · ·
Residential/Recreational * Commercial/Industrial
* The Residential/Recreational LUC has three sub categories: Single Family Homes, Multi-Family Housing and Recreational. Residential/Recreational SRVs are used with all three sub categories.
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Land use categories (LUC) have been developed depicting specific scenarios and receptors. LUCs characterize two things: · ·
LUC specific exposure parameters used to derive LUC specific SRVs Accessible and potentially accessible zone depths that a human receptor is expected to access
LUCs are summarized in Table 1 and depicted in Figures 1 through 6 in the Soil Reference Value (SRV) Technical Support Document. There are also two clauses: Impervious Surface and Utility Corridor that apply to all of the LUCs which are explained in Section 2.0 of the Soil Reference Value (SRV) Technical Support Document. Further explanation regarding appropriate depths to use when conducting a response action including the use of institutional controls is provided in the Property Use Guidance. (MPCA 2016a)
5.5 Risk characterization Risk characterization determines if there is a possibility that human health risks may exist at a site. During the initial soil investigation and remedial soil investigation this is accomplished by comparing site exposure concentrations to the appropriate LUC statewide applicable SRVs or BTVs using the SRV spreadsheet.
5.5.1 SRV spreadsheets There are two SRV spreadsheets available on MPCA’s website: ·
SRV spreadsheet · Used when conducting an initial soil investigation and a remedial soil investigation · Contains SRVs using default parameters applicable to the majority of sites in Minnesota and BTVs
·
SRV spreadsheet – Site specific · Used when conducting a site specific risk assessment · Allows users to calculate site specific SRVs using site specific parameters to determine site specific cleanup values
This section describes using the statewide applicable SRVs and BTVs to conduct an initial soil investigation and a remedial soil investigation using the SRV spreadsheet. The use of site specific SRVs to conduct a site specific risk assessment using the SRV spreadsheet – Site specific is included in Section 8.0.
5.5.1.1 Characterizing acute risks An exposure point concentration (discrete sample) is used to evaluate acute risks. The maximum concentration of a contaminant should be compared to the LUC acute SRV or BTV. Acute SRVs and BTVs are only provided for the Residential/Recreational LUC. This is accomplished by using the SRV spreadsheet applicable to all sites in Minnesota in the following manner: Entering Site data into the SRV spreadsheet – “Res-Rec Worksheet” tab: · ·
Acute SRVs and BTVs are listed in column B · Not all chemicals have acute SRVs or BTVs Enter the site maximum discrete sample concentration into column C · Blue cells indicate chemicals with acute SRVs or BTVs, gray cells indicate chemicals that do not have SRVs or BTVs
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Characterizing potential acute risks: ·
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If maximum discrete sample concentration in column C is equal to or less than the applicable LUC acute SRV or BTV in column B, contaminant does not present a potential human health risk and is not considered a contaminant of concern (COC). If maximum discrete sample concentration in column C is greater than the applicable LUC acute SRV or BTV in column B, contaminant may present an unacceptable human health risk and is considered a COC. · Exceedance of an acute SRV or BTV does NOT indicate that there is an acute human health risk at the site, rather it indicates that further investigation is necessary to determine if a risk may be present. §
Although a responsible or voluntary party has the option to conduct further investigation, they may also chose to cleanup based on exceedance of an acute SRV or BTV instead of investigating further.
In this case, contact the MPCA project team to determine if immediate action should be taken to mitigate any potential risks and how to proceed with the investigation. In general, if maximum discrete sample concentration in column C is less than or equal to site background, contaminant does not present an unacceptable human health risks and is not considered a COC. ·
·
It is NOT appropriate to use composite or incremental sampling to evaluate acute risks.
5.5.1.2 Characterizing chronic risks An exposure area concentration (averaged over the entire exposure area) is used to evaluate chronic risks. The 95% upper confidence level (95 UCL) of the mean of the contaminants discrete samples should be compared to the LUC chronic SRV. If the 95 UCL is greater than the maximum concentration too few samples may have been obtained. In this case, if additional samples are not an option, the maximum concentration should be used. Other cases where the maximum concentration should be used are: when comparing to a BTV, using composite or incremental samples or when there is not enough data to calculate a 95 UCL of the mean (less than eight samples). This evaluation is accomplished by using the SRV spreadsheet applicable to all sites in Minnesota in the following manner: Residential/Recreational LUC Entering Site data into the SRV spreadsheet – “Res-Rec Worksheet” tab: ·
·
· ·
Final chronic SRVs and BTVs are listed in column D. · The final SRV is based on which SRV calculates to be the smallest value between the cancer and noncancer SRVs. · BTVs listed when the final SRV calculates to be less than the background contaminant soil concentration. Enter the site 95 UCL of the mean (or maximum when comparing to a BTV, using composite or incremental samples, 95 UCL of mean is larger than maximum or 95 UCL of mean cannot be calculated) concentration into column F. · Basis for the chronic SRV is listed in column E (Cancer, Noncancer, BTV, Csat, Max Limit). If there are noncancer risks associated with the contaminant, the contaminants individual noncancer hazard quotient (HQ) will automatically calculate in column G. If there are cancer risks associated with the contaminant, the contaminants individual cancer excess lifetime cancer risk (ELCR) will automatically calculate in column H.
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Characterizing potential chronic risks in the “Res-Rec Worksheet” tab: ·
·
·
If the 95 UCL of the mean (or maximum) concentration in column F is equal to or less than the applicable LUC chronic SRV or BTV (requires maximum) in column D, contaminant does not present a potential human health risk and is not considered a COC. · If there are noncancer risks associated with the contaminant, noncancer HQ listed in column G will be less than 1.0. · If there are cancer risks associated with the contaminant, cancer ELCR listed in column H will be less than 1E-05. If the 95 UCL of the mean (or maximum) concentration in column F is greater than the applicable LUC chronic SRV or BTV (requires maximum) in column D, contaminant may present an unacceptable human health risk and is considered a COC. · Exceedance of a chronic SRV or BTV (requires maximum) does NOT indicate that there is a chronic human health risk at the site, rather it indicates that further investigation is necessary to determine if a risk may be present. § Although a responsible or voluntary party has the option to conduct further investigation, they may also chose to cleanup based on exceedance of a SRV or BTV instead of investigating further. · Further investigation may include calculating a site specific cleanup value as part of a site specific risk assessment (please refer to section 8.0), performing additional statistical analysis of site data to compare to BTV (please refer to Section 7.0) or deriving a site specific background value (please refer to Section 7.0). · If there are noncancer risks associated with the contaminant, noncancer HQ listed in column G will be greater than 1.0 indicating how much of a potential risk over the acceptable level may be present. · If there are cancer risks associated with the contaminant, cancer ELCR listed in column H will be greater than 1E-05 indicating how much of a potential risk over the acceptable level may be present. In general, if the 95 UCL of the mean (or maximum) concentration in column F is less than or equal to site background, contaminant does not present an unacceptable human health risks and is not considered a COC.
Commercial/Industrial LUC Entering Site data into the SRV spreadsheet – “Com-Ind Worksheet” tab: ·
·
· ·
Final chronic SRVs and BTVs are listed in column B. · The final SRV is based on which SRV calculates to be the smallest value between the cancer and noncancer SRVs. · BTVs listed when the final SRV calculates to be less than the background contaminant soil concentration. Enter the site 95 UCL of the mean concentration (or maximum when comparing to a BTV, using composite or incremental samples, 95 UCL of mean is larger than maximum or 95 UCL of mean cannot be calculated) into column D. · Basis for the chronic SRV is listed in column C (Cancer, Noncancer, BTV, Csat, Max Limit). If there are noncancer risks associated with the contaminant, the contaminants individual noncancer HQ will automatically calculate in column E. If there are cancer risks associated with the contaminant, the contaminants individual cancer excess lifetime cancer risk (ELCR) will automatically calculate in column F.
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Characterizing potential chronic risks in the “Com-Ind Worksheet” tab: ·
·
·
If the 95 UCL of the mean (or maximum) concentration in column D is equal to or less than the applicable LUC chronic SRV or BTV (requires maximum) in column B, contaminant does not present a potential human health risk and is not considered a COC. · If there are noncancer risks associated with the contaminant, noncancer HQ listed in column E will be less than 1.0. · If there are cancer risks associated with the contaminant, cancer ELCR listed in column F will be less than 1E-05. If the 95 UCL of the mean (or maximum) concentration in column D is greater than the applicable LUC chronic SRV or BTV (requires maximum) in column B, contaminant may present an unacceptable human health risk and is considered a COC. · Exceedance of a chronic SRV or BTV does NOT indicate that there is a chronic human health risk at the site, rather it indicates that further investigation is necessary to determine if a risk may be present. § Although a responsible or voluntary party has the option to conduct further investigation, they may also chose to cleanup based on exceedance of a SRV or BTV instead of investigating further. · Further investigation may include calculating a site specific cleanup value as part of a site specific risk assessment (please refer to section 8.0), performing additional statistical analysis of site data to compare to BTV (please refer to Section 7.0) or deriving a site specific background value (please refer to Section 7.0). · If there are noncancer risks associated with the contaminant, noncancer HQ listed in column E will be greater than 1.0 indicating how much of a potential risk over the acceptable level may be present. · If there are cancer risks associated with the contaminant, cancer ELCR listed in column F will be greater than 1E-05 indicating how much of a potential risk over the acceptable level may be present. In general, if the 95 UCL of the mean (or maximum) concentration in column D is less than or equal to site background, contaminant does not present an unacceptable human health risks and is not considered a COC.
To determine the 95 UCL of the mean, EPA’s ProUCL software should be used. This software is available on EPA’s website (please refer to Appendix A for instructions, EPA 2011). Potential risks for contaminants that are not listed in the SRV spreadsheet and lack sufficient toxicity data to derive a site specific SRV should be evaluated qualitatively (please refer to Section 8.0 for additional information).
5.5.1.3 Background soil concentrations In general, if the exposure point concentration or exposure area concentration is equal to or less than site background concentrations, the contaminant does not present an unacceptable human health risks and is not considered a COC. BTVs representing statewide applicable background concentrations for contaminants with SRVs calculated to be below soil background concentrations are listed in the SRV spreadsheet. Responsible or non-responsible parties also have the option to determine site specific background (please refer to Section 7.0 for additional information).
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5.5.1.4 Additive risks In general, it is not necessary to perform a separate evaluation for additive risks when conducting an initial soil investigation or a remedial soil investigation when using the SRVs spreadsheet containing SRVs derived to be applicable to the majority of sites in Minnesota. These SRVs are derived using a combined HQ/relative source contribution (RSC) of 0.2 and an excess lifetime cancer risk (ELCR) of 1E-05 making them reasonably protective of potential additive noncancer and cancer risks at the majority of sites. If there is a site specific characteristic that a MPCA project team identifies as being a potential additive risk concern, an additive risk evaluation may be required as part of a risk evaluation. It is not appropriate to include BTVs in calculations of additive risk.
5.6 Uncertainty There are always uncertainties involved when conducting an initial and remedial soil investigation. It is important to acknowledge any uncertainties and the impacts they may have upon any conclusions resulting from the investigation. Uncertainties that could have a significant effect on the outcome of the risk evaluation (either an under or over estimate of risks) may exist for two reasons: ·
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Lack of knowledge of the site which can be reduced by additional research or knowledge · Site specific data or information · Scientific information Natural variability which cannot be reduced by additional research or knowledge
Some examples are exposure assumptions, sampling, laboratory analysis, toxicity information, contaminant speciation and professional judgment.
5.7 Conclusion The results from the initial and remedial soil investigation should include: · · ·
Quantitative results from the SRV spreadsheet · Whether contaminant concentrations exceed their respective SRVs Qualitative discussion of potential risks associated with contaminants lacking toxicity data Quantitative and/or qualitative discussion of uncertainty and how it may impact the quantitative results
If all contaminant concentrations are below the appropriate LUC SRVs or BTVs and both noncancer and cancer additive risks (when necessary to evaluate) are below target risks, it can be concluded that unacceptable human health risks do not exist at the site. If there are contaminant concentrations in exceedance of the appropriate LUC SRVs or BTVs and/or noncancer or cancer additive risks (when they are necessary to evaluate) are above target risks, this does NOT indicate there is an actual human health risk at the site. It indicates a need for further investigation to determine if there may be an actual human health risk at the site. Although a responsible or voluntary party has the option to conduct further investigation, they may also chose to cleanup based on exceedance of a SRV or BTV instead of investigating further.
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If there is a need to investigate further, discuss the available options with the MPCA project team. Three possible options are to: · · ·
Use additional soil considerations to eliminate a completed pathway (please refer to Section 6.0) Determine site specific background (please refer to Section 7.0) Conduct a site specific evaluation (please refer to Section 8.0)
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6.0 Additional soil considerations Additional soil considerations should be evaluated for any site that is being redeveloped when a potential human health risk is identified during the soil investigation. In some cases, it may be possible to eliminate the completed soil risk pathway at the site. Depending on the specific site redevelopment plan and the concentrations of the contaminants in soil, it may be possible to use some or all of the contaminated soil on-site. These additional considerations may make a considerable difference in how soil is used on the site or how much soil needs to be removed from the Site. This should be considered early in the process of site evaluation. Some soil on the site is often not suitable from an engineering standpoint and may need to be moved to a different location on-site within the zone of contamination or disposed of offsite in accordance with an approved work plan. In some cases, contaminated soil may be left in place or used onsite in ways that are protective of human health. Some examples of this are soil being used: · · · ·
Under paved areas such as, parking lots, roads and sports courts Under buildings In constructed landscaping features Left at depth on site
In some cases, the contaminated soil may require an appropriate institutional control(s) to acknowledge that impacted soil is left onsite and place restrictions on those areas if necessary. Soil sampling data from the soil investigation is used to make these decisions. Development of these options will need to be presented to the MPCA project team for review and approval but may be evaluated early on in the investigation process. Voluntary and responsible parties evaluate the engineering properties of soil to create a final site grading plan. Although, MPCA does not evaluate engineering properties of soil or approve engineering plans for construction, this information may be used to determine appropriate uses of soils on site as proposed in a redevelopment plan. Some items that may be considered during this process are: · ·
·
·
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Construction practices may produce changes in contaminant mobility or accessibility such as mechanical compaction or compaction by temporary surcharging. Soils of specific drainage characteristics may be needed to prevent surface ponding of water or to direct drainage in certain areas of the site. In areas where infiltration of runoff is to be encouraged soils with certain infiltration capacities may be specified. An example would be rain gardens or infiltration ponds. Landscaping of the site may be required to support various kinds of plant growth. Specific types of soil may be required to supports grasses, bushes, gardens, trees and open spaces may be required. Amendments to existing soil may be needed to support various types of vegetation on site. Occasionally visual soil barriers are constructed on Sites to reduce unsightly views or to act as noise screens or to limit access to a Site. It is sometimes possible to utilize impacted soil to construct such features. The appropriate clean cover thickness can be determined as part of the cleanup plan. Specific soils may be needed in certain areas to prevent soil instability and erosion from occurring. Armoring or rip rap may be required in areas where soil instability due to storm water flow may be required.
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7.0 Site specific background This section explains how site specific background may be determined. Site specific background is generally determined as part of a site specific risk assessment which is typically conducted after the remedial soil investigation has been completed and there were potential human health risks that need to be investigated further. Please refer to the following EPA guidance for additional details not included in this section, including explanations of specific statistical tests and instructions on how to use EPA’s ProUCL software (EPA 2016b). The most recent EPA recommendations are contained in the most recent version of the ProUCL User and Technical Guidance. The other two EPA guidance listed below were released in 2002. Please follow the most recently released ProUCL User and Technical Guide recommendations when they differ from those included in the 2002 guidance listed below. · · · ·
ProUCL Version 5.0.00 Technical Guide (EPA 2013a) ProUCL Version 5.0.00 User Guide (EPA 2013b) Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites (EPA 2002b) Role of Background in the CERCLA Cleanup Program (EPA 2002c)
For the purposes of this document, background is defined as the amount of a contaminant that is present in the soil that is not due to local anthropogenic sources, such as a release. Some inorganics are present in lower or higher concentrations in soil due to local geological characteristics. Some organics such as BaP and 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) may be present at low concentrations in soil that are not due to local anthropogenic sources due to their persistence and ability to be transported long distances. In general, if the exposure point concentration or exposure area concentration (maximum required) is equal to or less than site background concentrations, the contaminant does not present an unacceptable human health risks and is not considered a COC. BTVs representing statewide applicable background concentrations for contaminants with SRVs calculated to be below soil background concentrations are listed in the SRV spreadsheet (MPCA 2016d). Maximum site concentrations should be compared to BTVs. If the maximum site concentration exceeds a BTV, there are two options to investigate further: · ·
Compare site dataset to BTV using the proportions test (Section 7.1) Determine site specific background and compare to site data · Compare background and site datasets (Section 7.2.1) · Establish site specific BTV and compare to site dataset (Section 7.2.2)
7.1 Site dataset vs. BTV using proportions test If the site maximum concentration exceeds a BTV, the site dataset can be compared to the BTV using the proportions test available in EPA’s ProUCL software (EPA 2016b). It is recommended that this be accomplished first before determining site specific background since this comparison will be easier to accomplish and will not require obtaining any additional data.
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7.1.1 Outliers Before performing the proportions test it is important to eliminate any outliers from the site dataset. In general, the outlier tests listed below can be used with the site dataset under the conditions listed. Please refer to EPA’s ProUCL User Guide and Technical Guide for detailed descriptions of how to perform outlier tests. ·
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Dixon Test plus visual examination of box plot and Q-Q plot · Datasets with ≤ 25 samples · Can be used with nondetect data Rosner test plus visual examination of box plot and Q-Q plot · Datasets with ≥25 samples · Can be used with nondetect data
The decision to eliminate an outlier should not be made based on the outlier test alone. The project team must factor in other site specific information as well as results from outlier tests to determine whether they are true outliers or not. Additional statistics should be performed on both the original dataset without removal of any outliers as well as the dataset after outliers are removed to provide multiple lines of evidence that can be used to make an appropriate and reasonable site decision.
7.1.2 Proportions test The proportions test determines if an allowable proportion (ex. 1%, 5%, 10%) of the site dataset would likely exceed the BTV. For example, if the allowable proportion is 5% the test determines one of the following: · ·
5% of the dataset would likely exceeds the BTV 5% of the dataset would likely NOT exceed the BTV
EPA’s ProUCL User Guide and Technical Guide include details regarding how to perform the test and other items to consider including the potential for errors. In general, it is appropriate to use the following null and alternative hypothesis (labeled as Form 2 in ProUCL): · ·
H0 (null hypotheses): Proportion of exceedance of BTV by sampled data is > or = to 0.05 (5%) H1 (alternative hypothesis): Proportion of exceedance of BTV by sampled data is < 0.05 (5%)
The results of the test will either accept or reject H0. The results can be interpreted as indicated below: ·
·
H0 is NOT REJECTED · Site population exceedances of the BTV are > or = to 0.05 (5%) · Indicates that the site samples may not be representative of background concentrations and further investigation is required including site specific background (please refer to Section 7.2) H0 is REJECTED · Site population exceedances of the BTV are < 0.05 (5%) · Indicates that the site samples may be representative of background concentrations as long as there was an appropriate amount of site samples used, appropriate sampling and laboratory analysis of the samples were conducted and the test was performed appropriately
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In general, a confidence level of 0.95 and a proportion of 0.05 should be used as the default. It is also reasonable to use a range of confidence levels and proportions to show additional lines of evidence that may be used by the project team to make a reasonable and appropriate site specific decision. Results from the proportions test alone are not intended to indicate that the site dataset is or is not representative of background. Results are intended to provide an additional line of evidence that is used along with other site information to arrive at a reasonable site specific decision.
7.2 Comparing site and background dataset If the site maximum concentration exceeds a BTV, the first step to conduct further investigation is to compare the site dataset to the BTV using the proportions test (please refer to Section 7.1). If this has been accomplished and further investigation is required, a responsible or non-responsible party may use an appropriate background dataset to compare to the site dataset. The background dataset may consist of previously sampled data or sampling conducted specifically for this purpose. This may be accomplished in one of two ways: · ·
Compare background and site datasets (Section 7.2.5) Establish site specific BTV and compare to site dataset (Section 7.2.6)
Comparing the background and site datasets is the recommended method since it will result in the most accurate estimate of how closely site samples reflect background and will not require as high of a level of effort as establishing a site specific BTV and comparing it to the site dataset. Responsible and nonresponsible parties are not required to perform both evaluations but can if it appears that this additional line of evidence may be relevant to a site decision. The steps included in both of these evaluations that are identical are included below in sections: · · · ·
7.2.1: Background reference area 7.2.2: Sampling design and laboratory analysis 7.2.3: Outliers 7.2.4: Dataset distributions
The two different types of evaluations are included in sections: · ·
7.2.5: Comparing background and site datasets 7.2.6: Comparing site specific BTV and site dataset
7.2.1 Background reference area In some cases there may be existing background data from an appropriate background reference area that can be used to compare to site data. In other cases it may be necessary to collect background data from an appropriate background reference area. It may be appropriate to have more than one background reference area to reflect different conditions present at some sites. In either case, the criteria below will determine whether the background reference area is appropriate or not. Please refer to EPA’s Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites (2002) for additional information. ·
There must be a sufficient amount of samples in both the background reference area and the site dataset. · At a minimum 10 samples are necessary but depending on site specific factors, such as the contaminant, size, distribution of data, etc., more samples may be necessary.
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·
·
· ·
Samples must be collected in areas that have not been impacted by local anthropogenic sources and are representative of either: · Natural background conditions. · Ambient conditions in cases where the contaminant is persistent and has the ability to be transported long distances (example: benzo[a]pyrene and dioxin). Examples of some inappropriate areas are those impacted by runoff such as storm drains, stormwater ponds and ditches; areas where fill material has been added; areas near roads, parking lots, and railroads. Changes in the area that might have led to contamination (ex. past and current land use, added fill, excavations). Area must be similar to site in the following ways: · Soil characteristics (example: type, particle size distribution, horizon thickness, moisture content, soil density). · Geochemistry (redox conditions, pH, cation exchange, organic carbon). · Geologic origin. · Hydrogeologic situation. · Depth below ground surface (bgs). · Potential for contaminant mobility.
7.2.2 Sampling design and laboratory analysis The items to consider regarding sampling design and laboratory analysis listed below are intended to be an overview and may not include all items that need to be considered. EPA’s ProUCL User Guide, Technical Guide and Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites for additional information. · · · · · · · ·
There must be a sufficient amount of samples in both the background reference area and the site dataset. Sampling design should be the same for both the background and site. Sampling methods should be the same for both the background and site. Sampling type should be the same for both the background and site (example: discrete, composite or incremental). Sample digestion and laboratory analysis should be the same for both the background samples. For existing background datasets, consider when the data was obtained and if it will reflect current conditions (example: benzo[a]pyrene and dioxin concentrations may change over time). Appropriate quality assurance and quality control used during sampling and laboratory analysis. Depth below ground surface (bgs): · Ensure datasets are representative of one similar soil horizon. · If there is more than one type of soil horizon of interest, ensure there are separate datasets to represent each.
7.2.3 Outliers Before performing hypothesis testing it is important to eliminate any outliers from the site dataset. In general, the outlier tests listed below can be used with the site dataset under the conditions listed. Please refer to EPA’s ProUCL User Guide and Technical Guide for additional information.
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·
·
Dixon Test plus visual examination of box plot and Quantile-Quantile (Q-Q) plot · Datasets with ≤25 samples · Can be used with nondetect data · Un-transformed dataset Rosner test plus visual examination of box plot and Q-Q plot · Datasets with ≥25 samples · Can be used with nondetect data · Un-transformed dataset
The decision to eliminate an outlier should not be made based on the outlier test alone. The project team must factor in other site specific information as well as results from outlier tests to determine whether they are true outliers or not. Additional statistics should be performed on both the original dataset without removal of any outliers as well as the dataset after outliers are removed to provide multiple lines of evidence that can be used to make an appropriate and reasonable site decision.
7.2.4 Dataset distribution It is important to determine a datasets distribution as part of the evaluation. ProUCL contains a goodness-of-fit (GOF) tests that will provide results regarding whether the dataset appears to have a normal, lognormal or gamma distribution. Graphical displays such as a histogram and Q-Q plot are also useful in identifying a datasets distribution. Please refer to EPA’s ProUCL User Guide and Technical Guide for additional information.
7.2.5 Comparing background and site datasets ProUCL contains several parametric and nonparametric statistical tests that can be used to compare background datasets to site datasets. A list of the tests are provided below. Graphical displays such as a multiple Q-Q plot and side by side boxplot are also useful in comparing background and site datasets. Please refer to EPA’s ProUCL User Guide and Technical Guide for additional information. ·
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Student’s t-test · Parametric – generally used for normally distributed datasets § May also be used for datasets greater than 100 regardless of the distribution § May be appropriate to use for datasets greater than 20 to 30 when the data is reasonably symmetric regardless of the distribution · Do NOT use with log transformed data · Do NOT use with nondetect data · Sensitive to outliers Wilcoxon-Mann-Whitney test (WMW) · Nonparametric – use for datasets that are not normally distributed · Use with nondetect data · Use only when there is one detection limit · May conclude that datasets are the same when concentrations in the right tail differ significantly (use graphical displays to confirm this is not occurring) · More resistant to outliers than student’s t-test
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·
·
Gehan test · Nonparametric – use for datasets that are not normally distributed · Use when there are multiple detection limits · Use with nondetect data · Rejected null hypothesis could be a result of differing censoring mechanisms between the background and site dataset Tarone-Ware test (T-W) · Nonparametric – use for datasets that are not normally distributed · Use when there are multiple detection limits · Use with nondetect data · Rejected null hypothesis could be a result of differing censoring mechanisms between the background and site dataset
Results from the hypothesis test alone are NOT intended to indicate that the site dataset is or is not representative of background. The results are intended to provide an additional line of evidence that is used along with other site information to arrive at a reasonable site specific decision.
7.2.6 Comparing site specific BTV and site dataset ProUCL may be used to establish a site specific BTV based on the datasets upper tolerance limit (UTL). Please refer to EPA’s ProUCL User Guide and Technical Guide and MPCA’s Background Threshold Value (BTV) Evaluation for additional information (MPCA 2016f). Once a site specific BTV is determined, the proportions test discussed in Section 7.1 may be used to compare site data to the site specific BTV.
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8.0 Site specific soil cleanup values Site specific soil cleanup values are used to evaluate potential human risks to contaminated soil that are derived to be applicable to one specific site rather than any site in Minnesota. They can be determined based on site specific information including soil exposure parameters, soil properties and contaminant speciation in soil. Site specific cleanup values are determined as part of a site specific risk assessment which is typically conducted after the remedial soil investigation has been completed and there were potential human health risks that need to be investigated further. A site specific risk assessment may be less or more detailed depending on what factors influence the potential human health risks at a site and how much detail a responsible or voluntary party wishes to include. For example, although site specific soil properties can be used to determine site specific cleanup values, it is not necessary to include them. Site specific cleanup values could be determined based on site specific soil exposure parameters only. This section explains how a site specific risk assessment may be conducted to determine site specific clean up values. Some of the information included in this section is also included in Section 5.0 since it is common to both evaluations.
8.1 Conceptual site model A conceptual site model (CSM) is an overview of what has and is occurring at a site. It includes the source of contamination, fate and transport of contamination, receptors that may be exposed to contamination and potential exposure pathways. Soil exposure is only one part of the complete CSM which includes all media (groundwater, air, surface water, vapor intrusion). The CSM portion regarding soil contamination is developed and revised throughout the entire soil investigation as new information is available. At a minimum, the following items should be clearly illustrated in the soil portion of the CSM: · · · · ·
Site geological and hydrogeological settings Locations, concentrations and volumes of soil contamination Soil contaminant migration pathways Soil exposure pathways Potential receptors on or off site
8.2 Contaminants of concern Contaminants of concern (COCs) include any contaminants that have been determined to potentially present a human health risk at a site based on the remedial soil investigation. Any COCs from the remedial soil investigation should be included in the site specific risk assessment.
8.3 Exposure pathways and receptors All potential exposure pathways and receptors should be identified. For an exposure pathway to be complete, the following three conditions must exist: · · ·
Source of contamination Exposure route Potential receptor
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Possible routes of human health exposure to contaminants in soil include: · · · · · · ·
Incidental soil ingestion Ingestion via produce Ingestion via food chain Dermal contact with soil Inhalation via fugitive dust Inhalation via volatilization - outdoor air Inhalation via volatilization - indoor air
Routes of exposure included in the derivation of SRVs are bolded. The inhalation via volatilization indoor air route of exposure is evaluated during the vapor intrusion investigation. If any of the routes of exposure that are not bolded in the list apply to a site (except for the inhalation of volatilization – indoor air), it may be necessary to include an additional evaluation of that route of exposure in the site specific risk assessment. Potential receptors on or off site that may be exposed to site soil contamination should be identified. It is also important to identify the most sensitive receptor that may be exposed. In general, if there is no completed exposure pathway for a COPC then it can be eliminated.
8.4 Sampling Data obtained from sampling is used to estimate an exposure concentrations used to evaluate potential risks (please refer to Section 4.0 for additional information). The default soil depth a receptor is likely to be exposed to will vary by LUC. Exposure concentrations to evaluate any potential risks from ingestion, dermal or inhalation via fugitive dust should be calculated from samples obtained from the surface to the depth a receptor is likely to have exposure to (Table 1 and Figures 1 through 6 in the Soil Reference Value (SRV) Technical Support Document, MPCA 2016c). If a situation exists on site that does not meet the assumptions used to establish the applicable LUC depth of exposure, the exposure concentration is required to be obtained from the site specific depth the receptor is likely to have exposure to. When VOCs or SVOCs are present, exposure concentrations to evaluate potential outdoor inhalation risk from vapor should be calculated from subsurface samples obtained from an appropriate depth based on the specific contaminant present and site characteristics.
8.4.1 Data presentation Sampling data should be presented in a clear and concise manner in tables and include the following information and statistics (when possible) used in the soil investigations to characterize potential human health risks: · · · · · · ·
Sample date, identification and depth Results of each individual sample Detection limit Number of observations Frequency of detection Maximum Minimum
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· · · ·
Median Arithmetic mean and standard deviation 95% upper confidence level (95 UCL) of the mean (when possible) Identification of samples designated with J to reflect an estimated concentration
To determine the 95 UCL of the mean, EPA’s ProUCL software should be used. This software is available on EPA’s website (please refer to Appendix A for detailed instructions, EPA 2016b). This calculation can only be accomplished on datasets consisting of eight or more samples. Maximum concentrations should be used for composite or incremental samples. It is not appropriate to report the items bolded in the list above for composite or incremental samples.
8.4.2 Non-detect data The Kaplan Meier method available in EPA’s ProUCL software is recommended to evaluate non-detect data, including 2,3,7,8-TCDD and Benzo[a]pyrene equivalents. Please refer to Appendix B for instructions of how to accomplish this using.
8.5 Exposure concentrations An exposure concentration refers to the concentration of a chemical in soil that a receptor is expected to be exposed to at a contaminated site. There are two types of exposure concentrations used to reflect a receptors contact with contaminated soil: ·
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Exposure point concentration · Used to evaluate acute exposures · Exposure points are defined by discrete samples with one exposure concentration · Samples used should be representative of the depth to which the potential receptor may be exposed Exposure area concentration · Used to evaluate chronic, subchronic and short-term exposures · Exposure areas § Consists of areas with similar contamination § Do NOT contain uncontaminated soil § Do NOT contain hot spots · Samples from an exposure area are averaged over the entire exposure area to define an exposure area concentration · Samples used should be representative of the area and depth to which the potential receptor may be exposed · Must be determined in a way that reasonably reflects a receptors potential exposure across the entire site
Due to the possible transport of contamination off site, exposure areas or points may be located on or off site. Information regarding the CSM gathered during the soil investigation regarding site use should be taken into consideration when determining appropriate exposure area and exposure point concentrations. Areas containing significantly higher concentrations of contamination than surrounding areas are referred to as hot spots. These areas may have been subject to larger releases or contaminated in Soil Investigation Guidance • September 2016
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different ways than other areas of the site. All hot spots should be defined as distinct exposure areas and evaluated separately. It is not appropriate to use composite or incremental sampling to evaluate acute risks.
8.5.1 Area and time weighted exposure point concentrations An exposure concentration is intended to be a spatial average and is assumed to be equal to the temporal average based on the following assumptions: · · ·
Soil concentrations remain constant over time (there is no mechanism decreasing contaminant concentrations over time, such as biodegradation) Samples represent a uniform, random distribution of soil samples over the entire exposure area A receptor is equally likely to be exposed to any exposure points within the exposure area
Rationale and data should be provided for any adjustments made to an exposure concentration due to biodegradation. In some cases, the spatial average exposure concentration is not equal to the temporal average exposure concentration. It may be appropriate to use area or time weighted exposure concentrations if detailed site specific exposure pattern information is known and if necessary, potential future site use is known and considered. This does require the approval of a MPCA or MDH risk assessor and the Remediation project team.
8.5.1.1 Area weighted exposure concentration For cases where samples (contaminant concentrations) are not evenly spaced over the exposure area but a receptor’s exposure is equally likely over the entire exposure area, an area weighted average exposure concentration can be calculated.
8.5.1.2 Time weighted exposure concentration For cases where a receptor is not equally likely to be exposed over the entire exposure area but the samples are evenly spaced over the exposure area, a time weighted average exposure concentration can be calculated. In this case, the most conservative applicable exposure assumptions must be used to derive the site specific SRVs.
8.5.2 Soil concentration modeling Data from actual sampling is the most accurate method of determining an exposure concentration and is always preferred. In some cases modeling may be appropriate if the site situation does not allow sampling.
8.6 Soil reference values Soil reference values (SRVs) are a screening tool used to evaluate potential human health risks from soil exposure. They are derived based on EPA Superfund methodology using exposure assumptions based on specific soil land use categories (LUC) depicting a specific soil land use scenario and set of receptors. For some chemicals, SRVs derived based on exposure parameters and toxicity values calculate to be below background soil concentrations. An evaluation was conducted to determine if specific SRVs were below soil background concentrations and if necessary establish appropriate background values (Background Threshold Values or BTVs) that could be used instead of the health based SRV.
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Additional detail regarding SRVs and BTVs, including descriptions of the LUCs, SRV methodology and exposure parameters and a list of chemical with BTVs may be found in the following MPCA guidance: · · · ·
Soil Reference Value (SRV) Technical Support Document (MPCA 2016c) SRV spreadsheet (MPCA 2016d) SRV spreadsheet – Site specific (MPCA 2016e) Background Threshold Value (BTV) Evaluation (MPCA 2016f)
Soil reference values (SRVs) evaluate chronic noncancer and cancer risks as well as acute noncancer risks for a limited number of chemicals.
8.7 Applicable LUC SRVs Information regarding the conceptual site model (CSM) gathered during the soil investigation should be used to determine the appropriate land use category (LUC) of SRVs applicable to the site. There are two sets of LUC SRVs: · ·
Residential/Recreational * Commercial/Industrial
* The Residential/Recreational LUC has three sub categories: Single Family Homes, Multi-Family Housing and Recreational. Residential/Recreational SRVs are used with all three sub categories. Land use categories (LUC) have been developed depicting specific scenarios and receptors. LUCs characterize two things: · ·
LUC specific exposure parameters used to derive LUC specific SRVs Accessible and potentially accessible zone depths that a human receptor is expected to access
LUCs are summarized in Table 1 and depicted in Figures 1 through 6 in the Soil Reference Value (SRV) Technical Support Document. There are also two clauses: Impervious Surface and Utility Corridor that apply to all of the LUCs which are explained in Section 2.0 of the Soil Reference Value (SRV) Technical Support Document. Further explanation regarding appropriate depths to use when conducting a response action including the use of institutional controls is provided in the Property Use Guidance (MPCA 2016a).
8.8 Risk characterization 8.8.1 SRV spreadsheets There are two SRV spreadsheets available on MPCA’s website: ·
SRV spreadsheet · Used when conducting an initial soil investigation and a remedial soil investigation · Contains SRVs using default parameters applicable to the majority of sites in Minnesota and BTVs · Contains two sets of SRVs and BTVs based on the applicable LUC: Residential/Recreational and Commercial/Industrial · Chronic SRVs and BTVs are included for both the Residential/Recreational and Commercial/Industrial LUCs
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Acute SRVs and BTVs are included for a limited number of chemicals for the Residential/Recreational LUC · BTVs are included for contaminants with SRVs calculated to be below soil background concentrations SRV spreadsheet – Site specific · Used when conducting a site specific risk assessment · Allows users to calculate site specific SRVs using site specific parameters to determine site specific cleanup values · Contains two sets of SRVs and BTVs based on the applicable LUC: Residential/Recreational and Commercial/Industrial · Chronic SRVs and BTVs are included for both the Residential/Recreational and Commercial/Industrial LUCs · Acute SRVs and BTVs are included for a limited number of chemicals for the Residential/Recreational LUC · BTVs are included for contaminants with SRVs calculated to be below soil background concentrations ·
·
This section describes how site specific cleanup values can be established during a site specific risk assessment using the SRV spreadsheet – Site specific. The use of the statewide applicable SRVs during an initial soil investigation or a remedial soil investigation using the SRV spreadsheet is included in Section 5.0, Using soil reference values.
8.8.1.1 Characterizing acute risks An exposure point concentration (discrete sample) is used to evaluate acute risks. The maximum concentration of a contaminant should be compared to the LUC acute noncancer SRV, BTV or site specific cleanup value. Acute noncancer SRVs and BTVs are only provided for Residential/Recreational LUC. If a contaminant exceeds the screening acute noncancer SRV or BTV the MPCA project team should be notified promptly to determine whether immediate action is necessary or not. In some cases a site specific acute cleanup value may be appropriate to establish. The SRV Spreadsheet – Site specific can be used to establish site specific acute cleanup values as follows in one of two ways: · ·
Derive a site specific acute noncancer SRV based on modification of the allowed parameters. · Use the site specific acute noncancer SRV as the site specific acute noncancer cleanup value. Derive multiple site specific acute noncancer SRVs using different modifications of the allowed parameters to show a range of potential acute noncancer SRVs (a range of potential risks based on comparison to the site exposure concentration to the different acute noncancer SRVs). · Establish an appropriate site specific acute noncancer cleanup value using that information combined with site specific information regarding the site scenario.
Allowed modifications to acute noncancer SRV parameters are listed in Table 4. This table presents when a specific modification is allowed under a LUC, when MPCA approval is necessary, whether the change may be made in the spreadsheet or if it requires a MPCA risk assessor to make the change and the appropriate use of the modification. For example, for acute noncancer SRVs there are two parameters that may be modified: ·
Toxicity value (“Toxicity Data” tab) · Modification can be made for any Residential/Recreational scenario · Requires approval of MPCA project team including a MPCA risk assessor · Requires MPCA risk assessor make modification in the SRV spreadsheet – Site specific
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Example of appropriate modification § Toxicity value used is not applicable to the species of the chemical that is present at the site but there is another toxicity value that is applicable to that species Ingestion rate (“Res-Rec Equations” tab, Equation 9) · Modification can be made for any Residential/Recreational scenario · Requires approval of MPCA project team including a MPCA risk assessor · Modification can be made in SRV spreadsheet – Site specific · Example of appropriate modification § Modification of ingestion rate from 10,000 mg/day to 5,000 mg/day and 7,500 mg/day to show a range of potential acute noncancer SRVs using reduced ingestion rates ·
·
After a site specific cleanup value has been determined based on either a 1) site specific acute noncancer SRV or 2) established based on a range of potential acute noncancer SRVs, site data may be entered in the SRV spreadsheet – “Res-Rec Worksheet” tab following the instructions below. For a site specific cleanup value based on a site specific acute noncancer SRV, the site specific acute noncancer cleanup value will automatically have been calculated in the SRV spreadsheet – Site specific (column B). For a site specific cleanup value based on a range of potential acute noncancer SRVs, the site specific acute noncancer cleanup value will be modified in the SRV spreadsheet – Site specific MPCA risk assessor and provided to the responsible or non-responsible party. · ·
Any site specific acute noncancer cleanup values will be listed in column B · Not all chemicals have acute site specific cleanup values Enter the site maximum discrete sample concentration into column C · Blue cells indicate chemicals with site specific acute noncancer cleanup values, SRVs or BTVs, gray cells indicate chemicals that do not have site specific acute cleanup values, SRVs or BTVs
Characterizing potential acute risks: ·
·
·
If maximum discrete sample concentration in column C is equal to or less than the applicable site specific acute noncancer cleanup value in column B, contaminant does not present a potential human health risk and is not considered a contaminant of concern (COC). If maximum discrete sample concentration in column C is greater than the applicable site specific acute noncancer cleanup value, contaminant may present an unacceptable human health risk and is considered a COC. · Exceedance of a site specific acute noncancer cleanup value does NOT indicate that there is an acute human health risk at the site, rather it indicates that further investigation is necessary to determine if a risk may be present. · In this case, contact the MPCA project team to determine if immediate action should be taken to mitigate any potential risks and how to proceed with the investigation. · Further investigation may include use of other toxicity information regarding the chemical to determine an appropriate level of exposure where there is no concern of acute noncancer health risks. In general, if maximum discrete sample concentration in column C is less than or equal to site background, contaminant does not present an unacceptable human health risks and is not considered a COC.
It is NOT appropriate to use composite or incremental sampling to evaluate acute risks. Soil Investigation Guidance • September 2016
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8.8.1.2 Characterizing chronic risks An exposure area concentration (averaged over the entire exposure area) is used to evaluate chronic risks. The 95% upper confidence level (95 UCL) of the mean of the contaminants discrete samples should be compared to the LUC chronic SRV or site specific cleanup value. If the 95 UCL is greater than the maximum concentration too few samples may have been obtained. In this case, if additional samples are not an option, the maximum concentration should be used. Other cases where the maximum concentration should be used are: when comparing to a BTV, using composite or incremental samples or when there is not enough data to calculate a 95 UCL of the mean (less than 8 samples). This evaluation is accomplished by using the SRV spreadsheet – Site specific can be used to establish site specific acute cleanup values as follows in one of two ways: · ·
Derive a site specific chronic SRV based on modification of the allowed parameters. · Use the site specific chronic SRV as the site specific chronic cleanup value. Derive multiple site specific chronic SRVs using different modifications of the allowed parameters to show a range of potential chronic SRVs (a range of potential risks based on comparison to the site exposure concentration to the different chronic SRVs). · Establish an appropriate site specific chronic cleanup value using that information combined with site specific information regarding the site scenario.
Allowed modifications to chronic SRV parameters are listed in Table 4. This table presents when a specific modification is allowed under a LUC, when MPCA approval is necessary, whether the change may be made in the spreadsheet or if it requires a MPCA risk assessor to make the change and the appropriate use of the modification. There are many parameters that can be modified for chronic SRVs. The SRV Range of Risks Spreadsheet should be used to display the different SRVs so they can be easily compared and reviewed by internal MPCA staff and external parties (MPCA 2016g). Although the spreadsheet provides some pre-established modifications to allow the user to have a framework to start from, modifications may be changed to reflect site specific information. Two examples of parameters that can be modified are included below but are NOT the only parameters that may be modified. ·
·
Noncancer hazard quotient (“Res-Rec Equations” tab, Equation 3, “Com/Ind” tab, Equation 11) · Modification can be made for any Residential/Recreational or Commercial/Industrial scenario · Requires approval of MPCA project team including MPCA risk assessor · Modification can be made in SRV spreadsheet – Site specific · Example of appropriate modification § Present a range of potential risks based on HQs from 0.2 to 1 Ingestion rate (“Res-Rec Equations” tab, Equations 1 and 3, “Com/Ind” tab, Equation 10 and 11) · Modification can be made for any Residential/Recreational or Commercial/Industrial scenario · Requires approval of MPCA project team including MPCA risk assessor · Modification can be made in SRV spreadsheet – Site specific · Example of appropriate modification § Present a range of potential risks based on appropriate central and upper percentile estimates
After a site specific cleanup value has been determined based on either a 1) site specific chronic SRV or 2) established based on a range of potential chronic SRVs, site data may be entered in the SRV spreadsheet – “Res-Rec Worksheet” or “Com/Ind Worksheet” tab following the instructions below. Soil Investigation Guidance • September 2016
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For a site specific cleanup value based on a site specific chronic SRV, the site specific chronic cleanup value will automatically have been calculated in the SRV spreadsheet – Site specific. For a site specific cleanup value based on a range of potential chronic SRVs, the site specific acute noncancer cleanup value will be modified in the SRV spreadsheet – Site specific MPCA risk assessor and provided to the responsible or non-responsible party. ·
·
·
·
Any site specific chronic cleanup values will be listed in · “Res-Rec Worksheet” tab, column D · “Com/Ind Worksheet” tab, column B · The final SRV is based on which SRV calculates to be the smallest value between the cancer and noncancer SRVs Enter the site 95 UCL of the mean concentration (or maximum if necessary) into · “Res-Rec Worksheet” tab, column F · “Com/Ind Worksheet” tab, column D If there are noncancer risks associated with the contaminant, the contaminants individual noncancer hazard quotient (HQ) will automatically calculate in · “Res-Rec Worksheet” tab, column G · “Com/Ind Worksheet” tab, column E If there are cancer risks associated with the contaminant, the contaminants individual cancer excess lifetime cancer risk (ELCR) will automatically calculate in · “Res-Rec Worksheet” tab, column H · “Com/Ind Worksheet” tab, column F
Characterizing potential chronic risks: ·
·
·
If the 95 UCL of the mean (or maximum) concentration is equal to or less than the applicable LUC site specific chronic cleanup value, contaminant does not present a potential human health risk and is not considered a COC. · If there are noncancer risks associated with the contaminant, noncancer HQ will be less than 1.0. · If there are cancer risks associated with the contaminant, cancer ELCR will be less than 1E-05. If the 95 UCL of the mean (or maximum) concentration in column F is greater than the applicable LUC site specific chronic cleanup value, contaminant may present an unacceptable human health risk and is considered a COC. · Exceedance of a chronic site specific cleanup value does NOT indicate that there is a chronic human health risk at the site, rather it indicates that further investigation is necessary to determine if a risk may be present. · Further investigation may include use of other toxicity information regarding the chemical to determine an appropriate level of exposure where there is no concern of acute noncancer health risks. · If there are noncancer risks associated with the contaminant, noncancer HQ will be greater than 1.0 indicating how much of a potential risk over the acceptable level may be present. · If there are cancer risks associated with the contaminant, cancer ELCR will be greater than 1E-05 indicating how much of a potential risk over the acceptable level may be present. In general, if the 95 UCL of the mean (or maximum) concentration is less than or equal to site background, contaminant does not present an unacceptable human health risks and is not considered a COC.
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8.8.1.3 Additive risks Additive risks are generally required to be evaluated quantitatively using the SRV spreadsheet – Site specific since site specific chronic cleanup values are established using modified site specific exposure parameters. All site noncancer risks are summed according to similar target endpoints and compared to a HQ of 1.0. All cancer risks are summed and compared to an excess lifetime cancer risk (ELCR) of 1E-05. · ·
· ·
If the summed noncancer risks (HI or Hazard Index) for a specific target endpoint are equal to or less than 1.0, there is not an unacceptable additive noncancer human health risk on site. If the summed noncancer risks for a specific target endpoint are greater than 1.0, there is a potential unacceptable additive noncancer human health risk on site and indicates that further investigation needs to be conducted to determine if an actual risk exists. If the summed cancer risks are equal to or less than 1E-05, there is not an unacceptable additive cancer human health risk on site. If the summed cancer risks are greater than 1E-05, there is a potential unacceptable additive cancer human health risk on site and indicates that further investigation needs to be conducted to determine if an actual risk exists.
In some cases, it may not be possible to evaluate additive risks quantitatively and it may be necessary and appropriate to evaluate additive risks qualitatively. It is not appropriate to include BTVs in calculations of additive risk.
8.8.1.4 Background soil concentrations In general, if the exposure point concentration or exposure area concentration (maximum required) is equal to or less than site background concentrations, the contaminant does not present an unacceptable human health risks ad is not considered a COC. BTVs representing statewide applicable background concentrations for contaminants with SRVs calculated to be below soil background concentrations are listed in the SRV spreadsheet – Site specific. Responsible or voluntary parties also have the option to determine site specific background (please refer to Section 7.0 for additional information).
8.9 Uncertainty A thorough explanation of the uncertainties involved in the risk evaluation should be provided. Uncertainties that could have a significant effect on the outcome of the risk evaluation (either an under or over estimate of risks) may exist for two reasons: ·
·
Lack of knowledge of the site which can be reduced by additional research or knowledge · Site specific data or information · Scientific information Natural variability which cannot be reduced by additional research or knowledge
There are many uncertainties involved in the risk evaluation. Some examples are exposure assumptions, sampling, laboratory analysis, toxicity information, contaminant speciation and professional judgment.
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8.10 Conclusion A concise summary should be provided indicating whether an unacceptable human health risk exists on site. This summary should include: ·
· ·
Quantitative results from the SRV spreadsheet – Site specific · Whether contaminant concentrations exceed their respective site specific cleanup values · Whether the additive risk evaluations exceed the target noncancer and cancer risk levels Qualitative discussion of potential risks associated with contaminants lacking toxicity data Quantitative and/or qualitative discussion of uncertainty and how it may impact the quantitative results
If all contaminant concentrations are below the site specific cleanup values and both noncancer and cancer additive risks are below target risks, it can be concluded that unacceptable human health risk do not exist at the site. If there are contaminant concentrations in exceedance of the site specific cleanup values and/or noncancer or cancer additive risks are above target risks, this does not indicate there is an actual human health risk at the site. It indicates a need for further investigation to determine if there may be an actual human health risk at the site. This investigation includes risk management principles such as use of institutional controls, type and likelihood of exposure, potential reuse of soil, exposure prevention methods along with professional judgement (please refer to Section 6.0, Additional Soil Considerations, for additional information).
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9.0 References ASTM 1992. American Society for Testing Materials. 1992. Field Screening Procedures Applied to Soils for use in Risk Assessments. STP1158. ASTM International, West Conshohocken, PA. http://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP23829S.htm. ASTM 2008. American Society for Testing Materials. 2008. Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process for Forestland or Rural Property. ASTM E2247-08. ASTM International, West Conshohocken, PA. http://www.astm.org/Standards/E2247.htm. ASTM 2011. American Society for Testing Materials. 2011. Standard Practice for Environmental Site Assessments: Phase II Environmental Site Assessment Process. ASTM E1903-11. ASTM International, West Conshohocken, PA. http://www.astm.org/Standards/E1903.htm. ASTM 2013. American Society for Testing Materials. 2013. Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process. ASTM E1527-13. ASTM International, West Conshohocken, PA. http://www.astm.org/Standards/E1527.htm. 40 CFR Part 312. Code of Federal Regulations. Accessed July 2016. Title 40 - Protection of the Environment, Chapter 1 – Environmental Protection Agency, Subchapter J – Superfund, Emergency Planning, and Community right-To-Know Programs, Part 312 – Innocent Landowners, Standards for Conducting all Appropriate Inquiries, Subpart C – Standards and Practices, 312.20 - All Appropriate Inquiry. http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title40/40cfr312_main_02.tpl. 40 CFR Part 300. Code of Federal Regulations. Accessed July 2016. Title 40 - Protection of the Environment, Chapter 1 – Environmental Protection Agency, Subchapter J – Superfund, Emergency Planning, and Community right-To-Know Programs, Part 300 – National Oil and Hazardous Substances Pollution Contingency Plan, Subpart L – National Oil and Hazardous Substances Pollution Contingency Plan; Involuntary Acquisition of Property by the Government, Appendix A - Hazard Ranking System. http://www.ecfr.gov/cgi-bin/textidx?SID=080988e2abcfe26940ffa30c002b038e&mc=true&node=ap40.28.300_11105.a&rgn=div9. EPA 1986. Environmental Protection Agency. October 1986. RCRA Facility Assessment Guidance. PB87107769. https://www.epa.gov/hw/guidance-initial-site-assessment-corrective-action-sites. EPA 1988. Environmental Protection Agency. October 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA, Interim Final. 9355.3-01. https://rais.ornl.gov/documents/GUIDANCE.PDF. EPA 1989. Environmental Protection Agency. May 1989. Interim Final RCRA Facility Investigation (RFI) Guidance Volume 1 of IV. 9502.00-6D. http://bit.ly/29wv7Ns. EPA 1991. Environmental Protection Agency. September 1991. Guidance for Performing Preliminary Assessments Under CERCLA. 9345.0-01A. http://bit.ly/29QS6oc. EPA 1992. U.S. Environmental Protection Agency. September 1992. Guidance for Performing Site Inspections Under CERCLA. 9345.1-05. http://bit.ly/29GV406. EPA 2002a. U.S. Environmental Protection Agency. 2002. Guidance on Choosing a Sampling Design for Environmental Data Collection. http://www.epa.gov/QUALITY/qs-docs/g5s-final.pdf. EPA 2002b. U.S. Environmental Protection Agency. September 2002. Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites. EPA 540-R-01-003. OSWER 9285.7-41. https://dec.alaska.gov/spar/csp/guidance_forms/docs/background.pdf. Soil Investigation Guidance • September 2016
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EPA 2002c. U.S. Environmental Protection Agency. April 26 2002. Role of Background in CERCLA Cleanup Program. OSWER 9285.6-07P. https://rais.ornl.gov/documents/bkgpol_jan01.pdf. EPA 2007. U.S. Environmental Protection Agency. Last Updated July 12, 2016. Accessed July 2016. SW-846 Online. https://www.epa.gov/hw-sw846. EPA 2013a. U.S. Environmental Protection Agency, Barnett, F.; Lockheed Martin, Singh, A., Maichle, R. September 2013. ProUCL Version 5.0.00 User Guide. EPA/600/R-07/041. https://www.epa.gov/landresearch/proucl-version-5000-documentation-downloads. EPA 2013bc. U.S. Environmental Protection Agency, Barnett, F.; Lockheed Martin, Singh, A.; University of Las Vegas Singh, A. K. September 2013. ProUCL Version 5.0.00 Technical Guide. EPA/600/R-07/041. https://www.epa.gov/land-research/proucl-version-5000-documentation-downloads. EPA 2015. U.S. Environmental Protection Agency. Last updated December 17, 2015. Accessed July 2016. CLU-IN website with Characterization and Monitoring Guidance. https://clu-in.org/characterization/. EPA 2016a. U.S. Environmental Protection Agency. Last Updated May 2016. Accessed July 2016. Superfund Remedial Investigation/Feasibility Study (Site Characterization) website. https://www.epa.gov/superfund/superfund-remedial-investigationfeasibility-study-sitecharacterization. EPA 2016b. U.S. Environmental Protection Agency. June 20 2016. ProUCL Software Version 5.1.00. https://www.epa.gov/land-research/proucl-software. EPA RFI. U.S. Environmental Protection Agency. Accessed July 2016. RCRA Facility Investigation Scope of Work. https://www3.epa.gov/reg3wcmd/ca/pdf/RCRA_FacilititiesInvestigationATTB.pdf. ITRC 2012. Interstate Technical Regulatory Council. 2012. Incremental Sampling Methodology. http://www.itrcweb.org/ism-1/#. MPCA 2008. Minnesota Pollution Control Agency. 2008 Soil Sample Collection and Analysis Procedures. c-prp4-04. https://www.pca.state.mn.us/sites/default/files/c-prp4-04.pdf. MPCA 2013. Minnesota Pollution Control Agency. Soil Leaching Values. May 2013. c-r1-04. https://www.pca.state.mn.us/waste/cleanup-guidance. MPCA 2016a. Minnesota Pollution Control Agency. 2016. Property Use Guidance. c-rem3-08. https://www.pca.state.mn.us/waste/risk-based-site-evaluation-guidance. MPCA 2016b. Minnesota Pollution Control Agency. Accessed July 2016. Website with Quality System Guidance. https://www.pca.state.mn.us/about-mpca/mpca-quality-system. MPCA 2016c. Minnesota Pollution Control Agency. 2016. Soil Reference Value Technical Support Document. c-r1-05. https://www.pca.state.mn.us/waste/risk-based-site-evaluation-guidance. MPCA 2016d. Minnesota Pollution Control Agency. 2016. SRV spreadsheet. c-r1-06. http://www.pca.state.mn.us/enzq83d. MPCA 2016e. Minnesota Pollution Control Agency. 2016. SRV spreadsheet – Site specific. c-r1-07. http://www.pca.state.mn.us/enzq83d. MPCA 2016f. Minnesota Pollution control Agency. Background Threshold Value (BTV) Evaluation. c-r1-08. http://www.pca.state.mn.us/enzq83d. MPCA 2016g. Minnesota Pollution control Agency. SRV Range of Risks Spreadsheet. c-r1-15. http://www.pca.state.mn.us/enzq83d.
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Tables
Agricultural * Adhesives
Corrosives/pH
Asbestos
Dioxin/Furans
Explosives/Propellant
Selenium/Molybdenum
PCP
PCBs
Cyanide
Metals and metalloids
Pesticides
Fuels (GRO, DRO, Fuel Oil, TPH)
PAHs
SVOCs
Site type
VOCs
Table 1. Typical site contaminants
Please contact the Minnesota Department of Agriculture x
x
x
x
Ash and slag disposal
x
x
Asphalt plant, disposal
x
x x
Autobody shop
x
x
x
x
Aviation and aerospace mfg
x
x
x
x
x
x
x
Battery recycling and disposal Cement plants
x
x
x
Ceramics works
x
x
x
Chemical and dye manufacturing/recycling
x
x
x
Chlor-Alkali manufacturing
x
x
x
Coal Burning
x
Cosmetics manufacturing
x
Demolition debris
x
Drum recycling
x
Dry cleaning
x
x
x x x
x
x
x
x x
x
x
x
x
x
x
x
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Electronics (Semiconductors, circuit board printing)
x
Food processing
x
Foundries
x
Gasoline stations
x
Glass manufacturing
x
Corrosives/pH
Asbestos
Dioxin/Furans
Explosives/Propellant
Selenium/Molybdenum
PCP
PCBs
Cyanide
Metals and metalloids
x x
x
x
x
x
x
x
x
x Please contact the Minnesota Department of Agriculture
x
Incinerators Injection molding
Pesticides
x
Grain storage * Hospitals
Fuels (GRO, DRO, Fuel Oil, TPH)
PAHs
SVOCs
VOCs
Site type
x
x
x
x
x
x
x
x
Inorganic chemical manufacturing
x
Inorganic organic pigments
x
Landfills and uncontrolled dumps
x
x x
x x
x
x
Leather manufacturing Machine shops and metal fabrication
x
x
Manufactured gas plants and coal gasification
x
x
Marine maintenance
x
Metal plating and finishing
x
Metal ore, mining, and smelting operations
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x x
Soil Investigation Guidance • September 2016
x x
x
x x
x
x
x
x x
x
x
Minnesota Pollution Control Agency 50
Corrosives/pH
x
Please contact the Minnesota Department of Agriculture
Petroleum refining and reuse
x
Pharmaceutical manufacturing
x
Photographic film manufacturing and development
x
Pipe yard
x
Plastic manufacturing
x
Printing and ink manufacturing
x
Railroad yards
x
x
Research and educational institutions
x
x
Rubber manufacturing
x
Shooting ranges Tank farms
x
Tannery
x
Tar disposal
x
x x
Pesticide manufacturing and use *
Asbestos
x
Dioxin/Furans
Paint, ink formulation
x
x x
Explosives/Propellant
x
Selenium/Molybdenum
Painting and automobile body repair
x
PCP
x
x
PCBs
Ordnance/Explosive storage and manufacturing
x
Cyanide
x
x
Metals and metalloids
Mining
x
Pesticides
x
Fuels (GRO, DRO, Fuel Oil, TPH)
SVOCs
x
PAHs
VOCs
Metal recycling/Scrap yards and automobile salvage
Site type
x
x
x
x x
x
x x
x
x
x
x x x
x
x x
x
x
x
x
x x
x
x
x
x
x
x x
x
x
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x
x
Minnesota Pollution Control Agency 51
x
Urban fill
x
Vehicle maintenance
x
Waste oil
x
x x
x x
Wood preservation/Treatment *
x
x
Corrosives/pH
Explosives/Propellant
Selenium/Molybdenum
PCP
PCBs
Asbestos
Underground storage tanks
Cyanide
Metals and metalloids
x
Dioxin/Furans
Transformer refurbishing
Pesticides
Fuels (GRO, DRO, Fuel Oil, TPH)
PAHs
SVOCs
VOCs
Site type
x
x
x
x
x
x
x
x
x
x
Please contact the Minnesota Department of Agriculture
Wood pulp and paper manufacturing (paper, sanitary tissue, cardboard)
x
Wood product manufacturing (lumber, plywood)
x
x
x
x
x
x
* Sites with agricultural contaminants should be referred to Minnesota Department of Agriculture
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Table 2. Screening methods
Screening method
Contaminant
Method advantages
Method limitations Readings sensitive to effective contaminant volatility, water content, sample temperature, and sample handling Some units can be bulky and heavy Not sensitive enough to obtain conclusive results for chlorinated VOCs present at low levels
Rapid and inexpensive PID/FID (organic vapor screening analysis)
VOCs
Useful to focus sampling High concentrations of VOCs (>1000 ppm vapor) may suggest NAPL presence
Gas chromatography (Portable/field GC units, ECD, ELCD, SAWS)
VOCs, SVOCs, PCB, PAH, PCP, petroleum hydrocarbons, pesticides, dioxin, nitroaromatic explosives
Potentially cost-effective
Experienced operator required
Low detection limits (able to measure maximum contaminant level (MCL) concentrations)
Learning curve associated with use of equipment
Quick turnaround time
Library of components limited for mass spectrometer
High-quality data generated
Petroleum carrier solvent can cause interference with analysis for PCP
Portable
Modification of extraction time can be necessary to improve consistency of results
High sample throughput
Poor extraction of diesel fuels from soils with high organic matter
Good correlation with EPA’s Contract Laboratory Program (CLP) laboratory data Ability to perform simultaneous analysis for BTEX and other hydrocarbon compounds
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Screening method
Infrared spectrophotometry
Contaminant
Petroleum hydrocarbons
Method advantages
Method limitations
Portable
Method only allows to determine what functional groups are in a substance
Real-time data
Difficulty in analyzing complex organic samples (sample may contain several C-H bonds indicated by several large unsharp peaks)
Easy to use
Interference caused by water vapor which may require purging with nitrogen or argon gas
Can be application specific
Ultraviolet visible spectrophotometry
Metal ions, conjugated organic compounds, biological macromolecules
Easy to use and maintain
Does not discriminate between the sample of interest and contaminants that absorb at the same wavelength
Sample integrity is maintained (no manipulation of the material being measured is required)
Erroneous reading may be recorded from impurities in sample that reflect light Absorption results can be influenced by temperature, pH, and impurities Sepctrophotometer can have inadequate sensitivity at low sample concentrations
Quick analysis
Non-destructive sampling
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Screening method
UV Florescence
Contaminant
Petroleum hydrocarbons, PAH, PCB
Method advantages
Method limitations
Can illuminate NAPLs that fluoresce including those that contain PAHs (coal tar, creosote, petroleum products) and those mixed with fluorescent impurities (i.e. oil and grease removed by solvent during degreasing, or humic compounds from natural organic matter)
Significant potential for false positives and false negatives
Can provide detailed information on relationship between stratigraphy and fluorescent NAPL distribution
Interference from non-target fluorescent materials (ex: shell fragments in lake sediment)
Can guide selection of subsamples for chemical or saturation analysis
Chlorinated solvents generally do not fluoresce when exposed to UV light unless commingled with sufficient fluorescent impurities
Can detect more than three to six log orders of concentration without sample dilution or modification of sample
Fiber-optic chemical sensor/LIF
VOC, PAH, petroleum hydrocarbons
Bubbles in sample preparation can result in erratic readings
Potentially cost-effective
Possible interference from other chlorinated VOCs
Can be used in situ
Concentration of contaminants affects instrument response time
Easy to use
Primarily applicable to PAHs; very limited use/experience at chlorinated solvent sites
Portable Quick turnaround time
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Screening method
X-ray fluorescence
Mercury vapor analyzer
Contaminant
Heavy metals
Mercury
Method advantages
Method limitations
Potentially cost-effective No investigation-derived waste (IDW) Good correlation with analytical laboratory results Real-time data
Limit on penetration depth Some field-portable units require liquid nitrogen
Quick turnaround time Capability to determine multiple contaminants simultaneously Nondestructive method Little sample preparation Consistent quality of data Real-time data Quick turnaround time Potentially cost-effective Near real-time data Reproducible results
VOCs, SVOCs, PAHs, PCBs, Mercury, Test kits heavy metals, NAPL, (Immunoassay, test pesticides, PCP, strips, shake tests) dioxin, petroleum hydrocarbons
Reasonable correlation with laboratory results
One field-portable unit weighs 50 pounds Preparation of quality control sample required Difficulty in obtaining sufficiently low detection limits because of matrix interference Detection limits sometimes not low enough to respond to ecological concerns Some a contaminants have high detection limits
Learning curve associated with use of equipment High rate of false positives found in results from PCB and organic pesticide kits Incapable of identifying individual PAHs Poor extraction efficiency in peat or bog samples Sufficient reagent needs to be provided to obtain valid results
Low rate of false negative results, except when fuel compounds were highly degraded
Detection limits sometimes not low enough, and test kit concentration ranges are limited
Portability
Can give false negatives if fuel products are degraded
Detection limits capable of meeting action levels
Visual contrast can be difficult to see in dark soil
Capable of defining boundaries of contamination
Dye can be an irritant and possible mutagen
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Screening method
Contaminant
Method advantages
Method limitations
Potentially cost-effective
Expensive for a limited number of sample locations
Continuous, real-time data
Direct push (Cone penetrometer, membrane interface probe)
VOC, SVOC,PAH, TPH, NAPL
Accurate measurements Three-dimensional mapping possible Contaminant fingerprinting capability Enhanced delineation of contaminant (2-inch vertical resolution) No soil cuttings Portable/versatile Quick decontamination Capability to identify thin stratigraphic layers that conventional layers miss
Naturally occurring fluorescent material can lead to false positives Limited by rough terrain Difficult to maneuver in tight spaces Subsurface cobbles cause probe refusal Susceptible to operator error/Experienced operator needed
Data can allow selection of optimal confirmation soil boring locations
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Table 3. Sample collection tools Tool
Hand auger
Advantages
Disadvantages
Allows sampling in shallow sub-surface areas difficult to access
Limited sampling depths
Allows safer shallow sub-surface sampling in areas with buried utilities
Sample may be disrupted and aerated
Comments
Difficult to penetrate hard materials
Easy to acquire large sample volume from surface layer or exposed sampling horizon Quick, uncomplicated; does not require expensive equipment or trained operators Hand scoop, trowel or shovel
Allows access to remote, small, crowded areas
Allows collection of headspace-free samples for VOC analyses from exposed surfaces or cores Subcoring samplers
Targets discrete layers for sampling Allows access to deep subsurface
Mechanical rotary drilling with splitspoon sampling or hydraulic push coring
Allows collection of sample at discrete depth intervals Allows collection of intact cores at significant depths including below the groundwater
Difficult to obtain deeper subsurface samples
Used to sample surface soil
Samples limited to discrete layer with limited volume
Used to sample soil from ground, splitspoon, or soil pile
Biased sample selection may not be representative of entire target interval
Some vendors offer efficient systems for collection and storage of samples
Difficult to obtain samples in hard soil or when rocks and debris are present
Soil may be easily extruded into sample containers
Limited to areas accessible by larger drilling machinery Results in relatively large boreholes with a significant volume of soil cuttings generated Used with mechanical drilling Multiple samples may be necessary for adequate volumes
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To obtain adequate volumes, subcoring of sleeve may be used
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Tool
Sonic rotary drilling
Advantages
Disadvantages
Allows access to deep subsurface
Limited to use in areas accessible by larger drilling machinery
Comments
Allows collection of relatively large, undisturbed and continuous sub-surface soil cores
Results in relatively large boreholes with a significant volume of soil cuttings generated Used to obtain stratigraphic information
Allows collection of samples at discrete depth intervals
Casing may heat up and cause sample to lose volatiles
Subcoring may prevent potential loss of volatiles from soil
Penetration through layers of hard soil and soil with rock fragments may be limited
Allows access to a wide range of locations since drilling machines are smaller
Direct push coring
Allows deep penetration to sub-surface through a small borehole with relatively little soil disturbance
Sampling depth may be limited compared to other types of mechanical drilling methods in some types of soil Sample volumes of target layers may be limited in individual cores for smaller diameter coring sleeves May be difficult to accurately target discrete layers in some types of soil
Drilling machines are smaller than the mechanical rotary drilling and sonic rotary drilling
Relatively high equipment cost for small investigations Management of large volumes of excavated materials may be required if hazardous or unsuitable for backfilling Allows access up to 20 feet below the ground surface Large volumes of soil or buried material can be recovered from the subsurface
Mechanical excavator
Exposes large areas of subsurface allowing for observation of buried waste and debris
Accessibility for large equipment Restoration of excavation areas is often required Measures must be taken to ensure excavation stability and safety Excavation depth limited by equipment size and soil stability
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Com/Ind Modification Allowed
X
X
X
X
X
X
Present a range of potential risks based on ELCR's from 1E-06 to 1E-04
Hazard quotient (HQ)
X
X
X
X
X
X
X
Present a range of potential risks based on HQ's from 0.2 to 1
Toxicity values
X
X
X
X
X
X
Exposure frequency
X
X
X
X
X
Sufficient rational exists to support difference, ex. nursing home, state forest
Exposure duration
X
X
X
X
X
Sufficient rational exists to support difference, ex. hospital, nursing home
Modification requires modified SRV Spreadsheet from MPCA risk assessor
Res/Rec-Recreational Modification Allowed
X
Approval required 3
Res/Rec-MFH Other 2 Modification Allowed
Excess Lifetime Cancer Risk (ELCR)
Parameter
Res/Rec-Single Family Home Modification Allowed
Res/Rec-MFH - Multi Family Housing 1 Modification Allowed
Modification can be made in site specific SRV spreadsheet
Table 4. Site specific SRV parameter modifications
Appropriate purpose of modification
Cancer and chronic noncancer SRVs
X
Value is more appropriate to use with different species of chemical present
Ingestion rate
X
X
X
X
X
X
X
Present a range of potential risks based on appropriate central and upper percentile estimates
Adherence factor
X
X
X
X
X
X
X
Evaluation of upland sediments
Dermal absorption
X
X
X
X
X
X
X
Value is more appropriate to use with different species of chemical present
Gastrointestinal absorption
X
X
X
X
X
X
X
Value is more appropriate to use with different species of chemical present
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X
X
X
Modification requires modified SRV Spreadsheet from MPCA risk assessor
Com/Ind Modification Allowed
X
Modification can be made in site specific SRV spreadsheet
Res/Rec-Recreational Modification Allowed
X
Approval required 3
Res/Rec-MFH Other 2 Modification Allowed
X
Res/Rec-MFH - Multi Family Housing 1 Modification Allowed
Relative bioavailability
Res/Rec-Single Family Home Modification Allowed
Parameter
X
Appropriate purpose of modification Value appropriate to use with species of chemical present and site soil characteristics
Age dependent adjustment factors
Not appropriate to modify
Cancer averaging time
Not appropriate to modify
Noncancer averaging time
X
X
X
X
X
Modification is automated in spreadsheet when exposure duration is modified
Body weight
Not appropriate to modify
Surface area
Not appropriate to modify
Standard volatilization factor Inverse of mean concentration
X
X
X
X
X
X
X
Site specific modeling or different source area than default of 0.5 acre square
Dry soil bulk density
X
X
X
X
X
X
X
Site specific data
Inverse of mean concentration
X
X
X
X
X
X
X
Site specific modeling or different source area than default of 0.5 acre square
Dry soil bulk density
X
X
X
X
X
X
X
Site specific data
Average depth of source (thickness)
X
X
X
X
X
X
X
Site specific data
X
X
X
X
X
X
X
Site specific data
Mass limit volatilization factor
Apparent diffusivity Air filled soil porosity
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Com/Ind Modification Allowed
X
X
X
X
X
Site specific data
Total soil porosity
X
X
X
X
X
X
X
Automatically calculated when soil particle density and dry soil bulk density are modified
Soil particle density
X
X
X
X
X
X
X
Site specific data
Dry soil bulk density
X
X
X
X
X
X
X
Site specific data
Fraction of organic carbon in soil
X
X
X
X
X
X
X
Site specific data
X
X
X
X
X
X
X
Site specific modeling or different source area than default of 0.5 acre square
X
X
X
X
X
X
Sufficient rational exists to support difference, ex. no significant amount of exposed soil
Modification requires modified SRV Spreadsheet from MPCA risk assessor
Res/Rec-Recreational Modification Allowed
Modification can be made in site specific SRV spreadsheet
Res/Rec-MFH Other 2 Modification Allowed
X
Approval required 3
Res/Rec-MFH - Multi Family Housing 1 Modification Allowed
X
Res/Rec-Single Family Home Modification Allowed
Water filled soil porosity
Parameter
Appropriate purpose of modification
Particulate emission factor Inverse of mean concentration Fraction of vegetative cover Mean annual windspeed (MAW) 4
X
X
X
X
X
X
X
4
X
X
X
X
X
X
X
X
X
X
X
X
X
X
All three parameters: MAW, ETV and dependent function are required to be modified at the same time based on modeling
Dry soil bulk density
X
X
X
X
X
X
X
Site specific data
Fraction of organic carbon in soil
X
X
X
X
X
X
X
Site specific data
Water filled soil porosity
X
X
X
X
X
X
X
Site specific data
Air filled soil porosity
X
X
X
X
X
X
X
Site specific data
Equivalent threshold value (ETV)
MAW and EVT dependent function 4 Soil saturation limit
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Com/Ind Modification Allowed
X
X
X
X
X
Automatically calculated when soil particle density and dry soil bulk density are modified
Soil particle density
X
X
X
X
X
X
X
Site specific data
X
X
X
X
NA
X
Modification requires modified SRV Spreadsheet from MPCA risk assessor
Res/Rec-Recreational Modification Allowed
Modification can be made in site specific SRV spreadsheet
Res/Rec-MFH Other 2 Modification Allowed
X
Approval required 3
Res/Rec-MFH - Multi Family Housing 1 Modification Allowed
X
Res/Rec-Single Family Home Modification Allowed
Total soil porosity
Parameter
Appropriate purpose of modification
Acute noncancer SRV Toxicity value Ingestion rate
X
X
X
X
NA
X
X X
Value is more appropriate to use with different species of chemical present Present a range of potential risks based on appropriate central and upper percentile estimates
Res/Rec - Residential/Recreational Com/Ind - Commercial/Industrial 1
- Includes "multi-family housing" portion of the Res/Rec-Multi-Family Housing and Other Areas Soil Land Use Category
2
- Includes "other" portion of the Res/Rec-Multi-Family Housing and Other Areas Soil Land Use Category
3
- Modifications must be approved by MPCA project team and MPCA risk assessor
4
- MAW, ETV and dependent function are all required to be modified at the same time based on modeling
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Appendix A – Calculating 95 UCL of the mean 1. In ProUCL, open up a new worksheet by choosing “File”, then “New”.
2. Name the first column to identify the contaminant by clicking on the header and choosing “Header Name”. The “HeaderNameForm” window will open. Enter the contaminant name (Chem Z) and click “OK”.
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3. If your data contains non-detect values, name the second column with the same name as the first column with a “D_” attached to the beginning. a. If your data does NOT contain any nondetect values, do NOT name the second column.
4. Enter the data into the first column (“Chem Z”). If the data you received from the lab is under the laboratory reporting limit but greater than the detection limit (J-flagged or estimated values), enter the estimated value into the worksheet treating it as a detected concentration. Enter the detection limit for all other nondetect values. a. The dataset must contain at least eight samples to calculate the 95 UCL of the mean. b. If you do not have any non-detect values you only need to enter the data into the first column. You do NOT need to enter anything into the second column. Make sure there is no header name on the second column. If there is a header name you can eliminate it by deleting the title using the same process used to enter the title. Soil Investigation Guidance • September 2016
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5. If any of the values in column one are non-detect values entered in as the detection limit, fill in the second column as described below: a. Enter a “0” for a nondetect (based on detection limit rather than an actual sample concentration). b. Enter a “1” for a detected value (based on an actual sample concentration).
6. Choose “UCLs/EPCs”, then “All”.
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7. The “Select Variables” window will open.
8. Select the dataset you want to calculate the 95 UCL of the mean for by highlighting it under the “Available Variables” list and clicking the “>>” button to move it to the “Selected Variables” list. You can calculate 95 UCL of means for more than one dataset at once.
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9. Press “OK”.
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10. ProUCL will return a list of possible 95 UCL of mean values based on the data’s distribution. There is a suggested 95 UCL of the mean listed at the end (inside green circle above). Users must evaluate the results presented to determine the most appropriate 95 UCL of the mean to use based on the data and the ProUCL calculations.
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Appendix B – Calculating TCDD and B[a]P equivalents Follow the instructions below to calculate 2,3,7,8-TCDD (TCDD) and benzo[a]pyrene (B[a]P), carcinogenic PAHs or cPAHs) equivalents using ProUCL and the Kaplan Meier method for non-detect data. Please refer to Figure B-1 for a flowchart depicting the process. Figure B-1. Calculating B[a]P and TCDD Equivalents Flowchart
Are all cPAHs detected?
YES
NO Proceed to Step 2
Proceed to Step 1
80% or less nondetects?
8 or more samples?
YES YES 95 UCL of all samples vs. SRV
NO
NO Proceed to Step 5
Proceed to Step 3
Each sample mean vs. SRV 8 or more samples?
8 or more samples?
NO
YES
95 UCL of all samples vs. SRV
Each sample mean vs. SRV
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YES 95 UCL of all samples vs. SRV
NO
Each sample mean vs. SRV
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Step 1 - No Non-detect data present ·
If all of the carcinogenic PAHs (cPAHs) have been detected follow the instructions below in Step 1. If not, proceed to Step 2. You will need to calculate a BaP and TCDD equivalent concentration for each individual discrete sample. Use the SRV spreadsheet to calculate the following (MPCA 2016d, MPCA 2016e): 1. Potency equivalent factor (PEF) for each of the cPAHs analyzed in each sample using the “BaP Equivalent” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Potency Equivalency Factors” (PEF) column contains the PEF that the site concentration is multiplied by to calculate the individual cPAH BaP equivalent concentration. d. There are a series of two columns titled “Site Concentration” and “BaP Equivalent” (starts with columns E and F and ends with AQ and AR). e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 5). f.
Enter the site concentration for the cPAH into the “Site Concentration” column and the “BaP Equivalent” concentration will automatically be calculated (multiples the site concentration by the cPAH PEF).
g. If you have eight or more samples. i. Enter the individual sample “Total BaP equivalents” (row 31) into ProUCL and calculate the 95 UCL of the mean using the instructions in Appendix A. ii. Compare the 95 UCL of the mean of your samples to the BaP SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). h. If you have less than eight samples. i. When you do not have eight or more samples, you cannot calculate the 95 UCL of the mean and compare it to the SRV. In this case you will need to compare each “sample mean” to the SRV. 2. Compare the individual sample mean from the “Total BaP Equivalents” column (row 31) to the BaP SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial).Toxicity equivalence factor (TEF) for each of the TCDDs analyzed in each sample using the “TCDD Equivalents” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Toxicity Equivalency Factor (TEF)” column (B) contains the TEF that the site concentration is multiplied by to calculate the individual TCDD equivalent concentration. Soil Investigation Guidance • September 2016
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d. There are a series of two columns titled “Site Concentration” and “TCDD Equivalent” (starts with columns C and D and ends with AO and AP). e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 4). f.
Enter the site concentration for the TCDD into the “Site Concentration” column and the “TCDD Equivalent” concentration will automatically be calculated (multiples the site concentration by the TCDD TEF).
g. If you have more than eight samples: i. Enter the individual sample “Total TCDD equivalents” (row 45) into ProUCL and calculate the 95 UCL of the mean using the instructions in Appendix A. ii. Compare the 95 UCL of the mean of your samples to the TCDD SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). h. If you have less than eight samples: i. When you do not have eight or more samples, you cannot calculate the 95 UCL of the mean and compare it to the SRV. In this case you will need to compare each “sample mean” to the SRV. ii. Compare the individual sample mean from the “Total TCDD Equivalents” column (row 45) to the TCDD SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial).
Step 2 - Non-detect data present ·
Determine the percentage of cPAH non-detects by dividing the number of non-detects in each sample by the total number of cPAHs sampled and then multiplying by 100. For example, if you sampled all 25 cPAHs and results indicated 10 non-detects, you would perform the following calculation to determine the percentage of non-detects: 10/25*100 = 40% non-detects. 1. If you have 80% or less non-detect data, the Kaplan Meier method should be used to calculate the KM Mean, proceed to Steps 3 and 4. 2. If you have greater than 80% non-detect data, the Kaplan Meier method should not be used, proceed to step 5.
Step 3 - 80% or less non-detect data ·
You will need to calculate a BaP and TCDD equivalent concentration for each individual discrete sample. Use the SRV spreadsheet to calculate the following: 1. Potency equivalent factor (PEF) for each of the cPAHs analyzed in each sample using the “BaP Equivalent” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Potency Equivalency Factors” (PEF) column contains the PEF that the site concentration is multiplied by to calculate the individual cPAH BaP equivalent concentration.
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d. There are a series of two columns titled “Site Concentration” and “BaP Equivalent” (starts with columns E and F and ends with AQ and AR) e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 5). f. Enter the site concentration for the cPAH into the “Site Concentration” column and the “BaP Equivalent” concentration will automatically be calculated (multiples the site concentration by the cPAH PEF). If the data you received from the lab is under the laboratory reporting limit but greater than the detection limit (J flagged or estimated values), enter the estimated value into the spreadsheet treating it like it is a detected concentration. Enter the reporting limit (or method detection limit if one is available) for all non-detect cPAHs. g. Proceed to Step 4 to calculate the BaP equivalent concentration using the Kaplan Meier method. 2. TCDD equivalent concentration for each of the TCDDs analyzed in each sample using the “TCDD Equivalents” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Toxicity Equivalency Factor (TEF)” column (B) contains the TEF that the site concentration is multiplied by to calculate the individual TCDD equivalent concentration. d. There are a series of two columns titled “Site Concentration” and “TCDD Equivalent” (starts with columns C and D and ends with AO and AP). e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 4). f.
Enter the site concentration for the TCDD into the “Site Concentration” column and the “TCDD Equivalent” concentration will automatically be calculated (multiples the site concentration by the TCDD TEF). If the data you received from the lab is under the laboratory reporting limit but greater than the detection limit (J flagged or estimated values), enter the estimated value into the spreadsheet treating it like it is a detected concentration. Enter the reporting limit (or method detection limit if one is available) for all non-detect TCDDs.
g. Proceed to Step 4 to calculate the BaP equivalent concentration using the Kaplan Meier method.
Step 4 - Kaplan Meier method ·
Use EPA’s ProUCL software to calculate the Kaplan Meier mean (KM Mean in ProUCL) B[a]P and/or TCDD equivalent concentration. 1. EPA’s ProUCL software is available to download for free (EPA 2016b). 2. In ProUCL, open up a new worksheet by choosing “File”, then “New”.
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3. Name the first column to identify the sample (ex. “Sample 1”) by clicking on the header and choosing “Header Name”. The “HeaderNameForm” window will open. Enter the title of that column and click “OK”.
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4. Name the second column with a “D_” in front of the name you gave the first column (ex. “D_Sample 1”) by clicking on the header and choosing “Header Name”. The “HeaderNameForm” window will open. Enter the title of that column and click “OK”.
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5. Enter the individual cPAH or TCDD data from the “SRV spreadsheet” into the first column (ex. “Sample 1”) in ProUCL. a. For BaP equivalents, enter any data under the “BaP Equivalents” tab for individual cPAHs from the SRV spreadsheet (rows 6 through 30) into the first column (ex. “Sample 1”) in ProUCL. b. For TCDD equivalents, enter any data under the “TCDD Equivalents” tab for the individual TCDDs from the SRV spreadsheet (rows 6 through 44) into the first column (ex. “Sample 1”) in ProUCL. 6. Under the second column (ex. “D_Sample 1”), enter a “0” if the sample (concentration) is non-detect data (based on a reporting limit or method detection limit if one is available rather than an actual sample concentration) and a “1” if it is a detected concentration. 7. Repeat this procedure for each additional sample listed in the “SRV spreadsheet” using additional columns across the spreadsheet (ex. “Sample 2” would be entered into columns 2 and 3 in the ProUCL spreadsheet).
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8. Under “Stats/Sample Sizes”, chose “General Statistics”, “With NDs”, “Raw Statistics”. The “Select Variables” window will open. Click the “>>” button to choose the data you want to use to calculate the “General Statistics”. You can choose all of your cores (samples) at the same time. Click “OK” to run the calculation.
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9. ProUCL will calculate “General Statistics” including the Kaplan Meier mean which is the value you will use to compare to the SRVs (see “KM Mean” in the blue circle below).
10. Multiply the “KM Mean” from ProUCL (value in blue circle above) by the number of cPAHs and/or TCDDs that were analyzed for and included in the calculation. Enter this value into the “SRV spreadsheet”, “Total B[a]P Equivalent – Kaplan Meier” (row 32) and/or “TCDD Equivalents – Kaplan Meier” (row 46) under the appropriate sample (ex. “Sample 1”). For example: If 15 cPAHs were analyzed for, the calculation would be 15 * 0.00423 = 0.0635 mg/kg. a. If the laboratory reports the three fluoranthenes (benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene) as total fluoranthenes count this as one cPAH. If the laboratory reports two of the fluoranthenes (benzo[b]fluoranthene and benzo[j]fluoranthene) as benzo[b,j]fluoranthene, count this as 1 cPAH.
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11. If you have eight or more samples: a. Enter the individual sample “Total B[a]P Equivalents – Kaplan Meier” (row 32) and/or “Total TCDD equivalents – Kaplan Meier” (row 46) into ProUCL and calculate the 95 UCL of the mean using the instructions in Appendix A. b. Compare the 95 UCL of the mean of your samples to the B[a]P equivalent and/or TCDD equivalent SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). 12. If you have less than eight samples: a. When you do not have eight or more samples, you cannot calculate the 95 UCL of the mean and compare it to the SRV. In this case you will need to compare each “sample mean” to the SRV. b. Compare the individual sample mean from the “Total B[a]P Equivalents – Kaplan Meier” column (row 32) and/or “Total TCDD equivalents – Kaplan Meier” column (row 46) to the B[a]P equivalent and/or TCDD equivalent SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial).
Step 5 - Greater than 80% non-detect data ·
When a dataset has greater than 80% non-detect data, Kaplan Meier is no better than stating the B[a]P equivalent or TCDD equivalent concentration is somewhere between the B[a]P equivalent or TCDD equivalent concentration calculated when replacing the non-detect data with the full method detection limit and when replacing the non-detect data with zeros. Use the “SRV spreadsheet” to calculate the potency equivalent factor (PEF) for each of the cPAHs and/or TCDDs analyzed. 1. Determine if appropriate reporting limits have been used by comparing the reporting limits used for your samples (found in the laboratory report) to those listed in the Table B-1 for cPAHs and Table B-2 for TCDD equivalents below. a. If the reporting limit used by the laboratory for a cPAH and/or TCDD is equal to or less than the reporting limit in the table, appropriate reporting limits were used for that cPAH and/or TCDD. All cPAHs and/or TCDDs need to be checked. If all cPAHs and TCDDs have been analyzed using appropriate reporting limits, skip to number 2 below to calculate total B[a]P equivalents and/or number 3 to calculate total TCDD equivalents. b. If any of the cPAHs and/or TCDDs did not use an appropriate reporting limit, you cannot calculate B[a]P and/or TCDD equivalents using the instructions in numbers 2 and 3 below. In this case, you will need to either re-analyze your samples for the cPAHs and/or TCDDS that did not have appropriate reporting limits or obtain new samples. The laboratory will be able to help you decide which one makes sense in your case. i. If the laboratory is able to re-run the sample and obtain a lower reporting limit, equal to or less than that in Table 1, it might be beneficial to run your sample again for that cPAH and/or TCDD. ii. If the laboratory had to dilute your sample resulting in an increase in the reporting limit for a cPAH and/or TCDD, you will probably need to obtain new samples.
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2. Use the SRV spreadsheet to calculate the potency equivalent factor (PEF) for each of the cPAHs analyzed in each sample using the “BaP Equivalent” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Potency Equivalency Factors” (PEF) column contains the PEF that the site concentration is multiplied by to calculate the individual cPAH BaP equivalent concentration. d. There are a series of two columns titled “Site Concentration” and “BaP Equivalent” (starts with columns E and F and ends with AQ and AR). e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 5). f.
Enter the site concentration for the cPAH into the “Site Concentration” column and the “BaP Equivalent” concentration will automatically be calculated (multiples the site concentration by the cPAH PEF). If the data you received from the lab is under the laboratory reporting limit but greater than the method detection limit (J flagged or estimated values), enter the estimated value into the spreadsheet treating it like it is a detected concentration. Enter the half the reporting limit (or method detection limit if one is available) for all non-detect cPAHs.
g. If you have more than eight samples: i. Enter the individual sample “Total BaP equivalents” (row 31) into ProUCL and calculate the 95 UCL of the mean using the instructions in Appendix A. ii. Compare the 95 UCL of the mean of your samples to the BaP SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). h. If you have less than eight samples: i. When you do not have eight or more samples, you cannot calculate the 95 UCL of the mean and compare it to the SRV. In this case you will need to compare each “sample mean” to the SRV ii. Compare the individual sample mean from the “Total BaP Equivalents” column (row 31) to the BaP SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). 3. Use the SRV spreadsheet to calculate the toxicity equivalence factor (TEF) for each if the TCDDs analyzed in each sample using the “TCDD Equivalents” tab. a. The spreadsheet is arranged to accommodate a total of 20 individual discrete samples. b. If you have more than 20 samples you can either use another copy of the SRV spreadsheet or request a copy of the SRV spreadsheet with columns for the number of additional samples necessary. c. The “Toxicity Equivalency Factor (TEF)” column (B) contains the TEF that the site concentration is multiplied by to calculate the individual TCDD equivalent concentration. Soil Investigation Guidance • September 2016
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d. There are a series of two columns titled “Site Concentration” and “TCDD Equivalent” (starts with columns C and D and ends with AO and AP). e. Enter the sample number or identification in the column that has “Enter Sample ID” (row 4). f.
Enter the site concentration for the TCDD into the “Site Concentration” column and the “TCDD Equivalent” concentration will automatically be calculated (multiples the site concentration by the TCDD TEF). If the data you received from the lab is under the laboratory reporting limit but greater than the method detection limit (J flagged or estimated values), enter the estimated value into the spreadsheet treating it like it is a detected concentration. Enter the one-half the reporting limit (or method detection limit if one is available) for all nondetect TCDDs.
g. If you have more than eight samples: i. Enter the individual sample “Total TCDD equivalents” (row 45) into ProUCL and calculate the 95 UCL of the mean using the instructions in Appendix A. ii. Compare the 95 UCL of the mean of your samples to the TCDD SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial). h. If you have less than eight samples: i. When you do not have eight or more samples, you cannot calculate the 95 UCL of the mean and compare it to the SRV. In this case you will need to compare each “sample mean” to the SRV ii. Compare the individual sample mean from the “Total TCDD Equivalents” column (row 45) to the TCDD SRV of the applicable LUC (Residential/Recreational or Commercial/Industrial).
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Table B-1. Carcinogenic PAH reporting limits Carcinogenic PAH (cPAH)
Potency equivalent factor (PEF)
Appropriate maximum reporting limit mg/kg *
Benz[a]anthracene
0.1
0.01
Benzo[b]fluoranthene
0.1
0.03
Benzo[j]fluoranthene
0.1
0.03
Benzo[k]fluoranthene
0.1
0.03
1
0.01
Chrysene
0.01
0.01
Dibenz[a,h]acridine
0.1
0.01
Dibenz[a,h]anthracene
0.56
0.01
7H-Dibenzo[c,g]carbazole
1
0.01
Dibenzo[a,e]pyrene
1
0.01
Dibenzo[a,h]pyrene
10
0.01
Dibenzo[a,i]pyrene
10
0.01
Dibenzo[a,l]pyrene
10
0.01
7,12-Dimethylbenzanthracene
34
0.01
Indeno[1,2,3,-c,d]pyrene
0.1
0.01
3-Methylcholanthrene
3
0.01
5-Methylchrysene
1
0.01
Benzo[a]pyrene
* Laboratory reporting limits listed will need to be corrected for dry weight. Table B-2. TCDD reporting limits TCDD
Potency equivalent factor (PEF)
Appropriate maximum reporting limit pg/g
Dioxins 2,3,7,8-TCDD
1
0.060
Other TCDD
0
0.060
1,2,3,7,8-PeCDD
1
0.060
Other PeCDD
0
0.060
1,2,3,4,7,8-HxCDD
0.1
0.060
1,2,3,6,7,8-HxCDD
0.1
0.060
1,2,3,7,8,9-HxCDD
0.1
0.060
0
0.060
0.01
0.060
0
0.060
0.0003
0.060
2,3,7,8-TCDF
0.1
0.060
Other TCDF
0
0.060
1,2,3,7,8-PeCDF
0.03
0.060
2,3,4,7,8-PeCDF
0.3
0.060
0
0.060
Other HxCDD 1,2,3,4,6,7,8-HpCDD Other HpCDD 1,2,3,4,6,7,8,9-OCDD Furans
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TCDD
Potency equivalent factor (PEF)
Appropriate maximum reporting limit pg/g
1,2,3,4,7,8-HxCDF
0.1
0.060
1,2,3,6,7,8-HxCDF
0.1
0.060
2,3,4,6,7,8-HxCDF
0.1
0.060
1,2,3,7,8,9-HxCDF
0.1
0.060
Other HxCDF
0
0.060
1,2,3,4,6,7,8-HpCDF
0.01
0.060
1,2,3,4,7,8,9-HpCDF
0.01
0.060
0
0.060
0.0003
0.060
0.0001
0.090
3,4,4',5-TeCB (PCB 81)
0.0003
0.10
2,3,3',4,4'-PeCB (PCB 105)
0.00003
0.15
2,3,4,4',5-PeCB (PCB 114)
0.00003
0.19
2,3',4,4',5-PeCB (PCB 118)
0.00003
0.19
2',3,4,4',5-PeCB (PCB 123)
0.00003
0.19
3,3',4,4',5-PeCB (PCB 126)
0.1
0.20
2,3,3',4,4',5-HxCB (PCB 156)
0.00003
0.081
2,3,3',4,4',5'-HxCB (PCB 157)
0.00003
0.081
2,3',4,4',5,5'-HxCB (PCB 167)
0.00003
0.064
3,3',4,4',5,5'-HxCB (PCB 169)
0.03
0.070
0.00003
0.11
Other HpCDF 1,2,3,4,6,7,8,9-OCDF PCBs 3,3'4,4'-TeCB (PCB 77)
2,3,3',4,4',5,5'-HpCB (PCB 189)
* Laboratory reporting limits listed will need to be corrected for dry weight.
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