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Geotechnical Engineering Services

 

Pierce County Project CRP 5757 9th Street East, between 190th Avenue East and 198th Street East Pierce County, Washington

 

for

 

Pierce County Public Works and Utilities

 

May 31, 2013

 

       

Earth Science + Technology

                       

Geotechnical Engineering Services

 

Pierce County Project CRP 5757 9th Street East, between 190th Avenue East and 198th Street East Pierce County, Washington

 

for

 

Pierce County Public Works and Utilities

 

May 31, 2013

 

       

1101 South Fawcett Avenue, Suite 200 Tacoma, Washington 98402 253.383.4940

Table of Contents INTRODUCTION AND PROJECT UNDERSTANDING ................................................................................... 1  SCOPE OF SERVICES ................................................................................................................................. 1  SURFACE CONDITIONS .............................................................................................................................. 2 

Geology ................................................................................................................................................... 3  FIELD EXPLORATIONS AND LABORATORY TESTING ............................................................................... 4 

Field Explorations ................................................................................................................................... 4  Laboratory Testing ................................................................................................................................. 4  Subsurface Conditions .......................................................................................................................... 4  Soil ................................................................................................................................................... 4  Groundwater .................................................................................................................................... 4  CONCLUSIONS AND RECOMMENDATIONS .............................................................................................. 5 

General ................................................................................................................................................... 5  Earthwork and Fill Placement ............................................................................................................... 5  General ............................................................................................................................................ 5  Subgrade Preparation ..................................................................................................................... 5  Fill Placement and Compaction ..................................................................................................... 5  Fill on Slopes ................................................................................................................................... 6  Fill Materials .................................................................................................................................... 6  Erosion Control ....................................................................................................................................... 6  Temporary and Permanent Slopes ....................................................................................................... 7  General ............................................................................................................................................ 7  Temporary Cut Slopes ..................................................................................................................... 7  Permanent Cut Slopes .................................................................................................................... 8  Retaining Systems ................................................................................................................................. 9  General ............................................................................................................................................ 9  Cast-in-Place Concrete Retaining Walls ....................................................................................... 10  Soldier Pile Wall............................................................................................................................. 11  Rockery Wall .................................................................................................................................. 12  Pavement Design Parameters ............................................................................................................ 13  Stormwater Vault ................................................................................................................................. 13  General .......................................................................................................................................... 13  Foundation Bearing Surface Preparation .................................................................................... 13  Bearing Capacity ........................................................................................................................... 14  Lateral Earth Pressures ................................................................................................................ 14  Lateral Resistance ........................................................................................................................ 14  Dewatering ........................................................................................................................................... 14  LIMITATIONS ........................................................................................................................................... 14 

 

May 31, 2013 | Page i File No. 0497-130-00

LIST OF FIGURES

Figure 1. Vicinity Map Figure 2. Site Plan APPENDICES

Appendix A. Test Pit Logs and Test Pit Location Map, Bowman Lake Plat Geotechnical Study, July 2000, Earth Consultants Appendix B. Field Explorations and Laboratory Testing Figure B-1. Key to Exploration Logs Figures B-2 through B-4. Log of Borings Figures B-5 and B-6. Sieve Analysis Results Appendix C. Stability Analysis Figures C-1 through C-19. SLOPE/W Analysis Appendix D. Report Limitations and Guidelines for Use

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

INTRODUCTION AND PROJECT UNDERSTANDING This revised report presents the result of our geotechnical engineering services for the proposed improvements to 9th Street East between 190th Avenue East and 198th Street East. Draft reports for this project were submitted on March 7, 2013 and April 8, 2013. Additional scope items were added by Pierce County after each draft report was reviewed. These additional scope items are incorporated into this final report. The approximate location of the project site is shown in Figure 1. Our understanding of the project is based on information provided by you, recent site visits and a previous study we performed at and near the subject site. Our previous study was conducted in September 1994 and consisted of a preliminary geotechnical evaluation for a section of 9th Street East, which included the site. The project at that time was titled the North Lake Tapps Access Project. Our report was preliminary in nature and provided general geotechnical recommendations. Our services for this project have been performed in general accordance with our proposal dated August 13, 2012 with additional scope items verbally authorized by Pierce County on March 21, 2013. We received initial authorization on October 2, 2012. We understand that you are considering improving and realigning about 1,000 linear feet of the existing roadway. The existing roadway traverses the sides and top of a low ridge at the site. A sharp curve is located near the top of the ridge. We understand that the project goals include increasing the radius of the curve and reducing the gradient of the roadway. This will be accomplished by cutting the ridge top and hillside by up to 25 feet and moving the centerline of the curve to the north as shown in the Site Plan, Figure 2. We understand that permanent cut slopes and/or a combination of permanent slopes with low retaining walls are being considered to accomplish the planned regrading. The roadway will also be widened to include 6-foot-wide paved shoulders. A below-grade stormwater detention vault is also planned for the western part of the realigned roadway

SCOPE OF SERVICES The list below presents the scope of services completed for the project. 1. Coordinate with Pierce County regarding the scope and schedule for the project. 2. Mobilize to the site to identify three borehole locations. Notify the “One-Call” utility locating service to check the proposed drilling areas for presence of subsurface utilities. 3. Review readily available published geologic and geotechnical information that includes the project site. This includes our previously completed preliminary geotechnical report, dated September 15, 1994. 4. Perform a geologic reconnaissance of the site. 5. Subcontract traffic control services for the site explorations. developed by the subcontracted traffic control company.

A traffic control plan was

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6. Obtain street use permits from Pierce County for the exploration at the site. 7. Perform subsurface exploration by advancing three drilled borings using a truck-mounted drill rig. Soil samples were collected at approximate 5-foot-depth intervals during drilling. 8. Submit six soil samples for laboratory testing. Our laboratory program included grain-size distribution tests and one California Bearing Ratio (CBR) test. 9. Develop an opinion regarding the composition and condition of the existing roadway subgrade. 10. Provide an interpreted soil resilient modulus (Mr) value based on the CBR test result. 11. Evaluate the proposed improvements with respect to the geologic/subsurface data. 12. Evaluate stability of existing and proposed slopes at three locations within the alignment using the computer program SLOPE/W. The evaluations were based on the subsurface data and soil properties developed from our field and laboratory programs and our experience. This scope item was not a part of our August 13, 2012 proposal and was added by Pierce County on March 21, 2013. 13. Provide an opinion regarding whether proposed slope geometries will result in an acceptable Factor of Safety (FS) against slope instability and whether shallower slopes with low retaining walls should be used. 14. Provide an opinion regarding suitable retaining wall systems for the site with respect to the proposed project and provide preliminary geotechnical recommendations for design. 15. Evaluate the suitability of using short (4 feet high or less) rockery walls at the base of the proposed cut slopes. Comment on the constructability of the rockery walls. 16. Develop earthwork recommendations for the proposed improvements. We provide recommendations for site preparation and grading, including temporary and permanent slopes, and fill placement criteria. We also discuss suitability of on-site soils for fill and subgrade preparation. 17. Provide geotechnical recommendations for a proposed detention vault to be located in the western portion of the site. This includes recommended allowable bearing capacity and lateral earth pressures. We also discuss groundwater elevation and potential impact including need for temporary dewatering.

SURFACE CONDITIONS The project site is located within a glacial upland area just north of Lake Tapps in Pierce County, Washington. Topography in this area is typified by northwest-southeast oriented ridges with narrow, valley areas between the ridges. We interpret the topography to represent relic ice-contact features that were formed at the base of the advancing Vashon glacial ice sheet. The low valley areas between the ridges in the site vicinity generally contain surface water. Bowman Lake, north of the site and Hille Lake, west of the site, are such areas. The project site comprises a section of 9th Street East that crosses over one of the northwest-southeast oriented ridges. At the site, 9th Street East is a narrow, two-lane roadway surfaced with asphalt concrete. Shallow drainage ditches border the east and north sides of the roadway. Roadway shoulders, where

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

present, are narrow and surfaced with gravel or native soils. The pavement at the site appears to be in good condition based on visual evaluation at the time of our geologic reconnaissance. We did not perform a detailed condition survey of existing pavement. The west part of the project site contains a section of 9th Street East that traverses the side-hill of the ridge. This portion of roadway has a side-hill cut on the east side and a side-hill fill on the west side of the two-lane roadway. The cut slope above this segment of the road is inclined at up to about 65 percent. We understand that part of the hillside was graded by Pierce County to provide borrow for CRP 5623, which was completed in 2005. This area is shaded in Figure 2. The remainder of the roadway, which is part of this project, appears to be at or near surrounding grades. A vacant area is located north of 9th Street East immediately to the southeast of the area previously graded by Pierce County. A soil-surfaced vehicle pullout area is located at the top of the ridge at this location. A primitive trail traverses the slope on the west side of the ridge in this location. Vegetation in the project area typically comprises a moderate to thick covering of brush and fir trees. The vacant area is vegetated with scattered grasses and scotch broom. The previous borrow area is covered with grasses and some scotch broom. We understand that localized pockets of groundwater seepage were encountered during the previous grading work and quarry spalls were placed in these locations to limit erosion. We observed quarry spalls beneath the covering of grass in portions of this area. We did not observe evidence of slope instability during our site visits. We also did not observe evidence of groundwater seepage in sloped portions of the site. Residential properties within the Bowman Lake Estates development border the project area to the east and north, as shown in Figure 2. Vacant and wooded property borders the roadway to the south and west.

Geology Geologic conditions at the site were evaluated by reviewing “Surficial Geology and Geomorphology of the Lake Tapps Quadrangle, Washington 1963.” The geologic unit mapped at and near the site comprises Vashon glacial till (map unit Qgt). Vashon till typically consists of a dense to very dense mixture of silt, sand, gravel and occasional cobbles and boulders. This material was deposited at the bottom of the advancing Vashon glacial ice sheet and was densified by the weight of the ice. We also reviewed test pit logs contained in a July 18, 2000 report completed by Earth Consultants titled “Geotechnical Engineering Study, Proposed Bowman Lake Development, Pierce County, Washington” Thirty-three test pits were completed for this project. Interpreted test pit locations near the site are shown in Figure 2. Copies of the test pits logs and location map from the 2000 report are contained in Appendix A. Glacial till soils were generally encountered at shallow depths in the nearby test pits completed for the 2000 geotechnical report.

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FIELD EXPLORATIONS AND LABORATORY TESTING Field Explorations Soil and groundwater conditions at the site were evaluated by observing the advancement of three drilled borings (B-1 through B-3) on January 2, 2013. Details of the field exploration program and logs of the explorations are presented in Appendix B. The approximate locations of the subsurface explorations are indicated in Figure 2.

Laboratory Testing Soil samples were obtained during drilling and taken to GeoEngineers’ laboratory for further evaluation. Selected samples were tested for moisture content and grain-size distribution (sieve analysis). A CBR test was completed on a composite sample of drill cuttings from the upper portions of the three exploratory borings. The result of the CBR test is presented in a later section of this report. Descriptions of the laboratory testing and the grain-size distribution test results are presented in Appendix B.

Subsurface Conditions Soil

One of the borings (B-2) was drilled in the vacant area near the top of the ridge. Borings B-1 and B-3 were drilled in paved areas within the existing roadway travel lanes. Boring B-2 was drilled to a depth of 30.5 feet. Borings B-1 and B-3 were drilled to depths of 16.5 feet each. Surfacing materials encountered in borings B-1 and B-3 comprised a thick section of asphaltic concrete pavement (9 to 9.5 inches) over about 3 to 4 inches of base course material. In B-1 medium dense fill (silty sand with gravel) was then encountered to a depth of 9.5 feet, where we encountered very dense glacial till soils. In B-3 loose fill (silty sand with gravel) was encountered to about 7.5 feet overlying very dense glacial till. Loose silty sand with gravel, which we interpret to be weathered glacial till soil, was encountered to a depth of about 8.5 feet in boring B-2. Very dense glacial till was then encountered to the full depth explored (30.5 feet) in this boring. The pavement subgrades in the project area likely consist of either native glacial till soils or fill materials derived from the glacial till soils. The subgrades encountered in borings B-2 and B-3 comprised fill and were in a loose to medium dense condition. Groundwater

Groundwater was not observed during drilling in any of our borings to the depths explored. Based on our experience, perched seasonal groundwater can occur within the glacial till, and also within fill soil placed on top of glacial till. We understand that localized groundwater seepage was encountered during excavation activities at the site in 2005. Groundwater of this nature typically occurs where there are pockets of relatively permeable soil within the very dense and typically low permeability glacial till materials. In our opinion isolated pockets of groundwater seepage should be anticipated in soil cuts for this project.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the site is generally suitable for the planned improvements. We anticipate soils along the alignment should consist of fill over Vashon glacial till. The fill and native soils contain a moderate to high proportion of fines. These materials are moisture sensitive and generally are difficult to work and compact during wet weather conditions. Because of this, we recommend that earthwork for the project be performed during periods of dry weather whenever possible. Our specific geotechnical recommendations are detailed below.

Earthwork and Fill Placement General

We recommend that the existing pavement, vegetation, topsoil, organics and otherwise unsuitable materials within the proposed project area be stripped and disposed of off site. Significant excavations into glacial till soils are anticipated for this project. We anticipate that cobbles and boulders will be encountered in the proposed excavations, based on our experience in similar geologic conditions. Boulders encountered in subgrade area excavations must be overexcavated and removed from the site. The overexcavation must be backfilled with structural fill placed and compacted in accordance with the recommendations in this report. We anticipate that the proposed roadway subgrade will be cut down as necessary to establish proposed roadway and wall subgrades. Cut material may be considered for use as structural fill provided the material can be properly moisture conditioned, any oversize particles are removed, and the material is placed and worked during extended periods of dry weather. Subgrade Preparation

Roadway, retaining wall, stormwater vault and fill subgrades must be thoroughly compacted with heavy, smooth-drum vibratory equipment prior to placement of fill or concrete. We recommend that prepared subgrades be observed by a member of our firm who will evaluate the suitability of the subgrade and identify areas of yielding subgrades, which are indicative of soft or loose soil. We recommend that these areas be scarified (e.g., with a ripper or a farmer’s disc), aerated and recompacted or the unsuitable soils be removed and replaced with structural fill. Fill Placement and Compaction

Fill soils must be compacted at a moisture content near optimum. The optimum moisture content varies with the soil gradation and must be evaluated during construction. Soils with a fines content over about 5 to 6 percent may be difficult or impossible to work or adequately compact during persistent wet weather conditions. We recommend that all fill placed at the site be compacted to at least 95 percent of the maximum dry density (MDD) as determined by ASTM International (ASTM) Test Method D 1557.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

Structural fill must be placed in uniform, horizontal lifts and uniformly densified with vibratory compaction equipment. The maximum lift thickness will vary depending on the material and compaction equipment used, but must generally not exceed 10 inches in thickness. Fill on Slopes

Fill placement on slopes is anticipated for the western portion of the project, based on the project plans. We recommend that fills placed on slopes steeper than 5H:1V (horizontal:vertical) be benched into the slope face and include keyways. In this manner, the transition zone between the new fill and native ground on a slope can be compacted by working from a horizontal fill surface. The configuration of the bench and keyway depends on the equipment being used. Bench excavations should be level and extend into the native slope face. We recommend that a vertical cut of about 3 feet be maintained for benched excavations. Keyways should be about 1-1/2 times the width of the equipment used for grading or compaction. Erosion control measures as discussed below should be implemented. Fill Materials ON-SITE SOILS

The on-site fills and native glacial till soils appear to contain a moderate to high percentage of fines and are extremely moisture sensitive. These soils can be extremely difficult to work and compact even during dry weather conditions and will likely not be suitable for use as structural fill when wet or if earthwork is performed in wet weather. The on-site soils can be considered for use as structural fill provided oversize particles (greater than 6 inches in dimension) are removed and the material is moisture conditioned so that it can be placed and compacted as recommended in this report. IMPORTED MATERIALS

We recommend that imported fill must consist of well-graded sand and gravel or crushed rock with a maximum particle size of 6 inches and less than 5 percent fines by weight based on the minus ¾-inch fraction. Organic matter, debris or other deleterious material must not be present. In our opinion, material conforming to Washington State Department of Transportation (WSDOT) Standard Specifications 9-03.9 (Aggregates for Ballast and Crushed Surfacing), 9-03.10 (Aggregate for Gravel Base) and 9-03.14(1) (Gravel Borrow) is suitable for use as imported fill material during wet weather, with the exception that the fines content must be 5 percent or less based on the minus ¾-inch fraction. If prolonged dry weather prevails during the earthwork phase of construction, somewhat higher fines content may be acceptable.

Erosion Control Weathering, erosion and the resulting surficial sloughing and shallow land sliding are natural processes. To reduce and slow these natural processes, we recommend the following be implemented during construction:

■ No discharge of concentrated surface water or significant sheet flow onto temporary or permanent slopes.

■ Collect groundwater seepage if encountered during construction, and discharge at appropriate off-site locations.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

■ Provide temporary erosion control during construction. ■ Provide permanent erosion control following construction. Temporary erosion control must be provided during construction activities and maintained until permanent erosion control measures are functional. Surface water runoff must be properly contained and channeled using drainage ditches, berms, swales, temporary ponds and/or siltation fences. Construction techniques that reduce disturbance and removal of vegetation are recommended. Disturbed sloped areas must be protected with a temporary covering until new vegetation can be established. Jute or coconut fiber matting, excelsior matting or clear plastic sheeting is suitable for this purpose. Permanent measures for erosion control include reseeding or replanting the disturbed areas as soon as possible and protecting those areas until new vegetation has been established. The removal of natural vegetation should be minimized and limited to active construction areas. Permanent site grading must be accomplished in such a manner that stormwater runoff is not concentrated and not directed to sloped areas. Catch basins and tightlines should be used where necessary to direct storm or other surface water across sloped areas. Surface water and drainage from impervious surfaces must be directed to appropriate stormwater disposal facilities.

Temporary and Permanent Slopes General

We understand that a permanent soil cut, ranging up to about 25 feet in depth and approximately 800 feet in length, is planned to construct the roadway. Our understanding is based on a review of preliminary project plans prepared by Pierce County and dated July 2012. We understand that the maximum cut depth will occur between about Station 58+00 and Station 59+00, at the approximate center of the overall soil cut. We anticipate that the cut material will comprise Vashon glacial till, based on the borings completed at the site. The approximate anticipated limit of the proposed cut is shown in in Figure 2. We also reviewed proposed cut slope geometries at various stations throughout the project. This information was provided to us on March 21, 2013. Proposed cut slope geometries of between 1.6H:1V and 1.75H:1V are indicated on the plan sheets. We selected three station locations (57+00, 55+00 and 53+00) and completed stability analyses of existing and proposed slope geometries. The results of our analyses are presented in a subsequent section of this report. Our specific geotechnical recommendations for temporary and permanent cut slopes at the site are presented in the following sections. Temporary Cut Slopes

Temporary cut slopes will be necessary during grading, retaining wall construction and utility installation. The contractor is responsible for construction site safety and must monitor slopes during earthwork in accordance with applicable Washington Industrial Safety and Health Administration (WISHA) regulations.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

In our opinion, the soil encountered in our explorations generally classifies as Type C as described in Washington Administrative Code (WAC) 296-155 Part N. Temporary slopes above groundwater in Type C soils may be inclined at 1.5H:1V or flatter. This recommendation assumes that all surface loads are kept a minimum distance of at least half the depth of the cut away from the top of the slope. Flatter slopes will be necessary if surface loads are imposed above the cuts a distance equal to or less than one-half the depth of the cut. Permanent Cut Slopes GENERAL

We understand that, because of property boundary limitations, permanent slope inclinations ranging from 1:75H:1V to possibly 1.6H:1V could be required to complete the roadway cut as envisioned. This is based on our review of the preliminary plan sheets provided by Pierce County, which include sheets containing proposed cut slope profiles provided on March 21, 2013. The tallest cut slope in the project area would be about 25 feet in vertical height according to the plans. We understand that Pierce County typically installs a bench or benches on permanent cut slopes greater than 15 feet in vertical height. The purpose of the bench(es) is to reduce the potential for erosion and instability. We understand that including a mid-slope bench at the site may not be possible due to right-of-way width restrictions. SLOPE STABILITY ANALYSES

We evaluated existing and proposed slope inclinations at three station locations (57+00, 55+00 and 53+00) along the proposed alignment. We used the computer program SLOPE/W (GEO-SLOPE International, Ltd., 2012) to numerically evaluate stability of cross sections at each of the above station locations. We selected soil parameters for our analysis based on the results of our recent borings completed in this area, our interpretation of geologic conditions at the site and a review of test pit logs contained in the July 18, 2000 geotechnical report for the Bowman Lake Estates. The interpreted location of nearby test pits from this study are included in Figure 2 and the test pit logs are contained in Appendix A. SLOPE/W evaluates the stability of numerous trial shear surfaces using a vertical slice limitequilibrium method. The program then identifies the shear surface with the lowest Factor of Safety (FS). We evaluated four general conditions for each cross section. First, we evaluated the existing slope conditions. We then evaluated the proposed cut slopes assuming both a 1.75H:1V cut slope and a 1.6H:1V cut slope. Section A-A’ was also evaluated assuming a 1.75H:1V cut slope with a small rockery at the toe. The results of our analysis are shown in Appendix C. In general, permanent cut slope inclinations of 1.6H 1V and 1.75H:1V appear to be stable relative to both deep-seated and shallow surficial slope movement, based on the analyses. The WSDOT Geotechnical Design Manual (WSDOT GDM) recommends that permanent cut slopes be designed to have a minimum FS of 1.25 against general slope movement. For slope movement that would impact a large structure such as a bridge pier, the WSDOT GDM recommends an FS greater than 1.5.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

Based on our analyses all of the proposed slope configurations have calculated safety factors greater than the minimum recommended FS of 1.25. Additionally, for deep slope movements that would mobilize a larger soil mass extending further upslope, all proposed slope configurations exceed the recommended 1.5 FS to protect structures Based on the results of our analyses, it is our opinion that roadway construction, as envisioned, should not destabilize structures upslope (east and north) of the proposed construction provided that cut slopes are inclined at or less than maximum recommended cut slope inclination of 1.6H:1V, and that the other recommendations provided in this report are followed. In western Washington, erosion and minor shallow surface sloughs are possible on newly constructed slopes inclined at 1.75H:1V or steeper. Surface sloughs could extend over a large area, but are typically limited to 12 to 24 inches in depth. The potential for erosion and surface sloughing is reduced once a full and thick vegetative cover is established. We recommend that erosion control be established on the cut slopes soon after the slopes are completed. This may consist of tacked-on geotextiles, which can promote vegetation growth on the slopes. Performing the earthwork in periods of extended dry weather will also assist in reducing the potential for erosion during construction. SEEPAGE CONTROL

We anticipate that pockets of groundwater seepage could be encountered as the slopes are excavated. This is relatively common when excavating cut slopes in compact glacial till soils. These localized areas of groundwater seepage typically “dry up” soon after the cut slope is completed as the water stored within the permeable areas drains out. However, it is possible that areas of wet soil will persist and continue to seep. We recommend that areas of persistent wet soil be repaired by placing at least 6 inches of sand and gravel filter blanket material topped with about 6 inches of quarry spalls. The purpose of the sand and gravel filter is to help control against piping and loss of native soil materials on the slope, which could lead to surficial slope failure if not controlled. Some overexcavation of the existing soils will be necessary to install the sand and gravel filter and quarry spalls. In larger areas where persistent water seepage is present, we recommend that lateral drains be installed. Each lateral drain should consist of a perforated pipe installed parallel to the slope within a trench excavated beneath the seep into the underlying relatively impermeable glacially consolidated soil. A perforated pipe is placed near the base of the trench. The trench must be backfilled with gravel that extends into the seep area. The downslope side of the trench must be lined with an impermeable plastic liner. The perforated pipe must be connected to an appropriate discharge point, such as to the storm pipes beneath the roadway.

Retaining Systems General

We understand that retaining wall systems are not desired as a part of this project. However, low “stub” retaining walls may be used along the base of the slope in order to maintain a minimum 1.75H:1V slope inclination.

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

If used, we anticipate that the stub walls would be limited in lateral extent and would be about 5 feet or less in vertical height. Either cast-in-place concrete and/or soldier pile wall systems are suitable for this purpose. We understand that you are also considering rockery walls for this application. We provide a summary of each system, with respect to the interpreted geologic conditions, in the following sections. Cast-in-Place Concrete Retaining Walls GENERAL

A near-vertical temporary cut slope will be necessary to construct cast-in-place concrete walls at the site. We anticipate that the wall foundations would bear on very dense glacial till soils and would retain similar materials. We recommend that foundation bearing surfaces be comprised of either dense to very dense glacially consolidated materials or structural fill, which extends to the dense to very dense native soils. If loose existing fill is encountered in the excavation base it must be overexcavated to firm soil and replaced with compacted structural fill. Foundation bearing surfaces must not be exposed to standing water. Should water infiltrate and pool in the excavation, it must be removed before placing structural fill or reinforcing steel. BEARING CAPACITY

We recommend that an allowable soil bearing pressure of 3,500 pounds per square foot (psf) be used for design of the cast-in-place walls, if they are used. The recommended bearing pressure may be applied to the total of dead and long-term live loads and may be increased by one-third when considering total loads, including earthquake or wind loads. This is a net bearing pressure, the weight of the footing and overlying fill can be ignored in calculating footing sizes. We estimate that post-construction settlement of footings founded as recommended above should be less than 1 inch with differential settlement of less than ½ inch. We expect that most of the estimated footing settlements will occur as loads are applied. LATERAL SOIL PRESSURES

The lateral soil pressures acting on cast-in-place retaining walls depends on the nature, density and configuration of the soil behind the wall and the amount of lateral wall movement, which can occur as backfill is placed. For walls that are free to yield at the top at least one-thousandth of the height of the wall, soil pressures will be less than if movement is limited by such factors as wall stiffness or bracing. Assuming that the walls are backfilled and drained as outlined in the following paragraphs, we recommend that yielding walls supporting horizontal backfill be designed using an equivalent fluid density of 35 pounds per cubic foot (pcf) (triangular distribution). For a 1.75H:1V back-slope, we recommend an equivalent fluid density of 55 pcf to calculate active pressures acting on the wall. For earthquake loading conditions, we recommend a rectangular pressure equal to 7H, where H is the exposed height of the retaining wall, to be added in the design. LATERAL RESISTANCE

Lateral wall foundation loads can be resisted by passive resistance on the sides of the wall footings and by friction on the base of the footings. Passive resistance may be evaluated using an equivalent fluid density of 300 pcf where footings are poured neat against native soil or cement

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9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

treated structural fill compacted to at least 95 percent of MDD per ASTM D 1557. Resistance to passive pressure should be calculated from the bottom of adjacent paving. Frictional resistance can be evaluated using 0.35 for the coefficient of base friction against footings. The above values incorporate an FS of about 1.5. DRAINAGE

Positive drainage must be provided behind the cast-in-place retaining walls by placing a 12-inchwide zone of gravel borrow behind the walls, with a nonwoven geotextile filter fabric between the gravel borrow and the wall backfill. We recommend the nonwoven geotextile filter fabric consist of Mirafi™ 140N, or approved equivalent, and be wrapped to protect the top and bottom of the gravel borrow. Approximately 12 inches of on-site silty soil should be placed above the zone of gravel borrow to reduce the surface water infiltration behind the wall. A perforated drain pipe with a minimum diameter of 4 inches must be placed at the bottom of the zone of gravel borrow. We recommend using either heavy-wall solid pipe (SDR-35 PVC) or rigid corrugated polyethylene pipe (ADS N-12, or equivalent) for the collector pipe. We recommend against using flexible tubing for wall drain pipe. The pipe must be laid with a minimum slope of ½ percent and discharge to a suitable on-site disposal location. The pipe installations must include cleanouts to allow for future maintenance. The drain pipe may be routed to a suitable disposal point or be allowed to exit through a series of weep holes if the area in front of the wall is unpaved. Soldier Pile Wall

Soldier pile walls include vertical steel H piles spaced about 5 to 10 feet on-center. The pile spacing is dependent on the proposed wall height and on the retained soil material. The piles are installed by drilling holes to the design depths, setting the pile into the hole and backfilling the annular space with concrete. The embedment depth required for the piles depends on the design loads which in turn depend on the height of the wall and the soil materials retained. The soldier pile holes are usually drilled with solid flight auger. We anticipate that the soils (glacial till) in the proposed soldier pile wall area could contain cobbles and boulders. The contractor must be prepared for these conditions and provide appropriate equipment, means and methods to advance the soldier pile holes should cobbles and boulders be encountered. For preliminary purposes at the project site, we recommend that the embedded portion of the soldier piles be at least 2 feet in diameter and extend a minimum distance of 10 feet below the base of the roadway excavation to resist “kick-out.” The axial capacity of the soldier piles must resist the downward component of the anchor loads, if tieback anchors are used, and other vertical loads, as appropriate. We recommend using an allowable end-bearing value of 30 ksf for piles supported on dense to very dense glacial till soils. The allowable end bearing value should be applied to the base area of the drilled hole into which the soldier pile is concreted. This value includes an FS of about 2.5. The allowable end bearing capacity assumes that the shaft bottom is cleaned out immediately prior to concrete placement. If necessary, an allowable pile skin friction of 1½ ksf may be used on the embedded portion of the soldier piles to resist the vertical loads.

May 31, 2013 | Page 11 File No. 0497-130-00

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

The spaces between the piles are protected with lagging. Lagging is typically either treated timbers or precast concrete panels. If timber is used, it must be adequately treated for protection against water and decay. For concrete lagging, it is important that the contractor accurately place and plumb the soldier piles to facilitate installation of the precast concrete lagging. Lagging is typically designed in accordance with the requirements of Section 5.4.3 of the Federal Highway Administration’s (FHA) Geotechnical Engineering Circular No. 4. Tiebacks are commonly used in soldier pile walls to provide supplemental lateral support in taller sections of the wall. Tiebacks will likely be required, in our opinion, if a soldier pile wall is used to retain the full anticipated soil cut height (25 feet). Tieback anchors are designed to extend far enough behind the wall to develop anchorage within stable soil materials beyond a “no-load” zone. The “no-load” zone is typically defined by extending a horizontal line back from the base of the wall for a distance equal to 1/4 H, where H is the height of wall, and then upward at a 60 degree angle to the ground surface behind and above the wall. Tieback anchors are typically inclined downward at 15 to 25 degrees below the horizontal. Rockery Wall GENERAL

We understand that, if constructed, the rockery walls would be a maximum height of about 4 feet. We completed slope stability analyses of a 4-foot high rockery wall at the base of the 1.75H:1V slope (Station 57+00). We calculate a minimum FS of 1.59 for this slope configuration using the criteria discussed in the “Slope Stability” section of this report. A near-vertical temporary cut slope will be necessary to construct rockery walls at the site. We anticipate that the rockery wall foundations would bear on very dense glacial till soils and would retain similar materials. We recommend that foundation bearing surfaces be comprised of either dense to very dense glacially consolidated materials or structural fill, which extends to the dense to very dense native soils. If loose existing fill is encountered in the excavation base it must be overexcavated to firm soil and replaced with compacted structural fill. DISCUSSION

Rockeries generally act as gravity walls that offer limited resistance to lateral loads. Important elements of a rockery are: 1) its size, weight and shape, 2) friction developed between individual rocks (internal friction), 3) friction between the base layer of rocks and the underlying ground, 4) passive resistance to sliding developed by soil or pavement in front of the rockery, and 5) lateral load acting on or resisted by the rockery. Internal friction is not easily quantified and is, in part, dependent on the rock strength at the contact and, to a large degree, on the skill and judgment of the rockery builder. Internal friction will change over time, due to weathering of the rock and from rockery movement. Rockeries typically experience a “settling in” during and for some time after construction. Also, many rockeries are subject to additional lateral load that causes additional movement due to wetting of the retained soil or other factors that reduce the strength of the soil. For poorly constructed rockeries, movement can result in loss of internal friction and a rockery failure.

Page 12 | May 31, 2013 | GeoEngineers, Inc. File No. 0497-130-00

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

Rockery construction is an art and depends largely on the skill of the builder. Although rockeries can offer some lateral restraint, they are partially indeterminate and they present increased risk relative to other retaining structures, such as cantilever concrete walls and soldier pile walls. Even when the rockery is properly constructed, there is risk of future movement and failure. We recommend that a wall design detail and specifications be completed if a rockery wall is chosen to retain short cut slopes at the site. The design must include recommendations for materials and drainage considerations, design details and guidelines for rockery wall construction.

Pavement Design Parameters We understand that Pierce County will complete the pavement section design for the project. We completed a CBR test of a composite sample of material collected from the borings. Based on the laboratory results, it is our opinion that a CBR value of 15 appropriately characterizes the anticipated subgrade conditions. Based on correlations between CBR and Mr, it is our further opinion that a resilient modulus of 22,500 pound per square inch (psi) may be assumed for the native subgrade material for pavement design purposes.

Stormwater Vault General

A concrete stormwater vault is planned for the west end of the proposed roadway segment. The planned vault is to be about 165 feet long and about 20 feet wide and 7 feet deep. The vault will be located beneath the south-bound traffic lane in the approximate location shown in Figure 2. We understand that the vault bottom will be flat. Therefore, the amount of fill over the vault will increase to the south, as road grades increase. The depth of fill material is unknown as the proposed vault bottom elevation was not included in the preliminary project plans. Our recommendations for footing design are presented in the following sections. Foundation Bearing Surface Preparation

Fill was encountered in Boring B-1 to a depth of about 9.5 feet. Accordingly, we anticipate that the vault could be founded on a combination of fill and native glacial till soils. Seasonal perched groundwater could be encountered near the fill/till contact, particularly if the work is performed during the wetter winter months or immediately after periods of heavy rain. We recommend that foundation bearing surfaces be comprised of either dense to very dense glacial consolidated materials or structural fill, which extends to the dense to very dense native soils. If loose existing fill is encountered in the excavation base it must be overexcavated to firm soil and replaced with compacted structural fill. Foundation bearing surfaces must not be exposed to standing water. Should water infiltrate and pool in the excavation, it must be removed before placing structural fill or reinforcing steel. A relatively large excavation will be required to construct the stormwater vault. We recommend that the excavation and temporary slopes used be completed in accordance with the “Temporary Cut Slopes” section of this report.

May 31, 2013 | Page 13 File No. 0497-130-00

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

Bearing Capacity

We recommend that an allowable soil bearing pressure of 3,500 psf be used for design of the stormwater vault. The recommended bearing pressure should be applied to the total of dead and long-term live loads and may be increased by one-third when considering total loads, including earthquake or wind loads. This is a net bearing pressure, the weight of the footing and overlying fill can be ignored in calculating footing sizes. We estimate that post-construction settlement of footings founded as recommended above should be less than 1 inch with differential settlement of less than ½ inch. We expect that most of the estimated footing settlements will occur as loads are applied. Lateral Earth Pressures

We recommend subsurface vault walls with a level backfill be designed using lateral earth pressures corresponding to an equivalent fluid density of 35 pcf for drained conditions. For the undrained condition, we recommend walls with a level backfill be designed using lateral earth pressures corresponding to an equivalent fluid density of 20 pcf plus hydrostatic pressure. The recommended pressures do not include the effects of surcharges from surface loads. Appropriate factors of safety should be applied to these values with respect to bearing capacity, sliding and overturning. If vehicles will be operated to within one-half the height of the wall, a traffic surcharge should be added to the wall pressure. The traffic surcharge can be approximated by the equivalent weight of an additional 2 feet of backfill behind the wall. Lateral Resistance

Lateral loads can be resisted by passive resistance on the sides of the footings and by friction on the base of the footings. Passive resistance should be evaluated using an equivalent fluid density of 300 pcf. For footings and slabs founded in accordance with the recommendations presented above, the allowable frictional resistance may be computed using a coefficient of friction of 0.35 applied to vertical dead-load forces. The recommended lateral resistance value includes an FS of approximately 1.5.

Dewatering Construction of subsurface elements of the project, such as utilities and the stormwater vault, may require dewatering. The effort required to dewater the temporary excavations should be less if construction occurs during the summer and early fall months. If dewatering is needed in the glacial till materials, it can likely be accomplished using sumps. The contractor selected for the construction of the subsurface structures should be responsible for design and installation of the temporary dewatering system.

LIMITATIONS We have prepared this report for the exclusive use of Pierce County and their authorized agents for the proposed intersection upgrade. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of

Page 14 | May 31, 2013 | GeoEngineers, Inc. File No. 0497-130-00

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Please refer to Appendix D titled “Report Limitations and Guidelines for Use” for additional information pertaining to use of this report.

May 31, 2013 | Page 15 File No. 0497-130-00

Map Revised: 07 March 2013

tkauhi

Site

Office: Tac

Path: P:\0\0497130\GIS\0497130_Fig1_Vicinity_9thStrEast.mxd

Lake Tapps

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2012

µ

Site 2,000

0

2,000

Feet

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap,

Vicinity Map Projection: WGS 1984 Web Mercator Auxiliary Sphere Notes: 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

Improvements, CRP 5757, 9th Street East Pierce County, Washington Figure 1

APPEENDIX A Testt Pit Logs and Test Pit Locatiion Map Bow wman Lak ke Plat Ge eotechnica al Study Jully 2000, E Earth Conssultants

APPENDIX B Field Exploratio ons and La aboratory Testing

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

APPENDIX B FIELD EXPLORATIONS AND LABORATORY TESTING Field Explorations Soil and groundwater conditions were explored by advancing three power borings at the site. The borings were completed by Holt Services on January 2, 2013. The borings were drilled to depths ranging from 16.5 to 30.5 feet. The exploration locations were established in the field by measuring from nearby roadway intersections or other nearby features shown on maps provided by Pierce County. Boring locations should be considered approximate and are shown on Figure 2. The borings were continuously monitored by our representative who maintained a log of subsurface conditions, visually classified the soils encountered and obtained soil samples during drilling. Soil samples were obtained from the borings using an SPT sampler driven up to 18 inches by a 140-pound hammer. The number of blows required to drive the sampler the last 12 inches, or other indicated distance, is recorded on the boring logs. The samples were collected in plastic bags and brought back to the GeoEngineers laboratory for review and analysis. Soils encountered were visually classified in general accordance with the classification system described in Figure B-1. A key to the boring log symbols is also presented in Figure B-1. The boring logs are presented in Figures B-2 through B-4. The logs are based on our interpretation of the field and laboratory data and indicate the various types of soils encountered. They also indicate the depths at which the soil characteristics change, although the change might actually be gradual. The soil densities noted on the boring logs are based on the number of blows required to drive the sampler. The ground surface elevations shown on the logs are based on topographic information provided by Pierce County and interpreted by us.

Laboratory Testing Soil samples obtained from the borings were brought to our laboratory to confirm field classifications. Selected samples were tested to determine their moisture content and grain-size distribution in general accordance with applicable ASTM International (ASTM) standards. The moisture content of selected samples was determined in general accordance with ASTM Test Method D 2216. The test results are presented in the respective boring logs. Grain-size distribution (sieve analyses) was conducted in general accordance with ASTM Test Method D 422. The results of the grain-size sieve analyses are presented in Figures B-5 and B-6.

 

May 31, 2013 | Page B-1 File No. 0497-130-00

SOIL CLASSIFICATION CHART MAJOR DIVISIONS

GRAVEL AND GRAVELLY SOILS COARSE GRAINED SOILS

MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE

GW

WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES

GP

POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES

GRAVELS WITH FINES

GM

SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES

(APPRECIABLE AMOUNT OF FINES)

GC

CLAYEY GRAVELS, GRAVEL SAND - CLAY MIXTURES

(LITTLE OR NO FINES)

SW

WELL-GRADED SANDS, GRAVELLY SANDS

SP

POORLY-GRADED SANDS, GRAVELLY SAND

SANDS WITH FINES

SM

SILTY SANDS, SAND - SILT MIXTURES

(APPRECIABLE AMOUNT OF FINES)

SC

CLAYEY SANDS, SAND - CLAY MIXTURES

ML

INORGANIC SILTS, ROCK FLOUR, CLAYEY SILTS WITH SLIGHT PLASTICITY

CL

INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS

OL

ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY

MH

INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS SILTY SOILS

CH

INORGANIC CLAYS OF HIGH PLASTICITY

OH

ORGANIC CLAYS AND SILTS OF MEDIUM TO HIGH PLASTICITY

PT

PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS

CLEAN SANDS MORE THAN 50% RETAINED ON NO. 200 SIEVE

SAND AND SANDY SOILS

SYMBOLS GRAPH LETTER

TYPICAL DESCRIPTIONS

SYMBOLS GRAPH LETTER

CLEAN GRAVELS

ADDITIONAL MATERIAL SYMBOLS

AC

Asphalt Concrete

CC

Cement Concrete

CR

Crushed Rock/ Quarry Spalls

TS

Topsoil/ Forest Duff/Sod

Groundwater Contact

(LITTLE OR NO FINES)

MORE THAN 50% OF COARSE FRACTION PASSING NO. 4 SIEVE

TYPICAL DESCRIPTIONS

Measured groundwater level in exploration, well, or piezometer Measured free product in well or piezometer

Graphic Log Contact

SILTS AND CLAYS

FINE GRAINED SOILS

LIQUID LIMIT LESS THAN 50

MORE THAN 50% PASSING NO. 200 SIEVE

SILTS AND CLAYS

LIQUID LIMIT GREATER THAN 50

HIGHLY ORGANIC SOILS

Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit

Material Description Contact Distinct contact between soil strata or geologic units Approximate location of soil strata change within a geologic soil unit

Laboratory / Field Tests

NOTE: Multiple symbols are used to indicate borderline or dual soil classifications

Sampler Symbol Descriptions 2.4-inch I.D. split barrel Standard Penetration Test (SPT) Shelby tube Piston Direct-Push Bulk or grab

Blowcount is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted). See exploration log for hammer weight and drop. A "P" indicates sampler pushed using the weight of the drill rig.

%F AL CA CP CS DS HA MC MD OC PM PI PP PPM SA TX UC VS

Percent fines Atterberg limits Chemical analysis Laboratory compaction test Consolidation test Direct shear Hydrometer analysis Moisture content Moisture content and dry density Organic content Permeability or hydraulic conductivity Plasticity index Pocket penetrometer Parts per million Sieve analysis Triaxial compression Unconfined compression Vane shear

Sheen Classification NS SS MS HS NT

No Visible Sheen Slight Sheen Moderate Sheen Heavy Sheen Not Tested

NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to be representative of subsurface conditions at other locations or times.

KEY TO EXPLORATION LOGS

FIGURE B-1

Start 1/2/2013

Drilled

End 1/2/2013

Surface Elevation (ft) Vertical Datum Easting (X) Northing (Y)

Total Depth (ft)

Logged By SMJ Checked By SWH

16.5

498

Hammer Data

14002.8 8876.7

System Datum

Drilling Hollow Stem Auger Method

Driller Holt Drilling

Autohammer

Drilling Equipment Groundwater Date Measured

Truck Mounted Depth to Water (ft)

Elevation (ft)

Not observed

Notes: At Station 53+00, approximately 10 feet south from centerline

0

AC

9.5 inches asphalt concrete

CR

4 inches base course Brown silty fine to coarse sand with gravel (medium dense, moist) (fill)

Dry Density, (pcf)

REMARKS

49

5

SM

Moisture Content, %

MATERIAL DESCRIPTION

Group Classification

Graphic Log

Water Level

Sample Name Testing

Collected Sample

Blows/foot

Recovered (in)

Interval

Depth (feet)

Elevation (feet)

FIELD DATA

7

10

1

12

61

2

13

95

3

12

49 0

5

SM

Light brown silty fine to coarse sand with gravel and cobbles (very dense, moist) (till)

12

48 5

10

Tacoma: Date:5/28/13 Path:P:\0\0497130\GINT\049713000.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD

15

Note: See Figure B-1 for explanation of symbols.

Log of Boring B-1 Project:

Improvements, CRP 5757, 9th Street East

Project Location:

Pierce County, Washington

Project Number:

0497-130-00

Figure B-2 Sheet 1 of 1

Start 1/2/2013

Drilled

End 1/2/2013

Surface Elevation (ft) Vertical Datum Easting (X) Northing (Y)

Total Depth (ft)

Logged By SMJ Checked By SWH

30.5

550

Hammer Data

14304.08 8534.19

System Datum

Drilling Hollow Stem Auger Method

Driller Holt Drilling

Autohammer

Drilling Equipment Groundwater Date Measured

Truck Mounted Depth to Water (ft)

Elevation (ft)

Not observed

Notes: At Station 57+60, approximately 10 feet south from centerline

54 5

0

5

7

9

SM

Brown silty fine to coarse sand with gravel (loose, moist) (weathered till)

1

54 0 53 5 53 0 52 5

25

97

2

18

81

3

18

79

4

5

62

5

5

50/3"

6

Light brown silty fine to coarse gravel with sand and cobbles (very dense, moist) (till)

6

0

20

52

Tacoma: Date:5/28/13 Path:P:\0\0497130\GINT\049713000.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD

15

9

REMARKS

12

GM 10

Dry Density, (pcf)

MATERIAL DESCRIPTION

Moisture Content, %

Group Classification

Graphic Log

Water Level

Sample Name Testing

Collected Sample

Blows/foot

Recovered (in)

Interval

Depth (feet)

Elevation (feet)

FIELD DATA

30

Note: See Figure B-1 for explanation of symbols.

Log of Boring B-2 Project:

Improvements, CRP 5757, 9th Street East

Project Location:

Pierce County, Washington

Project Number:

0497-130-00

Figure B-3 Sheet 1 of 1

Start 1/2/2013

Drilled

End 1/2/2013

Surface Elevation (ft) Vertical Datum Easting (X) Northing (Y)

Total Depth (ft)

Logged By SMJ Checked By SWH

16.5

528

Hammer Data

14631.67 8502.59

System Datum

Drilling Hollow Stem Auger Method

Driller Holt Drilling

Autohammer

Drilling Equipment Groundwater Date Measured

Truck Mounted Depth to Water (ft)

Elevation (ft)

Not observed

Notes: At Station 60+90, approximately 10 feet south from centerline

0

AC

9 inches asphalt concrete

CR

3 inches base course Brown silty fine to medium sand with gravel (loose, moist) (fill)

Dry Density, (pcf)

REMARKS

52

5

SM

Moisture Content, %

MATERIAL DESCRIPTION

Group Classification

Graphic Log

Water Level

Sample Name Testing

Collected Sample

Blows/foot

Recovered (in)

Interval

Depth (feet)

Elevation (feet)

FIELD DATA

5

7

4

1

52 0

SM

15

66

2

16

92

3

8

51 5

10

Light brown and orange staining silty fine to coarse sand with gravel (very dense, moist) (till)

Tacoma: Date:5/28/13 Path:P:\0\0497130\GINT\049713000.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARD

15

Note: See Figure B-1 for explanation of symbols.

Log of Boring B-3 Project:

Improvements, CRP 5757, 9th Street East

Project Location:

Pierce County, Washington

Project Number:

0497-130-00

Figure B-4 Sheet 1 of 1

0497-130-00

SWH:SAS:tt

U.S. STANDARD SIEVE SIZE 3”

1.5”

3/4”

3/8”

#4

#10

#20

#40

#60 #100

#200

100

PERCENT PASSING BY WEIGHT

90 80 70 60 50 40 30 20 10

FIGURE B-5

SIEVE ANALYSIS RESULTS

0 1000

100

10

1

0.1

0.01

GRAIN SIZE IN MILLIMETERS GRAVEL BOULDERS

SYMBOL

COBBLES

COARSE

SAND FINE

COARSE

MEDIUM

FINE

SILT OR CLAY

EXPLORATION NUMBER

DEPTH (ft)

MOISTURE (%)

SOIL CLASSIFICATION

B-1 B-1 B-2 B-2

5 10 5 15

12 12 12 6

Silty sand with gravel (SM) Silty sand with gravel (SM) Silty sand with gravel (SM) Silty gravel with sand (GM)

0.001

0497-130-00

SWH:SAS:tt

U.S. STANDARD SIEVE SIZE 3”

1.5”

3/4”

3/8”

#4

#10

#20

#40

#60 #100

#200

100

PERCENT PASSING BY WEIGHT

90 80 70 60 50 40 30 20 10

FIGURE B-6

SIEVE ANALYSIS RESULTS

0 1000

100

10

1

0.1

0.01

GRAIN SIZE IN MILLIMETERS GRAVEL BOULDERS

SYMBOL

COBBLES

COARSE

SAND FINE

COARSE

MEDIUM

FINE

SILT OR CLAY

EXPLORATION NUMBER

DEPTH (ft)

MOISTURE (%)

SOIL CLASSIFICATION

B-3

10

8

Silty sand with gravel (SM)

0.001

APPENDIX C S Stability A Analysis

0497-130-00

SLOPE/W Analysis, Section A-A’ Existing Condition Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-1

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.75H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-2

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.75H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-3

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.75H:1V with Wall; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-4

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.75H:1V Slope and Rockery; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-5

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.6H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-6

0497-130-00

SLOPE/W Analysis, Section A-A’ Proposed 1.6H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-7

0497-130-00

SLOPE/W Analysis, Section B-B’ Existing Conditions Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-8

0497-130-00

SLOPE/W Analysis, Section B-B’ Proposed 1.75H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-9

0497-130-00

SLOPE/W Analysis, Section B-B’ Proposed 1.75H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-10

0497-130-00

SLOPE/W Analysis, Section B-B’ Proposed 1.6H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-11

0497-130-00

SLOPE/W Analysis, Section B-B’ Proposed 1.6H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-12

0497-130-00

SLOPE/W Analysis, Section C-C’ Existing Conditions Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-13

0497-130-00

SLOPE/W Analysis, Section C-C’ Proposed 1.75H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-14

0497-130-00

SLOPE/W Analysis, Section C-C’ Proposed 1.75H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-15

0497-130-00

SLOPE/W Analysis, Section C-C’ Proposed 1.6H:1V Slope; Shallow Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-16

0497-130-00

SLOPE/W Analysis, Section C-C’ Proposed 1.6H:1V Slope; Deep Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-17

0497-130-00

SLOPE/W Analysis, Section C-C’ Existing Conditions Downhill Slope Movement Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-18

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SLOPE/W Analysis, Section C-C’ Proposed Downhill Slope Note: F.S. = Factor of Safety

Improvements, CRP 5757, 9th Street East Pierce County, Washington

Figure C-19

APPENDIX D Reportt Limitatio ons and G Guidelines for Use

9TH STREET EAST, BETWEEN 190TH AVENUE EAST AND 198TH STREET EAST „ Pierce County, Washington

APPENDIX D REPORT LIMITATIONS AND GUIDELINES FOR USE1 This appendix provides information to help you manage your risks with respect to the use of this report.

Geotechnical Services Are Performed For Specific Purposes, Persons and Projects This report has been prepared for the exclusive use of Pierce County and their authorized agents. This report is not intended for use by others, and the information contained herein is not applicable to other sites. GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted geotechnical practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated.

A Geotechnical Engineering or Geologic Report is Based on a Unique Set of ProjectSpecific Factors This report has been prepared for the planned improvements as a part of Pierce County Project CRP 5757, 9th Street East, 190th Avenue East to 198th Avenue East in Pierce County, Washington. GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates otherwise, do not rely on this report if it was:

■ not prepared for you, ■ not prepared for your project, ■ not prepared for the specific site explored, or ■ completed before important project changes were made.  

                                                             1

Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org.

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For example, changes that can affect the applicability of this report include those that affect:

■ the function of the proposed structure; ■ elevation, configuration, location, orientation or weight of the proposed structure; ■ composition of the design team; or ■ project ownership. If important changes are made after the date of this report, GeoEngineers should be given the opportunity to review our interpretations and recommendations and provide written modifications or confirmation, as appropriate.

Subsurface Conditions Can Change This report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by manmade events such as construction on or adjacent to the site, or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. Always contact GeoEngineers before applying a report to determine if it remains applicable.

Most Geotechnical and Geologic Findings are Professional Opinions Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then applied our professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions.

Geotechnical Engineering Report Recommendations are Not Final Do not over-rely on the preliminary construction recommendations included in this report. These recommendations are not final, because they were developed principally from GeoEngineers’ professional judgment and opinion. GeoEngineers’ recommendations can be finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability for this report’s recommendations if we do not perform construction observation. Sufficient monitoring, testing and consultation by GeoEngineers should be provided during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork activities are completed in accordance with our recommendations. Retaining GeoEngineers for construction observation for this project is the most effective method of managing the risks associated with unanticipated conditions.

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A Geotechnical Engineering or Geologic Report Could be Subject to Misinterpretation Misinterpretation of this report by other design team members can result in costly problems. You could lower that risk by having GeoEngineers confer with appropriate members of the design team after submitting the report. Also retain GeoEngineers to review pertinent elements of the design team’s plans and specifications. Contractors can also misinterpret a geotechnical engineering or geologic report. Reduce that risk by having GeoEngineers participate in pre-bid and preconstruction conferences, and by providing construction observation.

Do Not Redraw the Exploration Logs Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering or geologic report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk.

Give Contractors a Complete Report and Guidance Some owners and design professionals believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering or geologic report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only then might an owner be in a position to give contractors the best information available, while requiring them to at least share the financial responsibilities stemming from unanticipated conditions. Further, a contingency for unanticipated conditions should be included in your project budget and schedule.

Contractors are Responsible for Site Safety on Their Own Construction Projects Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to on-site personnel and to adjacent properties.

Read These Provisions Closely Some clients, design professionals and contractors may not recognize that the geoscience practices (geotechnical engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. GeoEngineers includes these explanatory “limitations” provisions in our reports to help reduce such risks. Please confer with GeoEngineers if you are unclear how these “Report Limitations and Guidelines for Use” apply to your project or site.

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Geotechnical, Geologic and Environmental Reports Should Not be Interchanged The equipment, techniques and personnel used to perform an environmental study differ significantly from those used to perform a geotechnical or geologic study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually relate any environmental findings, conclusions or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding a specific project.

Biological Pollutants GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention, or assessment of the presence of Biological Pollutants in or around any structure. Accordingly, this report includes no interpretations, recommendations, findings, or conclusions for the purpose of detecting, preventing, assessing, or abating Biological Pollutants. The term “Biological Pollutants” includes, but is not limited to, molds, fungi, spores, bacteria, and viruses, and/or any of their byproducts.

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