Attachment_4_Geotechnical_Report_2010.pdf

106561\POR10R010 January 15, 2010 Copyright 2010 Kleinfelder

9200 SW Nimbus Ave., Suite A, Portland, OR 97008 p | 503.644.9447 f | 503.643.1905

GEOTECHNICAL ENGINEERING REPORT

FORT VANCOUVER NATIONAL HISTORIC SITE

UPGRADE HISTORIC RESERVE VISITOR

CENTER AND EXPAND INTERPRETIVE

OPPORTUNITIES

VANCOUVER, WASHINGTON

KLEINFELDER PROJECT # 106561

January 15, 2010

All Rights Reserved

ONLY THE CLIENT OR ITS DESIGNATED REPRESENTATIVES MAY USE THIS DOCUMENT AND ONLY FOR THE SPECIFIC

PROJECT FOR WHICH THIS REPORT WAS PREPARED.

106561\POR10R010 January 15, 2010

9200 SW Nimbus Ave., Suite A, Portland, OR 97008 p | 503.644.9447 f | 503.643.1905

A Report Prepared For:

AJC Architects Attn: Ms. Jill Jones, AIA 703 East 1700 South Salt Lake City, UT 84105

GEOTECHNICAL INVESTIGATION

FORT VANCOUVER NATIONAL HISTORIC SITE

UPGRADE HISTORIC RESERVE VISITOR CENTER AND EXPAND

INTERPRETIVE OPPORTUNITIES

VANCOUVER, WASHINGTON

Kleinfelder Project Number 106561

Prepared By:

Andy George Ryan White, P.E.

Staff Geotechnical Engineer Geotechnical Engineer

Reviewed by:

Peter L. Stroud, L.E.G.

Principal Engineering Geologist

KLEINFELDER

9200 SW Nimbus Avenue, Suite A Beaverton, Oregon 97008 Phone: (503) 644-9447 Fax: (503) 643-1905

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TABLE OF CONTENTS

Section Page

1.0 INTRODUCTION

1.1 General

1.2 Project Description

1.3 Authorization and Scope of Work

2.0 SITE CONDITIONS

2.1 Geologic Setting

2.2 Subsurface Conditions

2.2.1 Soils

2.2.2 Groundwater

2.2.3 Infiltration Testing

3.0 SEISMIC HAZARD EVALUATION

3.1 Seismic Acceleration and Soil Profile

3.2 Seismic Hazards

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 Site Earthwork Recommendations

4.1.1 Site Preparation

4.1.2 Wet Weather Considerations

4.1.3 Proofrolling

4.1.4 Structural Fill Materials

4.1.5 Trench Backfill

4.2 Foundation Recommendations

4.2.1 Foundation Support Alternatives

4.3 Shallow Spread Footing Foundation Recommendations

4.3.1 Footing Preparation

4.3.2 Footing Embedment Depths

4.3.3 Footing Widths/Bearing Pressure

4.3.4 Foundation Static Settlement

4.3.5 Lateral Resistance

4.3.6 Drainage

4.4 Interior Floor Slabs

4.5 Excavations

4.6 On Site Pavements

4.6.1 Pavement Construction Considerations

4.7 On Site Infiltration of Stormwater

5.0 ADDITIONAL SERVICES

6.0 LIMITATIONS

7.0 REFERENCES

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FIGURES

1 Site Location Map 2 Site Plan

APPENDIX

A Field Exploration Borings B Laboratory Testing

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PROPOSED FORT VANCOUVER ADDITION

VANCOUVER, WASHINGTON

1.0 INTRODUCTION

1.1 GENERAL

The Fort Vancouver National Historic Site Visitor Center is located at 1501 Evergreen Boulevard in Vancouver, Washington. The proposed addition will be located north and east of the existing facility. The general project location is shown on the Site Location Map, Figure 1. The Site Plan, Figure 2, shows the location and configuration of the proposed Visitor Center addition and the locations of the explorations.

1.2 PROJECT DESCRIPTION

We understand that the proposed project will consist of the remodeling and expansion of the existing Visitor Center which was completed in 1962. The addition will be on the northeast side of the existing building and will have dimensions of approximately 105 feet long by between 12 to 32 feet wide along the north side of the Visitor Center and 36 feet long by 13 feet wide along the east end of the Visitor Center. Our understanding of the addition is that it will be a lightly loaded, one-story structure with slab-on-grade construction similar to the existing building. New structural pavement is planned for the parking area just south of TP-1.

The site is relatively level, and the surface of the area proposed for construction is covered with grass or concrete. Based on mapped local geology, subsurface conditions generally consist of gravel with sand, cobbles, and boulders to depths on the order of over 100 feet.

1.3 AUTHORIZATION AND SCOPE OF WORK

The purpose of the geotechnical investigation was to characterize the subsurface conditions in the vicinity of the proposed Visitor Center addition and to provide geotechnical recommendations for use in design and construction. To accomplish this, the following work was completed:

• Review published geologic data for the region available in our files;

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• Complete a field investigation consisting of drilling two mud-rotary borings (B-1 and B-2) to depths of approximately 21.5 feet below the current ground surface and excavating three test pits (TP-1 through TP-3) to depths of 5 to 10 feet below the existing ground surface;

• Complete two open-hole, falling-head infiltration tests;

• Conduct standard classification laboratory tests on selected samples obtained from the field investigation borings;

• Perform geotechnical engineering evaluation to provide the allowable soil bearing for spread footings, estimate the potential post-construction settlements, evaluate the ASCE 7-05 seismic soil profile, and prepare general earthwork recommendations;

and

• Prepare this Geotechnical Engineering Report summarizing our findings and our geotechnical recommendations and conclusions.

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2.0 SITE CONDITIONS

2.1 GEOLOGIC SETTING

The project site is located within the Portland-Vancouver Basin. The Portland- Vancouver Basin is part of the Willamette Valley and Puget Sound physiographic province and is a structural basin filled with igneous and sedimentary rocks of late Miocene, Pliocene, and Pleistocene ages. The basin extends southward into the State of Oregon, bounded by the Tualatin Mountains (also called the Portland West Hills) on the west and the Cascade Range on the east, north, and south. Northwest and northeast trending topographic lineations, faults, and folds exist throughout the Portland Basin (Swanson, et. al., 1993). Based on geologic mapping by Walsh et al. (1987), no structural features are visible in the immediate area of the project.

Upper Pleistocene Outburst Deposits of Glacial Lake Missoula (Qfg) are mapped by Walsh et al. (1987) as the primary geologic unit underlying the project site. The Outburst Deposits generally consist of gravel with sand, cobbles, and boulders deposited during Lake Missoula floods.

2.2 SUBSURFACE CONDITIONS

As discussed in the field exploration section, subsurface conditions at the site were explored by drilling two (2) borings (B-1 and B-2) and excavating three (3) test pits (TP-1 through TP-3). Logs summarizing the subsurface conditions encountered in the borings are presented in Appendix A. Approximate exploration locations are shown on the Site Plan, Figure 2. Soil conditions observed during the subsurface investigation are relatively consistent across the site as summarized below.

2.2.1 Soils

Fill: A layer of fill consisting of variable material, ranging from loose silty gravel to dense sand with gravel in borings B-1 and B-2, respectively, was encountered at the boring locations and extended from the landscape surface of grass and roots (approximately 1-foot thick) to approximately 4.5 feet below existing ground surface (bgs) in the borings and

2.5 to 3.5 feet bgs in the test pits. Sandy fill was fine- to coarse-grained. Gravelly fill consisted of fine to coarse, round to subround materials.

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Gravel: Gravel was encountered at both boring locations and extended from below the fill (approximately 4.5 feet bgs in the borings and 2.5 to 3.5 feet bgs in the test pits) to the bottom of the borings and test pits. Gravelly soils were fine- to coarse-grained. Varying amounts of silt, sand, and cobbles were observed throughout the gravel layer. The relative densities of the gravel ranged between medium dense to very dense. Cobbles and a 1.5-foot diameter boulder were observed in the test pit explorations.

2.2.2 Groundwater

Groundwater was not observed in the test pits and not directly measured in our borings due to the drilling methods used. The borehole was bailed and flushed, and a reading was taken after the hole had a chance to equilibrate. The resulting water level observed was not representative based on visible grades and a review of nearby well logs. However, we anticipate that groundwater beneath the site is hydraulically connected to water levels in the nearby Columbia River and is likely influenced by river levels. It should be noted that fluctuations in groundwater level could occur seasonally. Other factors such as variations in rainfall, utility trench locations and depths, and other factors that were not evident at the time of our investigation could potentially cause further variation in groundwater depth.

2.2.3 Infiltration Testing

One open-hole, falling-head infiltration test was completed in two test pits at depths of 3 and 4 feet, in TP-2 and TP-3, respectively. Following saturation, infiltration testing was completed over an approximately 12 inch by 12 inch area by filling the excavation to an initial head of approximately 6 inches and measuring the drop in the water level for at least 60 minutes. Recommended design infiltration rates are provided in Section 4.7 of this report.

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3.0 SEISMIC HAZARD EVALUATION

3.1 SEISMIC ACCELERATION AND SOIL PROFILE

ASCE 7-05 requires that the facility be designed to sustain the maximum considered earthquake. Based on the borings at the project site, a review of water well logs and geologic maps in our files, the subgrade for the structures may be underlain by generally medium dense to very dense gravel with gravel with sand, cobbles, and boulders to depths of over 100 feet. Based upon our evaluation of the soils disclosed in the boring logs, test pits, and other published geologic information, the seismic soil profile for the upper 100 feet beneath the site would likely be considered a very dense soil profile, with the Site Class defined as C per the 2006 IBC.

• Latitude = 45.626

• Longitude = -122.656

The design values for the spectral response accelerations, SS and S1, are 0.899 and

0.319 g, respectively, at the “bedrock” Site Class B.

3.2 SEISMIC HAZARDS

Seismic hazards that were considered for the site include liquefaction, reduction in bearing capacity, lateral spreading, fault displacement, tsunamis and seiches, and landslides. Soil liquefaction can occur in certain loose, saturated cohesionless sandy or silty soils resulting in a loss of strength due to strong ground shaking from an earthquake. The sandy material encountered in the fill layer in Boring B-2 was estimated to be very dense. Therefore, liquefaction is not considered to be a significant seismic hazard. Hence, reduction in bearing capacity and lateral spreading are not considered hazards at the site. No known faults exist underlying the site so fault displacement is not a hazard requiring consideration. Seismically related landslides, tsunamis, and seiches would not represent a significant hazard to the improvements proposed for this site as stated above.

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4.0 CONCLUSIONS AND RECOMMENDATIONS

Based on the results of the field exploration, laboratory testing, and engineering analyses performed, our opinion is that the proposed project is geotechnically feasible as planned, provided the recommendations of this report are incorporated into project design and construction.

4.1 SITE EARTHWORK RECOMMENDATIONS

4.1.1 Site Preparation

We understand that only minor grading will be required for the proposed addition.

Because of the importance of providing adequate subgrade support, we recommend that the subgrade exposed during excavation and/or stripping within the entire area proposed for re-development be recompacted to at least 92 percent of the modified maximum dry density determined in accordance with ASTM D1557. Due to the presence of silt in the near-surface soils, recompaction may not be possible during wet conditions and could result in subgrade softening. A medium weight (48-inch diameter drum) smooth, steel-wheel roller with the vibratory action turned on probably would be effective in compaction. Smaller hand-operated compactors may need to be used, at the contractor’s responsibility and discretion, near existing structures sensitive to vibrations.

As a general guideline, we suggest keeping large compaction equipment at least 5-feet away from existing structures.

Stripped organic soils (topsoil) will not be suitable for re-use as structural fill. Stripped topsoil can be stockpiled for later use in landscaped areas or berms, if desired. Unwanted soil and materials should be exported from the site.

All waste spoils, excess excavation, or temporary stockpiles should be placed or disposed in a location and manner that will not become unstable; or else should be removed from the site entirely. All waste spoils, excess excavation or temporary stockpiles should be located safely away from all excavations.

Working pads and haul roads should be built and maintained by the contractor to protect the subgrade from construction traffic disturbance. Due to the anticipated surficial silty material encountered, a layer of compacted crushed rock overlying compacted sand or

106561\POR10R010 Page 7 of 17 January 15, 2010 gravel subgrade may be an effective method of constructing a working pad. Also, the contractor should consider utilizing existing paved areas as working pads. Design, performance, and maintenance of the working pad are typically the responsibility of the contractor.

4.1.2 Wet Weather Considerations

The near surface soils generally contain variable amounts of silt. Therefore, material handling and compaction may be possible during dry to moderately wet conditions.

However, during periods of heavy rain or extended wet conditions, proceeding with site earthwork operations using these soils could add significant costs to the project. During periods of heavy rain, the soil may pump until the water has a chance to drain from the soil. In our experience this will occur quickly. We therefore recommend that, if possible, site clearing, preparation, and earthwork be completed when the weather is relatively dry.

No earthwork should be permitted during freezing conditions.

4.1.3 Proofrolling

Following stripping and preparation of the subgrade, we should be contacted to observe a proofroll conducted with a fully loaded 10- to 12-yard dump truck or other suitably loaded rubber-tired construction vehicle. If site constraints do not allow for a proof role, the subgrade should be probed by a representative from our firm.

4.1.4 Structural Fill Materials

Structural fill should only be installed on a subgrade that has been prepared in accordance with the preceding recommendations. Fill material should consist of relatively well-graded soil, or an approved rock-product, that is free of organic material and debris, and contains no particles greater than 2-inches nominal diameter. The suitability of soil for use as compacted structural fill will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion finer than the US Standard No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and compaction becomes more difficult to achieve. Soils containing more than about 5 percent fines cannot consistently be compacted to a dense, non-yielding condition when the water content is significantly greater (or significantly less) than optimum.

The near-surface soils encountered at the site during our subsurface investigation program that contain less than 5 percent passing a No. 200 sieve would be suitable for

106561\POR10R010 Page 8 of 17 January 15, 2010 placement as structural fill during wet weather conditions. Saturated, structural fill conditions may be problematic, and would require time for excess water to drain. At the time of our exploration, the in-situ moisture content of the near-surface, gravelly soil ranged from 11 to 32 percent. The moisture content of the near-surface soils can be expected to vary depending on the time of year and recent weather conditions.

The silt fraction of the near-surface soils is moisture sensitive, and during wet weather, native on-site soils may become unworkable because of excess moisture content. In our experience, if the silt fraction is relatively small, then the excess moisture should drain quickly following the wet weather. Structural fill should be uniformly moisture conditioned to within about ±2 percent of the optimum moisture content and compacted in thin lifts using suitable mechanical compaction equipment. We recommend that fills intended to support structures be placed in horizontal lifts not exceeding about 8 inches in loose thickness and be compacted to at least 92 percent of the maximum dry density as determined by the modified Proctor test method (ASTM D 1557).

4.1.5 Trench Backfill

All utility trenches should be backfilled with material that is suitable for compaction. The acceptability of trench backfill material should be in accordance with the same criteria described for "structural fill," whether it is clean sand, sand and gravel, or crushed rock, with the exception of “reject rock.” The backfill should be compacted to at least 90 percent of the maximum dry density as determined by the modified Proctor test method (ASTM D 1557) below 2 feet from the finished subgrade surface, and compacted to at least 92 percent in the upper 2 feet.

4.2 FOUNDATION RECOMMENDATIONS

4.2.1 Foundation Support Alternatives

Building foundation loads were not available at the time this report was prepared. We estimate building loads will be less than 20 kips for columns, 3 kips per lineal foot for walls, and 250 pounds per square foot (psf) for slabs. The following recommendations were based on the estimated loads stated above. If actual design loads will exceed these estimates we should be consulted to revise our recommendations as they may not apply.

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4.3 SHALLOW SPREAD FOOTING FOUNDATION RECOMMENDATIONS

4.3.1 Footing Preparation

We recommend that all footing excavations should be trimmed neat and footing subgrades carefully prepared. Footing subgrades should be recompacted 92 percent of the maximum dry density as determined by the modified Proctor test method (ASTM D 1557). Placement of 3 to 4 inches of lightly compacted crushed rock would help prevent disturbance to the bottom of the footing that can be attributed to weather, foot, or equipment traffic. Placement of this base rock is the prerogative of the contractor;

regardless, the footing subgrade should be in a dense condition prior to pouring concrete.

We recommend that the footing excavations be observed by us, the geotechnical engineer of record, prior to placing footing base rock, reinforcing steel, and concrete to check that anticipated conditions have been encountered and that the recommendations of this report have been followed.

4.3.2 Footing Embedment Depths

We recommend that exterior footings be founded a minimum of 18 inches below the lowest adjacent exterior grade. We recommend that interior footings have a minimum embedment of 12 inches.

4.3.3 Footing Widths/Bearing Pressure

Individual column footings and continuous strip footings should have minimum widths of 36 and 18 inches, respectively. We recommend that building footings founded on dense, silty gravel fill or gravel be prepared as recommended herein be proportioned for a maximum allowable bearing pressure of 3,000 psf. This applies to dead plus live loads.

Allowable bearing may be increased as allowed by building code for seismic and wind loads.

Please note that the above recommended bearing pressure is a net value, and the weight of concrete in the portions of the foundations that extend below grade can be neglected in proportioning the foundations.

4.3.4 Foundation Static Settlement

Footing settlements will result from the column and wall loadings, as well as from the effects of floor live loads. Based on these combined effects and our evaluation of the

106561\POR10R010 Page 10 of 17 January 15, 2010 subsurface conditions, we estimate the static settlement will be less than 1 inch with static differential settlement between two adjacent columns of less than 0.5 inch for footings proportioned as recommended above.

4.3.5 Lateral Resistance

The soil resistance available to withstand lateral foundation loads is a function of the frictional resistance which can develop on the base and the passive resistance which can develop on the face of below-grade elements of the structure as these elements tend to move into the soil. For spread footings founded on a granular leveling course placed in accordance with the above recommendations, the allowable frictional resistance may be computed using a coefficient of friction of 0.40 applied to vertical dead-load forces. In addition, the design value for passive pressure should not exceed the partial value of 150d psf (where “d” is the depth of the embedment), due to the large amounts of movement necessary to mobilize full passive resistance. The top foot of soil should not be used in calculating passive resistance since construction and post-construction activities often disturb this upper material.

4.3.6 Drainage

Seasonal groundwater levels and perched groundwater following rain has the potential to fluctuate up to near the existing ground surface. Perimeter footing drains are recommended for exterior footings in order to reduce the risk of shallow water or stormwater runoff from entering the building, as well as to reduce the risk of adverse hydrostatic pressures. The foundation subdrainage system should include a minimum 4-inch diameter perforated pipe in a drain gravel envelope. A non-woven geotextile filter fabric, such as Mirafi 140N or equivalent, should be used to completely wrap the drain gravel envelope, separating it from the native soil and footing backfill material. The invert of the perimeter drain lines should be placed near the same elevation as the bottom of the footing or grade beam. Also, the subdrainage system should be sealed at the ground surface, and the finished ground surface should be such to drain surface water away from the walls. The perforated subdrainage pipe should be laid to drain by gravity into a non-perforated solid pipe and finally connected with the site drainage system at a suitable location. Water from downspouts and surface water should be independently collected and routed to a storm sewer or other permissible positive outlet.

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4.4 INTERIOR FLOOR SLABS

The subgrade under all floor slab areas should be prepared in accordance with the Site Preparation and/or Wet Weather Construction section(s) above as applicable. We recommend that firm, recompacted subgrade be overlain by 6 inches of well-graded crushed rock during the dry season. During wet conditions, if the subgrade cannot be recompacted, it may be necessary to increase the base rock thickness, and we should be consulted. Soft, wet subgrade may require over-excavation and replacement with compacted structural fill prior to placement of base rock. One hundred percent of the compacted crushed rock should pass the 1-inch sieve, and less than 5 percent should pass the No. 200 sieve (wet sieve analysis). We recommend the granular layer be compacted to at least 92 percent of the maximum dry density as determined by the Modified Proctor test method (ASTM D 1557). To reduce the potential for underslab moisture problems, we recommend that, where possible, floor slabs be established 6 inches or more above surrounding final grades. Alternatively, proper sloping of surrounding final grades may be used to provide adequate drainage away from floor slabs and foundation subgrades. This may not be possible for embedded structures and/or basement slabs. As such measures should be taken to provide positive drainage away from slabs. This may include perimeter foundation drains, under-slab drainage, or use of trench drains.

For floor slabs supported on subgrades and a base course prepared in accordance with the preceding recommendations, the floor slab may be designed using a modulus of subgrade/base rock reaction (k) of 200 pounds per cubic inch.

4.5 EXCAVATIONS

Based upon our explorations, we anticipate that most of the excavations for cuts and utilities can be accomplished using conventional equipment.

The native soils encountered during our site investigation are likely prone to collapse suddenly and without warning during excavation. Any excavations deeper than 4 feet that will involve personnel within the excavation should be adequately sloped or shored in accordance with Washington OSHA requirements. Temporary excavation sloping is generally the prerogative of the contractor, and our suggestions are only for the designer to use in developing a practical, constructible design. We suggest that unshored temporary cuts up to 10-feet deep may be sloped at no steeper than 1.5H:1V (Horizontal:

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Vertical) provided groundwater is not encountered. The recommended maximum inclination for temporary slopes assumes that the ground surface behind the cut slopes is level and that surface loads from equipment and materials are kept a sufficient distance away from the top of the slope (typically at least half the slope height). Stability of temporary excavations is the responsibility of the contractor, who must maintain safe excavation slopes and/or shoring. Excavations must comply with the current requirements of OSHA and the State of Washington. We are providing this information solely as a service to our client. Under no circumstances should the information provided be interpreted to mean that Kleinfelder is assuming responsibility for construction site safety or the contractor’s activities. The contractor should be aware that slope height, slope inclination, or excavation depths (including utility trench excavations) should in no case exceed those specified in local, state, and/or federal safety regulations (e.g., OSHA Health and Safety Standards for Excavations, 29 CFR Part 1926, or successor regulations).

Such regulations are strictly enforced and, if they are not followed, the Owner, contractor, and/or earthwork and utility subcontractors could be liable for substantial penalties.

During wet weather, earthen berms or other methods should be used to prevent surface runoff water from entering excavations. All runoff water and groundwater encountered within the excavation(s) should be collected and disposed of outside the construction limits.

4.6 ON SITE PAVEMENTS

We understand that new pavements will be constructed within the parking lot of the Fort Vancouver Visitor Center. Specific traffic data was not available at the time this report was prepared. We have estimated traffic at the Visitor Center will consist of fewer than approximately 10 trucks per day (0.6 ESALS per truck). For a 20-year design life this corresponds to approximately 60,000 ESALS. If specific traffic information is available, we should be contacted to revise our analyses.

Structural pavement calculations were based on 1993 AASHTO design methods for flexible pavements and the 2005 Washington Department of Transportation (WSDOT) pavement guide. Table 1 presents a summary of our pavement design parameters.

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Table 1

Pavement Design Parameters

Design Parameter Value

Reliability Level 85%

Initial serviceability 4.5

Terminal serviceability 3.0

Subgrade modulus 6,000 psi*

Drainage coefficient 1.0

Standard deviation 0.5 aHMAC 0.44 aCS 0.13

Design 20-yr ESAL 60,000

* Subgrade resilient modulus MR based on California Bearing Ratio testing of remolded laboratory specimens compacted to 92% of ASTM D1557 and existing correlations to MR (MR = 1500 x CBR). The laboratory CBR value has been reduced to account for soil type, variability, and construction season variability.

Based on the parameters above and engineering analysis, we recommend a flexible pavement section of 3 inches of hot mix asphalt (HMAC) over 8 inches of crushed surfacing (CS) base rock for new pavements constructed in the Fort Vancouver Visitor Center parking lot.

Our pavement recommendations assume that the existing subgrade conditions are firm sandy silt and silt materials, prepared in general accordance with City of Vancouver requirements and Section 4.1 of this report.

4.6.1 Pavement Construction Considerations

Work should be performed in accordance with the latest edition of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction and the latest requirements of the City of Vancouver. HMAC should conform to the requirements of Section 5-04 Hot Mix Asphalt of the WSDOT Standard Specification. Crushed surfacing should conform to Section 9-03.9(3) Crushed Surfacing of the WSDOT Standard Specifications.

According to City of Vancouver standards, the upper 6 inches of subgrade should be scarified to a depth of 6 inches and recompacted to a minimum of 95 percent of AASHTO T99 maximum dry density. In our opinion, 92 percent of AASHTO 180 or ASTM D1557 Modified Proctor should be considered an equivalent level of relative compaction.

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Scarification and re-compaction of the exposed subgrade (where existing pavements are to be removed for the new pavement construction) may be waived where existing shallow utilities may underlie the existing subgrade and where the exposed subgrade is observed to be firm, as indicated by proofrolling with a fully-loaded dump truck and/or probing, moisture content, and visual appearance.

4.7 ON SITE INFILTRATION OF STORMWATER

Kleinfelder conducted an infiltration evaluation including:

• Open-hole, falling-head infiltration test in two (2) test pits, excavated to observe for soil profiling, obtain soil samples, and conduct testing; and

• Laboratory testing: particle size analyses (hydrometer).

Kleinfelder conducted soil infiltration-related field investigations and testing at the Fort Vancouver Visitor Center site on December 16, 2009. Exploration data from the prior explorations by Kleinfelder and the infiltration evaluation test pits were used to develop a conceptual understanding of the subsurface conditions, including soil heterogeneity and grain size variability.

Infiltration characteristics were evaluated by means of grain size testing and use of estimated long-term design infiltration rates based on Figure 3.28 in the Washington State Department of Ecology Western Washington Stormwater Design Manual. Based on field and laboratory test results, we recommend a design infiltration rate of 0.7 inches per hour.

We request that the civil engineer provide us the design storm flow hydrograph and information on infiltration facility type and layout so that revised recommendations can be provided as appropriate.

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5.0 ADDITIONAL SERVICES

We recommend that Kleinfelder be retained to review the project plans and specifications to evaluate if they are in substantial conformance with the conclusions and recommendations contained in this report, and to evaluate if they are compatible with the anticipated site geotechnical conditions. Moreover, we recommend that we review material gradation submittals and observe construction operations relating to earthwork, subgrade preparation, and compaction to check if the work is proceeding in accordance with the intent of the design concepts, specifications and/or recommendations, and to allow for design changes in the event that subsurface conditions differ from those anticipated. Unless we have the opportunity during construction to confirm our assumptions, interpretations, and analyses, we cannot be held responsible for the applicability of our conclusions and recommendations for subsurface conditions that are different from those anticipated.

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6.0 LIMITATIONS

This report has been prepared to aid AJC Architects in the design of the proposed addition and is in accordance with generally accepted local geotechnical engineering practice. Our description of the project represents our understanding of the significant aspects of the project relevant to the design and construction of earthwork, foundations, and related items. In the event that any changes in the basic design or location of the structure as outlined in this report are planned, or if there is more than 2 years lapse of time between our investigation and the start of work at the site, we should be given the opportunity to review the changes or conditions existing, and to modify or reaffirm in writing the conclusions and recommendations of this report, considering the changed conditions or time lapse.

The scope of our geotechnical services did not include any environmental investigation for the presence or absence of wetlands or hazardous or toxic materials in the soil, surface water, groundwater, or air; on, below, or around the site. Any statements in this report, or on the boring logs, regarding odors noted or unusual or suspicious items or conditions observed are solely for the information of our client.

The evaluations and recommendations represented in this report are based on the data obtained from the borings made at the locations indicated on the Site Plan, and from other information discussed herein. This report is based on the assumption that the subsurface conditions everywhere are not significantly different from those revealed by the borings. However, variations in soil conditions may exist between the boring locations and, also, general groundwater levels may fluctuate from time to time. The nature and extent of the variations may not become evident until construction. If subsurface conditions different from those encountered in the exploration are observed or encountered during construction or appear to be present beneath or beyond excavations, we should be advised at once so that we can observe and review these conditions and reconsider our recommendations where necessary.

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7.0 REFERENCES

Swanson, R.D., McFarland, W.D., Gonthier, J.B., and Wilkinson, J.M., 1993, A description of hydrogeologic units in the Portland Basin, Oregon and Washington:

U.S. Geological Survey Water-Resources Investigations Report 90-4196, 56 p., scale: 1:100,000.

Walsh, T.J., Korosec, M.A., Phillips, W.M., Logan, R.L., and Schasse, H.W., 1987, Geologic Map of Washington – Southwest Quadrant. Washington Division of Geology and Earth Resources Geologic Map GM-34.

Washington State Department of Ecology. (February 2005). Stormwater Management in

Western Washington: Volume III — Hydrologic Analysis and Flow Control Design/BMPs (Publication No. 05-10-31).

SCALE IN FEET

0 20 40

FORT VANCOUVER

VISITOR CENTER EXPANSION

VANCOUVER, WASHINGTON

FIGURE:

PROJECT NO. 106561

DRAWN: 10/09

DRAWN BY: TLK

CHECKED BY: ATG

FILE NAME:

106561F1.pdf

SITE LOCATION MAP

SITE

Appendix A Field Explorations

Kleinfelder Field Explorations January 2010 A-1 Fort Vancouver Visitor Center Addition (106561)

APPENDIX A

FIELD EXPLORATIONS

General

The subsurface conditions for the proposed addition to the Fort Vancouver National Historic Site

Visitor Center were explored by drilling two (2) borings (designated B-1 and B-2) and excavating three (3) test pits (designated TP-1 through TP-3) at the approximate locations shown in Figure

2, Site Plan. The exploration program was completed between October 19, 2009 and December

16, 2009.

The procedures and techniques used to advance the borings, excavate test pits, and collect samples for this project are described in detail in the following paragraphs. Unless otherwise noted, soil sampling and classification procedures generally followed local engineering practices.

Borings

Drilling. Borings were advanced to total depths 21.5 feet below the ground surface (bgs). Soil conditions observed during the subsurface investigation are relatively consistent across the site.

The borings were advanced using mud-rotary drilling techniques on a truck-mounted drill rig provided and operated by Western States Soil Conservation, Inc., of Hubbard, Oregon. Borings were backfilled using bentonite chips to the ground surface. Drilling of the borings was observed by members of our geology and engineering staff who located the general exploration area and maintained a log of the subsurface conditions and materials encountered during the course of the work.

Sampling. Disturbed soil samples were taken in the borings at selected depth intervals using both a standard 2-inch outer diameter (O.D.) and 3-inch O.D. split-spoon sampler and procedures prescribed for the Standard Penetration Test, ASTM 1586 During the Standard Penetration Test.

The sampler was driven 18 inches into the soil using a 140-pound hammer dropped 30 inches.

The number of blows required to drive the sampler the last 12 inches is defined as the standard penetration resistance (or N-value). The N-value provides a measure of the relative density of granular soils such as sand and gravel, and the consistency of cohesive soils such as silt, clay, and silty clay. The disturbed soil samples were examined and representative samples were sealed in jars for further examination and physical testing in our laboratory. The SPT at each of

January 2010 A-2 Fort Vancouver Visitor Center Addition (106561) the borings was conducted using auto-trip hammer. Values shown on boring logs have been corrected to N60 (cathead) values.

Test Pits

Excavations. The test pits were excavated with a rubber tire backhoe provided and operated by

Dan Fisher Excavating, Inc., of Forest Grove, Oregon. The test pits were observed by a member of our staff who maintained a detailed log of subsurface conditions and materials encountered, collected soil samples at appropriate depth intervals, and documented the abandonment. Each test pit was abandoned by backfilling the excavation with native soil.

Infiltration Tests. Kleinfelder completed a total of two (2) open-hole, falling head infiltration tests at the site in conjunction with our explorations completed at TP-2 and TP-3. In general, soil conditions tested consisted of silt (ML) and sand with silt (SP-SM). Open-hole testing was completed at depths of 3 and 4 feet, in TP-2 and TP-3, respectively. Following saturation, infiltration testing was completed over an approximate 12 inch by 12 inch area by filling the excavation to an initial head of approximately 6 inches and measuring the drop in the water level for at least 60 minutes.

Material Descriptions

Initially, the soil samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity, peculiar odors, and other distinguishing characteristics were noted. Afterwards, the samples were re-examined in the laboratory where various standard classification tests were conducted; field classifications were modified where necessary. The terminologies used in the soil classifications are defined in Table A1, which is in general conformance with ASTM D2488 Visual-Manual method.

Boring and Test Pit Logs

Figure A1 is a legend explaining the information and symbols presented on the boring and test pit logs. The logs of the borings are presented on Figures A2 and A3. The logs of the test pits are presented on Figures A4 and A5. The logs report the various types of materials encountered and the depths where the materials and/or characteristics of these materials changed, although the changes may be gradual. Where material types and descriptions changed between samples, the contacts were interpreted. On each log, the types of samples collected (including their identification number) are reported immediately to the right of the material classification. Further

January 2010 A-3 Fort Vancouver Visitor Center Addition (106561) to the right the standard penetration resistances (N60 values) and/or the natural water (moisture) contents are plotted. Backfill details are also provided.

Groundwater

Groundwater was not observed in the test pits and not directly measured in our borings due to the drilling methods used. However, we anticipate that groundwater beneath the site is hydraulically connected to water levels in the nearby Columbia River and is likely influenced by river levels. It should be noted that fluctuations in groundwater level could occur seasonally. Other factors such as variations in rainfall, utility trench locations and depths, and other factors that were not evident at the time of our investigation could potentially cause further variation in groundwater depth.

Table A1 Terminology Used to Describe Soil

Page 1 of 2 TABLE A1

Soil Descriptions

Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based upon total dry weight, is the primary soil type and is capitalized in our log descriptions, e.g., SAND, GRAVEL, SILT or CLAY. Lesser percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the Visual-Manual Procedure (ASTM D2488- 93). “General Accordance” means that certain local and common descriptive practices have been followed.

In accordance with ASTM D2488, group symbols (such as GP or CH) are applied on that portion of the soil passing the 3-inch (75mm) sieve based upon visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils.

Fine - Grained Soils (More than 50% fines passing 0.074 mm, #200 sieve) The primary soil type, i.e. SILT or CLAY is designated through visual – manual procedures to evaluate soil toughness, dilatency, dry strength, and plasticity. The following describes the terminology used to describe fine - grained soils, and varies from ASTM 2488 terminology in the use of some common terms.

Primary soil NAME, adjective and symbols Plasticity

Description Plasticity Index (PI)

ML & MH

CL & CH

OL & OH

SILT Organic SILT Non-plastic 0 - 3 SILT Organic SILT Low plasticity 4 - 10

Clayey SILT Silty CLAY Organic clayey SILT Medium Plasticity >10 – 20 Clayey SILT CLAY Organic silty CLAY High Plasticity >20 – 40 Clayey SILT CLAY Organic CLAY Very Plastic >40

Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:

Description % Composition Trace sand, trace gravel 5% - 10%

With sand; with gravel 15% - 25% Sandy, or gravelly 30% - 45%

Borderline Symbols, for example CH/MH, are used where soils are not distinctly in one category or where variable soil units contain more than one soil type. Dual Symbols, for example CL-ML, are used where two symbols are required in accordance with ASTM D2488.

Soil Consistency. Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 4). Descriptive terms are based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows.

Consistency Term SPT N-value Unconfined Compressive Strength Tons/sq.ft. kPa

Very soft Less than 2 Less than 0.25 Less than 24 Soft 2 - 4 0.25 - 0.5 24 - 48

Medium stiff 5 - 8 0.5 - 1.0 48 – 96 Stiff 9 - 15 1.0 - 2.0 96 – 192

Very stiff 16 - 30 2.0 - 4.0 192 – 383 Hard Over 30 Over 4.0 Over 383

Note: For SILT with low to non-plastic behavior, (i.e., PI < 4) a relative density description is applied.

Table A1 (Continued) Terminology Used to Describe Soil

Page 2 of 2 TABLE A1

������������������������(less than 50% fines)

Coarse-grained soil descriptions, i.e., SAND or GRAVEL, are based on that portion of materials passing a 3-inch (75mm) sieve. Coarse-grained soil group symbols are applied in accordance with ASTM D2488 based upon the degree of grading, or distribution of grain sizes of the soil. For example, well graded sand containing a wide range of grain sizes is designated SW; poorly graded gravel, GP, contains high percentages of only certain grain sizes. Terms applied to grain sizes follow.

Particle Diameter Inches Millimeters

Sand (S) 0.003 - 0.19 0.075 - 4.8 Gravel (G) 0.19 - 3.0 4.8 - 75

Additional Constituents Cobble 3.0 - 12 75 - 300

Boulder 12 - 120 300 - 3050 Rock Block >120 >3050

The primary soil type is capitalized, and the amount of fines in the soil are described as indicated by the following examples. Other soil mixtures will provide similar descriptive names.

Example: Coarse-Grained Soil Descriptions with Fines

5% fines 10% fines (Dual Symbols) 15% to 45% fines

GRAVEL with trace silt: GW or GP GRAVEL with silt, GW-GM Silty GRAVEL: GM SAND with trace clay: SW or SP SAND with clay, SP-SC Silty SAND: SM

Additional descriptive terminology applied to coarse-grained soils follow.

Coarse-Grained Soil Containing Secondary Constituents

Clean < 5% fines With sand or with gravel 15% - 25% sand or gravel

Sandy or gravelly 30% - 45% sand or gravel With cobbles; with boulders Any amount cobbles or boulders.

Additional terms may be used to describe amount including abundant, scattered.

Cobble and boulder deposits may include a description of the matrix soils, as defined above.

Relative Density terms are applied to granular, non-plastic soils based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84.

Relative Density Term SPT N-value Very loose 0 - 4

Loose 4 - 10 Medium dense 10 - 30

Dense 30 - 50 Very dense > 50

D e p th fe e t)

N u m b e r

T y p e

E X A M

P

LE

Well Construction

Detail and Drilling Remarks Material Description

R e p o rt

N E

W L

O G

O L

E G

E N

D

P A

G E

T e m p la te

S

Q U

IE

R

K

L E

IN

F

E L

D E

R

T E

M P

L A

T E

S .G

T

P ro j

ID

G

IN

T

.G

J

K y I

D

B -1 ri n te d

/2

/0

S-3

Fort Vancouver Visitor Center Addition

Very dense brown poorly-graded GRAVEL (GP) with sand, fine to coarse gravel, fine sand, wet.

E le v a ti o n fe e t)

FINE-GRAINED ALLUVIAL / FLOOD DEPOSITS

3/8" Bentonite Chip Backfill

LOG COLUMN DESCRIPTIONS

Asphalt

Remarks:

Well Construction:

3 7

Stiff brown SILT (ML) with fine to coarse sand, low to medium plasticity, moist.

Elevation:

Elevation (if available) is referenced to project datum.

Depth is depth below ground surface.

Description of subsurface soil and rock material encountered. Division lines between deposits are defined on Sheet 2.

Changes may be gradual in nature or occur over a longer interval than indicated on the log.

Soil classifications are in general conformace with ASTM Visual-Manual Procedure, D2488. Description terms include moisture, color, and relative density/consistency.

Graphic depiction of the subsurface material encountered (refer, Sheet 2).

Sample identification number and type of sample (refer, Sheet 2) collected at depth interval shown.

Graphical presentation of field and laboratory data (refer, Sheet 2).

SPT (N-Value): Standard Penetration Test (SPT) N-Value is the number of blows required to drive a standard (2.0-inch) split spoon sampler a distance of 1 foot using a 140-lb. hammer, dropped 30 inches (ASTM D 1586). Other samplers and hammers may be corrected to SPT values- see text.

Recovery: The total length of the sample recovered as a percentage of the total sampled interval. The scale (0% - 100%) is shown at the top of the log column.

RQD: Rock Quality Designation (RQD) is graphically portrayed for each core run. The scale (0 - 100) is shown at the top of the log column.

Moisture: Natural water content of the soil sample as determined in the lab. The scale (0% - 100%) is shown at the top of the log column.

Graphic depiction of well construction.

Descriptive comments on well construction, drilling and ground observations, and water level readings.

Graphic Log:

Medium high strength (R4) dark gray BASALT, close to medium close fractures, very slight weathering.

Material Description:

GINKGO-UNIT C.R.B.

Flush Mount Monument

Project No. 106561

Vancouver, Washington

Sample Number and Type

Field and Laboratory Data:

1 2 6

Grades to high strength (R5)

Material Description

COARSE-GRAINED ALLUVIAL / FLOOD DEPOSITS

7 ft -July 12, 2001

2-inch PVC Casing

10 x 20 Silica Sand

0.020-inch Slotted Well Screen

R-7

BORING LOG LEGEND

FIGURE A1

S-2

Pocket Penetrometer

0.0 5.02.5

Torvane

Shear Strength, T.S.F. (approx.)

SPT (N-value)

S-5

R-6

(Sheet 1 of 2)

S-1

N u m b e r

E le v a ti o n fe e t)

Well Construction

0 100

D e p th fe e t)

S a m p le

S-4

G ra p h ic

L o g

S a m p le

G ra p h ic

L o g

Field and Laboratory Data

Detail and Drilling Remarks

Moisture, %

Field and Laboratory Data

Fill materials

Seal Material; Bentonite Chips, Bentonite Grout, etc.

Aggregate Backfill

Grout/Concrete

Internal Material Boundary

GRAVEL

AND

GRAVELLY

SOILS

TYPICAL

LETTER

(LITTLE OR NO FINES)

DESCRIPTIONS

Vibrating-wire transducer in sand filter

MORE THAN 50% OF

COARSE FRACTION

RETAINED ON NO. 4

SIEVE

Note: Statigraphic and material boundaries shown on boring logs may reflect changes in lithology or material that are gradual in nature or occur over a greater interval than reflected on the log.

MORE THAN 50%

OF MATERIAL IS

SMALLER THAN NO.

200 SIEVE SIZE

Fort Vancouver Visitor Center Addition

SAND

AND

SANDY

SOILS

= Bulk Sample

SOIL SAMPLES

= Rock Core Sample

= Grab Sample

= 3.0" O.D. Split Spoon Sample

= Natural Water Content, %

= Torvane

R e p o rt

N E

W L

O G

O L

E G

E N

D

P A

G E

T e m p la te

S

Q U

IE

R

K

L E

IN

F

E L

D E

R

T E

M P

L A

T E

S .G j

ID

G

IN

T

.G y I

D n te d

/2

/0

Pavement section

MAJOR DIVISIONS

Topsoil

FINE

GRAINED

SOILS

SOIL CLASSIFICATION CHART

SW

INORGANIC CLAYS OF HIGH

PLASTICITY

SILTY SANDS, SAND - SILT MIXTURES

BASALT Bedrock

Weathered BASALT bedrock

SURFICIAL MATERIALS

Primary Unit Boundary

Vancouver, Washington

Project No. 106561

Flush monument set in concrete.

Native Material; Slough, Replaced Native, etc.

Transducer cable in bentonite seal.

(APPRECIABLE AMOUNT

OF FINES)

Filter pack, well casing shown where applicable.

Bentonite seal, well casing shown where applicable.

BEDROCK UNITS

SILTSTONE/CLAYSTONE

SP

WELL-GRADED GRAVELS, GRAVEL -

SAND MIXTURES, LITTLE OR NO

FINES

PT

INORGANIC SILTS AND VERY FINE

SANDS, ROCK FLOUR, SILTY OR

CLAYEY FINE SANDS OR CLAYEY

SILTS WITH SLIGHT PLASTICITY

Filter Material; 10/20 Silica Sand, Pre-Pack Filter, etc.

Fill materials with graphic symbol

SYMBOLS

MH

SOIL TESTS

= Photoionization Detector (PID)

ATTERB…