EPA_WED_Geotechnical_Report_20090513.pdf

L:\2009\Projects\102397\POR9R088.doc © 2009 Kleinfelder Page i of iv May 13, 2009

15050 S.W. Koll Parkway, Suite L Beaverton, OR

97006-6028 p| 503.644.9447 f| 503.643.1905 kleinfelder.com

GEOTECHNICAL INVESTIGATION REPORT

PHASE 1A LABORATORY MODERNIZATION

WESTERN ECOLOGY BUILDING, EPA FACILITY

200 SW 35

TH

STREET

CORVALLIS, OREGON

May 13, 2009

Copyright 2009 Kleinfelder

All Rights Reserved

Unauthorized use or copying of this document is strictly prohibited by anyone other than the client for the specific project.

L:\2009\Projects\102397\POR9R088.doc Page ii of iv May 13, 2009 © 2009 Kleinfelder

A Report Prepared For:

Mr. Dave Buesser, PE Plant Engineering Consultants 320 W. Fillmore, Suite 100 Colorado Springs, CO 80907

GEOTECHNICAL INVESTIGATION REPORT

PHASE 1A LABORATORY MODERNIZATION

WESTERN ECOLOGY BUILDING, EPA FACILITY

200 SW 35

TH

STREET

CORVALLIS, OREGON

Kleinfelder Project Number 102397

Prepared By:

Kevin R. Wells, EIT

Engineering Staff Professional

Justin G. Moderie, P.E.

Geotechnical Engineer

KLEINFELDER WEST, INC.

15050 SW Koll Parkway, Suite L

Beaverton, OR 97006

May 13, 2009

TABLE OF CONTENTS

Section Page

L:\2009\Projects\102397\POR9R088.doc Page iii of iv May 13, 2009 © 2009 Kleinfelder

1.0 INTRODUCTION

1.1 GENERAL

1.2 PROJECT DESCRIPTION

1.3 AUTHORIZATION AND SCOPE

2.0 FIELD EXLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

2.2 LABORATORY TESTING

2.2.1 General

3.0 SITE CONDITIONS

3.1 REGIONAL GEOLOGIC SETTING

3.2 SURFACE CONDITIONS

3.3 SUBSURFACE CONDITIONS

3.3.1 GROUNDWATER

3.4 EXPANSIVE SOILS

4.0 SEISMIC HAZARDS AND FAULTING

4.1 SEISMIC HAZARDS

4.1.1 Seismicity

4.1.2 Fault Surface Rupture

4.1.3 Liquefaction Potential

4.2 SEISMIC ACCELERATION AND SOIL PROFILE

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 SITE EARTHWORK

5.1.1 General

5.1.2 Site Preparation

5.1.3 Building Pad Preparation

5.1.4 Proofrolling

5.1.5 Structural Fill Materials

5.1.6 Wet Weather Construction Considerations

5.2 TRENCH BACKFILL

5.3 FOUNDATION RECOMMENDATIONS

5.3.1 Footing Preparation

5.3.2 Frost Penetration/Footing Embedment Depths

5.3.3 Footing Widths/Bearing Pressure

5.3.4 Foundation Static Settlement

5.3.5 Lateral Resistance

5.4 RETAINING WALLS

5.4.1 Lateral Earth Pressures

Active and At-Rest Pressures

5.4.2 Drainage

5.5 PREPARATION FOR INTERIOR CONCRETE SLAB

5.6 EXCAVATIONS

5.7 PERMANENT SLOPES

5.8 PAVEMENT RECOMMANDATIONS

TABLE OF CONTENTS (Cont.)

Section Page

© 2009 Kleinfelder Page iv of iv May 13, 2009

6.0 ADDITIONAL SERVICES

6.1 PLANS AND SPECIFICATIONS REVIEW

6.2 CONSTRUCTION OBSERVATION AND TESTING

7.0 UNCERTAINTY AND LIMITATIONS

FIGURES

Figure 1 Vicinity Map Figure 2 Site Plan

APPENDICES

Appendix A Field Investigation Appendix B Laboratory Test Results Appendix C ASFE Insert

© 2009 Kleinfelder Page 1 of 27 May 13, 2009

1.0 INTRODUCTION

1.1 GENERAL

This report presents the results of our geotechnical investigation for the Phase 1A

Laboratory Modernization for the Western Ecology Division, EPA Facility located at 200

SW 35

th

Street in Corvallis, Oregon. The purpose of our geotechnical exploration was to explore the subsurface conditions at the project location and, based on the conditions encountered during our field study, provide recommendations pertaining to the geotechnical aspects of the proposed development as outlined below in the

Authorization and Scope of Work section of this report.

The general site location is shown on the Vicinity Map, Figure 1. A site plan showing approximate field exploration locations is presented as Figure 2, Site Plan.

The latitude and longitude coordinates of the project are:

Latitude: 44.565°N

Longitude: -123.290°W

This report includes our recommendations related to the geotechnical aspects of project design and construction. Conclusions and recommendations presented in this report are based on our review of previous geotechnical borings in the area, our review of readily available local geologic maps, the subsurface conditions encountered at our explorations, our understanding of the project, and the provisions and requirements outlined in the Additional Services and Limitations sections of this report.

Recommendations presented herein should not be extrapolated to other areas or used for other projects without our prior review and consent.

1.2 PROJECT DESCRIPTION

Based on our review of Figure 4.3 of the Proposed Master Plan, Site Development Plan dated October 2006, the proposed development will include a new one- to two-story structure to be located within the open-space interior of the existing EPA facility immediately west of the existing main building. The structure will have a footprint of approximately 8,000 square feet and include a new annex, atrium, and greenhouse.

Appurtenant construction will consist of new asphalt paving, concrete flatwork, © 2009 Kleinfelder Page 2 of 27 May 13, 2009 underground utilities, and landscaping. Based on conversations with the civil engineer

(Farnsworth Group), we understand that a grading plan is not yet available for the site.

We anticipate grades on the building pad will have to be raised on the order of 1 foot.

Existing improvements within the project area include low-lying, shrubs, trees, exterior flatwork, asphalt pavements, underground utilities, grasses, and an at-grade power transformer. Many of these existing improvements will be removed for the new construction.

The site is generally flat with cuts and fills anticipated to be less than 2 feet across the site to establish finished grades. For the purpose of this report, we assume that isolated column and wall loads for these new structures will not exceed 120 kips and 3-

4 kips/foot, respectively. We understand that building occupancy will not require the preparation of a site specific seismic hazard assessment as defined in the Oregon

Structural Special Code (OSSC 2008).

1.3 AUTHORIZATION AND SCOPE

Kleinfelder has performed this geotechnical investigation accordance with the scope, assumptions, and limitations described in our October 21, 2008 proposal entitled, “Proposal for Phase 1A Laboratory Modernization, Western Ecology Division, EPA

Facility, 200 SW 35 th

Street, Corvallis, Oregon.” Our scope of work was authorized by

Mr. Dave Buesser of Plant Engineering Consultants and included the following:

• Review of readily available geotechnical and geologic data, including review of previous borings performed in the project vicinity and local geologic maps;

• A subsurface investigation program including the completion of six borings within the project area; three borings within the proposed building footprint and three borings throughout the exterior parking/hardscape areas;

• Laboratory testing of soils retrieved from our borings; and

• Preparation of a written report to include the following:

o Discussion of the subsurface conditions encountered during our exploration program;

© 2009 Kleinfelder Page 3 of 27 May 13, 2009 o Conclusions and recommendations regarding shallow and/or deep foundation types;

o Pavement recommendations for roadway and parking lot improvements;

o Physical properties and characteristics of the soils underlying the site, including indicators of groundwater;

o Excavation and site earthwork, including site preparation, and the procedures for the placement and compaction of fill;

o Allowable soil bearing for buildings;

o Estimated settlements for a shallow foundation system;

o Recommended footing embedment;

o Recommendations for cut/fill slopes;

o Lateral earth pressures on cast-in-place site retaining walls and embedded building walls as well as resistance against sliding of embedded walls, considering passive pressure and friction on the base, as applicable;

o Utility trench backfill;

o Subdrainage requirements for buildings;

o Base rock section for building slabs; and o Seismic hazard considerations, such as ground motions, earthquake initiated landslides, liquefaction analysis, estimated seismically induced ground settlement, lateral spreading evaluations, and appropriate geotechnical data for determining the seismic soil profile types, as described in OSSC 2008, not including a site specific seismic hazard evaluation.

© 2009 Kleinfelder Page 4 of 27 May 13, 2009

2.0 FIELD EXLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

The purpose of our geotechnical field exploration was to evaluate subsurface conditions for the proposed development and to collect soil samples for laboratory testing. Our field exploration was performed on February 25, 2009 and consisted of six borings within the project area. Three borings were drilled within the building footprint to depths between 31.5 to 41.5 feet below the existing ground surface. Three additional borings were advanced throughout the proposed exterior improvements and ranged in depth from 6.5 to 8.5 feet below the existing ground surface. The approximate locations of the soil borings are shown on Figure 2, Site Plan. The boring logs and a description of the Unified Soil Classification System (USCS) used to classify the site soils encountered are presented in Appendix A.

Four of the six borings were completed with a trailer-mounted drill rig equipped with

4-inch diameter solid-flight augers. The drill rig was supplied and operated by our subcontractor, Van De Hey Soil Sampling of Forest Grove, Oregon. The two remaining borings were advanced by a member of our engineering staff using a 4-inch diameter hand-auger. The two hand-augers were performed in lieu of truck-mounted borings due in part to soft ground conditions (wet/saturated grass-covered ground) at the time of our field exploration.

A member of our engineering staff logged the soil conditions encountered in the borings and collected soil samples for laboratory testing. The soils were classified in general accordance with the USCS with certain other terminology, such as the relative density or consistency of the soil deposits, in general accordance with current local engineering practice. In addition, a torvane shear device and a pocket penetrometer were used to check soil stiffness of relatively undisturbed soil samples and to assist with our field classifications.

Driven samples were obtained from the borings using a Standard Penetration Test

(SPT) sampler (2-inch outside and 1.4-inch inside diameter) and Shelby sampler (3-inch outside and 2.9-inch inside diameter). The SPT sampler was generally driven

18 inches into undisturbed soil using a 140-pound hammer with a 30-inch drop (double-wrap cathead method). The number of blows necessary to drive the sampler at 6-inch

© 2009 Kleinfelder Page 5 of 27 May 13, 2009 intervals was recorded for each sample. The blows recorded in the last 12 inches are termed the blow count, N60, and is noted on the boring logs in Appendix A.

Soil samples obtained from the borings were packaged, sealed in the field to reduce moisture loss and disturbance, and transported to our laboratory for testing. At completion, the borings were backfilled with hydrated bentonite chips. Borings completed within the exiting parking lot were additionally capped with concrete to match the surrounding pavement grade.

2.2 LABORATORY TESTING

2.2.1 General

Geotechnical laboratory testing was performed on representative bulk and driven samples to substantiate field classifications and to provide soil parameters for engineering analysis. The physical characteristics of the samples were noted in the field and the soil classifications were modified on the boring logs, where necessary, based on our review of the test results. The laboratory testing program consisted of dry unit weight, moisture content, expansion, consolidation testing, and standard classification tests including visual-manual examination and Atterberg limits.

The results of the laboratory tests, as well as a description of the laboratory testing procedures, are presented in Appendix B.

© 2009 Kleinfelder Page 6 of 27 May 13, 2009

3.0 SITE CONDITIONS

3.1 REGIONAL GEOLOGIC SETTING

Based on our review of the Geologic Framework of the Willamette Lowland Aquifer

System, Oregon and Washington (USGS, 1998), the site is located at the southern region of the Willamette Lowland physiographic subprovince, a geologic depression that extends from near Eugene, Oregon to the Lewis River in southern Washington.

The Willamette Lowland is bounded on the west by the Coast Range and on the east by the considerably higher Cascade Range.

The Corvallis vicinity is generally underlain by alluvial and lacustrine terraces consisting of silt, sand, and gravels deposited primarily by Pleistocene-age glacial-outburst floods associated with the Missoula Flood events. The Missoula Floods inundated the

Willamette Lowland as far south as Eugene several times towards the end of the last ice age as result of periodic rupturing of the ice dam of Glacial Lake Missoula. Locally, the alluvial and lacustrine terrace deposits can be traced to the Willamette River to the

Corvallis foothills. The Corvallis foothills north of the site are composed primarily of sedimentary and volcanic rock units.

3.2 SURFACE CONDITIONS

Surface conditions across the site generally consist of low-lying grasses, shrubs, trees, hardscape, curbs and asphalt pavements. An existing power transformer supported on a concrete base is located in the southerly end of the proposed building footprint.

Where grasses and landscaped areas are located, the average topsoil thickness was approximately 8 to 12 inches as measured in the borings. The existing pavements encountered in our borings generally consist of about 6 inches of asphaltic concrete over 7 to 8 inches of aggregate base.

The site is nearly flat and slopes gently towards the south.

3.3 SUBSURFACE CONDITIONS

Logs summarizing the subsurface conditions encountered in the borings are presented in Appendix A. Approximate exploration locations are shown on Figure 2, Site Plan. A table of the terminology used to describe soil is provided in the attached Table 1.

© 2009 Kleinfelder Page 7 of 27 May 13, 2009

The soil conditions observed during the subsurface investigation are relatively consistent across the site and are described in the following paragraphs.

Silty CLAY and CLAY (CL - CL/CH) – The soils encountered below the existing asphalt and topsoil generally consist of over consolidated, silty clay and clay soils to depths of approximately 16 to 18 feet below the existing ground surface. The plasticity of these soils is generally medium to high and the consistency of these soils is generally medium stiff. SPT N-values ranged between 4 and 8 blows per foot. The moisture content of these soils at the time of our field exploration was well over optimum for compaction and varied between 29 and 39 percent.

Based on our review of site conditions, the near surface soils may be locally disturbed by previous farming activities and/or surface improvements (underground utility, pavement, and hardscape construction). The near surface soil may also be locally saturated due to rain infiltration and local irrigation practice.

SILT with Sand and Gravel (ML) - The materials encountered between approximately

16 and 24 feet generally range between stiff clayey silt with sand and gravel to dense gravelly sand with silt and trace cobbles. These materials are generally low to medium plasticity and fine to medium grained. The gravels are fine to coarse grained and appear to be locally nested. SPT N-values varied between 24 and 46 blows per foot.

This unit was not encountered in Boring B2. The moisture content of these soils was about 13 percent in our moisture testing of these soils from Boring 3.

Very Stiff SILT (ML) - The soils encountered below approximately 24 feet to the bottom of our borings generally consist of very stiff sandy silt, silt, and clayey silt soils. The plasticity of these soils generally ranged from non-plastic to medium plasticity. Medium plasticity clayey silt soils generally predominate below depths of approximately 27 to 30 feet. SPT N-values varied between 24 and 35 blows per foot. The moisture content of these soils generally varied between 50 and 70 percent. Where encountered, the sands were generally fine grained and low to non-plastic.

3.3.1 GROUNDWATER

Groundwater was encountered at depths between 1 and 3 feet in our borings located within the proposed building footprint (Boring B1 through B3) and our two hand-auger

© 2009 Kleinfelder Page 8 of 27 May 13, 2009 borings in the northwestern portion of the site (Hand-Auger HA-1 and HA-2).

Groundwater was not encountered in Boring B4 which was advanced to a depth of 6.5 feet below the existing ground surface.

Water seepage was observed within the bottom of the aggregate base layer of Boring

B1. In addition, an underground utility vault in vicinity of Boring B2 was partially filled with groundwater at the time of our field study. Although the shallow groundwater observed at the site may be a result of a perched water table conditions, we anticipate that groundwater, be it perched or staticy, may impact construction/excavation activities at the site. This will occur particularly where earthwork operations are performed during wet weather periods. We anticipate that groundwater levels will fluctuate due to seasonal variations in rainfall and related surface water penetration.

3.4 EXPANSIVE SOILS

Expansive soils are characterized by their ability to undergo significant volume changes

(shrink or swell) with changes in moisture content. Changes in soil moisture content can result from many factors, including precipitation, landscape irrigation, utility leakage, roof drainage, perched groundwater, drought, etc., and may result in harmful settlement or heave of structures or concrete slabs supported on grade.

A one-dimensional swell test was performed on a soil sample retrieved from Boring B3 at a depth of 3.5 feet below existing grades. Based on our review of the soil conditions encountered at the site and the results of our one-dimensional swell test, the near-surface soils have a moderate potential for expansion. Although the shrink potential of the near surface soils is not anticipated to impact the building foundations, lightly loaded concrete improvements (i.e. sidewalks, concrete pavements, and slabs-on-grade) that are directly underlain by the onsite expansive soils may be impacted by shrink-swell behavior.

© 2009 Kleinfelder Page 9 of 27 May 13, 2009

4.0 SEISMIC HAZARDS AND FAULTING

4.1 SEISMIC HAZARDS

We have reviewed the site with respect to the potential presence of seismic hazards.

These hazards include seismic ground shaking, fault surface rupture, and liquefaction.

The following sections discuss these hazards and their potential at the project site.

4.1.1 Seismicity

The seismic probabilities of the site were analyzed using the 2003 NEHRP Seismic

Design Provisions, the database used by IBC-2006 and the 2007 Oregon Structural

Specialty Code. The database was developed by the USGS. This analysis method takes into account the historical seismicity of the western Oregon region and the greater

Pacific Northwest. The maximum considered earthquake (MCE) is an M8.5 or greater tectonic plate subduction earthquake occurring off the coast of Oregon and Washington within the Cascadia Subduction Zone. Research shows that there has been a series of subduction zone events over the past 10,000+/- years with an average return period of

300 to 700 years. Recent, ongoing research continues to support these estimates

(Nelson, et al, 2005). The last major event is believed to have occurred in 1700 (308 years ago). There is now a growing probability that another Subduction zone earthquake will occur within the next 50 years. Subduction zone earthquakes are the most damaging seismic events. Other possible seismic events are also included in the

USGS database cited above, but they only have a small effect on the overall earthquake hazard at the site.

4.1.2 Fault Surface Rupture

The project area is considered to be seismically active, as is most of the Willamette

Valley of Oregon. Based on our review of the geologic information available in our files, the subject site is not underlain by known active or potentially active faults. Therefore the potential for ground rupture due to faulting at the site is low.

4.1.3 Liquefaction Potential

Soil liquefaction can occur in loose, saturated cohesionless sandy, or silty soils resulting in a loss of strength due to strong ground shaking from an earthquake. Liquefaction is

© 2009 Kleinfelder Page 10 of 27 May 13, 2009 defined as a decrease of the shearing resistance of a cohesionless and some low plasticity soils due to the increase of excess pore water pressure; it involves a temporary transformation of the material into a fluid. In general, liquefaction can result in ground settlement, which may not be uniform; foundation bearing capacity failure;

and lateral spreading of the ground. Structures impacted by liquefaction may undergo large total and differential settlements which may cause damage and possibly failure.

Due to the type, consistency, and plasticity of soils encountered in our explorations the potential for liquefaction induced settlement at the subject site is low.

4.2 SEISMIC ACCELERATION AND SOIL PROFILE

OSSC 2008 requires that the facility be designed to sustain the maximum considered earthquake. As stated previously, the geologic units below the proposed structure generally consists of Pleistocene-age flood deposits consisting of stiff to very stiff clays and silts and interbedded dense gravelly sands. Based on our evaluation of the soils described in the boring logs and other published geologic information in the project vicinity, the seismic soil profile for the upper 100 feet beneath the site would likely be considered a stiff soil profile, with the Site Class defined as “D.” The Peak Horizontal

Acceleration (PGA) for the maximum considered earthquake for the site vicinity, based on IBC-2006, is 0.26g (2 percent probability of exceedance in 500 years, multiplied by a factor of 2/3).

We recommend the generalized (IBC-2006) response spectra be used in design of the structures using the following latitude and longitude coordinates (North America Datum

27) for the site in determining the IBC-2006 seismic factors:

Latitude: 44.565°N

Longitude: -123.290°W

© 2009 Kleinfelder Page 11 of 27 May 13, 2009

5.0 CONCLUSIONS AND RECOMMENDATIONS

Based on the results of the field exploration, laboratory testing, and our evaluations, 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.

5.1 SITE EARTHWORK

5.1.1 General

Site preparation and earthwork operations should be performed in accordance with applicable codes and local ordinances, and the earthwork recommendations discussed herein. All reference to maximum dry density is established in accordance with

American Society for Testing and Materials (ASTM) ASTM D 1557.

All site preparation and fill placement activities should be observed and tested by a representative of our firm. We recommend that the construction areas be cut to grade then observed by a representative of our firm to evaluate the subgrade soil conditions and make recommendations for removal of any soils and replacement with compacted fill.

5.1.2 Site Preparation

Areas that will receive structural fill, pavement, or structures should be stripped to a depth that is sufficient to remove existing asphalt, vegetation, significant roots larger than ½-inch in diameter and any other deleterious materials encountered. We anticipate that the required stripping depths will be 8 to 12 inches in vegetated areas.

The stripping operation should expose a firm, non-yielding subgrade that is free of large voids, organics, and deleterious materials. However, greater stripping depths may be required in localized areas. Old foundations, slabs, and asphalt concrete pavements should also be removed from these areas. The existing base rock may remain in place if it meets the gradation requirements for base rock, is underlain by suitably stiff subgrade conditions, and forms part of the pavement rock section to meet the minimum thickness requirements presented in Section 5.8, Pavement Recommendations.

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.

© 2009 Kleinfelder Page 12 of 27 May 13, 2009

Unwanted soil and materials should be exported from the site. Unless stated otherwise, exposed subgrades to receive new fill should be proofrolled in accordance with Section

5.1.4 to identify unsuitable subgrades areas prior to raising site grades.

Existing underground structures, abandoned utilities, and associated trench backfill material within the footprint of the new building, plus a lateral distance of 5 feet, should be removed and replaced with engineered fill. Where an existing utility will remain in service below the proposed structure(s), the existing utility should be encased in structural concrete and associated trench backfill materials should be removed and replaced with structural fill. The structural engineer should review the structural loading on existing utilities to remain in-place below the proposed improvement and evaluate whether or not the existing utilities to remain can tolerate the anticipated building loads and concrete encasement. The concrete encasement (if required) should be designed by the structural engineer. Existing utilities may be abandoned in-place provided they are 4 inches or less in diameter, are overlain with well compacted backfill (as evaluated by our field representative at the time of construction), and are completely in-filled with cementicous grout. Grout, where used, should be pumped into the utility conduit starting at the lowest point of the utility and filling upward throughout the conduit.

5.1.3 Building Pad Preparation

In general, we recommend the upper 24 inches of material within the building pad, and extending to a minimum 5 feet beyond the building pad, consist of imported, non-expansive granular fill soils that are placed and compacted in accordance with the recommendations presented herein. The purpose of the 24-inch thick section of granular fill material is to reduce the potential for shrink/swell behavior beneath the building pad.

Following the stripping of topsoil and removal of existing surface elements (pavement, old foundations, etc.), preparation of the building pad should consist of removing the existing soils to a minimum depth of 18 inches below finished subgrade. This depth of over-excavation may be reduced accordingly if site grades are raised within the building pad (i.e. if site grades are raised by 1 foot from existing grades, then the depth of over-excavation may reduced by 1 foot accordingly). Additional over-excavation may be required in localized soft spots.

© 2009 Kleinfelder Page 13 of 27 May 13, 2009

Once these soils have been removed, the exposed subgrade should be proofrolled with a fully loaded 10 to 12 yard dump truck or other suitably loaded rubber-tired construction vehicle (see Section 5.1.4 Proofrolling). Where proofrolling operations indicate suitable subgrade conditions, the bottom of the excavation should be cut clean, relatively smooth, and left in a relatively undisturbed condition. Isolated areas of weak soil encountered during the proofrolling operation should be scarified, dried and compacted, or else over-excavated and backfilled with compacted structural fill as discussed in Section 5.1.5, Structural Fill. A representative of our firm should be onsite during proofrolling operations to evaluate the subgrade soil conditions and make recommendations for removal of any soils and replacement with compacted fill.

Once a suitable excavation bottom has been achieved, the excavation should be backfilled with imported granular aggregate base material meeting the requirements presented in Section 5.1.5, Structural Fill. The aggregate base backfill should be placed in 8-inch loose lifts, moisture conditioned to within 2 percent of optimum moisture content and compacted to a minimum of 92 percent of the maximum dry density (ASTM D 1557) to finished subgrade elevation.

We anticipate that earthwork operations within the building pad may encounter soils that are over optimum moisture content at the time of construction. Since fine-grained soils (silts and clays) that are over optimum can be potentially sensitive to construction traffic, and therefore deflect and pump under repeated wheel loads, we recommend that excavations within the building pad be completed with relatively light-duty tracked equipment (Catarpillar D4 dozer or equivalent) or tracked excavator. In general, excavations completed with a tracked excavator operating from outside the building pad are favored over the operation of excavation equipment within the building pad area.

Dump trucks should not enter the excavation area during removal of the existing building pad soils.

Shallow groundwater may also be encountered during construction which may require the use of temporary sump pits to remove water from the excavation(s). Since groundwater is more likely to be encountered during wet weather periods, we recommend that earthwork activities, including building pad preparation, trenching, backfilling, and pavement construction be completed during the dry summer months to help avoid potential costly dewatering and/or special handling of wet soil conditions.

© 2009 Kleinfelder Page 14 of 27 May 13, 2009

5.1.4 Proofrolling

Following stripping and subgrade preparation, and prior to placement of structural fill or base course, we recommend that the site be proofrolled with a fully loaded 10 to 12 yard dump truck or other suitably loaded rubber-tired construction vehicle. Any areas that pump, rut, or appear soft or muddy should be scarified, dried, and compacted, or else over-excavated and backfilled with compacted structural fill as discussed below. If significant time passes between completion of subgrade preparation and commencement of other construction activities, or if significant traffic has been routed across the site, we recommend that the site be similarly proofrolled before placement of base rock or paving. A representative of our firm should observe this operation

5.1.5 Structural Fill Materials

Structural fill should only be placed on a subgrade that has been prepared in accordance with the preceding recommendations. The expansive clay soils encountered at the site are not generally suitable for reuse as structural fill. The in-situ moisture content of the near surface soil was about 26 to 38 percent, well over the optimum moisture content. The moisture content of the near surface soils can be expected to vary depending on the time of year and recent weather conditions.

We recommend that structural fills be placed in horizontal lifts not exceeding 8 inches in loose thickness, moisture conditioned to within 2 percent of optimum moisture content, and compacted to a minimum of 92 percent of the maximum dry density (ASTM D1557)

Structural fill should consist of non-expansive, well-graded, crushed rock meeting the gradation requirements of ODOT 1½-inch or ¾-inch minus base aggregate. Structural fill should be free of organic material and debris, and contain no particles greater than 3 inches nominal diameter. 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. For this reason, we generally recommend that materials used as structural fill contain less that 5 percent passing the No. 200 sieve.

The silt/clay fraction of the near-surface soils is moisture sensitive, and during wet weather, native on-site soils may become unworkable because of excess moisture

© 2009 Kleinfelder Page 15 of 27 May 13, 2009 content. In order to reduce moisture contents, some discing and drying of native soils may be required, particularly where existing grades are to be scarified and recompacted prior to receiving new fill. If moisture contents of the near surface soils cannot be reduced by air drying it may be necessary to grade the site with granular soils that do not contain more than 5 percent passing the No. 200 sieve (wet sieve analysis). In this case the recommendation presented in Section 5.1.6, Wet Weather Construction should be followed.

5.1.6 Wet Weather Construction Considerations

Much of the near surface soils are fine-grained or contain a substantial fines portion, and are therefore sensitive to moisture during handling and compaction. Proceeding with site earthwork operations using these soils during wet weather could add significant costs to the project. We therefore recommend that, if possible, site clearing, preparation, and earthwork be completed during an extended period of warm, dry weather when soil moisture can be controlled by aeration.

Due to the potential for near surface ground water during wet weather periods (ground water was encountered from 1 to 3 feet below the existing ground surface during our field exploration), site grading should be completed during dry weather periods to avoid disturbing the saturated site soils and help reduce the need for dewatering open excavations.

During or subsequent to wet weather, drying or compacting the near surface on-site soils will be difficult. It will be necessary to amend the on-site soils, or import granular materials for use as structural fill, and it may be necessary to install granular working pads and/or haul roads to support construction traffic. A 12-inch granular working pad may be sufficient for light construction traffic. For heavy construction traffic, the granular working pad thickness should be increased to at least 24 inches. The granular working pad material should consist of well-graded ¾-inch minus or 1 ½-inch minus crushed rock. A woven geotextile fabric, such as Mirafi 500X, should be placed under working pads to reduce the risk of contamination of the crushed rock by subgrade silts and clays. Delays in site earthwork activities should be anticipated during periods of heavy rain. In addition, site clearing and stripping activities will expose “tender” subgrades that are subject to disturbance (severe pumping and loss of equipment

© 2009 Kleinfelder Page 16 of 27 May 13, 2009 support) if the contractor allows construction traffic on the subgrade while wet conditions exist.

If construction does occur during wet weather, some steps to reduce the risk of soil disturbance may be taken as follows:

a) Use a smooth-blade bucket, operating from a bench above subgrade level, to strip the soft and wet surface material and locally over-excavate unsuitable soils. Probe the subgrade to confirm that soft/unsuitable soils were removed.

b) Avoid standing water in low areas and wheel ruts and grade the exposed subgrade with a smooth-edge bucket to facilitate runoff of surface water.

c) Do not allow construction equipment to operate directly on the exposed subgrade and cover and protect the approved subgrade immediately.

Local ordinances may require contractors to mitigate the tracking of fines from the site to improved streets, and the use of silt fences and other means to control erosion and sediment transport during construction is recommended.

5.2 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” and on-site spoils which should not be used as trench backfill except in landscape areas. 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.

5.3 FOUNDATION RECOMMENDATIONS

The assumed building foundation loads used to develop the recommendations included below are limited to column loads not exceeding 120 kips and wall loads not to exceed

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3 to 4 kips per lineal foot. Slab loads are unknown; but we understand the slab will support foyer, office, and classroom space.

5.3.1 Footing Preparation

We recommend that all footing excavations be trimmed neat and footing subgrades carefully prepared. Any loose or softened material should be removed from the footing excavation prior to placing rebar and/or concrete. Due to the potential for clay soils to become unstable during construction activities, site foundations should be underlain by about 3 to 4-inches of lightly compacted, well-graded ¾-inch minus or 1 ½-inch minus crushed rock. Therefore, footing subgrades do not need to be scarified and recompacted. The crushed rock should be compacted with a minimum of three passes of a vibratory base plate compactor with a minimum operating centrifugal force of 6,000 pound. We recommend that the footing excavations be observed by a representative of our firm 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.

All footings should be extended in depth as necessary so that no existing or proposed utility trenches will extend below a plane having a downward slope of 2H:1V from a line

9 inches above the bottom edge of the closest footing. In addition, no parallel trenches should be within 18 inches from the closest edge of the footing. New footings should not be excavated below the bottom of adjacently located existing foundations.

5.3.2 Frost Penetration/Footing Embedment Depths

We recommend that all footings be founded a minimum of 18 inches below the lowest adjacent exterior grade to lie below maximum seasonal frost penetration depths.

5.3.3 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 prepared as recommended herein be proportioned for a maximum allowable bearing pressure of

2,500 pounds per square foot (psf). This applies to dead plus live loads. The allowable bearing pressure can be increased by one-third for short term loads such as those due to wind and seismic forces.

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Please note that the above recommended bearing pressures are net values, and the weight of concrete in the portions of the foundations that extend below grade can be neglected in proportioning the foundations.

5.3.4 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 subsurface conditions, we estimate the static settlement to be less than 1-inch. The potential static differential settlement between two adjacent columns (approximate 40 foot center to center spacing) should be less than 1/2-inch.

5.3.5 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 these recommendations, the allowable frictional resistance may be computed using a coefficient of friction of 0.35 applied to vertical dead-load forces. In addition, the design value for passive pressure should not exceed a value of

250d psf (where “d” is the depth of the embedment in feet), due to the large amounts of movement necessary to mobilize full passive resistance. Passive pressure and base friction can be combined without reduction to resist lateral loads. However, the top 12 inches of soil should not be used in calculating passive resistance since construction and post-construction activities often disturb this upper material.

5.4 RETAINING WALLS

Retaining wall foundations should have a minimum width of 4 feet or greater depending upon wall stability analyses performed by the retaining wall designer. Foundations should be embedded at least 18 inches below the lowest adjacent grade or to the depth necessary to provide adequate factors of safety against sliding and overturning as determined by the retaining wall designer, whichever is greater. Reinforcement should be provided as required by the wall designer for load carrying purposes.

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Footings can be designed using an allowable soil bearing pressure of 2,000 pounds per square foot (psf), for dead loads plus long-term live loads. These design values can be increased by one-third for short term loads such as those due to wind and seismic forces.

5.4.1 Lateral Earth Pressures

Active and At-Rest Pressures

Lateral pressures acting against retaining walls can be calculated assuming that the backfill soils act as a fluid. The equivalent fluid weight (EFW) value depends on allowable wall movement. Walls which are free to rotate at least 0.2 percent of the wall height can be designed for the active EFW. Walls which are restrained at the top or are sensitive to movement and tilting should be designed for the at-rest EFW. The recommended active EFW is 35 pounds per cubic foot (pcf) and the recommended at-rest EFW is 55 pcf. These values assume: a triangular distribution; level backfill;

backfill with on-site or imported, non-expansive granular soils (SP, SM, GC, GM); and that the backfill is well drained.

5.4.2 Drainage

Seasonal groundwater levels and perched groundwater following rain and other precipitation events may be expected to fluctuate up to near the existing ground surface. Due to the presence of shallow groundwater at the site, perimeter foundation drains are recommended. The foundation subdrainage system should include a minimum 4-inch diameter perforated pipe in a pea gravel or drain rock envelope.

A non-woven geotextile filter fabric, such as Mirafi 140N or equivalent, should be used to completely wrap the pea gravel envelope, separating it from the native soil and footing backfill material. The invert of the perimeter drain lines should be placed below the base slab. Also, the subdrainage system should be sealed at the ground surface and the finished ground surface should be graded to drain surface water away from the building. 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. This water should be

© 2009 Kleinfelder Page 20 of 27 May 13, 2009 conveyed away from the building with the use of continuous (non-perforated) drain-pipe connections, and not be allowed to enter the bearing soils.

5.5 PREPARATION FOR INTERIOR CONCRETE SLAB

We recommend that conventional, slab-on-grade floors be underlain by very low to non-expansive compacted fill prepared in accordance with Section 5.1.3, Building Pad

Preparation. For floor slabs supported on subgrades and aggregate base that are prepared in accordance with the recommendations presented herein, the floor slab may be designed for a modulus of subgrade/base rock reaction (k) of 150 pounds per cubic inch.

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.

Subsurface moisture and moisture vapor naturally migrate upward through the soil and, where the soil is covered by a building slab or pavement, this subsurface moisture will migrate through the floor slab and potentially impact impervious or moisture-sensitive floor coverings such as tile, carpet, linoleum, or varnished hard wood. To reduce the impact of this subsurface moisture and the potential impact of future introduced moisture (such as landscape irrigation or precipitation), the architect, structural engineer, and/or owner should consider the placement of a plastic membrane (vapor retarder) below the floor slab. This vapor retarder typically consists of visqueen or polyvinyl plastic sheeting at least 15 mil in thickness. The aggregate subbase typically consists of 6 inches of clean crushed rock material placed and compacted over a properly prepared subgrade. 100 percent of the aggregate subbase should pass the 1-inch sieve and have less than 5 percent passing the No. 200 sieve (washed sieve analysis). If used, we recommend the aggregate subbase layer be compacted to at least 92 percent of the maximum dry density as determined by the modified Proctor test method (ASTM D 1557).

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5.6 EXCAVATIONS

Based on our review of the soil conditions encountered during our field exploration, we anticipate that excavations at the site may be accomplished using conventional earthmoving equipment.

Although the native soils excavated during our site investigation will typically stand on near vertical slopes for short periods of time, they may collapse suddenly and without warning. Any excavations deeper than 4 feet that will involve personnel within the excavation should be adequately sloped or shored in accordance with Oregon OSHA requirements. Temporary excavation sloping is generally the prerogative of the contractor, and our suggestions are only for the design to use for 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: Vertical) provided groundwater is not encountered. If sand is encountered within the excavation, we recommend that the excavation be sloped back at no steeper than 2H:1V. It should be anticipated that shallow, perched groundwater may be encountered within a few feet of the surface throughout the wet season. Temporary cuts that encounter groundwater should be shored and adequately braced, or provisions made for dewatering the excavations.

During dry summer weather the water level will drop, and may not be encountered in utility excavations. 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) and that permanent structures are not near the top of the slope. 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

Oregon. 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).

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If groundwater is encountered within the depths required for installation of utilities, dewatering of trench excavations should be possible using a system of ditches directing water inflow to a sump where water can be removed by a pump. During wet weather, earthen berms or other methods may be used to prevent surface runoff water from entering excavations. De-watering is typically the responsibility of the contractor, and our statements in this regard are for the owner’s planning purposes only. All runoff water and groundwater encountered within the excavation(s) should be collected and disposed of outside the construction limits.

5.7 PERMANENT SLOPES

No permanent cut or fill slopes are anticipated for this project.

5.8 PAVEMENT RECOMMENDATIONS

General

We understand that the proposed parking lot will be paved with asphalt concrete and will be generally used for passenger cars and light trucks with occasional heavy trucks.

Subgrade

The subgrade for the proposed access drive pavements consists typically of medium stiff silty clay and clay soils. Based on our experience, we are providing pavement sections recommendations, provided the subgrade is prepared as recommended below.

The subgrade should be checked for firmness and suitability by proofrolling and/or using a hand probe after scarifying and recompacting the upper 12 inches of subgrade as described above in the Site Preparation section. Any soft/weak or very wet areas disclosed in the underlying subgrade should be improved as recommended in the Site

Preparation section. However, if construction proceeds during the wet season and scarifying the subgrade is not feasible, we also recommend that the subgrade be prepared as recommended in Section 5.1.6, Wet Weather Construction Considerations, and that woven geotextile fabric such as Mirafi 500X, or equivalent, be placed on the excavated subgrade before placement of base rock to provide subgrade strength and prevent contamination of base rock from the subgrade silts.

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Base Course

We recommend that a minimum of 12 inches of crushed rock base be used in the heavy truck drive areas, including 10 inches of 1½-inch minus crushed base rock capped with 2 inches of ¾-inch minus crushed rock leveling course.