Geotech Report_PBS.pdf

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Geotechnical Engineering Report Willapa Wildlife Refuge

Long Beach, Washington

Prepared for:

Ms. Angela Hansen, Assistant Chief

CTA Architects Engineers

800 W. Main Street, Suite 800

Boise, Idaho 83702

June 29, 2017

PBS Project No. 73308.000

©2017 PBS Engineering and Environmental Inc.

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Geotechnical Engineering Report

Willapa Wildlife Refuge

Long Beach, Washington

Prepared for:

Ms. Angela Hansen, Assistant Chief

800 W. Main Street, Suite 800

Boise, Idaho 83702

Prepared by:

Tony Rikli, PE (OR)

Project Geotechnical Engineer

Reviewed by:

Ryan White, PE, GE

Geotechnical Discipline Lead

6/29/2017

CTA Architects Engineers

Willapa Wildlife Refuge

Long Beach, Washington i

TABLE OF CONTENTS

1 INTRODUCTION

1.1 General

1.2 Purpose and Scope

1.2.1 Literature and Records Review

1.2.2 Subsurface Explorations

1.2.3 Soils Testing

1.2.4 Geotechnical Engineering Analysis

1.2.5 Report Preparation

1.3 Project Understanding

2 SITE CONDITIONS

2.1 Surface Description

2.2 Geologic Map Review

2.3 Subsurface Conditions

2.4 Groundwater

2.5 Infiltration Testing

3 CONCLUSIONS AND RECOMMENDATIONS

3.1 Geotechnical Design Considerations

3.2 Seismic Design Considerations

3.2.1 Code-Based Seismic Design Parameters

3.2.2 Liquefaction Potential

3.2.3 Existing Non-Liquefiable “Crust” and Shallow Spread Footings

3.3 Shallow Foundations

3.3.1 Minimum Footing Widths / Design Bearing Pressure

3.3.2 Footing Embedment Depths

3.3.3 Footing Preparation

3.3.4 Lateral Resistance

3.3.5 Grade Beams

3.4 Floor Slabs

3.5 Pavement Design

3.5.1 Asphalt Concrete

4 CONSTRUCTION RECOMMENDATIONS

4.1 Site Preparation

4.1.1 Proofrolling/Subgrade Verification

4.1.2 Wet/Freezing Weather and Wet Soil Conditions

4.2 Excavation

4.3 Slopes

4.4 Structural Fill

4.4.1 On-Site Soil

4.4.2 Imported Granular Materials

4.4.3 Crushed Aggregate Base

4.4.4 Utility Trench Backfill

5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS

ii

6 LIMITATIONS

7 REFERENCES

SUPPORTING DATA

TABLES

Table 1. Infiltration and Laboratory Test Results Table 2. 2015 IBC Seismic Design Parameters Table 3. Minimum AC Pavement Sections

FIGURES

Figure 1 Vicinity Map

Figure 2 Site Plan

APPENDICES

APPENDIX A: Field Explorations

Table A-1 Terminology Used to Describe Soil

Table A-2 Key to Test Pit and Boring Log Symbols

Figures A1–A4 Logs for Borings B1 through B3, INF-1

APPENDIX B: Laboratory Testing

Figure B1 Atterberg Limits Test Results

Figure B2 Summary of Laboratory Data

1 INTRODUCTION

1.1 General

PBS Engineering and Environmental Inc. (PBS) previously provided geotechnical engineering services for the

Willapa Wildlife Refuge development located in Long Beach, Washington (site), and presented the results in a

Geotechnical Data Review letter dated February 6, 2017 (PBS, 2017). This report presents results of PBS’ geotechnical engineering design services for the proposed new visitor center and maintenance building at the site. The general site location is shown on the Vicinity Map, Figure 1. The locations of PBS’ explorations in relation to existing and proposed site features are shown on the Site Plan, Figure 2.

1.2 Purpose and Scope

The purpose of PBS’ services was to develop geotechnical design and construction recommendations in support of the planned new visitor center and maintenance building. This was accomplished by performing the following scope of services.

1.2.1 Literature and Records Review

PBS reviewed various published geologic maps of the area for information regarding geologic conditions and hazards at or near the site. PBS also reviewed previously completed reports for the project site and vicinity.

1.2.2 Subsurface Explorations

Three borings were advanced to depths up to 41.5 feet below the existing ground surface (bgs) within or adjacent to the proposed new building footprints. The borings were logged and representative soil samples collected by a member of the PBS geotechnical engineering staff. The approximate boring locations are shown on the Site Plan, Figure 2. The interpreted boring logs are presented as Figures A1 through A4 in

Appendix A, Field Explorations.

1.2.3 Soils Testing

Soil samples were returned to our laboratory and classified in general accordance with the Unified Soil

Classification System, Visual-Manual Procedure. Laboratory tests included natural moisture contents, grain-size analyses, and Atterberg limits. Laboratory test results are included in the boring logs in Appendix A, Field

Explorations; and in Appendix B, Laboratory Testing.

1.2.4 Geotechnical Engineering Analysis

Data collected during the subsurface exploration, literature research, and testing were used to develop site-specific geotechnical design parameters and construction recommendations.

1.2.5 Report Preparation

This Geotechnical Engineering Report summarizes the results of our explorations, testing, and analyses, including information relating to the following:

• Field exploration logs and site plan showing approximate exploration locations

• Laboratory test results

• Groundwater levels and considerations

• Liquefaction potential

• Shallow foundation recommendations:

o Minimum embedment o Allowable bearing pressure o Estimated settlement o Sliding coefficient

• Earthwork and grading, cut, and fill recommendations:

o Structural fill materials and preparation o Utility trench excavation and backfill requirements o Slab and pavement subgrade preparation o Wet weather considerations

• Seismic design criteria in accordance with the 2015 International Building Code (IBC) with State of

Washington amendments

• Recommended pavement section thickness

1.3 Project Understanding

PBS understands that development plans are currently in their conceptual stages. However, based on the site layout concept provided by CTA Architects Engineers on May 16, 2017, development will include a new two-story administration building/visitor center with associated parking area, drive lanes, gathering plaza, trail connections, and a potential overlook. A new one-story maintenance building will be constructed southeast of the proposed administration building/visitor center.

2 SITE CONDITIONS

2.1 Surface Description

The subject property is located east of the city of Long Beach, Washington, within the Willapa Wildlife Refuge.

The proposed development area (site) is surrounded by a forested area and is accessed through Rekola Road to the southwest. In general, the site lies atop a large hill where elevations gradually change from approximately 70 feet at its peak to 10 feet amsl to the southeast, southwest, and northwest. The site area is generally flat with elevations varying from approximately 48 feet to 70 feet (WGS84 EGM96 Geoid). The site is currently occupied by two maintenance buildings and a grass field. Much of the northeastern portion has been graded and sloped, and brush and several tree clusters have been removed.

2.2 Geologic Map Review

Published geologic maps of the area (Wells, 1989) show the site is mantled with Quaternary semi-consolidated fine to coarse sand known as the Sand of Mountain Springs Formation. This formation may represent remains of an older barrier beach and dune field and is commonly yellow-orange. Subsurface conditions observed in our explorations are consistent with those described and depicted in the geologic maps covering the site.

2.3 Subsurface Conditions

The site was explored by drilling four borings, designated B-1 through B-3 and INF-1, to depths of up to 41.5 feet bgs. The drilling was performed by Western States Soil Conservation, Inc., of Hubbard, Oregon, using a track-mounted CME-850 drill rig and mud-rotary and hollow-stem auger drilling techniques.

PBS has summarized the subsurface units as follows:

FILL: gravel (GP);

silt (ML)

Soft to stiff silt with organics and poorly graded gravel fill was observed in boring B-1 and

B-3 to depths of 9.5 feet and 2.5 feet bgs, respectively. The silt was generally brown-gray and varied in consistency/relative density with N-Values of 2 to 3 blows per foot (bpf).

The fine-grained portion of the samples was generally low plasticity with moisture contents varying from 36 to 51 percent. Gravel fill varied from fine to coarse grained and subangular to angular.

SAND OF Below the fill in B-1 and B-3 and at the surface in B-2 and INF-1, poorly graded GRAVEL

FILL: gravel (GP);

silt (ML)

Soft to stiff silt with organics and poorly graded gravel fill was observed in boring B-1 and

B-3 to depths of 9.5 feet and 2.5 feet bgs, respectively. The silt was generally brown-gray and varied in consistency/relative density with N-Values of 2 to 3 blows per foot (bpf).

The fine-grained portion of the samples was generally low plasticity with moisture contents varying from 36 to 51 percent. Gravel fill varied from fine to coarse grained and subangular to angular.

MOUNTAIN

SPRINGS

FORMATION:

silty sand (SM), gravel with sand

(GP) with sand and silty SAND (SM) was observed. The materials were generally brown-orange with relative densities varying from very loose to medium dense in the silty sand layer and dense in the gravel layer. The gravel layer moisture content was approximately

19 percent with a general silt fraction of 11 percent. N-values varied from 4 to 11 bpf in the silty sand layer. N-values in the gravel layer were 32 bpf.

2.4 Groundwater

Static groundwater was not encountered during our explorations to the depths explored. However, standing water was observed in the wetland and drainage at the base of the slope near the project site (approximate elevation 10 feet). Given the boring locations are at approximately elevation 70, groundwater is likely present at depths greater than 50 feet bgs at the project site. Please note that groundwater levels can fluctuate during the year depending on climate, irrigation season, extended periods of precipitation, drought, and other factors.

2.5 Infiltration Testing

PBS completed infiltration testing in boring INF-1 at a depth of approximately 3 feet bgs through a 6-inch

PVC standpipe. The standpipe was advanced to the test depth and filled with water to saturate the soil.

Following saturation, the water was allowed to drain while the water level was recorded at regular, timed intervals.

Table 1 presents the test depth, measured infiltration rate, and soil classification.

Table 1. Infiltration and Laboratory Test Results

Exploration Depth of Infiltration Test

(feet bgs)

Infiltration Rate1

(inches/hour) Soil Classification

INF-1 3 0.5

Brown poorly graded

Gravel (GP) with silt and sand 1 Average infiltration rate measured in the field.

The infiltration rate listed in Table 1 are not a permeability/hydraulic conductivity, but a field-measured rate, and does not include correction factors related to long-term infiltration rates. The design engineer should determine the appropriate correction factors to account for the planned level of pre-treatment, maintenance, vegetation, siltation, etc.

Soil types can vary significantly over relatively short distances. The infiltration rates noted above are representative of one discrete location and depth. Installation of infiltration systems within the layer in which the field rate was measured is considered critical to proper performance of the systems.

3 CONCLUSIONS AND RECOMMENDATIONS

3.1 Geotechnical Design Considerations

The project site is underlain by loose to medium dense, potentially saturated silty sand and sand to depths of greater than 50 feet bgs. Conventional foundation support on shallow spread footings is not feasible without some consideration of earthquake risk. Excavation with conventional equipment is feasible at the site.

The grading and final development plans for the project had not been completed when this report was prepared. Once completed, PBS should be engaged to review the project plans and update our recommendations as necessary.

3.2 Seismic Design Considerations

3.2.1 Code-Based Seismic Design Parameters

Due to the potential for liquefaction of site soils below groundwater, the site should be considered Site Class

F. However, in accordance with American Society of Civil Engineers (ASCE) 7-10, Section 20.3.1 for structures having a fundamental period of less than 0.5 seconds, a site-response analysis is not required to determine the spectral accelerations of liquefied soils, and seismic design parameters can be determined using the pre-liquefaction site class.

The average Standard Penetration Test (SPT) N-value (N60) in the upper 100 feet (estimated below depths of

51.5 feet bgs) was estimated to be greater than 15 blows per foot, resulting in classification as Site Class D.

According to the Site Class Map of Pacific County (Palmer et al., 2004), the site lies within the seismic site class

C. However, based on the soil types encountered and the consistency and/or relative density correlated from

SPT N-values of subsurface soils, the site should be characterized as Site Class D.

The seismic design criteria, in accordance with the 2015 IBC, are summarized in Table 2.

Table 2. 2015 IBC Seismic Design Parameters

Parameter Short Period 1 Second

Maximum Credible Earthquake Spectral Acceleration Ss = 1.36 g S1 = 0.70 g

Site Class D*

Site Coefficient Fa = 1.00 Fv = 1.50

Adjusted Spectral Acceleration SMS = 1.36 g SM1 = 1.04 g

Design Spectral Response Acceleration Parameters SDS = 0.91 g SD1 = 0.70 g

Design Spectral Peak Ground Acceleration 0.36 g g= Acceleration due to gravity

* Site Class D can be used if the fundamental period of the new structure is less than 0.5 seconds.

3.2.2 Liquefaction Potential

Liquefaction is defined as a decrease in the shear resistance of loose, saturated, cohesionless soil (e.g., sand) or low plasticity silt soils, due to the buildup of excess pore pressures generated during an earthquake. This results in a temporary transformation of the soil deposit into a viscous fluid. Liquefaction can result in ground settlement, foundation bearing capacity failure, and lateral spreading of ground.

Based on review of the Liquefaction Susceptibility Map of Pacific County, Washington (Palmer et al., 2004), the site is shown as having very low to low liquefaction hazard susceptibility. Our analysis indicates that below depths of approximately 50 feet bgs, the project site is underlain by potentially liquefiable soil. The results of our analyses indicate liquefaction will likely occur at the site during the design seismic event resulting in about

6 inches of liquefaction-induced settlement.

3.2.3 Existing Non-Liquefiable “Crust” and Shallow Spread Footings

The risk of surface manifestation of liquefaction is reduced by the presence of the existing non-liquefiable layer at the surface (i.e., “crust”). This crust is approximately 50 feet thick (represented by the unsaturated soil).

This allows for the use of shallow spread footings to support the proposed buildings. The presence of the crust does not reduce the risk of liquefaction in the deeper soils and several inches of liquefaction settlement would probably still occur at the site. To reduce the impacts of possible differential settlement associated with liquefaction, we recommend all footings be connected with grade beams. Specific recommendations for design and construction of both footings and grade beams are included in the following sections.

3.3 Shallow Foundations

Due to the soft/loose consistency/relative density of the fill encountered within the proposed new building footprint, new footings must not be constructed on the undocumented fill encountered in our borings.

Shallow spread footings bearing on native silty sand and gravel or structural fill bearing on the native soil may be used to support loads associated with the new structures provided the recommendations in this report are followed. Undocumented fill should be removed from within the proposed new building footprints.

3.3.1 Minimum Footing Widths / Design Bearing Pressure

Continuous wall and spread footings should be at least 18 and 24 inches wide, respectively. Footings should be sized using a maximum allowable bearing pressure of 3,000 psf, bearing in undisturbed silty sand and/or gravel with sand. This is a net bearing pressure and the weight of the footing and overlying backfill can be disregarded in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long-term live loads. Allowable bearing pressures may be increased by one-third for seismic and wind loads.

Footings will settle in response to applied loads. Based on our evaluation of the subsurface conditions and our analysis, we estimate post-construction settlement will be less than about 1 inch. Differential settlement will be on the order of one-half of the total settlement.

3.3.2 Footing Embedment Depths

PBS recommends that all footings be founded a minimum of 18 inches below the lowest adjacent grade or the depth of scour, whichever is greater. The footings should be founded below an imaginary line projecting upward at a 1H:1V (horizontal to vertical) slope from the base of any adjacent, parallel utility trenches or deeper excavations.

3.3.3 Footing Preparation

Undocumented fill encountered in the proposed new building areas should be removed and replaced with structural fill. Structural fill should be planned to extend a minimum of 1 foot laterally beyond the edges of footings in all directions for each foot of fill removed/replaced. Structural fill may be composed of crushed rock or other, suitable materials and prepared as specified in section 4.4, Structural Fill, of this report.

Excavations for footings should be carefully prepared to a neat and undisturbed state. A representative from

PBS should confirm suitable bearing conditions and evaluate all exposed footing subgrades. Observations should also confirm that undocumented fill and loose or soft materials have been removed from new footing excavations and concrete slab-on-grade areas. Localized deepening of footing excavations may be required to penetrate loose, wet, or deleterious materials.

PBS recommends a layer of compacted, crushed rock be placed over the footing subgrades to help protect them from disturbance due to foot traffic and the elements. Placement of this rock is the prerogative of the contractor; regardless, the footing subgrade should be in a dense or stiff condition prior to pouring concrete.

Based on our experience, approximately 4 inches of compacted crushed rock will be suitable beneath the footings.

3.3.4 Lateral Resistance

Lateral loads can be resisted by passive earth pressure on the sides of footings and grade beams, and by friction at the base of the footings. A passive earth pressure of 300 pounds per cubic foot (pcf) may be used for footings confined by native soils and new structural fills. The allowable passive pressure has been reduced by a factor of two to account for the large amount of deformation required to mobilize full passive resistance.

Adjacent floor slabs, pavements, or the upper 12-inch depth of adjacent unpaved areas should not be considered when calculating passive resistance. For footings supported on native soils or new structural fills, use a coefficient of friction equal to 0.4 when calculating resistance to sliding. These values do not include a factor of safety (FS).

3.3.5 Grade Beams

Grade beams are not intended to vertically support column footings, but to help hold the facility structure together during a design-level earthquake and reduce the impacts of differential settlement. Grade beams between footings should be designed in accordance with the requirements of section 1810.3.12 of the 2015

IBC.

3.4 Floor Slabs

Satisfactory subgrade support for building floor slabs can be obtained from the native silty sand subgrade prepared in accordance with our recommendations presented in the Site Preparation, Wet/Freezing Weather and Wet Soil Conditions, and Select Granular Fill sections of this report. This will also require removal of undocumented fill from within the building area. A minimum 6-inch-thick layer of imported granular material should be placed and compacted over the prepared subgrade. Thicker aggregate sections may be necessary where undocumented fill is present, soft/loose soils are present at subgrade elevation, and/or during wet conditions. Imported granular material should be composed of crushed rock or crushed gravel that is relatively well graded between coarse and fine, contains no deleterious materials, has a maximum particle size of 1 inch, and has less than 5 percent by dry weight passing the US Standard No. 200 Sieve.

Floor slabs supported on a subgrade and base course prepared in accordance with the preceding recommendations may be designed using a modulus of subgrade reaction (k) of 150 pounds per cubic inch

(pci).

3.5 Pavement Design

Site development may include asphalt concrete (AC) pavement. Recommendations for AC pavements were developed using the American Association of State Highway and Transportation Officials (AASHTO) design methods. The surficial soils across the site are sand with varying amounts of silt. With proper preparation, these soils are suitable to provide pavement support. Soft or loose areas should be compacted to an unyielding condition, or be excavated and replaced with structural fill. Soil may require moisture conditioning to be properly compacted. All pavement subgrades should be evaluated and prepared in accordance with the

Site Preparation and Wet/Freezing Weather and Wet Soil Conditions sections of this report. The required layer of aggregate base rock should be placed and compacted over the prepared subgrade. Aggregate base rock recommendations are provided in section 4.4.3 of this report.

Heavy construction traffic on pavements or partial pavement sections (such as base rock over the prepared subgrade), may exceed the design loads and could potentially damage or shorten the life of the pavements.

Therefore, we recommend the contractor take appropriate measures to protect the subgrades, base rock, and pavement during construction. If construction occurs during wet conditions, thicker aggregate base may be required.

3.5.1 Asphalt Concrete

The AC pavement was evaluated using a pavement design life of 20 years. Access will be limited to maintenance trucks and occasional delivery and/or fire trucks. We have assumed approximately 5 equivalent single-axle loads (ESAL) per week. Based on the limited traffic, we have estimated total ESALs of 50,000 for a

20-year design life. The native subgrade under AC pavement areas should be prepared by scarifying, moisture conditioning, and recompacting a minimum of 12 inches below the bottom of the base course. Our AC pavement design recommendations are based on the following design parameters:

• A resilient modulus of 6,000 pounds per square inch (psi) (equivalent to a California Bearing

Ratio [CBR] value of 4) was used for the sand subgrade that has been scarified and recompacted to a depth of 12 inches bgs

• A resilient modulus of 28,000 psi was assumed for the aggregate base rock

• Initial and terminal serviceability index of 4.2 and 2.5, respectively

• Reliability and standard deviation of 90 percent and 0.45, respectively

• Structural coefficient of 0.42 and 0.13 for the asphalt and aggregate base rock, respectively

Table 3. Minimum AC Pavement Sections

Loading

AC

(inches)

Base Rock

(inches)

Pull-in Car Parking Areas 3 9

Drive Lanes and Access Roads 4 12

The AC binder should be performance graded according to the Washington State Department of

Transportation (WSDOT) SS 9-02.1(4) – Performance Graded Asphalt Binder. The AC should consist of ½-inch, hot mix asphalt (HMA). The maximum lift thicknesses should be 3.0 inches. The AC should conform to WSDOT

SS 5-04.3(7)A – Mix Design, WSDOT SS 9-03.8(2) – HMA Test Requirements, and WSDOT SS 9-03.8(6) – HMA

Proportions of Materials. The AC should be compacted to 91 percent of maximum theoretical density (Rice

Value) of the mix, as determined in accordance with ASTM D2041, following the guidelines set in WSDOT SS

5-04.3(10) – Compaction.

4 CONSTRUCTION RECOMMENDATIONS

4.1 Site Preparation

Construction of the proposed refuge will involve clearing and grubbing of the existing vegetation or demolition of possible existing structures. Demolition should include removal of existing pavement, utilities, etc., throughout the proposed new development. Underground utility lines or other abandoned structural elements should also be removed. The voids resulting from removal of foundations or loose soil in utility lines should be backfilled with compacted structural fill. The base of these excavations should be excavated to firm native subgrade before filling, with sides sloped at a minimum of 1H:1V to allow for uniform compaction.

Materials generated during demolition should be transported off site or stockpiled in areas designated by the owner’s representative.

4.1.1 Proofrolling/Subgrade Verification

Following site preparation and prior to placing aggregate base for the shallow foundations, the exposed subgrade should be evaluated either by proofrolling or another method of subgrade verification. The subgrade should be proofrolled with a fully loaded dump truck or similar heavy, rubber-tire construction equipment to identify unsuitable areas. If evaluation of the subgrades occurs during wet conditions, or if proofrolling the subgrades will result in disturbance, they should be evaluated by PBS using a steel foundation probe. We recommend that PBS be retained to observe the proofrolling and perform the subgrade verifications. Unsuitable areas identified during the field evaluation should be compacted to a firm condition or be excavated and replaced with structural fill.

4.1.2 Wet/Freezing Weather and Wet Soil Conditions

Due to the presence of fine-grained sands in the near-surface materials at the site, construction equipment may have difficulty operating on the near-surface soils when the moisture content of the surface soil is more than a few percentage points above the optimum moisture required for compaction. Soils disturbed during site preparation activities, or unsuitable areas identified during proofrolling or probing, should be removed and replaced with compacted structural fill.

Site earthwork and subgrade preparation should not be completed during freezing conditions, except for mass excavation to the subgrade design elevations.

Protection of the subgrade is the responsibility of the contractor. Construction of granular haul roads to the project site entrance may help reduce further damage to the pavement and disturbance of site soils. The actual thickness of haul roads and staging areas should be based on the contractors’ approach to site development, and the amount and type of construction traffic. The imported granular material should be placed in one lift over the prepared undisturbed subgrade and compacted using a smooth-drum, non-vibratory roller.

During wet conditions, where imported granular material is placed over soft-soil subgrades, we recommend a geotextile be placed between the subgrade and imported granular material. Depending on site conditions, the geotextile should meet the Washington State Department of Transportation Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT SS) 9-33.2 – Geosynthetic Properties for soil separation or stabilization. The geotextile should be installed in conformance with WSDOT SS 2-12.3 – Construction

Geosynthetic (Construction Requirements) and, as applicable, WSDOT SS 2-12.3(2) – Separation or WSDOT SS

2-12.3(3) – Stabilization.

4.2 Excavation

The near-surface soils at the site can be excavated with conventional earthwork equipment. Sloughing and caving should be anticipated. All excavations should be made in accordance with applicable Occupational

Safety and Health Administration (OSHA) and state regulations. The contractor is solely responsible for adherence to the OSHA requirements. Trench cuts should stand relatively vertical to a depth of approximately

4 feet bgs, provided no groundwater seepage is present in the trench walls. Open excavation techniques may be used provided the excavation is configured in accordance with the OSHA requirements, groundwater seepage is not present, and with the understanding that some sloughing may occur. Trenches/excavations should be flattened if sloughing occurs or seepage is present. Use of a trench shield or other approved temporary shoring is recommended if vertical walls are desired for cuts deeper than 4 feet bgs. If dewatering is used, we recommend that the type and design of the dewatering system be the responsibility of the contractor, who is in the best position to choose systems that fit the overall plan of operation.

4.3 Slopes

Our understanding of the current plans is that the project may include permanent slopes or open excavation.

Temporary and permanent cut slopes up to 10 feet high may be inclined at 1.5H:1V and 2H:1V, respectively.

Access roads and pavements should be located at least 5 feet from the top of temporary slopes. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face.

4.4 Structural Fill

The extent of site grading is currently unknown; however, PBS estimates that cuts and fills will be on the order of up to 10 feet to remove the soft and possibly organic soils. Structural fill should be placed over subgrade that has been prepared in conformance with the Site Preparation and Wet/Freezing Weather and Wet Soil

Conditions sections of this report. Structural fill material should consist of relatively well-graded soil, or an approved rock product that is free of organic material and debris, and contains particles not greater than 4 inches nominal dimension.

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 (material 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.

If fill and excavated material will be placed on slopes steeper than 5H:1V, these must be keyed/benched into the existing slopes and installed in horizontal lifts. Vertical steps between benches should be approximately 2 feet.

4.4.1 On-Site Soil

On-site native soils encountered in our explorations are generally suitable for placement as structural fill during moderate, dry weather when moisture content can be maintained by air drying and/or addition of water. In order to reduce moisture content, some aerating and drying of silty sand soils may be required. The material should be placed in lifts with a maximum uncompacted thickness of approximately 8 inches and compacted to at least 95 percent of the maximum dry density, as determined by ASTM D1557 (modified proctor).

4.4.2 Imported Granular Materials

Imported granular material used during periods of wet weather or for haul roads, building pad subgrades, staging areas, etc., should be pit or quarry run rock, crushed rock or crushed gravel, and sand, and should meet the specifications provided in WSDOT SS 9-03.14(2) – Select Borrow. However, the imported granular material should also be fairly well graded between coarse and fine material, and of the fraction passing the US

Standard No. 4 Sieve, less than 5 percent by dry weight should pass the US Standard No. 200 Sieve.

Imported granular material should be placed in lifts with a maximum uncompacted thickness of 9 inches, and be compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D1557.

4.4.3 Crushed Aggregate Base

Imported granular material placed at the base of excavations for spread footings, pavements, and other below-grade structures should be clean, crushed rock or crushed gravel, and sand that is fairly well graded between coarse and fine. The granular materials should contain no deleterious materials, have a maximum particle size of 1 inch, and meet WSDOT SS 9-03.9(3) – Crushed Surfacing Base Course with less than 5 percent by dry weight passing the US No. 200 Sieve. The imported granular material should be placed in one lift and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D1557.

4.4.4 Utility Trench Backfill

Trench backfill placed beneath, adjacent to, and for at least 2 feet above utility lines (i.e., the pipe zone), should consist of well-graded granular material with a maximum particle size of 1 inch and less than 10 percent by dry weight passing the US Standard No. 200 Sieve, and should meet the standards prescribed by

WSDOT SS 9-03.12(3) – Gravel Backfill for Pipe Zone Bedding. The pipe zone backfill should be compacted to at least 90 percent of the maximum dry density as determined by ASTM D1557, or as required by the pipe manufacturer or local building department.

Within pavement areas or beneath building pads, the remainder of the trench backfill should consist of well-graded granular material with a maximum particle size of 1½ inches, less than 10 percent by dry weight passing the US Standard No. 200 Sieve, and should meet standards prescribed by WSDOT SS 9-03.19 – Bank

Run Gravel for Trench Backfill. This material should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM D1557, or as required by the pipe manufacturer or local building department.

The upper 2 feet of the trench backfill should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM D1557.

Outside of structural improvement areas (e.g., roadway alignments or building pads), trench backfill placed above the pipe zone should consist of excavated material free of wood waste, debris, clods, or rocks greater than 6 inches in diameter and meet WSDOT SS 9-03.14 – Borrow and WSDOT SS 9-03.15 – Native Material for

Trench Backfill. This general trench backfill should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D1557, or as required by the pipe manufacturer or local building department.

5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS

In most cases, other services beyond completion of a final geotechnical engineering report are necessary or desirable to complete the project. Occasionally, conditions or circumstances arise that require additional work that was not anticipated when the geotechnical report was written. PBS offers a range of environmental, geological, geotechnical, and construction services to suit the varying needs of our clients.

PBS should be retained to review the plans and specifications for this project before they are finalized. Such a review allows us to verify that our recommendations and concerns have been adequately addressed in the design.

Satisfactory earthwork performance depends on the quality of construction. Sufficient observation of the contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. We recommend that PBS be retained to observe general excavation, stripping, fill placement, footing subgrades, and/or pile installation. Subsurface conditions observed during construction should be compared with those encountered during the subsurface explorations. Recognition of changed conditions requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated.

6 LIMITATIONS

This report has been prepared for the exclusive use of the addressee, and their architects and engineers, for aiding in the design and construction of the proposed development and is not to be relied upon by other parties. It is not to be photographed, photocopied, or similarly reproduced, in total or in part, without express written consent of the client and PBS. It is the addressee's responsibility to provide this report to the appropriate design professionals, building officials, and contractors to ensure correct implementation of the recommendations.

The opinions, comments, and conclusions presented in this report are based upon information derived from our literature review, field explorations, laboratory testing, and engineering analyses. It is possible that soil, rock, or groundwater conditions could vary between or beyond the points explored. If soil, rock, or groundwater conditions are encountered during construction that differ from those described herein, the client is responsible for ensuring that PBS is notified immediately so that we may reevaluate the recommendations of this report.

Unanticipated fill, soil and rock conditions, and seasonal soil moisture and groundwater variations are commonly encountered and cannot be fully determined by merely taking soil samples or completing explorations such as soil borings or test pits. Such variations may result in changes to our recommendations and may require additional funds for expenses to attain a properly constructed project; therefore, we recommend a contingency fund to accommodate such potential extra costs.

The scope of work for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site.

If there is a substantial lapse of time between the submission of this report and the start of work at the site, if conditions have changed due to natural causes or construction operations at or adjacent to the site, or if the basic project scheme is significantly modified from that assumed, this report should be reviewed to determine the applicability of the conclusions and recommendations presented herein. Land use, site conditions (both on and off site), or other factors may change over time and could materially affect our findings; therefore, this report should not be relied upon after three years from its issue, or in the event that the site conditions change.

7 REFERENCES

ASCE. (2010). Minimum Design Loads for Buildings and Other Structures (ASCE 7-10)

IBC. (2015). International Building Code. Country Club Hills, IL: International Code Council, Inc. Washington

State Amendments to the International Building Code 2012 Edition.

Palmer, S. Magsino, S. L, Poelstra J. L, and Niggemann, R. A. (2004). Liquefaction Susceptibility Map of Pacific

County, Washington. Washington Division of Geology and Earth Resources. Open File Report 2004-20.

Liquefaction Susceptibility and Site Class Maps of Washington State, By County. Map 25A— Pacific County

Liquefaction Susceptibility, Sheet 50 of 78. 1: 100,000

Palmer, S. Magsino, S. L, Poelstra J. L, and Niggemann, R. A. (2004). Site Class Map of Pacific County, Washington. Washington Division of Geology and Earth Resources. Open File Report 2004-20.

Liquefaction Susceptibility and Site Class Maps of Washington State, By County. Map 25B—Pacific County

Liquefaction Susceptibility, Sheet 50 of 78. 1: 100,000

PBS Engineering and Environmental. (2017). Geotechnical Engineering Services – Phase 1: Geotechnical Data

Review. Prepared for CTA Architects Engineers. PBS Project No. 73308.000.

Wells, R. E. (1989). Geologic map of the Cape Disappointment-Naselle River area, Pacific and Wahkiakum

Counties, Washington: US Geological Survey, Miscellaneous Investigations Series Map I-1832, scale

1:62,500

FIGURES

0' 1,000' 2,000' 4,000'

PROJECT LOCATION

F l e n a m e

L

P r o j e c t s

W i l l a p a

W i l d l i f e

R e f u g e

G e o

D w g

F I G d w g

L a y o u t

T a b

F

U s e r

J m

B l a n c o

C

A D

P o t

D a t e

T i m e

P

M

SCALE: 1" = 2,000'

SOURCE: USGS CHINOOK, WA OR QUADRANGLE 1984,

PHOTO REVISED 1981.

WASHINGTON

VANCOUVER

OLYMPIA

SEATTLE

SITE

ILWACO

FIGURE

JUNE 2017

73308.000

VICINITY MAP

WILLAPA WILDLIFE REFUGE

LONG BEACH, WASHINGTON

INF-1

B-1

B-2

B-3

0 40' 80' 160'

SCALE: 1" = 80'

F l e n a m e

L

P r o j e c t s

W i l l a p a

W i l d l i f e

R e f u g e

G e o

D w g

F d w

L a y o u t

T a b

F

U s e r

J m

B a n c

C o t

D a t e

T i m e

P

M

SOURCE: © 2017 GOOGLE EARTH PRO

BORING NUMBER AND APPROXIMATE LOCATION

INFILTRATION SAMPLE NUMBER AND APPROXIMATE LOCATION

LEGEND

INF-1

B-1

FIGURE

JUNE 2017

73308.000

SITE PLAN

WILLAPA WILDLIFE REFUGE

LONG BEACH, WASHINGTON

PROPOSED BUILDING

APPENDIX A

Field Explorations

APPENDIX A: FIELD EXPLORATIONS

A1 GENERAL

PBS explored subsurface conditions at the project site by advancing four borings to depths of up to approximately 41.5 feet bgs on May 30 and 31, 2017. The approximate locations of the explorations are shown on Figure 2 Site Plan. The procedures used to advance the borings, collect samples, and other field techniques are described in detail in the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed engineering practices in general accordance with relevant ASTM procedures. “General accordance” means that certain local drilling/excavation and descriptive practices and methodologies have been followed.

A2 BORINGS

A2.1 Drilling

Borings were advanced using a track-mounted CME-850 drill rig provided and operated by Western States

Soil Conservation, Inc., of Hubbard, Oregon. Borings B-1 through B-3 were advanced using mud-rotary drilling techniques. INF-1 was advanced using hollow-stem auger techniques. The borings were observed by a member of the PBS geotechnical staff, who maintained a detailed log of the subsurface conditions and materials encountered during the course of the work.

A2.2 Sampling

Disturbed soil samples were taken in the borings at selected depth intervals. The samples were obtained using a standard 2-inch outside diameter (OD), split-spoon sampler following procedures prescribed for the standard penetration test (SPT). Using the SPT, the sampler is 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 (N-value). The N-value provides a measure of the relative density of granular soils such as sands and gravels, and the consistency of cohesive soils such as clays and plastic silts.

The disturbed soil samples were examined by a member of the PBS geotechnical staff and then sealed in plastic bags for further examination and physical testing in our laboratory.

A relatively undisturbed sample was taken in boring B-1 at a depth of 8 feet bgs. The sample was obtained in a 3-inch OD thin-wall Shelby tube by hydraulically pushing the tube into the undisturbed soil at the bottom of the bore hole. The soils exposed at the ends of the tube were examined and classified. After field classification, the ends of the tube were capped and sealed with tape to preserve the natural moisture of the sample. The sealed tube was returned to our laboratory for physical testing.

A2.3 Boring Logs

The boring logs show the various types of materials that were encountered in the borings 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. The types of samples taken during drilling, along with their sample identification number, are shown to the right of the classification of materials. The N-values and natural water (moisture) contents are shown further to the right.

A3 MATERIAL DESCRIPTION

Initially, samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity, and other distinguishing characteristics of the soil samples were noted. Afterward, the samples were reexamined in the PBS laboratory, various standard classification tests were conducted, and the field classifications were modified where necessary. The terminology used in the soil classifications and other modifiers are defined in Table A-1, Terminology Used to Describe Soil.

SAMPLING DESCRIPTIONS

Table A-2

Key To Test Pit and Boring Log Symbols S P T D ri ve

S am p le r

S ta n d ar d P e n e tr at io n T e st

T M

D

S h e lb y T u b e P u sh

S am p le

T M

D

S p e ci al iz e d D ri ve

S am p le rs

(D e ta ils N o te d o n L o g s)

S p e ci al iz e d D ri ll o r

P u sh am p le r (D e ta ils N o te d n

Lo s)

G ra b S am p le

R o ck

C o ri n g I n te rv al

S cr e

(W at e r o r

A ir S a m p lin

W at e r

Le ve l D u ri ri lli n g /E xc av at io n W at e r

Le ve l A ft ri lli n g /E xc av at io

LOG GRAPHICS

PP Pocket Penetrometer HYD Hydrometer Gradation

TOR Torvane SIEV Sieve Gradation

DCP DS Direct Shear

ATT Atterberg Limits DD Dry Density

PL Plasticity Limit CBR California Bearing Ratio

LL Liquid Limit RES Resilient Modulus

PI Plasticity Index VS Vane Shear

P200 Percent Passing US Standard No. 200 Sieve bgs Below ground surface

OC Organic Content MSL Mean Sea Level

CON Consolidation HCL Hydrochloric Acid

UC Unconfined Compressive Strength

Details of soil and rock classification systems are available on request. Rev. 02/2017

Dynamic Cone Penetrometer

Geotechnical Testing Acronym Explanations

Lithology Boundary:

separates distinct units

(i.e., Fill, Alluvium, Bedrock) at approximate depths inciated

Sampler

Type

Sample

Recovery Sample

Interval

Instrumentation Detail Sampling Symbols Soil and Rock

Well Pipe

Piezometer

Piezometer

Ground Surface

Well Cap

Bottom of Hole

S o il o r R o ck

T y p e s

Well Seal

Well Screen

Soil-type or Material-type

Change Boundary: separates soil and material changes within the same lithographic unit at approximate depth indicated

Table A-1

Terminology Used to Describe Soil

Soil Descriptions

Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based on total dry weight, is the primary soil type and is capitalized in our log descriptions (SAND, GRAVEL, SILT, or CLAY). Smaller percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the

ASTM D2488-06 Visual-Manual Procedure. “General Accordance” means that certain local and common descriptive practices may have been followed. In accordance with ASTM D2488-06, group symbols (such as GP or CH) are applied on the portion of soil passing the 3-inch (75mm) sieve based on visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils.

Fine-Grained Soils (50% or greater fines passing 0.075 mm, No. 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 outlines the terminology used to describe fine-grained soils, and varies from ASTM

D2488 terminology in the use of some common terms.

Primary soil NAME, Symbols, and Adjectives Plasticity

Description

Plasticity

Index (PI)

SILT (ML & MH) CLAY (CL & CH) ORGANIC SOIL (OL & OH)

SILT Organic SILT Non-plastic 0 – 3

SILT Organic SILT Low plasticity 4 – 10

SILT/Elastic SILT Lean CLAY Organic SILT/ Organic CLAY Medium Plasticity 10 – 20

Elastic SILT Lean/Fat CLAY Organic CLAY High Plasticity 20 – 40

Elastic SILT Fat CLAY Organic CLAY Very Plastic >40

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

Description % Composition

With Sand % Sand ≥ % Gravel 15% to 25% plus No. 200

With Gravel % Sand < % Gravel

Sandy % Sand ≥ % Gravel ≤30% to 50% plus No. 200

Gravelly

% Sand < % Gravel

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

Soil Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 7). Descriptive terms are based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows. SILT soils with low to non-plastic behavior (i.e., PI < 7) may be classified using relative density.

Consistency

Term SPT N-value

Unconfined Compressive Strength tsf 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

Table A-1

Terminology Used to Describe Soil

Soil Descriptions

Coarse - Grained Soils (less than 50% fines)

Coarse-grained soil descriptions, i.e., SAND or GRAVEL, are based on the portion of materials passing a 3-inch (75mm) sieve.

Coarse-grained soil group symbols are applied in accordance with ASTM D2488-06 based on 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.

Material NAME Particle Diameter

Inches Millimeters

SAND (SW or SP) 0.003 – 0.19 0.075 – 4.8

GRAVEL (GW or GP) 0.19 – 3 4.8 – 75

Additional Constituents:

Cobble 3 – 12 75 – 300

Boulder 12 – 120 300 – 3050

The primary soil type is capitalized, and the fines content in the soil are described as indicated by the following examples.

Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 percent. Other soil mixtures will have similar descriptive names.

Example: Coarse-Grained Soil Descriptions with Fines

>5% to < 15% fines (Dual Symbols) ≥15% to < 50% fines

Well graded GRAVEL with silt: GW-GM Silty GRAVEL: GM

Poorly graded SAND with clay: SP-SC Silty SAND: SM

Additional descriptive terminology applied to coarse-grained soils follow.

Example: Coarse-Grained Soil Descriptions with Other Coarse-Grained Constituents

Coarse-Grained Soil Containing Secondary Constituents

With sand or with gravel ≥ 15% sand or gravel

With cobbles; with boulders Any amount of cobbles or…