00-31-32-01_1-3-B-11_2014_05_27_IBM13C0014_SD_Admin_Geotech_Report_Stantec.pdf

STATEMENT OF CONFIDENTIALITY

This report has been submitted for the sole and exclusive use of Abide International Inc.and shall not be disclosed or provided to any other entity, corporation, or third party for purposes beyond the specific scope or intent of this report without the express written consent of Stantec Consulting Services Inc.

Prepared by:

Jaret Fischer, P.E.

Senior Engineer

Reviewed by:

Kevin Miskin, P.E.

Principal Engineer

GEOTECHNICAL INVESTIGATION

REPORT

United States International

Boundary and Water Commission Water / Wastewater Treatment Plan

New Administration Building

2225 Dairy Mart Road

San Ysidro, California 92173

Prepared for:

Abide International Inc.

561 First Street West

Sonoma, California 95476

Prepared by:

Stantec Consulting Services Inc.

25864-F Business Center Drive

Redlands, CA 92374

(909) 335-6116 tel

(909) 335-6120 fax

Stantec JN: 184710304

May 27, 2014

Stantec Consulting Services Inc.

25864-F Business Center Drive Redlands, CA 92374 Tel: (909) 335-6116 Fax: (909) 335-6120

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May 27, 2014

Mr. Karl Lindstrom Abide International Inc.

561 First Street West Sonoma, California 95476

RE: GEOTECHNICAL INVESTIGATION REPORT

United States International Boundary and Water Commission Water / Wastewater Treatment Plant New Administration Building 2225 Dairy Mart Road San Ysidro, California 92173

Dear Mr. Lindstrom, Pursuant to the request of Abide International Inc. (Abide), Stantec Consulting Services Inc.

(Stantec) has prepared the attached Geotechnical Investigation Report for the proposed administration building at the United States International Boundary and Water Commission, Water / Wastewater Treatment Plant, located at 2225 Dairy Mart Road, in the City of San Ysidro, San Diego County, California.

This investigation was performed in general accordance with Stantec’s standard protocol for geotechnical investigations. The objective of the geotechnical investigation was to assess the soil conditions underlying the Site and make geotechnical recommendations for design and construction of the proposed development, which includes building a new 4,250 square feet (ft2) administration building.

Based upon the results of this investigation, development of the Site is geotechnically feasible provided that the recommendations presented herein are implemented in the design and construction of the project.

The complete findings of this investigation and recommendations for Site development are presented in the attached report. It is our pleasure to be of service to you and we look forward to providing Abide with future engineering services. Should you have any questions regarding the information contained in the attached report, please contact the undersigned at your convenience.

Respectfully submitted, Stantec Consulting Services Inc.

Jaret Fischer, P.E.

Senior Engineer

Stantec Consulting Services Inc.

25864-F Business Center Drive Redlands, CA 92374 Tel: (909) 335-6116 Fax: (909) 335-6120

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Enclosure: Geotechnical Investigation Report

International Boundary and Water Commission May 27, 2014 San Ysidro, California Page i

Facility: USIBWC – Administration Building Consultant: Stantec Location: 2225 Dairy Mart Road Stantec JN: 184710304

San Ysidro, California

REPORT SUMMARY

Allowable Footing Bearing Pressures - Building Foundations 1,500 psf

- Canopy Foundations 2,500 psf

Passive Lateral Pressures - Building Foundations 350D psf/ft

- Canopy Foundations 350D psf/ft

Coefficient of Friction - Building Foundations 0.30

Modulus of Subgrade Reaction 225 pci

Expansive Soils o Yes x No

Expansion Potential x V. Low o Low o Medium o High o V. High

R-Value 20

Automobile Traffic (TI = 4.5) 4.0" AC / 4.0" AB Truck Traffic (TI = 6.5) 4.0" AC / 6.0" AB

Artificial Fill x Yes o No

Relatively Loose Near-Surface Soils o Yes x No

Groundwater Within 20 Feet of Surface o Yes x No

Monitoring Well Installed o Yes x No

Hydrocarbons Detected o Yes x No

Existing Underground Tanks o Yes x No

Existing Structures o Yes x No

Special Considerations:

To provide uniform and firm support for the building foundations, removal of the existing soils will be required to a minimum depth of 4 feet or 2 feet below the bottom of the proposed footings, whichever is deeper. Compact and maintain moisture at 2 percent over optimum.

San Ysidro, California Page i

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 AUTHORIZATION AND LIMITATIONS

1.2 PURPOSE AND SCOPE OF WORK

1.3 SITE LOCATION

1.4 SITE DESCRIPTION

2.0 PROJECT DESCRIPTION

3.0 SUBSURFACE INVESTIGATION

3.1 PRE-DRILLING PROCEDURES

3.2 HOLLOW STEM AUGER DRILLING

3.3 SPLIT SPOON SOIL SAMPLING

3.4 LABORATORY SOIL TESTING

4.0 REGIONAL GEOLOGIC CONDITIONS

4.1 REGIONAL PHYSIOGRAPHIC CONDITIONS

4.2 REGIONAL GEOLOGY

4.3 REGIONAL HYDROGEOLOGY

5.0 SUBSURFACE SOIL AND GROUNDWATER CONDITIONS

5.1 STANTEC FIELD INVESTIGATION

6.0 REGIONAL SEISMIC CONDITIONS

6.1 REGIONAL SEISMICITY

6.2 CALIFORNIA BUILDING CODE SEISMIC CRITERIA

6.3 REGIONAL SEISMIC HAZARDS

6.3.1 Fault Rupture Hazard

6.3.2 Liquefaction Hazard

6.3.3 Seismic Induced Settlement in Unsaturated Zone

7.0 ENGINEERING RECOMMENDATIONS

7.1 EXPANSIVE SOIL POTENTIAL

7.2 CORROSIVE SOIL POTENTIAL

7.3 FOUNDATION DESIGN

7.3.1 Building Foundations

7.3.2 Covered Parking Canopy Foundations

7.3.3 Foundation Construction

7.3.4 Estimated Foundation Settlement

7.4 SLOPES

7.5 TENTATIVE PAVEMENT DESIGN

7.5.1 Asphalt Concrete Pavement

7.5.2 Portland Cement Concrete Pavement

7.5.3 Subgrade and Aggregate Base Specifications

7.6 CONCRETE FLOOR SLABS-ON-GRADE

7.7 TEMPORARY EXCAVATIONS

7.8 SITE GRADING

7.8.1 Clearing and Grubbing

7.8.2 Removal Requirements

7.8.3 Placement of Compacted Fill

7.9 POST INVESTIGATION SERVICES

8.0 CLOSURE

9.0 REFERENCES

San Ysidro, California Page ii

TABLE OF CONTENTS (Continued)

LIST OF FIGURES

Figure 1............................................................................................................. Site Location Map Figure 2...............................................................................................................................Site Plan

LIST OF APPENDICES

Appendix A ................................................................................................................. Boring Logs Appendix B ...............................................................................................Laboratory Test Results Appendix C ..................................................General Earthwork and Grading Specifications

International Boundary and Water Commission 1 May 27, 2014 San Ysidro, California

1.0 INTRODUCTION

1.1 AUTHORIZATION AND LIMITATIONS

This report presents the results of a geotechnical investigation performed at the request of Abide International Inc. (Abide), by Stantec Consulting Services Inc. (Stantec), for the proposed administration building at the existing United States International Boundary and Water Commission (IBWC), Water / Wastewater Treatment Plant, located at 2225 Dairy Mart Road, in the City of San Ysidro, San Diego County, California. This report has been prepared for Abide and their project design consultants to be used solely in the design of the proposed project, as described herein. This report may not contain sufficient information for other uses or the purposes of other parties.

1.2 PURPOSE AND SCOPE OF WORK

The objective of this investigation was to assess the nature and engineering properties of the encountered subsurface soils and to provide geotechnical design recommendations for Site development, which includes a 4,250 ft2 single story building. The scope of work was performed in general accordance with Stantec’s standard protocol for geotechnical assessments, and included the following tasks:

Review available subsurface information for the Site, Drill, log and sample five soil borings, Perform soil mechanics laboratory testing on select soil samples, Evaluate geotechnical properties of soils pertinent to the design and construction of the proposed development, and Summarize findings, conclusions, and recommendations in a report.

1.3 SITE LOCATION

The Site is located at 2225 Dairy Mart Road, in the City of San Ysidro, County of San Diego, California (Site). The Site is bounded by vacant land followed by the Tijuana River and a small radio controlled airport to the north and east, vacant land followed by a water treatment plant to the west, and vacant land followed by the United States / Mexico border to the south.

1.4 SITE DESCRIPTION

The facility boundary is irregular in shape, is approximately 36 acres in size, and is occupied by an existing water / wastewater treatment plant located at 2225 Dairy Mart Road, in the City of San Ysidro (Figure 2). The Site where the proposed administrative building will be located within the facility is currently vacant land covered with low lying weeds.

International Boundary and Water Commission 2 May 27, 2014

2.0 PROJECT DESCRIPTION

Stantec Architecture Inc. of Sacramento, California provided the preliminary development layout for the proposed project. The proposed development will consist a new single story 4,250 ft2 building. The Site location and the layout of the proposed structures are shown on Figure 2.

There were no building or grading plans or design loads available at the time of this report.

Based on our experience with similar projects and the available information, the conceptual design generally calls for the building to be founded on a combination of shallow continuous footings (width = 1.0 to 1.5 feet) and spread footings (width = 3.0 to 4.0 feet). The foundation loads for the proposed structure were estimated for the purpose of this report at less than 1.5 kips per linear foot (klf) for continuous building wall footing loads and 2.5 kips per square foot (ksf) for spread footings. If actual design loading conditions differ from those indicated above, the recommendations of this report will need to be re-evaluated and are subject to change.

Based upon Stantec’s review of the existing Site topography, it is assumed that the final surface elevations will not vary more than 0.5 to 1.0 foot from existing grades and that minor grade changes will be made for the purpose of establishing Site drainage. Stantec recommends that the final grading plan be provided to the Project Soils Engineer for review. The recommendations of this report are subject to change based upon review of the final grading plan.

International Boundary and Water Commission 3 May 27, 2014

3.0 SUBSURFACE INVESTIGATION

3.1 PRE-DRILLING PROCEDURES

Underground Service Alert (USA) was notified several days prior to commencing drilling activities to identify any public utilities that may conflict with the proposed boring locations. In addition, potential conflict with underground utilities was prevented by conducting a geophysical survey and manually augering the upper five feet of soil at each proposed soil boring location, prior to drilling.

3.2 HOLLOW STEM AUGER DRILLING

Five hollow stem auger (HSA) soil borings were drilled on May 6 and May 7, 2014, by California Pacific Drilling (Cal-Pac) under the direction of a Stantec field engineer or geologist. CalPac drilled the soil borings using a Mobile B-61 HSA drill rig. All drilling and soil sampling were performed under the general guidance of ASTM D 6151 (Standard Practice for Using Hollow- Stem Augers (HSA) for Geotechnical Exploration and Soil Sampling).

The HSA soil borings drilled for this geotechnical investigation were advanced using eight-inch outside diameter auger, to a maximum depth of approximately 46.5 feet below the ground surface (bgs), at the location shown on Figure 2. The rationale for placement of the borings was to locate at least one boring in the vicinity of each of the proposed structure to investigate the underlying subsurface conditions.

At each boring location, drilling was initiated by pushing the lead HSA auger below the ground surface and rotating at a low velocity. Firm downward pressure and low rotation velocity were maintained in the beginning to produce a straight borehole. Once a straight hole was initiated and the HSA auger appeared clear of potential underground utilities, rotation velocity and downward pressure were increased. The rotation velocity and downward pressures were adjusted during drilling to optimize penetration rates with appropriate drill cutting return up the HSA auger flight. Additional five-foot sections of HSA auger flight were attached to the drill column to achieve the desired drilling/sampling depths.

When the desired sampling depth was achieved, the bottom of the borehole was cleaned by slowly rotating the auger with minimal downward pressure. When the borehole was sufficiently clean, soil samples were collected as described in the section below.

Following completion of drilling and soil sampling, the borings were abandoned by removing the auger and/or sampling equipment from the borehole and subsequently backfilling with native soil.

3.3 SPLIT SPOON SOIL SAMPLING

Stantec field personnel were onsite to supervise field operations, log subsurface soil conditions, and to collect soil samples for physical and chemical analysis. Soil samples were collected using a California Modified (CM) and Standard Penetration Test (SPT) split-spoon samplers, under the general guidance of ASTM D 1586 (Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils), 3550 (Standard Practice for Ring-Lined Barrel Sampling of Soils) and 6066 (Standard Practice for Determining the Normalized Penetration Resistance of Sands for Evaluation of Liquefaction Potential). The CM sampler is approximately 18-inches long by 2.5 inches inside diameter (ID). The SPT sampler is approximately 18-inches long by 1.5 inches ID.

The samplers were driven at approximately five-foot intervals with a 140-pound hammer, International Boundary and Water Commission 4 May 27, 2014 free-falling 30 inches. Unless otherwise indicated on the boring logs, the samplers were advanced 18 inches at each sample interval and the blow counts required to advance the sampler each six-inch drive length were recorded on the boring logs. The blow counts are used in the evaluation of the consistency of the soils and are correlated to various engineering properties.

Unless otherwise indicated on field boring logs, soil sampling was performed at approximately five-foot intervals, to the total depth of exploration, to develop a description of the subsurface stratigraphy and to collect samples for potential geotechnical testing. The observed soils in soil samples and drill cuttings were classified in accordance with the Unified Soil Classification System, under the guidance of ASTM D 2488-00 (Standard Practice for Description and Identification of Soils [Visual-Manual Method]).

Geotechnical samples were collected from the CM and SPT samplers. Six relatively undisturbed brass rings were carefully removed from the CM sampler, placed in a plastic sleeve and sealed with plastic end caps. Electrical tape was used to secure the end caps to the plastic sleeve to preserve natural moisture content. Disturbed samples were also collected from the lowermost brass tube of the SPT sampler. The soil was extruded from the brass tube and placed in a sealed plastic bag. Geotechnical ring and bulk samples were labeled and transported to a soil mechanics laboratory for physical testing. The CM soil samples were securely packed with foam or other shipping materials to minimize sample disturbance, under the guidance of ASTM D 4220- 00 (Standard Practice for Preserving and Transporting Soil Samples).

3.4 LABORATORY SOIL TESTING

The following laboratory tests were performed on samples collected at the Site either in general accordance with the American Society for Testing and Materials (ASTM) or contemporary practices of the soil engineering profession:

In-Situ Moisture and Density (ASTM D 2216): In-situ moisture and density are calculated by weighing and measuring the drive samples obtained from the borings to determine their in-place moisture and density. These results are used to analyze the consistency of the subsurface soils.

Direct Shear Test (ASTM D 3080): The tests were performed on an undisturbed sandy soil sample in order to obtain the soil shear strength values, which are among the basic soil parameters that are used to estimate soil bearing capacity, slope stability and lateral earth pressures.

Sieve Analysis (ASTM D-422): This test is used to evaluate the distribution of soil grain sizes, which constitute the soil fabric and is used in soil classification and assessment of soil engineering behavior.

Maximum Dry Density and Optimum Moisture Content (ASTM D 1557): The compaction curve defines the relationship between water content and dry unit weight of soils compacted under modified compaction effort. The maximum dry density and optimum water content are used to determine the relative density of existing soils and to determine the level of compaction during grading activities.

Chemical Tests for Corrosion Potential (Caltrans 643, 422, 417, and 532): The red-ox potential, pH, water extractable sulfates, water extractable chlorides, sulfides, and resistivity were evaluated in a near surface soil sample.

Stantec has reviewed the laboratory test data and report provided by Converse Consultants dated May 21, 2014 and concurs with the laboratory test results and report. Materials laboratory tests completed include one Soil Corrosivity Test (ASTMG 187, ASTM D 4327, ASTM D 6919, and

International Boundary and Water Commission 5 May 27, 2014

Cal Trans 6143) and four Direct Shear Tests (ASTM D3080). The laboratory results of all laboratory tests are presented in Appendix B.

International Boundary and Water Commission 6 May 27, 2014

4.0 REGIONAL GEOLOGIC CONDITIONS

4.1 REGIONAL PHYSIOGRAPHIC CONDITIONS

The Site is located in the southwestern portion of the Peninsular Range Geomorphic Province in the southwestern part of California. The region is separated by northwest trending valleys, subparallel to faults branching from the San Andreas Fault. The Site resides in the portion of the Province drained by the Tijuana River.

The United States / Mexico International Border is located approximately 200 feet south of the Site, the Tijuana River is located adjacent to the north of the Site, Interstate 5 is located approximately 4,800 feet northwest of the Site, and the Pacific Ocean is located approximately

3.5 miles west of the Site. Based on interpretation of the ground surface elevation contour lines drawn on the topographic map, the Site is located at an elevation of approximately 45 feet above mean sea level (msl). The topography in the vicinity of the Site is moderate, with a regional slope to the north toward the Tijuana River (USGS, 1955).

4.2 REGIONAL GEOLOGY

The regional surficial geology is described as late to middle Pleistocene era consisting of mostly poorly sorted, moderately permeable, reddish-brown interfingered strandline, beach, estuarine, and colluvial deposits overlying siltstone, sandstone, and conglomerate (USGS, 2004).

The Site is located in Southern California, a seismically active area. The nearest recently active fault includes the San Ysidro Fault located approximately 1.7 miles northeast of the Site. The Site is not located within an Alquist-Priolo Earthquake Fault Zone (CDMG, 2000).

4.3 REGIONAL HYDROGEOLOGY

According to the California Department of Water Resources (CDWR) Bulletin 118 Report, the Site is located within the Tijuana Groundwater Basin, in the South Coast Hydrologic Region. The basin is approximately 11.6 square miles and is bounded by the international border with Mexico to the south, semi-permeable Pleistocene and Pliocene marine deposits to the east and north, and the Pacific Ocean to the west (DWR, 2006).

Groundwater data from previous soil borings in the proposed building location indicates the depth to first groundwater is approximately 16 feet bgs (WCC, 1993). Groundwater in the site vicinity flows to the north toward the Tijuana River. Groundwater was encountered at a depth of approximately 20 to 23 feet below the ground surface during this investigation.

International Boundary and Water Commission 7 May 27, 2014

5.0 SUBSURFACE SOIL AND GROUNDWATER CONDITIONS

5.1 STANTEC FIELD INVESTIGATION

The native subsurface soils encountered below the site were composed of interbedded layers of sand (SP, SW, SP-SM, SM and SC USCS soil type) with variable amounts of silt and clay, gravel (GM USCS soil type) with variable amounts of sand and silt, and clay (CL USCS soil type) with variable amounts of sand from the ground surface to the maximum depth of exploration at 46.5 feet below the ground surface (bgs). The near surface soils in the upper 2 to 4 feet appear to be fill placed during mass grading when the Site was initially developed around 1995. The fill soils consist of silty gravel with sand and silty sand with gravel, and were generally moist and dense in density. The sands below the fill soils were fine to coarse-grained and generally, moist to wet and medium dense to very dense in density. The low plasticity silts were generally moist and very stiff in consistency.

The subsurface soils were not difficult to penetrate nor did the borings cave to the maximum depth of exploration. Groundwater was encountered at a depth of approximately 20 to 23 feet bgs during this investigation.

A more detailed description of the interpreted soil profile in each borehole is presented on boring logs in Appendix A. The groupings represent the predominant materials encountered in soil samples. Also, stratification lines indicate the approximate boundary between the major material types. The actual transition may be gradual.

International Boundary and Water Commission 8 May 27, 2014

6.0 REGIONAL SEISMIC CONDITIONS

6.1 REGIONAL SEISMICITY

The Site, as is most of California, is located in a seismically active area. The estimated distance of the Site to the nearest expected surface expression of nearby faults is presented in the table below.

Fault Distance (miles) (1)

Maximum Moment Magnitude (1)

San Ysidro 1.7 6.6

Rose Canyon 12.1 6.5

Coronado Bank 12.3 7.4 Newport – Inglewood (offshore) 47.3 6.5

Elsinore - Julian 47.8 7.1 Elsinore – Coyote Mountain 50.1 6.8

Earthquake Valley 51.1 6.5

1. Measured from 2008 National Seismic Hazard Maps - USGS (USGS, 2008).

6.2 CALIFORNIA BUILDING CODE SEISMIC CRITERIA

Based on the specified design criteria of the 2013 California Building Code, the following Site seismic information may be considered for earthquake design.

Design Criteria Design Value

Site Class D

Mapped Spectral Response Acceleration for Short Periods Ss (g)

1.141

Mapped Spectral Response Acceleration for 1-second Period S1 (g)

0.438

Maximum Considered Earthquake Spectral Acceleration for Short Periods SMS (g)

1.190

Maximum Considered Earthquake Spectral Response Acceleration for 1-second Periods SM1 (g)

0.685

5-percent Design Spectral Response Acceleration for Short Periods SDS (g)

0.794

5-percent Design Spectral Response Acceleration for 1-second Periods SD1 (g)

0.457

Site Coefficient Fa 1.043

Site Coefficient Fv 1.562

6.3 REGIONAL SEISMIC HAZARDS

6.3.1 Fault Rupture Hazard

The Site is not located within a currently mapped California Earthquake Special Studies Fault Zone. As described above, the nearest faults are the San Ysidro Fault and Rose Canyon Fault, located approximately 1.7 miles northeast and 6.5 miles west of the Site, respectively. Based on available geologic data, there is low potential for surface fault rupture from the San Ysidro Fault

International Boundary and Water Commission 9 May 27, 2014 and Rose Canyon Fault and other known nearby active faults propagating to the surface of the Site during the design life of the proposed development.

6.3.2 Liquefaction Hazard

Liquefaction Background

Liquefaction of saturated sandy soils is generally caused by the sudden decrease in soil shear strength due to vibration. During cyclic shaking, typically caused by an earthquake, the soil mass is distorted, and interparticulate stresses are transferred from the soil particles to the pore water. As pore pressure increases the bearing capacity decreases and the soil may behave temporarily as a viscous fluid (liquefaction) and, consequently, loses its capacity to support the structures founded thereon.

Engineering research of soil liquefaction potential (Seed, et. al., 1982 and 1985) indicates that generally three basic factors must exist concurrently in order for liquefaction to occur, namely:

A source of ground shaking, such as an earthquake, capable of generating soil mass distortions.

A relatively loose sandy soil fabric exhibiting a potential for volume reduction.

A relative shallow groundwater table (within approximately 50 feet below ground surface) or completely saturated soil conditions that will allow positive pore pressure generation.

Screening Investigation for Liquefaction Potential

The Site is not located within a current, mapped California Liquefaction Hazard Zone. However, a site specific liquefaction evaluation was conducted in accordance with the guidance outlined in Special Publication 117A: Guidelines for Evaluating and Mitigating Seismic Hazards in California (CDMG, 2008). The in-situ characteristics of the subsurface soils were analyzed, and similarities and dissimilarities of the subsurface conditions were compared with those sites where the subsurface soils are known to have liquefied.

Following the specified steps of the Screening Investigation (CDMG, 2008), a historic high groundwater elevation was evaluated for the liquefaction analysis. Based on available groundwater information in the Site vicinity, groundwater in the site vicinity is expected to be approximately 15 feet below the ground surface (bgs) (WC, 1995). As a result of the depth to groundwater and density of the subsurface soils, the onsite soils do not appear to be susceptible to soil liquefaction. As such, onsite subsurface soils were eliminated from further engineering evaluation of potential liquefaction hazard (CDMG, 2008).

6.3.3 Seismic Induced Settlement in Unsaturated Zone

Near surface soils in the unsaturated zone (upper 5 feet) consist of medium dense to dense soils.

These sediments may be prone to significant volumetric strain as a result of cyclic loading from seismic activity. Although difficult to predict, seismic settlements in the unsaturated zone were estimated to be less than 0.1 inches, following methods promulgated by Tokimatsu and Seed (1987).

Recommendations for mitigating settlements due to loose soils and liquefaction settlement are not required.

International Boundary and Water Commission 10 May 27, 2014

7.0 ENGINEERING RECOMMENDATIONS

Based upon the results of the investigation, development of the Site is geotechnically feasible provided that the recommendations presented herein are implemented in the design and construction of the project. Removal and recompaction of the near surface soils will be required in the structural areas to provide a relatively uniform and firm engineered soil blanket for support of the proposed development and reduce the potential for differential settlement.

7.1 EXPANSIVE SOIL POTENTIAL

The near-surface soils (upper 5 feet) encountered in the proposed building area consist of silty sand and silty gravel with variable amounts of sand. Based on visual classification of subsurface soils in the proposed building area, near surface soils exhibit low to medium expansion potential, as defined by the 2010 California Building Code (CBC, 2010). Design for expansive soils is not required.

If imported soils are used for earthwork at the Site, Stantec recommends that the proposed soils be tested for expansion potential prior to import. To avoid the use of expansive soils on the project, all imported soils must be pre-approved by the Project Soils Engineer prior to utilization.

7.2 CORROSIVE SOIL POTENTIAL

Chemical tests to evaluate corrosive soil potential of near surface soils were performed by Converse Consultants. The test results indicated pH of 7.3, water soluble sulfate = 509 ppm, soluble chlorides = 1,707 ppm, and saturated resistivity = 356 ohm-cm.

Based on the test results, the near surface soils are expected to exhibit a low corrosion potential for concrete and very severe corrosion potential for steel. As a result, corrosion resistant piping is recommended for the Site. Stantec recommends that corrosion resistant piping (e.g. non-metallic pipe), be utilized for all subsurface utilities in contact with onsite soils. Cathodic protection may be utilized in lieu of the corrosion resistant piping if properly designed and approved by an engineer competent in corrosion design.

Material Type Degree of Corrosivity Recommendation

Concrete Low --

Steel Very Severe Corrosion Resistant

Piping

If imported soil is utilized for earthwork at the site, Stantec recommends that the proposed soils be tested for corrosion soil potential prior to import. To avoid the use of corrosive soils on the project, all imported soils should be pre-approved by the Project Soils Engineer prior to utilization.

Proposed import soils exhibiting corrosion potential for steel or concrete should not be utilized at the Site unless appropriate mitigation measures are implemented.

7.3 FOUNDATION DESIGN

7.3.1 Building Foundations

The typical shallow, continuous footings for the buildings, as described in Section 2.0, are expected to provide adequate support for the proposed structure provided they are founded on properly recompacted soil. For continuous perimeter wall footings planned for the building, crystal.cadillo Highlight crystal.cadillo Highlight

International Boundary and Water Commission 11 May 27, 2014 bearing entirely on compacted fill soils, an allowable bearing pressure of 1,500 pounds per square foot (psf) may be incorporated in the design. The building footings should be at least 12 inches in width and founded a minimum of 18 inches deep. The embedment depth should be measured from the bottom of the footing to the lowest adjacent soil subgrade. For resistance to transient lateral loads, such as earthquake and wind loads, the allowable bearing capacity may be increased by one-third.

For spread footings up to 4 feet in width and embedded 18 inches or deeper, an allowable bearing pressure of 1,500 psf may be used in the design provided the footing is constructed on properly compacted fill.

For resistance to transient lateral loads, such as earthquake and wind loads, the aforementioned allowable bearing capacity may be increased by one-third. A modulus of subgrade reaction

(k) of 225 pounds per cubic inch (pci) may be used in the design.

Building footings structural design for resistance of lateral forces may be based upon a passive lateral earth pressure/resistance (equivalent fluid pressure) of 350D psf/ft and a coefficient of friction between the concrete footing and subsurface soils equal to 0.30, where D corresponds to the embedment depth of the footing in feet. For lateral bearing capacity analysis and design, the passive earth pressure and frictional resistance may be combined without reduction.

7.3.2 Covered Parking Canopy Foundations

Canopy column footings consisting of reinforced concrete drilled piers should a minimum diameter or width of 2 feet and embedded at a minimum depth of 4 feet bgs. Based on these assumptions and the anticipated subsurface conditions, an allowable bearing pressure of 2,500 psf may be used in the design. For resistance to transient lateral loads, such as earthquake and wind loads, the aforementioned allowable bearing capacity may be increased by one-third.

Canopy foundation structural design for resistance of lateral forces may be based upon a passive lateral earth pressure/resistance (equivalent fluid pressure) of 350D psf/ft, where D corresponds to the embedment depth of the footing in feet.

7.3.3 Foundation Construction

Proper footing construction will be dependant upon the quality of the contractor’s workmanship. Any deviation from the methods proposed herein should be approved by the Project Soils Engineer prior to implementation.

It is essential that the Project Soils Engineer review and approve the foundation plans and observe the building foundation excavations prior concrete placement, to verify that the contractor utilizes proper construction methods, and that foundation excavations are adequately sized and founded on suitable material. The bottom of the foundation excavations should be excavated in such a way as to minimize slough, debris and unsuitable material from collecting at the bottom of the excavation. The contractor should provide the Project Soils Engineer a safe method to verify that a competent footing bottom has been achieved by the contractor.

7.3.4 Estimated Foundation Settlement

Assuming that the engineering recommendations of this report will be strictly adhered to, static foundation settlement for the above described foundations is estimated to be less than 1.0

International Boundary and Water Commission 12 May 27, 2014 inches total and less than 0.5 inches of differential over a lateral distance of 50 feet, between similarly loaded footings of the same size.

7.4 SLOPES

Although pertinent grading information is currently unavailable, no permanent slopes are anticipated for the project. The stability of slopes, if any, should be evaluated when design-grading information becomes available.

7.5 TENTATIVE PAVEMENT DESIGN

Tentative pavement structural sections were developed based on the visual onsite soil classifications (course-grained sandy soil), an estimated subgrade resistance R-Value of 20, an equivalent single axle load (ESAL) value comparable to the referenced traffic index (TI) values below, and an AASHTO Reliability Factor of 75%. The design below applies to pavement sections supported on compacted existing onsite soils.

7.5.1 Asphalt Concrete Pavement

Traffic Type Automobile Traffic

TI = 4.5

Light Truck Traffic

TI = 6.5

Asphalt Concrete (AC) Thickness 4.0" 4.0"

Aggregate Base (AB) Thickness 4.0" 6.0"

*AASHTO Highway Design Method

7.5.2 Portland Cement Concrete Pavement

Proposed portland cement concrete pavement areas that are subject to vehicle traffic loads, should have a minimum thickness of four inches. However, the structural engineer may require additional thickness for structural purposes. In addition, a minimum of six inches of aggregate base should be placed beneath all concrete pavement areas subject to traffic loads.

The concrete should exhibit a minimum compressive strength of 2,500 psi and approximate three-inch slump (± one inch). Minimum reinforcement for concrete pavement in vehicle traffic areas should include a synthetic fibermesh. Additional reinforcement and/or slab thickness may be appropriate as structural conditions dictate, as determined by the project structural or civil engineer. Other design and construction criteria for concrete floor slabs, such as mix design, strength, durability, reinforcement, joint spacing, etc., should conform to current specifications promulgated by the American Concrete Institute (ACI).

7.5.3 Subgrade and Aggregate Base Specifications

The above pavement sections are based upon the assumption that the subgrade is uniformly compacted to at least 90 percent relative compaction with uniform moisture content within 2 percent of optimum moisture content, as determined by ASTM Standard D 1557, to a depth of 12 inches at the time of base placement. The moisture content of the soil must be maintained and not allowed to dry through slab or footing construction. Final geotechnical observation and testing of subgrade should be performed just prior to the placement of aggregate base or concrete.

The aggregate base for asphalt concrete pavement sections should meet Caltrans specifications for Class 2 base or the specifications for Processed Miscellaneous Base (PMB), as

International Boundary and Water Commission 13 May 27, 2014 contained in the Standard Specifications for Public Works Construction. Aggregate base should be compacted to at least 95 percent relative compaction with uniform moisture content near the optimum percent, as determined by ASTM Standard D 1557. Final geotechnical observation and testing of aggregate base should be performed just prior to the placement of asphalt concrete.

It is possible that Site grading, use of import fill soils, utility line backfilling, and/or underground storage tank installation could alter the distribution of near-surface materials, thus requiring re-evaluation of the recommended pavement structural sections. If any of the above named conditions occurs, which warrants a re-evaluation of the pavement sections, Stantec recommends that at least one near surface soil sample be tested to evaluate the subgrade R-value, following rough grading of the pavement areas. If necessary, the above described tentative pavement structural section recommendations should be revised based on the actual R-value test result.

7.6 CONCRETE FLOOR SLABS-ON-GRADE

At the time of concrete placement, the floor slab subgrade should be firm, relatively unyielding, and be within 2 percent of the optimum moisture content, to a depth of six inches. To protect against capillary moisture and to provide a vapor barrier from the underlying soils, the building floor slab should be underlain by a minimum ten-mil plastic membrane, underlain and covered with a minimum of two inches of sand. The moisture mitigation measures recommended above are applicable to the building floor slab areas that are to be covered by carpet, tile or other moisture sensitive floor coverings. A vapor barrier is not required if moisture sensitive floor coverings are not utilized.

In lieu of a plastic membrane and sand, a four-inch thick layer of open-graded gravel may be used. A suggested gradation for the gravel layer is as follows:

Sieve Size Percent Passing

¾ 90 – 100

No. 40 0 – 10

No. 100 0 – 3

For geotechnical purposes, the minimum concrete floor thickness should be 4 inches and minimum reinforcement should be No. 4 deformed reinforcing bars, spaced at 18 inches on center each way. Additional reinforcing and/or slab thickness should be provided as structural conditions dictate. It is essential that during construction the slab reinforcing bars be properly supported on rebar supports to keep the reinforcing bars centralized (mid-height) in the slab during the concrete pour.

Other design and construction criteria for concrete floor slabs, such as mix design, strength, durability, reinforcement, joint spacing, etc., should conform to the current specifications promulgated by the American Concrete Institute (ACI).

7.7 TEMPORARY EXCAVATIONS

Temporary excavations should be shored or excavated with a slope not steeper than 1:1 (horizontal to vertical) in accordance with OSHA requirements. The OSHA requirements for excavation should be strictly adhered to ensure safety of personnel and equipment around the excavations. The excavations should be inspected by the Project Civil Engineer to verify safe working conditions on a regular basis (at least daily). Surcharges from soil stockpiles, structures, vehicles, etc., should not be positioned within ten feet of the excavation.

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Where cantilevered shoring is used in lieu of sloping the temporary excavation sidewalls, the shoring design may be tentatively based upon the following lateral earth pressures (equivalent fluid pressures with a triangular pressure distribution), up to an excavation depth of 16 feet bgs.

Active: 40H psf/ft, At-rest: 60H psf/ft, Passive: 350D psf/ft, where H is the length of the sheet pile below the ground surface and D is the embedment depth of the shoring measured from the bottom of the excavation (unless pavement or hardscape are present, exclude the upper foot when calculating passive resistance to account for erosion).

These equivalent fluid pressures should be applied as a triangular pressure distribution behind the shoring and assume level backfill behind and in front of shoring. For braced shoring, a uniform rectangular pressure distribution should be used from top to bottom of the shoring equivalent to the following, Bracing: 30H psf/ft where H is the depth of the excavation.

The earth pressures are based on drained conditions (no hydrostatic or buoyant conditions) and the assumption that the shoring is vertical (no batter), and the ground surface in front and behind the shoring is level. For different geometries or conditions, the above lateral earth pressures should be reevaluated. The earth pressures indicated above do not include a safety factor, therefore the shoring design should include an appropriate safety factor for the overall performance of the system.

7.8 SITE GRADING

Site grading will be required to achieve plan grades and to provide uniform support for foundations, slabs-on-grade and pavement. Recommendations for Site grading are presented in the following subsections, while general guide specifications for earthwork and grading are presented in Appendix C. The following grading recommendations are subject to change, depending on the actual earthwork required for the project and the subsurface conditions encountered during grading.

7.8.1 Clearing and Grubbing

The ground surface of the Site should be cleared and grubbed all of vegetation and deleterious materials, prior to grading. Clearing and grubbing is considered complete when soil supporting structural fill material or soil to be excavated as reused as structural fill materials contains less than five percent organic materials (by volume). Excavations created by removing underground structures, construction debris, vegetation roots, contaminated soils, and any other unsuitable materials should be backfilled with clean fill soil and should be compacted in accordance with the requirements presented below.

7.8.2 Removal Requirements

Building Pad:

To reduce differential settlement, and to provide uniform and firm support for the proposed building, removal of existing near surface soils will be required to a minimum depth of 2 feet

International Boundary and Water Commission 15 May 27, 2014 below the proposed bottom of footing elevation, or to a depth of 4 feet bgs, whichever is greater. Depending on weather conditions, the natural moisture content of the soils may exceed the optimum moisture content and will required drying or other stabilization prior to replacement as fill. Once the soils are dried back to 2 percent over the optimum moisture content, if required, they may be placed back in the subexcavation as compacted fill, in accordance with the recommendations of Section 7.8.3. Removal and recompaction should be completed laterally at least five feet beyond the outside edge of the building footings.

Moisture content should be maintained through construction of foundations and slabs.

The continuous footing along any subexcavation that does not extend at least five feet beyond the outside edge of the footing should be designed as a grade beam or with sufficient rebar to reduce the potential for differential settlement.

Pavement Areas:

To provide uniform and firm support for the proposed pavement areas, ripping and recompacting the existing soils will be required to a minimum depth of 1 foot below the bottom of pavement section elevation. If necessary, the soils may be removed and placed back in the subexcavation as compacted fill, in accordance with the recommendations of Section 7.8.3.

Removal and recompaction for pavement areas should extend horizontally at least 2 feet beyond the rear curb face or as property line constraints dictate.

If pavement area recompaction results in substandard relative compaction as a result of unsuitable subsurface conditions, unsuitable areas should be removed to a minimum depth of one foot. Depending on the condition of the subexcavation bottom, additional removal depth may be required. Once a suitable subexcavation bottom is achieved, the exposed surface at the bottom of the subexcavation should be moisture conditioned and surface compacted to the specified density. The removed soils should be placed back in the subexcavation as compacted fill, in accordance with the recommendations of Section 7.8.3.

Required Inspection of Subexcavation:

It is imperative that the Project Soils Engineer inspect the bottoms of all subexcavations. As a general rule, a suitable subexcavation bottom should have a minimum dry density of 85 percent of the maximum dry density. Final determination of a suitable subexcavation bottom is at the discretion of the Project Soils Engineer. Should any deeper artificial fill or relatively loose soils, not in conformance with the above described conditions, be encountered within the exposed bottom of the subexcavations, the depth of removal may be extended in accordance with the professional judgment of the Project Soils Engineer.

7.8.3 Placement of Compacted Fill

General guide specifications for placement of fill and backfill are provided in Appendix C. The bottom of subexcavations and areas to receive fill should be scarified to a depth of six inches, moisture conditioned to +/- 2 percent of the optimum moisture content and then surface compacted to the relative compaction specified below.

Compaction should be performed in thin lifts using mechanical compaction equipment and maintained until after pavement, slabs, or foundations are constructed. Unless specified otherwise, all fill should be compacted to a minimum of 90 percent relative compaction based upon the maximum density obtained in accordance with ASTM Standard D 1557. Gravel should not be used to backfill any excavations onsite without the approval of the Project Soils Engineer.

If the Project Soils Engineer approves the use of gravel in excavations, vibratory compaction and “burrito wrapping” in a geosynthetic filter fabric may be required.

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During grading, frequent density testing should be performed by a representative of the geotechnical engineer to evaluate compliance with grading specifications. Where testing indicates insufficient relative compaction, additional compactive effort should be applied, with the adjustment of moisture content where necessary, until the required relative compaction is obtained.

7.9 POST INVESTIGATION SERVICES

Post investigation services are an important and necessary continuation of this investigation, and it is recommended that Stantec be retained as the Project Soils Engineer to perform such services to assure adherence with the intent of the geotechnical recommendations presented herein.

Final project grading and foundation plans, foundation details and specifications should be reviewed by Stantec, prior to construction, to confirm that the full intent of the recommendations presented herein have been applied to the designs. Following review of plans and specifications, sufficient and timely observation during construction should be performed to correlate the findings of this investigation with the actual subsurface conditions exposed during construction.

The following should be inspected observed, and tested by the Project Soils Engineer to ensure compliance with the recommendations contained herein.

Rough Site grading, including the bottom of subexcavations.

Footing excavations to confirm that the foundation elements are founded in the recommended materials.

Utility trench backfill.

Subgrade preparation, base placement and compaction.

All other items of work requiring an opinion of adequacy from the Project Soils Engineer to be included in a final geotechnical report.

During construction, the Project Soils Engineer and/or their authorized representatives, are present at the Site to provide a source of advice to the client regarding the geotechnical aspects of the project and to observe and test the earthwork. Their presence should not be construed as an acceptance of responsibility for site safety or for the performance of the completed work since it is the sole responsibility of the contractor performing the work to ensure that the work complies with federal, state, and local safety procedures/regulations and with all applicable plans, specifications, ordinances, etc.

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8.0 CLOSURE

Our conclusions, recommendations and discussions presented herein are (1) based upon an evaluation and interpretation of the findings of the field and laboratory programs, (2) based upon an interpolation of subsurface conditions between and beyond the explorations, (3) subject to confirmation of the actual conditions encountered during construction, and (4) based upon the assumption that sufficient observation and testing will be provided by Stantec during construction.

Any person using this report for bidding or construction purposes should perform such independent investigations as he deems necessary to satisfy himself as to the surface and subsurface conditions to be encountered and the procedures to be used in the performance of work on this project.

This report contains information which is valid as of this date. However, conditions that are beyond our control or that may occur with the passage of time may invalidate, either partially or wholly, the conclusions and recommendations presented herein.

The conclusions of this report are based on an interpolation of subsurface conditions encountered at the boring locations. The actual subsurface conditions at unexplored locations may be different. Consequently, the findings and recommendations of this report will require re-evaluation if subsurface conditions different than stated herein are encountered.

Inherent in most projects performed in the heterogeneous subsurface environment, continuing subsurface investigations and analyses may reveal findings that are different than those presented herein.