B09_Amend_1_Attach_1_YOSE_196416_Specs_Div_1_Geotech_and_Hazmat_El_Portal_WWTP_Unsecured_0001.pdf

YOSEMITE NATIONAL PARK

CALIFORNIA

Rehabilitate El Portal Wastewater Treatment Facility

YOSE

196416

Volume 1B of 6 Division 01 Reports

PROJECT SPECIFICATIONS

NATIONAL PARK SERVICE (NPS)

DENVER SERVICE CENTER (DSC)

YOSE 196416 TABLE OF CONTENTS

PW\DEN003\D3167637 00 01 10 - 1

TABLE OF CONTENTS

Person Section Responsible Title Pages

VOLUME 1A

SPECIFICATIONS

DIVISION 01—GENERAL REQUIREMENTS

01 11 00 CH Summary of Work ....................................................................... 1- 13 Supplement:

Construction Constraints ............................................................. 1- 3 01 26 01 CH Contract Modification Procedures .............................................. 1- 7 01 27 00 CH Definition of Contract Line Items ............................................... 1- 6 01 31 00 CH Project Management and Coordination ...................................... 1- 12 01 32 16 CH Construction Schedule ................................................................ 1- 11 01 32 33 CH Photo Documentation.................................................................. 1- 3 01 33 23 CH Submittal Procedures .................................................................. 1- 10 01 35 13.22 CH Archeological Protection ............................................................ 1- 4 01 35 23 CH Safety Requirements ................................................................... 1- 5 01 35 91 CH Historic Preservation Treatment Procedures .............................. 1- 4 01 40 00 CH Quality Requirements ................................................................. 1- 11 Supplement:

CH Statement of Structural Tests and Special Inspections ............... 1- 17 01 42 00 CH Reference Standards.................................................................... 1- 14 01 45 36 CH Equipment Seismic Certification ................................................ 1- 4 Supplement:

CH Seismic Qualification of Mechanical and Electrical Equipment Certificate of Compliance ........................................................ 1- 2 01 50 00 CH Temporary Facilities and Controls .............................................. 1- 12 01 57 19 CH Temporary Environmental Controls ........................................... 1- 35 01 57 19.11 CH Indoor Air Quality Management ................................................. 1- 7 01 57 19.12 CH Noise and Acoustics Management .............................................. 1- 3 01 57 23 CH Temporary Storm Water Pollution Prevention ........................... 1- 8 01 57 28 CH Temporary Flow Control ............................................................ 1- 8 01 64 00 CH Government-Furnished Products ................................................ 1- 5 Supplements:

CH Section 40 90 00, Supplement Loop Specifications ................... 1- 63 CH Section 40 92 07, Network Components .................................... 1- 3 CH Section 40 92 07, Supplement Network Equipment List ............ 1- 1 CH Section 40 96 00, Applications Software ................................... 1- 29 01 67 00 CH Product Requirements ................................................................. 1- 11 Supplement:

CH Affirmative Procurement Reporting Form .................................. 1- 2 CH Manufacturer’s Certificate of Compliance ................................. 1- 1

Person Section Responsible Title Pages

TABLE OF CONTENTS YOSE 196416

00 01 10 - 2 PW\DEN003\D3167637

01 73 29 CH Cutting and Patching ................................................................... 1- 4 01 73 40 CH Execution .................................................................................... 1- 8 Supplement:

CH Temporary Water Service Application and Policy ..................... 1- 1 01 74 19 CH Construction Waste Management and Disposal ......................... 1- 8 Supplement:

CH Project Waste Management Plan Worksheet Sample ................. 1- 2 01 77 00 CH Closeout Procedures.................................................................... 1- 6 Supplement:

CH Closeout and Operation & Maintenance (O&M) Requirements Template & Sample ................................................................ 1- 9 01 78 23 CH Operation and Maintenance Data ................................................ 1- 7 Supplement:

CH Equipment Data Sheet................................................................. 1- 1 01 79 00 CH Demonstration and Training ....................................................... 1- 5 Supplement:

CH Manufacturer’s Certificate of Proper Installation ....................... 1- 1 01 81 13 CH Sustainable Design Requirements for Non-LEED™ Projects .... 1- 4 01 81 33 CH Cyber Security Requirements ..................................................... 1- 6 01 88 15 CH Anchorage and Bracing ............................................................... 1- 7 01 91 14 CH Total Building Commissioning ................................................... 1- 12 01 91 15 CH Equipment Testing and Facility Startup ..................................... 1- 25 Supplements:

CH Facility Startup Flowchart ........................................................... 1- 1 CH Unit Process Startup Form .......................................................... 1- 1 CH Facility Performance Demonstration Form ................................ 1- 1 CH El Portal Wastewater Treatment Plant Startup Constraints and Phasing .............................................................................. 1- 13

VOLUME 1B

Title Pages

REPORTS

Geotechnical Report NPS El Portal Wastewater Treatment Plant ............. 1-156 Pavement Design Report YOSE 196416 – Rehabilitate El Portal Administrative Camp Design Services ................................................... 1- 47 Addendum 1, Pavement Design Report, Yose 196416 – Rehabilitate El Portal Administrative Camp Design Services .................................... 1- 30 Hazardous Materials Investigation Report El Portal Wastewater Treatment Plant ....................................................................................... 1-147

Title Pages

YOSE 196416 TABLE OF CONTENTS

PW\DEN003\D3167637 00 01 10 - 3

Asbestos Survey El Portal Admin Camp Laundry House Building #1 ..... 1- 9 Limited Lead Samples by XRF El Portal Admin Camp Laundry House Building #1 .................................................................................. 1- 12 Asbestos Survey El Portal Admin Camp Old House Building #6 ............. 1- 11 Asbestos and Lead Survey El Portal Admin Camp Debris Field .............. 1- 13 Executive Summary Asbestos and Lead Testing El Portal Admin Camp ........................................................................................... 1- 9

END OF SECTION

REPORTS

SUBMITTED TO:

Jacobs Engineering Group, Inc.

9191 Jamaica Street Englewood, CO 80112

BY:

Shannon & Wilson 1321 Bannock Street, Suite Denver, Colorado 80204

(303) 825-3800 www.shannonwilson.com

GEOTECHNICAL REPORT

NPS El Portal Wastewater Treatment Plant

EL PORTAL, CALIFORNIA

February 2022

Shannon & Wilson No: 106739-001

NPS El Portal Wastewater Treatment Plant Geotechnical Report

106739-001 February 2022

PAGE INTENTIONALLY LEFT BLANK FOR DOUBLE-SIDED PRINTING

2/18/2022-106739-001_R1 Geotechnical Report_Rev1docx.docx i

Submitted To: Jacobs Engineering Group, Inc.

9191 Jamaica Street Englewood, CO 80112 Attn: Travis McIntosh, P.E., S.E.

Subject: GEOTECHNICAL REPORT, NPS EL PORTAL WASTEWATER TREATMENT

PLANT, EL PORTAL, CALIFORNIA

We are pleased to submit our geotechnical report for the above-referenced project. The enclosed report summarizes subsurface conditions encountered in our exploration program, laboratory test results, and geotechnical engineering recommendations for the proposed project.

Shannon & Wilson participated in this project as a subconsultant to Jacobs Engineering Group, Inc. (Jacobs). Our scope of services for the project was specified in our Professional Services Task Order 148021898 dated October 4, 2021.

We appreciate the opportunity to be of service to you on this project. If you have questions concerning this report, or we may be of further service, please contact us.

Sincerely, SHANNON & WILSON

Jason Buenker, Ph.D., P.E., G.E. Gregory R. Fischer, Ph.D.

Geotechnical Engineer President

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CONTENTS

1 Introduction

2 Project and Site Description

3 Subsurface Explorations and Laboratory Testing

3.1 Field Investigation

3.2 Geotechnical Laboratory Testing

3.3 Previous Explorations

4 Regional Geology and Subsurface Conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.3 Groundwater

4.4 Subsurface Variations

5 Geologic Hazard Evaluation

5.1 Seismic Hazards

5.2 Corrosion

6 Geotechnical Recommendations

6.1 Ground Motion Design Parameters

6.2 Foundations

6.2.1 Spread/Strip Footings

6.2.2 Mat Foundations

6.2.3 Floor Slab Support

6.3 Lateral Earth Pressures and Lateral Resistance

6.4 Foundation Uplift

6.5 Surface Drainage

7 Construction Considerations

7.1 Dewatering

7.2 Earthwork

7.2.1 Site Preparation

7.2.2 Excavation

7.2.3 Foundation and Slab Subgrade Preparation

7.2.4 Proof-rolling

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7.2.5 Fill Placement and Compaction

7.2.6 Temporary Slopes

8 Limitations

9 References

Exhibits Exhibit 2-1: New Facilities Exhibit 5-1: Corrosion Testing Results Exhibit 6-1: Seismic Design Ground Motion Parameters Exhibit 6-2: Recommended Lateral Earth Pressure Values

Figures Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Figure 3: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Subsurface Explorations Appendix B: Laboratory Test Results Appendix C: Previous Explorations Important Information

106739-001 February 2022

1 INTRODUCTION

This report presents the results of our subsurface exploration and testing program and geotechnical engineering recommendations for the proposed National Park Service (NPS) El Portal Wastewater Treatment Plant (WWTP) Project (the Project) in El Portal, California (Figure 1).

Our conclusions and recommendations are based on:

Our understanding of the Project and information provided by Jacobs;

Subsurface conditions observed in the explorations; and

The results of testing performed on samples collected from the explorations.

The objective of our studies was to provide geotechnical recommendations and construction considerations, as presented herein, for the proposed new facilities. This report should not be used for other purposes without Shannon & Wilson’s review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located in the locality of El Portal in Mariposa County, California (Figure 1).

The Project site is approximately 8 miles west of Yosemite National Park adjacent to the Merced River along California State Route 140. The Project includes the construction of 12 new facilities within the existing plant site, which are described in Exhibit 2-1 below.

The Project location is situated on an abandoned meander bend on the north side of the Merced River. The existing wastewater treatment plant is adjacent to the National Park Service El Portal Maintenance/Warehouse complex and covers nearly 6 acres of paved and landscaped areas surrounding the treatment facility structures. Refer to Figure 2 for a Project map.

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Exhibit 2-1: New Facilities

New Facilities Structure Description Approximate Embedment

Depth Below Grade

Headworks Precast Concrete Wall/Bar Joist Roof 5 feet

Headworks Effluent Pump Station Cast-in-place Concrete Basin 10 – 15 feet

Odor Control Cast-in-place Concrete Basin 5 feet

Blower Building Precast Concrete Wall/Bar Joist Roof 2 – 5 feet

Bioreactor 1, 2, and 3 Cast-in-place Concrete Basin 10 feet

Secondary Clarifiers Cast-in-place Concrete Basin 10 feet

Chemical Building Precast Concrete Wall/Steel Beam Framed Roof

2 – 5 feet

Digester Complex and Dewatering Facility

Concrete Basin, Precast Concrete Wall/Bar Joist Roof

5 – 10 feet

Electrical Building Precast Concrete Wall/Bar Joist Roof 2 – 5 feet

Operations Building Precast Concrete Wall/Bar Joist Roof 2 – 5 feet

Maintenance Building Precast Concrete Wall/Bar Joist Roof 2 – 5 feet

RAS/WAS Pump Station Precast Concrete Wall/Bar Joist Roof 2 – 5 feet

NOTES:

Based on information provided in Attachment A-1 in the Draft Professional Services Master Agreement and modified based on Civil Site Plan provided by Jacobs.

3 SUBSURFACE EXPLORATIONS AND LABORATORY

TESTING

3.1 Field Investigation

Shannon & Wilson conducted a field exploration program from October 12 through 15, 2021, to explore subsurface conditions at the Project site. The subsurface exploration program consisted of drilling and sampling 6 borings, designated as borings B-1 to B-6.

Refer to Figure 2 for the approximate boring locations. Borings B-4 and B-6 were advanced to a depth of approximately 20 feet below the ground surface (bgs) and borings B-1, B-2, B-3, and B-5 were advanced to a depth of approximately 40 to 45 feet bgs.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used to classify soil and rock samples recovered from the borings.

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3.2 Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings. Index tests included natural water content and grain size analysis. Engineering properties tests included corrosion and uniaxial compressive strength. Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content and fines content are also shown on the individual boring logs included in Appendix A.

3.3 Previous Explorations

Existing subsurface data available for the site includes logs for 2 test pits by BSK & Associates (1993). Appendix C includes these logs and a site plan showing the approximate test pit locations.

Additionally, Shannon & Wilson obtained 3 monitoring well completion reports in the Project area from the California Department of Water Resources publicly available Well Completion Report Map Application (2019). The well completion reports for the wells designated MW-2, MW-3, and MW-4 are provided in Appendix C. A site plan showing the location of these wells was obtained from a California Regional Water Quality Control Board, Central Valley Region report of Waste Discharge Requirements for the El Portal Wastewater Treatment Facility (2019). The site plan is included in Appendix C.

4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

The Project site is located on the western flank of the Sierra Nevada, a northerly trending mountain range formed from an uplifted and west-tilted fault block. The Project area is underlain by strongly deformed, but weakly metamorphosed, sedimentary rock of Paleozoic and early Mesozoic age deformed by the emplacement of Cretaceous plutonic rock (Huber and others, 1989). These granitic intrusive rocks are exposed east of the Project vicinity. The Paleozoic rock exposed north and south of the Merced River (near the Project) site comprise a series of stratified rock units that trend north northwesterly with steeply dipping to vertical bedding striking parallel to the trend of the rock units (Bateman and Krauskopf, 1987). The rock is deeply dissected by the Merced River and its tributaries.

Alluvium comprised of granitic and other rock eroded from upstream sources are deposited along the flanks of the Merced River.

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4.2 Subsurface Conditions

Boring B-5, which was performed in a location overlying the existing pavement, encountered approximately 4 inches of asphalt. Fill was encountered in all borings, except boring B-6, and consisted of loose to very dense sand with varying amounts of silt and gravel. Fill was encountered to depths of 4.0 to 7.5 feet bgs. Based on the test pits completed by BSK & Associates (1993) for the previous geotechnical report, cobbles and boulders up to 30 inches in size were encountered in the upper 5 feet of test pit TP-2. While the diameter of our samplers prohibits us from collecting cobble- or boulder-sized samples from the borings, we did not observe drill action or low recovery indicating cobbles and boulders where fill was observed.

Alluvium was encountered below the fill to the termination depth of the borings. The alluvium observed contained varying amounts of boulders and cobbles in a matrix of sand with varying amounts of silt and gravel. Boulders and cobbles were inferred from drill action and portions of boulders and cobbles were observed in our samples. Borings B-2, B-3, and B-5 encountered more boulders and cobbles than borings B-1, B-4, and B-6. The boulders and cobbles consisted of completely to slightly weathered granitic and metasedimentary rock.

4.3 Groundwater

Groundwater was not encountered in any of our borings; however, the use of water during rock coring in borings B-1, B-2, B-3, and B-5 and mud rotary in boring B-4 may have masked the presence of groundwater. In the previous geotechnical report by BSK & Associates (1993), groundwater was encountered in one test pit (TP-2) at a depth of approximately 12 feet at the time of excavation. Additionally, 3 monitoring wells, designated MW-2, MW-3, and MW-4, were installed at the site on February 23, 1992 (California Department of Water Resources, 2019). The static water level measured in each of the 3 wells on February 24, 1992 was 10 feet bgs. Groundwater fluctuations are likely and will depend on seasonal variations, local precipitation and runoff, and flood events.

4.4 Subsurface Variations

The explorations were performed to evaluate subsurface conditions at the Project site. Our observations are specific to the locations, depths, and times noted on the logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions.

Potential variation includes, but is not limited to:

106739-001 February 2022

The conditions between explorations may be different, especially due to the presence of boulders and cobbles, differences in densities or gradations of fill.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

If conditions different from those described herein are encountered during construction, we should review our description of the subsurface conditions and reconsider our conclusions and recommendations.

5 GEOLOGIC HAZARD EVALUATION

5.1 Seismic Hazards

Based on a database by the U.S. Geological Survey (USGS), the nearest confirmed late Quaternary fault to the Project is the Silver Lake Fault, approximately 38 miles to the northeast (Sawyer and Bryant, 1995). The fault is a normal fault running north to south with movement on the order of 0.2 to 1.0 mm per year. Also based on the geologic database by the USGS, the late Quaternary Foothills Fault system is approximately 38 miles to the northwest (Bryant, 2017). The fault runs north to south, but the type of fault, dip direction, and rate of movement is not specified. Based on the distance of both faults and the direction of movement, it is our opinion that the potential for ground surface fault rupture at the Project site is low.

5.2 Corrosion

The soil encountered at the Project site can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, selected samples were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Exhibit 5-1 and Table B-1 in Appendix B.

Exhibit 5-1: Corrosion Testing Results

Boring Sample Material pH Resistivity (ohm-cm)

Water-Soluble Sulfates

Water-Soluble Chlorides

B-1 S-5 Alluvium 7.7 9,109 0.001 0.0003

B-3 S-1 Fill 8.0 9,279 0.001 0.0002

B-4 S-5 Alluvium 7.7 7,153 0.007 0.0007

NOTES:

Water-soluble sulfate and chloride values are shown as percent weight in dry soil.

ohm-cm = ohm-centimeter

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Guidelines in the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (2020) indicate that resistivity measured below 2,000 ohm-centimeters should be considered corrosive. The resistivity measured in our tests were all higher than 7,000 ohm-centimeters. As such, AASHTO (2020) would not consider these soils corrosive.

Soil or rock with sulfate concentrations more than 1,000 parts per million (0.1%) are indicative of potential degradation based on AASHTO (2020). The concentration of water-soluble sulfates measured in the samples was 0.007% by weight or less; therefore, AASHTO would suggest that the concrete design does not need to be sulfate resistant. Similarly, ACI 318-19 (ACI, 2019) classifies these soils as exposure class S0, negligible, on concrete exposed to soil.

The test results and the above discussion are provided to assist the designer in the selection of project materials, concrete type, or other features with respect to corrosion. As appropriate, the designer should consider protective measures, such as coatings, upsizing for section loss, or using alternative materials to reduce the corrosion potential.

6 GEOTECHNICAL RECOMMENDATIONS

6.1 Ground Motion Design Parameters

We evaluated seismic design criteria for the proposed structures in accordance with the 2018 International Building Code (International Code Council, 2017), which has adopted the American Society of Civil Engineers (ASCE) 7-16 Design Code for Minimum Design Loads on Buildings (ASCE, 2017). We characterized the site class using Standard Penetration Test (SPT) N-values (blow counts) noted in our exploration logs and our characterization of geologic conditions at the site. We concluded the site can be classified as Site Class C.

Seismic design parameters for Site Class C are provided in Exhibit 6-1.

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Exhibit 6-1: Seismic Design Ground Motion Parameters

Parameter Value

PGA (g) (Site Class B) 0.213

SS (g) 0.495

S1 (g) 0.196

Fpga (Site Class C) 1.2

Fa (Site Class C) 1.3

Fv (Site Class C) 1.5

PGAM (PGA x Fpga) (g) 0.256

SMS (SS x Fa) (g) 0.643

SM1 (S1 x Fv) (g) 0.295

SDS (2/3 x SMS) (g) 0.429

SD1 (2/3 x SM1) (g) 0.196

NOTES:

Calculated in accordance with IBC 2018 and ASCE 7-16 (2016).

g = gravity; PGA = peak ground acceleration

Additionally, we performed analyses to estimate the liquefaction and seismic compression potential at the site. Liquefaction may occur in loose, saturated, granular soils when subjected to earthquake ground shaking. We evaluated liquefaction potential using methods by Cetin and others (2004), Boulanger and Idriss (2014), and Youd and others (2001). Based on our evaluation, we conclude that the potential for liquefaction during a seismic event is low and that significant liquefaction-induced settlement is not likely.

Seismic compression may occur when loose, granular soils above the groundwater table are rearranged into a denser configuration during seismic shaking, which can cause settlement.

We used correlations by Ishihara and Yoshimine (1992) and Tokimatsu and Seed (1987) to evaluate seismic compression. We calculated that the total seismic compression observed at the ground surface would be less than 0.25 inch. We expect seismic compression-induced settlement to occur in the undocumented fill, which we recommend be excavated and replaced (see Section 6.2) prior to installing new foundations for the Project. It is important that the new fill materials be properly placed and compacted (see Section 7.2.5) to reduce the likelihood of additional seismic compression associated with improperly compacted fill.

6.2 Foundations

We recommend that the proposed structures be supported by either spread/strip footings or mat foundations. Based on the conditions encountered in our borings, undocumented fill was encountered to a maximum depth of 7.5 feet bgs. The fill was consistently classified as poorly graded sand with silt and gravel but was of variable relative density, ranging from

106739-001 February 2022 loose to very dense. Based on the variable relative density of the fill, and because the placement of the fill and its characteristics are not documented, we recommend that the undocumented fill beneath all footings and slabs be over-excavated, moisture-conditioned, and replaced in a controlled fashion. We recommend that the depth of over-excavation be based on field observations by a geotechnical engineer.

Several building foundations are proposed to be founded deeper than the fill, and we recommend that those foundations be placed on a minimum of 12 inches of over-excavated, moisture conditioned, and recompacted material, due to the variability of the cobbles and boulders throughout the site. We also recommend assuming a design groundwater level of 10 feet bgs based on the groundwater depth observed in previous explorations (see Section 4.3).

We understand that the NPS may be willing to accept an increased risk of poor structure performance (i.e., increased settlement) to reduce costs and avoid archeological-related excavation concerns, for structures supported at or near the existing ground surface.

Essentially, this would involve reducing the amount of over-excavation of undocumented fill. In determining if this approach is acceptable, we recommend that the design team and NPS consider the depth of excavation required to reach the base of the excavation (i.e., how much undocumented fill will remain), the loading of the structure (lightly loaded structures would be at less risk than heavily loaded structures), and the structure's tolerance for differential settlement (i.e., applying only to structures that could tolerate more settlement).

If the undocumented fill will not be completely removed, we recommend that at least 3 feet of fill be removed, the subgrade evaluated by a geotechnical engineer for any signs of deleterious materials (and the excavation continued deeper if such materials are observed), and the subgrade be compacted with a large-diameter vibratory compactor in accordance with the criteria in Section 7.2. The size and vibration frequency of the compactor and minimum number of passes should be specified to induce settlement in any undocumented fill that is not removed.

6.2.1 Spread/Strip Footings

We recommend designing spread/strip footings for a net allowable bearing capacity of 3,500 pounds per square foot (psf). These capacities can be increased by 33% for transient wind or seismic loads. Strip footings should have a minimum width of 2 feet and rectangular (spread) footings a minimum width of 4 feet. We recommend foundation elements be founded a minimum embedment of 24 inches below grade (the frost depth at the site is 5 to 10 inches). We anticipate a potential total settlement of footings to be on the order of 1 inch and differential settlement on the order of 0.5 inch over a span of 30 feet. The majority of the settlement is expected to occur as the load is applied.

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6.2.2 Mat Foundations

We recommend designing mat foundations for a gross allowable bearing pressure of 2,000 psf. For this value, we anticipate a settlement of about 1 inch. However, we do not anticipate that bearing capacity will control the mat foundation design. Instead, we anticipate that the design will be governed by soil-structure interaction and the evaluation of calculated mat settlement (deflections), shears, and moments. Geotechnical information required for this analysis is the subgrade reaction modulus, which is analogous to a spring that can be applied in the structural model to represent the soil/rock response to applied stress. This value is a function of the dimensions of the mat and the stiffness of the underlying soil. For structural design, we recommend using a vertical modulus of subgrade reaction (k) value of 30 to 40 pounds per cubic inch (pci). This k value is valid for mat sizes that are at least 20-feet-wide.

6.2.3 Floor Slab Support

Slab-on-grade floors may be used beneath the proposed structures. As described at the beginning of Section 6.2, all undocumented fill should be excavated and any buildings founded deeper than the fill should be placed on a minimum of 12 inches of over-excavated material. The over-excavated areas should be replaced with moisture conditioned, compacted fill as described in Section 7.2.5. A capillary break layer should be placed below the slab and should outlet through the foundation walls. In addition, a vapor barrier could be considered by the designer to reduce the potential for moisture infiltration through the slab.

6.3 Lateral Earth Pressures and Lateral Resistance

The lateral earth pressures acting on structure walls depend on many factors, including surcharge loads, the soil type/consistency, and whether the top of the wall is free to yield or deflect laterally during and after excavation. If the top of the wall is free to yield a minimum of 0.1% of the wall height (i.e., 0.001 times the height [H]), the soil pressures will generally be less (i.e., active condition) than if the wall is not able to yield this amount due to stiffness or resistance of the wall (i.e., at-rest condition). We anticipate that at-rest earth pressures will be appropriate for the structures. Our static earth pressure recommendations are presented in Exhibit 6-2. The static lateral earth pressures assume the structure walls are backfilled with properly compacted granular material in a 1 horizontal to 1 vertical (1H:1V) zone extending upward from the base of the structure from a point 1.5 feet behind the wall.

These pressures also assume a vertical wall face and a flat backslope. Clay, cobbles, and boulders are not suitable for reuse as backfill. We anticipate that the existing fill materials would be suitable for reuse as backfill for retaining walls if cobbles and boulders encountered are screened out.

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Seismic active lateral earth pressure coefficients were determined based on the Mononabe- Okabe method (AASHTO, 2020), and seismic at-rest earth pressure coefficients were determined based on methods developed by Zhang and others (1998). Per AASHTO (2020), the pressure distribution shape for dynamic active earth pressures is triangular, with the resultant force (PAE) acting at the lower third of the wall height (h/3). The parameters are provided in Exhibit 6-2.

Exhibit 6-2: Recommended Lateral Earth Pressure Values

Parameter Coefficient

Above Water Table Equivalent Fluid

Pressure (pcf)1

Submerged Equivalent Fluid

Pressure (pcf)2

Static Active Earth Pressure KA = 0.31 39 82 Static At-rest Earth Pressure Ko = 0.47 59 92 Static Passive Earth Pressure3 Kp = 3.0 375 250 Dynamic Active Earth Pressure KAE = 0.38 48 87 Dynamic At-rest Earth Pressure Koe = 0.55 69 97

NOTES:

Based on granular soil with an assumed unit weight of 125 pcf and a friction angle of 32 degrees for the retained soil.

Includes water pressure based on design groundwater depth of 10 feet bgs.

Static Passive Earth Pressure coefficient is reduced by a factor of 2.

pcf = pounds per cubic foot

Surcharge loads from vehicles/traffic and construction equipment will induce additional lateral loads on structure walls. The pressures provided above do not account for surcharge loads. Lateral loads due to various types of surcharges may be calculated by multiplying the surcharge by the provided pressure coefficient. Surcharge loads should be applied as recommended in Figure 3.

Lateral loads can be resisted by friction along the base of the foundation using an allowable coefficient of sliding resistance of 0.35. This allowable value for coefficient of sliding resistance includes a factor of safety of 1.5. In addition, we recommend an allowable passive pressure as provided in Exhibit 6-2. The allowable passive earth pressure coefficients include a factor of safety of 2 to account for uncertainty in soil properties and to limit the lateral deflection necessary to mobilize the passive resistance. Because of the potential for disturbance of near surface soils, passive resistance should be ignored in the upper 12 inches; however, the equivalent fluid pressure line may be projected down from the ground surface. In cases where the passive resistance is assumed to act on the below-grade portion of a structure that moves laterally into the soil, the active earth pressure described above should also be considered to act on any below-grade portion of the structure that moves laterally away from the soil.

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6.4 Foundation Uplift

Some of the proposed foundation depths are below the recommended design groundwater depth. As such, uplift pressures should be included on these structures. Sufficient mass or uplift resistance will be required to counteract uplift loads created by hydrostatic forces acting on the bottom of the foundation. We recommend using one or more of the following methods to resist or compensate for groundwater uplift pressures: soil-structure friction, structure weight, and/or thickened or widened structure base (mat foundation).

Typically, uplift can be resisted by the weight of the structure and frictional resistance between the structure walls and backfill material. When evaluating the weight of a structure for uplift resistance, only those portions of the structure on which the uplift forces act and are constructed as a coherent mass should be considered. To determine soil-structure friction, we recommend using 90% of lateral earth pressures provided in Exhibit 6- 2 multiplied by an allowable coefficient of friction of 0.25. This value includes a factor of safety of 1.5 and assumes backfill of the wall consists of a granular fill material. If an increase in structure weight is desired for uplift resistance, a thickened or widened base could be used. For a widened base, the base edge would extend past the structure wall to utilize the weight of material from the top of the base to the ground surface. For such a design, we recommend using a total soil unit weight of 125 pcf and to only include the weight of the soil directly above the footing extension. To determine soil-soil friction along the base of the vertical extension, we recommend multiplying by an allowable coefficient of friction of 0.40.

6.5 Surface Drainage

Surface drainage control can be critical in reducing the potential for soil movements to develop, as well as reducing the magnitude of any such movements. The ground surface around the structures should be sloped to provide positive drainage away from the foundation. We recommend providing a slope of at least 10% for the first 5 feet surrounding the buildings. Roof downspouts should discharge into the storm drain system. If this is not possible, roof downspouts should discharge beyond the limits of foundation backfill or a minimum of 5 feet. We recommend providing splash blocks and downspout extenders, or tightlining downspouts away from the building. Roof downspouts should not be connected into a perimeter foundation drain system.

7 CONSTRUCTION CONSIDERATIONS

The applicability of the design recommendations provided in this report is contingent on good construction practice. Poor construction techniques may alter conditions from those

106739-001 February 2022 on which our recommendations are based, resulting in reduced foundation capacity and increased settlement. The following sections present construction considerations for this Project.

7.1 Dewatering

Groundwater was not encountered during our subsurface exploration program; however, it was encountered during previous explorations in 1992 and 1993 (See Section 4.3). Based on the highest groundwater measured at the site during those previous explorations (10 feet bgs in the monitoring wells completed in 1992), we anticipate that groundwater may be encountered during excavation for some of the facilities. Should dewatering be required for some of the deeper facilities, we recommend that a dewatering designer and contractor be obtained for the project design.

7.2 Earthwork

7.2.1 Site Preparation

We recommend that pavement, brush, and other vegetation be cleared, and roots and stumps be removed from all areas to be improved. Any existing surficial organic topsoil and any soil containing organics also should be stripped and removed. The depth of this removal is anticipated to vary over the site. Pavement, topsoil, and organic-rich soils are not considered suitable for reuse as fill and should be removed from the site or stockpiled for reuse in landscaping areas.

As discussed previously, undocumented fill soils exist below the facilities. We recommend that all undocumented fill soils be removed beneath all areas of the site where structures are to be constructed.

7.2.2 Excavation

Shallow excavations (less than 5 feet) for foundations will likely occur within fill soils. We anticipate that fill soils can be excavated using conventional excavating equipment, such as a rubber-tired backhoe with a telescoping boom, or a tracked hydraulic excavator. Deeper excavations (greater than 5 feet) may encounter boulders and cobbles within the alluvial soils. Based on the structure and strength of the materials observed in our explorations, we anticipate that these materials can also be excavated using conventional excavating equipment.

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7.2.3 Foundation and Slab Subgrade Preparation

Excavations for mat or shallow foundations should be observed by a geotechnical engineering representative familiar with the subsurface conditions to evaluate the adequacy of the bearing stratum and confirm that the subsurface conditions at and below the bearing elevations are consistent with design assumptions and all undocumented fill has been removed. For foundations and slabs constructed on granular soils, we recommend that the foundation subgrade be proof-rolled or probed to determine its suitability.

Subgrade excavations should be cleaned of all undocumented fill, debris, or loose/soft material prior to concrete placement and should be kept free of water at all times. If any structures require dewatering to reach the base of excavation, it will be important to maintain the soil at the base of the excavation in a firm and undisturbed condition. If groundwater is flowing into the base of the excavation or is near the subgrade elevation it can loosen/soften the subgrade material. Therefore, we recommend that the groundwater level be maintained a minimum of 3 feet below the base of all excavations.

Where loose or disturbed sands are encountered in a dry to moist state, it is generally possible to recompact these soils in place to provide suitable foundation support. However, if the sand is wet, compaction may be difficult without first drying the soils. In our opinion, the moisture content range that would permit adequate compaction would depend on the fines content but would likely be from about 3% below to 3% above the optimum moisture content, as determined by ASTM D1557 (ASTM International, 2021). If compaction of the exposed materials is not possible because of wet or otherwise unsatisfactory conditions, the material should be over-excavated to a depth where medium dense or denser, undisturbed sand is encountered and replaced with compacted Granular Fill to re-establish adequate foundation support.

7.2.4 Proof-rolling

Subgrades under mat or shallow foundations should be proof-rolled prior to concrete placement using a 10-ton (minimum) static roller. Proof-rolling helps identify areas that are loose, soft, or yielding. Any loose, soft, or yielding areas identified by proof-rolling should be compacted in place or removed and replaced with Granular Fill. Care should be taken during proof-rolling and subgrade preparation to avoid disturbing subgrade soils and supporting soils that will remain in place, as they can rut under repeated construction traffic.

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7.2.5 Fill Placement and Compaction

Granular Fill should be used to backfill any overexcavation beneath foundations and slabs to provide suitable support and to reduce the long-term compressibility of these materials.

Granular Fill should consist of native or imported sand and gravel with less than 12% fines (material passing the U.S. Standard No. 200 sieve) and a minimum particle size of 3 inches.

We anticipate that the undocumented fill on site may be suitable for reuse as Granular Fill after excavation if properly moisture conditioned and compacted. Should cobbles and boulders be encountered in fill materials, it may make the excavated fill unsuitable for reuse as structural fill. Any cobbles and boulders encountered should be screened out before reuse. Imported material classified as GW, GW-GM, GP, GP-GM, SW, or SW-SM according to the Unified Soil Classification System (USCS), would also be suitable for Granular Fill.

Fill materials should be placed in horizontal lifts, with the loose lift thickness not to exceed 12 inches for heavy equipment compactors and 6 inches for hand-operated compactors.

Compaction of backfill adjacent to walls can result in higher lateral earth pressures against the wall. As such, small equipment that is hand-operated shall only be used within a line extending upward from the base of the structure at 0.5H:1V, or at least 3 feet from the wall, whichever is greater.

All fill materials shall be compacted to a dense/hard and unyielding condition. Granular Fill should be compacted to a minimum of 95% of its Modified Proctor maximum dry density (ASTM D1557 (ASTM International, 2021)). The moisture content of Granular Fill should be within plus or minus 3% of the optimum moisture content.

7.2.6 Temporary Slopes

Temporary excavations will be required to construct the proposed structures. The Contractor will be responsible for excavation stability during construction. As such, the Contractor should evaluate the stability of temporary slope and excavation configurations that may be required during construction.

The safe slope for the excavation of subsurface materials depends on many factors, including: (1) the presence of groundwater; (2) the type, density, and shear strength of the subsurface materials; (3) the depth of excavation; (4) the presence of adjacent structures;

(5) surcharge loading adjacent to the excavation (including excavated material, existing dead or live loads, and construction equipment); and (6) time of construction.

To the extent that temporary excavation slopes are feasible, the following slope conditions are for cost estimating and planning purposes only and limited to slopes up to 20 feet in height. We anticipate that temporary excavations in cohesionless soils can be made at

106739-001 February 2022 slopes of 1.5H:1V to 1H:1V in granular cohesionless soils. Flatter slopes would likely be required if groundwater is encountered during excavation. If temporary slopes will be made, they should be consistent with the Occupational Safety and Health Administration (OSHA) guidelines contained in 29 CFR 1926, Subpart P (OSHA, 1999).

Consistent with conventional practice, the Contractor should be responsible for the actual temporary excavation slopes and shoring, including methods, sequence, and schedule of construction. The Contractor is able to observe the nature and conditions of the subsurface materials encountered and should evaluate the factors discussed above. If instability is observed, slopes should be flattened or shored. All excavations should be accomplished in accordance with local, state, and federal safety regulations.

8 LIMITATIONS

This report was prepared for the exclusive use of Jacobs and the National Park Service for use in design of the El Portal WWTP Project. It should be made available to prospective contractors and/or the Contractor for information on factual data only, and not as a warranty of subsurface conditions. Within the limitations of scope, schedule, and budget, the analyses, conclusions, and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

This report should not be used without our approval if any of the following occurs:

Conditions change due to natural forces or human activity under, at, or adjacent to the site.

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analyses, conclusions, and recommendations may be affected.

If the site ownership or land use has changed.

More than 5 years has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses, conclusions, and recommendations.

Unanticipated soil conditions are commonly encountered and cannot be fully determined by a limited boring and testing program. Therefore, some contingency fund is recommended to accommodate such potential extra costs. The scope of our present work

106739-001 February 2022 did not include environmental assessments or evaluations regarding the presence or absence of wetlands, or hazardous or toxic substances in the soil, surface water, groundwater, or air, on or below or around this site, or for the evaluation or disposal of contaminated soils or groundwater should any be encountered.

Shannon & Wilson has prepared the attached document, "Important Information about Your Geotechnical Report," to assist you and others in understanding the use and limitations of our reports.

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9 REFERENCES

American Concrete Institute (ACI), 2019, Building code requirements for structural concrete and commentary, Farmington Hills, Mich., ACI 318-19.

American Association of State Highway and Transportation Officials (AASHTO), 2020, AASHTO LRFD bridge design specifications, Customary U.S. units, 9th edition:

Washington, D.C., American Association of State Highway and Transportation Officials.

American Society of Civil Engineers (ASCE), 2017, Minimum design loads and associated criteria for buildings and other structures: Reston, Va. American Society of Civil Engineers, ASCE Standard ASCE/SEI 7-16, 2 v.

ASTM International, 2021, Standard test methods for laboratory compaction characteristics of soil using modified effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)), D1557-12(2021):

West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.08, soil and rock (I): D420 - D5876, 13 p., available: www.astm.org.

Bateman, P.C., and Krauskopf, K.B., 1987, Geologic Map of the El Portal Quadrangle, West- Central Sierra Nevada, California: Miscellaneous Field Studies Map MF-1998, U.S.

Geological Survey (USGS), Reston, Virginia.

Boulanger, R. W. and Idriss, Izzat M., 2014, CPT and SPT based liquefaction triggering procedures: Univesity of California at Davis, Center for Geotechnical Modeling, report no. UCD/CGM-14/01, 134 p.

Bryant, W.A., compiler, 2017, Fault number 26, Foothills fault system, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 01/12/2022 02:03 PM.

BSK & Associates, 1993, Geotechnical Engineering Investigation, El Portal Wastewater Treatment Plant Expansion, Mariposa County, California, June 1.

California Department of Water Resources, 2019, Well Completion Report Map Application, 03S20E18_00393138.pdf, accessed January 12, 2022, at ArcGIS web application at https://dwr.maps.arcgis.com/apps/webappviewer/index.html?id=181078580a214c0 098e2da28f8623b37.

California Regional Water Quality Control Board, Central Valley Region, 2019, Order R5- 2019-0069, NPDES No. CA0081759, Waste Discharge Requirements for the United States Department of the Interior, National Park Service, Yosemite National Park, El Portal Wastewater Treatment Facility, Mariposa County, October 11.

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Cetin, K.O., Seed, R.B, and others, 2004, Standard Penetration Test-Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential: Journal of Geotechnical and Geoenvironmental Engineering, v. 130, no. 12, pp. 1314 – 1340.

Huber, N. K., P. C. Bateman, and C. Wahrhaftig, 1989, Geologic map of Yosemite National Park and vicinity, California, Denver, Colorado: Misc. Investigations Series Map I- 1874, USDI Geological Survey

International Code Council, Inc., 2017, International building code 2018: Country Club Hills, Ill., International Code Council, Inc., 726 p.

Ishihara, K., and Yoshimine, M., 1992. “Evaluation of settlements in sand deposits following liquefaction during earthquakes.” Soils and Foundations, JSSMFE, Vol. 32, No. 1, March, pp. 173-188.

Occupational Safety & Health Administration (OSHA), 1999, 29 CFR 1926, Subpart P.

Sawyer, T.L., and Bryant, W.A., compilers, 1995, Fault number 42, Silver Lake fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 01/12/2022 01:48

PM.

Tokimatsu, K. and Seed, H.B., 1987. “Evaluation of Settlement in Sands Due to Earthquake Shaking.” ASCE Journal of Geotechnical Engineering, Vol. 113, No. 8, August 1987.

Youd, T. L.; Idriss, I. M.; Andrus, R. D.; and others, 2001, Liquefaction resistance of soils:

summary report from the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils: Journal of Geotechnical and Geoenvironmental Engineering, v. 127, no. 10, p. 817-833.

Zhang, J.-M.; Shamato, Yasuhiro; and Tokimatsu, Kohji, 1998, Seismic earth pressure theory for retaining walls under any lateral displacement: Soils and Foundations, v. 38,

no. 2, p. 143-163.

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