At05_GeotechReport_18Oct24_0003.pdf

Geotechnical ExploraƟon Report

GARNET HILL RECREATION AREA – VARIOUS IMPROVEMENTS

U.S. Highway 50 Near Ely, Nevada

Prepared for:

S&B Christ ConsulƟng, LLC

9555 Hillwood Drive, Suite 160 Las Vegas, NV 89134

Prepared By:

UES

4480 W. Hacienda Avenue, Suite 104

Las Vegas, NV 89118

October 18, 2024 Project No. 4030.2400162

UES

4480 W. Hacienda Avenue, Suite 104

Las Vegas, NV 89118

p. 702.873.3478 | TeamUES.com

Environmental ConsulƟng | Geotechnical Engineering | Materials TesƟng & InspecƟons OccupaƟonal Health & Safety | Building Sciences & Code Compliance | Virtual Design ConsulƟng

October 18, 2024

S&B Christ ConsulƟng, LLC 9555 Hillwood Drive, Suite 160 Las Vegas, NV 89134

AƩenƟon: Mr. Daniel Kelley, P.E.

(702)202-6004 dkelley@SBCC-US.com

Reference: Geotechnical Engineering Report Garnet Hill RecreaƟon Area – Various Improvements U.S. Highway 50 Near Ely, Nevada Project No: 4030.2400162

UES is pleased to submit this Geotechnical Engineering Report for the referenced project. This report includes the results from the field exploraƟon, geological reconnaissance and laboratory tesƟng program, along with recommendaƟons for use in the preparaƟon of the appropriate design and construcƟon documents for this project.

UES appreciates the opportunity to provide this Geotechnical Engineering Report and looks forward to conƟnuing parƟcipaƟon during the design and construcƟon phases of this project. UES also has great interest in providing construcƟon services, including materials tesƟng and inspecƟon services during the construcƟon of this project, and will be glad to meet with you to further discuss how we can be of assistance as the project advances.

If there are quesƟons pertaining to this report, or if UES may be of further service, please contact us at your convenience.

Respecƞully, UES

Prepared by: Reviewed By:

Sarah Schick Lee J. Mitchell, P.E.

Geotechnical Project Manager Senior Geotechnical Engineer

Garnet Hill RecreaƟon Area – Various Improvements

Page-i

4480 W. Hacienda Avenue, Suite 104, Las Vegas, NV 89118

p. 702.873.3478 | TeamUES.com

Table of Contents

1.0 IntroducƟon

1.1 Proposed Development

1.2 Scope of Work

1.3 Figures and AƩachments

2.0 Site InformaƟon

2.1 Site DescripƟon

2.1.1 Egan Crest Trailhead

2.1.2 Garnet Hill Sign – US-50 and Pole Line Road

2.1.3 Narrow Road

2.1.4 Garnet Hill Upper and Lower Campground

2.1.5 Garnet Hill RecreaƟon Area

2.2 Site History

2.3 Geologic History

2.4 Seismic Site Class

2.5 GeoHazards Assessments

2.5.1 Historic Seismicity

2.5.2 Seismic Hazards

2.5.3 Landslides

2.5.4 Soil Expansion PotenƟal

3.0 Field ExploraƟon & Laboratory Program

3.1 Field AcƟviƟes

3.2 Lab Program

3.3 Subsurface CondiƟons

3.4 Groundwater

3.4.1 Groundwater Effect on Development and Seasonal Water

3.5 Corrosion

3.5.1 Soil Corrosion PotenƟal

4.0 Engineering Analysis

4.1 Environmental and Human Health Hazards

5.0 Conclusions and RecommendaƟons

Page-ii

5.1 Geotechnical Discussion

5.2 Site PreparaƟon

5.2.1 Site Clearing

5.2.2 ExcavaƟon

5.3 Earthwork

5.3.1 Subgrade PreparaƟon

5.3.2 Fill Materials

5.3.3 Fill Placement and CompacƟon

5.3.4 On-site Soil Suitability for Use in Fill ConstrucƟon

5.3.5 Permanent Slopes

5.4 FoundaƟons

5.4.1 Outdoor Amphitheater and Roadway Signs

5.4.2 Shade Structures and Concrete Dumpster Pads

5.4.3 ADA Vault Toilets

5.4.4 Earthen Berm (Egan Crest)

5.5 Exterior Flatwork ConstrucƟon (including paved walking trails)

5.6 Drainage and Moisture ProtecƟon

5.7 Lateral Earth Pressures and Retaining Walls (including ada vault toilet)

5.8 Pavement Design

5.8.1 Asphalt Pavement (Pole Line Road)

5.8.2 On-site Pavements (Parking Areas)

5.8.3 Aggregate Base Parking Areas

5.9 Plan Review

5.10 ConstrucƟon Items

6.0 Geotechnical Risk and LimitaƟons

Page-iii

FIGURES

Overall Site Map Figure 1 Boring Map B-1 through B-3 Figure 2 Boring Map B-4, Slope 1 through Slope 3 Figure 3 Boring Map B-5 and B-6 Figure 4

APPENDIX A – GENERAL PROJECT INFORMATION, LABORATORY TESTING AND RESULTS

Logs of Borings 1 through 9 Unified Soil ClassificaƟon System 10

GradaƟon Test Results 11 through 15 Laboratory Results Summary 16 Chemical Test Results 17 through 21

Page-1

1.0 INTRODUCTION

Nova Geotechnical and InspecƟon Services dba UES, Consultant, has completed a field exploraƟon and geotechnical evaluaƟon for the Garnet Hill RecreaƟon Area project. Sharon Christ, represenƟng S&B Christ ConsulƟng, LLC, authorized UES services on August 14, 2024, by signing UES Proposal No.

4030.0524.00031 and the ‘Request for Change Order’ document dated August 29, 2024.

The site is located along U.S. Highway 50 near Ely, Nevada. The general locaƟon of the site is shown in Figure No. 1, Vicinity Map.

The purpose of our services was to provide informaƟon and geotechnical engineering recommendaƟons relaƟve to:

• Subsurface soil condiƟons

• General geology of the area

• FoundaƟon design and construcƟon

• Lateral earth pressure and retaining wall design parameters

• Slab-on-grade design and construcƟon

• Pavement design and construcƟon

• Slope Stability Analysis

• Earthwork

This report is for the purpose of providing geotechnical engineering requirements. The scope of our services for this project did not include any environmental assessment or invesƟgaƟon for the presence or absence of hazardous or toxic material in structures, soil, surface water, groundwater, or air, below or around this site.

1.1 PROPOSED DEVELOPMENT

The project site consists of recreaƟonal BLM land parƟally developed with day-use faciliƟes. The planned construcƟon sites include Egan Crest Trailhead, Garnet Hill Lower Campground, Garnet Hill Upper Campground, and Garnet Hill Trailhead. The site construcƟons/improvements include the following:

Egan Crest Trailhead o Parking area enlargement o ADA accessible vault toilet o Concrete dumpster pad o ADA accessible day-use sites with steel shade structure o Earthen berm (max 600-feet)

Garnet Hill Campground (Upper and Lower) o ADA accessible group and individual camp sites with steel shade structure o ADA accessible vault toilet o Concrete dumpster pad

Garnet Hill Trailhead

Page-2 o Trailhead enlargement o Retaining wall construcƟon o ADA accessible day-use sites with steel shade structure o Break up rock at exisƟng rockhounding areas o Concrete or pavement trails to rockhounding areas and day-use sites o ADA accessible vault toilet (may be preserving exisƟng toilet)

Improved dirt access roads with drainage ditches

New signage at all sites

Gravel parking area and large sign at Garnet Hill/U.S. 50 intersecƟon

DemoliƟon of exisƟng vegetaƟon or structures at the proposed sites

Structural loads for the proposed buildings were not provided. We anƟcipate maximum dead- plus live-loads for columns and wall loading at approximately 60 kips and 2.0 kips per lineal foot, respecƟvely. There will be on-site paved areas. Based on the topography of the area, it is further anƟcipated that significant cut and fill will be required, parƟcularly at Garnet Hill Campgrounds and Trailhead.

1.2 SCOPE OF WORK

Our scope of work included the following:

Site reconnaissance

Review of United States Geological Survey (USGS) topographic maps, aerial photographs and available groundwater data

Review of geologic maps and fault maps

Review of seismic acƟvity within 100 kilometers (62 miles) of the site

Subsurface exploraƟon, including the drilling and sampling of nine borings to target depths ranging from approximately 15 to 16½ feet below the ground surface (bgs).

Bulk sampling of near-surface soils

Laboratory tesƟng of selected soil samples

Slope stability analysis of narrow secƟons on Pole Line Road

Engineering analyses

PreparaƟon of this report

1.3 FIGURES AND ATTACHMENTS

The following figures are included with this report:

1. Vicinity Map

2. Site Plan

Appended to this report are:

Appendix A

Page-3 o Logs of Soil Borings o United Soil ClassificaƟon System o General informaƟon regarding project concepts, exploratory methods used during our field invesƟgaƟon and laboratory test results not included on the Logs of Soil Borings o Laboratory Test Results

2.0 SITE INFORMATION

2.1 SITE DESCRIPTION

The project site is recreaƟonal land located approximately 8 miles Northwest of Ely, Nevada along Highway

50. The Robinson Copper Mine is to the northwest and downhill of the project site with the Egan Mountain range running from the NW-SE north of the site. Site condiƟons for each area were recorded during site reconnaissance visit on August 19, 2024 and drilling on September 17-18, 2024.

2.1.1 Egan Crest Trailhead

The Egan Crest project locaƟon is a total of approximately four acres, with a 1/3-acre gravel parking area that includes two shade structures with slab on grade concrete pads, and trail sign. The remainder of the site consists of historically graded naƟve material with sparce vegetaƟon.

2.1.2 Garnet Hill Sign – US-50 and Pole Line Road

This locaƟon is south of Pole Line Road at the intersecƟon of Hwy-50. The area consists of undisturbed, naƟve vegetaƟon with uƟlity infrastructure on the north side of Pole Line Road.

2.1.3 Narrow Road

Several areas along Pole Line Road (access road to Garnet Hill) will require road-widening, which will likely include excavaƟon techniques (including rock excavaƟon) at the toe of the slopes to the north. The slope North of Pole Line Road are approximately 10-12 degrees, with undisturbed vegetaƟon, surficial soils and gravels, and bedrock outcrops.

2.1.4 Garnet Hill Upper and Lower Campground

The upper and lower campground sites are located approximately 2.8 and 2.2 miles from Hwy-50 along Pole Line Road. The sites appear to have been used for primiƟve recreaƟon sites as evidenced by the fire rings and trash. There are several small two-track roads throughout these areas; however, the area is primarily undeveloped, with undisturbed surface vegetaƟon, surficial soils and gravels, and some bedrock outcrops. The upper campground has significant slopes in all direcƟons, likely requiring significant cut and fill, depending on final design.

2.1.5 Garnet Hill RecreaƟon Area

The Garnet Hill RecreaƟon Area is currently developed as a rockhounding trailhead including a vault toilet, railroad-Ɵe retaining wall, gravel parking area, and several small picnic areas and walking trails. NaƟve vegetaƟon with surficial soils and gravels exists at the site between the developed areas. Previous grading at the site has been done at the site Northwest of the vault toilet.

Page-4

Figure 2-1: Top LeŌ: View looking North at the Egan Crest Trailhead showing exisƟng shade structures and gravel parking area. Top Right: View looking east at undeveloped Lower Garnet Hill Campground Site (approximate B-3 locaƟon). BoƩom LeŌ: View looking North at Garnet Hill Trailhead showing exisƟng gravel parking area and exisƟng retaining wall structure (approximate B-1 locaƟon). BoƩom Right: View looking southwest at slope stability analysis area where road is to be widened.

2.2 SITE HISTORY

Review of the aerial photographs from Google Earth and historicaerials.com reveal that the project site has been relaƟvely undeveloped other than the dirt roads and trail head parking lots on the sites. Egan Crest Trailhead appears to have been mass graded; however, the grading condiƟons have not changed since the earliest imagery in 1979. The current gravel area and shade structures at Egan Crest Trailhead appears to have been constructed between 1985 and 1999. The Garnet Hill access road (Pole Line Road) appears to have been parƟally developed before 1979, with the final secƟon of road up to Garnet Hill Trailhead being constructed between 1982 and 1999. Based on historical imagery, it is unknown when the picnic areas and vault toilet were constructed.

2.3 GEOLOGIC HISTORY

The project site is located within the eastern area of the Great Basin geomorphic province of Nevada. The Great Basin covers a rough area of 190,000 square miles across Utah, Nevada, Idaho, and Oregon with

Page-5 small porƟons of California1. The area of interest has been heavily impacted by tectonics, volcanics, and weathering from wind and water; this has caused chemical and physical changes throughout the site which can be seen in geologic analysis.

The Great Basin is associated with basin-and- range normal faulƟng which creates the disƟncƟve north-south running mountain ranges with valleys between which surrounds the project area. The basin-and -range allows for surficial expression near the Eagan Crest Trailhead of Permian interbedded Siltstone and Sandstone (Pau). The fine-grained sandstone and sandstone ranges in color from tan to orange/red with a thickness of 1400-1500 feet. In some areas there is quaternary Alluvium which consists of silt, sand, and gravel (Qal) which has deposited from higher in the Eagan Range to near highway 50. The Garnet Hill area experiences the relaƟvely recent volcanism of the area in TerƟary aged RhyoliƟc rock ranging in color from light to dark gray with thin layers of pink. The rhyolite contains smokey quartz, potassium feldspar, plagioclase, bioƟte, and garnet crystals2. Near the Garnet Hill area is exposed upper Mississippian limestone thickly bedded with interbedded chert, this limestone ranges from light olive to brown-gray with a bedding thickness between 2,500-2,700 feet.

2.4 SEISMIC SITE CLASS

The 2018 InternaƟonal Building Code (IBC) also requires that a default Site Class D be assumed for seismic design when soil condiƟons for the top 100 feet are not known in sufficient detail for determinaƟon in accordance with Table 20.3-1 of ASCE Standard 7.

The site is located at approximately the following laƟtude and longitude:

LocaƟon LaƟtude Longitude

Egan Crest 39.31095° -114.99006°

Garnet Hill 39.282942° -114.949621°

Hwy50/Pole Line Rd 39.286628° -114.964112°

A search of the USGS Earthquake Hazards Program’s ASCE 7-16 data, as published by the ASCE 7 Hazard Tool (hƩps://asce7hazardtool.online/), indicated the following spectral acceleraƟon parameters for the locaƟons indicated above and a Site Class D:

Table 2-1: Seismic Design Parameters

Period (s) MCER ground moƟon

(g) Site-modified spectral acceleraƟon value (g)

Numeric seismic design value (g)

Site amplificaƟon factor (g)

0.2 SS 0.371 SMs 0.558 SDS 0.372 Fa 1.503

1.0 S1 0.125 SM1 0.293 SD1 0.195 Fv 2.351

1 Spencer, A.C,. 1917. The Geology and Ore Deposits of Ely, Nevada. United States Geologic Survey.

//efaidnbmnnnibpcajpcglclefindmkaj/hƩps://pubs.usgs.gov/pp/0096/report.pdf 2 Brokaw, A.L., Bauer, H.L., Breitrick, R.A. 1973. Geologic Map of the Rush quadrangle, White Pine County, Nevada.

U.S. Geologic Survey. Map Scale 1:24,000. hƩps://ngmdb.usgs.gov/Prodesc/proddesc_10629.htm.

Page-6

2.5 GEOHAZARDS ASSESSMENTS

2.5.1 Historic Seismicity

Seismological data regarding significant historical earthquakes affecƟng the site was obtained using the USGS Earthquake Catalog (USGS, hƩps://earthquake.usgs.gov/earthquakes/search/). A search radius of 100 kilometers (62 miles) was specified for this analysis.

According to the tabulated data, the most intense earthquake ground shaking within 100 kilometers of the site resulted from a MR (Richter Scale Magnitude) 3.2 earthquake on May 17, 1991, with an epicenter located approximately 49.83 kilometers (31 miles) East of the Garnet Hill site and 57.94 kilometers (36 miles) Southeast of the Eagen Crest site.

The closest earthquake to the site is indicated to be an MR 2.5 earthquake that occurred on February 16, 2013, with an epicenter located approximately 4.83 kilometers (3 miles) East of the Garnet Hill site and

12.87 kilometers (8 miles) Southeast of the Eagen Crest site.

2.5.2 Seismic Hazards

No acƟve or potenƟally acƟve faults are known to underlie the site based on the published geologic maps or aerial photographs that we reviewed. The site is not located within an Alquist-Priolo Earthquake Fault Rupture Hazard Zone, and we observed no surface evidence of faulƟng during our site reconnaissance.

Therefore, it is our opinion that ground rupture at the site resulƟng from seismic acƟvity is unlikely. The site is not located within a seismic hazard zone pursuant to the Seismic Hazard Zone Mapping Act.

2.5.3 Landslides

The topography across the project area varies depending on site. Egan Crest Trailhead and Garnet Hill Sign (Hwy 50) development appears to be on relaƟvely level ground, posing no landslide risk. The Lower Campground slopes very gently to the northeast, with very low landslide potenƟal. Upper Campground has considerable slopes given the area has considerable elevaƟon gain Garnet Hill Trailhead is only 100-feet shy of the nearest peak, therefore development in this area has considerable potenƟal for high amounts of cut and fill. AddiƟonally, the parking area has an approximately 15% slope toward the northeast, where the current retaining wall sits. Stability of this slope should be considered in retaining wall design. Landslide potenƟal at the Upper Campground and Garnet Hill Trailhead should be further considered if the final design is such that significant cut and fill is required as that may affect the current stability of the area. UES is available to perform global stability analyses in these areas upon request. A specific scope of work and cost proposal will be prepared prior to engaging in these services.

The access road leading to the Garnet Hill Campgrounds and Trailhead is currently too narrow for large recreaƟonal vehicles to access the proposed development; therefore, it is necessary to widen several areas of the exisƟng road. Field exploraƟons and stability analysis of this area was completed as the bedrock and soil slope toes will be removed to accommodate the road widening..

2.5.4 Soil Expansion PotenƟal

Based on the AƩerberg Limits test results, the naƟve clayey sand soils are not capable of exerƟng significant expansion pressures on building foundaƟons, or exterior flatwork.

Page-7

3.0 FIELD EXPLORATION & LABORATORY PROGRAM

3.1 FIELD ACTIVITIES

The scope of our services for this project included a subsurface exploraƟon program at Egan Crest Trailhead, Garnet Hill Sign locaƟon, narrow road modificaƟon area, and Garnet Hill Campgrounds. The subsurface exploraƟon program consisted of drilling nine (9) borings to target depths of approximately 15 to 16 1/2 feet below exisƟng site grades. Early auger refusal was encountered on bedrock at the following borings and depths.

Boring No. Depth to Bedrock (Ō)

B-1 13

B-6 14 ½

Slope-1 3.5

Slope-3 13 ½

The borings were logged during drilling by a geotechnical staff professional. SPT and bulk samples were obtained to aid in material classificaƟon and for laboratory tesƟng. The approximate locaƟons of the borings are shown in Figure 2, Project Site Plan. The locaƟons of the borings were determined in the field by using a tablet GPS. The locaƟons of the borings should be considered accurate only to the degree implied by the method used. Results of the boring are presented in the Appendix.

During drilling, two of the borings, B-05 and B-06, at Egan Crest Trailhead had a yellow sulfide mineral as well as petroleum smell between 7-13 feet. Three borings (B-1, Slope-1, and Slope-3) did not reach the targeted 15 feet depth due to early terminaƟon on bedrock.

3.2 LAB PROGRAM

The soil samples collected in the field as part of our field exploraƟon were transported to our lab.

Laboratory tesƟng was conducted to determine certain physical and chemical properƟes of the soils.

Further discussion of the laboratory tesƟng and the laboratory tesƟng result will be discussed later in this report. The laboratory tesƟng data is also included in the Appendix.

3.3 SUBSURFACE CONDITIONS

Fill was encountered in the upper 2-feet of all exploraƟons. The fill generally consisted of naƟve, compacted rhyoliƟc sand, silt and gravels and very sƟff sandy silt. However, due to previous site development/grading there could be deeper and/or poorer quality fill in other areas of the site beyond our exploraƟons.

The Garnet Hill Trailhead as well as Upper and Lower Campground consist of approximately 2-feet of compacted natural fill material underlain by medium to very dense silty sands and gravel. Bedrock was encountered at 13-feet at the Garnet Hill Trailhead site.

The slope borings along the narrow secƟon of Pole Line Road as well as the Garnet Hill Sign boring (B-04) revealed 2-feet of compacted naƟve fill material underlain by loose to very dense silty sand to varying

Page-8 depths. Refusal was encountered on very dense, cemented gravel at a depth of 3.5-feet at the southwestern most slope boring (Slope-1) and on bedrock at 13.5-feet at the middle slope boring (Slope- 3).

Egan Crest Trailhead consists of 2 to 3-feet of fill underlain by firm to very sƟff silt with gravel and medium dense sand with gravel. As stated previously, this site has yellow mineral inclusions that contain elevated arsenic concentraƟons. There was an apparent petroleum smell between 7-13-feet below ground surface.

Laboratory test results indicate that the on-site clay soils have a low expansion potenƟal. Groundwater was not encountered within the depths explored. The boring logs and laboratory test results presented in the Appendix should be referred to for more detailed informaƟon.

3.4 GROUNDWATER

To supplement the groundwater data, we reviewed available groundwater data published by the Nevada Department of Water Resources (DWR) from a monitoring well (385521114503601) located about 30 miles south of the site. DWR has monitored water levels in the well since May 2020. Ground surface elevaƟon at the well is indicated to be about 7,328 feet which is close to the subject property’s elevaƟon.

The monitoring well data shows staƟc water level of 428 feet below ground surface (bgs) on 09/24/2024.

3.4.1 Groundwater Effect on Development and Seasonal Water

Review of available groundwater data revealed the groundwater elevaƟon at nearby monitoring wells has ranged from 100-430 feet below the exisƟng well ground surface. Groundwater levels at the site should be expected to fluctuate throughout the year based on variaƟons in seasonal precipitaƟon, local pumping, and other factors. Locally perched shallower groundwater may be encountered.

Based on our subsurface exploraƟon, experience at the site, and review of groundwater informaƟon near the site, the permanent groundwater table will not likely be a significant factor in construcƟon for excavaƟons extending less than 50 feet below the ground surface. However, it is possible that perched groundwater may be encountered in excavaƟons if construcƟon begins in the winter and early spring months. If groundwater is encountered, the use of sumps, submersible pumps, deep wells or a well point system could be used as methods to lower the groundwater level. The dewatering method used will depend on the soil condiƟons, depth of the excavaƟon and amount of groundwater present within the excavaƟon. Dewatering, if required, should be the contractor’s responsibility. The dewatering system should be designed and constructed by a dewatering contractor with local experience. We recommend the selected dewatering system lower the groundwater level to at least two feet below the boƩom of the proposed excavaƟons.

During the wet season, infiltraƟng surface runoff water can create saturated surface condiƟons. Earthwork operaƟons aƩempted following the onset of winter rains and prior to prolonged drying periods will be hampered by high soil moisture contents.

Soils beneath exisƟng pavements will likely be at an elevated moisture content regardless of the Ɵme of year and will require drying before compacƟon or use as fill. Such soils, intended for use as engineered fill, will require considerable aeraƟon and/or drying to reach a moisture content that will permit the soils to be properly compacted.

Page-9

3.5 CORROSION

3.5.1 Soil Corrosion PotenƟal

Three soil samples were tested to determine minimum resisƟvity, pH, chloride, and sulfate concentraƟons to help evaluate the potenƟal for corrosive aƩack upon reinforced concrete and buried metal. The results of the corrosivity tests are summarized in the below table. Copies of the corrosion potenƟal test results performed by ChemTech Ford are included in the Appendix.

Table 3-1: Soil Corrosivity TesƟng Results

Analyte Test Method Sample IdenƟficaƟon

B-06@7.5’ B-05 @5’ B-02 @2.5’ Slope-3 @2.5’ pH EPA 9045D NA 9.0 8.8 8.5

Minimum ResisƟvity

SSSA 10-3.3 NA 22.3 ohm-m 22.1 ohm-m 21.6 ohm-m

Chloride EPA 300.0 NA 18.3 mg/kg 35 mg/kg 32 mg/kg

Sulfate EPA 300.0 NA Not Detectable 26 mg/kg 16 mg/kg

Total Solids CTF8000 NA 92.3% 87.0% 96.3%

Arsenic

EPA

6010D/3050B

4.58 mg/kg 3.95 mg/kg Not tested Not tested

Based on test results and Table 19.3.1.1 of ACI 318-14 Sec on 19.3, the on-site soils classify as having an “S0” (Negligible) sulfate exposure. Please refer to Table 19.3.2.1 of ACI 318-14 for the requirements for concrete by exposure class. ConsideraƟon should be given to providing protecƟon to buried metal pipes or the use of nonmetallic pipes where permiƩed by local building codes. Non-corrosive backfill, protecƟve coaƟngs and wrappings, sacrificial anodes, or a combinaƟon of these methods could be considered. UES personnel are not experts regarding corrosion and/or corrosion protecƟon, and we recommend that a “Corrosion Engineer” be consulted for actual recommendaƟons regarding the necessity and/or method of cathodic protecƟon.

The soil at Egan Crest Trailhead have elevated arsenic concentraƟons which adds to human health hazards, and in addiƟon is also a corrosive mineral which could pose higher risk of corrosion.

4.0 ENGINEERING ANALYSIS

4.1 ENVIRONMENTAL AND HUMAN HEALTH HAZARDS

The Egan Crest Trailhead Site has several factors that could pose an environmental or human health hazard.

The arsenic concentraƟon sampled in the soils at Egan Crest is above the ‘Minimal Risk Level (MRL)’ of

0.005 mg As/kg/day as defined by the U.S. Department of Health & Human Services.

There was an apparent petroleum smell from boring B-6 at a depth of 7.5 feet at Egan Crest Trailhead, which may pose an environmental concern. UES is available to invesƟgate this further upon request. A separate cost proposal can be prepared to define the scope of work.

UES recommends that an environmental assessment be completed for the Egan Crest Site if the client assesses that construcƟon or recreaƟonal use could cause elevated arsenic exposure to human occupants.

Page-10

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 GEOTECHNICAL DISCUSSION

Our recommendaƟons are based on the assumpƟon that the soil condiƟons are similar to those disclosed by the exploraƟons. If variaƟons are noted during construcƟon or if changes are made in the site plan, structural loading, foundaƟon type or floor level, we should be noƟfied so we can supplement our recommendaƟons, as applicable.

Based on our field and laboratory test results, it is our opinion that firm, undisturbed naƟve soils will be capable of supporƟng the proposed improvements provided the further recommendaƟons regarding site preparaƟon and soils compacƟon are followed. Our work also indicates that naƟve soils and/or engineered fill, properly placed and compacted in accordance with the recommendaƟons of this report, will be capable of supporƟng the proposed structures and pavements, if applicable.

An important aspect of site development will be the adequate clearing of exisƟng surface and subsurface features associated with the exisƟng structures, the proper backfilling of depressions created by structure removal, and uniform compacƟon of all disturbed soils. During demoliƟon we anƟcipate that the upper one to two feet of near-surface soils will become disturbed. Thorough compacƟon of the upper soils will be crucial to providing uniform support of the planned structures and pavements, if applicable.

5.2 SITE PREPARATION

5.2.1 Site Clearing

Strip and remove exisƟng vegetaƟon, debris, uncontrolled fill, disturbed natural soils, and other deleterious materials from proposed building areas, adjacent walks and slabs, and in areas to be paved. ExcavaƟons should extend at least 5 feet beyond the areas to be improved in plan view.

Uncontrolled fill is defined as any exisƟng fill that was not properly placed, observed and tested.

Exposed surfaces should be free of mounds and depressions which could prevent uniform compacƟon.

If unexpected fills or abandoned structures/improvements are encountered during site clearing, such features should be removed and the excavaƟon thoroughly cleaned and backfilled.

ExcavaƟons should be observed by the geotechnical engineer prior to backfill placement.

DemoliƟon of exisƟng structures/improvements should include removal of any foundaƟon system and uƟliƟes. Any excavaƟons as a result of demoliƟon and removal should be properly filled.

Materials derived from the demoliƟon of exisƟng structures/improvements should be removed from the site, and not be allowed for use in any fills. In some cases, exisƟng pavements, if properly broken up, can be used in required fills. The geotechnical engineer should determine the suitability for use based on condiƟons in the field.

5.2.2 ExcavaƟon

It is anƟcipated that excavaƟon of the on-site natural deposits for the proposed project can be accomplished with convenƟonal earthmoving equipment.

ExcavaƟons penetraƟng bedrock will require special consideraƟon where they are to be performed.

Page-11

Contractors, especially those excavaƟng for uƟliƟes, should saƟsfy themselves as to the hardness of materials and equipment required.

Temporary unsurcharged construcƟon excavaƟons should be sloped or shored. Slopes should not be steeper than 2 horizontal to 1 verƟcal. Slopes may need to be flaƩened depending on condiƟons exposed during construcƟon. Exposed slopes should be kept moist (but not saturated) during construcƟon. If there is not enough space for sloped excavaƟons, shoring should be used.

Traffic and surcharge loads should be kept back at least 10 feet from the top of the excavaƟon.

If excavaƟons, including uƟlity trenches, are extended to a depth of more than 20 feet, OSHA requires that the protecƟve system of such excavaƟons be designed by a professional engineer.

ExcavaƟon, trenching and shoring should be conducted in accordance with the U.S. Department of Labor Occupa onal Safety and Health Administra on’s (OSHA) Excava on and Trenching Standard, Title 29 of the Code of Federal Regula on (CFR), Part 1926.650. The safety of construcƟon personnel is the responsibility of the contractor.

5.3 EARTHWORK

All earthwork should be performed in accordance with the guidelines presented in Chapter 18 of the 2018 IBC, except where specific recommendaƟons are presented in this report. It is recommended that contractors perform their own reconnaissance of the site. If the contractors have any quesƟons regarding site condiƟons, site preparaƟon, or recommendaƟons in this report, they should contact a representaƟve of Universal Engineering Sciences.

5.3.1 Subgrade PreparaƟon

Following site clearing acƟviƟes, areas designated to receive fill, at-grade areas, or those achieved by excavaƟon should be scarified to a depth of at least 12 inches, moisture condiƟoned to at least the opƟmum moisture content and compacted to not less than 90 percent of the maximum dry density as determined by ASTM D1557.

The upper 12 inches of final subgrade for the concrete slabs and exterior flatwork should consist of imported compactable, low-expansive soils. All soils supporƟng interior and exterior slab-on-grade concrete should be uniformly compacted to 90 percent of the ASTM D1557 maximum dry density.

Difficulty in achieving the recommended compacƟon may require drying the near-surface subgrade to a compactable moisture content, removal and replacement, and/or the use of a layer of geogrid reinforcement (Tensar BX1100, Tensar TX140, Mirafi 5XT, or equivalent). RecommendaƟons to achieve the recommended compacƟon can be made during construcƟon and will depend on the condiƟons encountered in the field and other factors, such as project schedule and prevailing weather condiƟons.

CompacƟon of all subgrade soils should be performed using a heavy, self-propelled, compactor capable of achieving the required compacƟon and must be performed in the presence of the Geotechnical Engineer’s representaƟve who will evaluate the performance of subgrade under compacƟve load. Difficulty in achieving subgrade compacƟon may be an indicaƟon of loose, soŌ or unstable soil condiƟons that could require addiƟonal excavaƟon. If these condiƟons exist, addiƟonal subgrade stabilizaƟon recommendaƟons may be required at the Ɵme of construcƟon.

Page-12

5.3.2 Fill Materials

On-site soils meeƟng the following criteria, as determined by visual observaƟon by the 3rd party inspector, may be used in required fills:

Table 5-3.2: Fill Materials

Sieve Size Percent Passing

12-inch 100

6-inch 85-100

¾-inch 40-100

Notes: Material should be free of all debris and organic maƩer.

Material has an expansion potenƟal less than 4.0 percent.

In general, material greater than 12 inches in diameter should not be used in fills within 5 feet below the boƩom of the fooƟng within building pad areas.

Fill containing material greater than 6 inches in diameter should not be used in any uƟlity trenches, behind retaining walls or against foundaƟons or grade beams.

Imported material should be compaƟble with on-site soils in addiƟon to being suitable for its intended use. All imported materials should be approved by the geotechnical firm providing tesƟng during construcƟon prior to imporƟng. In general, imported soils should be granular and non-expansive or have a maximum expansion index of 20, a maximum solubility of 0.5%, a maximum sulfate content of 0.1% and a maximum sodium sulfate content of 0.2%.

Select free draining granular materials should be used as backfill immediately behind retaining walls (6 to 12 inches). As an opƟon, a prefabricated drain may be used and should be installed in accordance with the manufacturer’s recommendaƟons.

Based on chemical test results, some on-site naƟve soils contain sufficient concentraƟons of sodium sulfate to be suscepƟble to chemical expansion. The upper 12 inches of material beneath concrete floor slabs should consist of Type II.

5.3.3 Fill Placement and CompacƟon

AŌer performing required excavaƟons, the exposed soils should be carefully observed to verify removal of all unsuitable deposits. Exposed soils should then be scarified to a depth of 6 inches, watered as necessary, and compacted as recommended.

Fill materials should be placed on a horizontal plane unless otherwise accepted by the geotechnical engineer.

Where the slope raƟo of the original ground is steeper than 5 horizontal to 1 verƟcal, the slope should be benched to create near-level areas for the placement of fill. The maximum allowable height of the bench is 3 feet. Bench excavaƟon should be conƟnued to the top of the exisƟng slope in structural fill areas or the daylight (cut/fill) contact.

All required fill should be placed in loose liŌs. The liŌ thickness will depend on the size of the material present. Based on the size of the material encountered, liŌs will range from 8 to 18 inches in thickness.

Materials should be compacted to the following:

Page-13

Table 5-1: CompacƟon Criteria and TesƟng Frequency

Material Type (locaƟon)

Per Modified Proctor Test (ASTM D1557)

CompacƟon (%) Moisture Content Range of OMC TesƟng Frequency

(min. 3 per liŌ) Minimum Maximum

Fine–grained/lean clays 90 (minimum) 92 (preferred)

0% +2% 1 per 2,500 sf

Granular (including aggregate base)

90 (minimum) 95 (preferred)

-2% +2% 1 per 5,000 sf

Notes: OMC = OpƟmum Moisture Content

1. For compacƟon, fine-grained soils are soils with at least 30 percent passing the No. 200 sieve and/or soils having an expansion index of less than 20.

2. All fill placed deeper than 5 feet below the final grade should be compacted to a minimum of 95 percent at a moisture content of opƟmum or greater.

3. Street/pavement subgrade and retaining wall backfill only need to be compacted to a minimum of 90 percent.

4. Moderately to highly expansive clays (expansion index more than 50), if encountered, should not be used as structural fill.

Soils should not be allowed to dry out such that cracking occurs during or aŌer grading. Sufficient moisture contents should be maintained, to prevent cracking, at least unƟl foundaƟons, floor slabs, flatwork, and pavements are constructed. Any significantly dried or cracked soils could be weƩed unƟl they reach acceptable moisture contents or they could be excavated and replaced with acceptable properly compacted fill.

Structural fill should be observed and tested as necessary to determine compliance with the compacƟon requirements presented in this report. In general, one compacƟon test should be performed for approximately every 500 cubic yards of fill, one for one foot of fill placed, or change in material.

5.3.4 On-site Soil Suitability for Use in Fill ConstrucƟon

The on-site soils encountered in our borings are considered suitable for use in engineered fill construcƟon, provided these materials do not contain rubble, rubbish, significant organic concentraƟons, and are at a workable moisture content appropriate for compacƟon. However, near-surface clays (if encountered) should not be used within the upper 12 inches of the final subgrade within interior and exterior slab-on-grade improvements.

ExisƟng pavements and flatwork (asphalt concrete and/or concrete), if any, within areas to be demolished may be broken up and pulverized for use as fill. Asphalt and Portland cement concrete rubble may be used as fill provided it is processed into fragments less than three inches in largest dimension, is mixed with soil to form a compactable mixture, and is approved by the District.

Clean aggregate base materials recovered during site clearing also may be used in engineered fill construcƟon.

5.3.5 Permanent Slopes

Earthwork acƟviƟes to construct slopes at the site should be done in accordance with the following:

• Cut and/or fill slopes should be constructed no steeper than 2 horizontal to 1 verƟcal.

Page-14

• If any slope exceeds 30 feet in height, the slope design should include mid-height benches to intercept surface drainage and divert flow from the slope face.

• The surfaces of slopes should be compacted (not necessary where caliche/rock is exposed) to the minimum specificaƟons recommended in the Earthwork secƟon of this report unƟl the slopes are stable and there are no loose soils on the slopes. Alternately, fill slopes could be constructed by over-filling and cuƫng back to expose fully compacted soil.

• The ground surface adjacent to the top of the slopes should be graded to drain away from the slopes. Any required erosion control measures should be provided for all slopes as soon as possible aŌer grading.

5.4 FOUNDATIONS

If the grading recommendaƟons presented in the Earthwork secƟon of this report are complied with, the proposed structures and any block walls or retaining walls may be supported by convenƟonal type foundaƟons. Any proposed retaining walls or block walls may be established on convenƟonal fooƟngs.

FoundaƟons should be established on undisturbed natural soils having a consistency of at least medium dense (granular) or very sƟff (fine-grained soils) and/or properly compacted fill or bedrock. If bedrock deposits are encountered at foundaƟon elevaƟons, foundaƟons for the structure should be supported enƟrely on bedrock deposits. FoundaƟons for a porƟon of a structure should not be established partly on bedrock deposits and partly on natural soils and/or properly compacted fill. FoundaƟon design parameters are summarized below.

Soil-moisture changes below foundaƟons and floor slabs is the major factor in damages relaƟng to soils.

SeƩlement of the proposed structures, supported as recommended, should be within acceptable limits as provided above. However, if the soils beneath foundaƟons experience an increase in moisture, seƩlement could occur and cause addiƟonal movement of a structure. Therefore, it is important that the recommendaƟons presented in the Drainage and Moisture ProtecƟon secƟon of this report be adhered to.

Individual foundaƟons should not be established partly on bedrock and partly on natural soils and/or properly compacted fill. In some instances, bedrock will be deeper than the design elevaƟon of the boƩom of the foundaƟons. In such cases, the following three alternaƟves can be considered:

1. The column foundaƟon should be extended to bedrock so that all foundaƟons are supported on bedrock.

2. Rather than extending the column foundaƟon to bedrock, lean concrete or controlled low-strength material (CLSM) may be used between the planned design boƩom of the foundaƟon and the top of the caliche. Lean concrete shall have a minimum design strength of 1,000 psi. CLSM shall have a minimum design strength of 100 to 300 psi. One test should be performed for every 50 cubic yards of CLSM or one test per placement day, whichever is more frequent. The sampling and tesƟng of CLSM should be performed in accordance with ASTM D5971 and ASTM D4832, respecƟvely.

5.4.1 Outdoor Amphitheater and Roadway Signs

The outdoor amphitheater may be supported using convenƟonal type foundaƟons. Parameters for foundaƟons are shown in the table below. These parameters should be used for design of all grade beams bearing on undisturbed soil or placed and compacted as recommended in SecƟon 5.3.3 of this report.

Page-15

Table 5-5.1: FoundaƟon Design Parameters

Description Parameter

Allowable bearing pressure 1,2 2,000 psf (soil), 4,000 psf (bedrock)

Minimum width 3 12 inches

Minimum embedment depth 3, 4 36 inches

Anticipated total settlement Less than 1 inch

Anticipated differential settlement Less than ½ inch

Notes:

1. The bearing value may be increased by 500 psf for each additional 12 inches of embedment up to a maximum of 4,000 psf.

2. A one-third increase may be used for wind or seismic loads.

3. Minimum width and embedment depth are for conventional spread footings or the thickened edge of post-tension slab foundations.

4. Below the lowest adjacent final compacted subgrade (generally pad grade before landscaping; exterior footings) or the top of the finished floor slab (interior footings).

5.4.2 Shade Structures and Concrete Dumpster Pads

The shade structures and concrete dumpster pads at the site may be supported using a monolithic slab-on-grade foundaƟon system. FoundaƟon design parameters for slab-on-grade foundaƟons or the thickened edge of the slabs are shown in the table below. These parameters should be used for design of all grade beams bearing on undisturbed soil or placed and compacted as recommended in SecƟon 5.3.3 of this report.

For foundations constructed on slopes, a minimum horizontal distance of 4 feet, measured from the top of the footing, should be provided between the near face of the footing and the face of the finished slope.

Table 5-5.2: FoundaƟon Design Parameters Shade Structures and Dumpster Pads

Description Parameter

Allowable bearing pressure 1,2 2,000 psf (soil), 4,000 psf (bedrock)

Minimum width 3 12 inches

Minimum embedment depth 3, 4 36 inches

Anticipated total settlement Less than 1 inch

Anticipated differential settlement Less than ½ inch

Notes:

1. The bearing value may be increased by 500 psf for each additional 12 inches of embedment up to a maximum of 4,000 psf.

2. A one-third increase may be used for wind or seismic loads.

3. Minimum width and embedment depth are for conventional spread footings or the thickened edge of post-tension slab foundations.

Page-16

Description Parameter

4. Below the lowest adjacent final compacted subgrade (generally pad grade before landscaping; exterior footings) or the top of the finished floor slab (interior footings).

5.4.3 ADA Vault Toilets

The boƩom of the vault will act as its foundaƟon. We recommend a net allowable bearing pressure of 2,000 pounds per square foot (soil) for the vault bearing on undisturbed naƟve soils, or 4,000 psf (bedrock). We understand the shelter contains a pre-cast concrete floor slab and will be installed over the enƟre vault.

Open cut methods require a significant amount of space and may require temporary shoring. Regardless of the excavaƟon/retenƟon system uƟlized, such systems should be designed by a professional engineer registered in the State of Nevada that is experienced in design of these systems.

5.4.4 Earthen Berm (Egan Crest)

The exposed surface should be relaƟvely flat, uniform, and free of materials greater than 12 inches in any direcƟon. The cleared and grubbed area should be proof-rolled to idenƟfy weak areas within the subgrade.

The primary purpose of proof roll tesƟng is to idenƟfy areas where instability may be exhibited under heavy loads, requiring higher compacƟon effort to ensure the area is stable and meets performance expectaƟons. Proof rolling with a fully loaded 4,000-gallon water truck (or equivalent) is a proven method to idenƟfy weak, unstable soil layers. IdenƟfying and miƟgaƟng unstable subgrades improves constructability by ensuring a smooth and uniform foundaƟon for construcƟon. Furthermore, the early idenƟficaƟon of potenƟally problemaƟc areas reduces the effort required to miƟgate soil-related defects in the final materials and potenƟal future maintenance.

We recommend that the firm conducƟng quality insurance inspecƟons inspect and document the proof rolling equipment and procedures. Proofing rolling should meet the following criteria:

The proof rolling equipment shall make at least two overlapping passes at a speed not exceeding five miles per hour (5 mph).

Proof rolling shall be completed in the longitudinal direcƟon, starƟng from the outside edge and moving in (approximately the width of the proof rolling equipment’s Ɵres) with each subsequent pass.

The recommended proof rolling vehicle shall have a gross weight between 30 and 50 tons and provide a uniform compacƟon effort over the enƟre contact area.

Failure criteria for proof rolling include:

o Permanent ruƫng or pumping exceeding one inch (1”).

o Signs of soil pumping.

Possible miƟgaƟon alternaƟves for soŌ or weak areas exposed during proof-rolling include:

o Removing, replacing, and recompacƟng the area of concern o Add addiƟonal soil such that there is a smooth transiƟon (± 1/2 inch) between the improved area and the remaining subgrade aŌer recompacƟng the area.

Page-17 o Other approved alternaƟve methods provided by the Earthwork Contractor o The contractor should provide in wriƟng a descripƟon of their ways and means to the design team, UES, and the firm providing quality assurance for acceptance.

Regardless of the miƟgaƟon approach selected, all miƟgated areas require verificaƟon through proof rolling and shall be documented by the firm conducƟng quality assurance efforts.

5.5 EXTERIOR FLATWORK CONSTRUCTION (INCLUDING PAVED WALKING TRAILS)

The upper 12 inches of final soil subgrade for exterior concrete flatwork areas should consist of approved, imported, compactable, low-expansive (less than 4% swell) soils compacted in accordance with the Engineered Fill ConstrucƟon recommendaƟons included in this report. Exterior flatwork subgrade soils should be maintained in a moist condiƟon and protected from disturbance.

Proper moisture condiƟoning of the subgrade soils is considered important to the performance of exterior flatwork. Expansion joints should be provided to allow for minor verƟcal movement of the flatwork.

Exterior flatwork should be constructed independent of the perimeter building foundaƟon and isolated column foundaƟons by the placement of a layer of felt material between the flatwork and the foundaƟon.

Exterior flatwork concrete should be at least four inches thick in pedestrian traffic areas and underlain by at least four inches of aggregate base compacted to at least 95 percent of the ASTM D1557 maximum dry density. The four inches of aggregate base is not required if the low-expansion imported fill below the flatwork consists of aggregate base.

ConsideraƟon should be given to thickening the edges of the slabs at least twice the slab thickness where wheel traffic is expected over the slabs. Expansion joints should be provided to allow for minor verƟcal movement of the flatwork. Exterior flatwork should be constructed independent of other structural elements by the placement of a layer of felt material between the flatwork and the structural element.

The slab designer should determine the final thickness, strength and joint spacing of exterior slab-on-grade concrete. The slab designer should also determine if slab reinforcement for crack control is required and determine final slab reinforcing requirements.

Our recommendaƟons are intended to reduce the effects of variable soil subgrade condiƟons in exterior concrete flatwork areas. However, some seasonal movement of exterior flatwork should be anƟcipated where flatwork is adjacent to landscape areas.

Areas adjacent to new exterior flatwork should be landscaped to maintain more uniform soil moisture condiƟons adjacent to and beneath flatwork. We recommend final landscaping plans not allow fallow ground adjacent to exterior concrete flatwork.

5.6 DRAINAGE AND MOISTURE PROTECTION

FoundaƟon soils should generally not be allowed to become saturated during or aŌer construcƟon, except when necessary to increase moisture contents prior to construcƟon. InfiltraƟon of water into foundaƟon or uƟlity excavaƟons should be prevented during construcƟon. UƟlity lines should be properly installed and the backfill properly compacted to avoid possible sources for subsurface saturaƟon.

PosiƟve drainage away from the structures should be provided during construcƟon and maintained throughout the life of the structure. Any downspouts, roof drains or scuppers should discharge into splash blocks or extensions and away from the structures. Backfill against fooƟngs, exterior walls, and in uƟlity

Page-18 trenches should be properly compacted and free of all construcƟon debris to reduce the possibility of moisture infiltraƟon.

If the above recommendaƟons are not followed there would be an increased risk/potenƟal for increasing moisture below foundaƟons and slabs, resulƟng in addiƟonal movement and distress to structures and slabs.

5.7 LATERAL EARTH PRESSURES AND RETAINING WALLS…