FIO_-_Fillstand_Addition_Geotech_Report_Site_1.pdf

GEOTECHNICAL EVALUATION

PROPOSED TRUCK FILLSTAND F-35

NELLIS AIR FORCE BASE

CLARK COUNTY, NEVADA

Project No. 20143373E2

May 5, 2017

Prepared for:

Robert and Company

2233 Park Avenue, Suite 205 Orange Park, Florida 32073

Prepared by:

Geotechnical & Environmental Services, Inc.

7150 Placid Street Las Vegas, Nevada 89119

GEOTECHNICAL &

ENVIRONMENTAL

SERVICES, INC.

We make the ground work for you. . . ®

PROVIDING

• Geotechnical

Engineering

• Construction Materials Testing & Inspections

• Environmental Services

• Ground Source Heat Exchange

• Thermal Conductivity Testing

• IAS Accredited

• AASHTO

Accredited Testing Laboratory

May 5, 2017 Project No. 20143373E2

Mr. James A. Morgan, PE Robert and Company 2233 Park Avenue, Suite 205 Orange Park, Florida 32073

RE: Geotechnical Evaluation, Proposed Truck Fil/stand F-35 Program Addition, Nellis Air Force Base, Clark County, Nevada

Dear Mr. Morgan:

Geotechnical & Environmental Services, Inc. (GES) is pleased to present to Robert and Company the Geotechnical Evaluation report for the Proposed Truck Fill Stand F-35 Program Fueling Facility addition to be constructed at Nellis Air Force Base in Clark County, Nevada.

The Geotechnical Evaluation report includes the findings of the geologic review, the results of the field exploration and laboratory testing programs, conclusions, and recommendations for site development.

We appreciate this opportunity to provide our professional services. If you have any questions or comments regarding this information, please feel free to contact our office.

Sincerely, Geotechnical & Environmental Services, Inc.

Melissa N. Salva ~ Staff Professional

MNS:DJS:caw

David J. Salter, P.E.

Geotechnical Practice Leader

Dist: 5 originals mailed to addressee PDF emailed to addressee atj .morgan@robertco.com Copy to Project File

Las Vegas • 7150 Placid Street Las Vegas, Nevada 89119 • (702) 365-1001 • Fax (702) 341-7120

Field Office - Mesquite • (702) 346-4489 • Fax (702) 346-0525 www.gesnevada.com

TABLE OF CONTENTS

INTRODUCTION

1.1. PURPOSE AND SCOPE

1.2. PROJECT DESCRIPTION

1.3. SITE DESCRIPTION

DISCUSSION

2.1. GEOLOGY

2.2. SEISMICITY

2.3. LIQUEFACTION

2.4. MAPPED SUBSURFACE CONDITIONS

2.5. FIELD EXPLORATION

2.5.1. RESISTIVITY SURVEYS

2.5.2. REFRACTION MICROTREMOR (ReMi) SURVEY

2.5.3. EXPLORATORY BORINGS

2.6. ENCOUNTERED SUBSURFACE MATERIALS AND CONDITIONS

2.6.1. FILL

2.6.2. NATIVE SOIL

2.6.3. GROUNDWATER

2.7. LABORATORY TESTING

CONCLUSIONS

RECOMMENDATIONS

4.1. EARTHWORK

4.1.1. SITE GRADING

4.1.2. STRUCTURAL FILL AND BACKFILL SUITABILITY

4.1.3. FILL PLACEMENT

4.1.4. OBSERVATION AND TESTING

4.2. EXCAVATION CONSIDERATIONS

4.2.1. TEMPORARY EXCAVATIONS

4.2.2. CEMENTED SOIL

4.3. MATERIAL VOLUME CHANGES

4.4. UNDERGROUND UTILITIES

4.5. FOUNDATIONS

4.5.1. SPREAD FOOTINGS

4.6. SEISMIC SITE CLASS

4.7. LATERAL EARTH PRESSURES

4.8. PIPELINE DESIGN

4.8.1. MODULUS OF SOIL REACTION (E')

4.8.2. VERTICAL LOADS AND FOUNDATIONS

4.9. EXTERIOR CONCRETE FLATWORK

4.10. RECOMMENDED NON-DEDICATED PAVEMENT SECTIONS

4.11. CONCRETE AND CORROSIVITY

4.12. DRAINAGE AND MOISTURE PROTECTION

LIMITATIONS

REFERENCES

TABLES

Table 2.5.1. Field Resistivity Test Results Table 2.5.2. Exploratory Borings Table 4.6 Spectral Response Accelerations and Site Coefficients Table 4.8.1. Estimates of Composite Subgrade Modulus, E' Table 4.10.-1 Recommended Asphalt Concrete Pavement Sections Table 4.10.-2 Recommended Portland Cement Concrete Pavement Sections

APPENDIX A – SUBSURFACE STUDY

APPENDIX B – LABORATORY TEST RESULTS

APPENDIX C – DESIGN FIGURES

APPENDIX D – SITE SEISMIC SURVEY RESULTS

May 5, 2017

GEOTECHNICAL EVALUATION

PROPOSED TRUCK FILLSTAND F-35

INTRODUCTION

This report presents the results of a geotechnical evaluation performed by Geotechnical &

Environmental Services, Inc. (GES) for Robert and Company for the Proposed Truck Fill Stand F-35

Program Fueling Facility addition to be constructed at Nellis Air Force Base (AFB) in Clark County, Nevada. Figure A-1 presents a vicinity map showing the approximate location of the site within the

Las Vegas Valley. The following sections present the purpose and scope of our geotechnical evaluation, project description and site description. Our services for this project were performed in general accordance with our proposal dated August 10, 2016.

1.1. PURPOSE AND SCOPE

The purpose of this geotechnical evaluation was to provide general subsurface information and recommendations to aid in the design and construction of the Proposed Truck Fill Stand F-35

Program Fueling Facility addition project. The scope of this study included a review of referenced geologic literature and maps, a subsurface exploration, soil sampling, laboratory testing of selected soil samples, engineering evaluations, and preparation of this report.

1.2. PROJECT DESCRIPTION

Our understanding of the project is based upon our conversation with Robert and Company personnel, the conceptual site plan provided, and our local experience with similar projects at Nellis

AFB.

The proposed project includes the design and construction of a truck fill stand fueling facility to support aircraft revetment and bomber positions. We understand that the project is being constructed through the US Army Corps of Engineers. Based on review of the provided conceptual site plan, we understand that the new facility will include two new revetments and asphalt paved access ways to the planned truck fill stand location. The paved access areas will include approximately 1,200 feet of new pavement that varies from approximately 20 to 80 feet in width. The vehicle access roads will be constructed with asphalt concrete. We anticipate downward axial column loads up to approximately 1.8 kips and wall loads of up to 2 kips per lineal

May 5, 2017 foot. We anticipate that the finish grade elevations will be generally within 2 feet of the existing site grade.

1.3. SITE DESCRIPTION

The project site is located within Nellis AFB, Nevada, within APN 140-10-101-001, northeast of the existing revetment positions and ½-mile due north of existing Kinder Morgan fuel tanks

A dirt road, oriented northeast-southwest was observed near the western portion of the site. Other various infrastructure associated with the Air Force base was observed near and within the project site. Several drainage features transect the site in east-west directions. At the time of our exploration the majority of the site was vacant, undeveloped. Scattered desert vegetation, including small shrubs, was observed throughout the site. Severe desiccation cracking was observed throughout the site with cracks up to approximately 18-inches deep predominantly in the southern portion of the project site. Some of these deeper cracks appeared to be associated with desiccation of near-surface soils; however, deepening and widening of some of the cracks appeared to be associated with additional erosion from precipitation and associated particle migration, or possibly in part from burrowing animals. Some cracks extended up to 18 inches, or more, below the ground surface and appeared intermittently, sometimes along relatively linear alignments.

DISCUSSION

The following sections describe geology, seismicity, mapped subsurface conditions, field explorations, encountered subsurface materials and conditions, and laboratory testing.

2.1. GEOLOGY

The subject site is located in the northeast portion of the Las Vegas Valley, a fault-bounded graben structure surrounded by mountain ranges. The Las Vegas Valley is physiographically characteristic of the Basin and Range Province with generally northwest-trending parallel mountain ranges and an intervening basin. Unlike many basins within the Basin and Range

Province which are internally draining, the Las Vegas Valley is unique in that the basin drains through the Las Vegas Wash to Lake Mead and the Colorado River.

Tertiary and Quaternary unconsolidated alluvial deposits, derived from the surrounding mountain ranges, fill the valley. These deposits may be up to 4,000 feet thick near the center of the valley.

May 5, 2017

The surrounding mountain ranges are comprised of sedimentary and igneous rocks. Alluvial fan deposits, consisting of sand and gravel, slope down from the mountain fronts towards the valley floor. Sediments are typically less coarse, grading from fine sand and silt to clay near the valley bottom. Beds of amorphous and crystalline gypsum are common. Zones of calcareous cemented deposits (caliche) are present at various locations and depths throughout the valley.

2.2. SEISMICITY

The U.S. National Oceanic and Atmospheric Administration Earthquake Catalog lists about 800 events of magnitude greater than or equal to 4 with epicenters within about 120 miles of Las Vegas.

Only 19 events greater than or equal to magnitude 4 are estimated to have occurred during the 1881 through 1938 period in the southern Nevada region.

After about 1947, nuclear testing began at the Nevada Test Site. Therefore, many of the recorded earthquakes after about 1947 may be due to nuclear blasts occurring more than about 60 miles from the subject site. Several hundred earthquakes occurred from 1936 to 1965 near Hoover Dam, presumably due to filling of the Lake Mead reservoir, with 24 of these events reportedly greater than or equal to magnitude 4.

Based on a review of referenced geologic maps and literature, the nearest mapped Quaternary-age

(last 1.6 million years) tectonic fault is approximately ½ mile southwest of the site. Other Quaternary-age sites are the Eglington fault, which geologists have debated may also be potentially active, and

Frenchman Mountain fault, which are located approximately 7-1/2 miles northwest , and 1-¾ miles southeast of the site, respectively. The nearest mapped Holocene active fault (i.e., a fault that has moved within the last 10,000 years) is the Black Hills fault, located approximately 19 miles south of the site (USGS). The nearest mapped fissure zone is located approximately 5-1/2 miles west of the site near Alexander Road and North 5th Street (DePolo, 2000). Based on the results of our review of available literature, it is our opinion that the potential for fault-related surface rupture at the site is negligible.

2.3. LIQUEFACTION

Liquefaction is a phenomenon in which loose, saturated soils lose shear strength under short-term

(dynamic) loading conditions. Ground shaking of sufficient duration results in the loss of

May 5, 2017 grain-to-grain contact in potentially liquefiable soils due to a rapid increase in pore water pressure, causing the soil to behave as a fluid for a short period of time.

To be potentially liquefiable, a soil is typically cohesionless with a grain-size distribution generally consisting of sand and silt. It is generally loose to medium dense and has a relatively high moisture content, which is typical near or below groundwater level. The potential for liquefaction decreases with increasing clay and gravel content, but increases as the ground acceleration and duration of shaking increase. Potentially liquefiable soils need to be subjected to sufficient magnitude and duration of ground shaking for liquefaction to occur. An in-depth evaluation of the potential for liquefaction at the site was outside the scope of this geotechnical evaluation.

Effects of liquefaction include relatively large total and differential settlements, flotation of subsurface structures, slope failures, lateral ground displacements (lateral spreading), surface subsidence, ground cracking, and sand boils.

2.4. MAPPED SUBSURFACE CONDITIONS

Based on review of the Clark County Soil Guidelines Map (CCBD, 1998), the project site is located near a previously mapped Special Geotechnical Consideration Area containing potential drainage areas or recent sediment deposits, and may also have solubility, clay swell, corrosion, gypsum salt, expansive or hydro-collapsible potential. Based on review of the Clark County Expansive Soil

Guidelines Map (CCDDS, 2006), the project site is located in a Special Geotechnical Consideration

Area having low to moderate swell potential (up to 8 percent).

The subject site is located on the referenced Geologic Map of the Las Vegas Northeast Quadrangle

(Matti et al., 1993) within a geologic unit of intermittently active alluvium (Qai) mapped as slightly to moderately consolidated, pink to pale-brown sand and pebble to cobble conglomerate mainly on between-channel alluvial flats and less commonly in incised washes.

2.5. FIELD EXPLORATION

GES evaluated the subsurface conditions in proposed improvement areas by performing soil resistivity surveys, performing a refraction microtremor (ReMi) survey, and drilling exploratory borings.

May 5, 2017

2.5.1. RESISTIVITY SURVEYS

On October 19, 2016, resistivity surveys were performed at the project site. Resistivity tests were performed at the planned truck fill stand at the project site to aid in assessing the corrosion potential of the on-site soils to metal. The tests were performed with a Ground Tester Model 6470 soil resistance meter by AEMC Instruments using the Wenner array in general accordance with

ASTM G 57. Electrode spacing of 5, 10, 20, 30, 40 and 60 feet were used for the tests to measure the apparent resistivity to an approximate depth of 60 feet below existing grade. A second resistivity array was run approximately perpendicular to the first. The locations of the resistivity tests are provided on the Exploration Locations Map in Appendix A, and the results are presented in the table below along with corresponding corrositivity ratings.

Table 2.5.1. Field Resistivity Test Results

Resistivity Test No.

Electrode Spacing (ft)

Apparent Resistivity (Ohm-cm)

Corrosivity Rating

R-1 (North to South)

37490

Essentially Non- Corrosive

40 5120 Moderately Corrosive

63093

Essentially Non- Corrosive

22829

Essentially Non- Corrosive

10 12649 Mildly Corrosive

5 1524 Highly Corrosive

R-1 (West to East)

60 3901 Corrosive

1676400

Essentially Non- Corrosive

60960

Essentially Non- Corrosive

20 5120 Moderately Corrosive

40843

Essentially Non- Corrosive

24932

Essentially Non- Corrosive

2.5.2. REFRACTION MICROTREMOR (ReMi) SURVEY

Relatively deep subsurface information was obtained at the project site on October 18, 2016, by performing a refraction microtremor (ReMi) survey. The ReMi survey is a non-destructive, geophysical, surface based test utilized to characterize the shear-wave velocity profile of the subsurface materials to a depth of approximately 100 feet or more. The test uses passive energy wave sources of vibrations from traffic, construction, airplanes, etc. The results of the ReMi survey

May 5, 2017 are included in Appendix D. The locations of the explorations, resistivity surveys and ReMi survey array were recorded by GES staff using a hand-held GPS unit at the time the explorations were performed. The approximate location of the ReMi array is shown on the Figure A-2, Exploration

Location Map in Appendix A.

2.5.3. EXPLORATORY BORINGS

Five exploratory borings (B-1 through B-5) were drilled to depths of between approximately 10 and

15 feet below the existing ground surface on November 15, 2016. The total footage drilled was approximately 65 lineal feet. The approximate locations and depths of the borings are described in the table below.

Table 2.5.2. Exploratory Borings

Structure Number of

Borings Depth of Borings

(feet) Total Footage

(feet)

Revetments (2) 2 15 30

Truck Fillstand 1 15 15

Roads 2 10 20

Total 65

GES staff directed and supervised the subsurface explorations, while maintaining detailed logs of the subsurface conditions, classifying the soils encountered, and obtaining soil samples. The soils encountered were classified in genersal accordance with the Unified Soil Classification System

(USCS). A Key to Symbols and Terms utilized on the exploration logs is presented on Figure A-3.

The exploration logs are presented in Appendix A.

The explorations were drilled with track-mounted Diedrich D-50 drill rigs using 8-inch nominal outside diameter hollow stem augers. Ring-lined soil samples and penetration blow counts were obtained with a 3-inch outside diameter ring-lined drive sampler in general accordance with ASTM D 3550.

The sampler was driven with a 140-pound automatic trip hammer falling about 30 inches. The penetration resistance (blow counts) measured by driving the sampler was used to evaluate the density and consistency of the in-place soil. Bulk samples were also obtained at selected subsurface intervals. The explorations were backfilled with soil cuttings.

Approximate exploration locations are presented on Figure A-2. The exploration locations were recorded by GES staff using a hand held GPS unit at the time the explorations were performed.

May 5, 2017

Ground surface elevations at the boring locations were estimated based on Google Earth data and are provided on the boring logs in Appendix A.

2.6. ENCOUNTERED SUBSURFACE MATERIALS AND CONDITIONS

The following sections describe the fill and native soil encountered in the explorations. Detailed information regarding subsurface materials and conditions are presented on the boring logs in

Appendix A.

2.6.1. FILL

Fill was penetrated in exploratory borings, B-1 and B-2, to depths of approximately 1 and 10 feet below ground surface. The encountered fill was composed primarily of dry, medium dense to dense sand and gravel with varying amounts of clay. Documentation of fill placement and compaction in the area was not available. Without documentation to indicate that the fill soils were placed under the supervision of a geotechnical engineer, the existing fill soils at the site are considered uncontrolled. The term uncontrolled fill soils refers to artificial fill which was placed without engineering observation, testing, or documentation and is considered unsuitable in its present condition for the support of the proposed improvements.

2.6.2. NATIVE SOIL

The native subsurface soils encountered in the borings were generally observed as layers of dry, stiff to very stiff lean clay. Some medium dense to dense, clayey sand, very stiff dry silt were also encountered in the borings. Weakly cemented soil was encountered in our explorations.

2.6.3. GROUNDWATER

Groundwater was not encountered within any of the borings during our field exploration. A review of water wells listed on the State of Nevada Department of Conservation & Natural Resources, Division of Water Resources website indicates that historical groundwater levels measured in wells in the same township, range, and section as the project site (S20-E62-10) are deeper than approximately 42 feet below the ground surface. Groundwater levels should be anticipated to fluctuate due to seasonal precipitation, groundwater withdrawal and recharge, irrigation practices, and potential future dewatering efforts within and/or near the subject site. A detailed evaluation of possible groundwater fluctuations was beyond the scope of this study.

May 5, 2017

2.7. LABORATORY TESTING

The laboratory testing program included tests to classify and to evaluate engineering and physical properties of the on-site soils. The tests were performed on samples obtained from the on-site native soils.

The test results are presented in Appendix A on the exploration logs and on test reports presented in Appendix B. Detailed descriptions of the laboratory tests performed are also presented in

Appendix B.

CONCLUSIONS

Based on the results of our field exploration and laboratory testing programs, it is our opinion that there are no known geologic or geotechnical conditions that would prevent development of the site.

It is also our opinion that there are some geotechnical considerations that will affect site development including the presence of fill soils and chemical corrosivitiy of native soils, as described below.

• Based on the results of our resistivity testing at the project site in the area of the truck fill stand construction, the project soils should be considered highly corrosive to metal.

• Fill soils up to approximately 10 feet in thickness were encountered in two explorations performed at the site. Fill soils should be considered uncontrolled fill unless documentation of their placement and compaction is provided. The term uncontrolled fill refers to man-made fill which was placed without engineering observation, testing, or documentation and is considered unsuitable in its present condition to support structures or other improvements.

• The tested soils have a high expansive potential as tested and defined according to subsection 1803.5.3.2 and Table 1808.6.1.1, respectively, of the SNA to the 2012 IBC

(SNBO, 2013).

• Based on our understanding of the project and the results of our laboratory tests performed on samples of native soils, it is our opinion that soil materials at the site classify as Category 4b soils based on Table 1705.6 of the SNA to the 2012 IBC (SNBO, 2010), which indicates full time observations during construction activities will be needed.

• Based on the cohesive nature and consistency of the soils encountered and depth to groundwater, it is our opinion that the potential for liquefaction at the site is very low.

• Based on the laboratory test results, the tested on-site native soils have a low solubility.

Table 1804.3.1 of the SNA to the 2012 IBC (SNBO, 2010) defines soils as with less than 2.00 percent by dry weight soluble solids as determined by American Water Works Association (AWWA) standard test method 2540 C as having a low solubility.

• The tested on-site soils have a severe concrete sulfate exposure, and a moderate chemical-induced heave potential as determined by AWWA Standard Test Methods 3500-Na D and 4500 E.

• Based on the results of our ReMi survey, a Seismic Site Class D may be used for design.

RECOMMENDATIONS

The following sections present recommendations concerning the proposed improvements at the subject site. These recommendations are based upon our understanding of the project, the engineering properties of the tested soils, the geologic conditions that are presented in this report, and the assumption that an adequate number of tests and observations will be made during construction to evaluate compliance with these recommendations.

4.1. EARTHWORK

Based on the results of our field exploration and laboratory testing programs, and our stated understanding of the proposed project, it is our opinion that the following earthwork recommendations for the proposed improvements are applicable to the project.

4.1.1. SITE GRADING

Any existing uncontrolled fill, deleterious material, and loose, cracked, or disturbed native soils, should be excavated from within the improvement areas to expose suitable native soils, and either removed from the site or processed for use as structural fill meeting the recommendations outlined in this report. Based on the dry surficial soils and the expansion potential of site soils overexcavation of surficial soil in areas to receive new construction should be performed; overexcavation to a depth of 36 inches or more should be performed below the bottom of foundations of structures sensitive to movement including the proposed roadway. In fill areas with 30-inches or more vertical feet of fill, at least the upper 24-inches of native soil should be overexcavated prior to placing structural fill.

Overexcavations should extend laterally a distance equal to the depth of the overexcavation, or at least 5 feet beyond the edge of footings/concrete slabs/tanks and at least 2 feet beyond the edge of pavements, whichever is greater. The lateral extent of ovexcavations may be terminated if space limitations prevent the recommended overexcavation, at the discretion of the geotechnical consultant.

After the removal of existing unsuitable soils described above, the bottom of the overexcavation should consist of stiff to very stiff native soils. The depth of the overexcavation may need to be increased until surface cracks and porous materials (i.e. soil that may exhibit potential for hydro-collapse) are fully excavated and suitable soils are encountered.

May 5, 2017

After the recommended excavations are performed, the stiff to very stiff native soils should be scarified to a depth of at least 6 inches, moisture conditioned to within approximately 2 percent of optimum moisture content, and compacted to at least 90 percent of the maximum dry density, as determined by ASTM D 1557. Scarification may terminate on strongly cemented soil, as evaluated by the geotechnical consultant; additional cemented soil considerations are provided in Section 4.2.2 of this report.

4.1.2. STRUCTURAL FILL AND BACKFILL SUITABILITY

Samples of materials proposed for use as imported structural fill should be submitted to the geotechnical consultant for testing and evaluation prior to being transported to the site. Imported materials and on-site materials that have been excavated, stockpiled, and processed for use as structural fill should satisfy the following recommendations.

• Imported fill materials and excavated on-site material should be similar to the on-site soils and have 10 to 80 percent of material passing the No. 200 sieve and 100 percent passing the 4-inch sieve.

• Imported fill materials and excavated on-site material should have a liquid limit of less than 35 and plasticity index of less than 20.

• Imported fill materials and excavated on-site material should have a remolded swell potential of less than 4 percent as determined per the procedure outlined in Section 1803.5.3.2 of the SNA to the 2009 IBC (SNBO, 2010).

• Imported fill materials and excavated on-site material should contain less than 1.00 percent by dry weight soluble solids as determined by AWWA standard test method 2540 C.

• Imported fill materials and excavated on-site material should contain less than 0.2 percent by dry weight soluble sulfate as determined by AWWA standard test method 4500 E.

• Imported fill materials and excavated on-site material should be free of debris, organic materials, and other deleterious materials.

• Imported fill materials and excavated on-site material used as retaining wall backfill should have 10 percent, or less, of material passing the No. 200 sieve and 100 percent passing the 4-inch sieve.

4.1.3. FILL PLACEMENT

Structural fill should be uniformly moisture conditioned to within approximately 2 percent of optimum moisture content, placed in horizontal lifts, and compacted to at least 90 percent of the maximum dry density as determined by ASTM D 1557. Fill placed deeper than 5 feet below finished grade should be compacted to 95 percent of maximum dry density as determined by ASTM D 1557. The optimal

May 5, 2017 lift thickness of fill will depend on the type of soil and compaction equipment used, but should generally not exceed approximately 8 inches in loose thickness.

If fill material is placed where the existing ground surface is steeper than 5:1 (horizontal to vertical), the surface on which fill is to be placed should be benched. We recommend that benches be 8 feet or more wide, or be of sufficient width to permit operation by compaction equipment. Benches should include approximately 2-foot high vertical or near-vertical intervening steps, cut to expose stiff to very stiff soil as evaluated in the field by the geotechnical consultant during earthwork operations.

Preparation of the benching surface in areas to receive fill should include scarification and moisture-conditioning to a depth of approximately 8 inches, and compaction to a relatively non-yielding condition, prior to placement of fill.

4.1.4. OBSERVATION AND TESTING

A qualified geotechnical consultant should perform appropriate observation and testing services during grading and construction operations. These services should include observation of removal of soft, loose, cracked, or otherwise unsuitable soils, evaluation of subgrade conditions where soil removals are performed, and performance of observation and testing services during placement and compaction of structural fill and backfill soils. In-place density and moisture tests should be performed in accordance with ASTM D 6938 or, alternatively, in accordance with ASTM D 1556. The test frequency should be at least one test per 500 cubic yards of fill material placed or at least 2 tests per lift of fill material placed, whichever is more. Additional field tests may also be performed in structural and non-structural areas at the discretion of the geotechnical consultant.

The geotechnical consultant should perform observation and testing services during placement of concrete, mortar, grout, asphalt concrete, and steel reinforcement, as needed. Observation and testing of soils should be performed as indicated in Table 1705.6 of the referenced SNA to the 2012

IBC (SNBO, 2014). Based on the results of our laboratory testing and our understanding of the subject project, it is our opinion that the level of special inspection, as indicated in Table 1705.6, should be 4b.

May 5, 2017

4.2. EXCAVATION CONSIDERATIONS

The following sections provide recommendations to aid in the successful performance of excavations at the project site and include recommendations regarding temporary excavations and cemented soil.

4.2.1. TEMPORARY EXCAVATIONS

Temporary slope surfaces should be kept moist to retard raveling and sloughing. Water should not be allowed to flow over the top of excavations in an uncontrolled manner. Stockpiled material and/or equipment should be kept back from the top of excavations a distance equivalent to the depth of the excavation or more. Workers should be protected from falling debris, sloughing and raveling in accordance with Occupational Safety and Health Administration regulations. Temporary excavations are time sensitive and failures are possible.

Excavations greater than 4 feet in depth into uncemented soils are not anticipated to stand vertically.

Excavations greater than 4 feet in depth should be sloped back in accordance with the maximum allowable slope ratios presented in Appendix B to Subpart P of Occupational Safety and Health

Standards for the Construction Industry (OSHA) 29 CFR, State of Nevada, Division of Occupational

Safety and Health, Part 1926. The soil type definitions in Appendix A to Subpart P of OSHA 29 CFR, Part 1926 should be applied to soils encountered in excavations to determine the maximum allowable slope ratio. As an alternative to sloped excavation sidewalls, excavations could be shored and braced. Shoring and bracing should be designed in accordance with Appendices C and D to

Subpart P of OSHA 29 CFR, Part 1926. Safety of construction personnel is the responsibility of the contractor.

4.2.2. CEMENTED SOIL

Weakly and moderately cemented soil refers to cemented soil that will crumble or break with little or considerable finger pressure, respectively. Strongly cemented soil refers to rock-like soil that will not crumble or break at any finger pressure. In general, very dense or slightly hard cemented soils can be excavated with a backhoe and moderately hard cemented soils can be excavated easily with a ripper tooth or by a backhoe with extreme difficulty. In general, to excavate moderately hard to hard, hard, and very hard rock-like materials a heavy duty excavator or trencher, Caterpillar D-10 Dozer (or equivalent) or larger, ripper, hoe-ram, headache ball, rock-

May 5, 2017 saw or similar rock excavation techniques may be needed. Where thick layers of very hard cemented materials are to be excavated, blasting is sometimes needed for removal.

Although not encountered in our explorations, strongly cemented soils may be encountered beyond or between our boring locations. The following additional recommendations are provided in the event that strongly cemented soil is encountered during construction. A detailed excavatability or rippability evaluation was beyond the scope of this study. The contractor should perform the independent investigations necessary to determine the type of equipment required to perform the work. If the contractor(s) have any questions regarding site conditions, site preparation, or the recommendations provided, they should contact a representative of GES for any needed clarifications prior to submitting earthwork bids.

Due to the potential for differential settlement, structure footings (including ring, retaining wall, and screen wall footings) should not bear on both strongly cemented and non-cemented or weakly cemented soils. If both cemented and non-cemented/weakly-cemented soils are present at the footing base, as evaluated by the geotechnical consultant, the cemented soil should be overexcavated approximately 12 inches and replaced with structural fill, or the uncemented soil should be overexcavated down to strongly cemented soil and the excavated material replaced with lean concrete.

Overexcavation and/or scarification efforts may be terminated at depths where medium hard to very hard, strongly cemented material is encountered, as evaluated in the field by the geotechnical consultant.

Rock excavation techniques such as use of heavy-duty ripping equipment, heavy-duty backhoe, headache ball, hoe-ram, and/or rock saw should be anticipated to remove strongly cemented materials. The contractor should be aware of the potential for (and take adequate precautions to reduce the potential for) vibrational damage to adjacent or nearby structures, and take appropriate precautions, when using heavy impact equipment during removal of strongly cemented materials.

Pre-construction documentation of existing distress to structures near construction areas, and monitoring of these structures and ground motions generated, should be considered to reduce the potential for damage and construction-related claims.

May 5, 2017

Oversize material is anticipated to be generated during excavation of strongly cemented material.

These materials will need to be crushed prior to being used as structural fill and backfill, or removed from the site and disposed of in a suitable manner. Bulking of this material should be anticipated when it is excavated, processed/crushed, and compacted. For planning purposes, up to approximately 10 percent bulking, or more, should be anticipated.

4.3. MATERIAL VOLUME CHANGES

Based on our experience, it is our opinion that there will be a reduction in volume when the on-site uncemented soils are excavated and compacted. Shrinkage of the on-site uncemented soils is estimated to be in the range of 5 to 15 percent when compacted to at least 90 percent of the maximum dry density (ASTM D 1557). Accordingly, with shrinkage of 5 to 15 percent, one cubic yard of excavated native soils compacted to 90 percent relative compaction would generate approximately 0.95 to 0.85 cubic yards of structural fill.

4.4. UNDERGROUND UTILITIES

Excavated, on-site soils may be used for utility trench backfill provided they meet the recommendations for imported structural fill outlined in this report. Soils used for trench backfill should be should be moisture conditioned to approximately optimum moisture content and compacted to at least 90 percent of the maximum dry density per ASTM D 1557. Suitability and compaction of trench backfill should be evaluated during construction.

Off-site utility trench backfill placement procedures should meet the specifications outlined in the latest edition of the referenced USS (Clark County, 2003). Some near-surface, on-site soils are not anticipated to meet the specifications for Selected Backfill as outlined in Subsection 207.02.01 of the

USS. Suitability and compaction of trench backfill should be evaluated during construction.

Due to the nature of the on-site soils, ponding or jetting of utility trench backfill will not be acceptable.

Trench backfill should be compacted by mechanical means only.

4.5. FOUNDATIONS

The following sections present recommendations for spread footings and concrete slabs-on grade.

May 5, 2017

4.5.1. SPREAD FOOTINGS

Foundations supporting the proposed improvements should be supported on a zone of properly compacted structural fill as previously described. Spread footings should be established at least 18 inches below the lowest adjacent final compacted grade. Spread footings should be at least 12 inches wide and should be reinforced in accordance with the project structural engineer’s recommendations. From a geotechnical standpoint, we recommend that footings be reinforced with two No. 4 or larger reinforcing bars, one placed near the top and one near the bottom of the footings.

Additional reinforcement may be recommended by the structural engineer.

Footings may be designed based on an allowable net dead plus sustained live load bearing pressure of 2,400 pounds per square foot (psf). The allowable bearing pressure for conventional spread footings may be increased by 1,200 psf for each additional foot of embedment or 500 psf for each additional foot of width up to a maximum allowable pressure of 4,000 psf. The allowable bearing pressures may be increased by one-third for temporary wind or seismic loads. The allowable bearing pressure presented above includes a factor of safety against generalized bearing capacity failure of

3.0. Resistance to lateral loads may be estimated using both passive lateral earth support and friction developing between the wall footing and underlying soil, as described in Section 4.7 of this report.

Provided that the earthwork recommendations presented are followed and structural loads are 3 kips or less per lineal foot for continuous footings, and 50 kips or less for isolated footings, total and differential settlements are not anticipated to exceed 1 and ½ inch, respectively. If structural loads exceed these values, GES should be provided the opportunity to re-evaluate our settlement estimates. Structural loads in excess of these estimates may result in increased settlement that could exceed the design tolerance of the structure.

4.6. SEISMIC SITE CLASS

An evaluation testing of the Seismic Site Class by GES via an independent geophysical study was included in the scope of the geotechnical evaluation presented in this report. Based on the results of the seismic shear wave analysis, and in accordance with Section 1613 of the 2012 IBC (ICC, 2012). The ReMi survey is described in Section 2.4.2 of this report. Based on the results of the ReMi survey a Seismic Site Class D is appropriate for design, and the following seismic design parameters may be utilized. The parameters were developed using representative coordinates of 36.2298 degrees latitude and -115.0315 degrees longitude for the project site.

Table 4.6 Spectral Response Accelerations and Site Coefficients

Spectral Response Acceleration at Short

Periods, Ss

Spectral Response Acceleration at 1-Second

Period, S1

Spectral Response Coefficient at Short

Periods, SDs

Spectral Response Coefficient at 1-Second

Period, SD1

0.518g 0.168g 0.478g 0.239g

4.7. LATERAL EARTH PRESSURES

Two conditions are generally considered for retaining wall design that include earth pressure coefficients for the “active” and “at-rest” conditions. In the “active” condition the wall is able to deflect such that stresses from the adjacent soils are lessened. The “at rest” condition considers the walls to be rigid, or restrained, such that the walls do not deflect to lessen stresses from retained soils.

Lateral earth pressures induced by adjacent uniform surface surcharge loads may be estimated as a uniformly distributed lateral load with a magnitude equal to the magnitude of the surface surcharge load multiplied by an earth pressure coefficient. Retaining walls with level backfill should be designed to resist the lateral earth pressures for the appropriate conditions presented in Figure C-1, which were developed in general accordance with the 2012 IBC (ICC, 2012) and the SNA to the 2012 IBC

(SNBO, 2013) utilizing a soil friction angle of 32 degrees and a soil unit weight of 135 pounds per cubic foot.

The values presented in Figure C-1 assume that the build-up of hydrostatic pressure will be prevented. To reduce the build-up of hydrostatic pressure, a wall drainage system, including weep-holes or a footing drainage system, day lighting to an appropriate outlet should be installed behind retaining walls. The wall drainage system should consist of a non-woven geotextile fabric having a maximum average Apparent Opening Size less than 0.43 mm (US Sieve #40) by ASTM D 4751 and a minimum grab tensile strength of 120 pounds or more by ASTM D 4632 wrapped around drain rock. Alternately, the wall drainage system may include should a drain board (e.g., DrainStar Drain

Board or equivalent) used in conjunction with a strip drain (e.g., DrainStar Stripdrain by Tremco

Barrier Solutions, Inc., or equivalent). The strip drain should be a minimum of 12 inches in height and placed continuously along the bottom of the retaining wall.

Resistance to lateral loads may be estimated using both passive lateral earth support and friction developing between wall footings and underlying soil. Passive resistance may be used if foundation backfill soils in front of the wall are compacted to 90 percent of the maximum laboratory dry density

(ASTM D 1557), or more, and if the ground surface in front of the wall is level for a distance of twice the embedment depth of the footing, or more. The upper 12 inches below the ground surface should

May 5, 2017 be neglected when estimating passive resistance. The passive lateral earth support for subsurface walls may be estimated based on an equivalent fluid density of 440 pcf up to a maximum passive lateral pressure of 2,900 psf. A coefficient of friction of 0.39 may be used for the interface between concrete (e.g. tank wall footing) and underlying properly compacted structural fill. The values for the equivalent fluid density and coefficient of friction presented does not include a factor of safety.

Backfill placed behind retaining walls or subsurface walls should meet the criteria for retaining wall backfill presented in this report. Backfill placed behind retaining walls should be placed in 8-inch maximum vertical lifts, moisture conditioned to approximately optimum moisture content, and compacted to between 90 and 95 percent of the maximum laboratory dry density as determined per

ASTM D 1557. Over-compaction adjacent to retaining walls or subsurface walls should be avoided.

The lateral earth pressures shown on Figure C-1 assume that compaction behind retaining walls or subsurface walls will be accomplished with relatively light compaction equipment.

4.8. PIPELINE DESIGN

External loads that will be imposed on buried pipe are dependent on subsurface conditions, type of pipe used, thickness of soil above pipe, method of pipe placement, backfill conditions, and other factors. The effect of traffic loads on the pipeline should be included in the design, in addition to the soil loads, as needed. Additional recommendations for pipeline design are provided in the following subsections.

4.8.1. MODULUS OF SOIL REACTION (E')

It is our understanding that cut-and cover methods will be used to install new pipeline. We have provided the following recommendations for modulus of soil reaction (E') to be used for design along the pipeline alignment.

The modulus of soil reaction (E') is used to characterize the soil-pipe relationship for the purpose of evaluating deflection caused by the external loads on the pipe. E' is dependent upon a variety of factors including trench width, pipe diameter, springline depth, backfill material, backfill compaction, and relative compaction density of the trench wall soils. The pipeline designer should have a sound understanding of how these, and other, factors influence the parameters used in the design equations utilized during the design and consider the effects of the actual pipeline construction methods on those factors.

We have assumed that the depth to the top of the pipe (or cover) will range up to 5 feet in cut-and-cover areas. To provide estimates of E, which may be used in the pipeline design in cut-and-cover areas along the alignment, we have prepared the following table based on methods described in the referenced article, Modulus of Soil Reaction (E') Values for Pipeline Design, (Jeyapalan, 2004) with these assumptions:

• Springline depth of approximately 5-3/4 feet.

• Trench width of approximately 3-1/2 feet.

• E' value of 2,500 psi for Type II Aggregate Base trench backfill.

• E' value of 15,000 psi for CLSM trench backfill.

• Native soil relative compaction density of 85 percent (ASTM D 698).

If these assumptions are not considered appropriate, this office should be notified.

Table 4.8.1. Estimates of Composite Subgrade Modulus, E'

Location Backfill Composite E' Value (psi/inch)

Fuel pipeline Type II Aggregate Base 800

Fuel pipeline CLSM 2,300

4.8.2. VERTICAL LOADS AND FOUNDATIONS

For calculation of overburden loads, Type II Aggregate Base pipe zone and trench final zone backfill soils, when placed and compacted as recommended in this report, may be assumed to have a unit weight of approximately 120 pounds per cubic foot (pcf). This value is based on soils being compacted to a relative compaction of 90 percent of the maximum dry density (ASTM D 1557). We have assumed that controlled low strength material (CLSM) used as pipe zone and trench backfill material will have a unit weight of approximately 120 pcf.

The bases of any vaults should be founded on 4 inches of Type II Aggregate Base, stiff to very stiff fine-grained soils, or structural fill (recompacted native soils). Exposed loose or disturbed surficial soil at the base of vault excavations should be moisture-conditioned to within approximately 2 percent of optimum moisture content and compacted to 90 percent relative compaction (ASTM D 1557). The

Type II Aggregate Base should be in accordance with USS Subsection 704.03.04 and be similarly moisture-conditioned and compacted. An allowable bearing value of 2,400 psf may be used in design of vaults with a base 3 feet wide and embedded 3 feet or more below the lowest adjacent finished

May 5, 2017 grade. This allowable value may be increased by 500 psf for each additional 1 foot of width and

1,200 psf for each additional 1 foot of embedment up to a value of 4,000 psf. Lateral resistance for footings and the frictional resistance to lateral loads are presented in Section 4.8.

4.9. EXTERIOR CONCRETE FLATWORK

Concrete flatwork should be at least 4 inches in thickness. Aggregate base course materials beneath concrete flatwork should be at least 8 inches in thickness and should consist of Type II Aggregate

Base or other similar material approved by the Geotechnical Engineer. Aggregate base should be uniformly placed and compacted to at least 95 percent of the maximum dry density.

The existing on-site subgrade soils beneath concrete flat work should be prepared as described in

Section 4.1 of this report, including overexcavation, moisture-conditioning to near optimum moisture content, and recompaction to at least 90 percent of the maximum dry density as determined by

ASTM D 1557 prior to the placement of supportive aggregate base.

Excessive slump (due to a high water-cement ratio) of the concrete and/or improper curing procedures could lead to excessive shrinkage, cracking or curling of slabs and other flatwork.

Concrete placement and curing operations should be performed in accordance with the American

Concrete Institute (ACI) Manual of Concrete Practice (ACI, 2011).

4.10. RECOMMENDED NON-DEDICATED PAVEMENT SECTIONS

We understand that planned site improvements may include the construction of an asphalt concrete paved access road. Soils underlying the paved road should be overexcavated and replaced with fill as described in the Earthwork section of this report.

To form a basis for design of non-dedicated paved parking and roadways, we have assumed the following:

• A design Equivalent Single Axle Load (ESAL) value of 7,550 for light truck areas and an ESAL value of 35,500 for heavy truck areas (e.g., on-site drive areas).

• 80 percent reliability.

• 0.45 standard deviation.

• 4.2 initial serviceability.

• 2.5 terminal serviceability.

May 5, 2017

• Resilient modulus (MR) of 6,800 pounds per square inch (psi) based on a tested R-value of 30 (from laboratory test results).

If the traffic loadings are not representative of anticipated traffic, then our office should be notified to reevaluate the following recommended pavement sections.

Table 4.10.-1 Recommended Asphalt Concrete Pavement Sections

Loading Condition Design ESALs

Asphalt Thickness (Inches)

Type II Aggregate Base Thickness

(Inches)

Automobile and Light Truck 7,550 2.0 6.0

Heavy Truck 35,500 3.0 7.0

Alternately, a rigid concrete pavement section may be considered. To form a basis for design of rigid pavement for on-site paved parking and access areas, we have assumed the following parameters:

• 85 percent reliability.

• 0.35 standard deviation.

• 4.5 initial serviceability.

• 2.0 terminal serviceability.

• Resilient modulus (MR) of 6,800 pounds per square inch (psi) based on a tested R-value of 30 (from laboratory test results).

• Concrete modulus of rupture of 600 psi and modulus of elasticity of 3,600,000 psi.

• Load transfer coefficient of 3.9 and a drainage coefficient of 1.0.

• An effective modulus of subgrade reaction, k, of 100 psi per inch (pci)

• Subgrade consists of 36 inches or more of structural fill compacted to a relative compaction of 90 percent, as evaluated ASTM D 1557.

If these values are not considered appropriate, this office should be notified. Using these values, a recommended rigid pavement section was developed and the corresponding amount of vehicle traffic (in ESALs) corresponding to the section was estimated. The following table presents the recommended rigid pavement section for on-site parking and access areas and the corresponding amount of traffic.

May 5, 2017

Table 4.10.-2 Recommended Portland Cement Concrete Pavement Sections

Loading Condition ESALs

Portland Cement Concrete Thickness (Inches)

Type II Aggregate Base Thickness

(Inches)

Automobile, Light Truck, and Heavy Truck

80,000 5.0 6.0

The recommended pavement sections assume subgrade soils will have an R-value of 30 or more.

If soils with R-values less than 30 are placed as subgrade beneath pavement…