Attachment_8_-_Orovada_Fire_Station_Reports_and_Feasibility_Study.pdf

Reports

Geotechnical Report 2019-11-01

Conceptual Hydrology Study 2019-11-01

Hazmat Investigation Report 2019-11-01

Feasibility Study 2019-11-01

Geotechnical Report 2019-11-01

REPORT COVER PAGE

Geotechnical Engineering Report Orovada Fire Station

Orovada, Nevada Revised November 16, 2018

Terracon Project No. NB185106

Prepared for:

Short Elliott Hendrickson, Inc.

Denver, Colorado

Prepared by:

Terracon Consultants, Inc.

Sacramento, California

Terracon Consultants, Inc. 50 Goldenland Cour t, Suite 100 Sacramento, Californ ia 95834

P (916) 928 4690 F (916) 928 4697 terracon.com

REPORT COVER LETTER TO SIGN

Short Elliott Hendrickson, Inc.

200 S. Colorado Blvd.

Denver, Colorado 80222

Attn: Mr. Scott Jardine, PE, LEED AP

P: (303) 345-1817 E: sjordine@sehinc.com

Re: Geotechnical Engineering Report

Orovada Fire Station Kunkel Lane Orovada, Nevada

Dear Mr. Jardine:

We have completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with Scope of Work Title I AE Services for Site Development at Orovada Fire Station, dated June 20, 2018. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the proposed project.

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

Sincerely, Terracon Consultants, Inc.

Nicholas Novotny, P.G. Robert Holmer, P.E., G.E.

Senior Staff Geologist Principal Engineer mailto:sjordine@sehinc.com

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REPORT TOPICS

REPORT TOPICS

REPORT SUMMARY

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

SEISMIC CONSIDERATIONS

LIQUEFACTION

CORROSIVITY

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

FLOOR SLABS

LATERAL EARTH PRESSURES

PAVEMENTS

FROST CONSIDERATIONS

GENERAL COMMENTS

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

APPENDIX A – FIELD EXPLORATION

Exhibit A-1 Site Location Exhibit A-2 Exploration Plan Exhibit A-3 Field Exploration Description Exhibits A-4 thru A-12 Test Pit Logs

APPENDIX B – LABORATORY TESTING

Exhibit B-1 Laboratory Test Description Exhibit B-2 Atterberg Limits Test Results Exhibit B-3 Grain size Analysis Exhibit B-4 R-Value Test Results Exhibit B-5 Corrosivity Test Results

APPENDIX C – SUPPORTING DOCUMENTS

Exhibit C-1 Unified Soil Classification Exhibit C-2 Description of Soil Properties Exhibit C-3 Seismic Design Maps Detailed Report http://client.terracon.com/

Orovada Fire Station ■ Orovada, Nevada Revised November 16, 2018 ■ Terracon Project No. NB185106

REPORT SUMMARY

Topic 1 Overview Statement 2

Project Description

The proposed development will consist of a new fire station structure with associated asphalt pavements and concrete flatwork.

Geotechnical Characterization

■ Native subsurface materials encountered at the site generally consisted of 2 to 8 inches of topsoil, underlain by loose to medium dense silty sand to poorly graded sand with variable gravel and cementation to a depth of 3 to 4.5 feet.

Sands were generally underlain by silty to poorly graded gravel with cobbles to the total depth of exploration of 7 feet.

■ Groundwater was not encountered at any time during our investigation.

Collapsible Soils

Near surface soils consist of dry, loose, and weakly cemented sands. These soils are at high risk of suffering collapse settlement upon wetting. As a result, we recommend over-excavation and recompaction of the surface soils to a depth of 5 feet beneath the building footprint.

Earthwork

■ Earthwork for this project will consist of removal of site grading, excavation, and fill placement.

■ As described above, we recommend over-excavation and recompaction of the surface soils to a depth of 5 feet beneath the building footprint. Over-excavation and recompaction shall extend a lateral distance of 5 feet beyond foundation lines.

■ Subsurface silty sands with gravel are suitable for use as general fill for this project. Onsite and import materials to be used as engineered fill for this project should meet the requirements for engineered fill presented in Earthwork

Shallow Foundations

■ The proposed development may be supported on traditional spread footings supported on compacted engineered fill.

■ Additional recommendations may be found in Earthwork

Pavements

With subgrade prepared as noted in Earthwork Pavement thicknesses based on anticipated Equivalent Single Axel Load (ESAL) is as follows:

Concrete:

■ ESAL of 4,710 – 5.0” PCC over 4.0” AB

■ ESAL of 23,500 – 6.0” PCC over 4.0” AB

■ ESAL of 89,800 – 6.0” PCC over 6.0” AB

■ ESAL of 487,000 – 6.0” PCC over 8.0” AB

Asphalt:

■ ESAL of 4,710 – 2.5” ACC over 4.0” AB

■ ESAL of 23,500 – 3.0” ACC over 4.0” AB

■ ESAL of 89,800 – 3.5” ACC over 4.5” AB

■ ESAL of 487,000 – 4.0” ACC over 7.0” AB

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

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INTRODUCTION

Geotechnical Engineering Report Orovada Fire Station

Kunkel Lane Orovada, Nevada

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed Fire Station to be located on the north side of Kunkel Lane in Orovada, Nevada. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions ■ Foundation design and construction

■ Groundwater conditions ■ Floor slab design and construction

■ Site preparation and earthwork ■ Seismic site classification per CBC

■ Pavement design and construction ■ Lateral earth pressures

■ Excavation considerations

The geotechnical engineering scope of services for this project included the advancement of nine

(9) test pits to depths of approximately 6.0 to 7.0 feet below existing site grades.

Maps showing the site and test pit locations are shown in the Site Location and Exploration Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the Test Pit Logs and as separate graphs in the Exploration Results section of this report.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel Information The site is located on the north side of Kunkel Lane in Orovada, Nevada.

See Site Location

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Existing Improvements The site consists of vacant land. Multiple dirt trails traverse the site.

Current Ground Cover

Earthen, sandy, with moderate vegetation consisting of desert shrubs and bushes.

Existing Topography Relatively flat, with a dry creek running east-west across the northern third of the property. The creek branches near the center of the parcel.

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed in the project planning stage. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Information Provided Project Scope of Work and Site Development Feasibility Study was furnished to us by Scott Jardine of SEH.

Project Description The proposed project will consist of a Wildland Fire Station Compound with associated pavements, concrete flatwork, utilities, and landscaping.

Proposed Structure The project will include a fire station structure.

Building Construction We anticipate that the proposed fire station structure will be one to two stories tall, and consist of masonry, wood, or light gauge steel framing, and be founded on a shallow spread footing foundation system with concrete slab on grade floor.

Finished Floor Elevation Within ±3 feet from existing ground surface

Maximum Loads (Assumed)

■ Columns: 100 kips

■ Walls: 5 kips/ft.

■ Slabs: 100 psf

Grading/Slopes A creek runs east to west through the northern portion of the site. The proposed development may include diversion of the existing channel.

Pavements

A paved driveway and parking area will be constructed at the site.

We assume both rigid (concrete) and flexible (asphalt) pavement sections should be considered.

Anticipated Equivalent Single Axel Load (ESAL) is as follows:

■ Auto parking: 4,710

■ Auto and light truck drives: 23,500

■ Heavy truck drives: 89,800

■ Very Heavy Truck Drives: 487,000

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GEOTECHNICAL CHARACTERIZATION

Geologic Setting

The project area is situated within the Basin and Range Geomorphic Provence of Nevada. The Basin and Range consists of a series of northwest trending hills (horsts) and valleys (Grabens) formed structurally through tensional tectonic activity in the region. Horsts and Grabens are often bounded by normal (tensional) faults of low to moderate activity. Grabens experienced a period of glaciation, and subsequent lacustrine facies development after the most recent ice age (~10 million years ago). The most notable lacustrine event being Lake Lahontan.

Horsts generally consist of metamorphic rock of Paleozoic Age intruded by Mesozoic intrusive igneous complexes. Grabens are generally characterized by alluvial basin fill deposits characterized by coarse alluvial fan sequences fining upwards into lacustrine sands, silts and clays. Carbonate and evaproite deposits are also common in low-lying areas.

The native materials underlying the site are considered to be Young Alluvium (Qya), as described in the geologic map of the area1. According to the map, the alluvium is Quaternary in age (duration about 2.6 million years ago to present) and consists of playa, dune, and stream deposits associated with old Lake Lahontan beds. The subsurface materials encountered in our investigation are generally consistent with the mapped geology.

Subsurface Profile

We have developed a general characterization of the subsurface soil and groundwater conditions based upon our review of the data and our understanding of the geologic setting and planned construction. The following table provides our geotechnical characterization.

The geotechnical characterization forms the basis of our geotechnical calculations and evaluation of site preparation, foundation options and pavement options. As noted in General Comments, the characterization is based upon widely spaced exploration points across the site, and variations are likely.

Stratum Approximate Depth to Bottom of Stratum Material Description Consistency/Density

Surface 2 to 8 inches Topsoil: brown to light brown, friable and contained significant organic matter

N/A

Saucedo, G.J., and Wagner, D.L., 1992, Geologic Map of the Chico Quadrangle: California Division of Mines and

Geology, Regional Geologic Map 7A, scale 1:250,000

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Stratum Approximate Depth to Bottom of Stratum Material Description Consistency/Density

1 3 to 4.5 Silty to Poorly Graded Sand with Variable Gravel

Loose to Medium Dense, Slightly

Cemented

Undetermined: Test Pits terminated within this stratum at the planned depth of approximately 7 feet

Silty to Poorly Graded Gravel with Cobbles Medium Dense

Conditions encountered at each Test Pit location are indicated on the individual Test Pit logs shown in the Exploration Results section and are attached to this report. Stratification boundaries on the Test Pit logs represent the approximate location of changes in native soil types;

in situ, the transition between materials may be gradual.

Groundwater Conditions

The boreholes were observed while excavating and after completion for the presence and level of groundwater. The water levels observed in the boreholes can be found on the Test Pit logs in Exploration Results, and are summarized below.

Groundwater was not observed in the remaining Test Pits while excavating, or for the short duration the Test Pits could remain open. However, this does not necessarily mean the Test Pits terminated above groundwater, or the water levels summarized above are stable groundwater levels.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the Test Pits were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the Test Pit logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design Category. Site Classification is required to determine the Seismic Design Category for a structure.

The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7-13.

DESCRIPTION VALUE

2016 California Building Code Site Classification (CBC) 1 D 2

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DESCRIPTION VALUE

Site Latitude N 41.5593°

Site Longitude W -117.7912°

Ss Spectral Acceleration for a Short Period 3 0.490g

S1 Spectral Acceleration for a 1-Second Period 3 0.169g

SMS Maximum Considered Earthquake (MCE) Spectral 3 ponse Acceleration Value (Short Period), SMS

0.690g

SM1 Maximum Considered Earthquake (MCE) Spectral 3 Response Acceleration Value (1-Second Period), SM1

0.358g

Design Spectral Acceleration Value (Short Period), SDS

0.460g

Design Spectral Acceleration Value (1-Second Period), SD1 3 0.239g

Fa Site Coefficient for a Short Period 3 1.408

Fv Site Coefficient for a 1-Second Period 3 2.125

1. Seismic site classification in general accordance with the 2015 International Building Code, which refers to ASCE 7-13

2. The 2015 International Building Code (IBC) requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope does not include the required 100 foot soil profile determination. Test Pits extended to a maximum depth of 7.0 feet, and this seismic site class definition considers that similar soils continue below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be necessary to confirm and/or modify the above site class.

3. These values were obtained using online seismic design maps and tools provided by the USGS (http://earthquake.usgs.gov/hazards/designmaps/).

The site is located in Northern Nevada, which is a seismically active area. The type and magnitude of seismic hazards affecting the site are dependent on the distance to causative faults, the intensity, and the magnitude of the seismic event. The table below indicates the distance of the fault zones and the associated maximum credible earthquake that can be produced by nearby seismic events, as calculated using the USGS Earthquake Hazard Program Unified Hazard tool.

Characteristics and Estimated Earthquakes for Regional Faults

Fault Name Percent

Contribution

Approximate Distance to Site

(kilometers)

Maximum Credible Earthquake (MCE)

Magnitude Santa Rosa System 50 8.10 6.62 7.23 Hoppin Peaks 50 3.27 11.32 6.53

Based on the ASCE 7-10 Standard, the peak ground acceleration (PGAM) at the subject site approximately 0.276g. Based on the USGS 2008 interactive deaggregations, the project site has a mean magnitude of 6.51.

http://earthquake.usgs.gov/hazards/designmaps/

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LIQUEFACTION

Liquefaction is a mode of ground failure that results from the generation of excess pore-water pressures during earthquake ground shaking, causing loss of shear strength. This phenomenon generally occurs in areas of high seismicity, where groundwater is shallow, and loose granular soils or relatively non-plastic fine-grained soils are present. Based on the anticipated depth to groundwater, distance to causative faults, and relative density of subgrade soils at the site, the potential for seismically induced liquefaction at this site is considered low.

CORROSIVITY

The table below lists the results of laboratory soluble sulfate, soluble chloride, electrical resistivity, and pH testing. The values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction.

Corrosivity Test Results Summary

Test Pit Sample Depth (feet)

Soil Description Soluble Sulfate (ppm)

Soluble Chloride

(ppm)

Electrical Resistivity

(Ω-cm) pH

TP-5 1-2 SM 0 0 37,000 7.0

The sulfate test results indicate that the soil from Test Pit TP-5 classifies as Class S0 according to Table 19.3.1.1 of ACI 318-14. This indicates that the sulfate level is negligible when considering corrosion to concrete.

The chloride test results indicate that the soils have a negligable chloride content present.

According to Table 19.3.1.1 of ACI 318-14, the soil should not be considered an external source of chloride (i.e. sea water, etc.) to concrete foundations. Consequently, chloride classes of C0 and C1 should be used where applicable. C0 is defined as, “Concrete dry or protected from moisture” and C1 is defined as, “Concrete exposed to moisture but not to an external source of chlorides”. For the amount of chlorides allowed in concrete mix designs, Table 19.3.2.1 of ACI 318-14 shall be adhered to as appropriate.

Based on the results of the sulfate content test results, ACI 318-14, Section 19.3 does not specify the type of cement or a maximum water-cement ratio for concrete for sulfate Class S0. For further information, see ACI 318-14, Section 19.3.

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GEOTECHNICAL OVERVIEW

A creek runs east to west through the northern portion of the site. The proposed development may include diversion of the existing channel. Additional site preparation recommendations including subgrade improvement and fill placement are provided in the Earthwork section.

Near surface soils consist of dry, loose, and weakly cemented sands. These soils are at high risk of suffering collapse settlement upon wetting. As a result, we recommend over-excavation and recompaction of the surface soils to a depth of 5 feet beneath the building footprint. Over-excavation and recompaction shall extend a lateral distance of 5 feet beyond foundation lines.

The Shallow Foundations section addresses support of the building bearing on over-excavated and recompacted native silty sand soils. The Floor Slabs section addresses slab-on-grade support of the building.

Both rigid and flexible pavement system recommendations are provided for this site. The Pavements section addresses the design of pavement systems.

The General Comments section provides an understanding of the report limitations.

EARTHWORK

Earthwork will include clearing and grubbing, excavations and fill placement. The following sections provide recommendations for use in the preparation of specifications for the work.

Recommendations include critical quality criteria as necessary to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Site Preparation – Over Excavation and Recompaction

Prior to placing fill, existing vegetation and root mat should be removed. Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas. Topsoil was encountered to depths of 2 to 8 inches across the site.

Near surface soils consist of dry, loose, and weakly cemented sands. These soils are at high risk of suffering collapse settlement upon wetting. As a result, we recommend over-excavation and recompaction of the surface soils to a depth of 5 feet beneath the building footprint. Over-excavation and recompaction shall extend a lateral distance of 5 feet beyond foundation lines.

After over-excavation, and prior to fill placement, the resulting subgrade should be proof-rolled with an adequately loaded vehicle such as a fully loaded tandem axle dump truck. The proof-rolling should be performed under the direction of the Geotechnical Engineer. Areas excessively

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Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

Fill Materials and Placement

All fill materials should be inorganic soils free of vegetation, debris, and fragments not larger than four inches in size. Pea gravel or other similar non-cementitious, poorly-graded materials should not be used as fill or backfill without the prior approval of the geotechnical engineer.

Approved imported materials or onsite fill materials with low volume change properties may be used as fill material for general site grading and over-excavation and recompaction of the building pad.

Any imported or onsite soils for use as fill material for the project should conform to low volume change materials as indicated as follows:

Percent Finer by Weight Gradation (ASTM C 136)

3” 100 No. 4 Sieve 40 to 100 No. 200 Sieve 20 to 40 Liquid Limit 30 (Max) No. 200 Sieve 20 to 40 Plasticity Index 15 (max) Maximum expansive index* 20 (max)

*ASTM D 4829

Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift.

Fill lifts should not exceed eight inches in loose thickness.

Fill Compaction Requirements

Compaction requirements for over-excavated and recompacted engineered fill and general fill should meet the following compaction requirements.

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Material Type and Location

Per the Modified Proctor Test (ASTM D 1557)

Minimum Compaction Requirement

Range of Moisture Contents for Compaction Above Optimum Minimum Maximum

Approved On-site or approved import structural fill soils:

90%

Beneath foundations: 0% +4%

Beneath slabs: 90% 0% +4%

Utility trenches (structural areas): 95% 0% +4%

Bottom of excavation receiving fill: 90% 0% +4%

Miscellaneous backfill: 90% 0% +4%

Utility trenches (Landscape areas): 90% 0% +4%

Beneath asphalt pavements: 95% 0% +4%

Beneath concrete pavements: 95% 0% +4%

Aggregate base (beneath pavements): 95% 0% +4%

Utility Trench Backfill

Utility trenches penetrating beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior.

The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

All final grades must provide effective drainage away from the building improvements during and after construction. Water permitted to pond next to the building can result in greater soil movements than those discussed in this report. These greater movements can result in unacceptable differential floor slab movements, cracked slabs and walls, and roof leaks.

Estimated movements described in this report are based on effective drainage for the life of the structure and cannot be relied upon if effective drainage is not maintained.

Exposed ground should be sloped at least 2 percent away from the building extending a minimum of 10 feet beyond the perimeter of the building. After building construction and landscaping, we recommend the Civil Engineer/Surveyor verify final grades to document that effective drainage

Responsive ■ Resourceful ■ Reliable 10 has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary, as part of the structure’s maintenance program.

Planters located within 10 feet of the structure should be self-contained to prevent water accessing the building and pavement subgrade soils. Locate sprinkler mains and spray heads a minimum of 5 feet away from the building line. Collect roof runoff in drains or gutters. Discharge roof drains and downspouts onto pavements which slope away from the building or extend down spouts a minimum of 10 feet away from the structure.

Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when the ground surface beneath such features is not protected by exterior slabs or paving. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent to the foundation system should be minimized or eliminated.

Earthwork Construction Considerations

It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. At the time of our study, moisture contents of the surface and near-surface native soils ranged from 2 to 10 percent. Based on these moisture contents, some moisture conditioning may be needed for the project.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of the floor slab. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become desiccated, saturated, frozen, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and re-compacted prior to floor slab and pavement construction.

Surface water should not be allowed to pond on the site and soak into the soil during construction.

Construction staging should provide drainage of surface water and precipitation away from the building and pavement areas. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils. Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage.

Groundwater was not encountered in our Test Pits during our exploration. Based on our understanding of the proposed development, we do not expect groundwater to affect construction.

If groundwater is encountered during construction, some form of temporary or permanent dewatering may be required. Conventional dewatering methods, such as pumping from sumps, should likely be adequate for temporary removal of any groundwater encountered during

Responsive ■ Resourceful ■ Reliable 11 excavation at the site. Well points would likely be required for significant groundwater flow, or where excavations penetrate groundwater.

All excavations should be sloped or braced as required by OSHA regulations to provide stability and safe working conditions. Temporary excavations will probably be required during grading operations. The grading contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current Occupational Health and Safety Administration (OSHA) Excavation and Trench Safety Standards.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer.

Monitoring should include documentation of adequate removal of vegetation and top soil, proof-rolling and mitigation of areas delineated by the proof-roll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked as necessary until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,500 square feet of compacted fill in the building areas and 5,000 square feet in pavement areas. One density and water content test for every 50 linear feet of compacted utility trench backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. In the event that unanticipated conditions are encountered, the Geotechnical Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

SHALLOW FOUNDATIONS

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

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Design Parameters – Compressive Loads

Item Description Maximum Net Allowable Bearing pressure 1, 2 2,500 psf

Required Bearing Stratum 3 Over-excavated and recompacted native sand soils

Minimum Foundation Dimensions Columns: 18 inches Continuous: 12 inches

Ultimate Passive Resistance 4 (equivalent fluid pressures)

350 pcf

Ultimate Coefficient of Sliding Friction 5 0.40

Minimum Embedment below

Finished Grade 6 24 inches

Humboldt County Frost Depth 24 inches

Estimated Total Settlement from Structural Loads 2 Less than about 1 inch

Estimated Differential Settlement 2, 7 About 2/3 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied. These bearing pressures can be increased by 1/3 for transient loads unless those loads have been factored to account for transient conditions. Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description.

3. Unsuitable or soft soils should be over-excavated and replaced per the recommendations presented in the

Earthwork.

4. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

7. Differential settlements are as measured over a span of 50 feet.

Foundation Construction Considerations

Near surface soils consist of dry, loose, and weakly cemented sands. These soils are at high risk of suffering collapse settlement upon wetting. As a result, we recommend over-excavation and recompaction of the surface soils to a depth of 5 feet beneath the building footprint. Over-excavation and recompaction shall extend a lateral distance of 5 feet beyond foundation lines, as shown below:

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As noted in Earthwork, the footing excavations should be evaluated under the direction of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

FLOOR SLABS

Design parameters for floor slabs assume the requirements for Earthwork have been followed.

Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

Floor Slab Design Parameters

Item Description

Floor Slab Support 1 Native soils that have been over-excavated and recompacted as engineered fill.

Capillary Break Minimum 6 inches of free-draining (less than 6% passing the U.S. No. 200 sieve) crushed aggregate compacted to at least 90% of ASTM D 1557 2, 3

Estimated Modulus of Subgrade Reaction 2

150 pounds per square inch per inch (psi/in) for point loads

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

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3. Free-draining granular material should have less than 6 percent fines (material passing the #200 sieve).

Other design considerations such as cold temperatures and condensation development could warrant more extensive design provisions.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or cracks should be sealed with a water-proof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

Floor Slab Construction Considerations

Finished subgrade within and for at least 10 feet beyond the floor slab should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should approve the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

LATERAL EARTH PRESSURES

Design Parameters

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to values indicated in the following table. Earth pressures will be

Responsive ■ Resourceful ■ Reliable 15 influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top.

The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

Lateral Earth Pressure Design Parameters

Earth Pressure Condition 1

Coefficient for Backfill Type2

Surcharge Pressure 3, 4, 5 p1 (psf)

Effective Fluid Pressures (psf) 2, 4, 5

Active (Ka) 0.31 (0.31)S (35)H At-Rest (Ko) 0.53 (0.53)S (55)H Passive (Kp) 3.25 --- (350)H

1. For active earth pressure, wall must rotate about base, with top lateral movements 0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance.

2. Uniform, horizontal backfill using on-site material, compacted to at least 90 percent of the ASTM D 1557 maximum dry density, rendering a maximum unit weight of 115 pcf.

3. Uniform surcharge, where S (psf) is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

5. No safety factor is included in these values.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils.

For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively.

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PAVEMENTS

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs, noted in this section, must be applied to the site, which has been prepared as recommended in the Earthwork section.

Pavement Design Parameters

Design of Asphaltic Concrete (AC) pavements are based on the procedures outlined in the American Association of State and Highway Transportation Officials (AASHTO) Guide for Design of Pavement Structures. Design of Portland Cement Concrete (PCC) pavement sections were designed using PCA “Thickness Design for Concrete Highway and Street Pavements.” Asphalt mix design for this project should conform to Section 703 of the Nevada Department of Transportation (NDOT) Standard Specifications for Road and Bridge Construction. We consider asphalt bituminous mixes such as PG 76-22NVTR, or PG 64-28NVTR to be suitable for use on this project. Aggregate used for bituminous mixes shall comply with the specifications for Type 2 as defined in Section 705 of the NDOT Standard Specifications for Road and Bridge Design.

Pavement subgrades are expected to consist of native on-site soils at elevations roughly equivalent to existing grades. According, a bulk sample of near surface soil was collected for laboratory testing, and subgrade support was estimated from a laboratory prepared remolded R- Value test. An R-Value of 68 was obtained from the sample collected at Test Pit TP-8.

Based on site soil variability, and considering climatic effects, a design R-Value of 50 was used for the AC pavement designs, and a modulus of subgrade reaction of 150 pci was use for the PCC pavement designs. The values were determined through lab testing, and also empirically derived based upon our experience with the describe soil type subgrade soils and our understanding of the quality of the subgrade as prescribed by the Site Preparation conditions as outlined in Earthwork. A modulus of rupture of 600 psi was used for pavement concrete.

Pavement Section Thicknesses

The following table provides options for AC and PCC Sections:

Asphaltic Concrete Design

Traffic Area Equivalent Single Axel Load (ESAL) AC (inches) Aggregate Base

(inches) Total Thickness

(inches) Auto Parking 4,710 2.5 4.0 6.5

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Asphaltic Concrete Design

Traffic Area Equivalent Single Axel Load (ESAL) AC (inches) Aggregate Base

(inches) Total Thickness

(inches) Auto Drives 23,500 3.0 4.0 7.0

Truck Drives 89,800 3.5 4.5 8.0

Heavy Truck Drives 487,000 4.0 7.0 11.0

Portland Cement Concrete Design

Traffic Area Equivalent Single Axel Load (ESAL) PCC (inches) Aggregate Base

(inches) Total Thickness

(inches) Auto Parking 4,710 5.0 4.0 9.0

Auto Drives 23,500 6.0 4.0 10.0

Truck Drives 89,800 6.0 6.0 12.0

Heavy Truck Drives 487,000 6.0 8.0 14.0

The above sections represent minimum design thicknesses and, as such, periodic maintenance should be anticipated. The Portland cement concrete pavement should have a minimum 28-day compressive strength of 4,000 psi.

The estimated pavement sections provided in this report are minimums for the assumed design criteria, and as such, periodic maintenance should be expected. Areas for parking of heavy vehicles, concentrated turn areas, and start/stop maneuvers could require thicker pavement sections. Edge restraints (i.e. concrete curbs or aggregate shoulders) should be planned along curves and areas of maneuvering vehicles. A maintenance program including surface sealing, joint cleaning and sealing, and timely repair of cracks and deteriorated areas will increase the pavement’s service life. As an option, thicker sections could be constructed to decrease future maintenance.

Concrete for rigid pavements should have a minimum 28-day compressive strength of 4,000 psi, and be placed with a maximum slump of 4 inches. A minimum 4-inch thick base course layer is recommended to help reduce potential for slab curl, shrinkage cracking, and subgrade pumping through joints. Proper joint spacing will also be required to prevent excessive slab curling and shrinkage cracking. Joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer.

Where practical, we recommend early-entry cutting of crack-control joints in PCC pavements.

Cutting of the concrete in its “green” state typically reduces the potential for micro-cracking of the pavements prior to the crack control joints being formed, compared to cutting the joints after the

Responsive ■ Resourceful ■ Reliable 18 concrete has fully set. Micro-cracking of pavements may lead to crack formation in locations other than the sawed joints, and/or reduction of fatigue life of the pavement.

Openings in pavements, such as decorative landscaped areas, are sources for water infiltration into surrounding pavement systems. Water can collect in the islands and migrate into the surrounding subgrade soils thereby degrading support of the pavement. This is especially applicable for islands with raised concrete curbs, irrigated foliage, and low permeability near-surface soils. The civil design for the pavements with these conditions should include features to restrict or to collect and discharge excess water from the islands. Examples of features are edge drains connected to the storm water collection system, longitudinal subdrains, or other suitable outlet and impermeable barriers preventing lateral migration of water such as a cutoff wall installed to a depth below the pavement structure.

Dishing in parking lots surfaced with ACC is usually observed in frequently-used parking stalls (such as near the front of buildings), and occurs under the wheel footprint in these stalls. The use of higher-grade asphaltic cement, or surfacing these areas with PCC, should be considered. The dishing is exacerbated by factors such as irrigated islands or planter areas, sheet surface drainage to the front of structures, and placing the ACC directly on a compacted clay subgrade.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase.

Pavement Maintenance

The pavement sections represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore, preventive maintenance should be planned and provided for through an on-going pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment.

Maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventive maintenance is usually the priority when implementing a pavement maintenance program. Additional engineering observation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required.

Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

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■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2%.

■ Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage.

■ Install joint sealant and seal cracks immediately.

Aggregate Surface Storage Yard Recommendations

We anticipate an aggregate surfaced storage yard to be included in this project. As a minimum, the aggregate surface course should consist of 6 inches in depth after full compaction, and be constructed directly above 10 inches of scarified, moisture conditioned, and compacted native soils.

The aggregate surface course should conform to Type 2 Class A or B aggregate base in accordance with Section 704 of NDOT Standard Specifications for Road and Bridge Design, or other approved local governing specifications.

The aggregate surface course should be compacted to a minimum of 95 percent of the maximum dry density as determined by ASTM D1557. The surface course should be compacted at a moisture content not more than 4 percent above the optimum moisture content defined by ASTM D1557.

Based upon the soils conditions encountered in the test borings, the use of on-site soils for construction of onsite storage yard is considered acceptable. Without the use of asphalt concrete or other hardened material to surface the roadways, there is an increased potential for erosion and rutting of the roadway to occur.

Positive drainage should be provided during construction and maintained throughout the life of the gravel paved storage yard. Proposed storage yard design should maintain the integrity of the yard and eliminate ponding. The un-surfaced roads are expected to function with periodic maintenance.

Aggregate Surface Storage Yard Construction Considerations

Preventative maintenance should be planned and provided for through an on-going pavement management program in order to enhance future gravel surface performance. Preventative maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment.

Materials and construction of pavements for the project should be in accordance with the requirements and specifications of the State of Nevada Department of Transportation, or other approved local governing specifications.

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Base course or surfacing materials should not be placed when the surface is wet. Surface drainage should be provided away from the edge of the storage yard to reduce lateral moisture transmission into the subgrade.

FROST CONSIDERATIONS

The subgrade soils encountered on this site consist largely of free draining sands and gravels.

Granular soils with large void spaces permit water to freeze in place and expand into the void spaced between granular particles without causing surface heave. As a result, we do not anticipate frost susceptible soils to be encountered during grading at this site.

If frost susceptible soils, such as silts and clays, are encountered and frost action needs to be eliminated in critical areas, we recommend the use of non-frost susceptible (NFS) fill, such as sands and gravels, or structural slabs (for instance, structural stoops in front of building doors).

Placement of NFS material in large areas may not be feasible; however, the following recommendations are provided to help reduce potential frost heave:

■ Provide surface drainage away from the building and slabs, and toward the site storm drainage system.

■ Install drains around the perimeter of the building, stoops, below exterior slabs and pavements, and connect them to the storm drainage system.

■ Grade clayey subgrades, so groundwater potentially perched in overlying more permeable subgrades, such as sand or aggregate base, slope toward a site drainage system.

■ Place NFS fill as backfill beneath slabs and pavements critical to the project.

■ Place a 3 horizontal to 1 vertical (3H:1V) transition zone between NFS fill and other soils.

■ Place…