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Table of Contents
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Introduction ....................................................................................................... 1
Project Description .......................................................................................... 2
Structure/Development Information ................................................................................................. 2 Hazardous Waste Cleanup .................................................................................................................... 3 Grading Concepts ..................................................................................................................................... 3
Site Conditions ................................................................................................. 4
Previous Improvements.......................................................................................................................... 4 Existing Improvements ........................................................................................................................... 4 Topography ................................................................................................................................................. 5 Vegetation ................................................................................................................................................... 5
Exploration ......................................................................................................... 6
Drilling .......................................................................................................................................................... 6 Test Pits ........................................................................................................................................................ 6 Material Classification ............................................................................................................................. 7
Laboratory Testing ........................................................................................... 8
Index Tests .................................................................................................................................................. 8 Chemical Tests........................................................................................................................................... 8
Geologic and General Soil Conditions ...................................................... 9
Geologic Hazards ........................................................................................... 12
Seismicity .................................................................................................................................................. 12 Faults .......................................................................................................................................................... 12 Ground Motion and Liquefaction ...................................................................................................... 13 Flood Plains .............................................................................................................................................. 13 Other Geologic Hazards ....................................................................................................................... 13
Discussion and Recommendations .......................................................... 14
General Information .............................................................................................................................. 14 Site Preparation ....................................................................................................................................... 15 Trenching, Excavation and Utility Backfill ....................................................................................... 16 Mass Grading ........................................................................................................................................... 18 Fill Settlement .......................................................................................................................................... 19 Seismic Design Parameters ................................................................................................................. 19 Foundation ............................................................................................................................................... 20 Retaining Walls ........................................................................................................................................ 21
Table of Contents
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T Subsidence and Shrinkage .................................................................................................................. 22 Slope Stability and Erosion Control .................................................................................................. 22 Site Drainage ............................................................................................................................................ 23 Geotechnical Considerations for Detention Basins ..................................................................... 23 Concrete Slabs ......................................................................................................................................... 23 Asphalt Concrete .................................................................................................................................... 25 Corrosion Potential ................................................................................................................................ 26
Anticipated Construction Problems ......................................................... 27
Quality Control ............................................................................................... 28
Standard Limitations Clause ....................................................................... 29
References ....................................................................................................... 30
Tables
1 - Minimum Required Properties for Separator Geotextile
2 - Maximum Allowable Temporary Slopes
3 - Guideline Specification for Imported Structural Fill
4 - Seismic Design Criteria Using 2012 International Building Code 5 - Retaining Wall Design Parameters
6 - Sulfate Exposure Class
Plates
1 - Plot Plan
2 - Test Pit and Boring Logs
3 - USCS Soil Classification Chart 4 - Index Test Results
Appendices
A - Chemical Test Results
Introduction
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Introduction Presented herein are the results of Black Eagle Consulting, Inc.’s (BEC’s) geotechnical investigation, laboratory
testing, and associated geotechnical design recommendations for the proposed warehouse-style building to be
located southeast of the intersection of Military Road and Echo Avenue in Reno, Nevada These recommendations are based on surface and subsurface conditions encountered in our explorations and on details of the proposed
project as described in this report. The objectives of this study were to:
1. Determine general soil and groundwater conditions pertaining to design and construction of the proposed warehouse building.
2. Provide recommendations for design and construction of the project as related to these geotechnical conditions.
The area covered by this report is shown on Plate 1 (Plot Plan). Our investigation included field exploration,
laboratory testing, and engineering analysis to determine the physical and mechanical properties of the various on-
site materials. Results of our field exploration and testing programs are included in this report and form the basis
for all conclusions and recommendations.
The services described above were conducted in accordance with the BEC Professional Geotechnical Agreement dated December 8, 2017, which was signed by Mr. La Montagne of Hunt Southwest.
Project Description
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Site Plan
Project Description The project site consists of an irregularly shaped parcel of approximately 46.6 acres located in Washoe County,
Nevada. The site is entirely contained in Section 29, Township 21 North, Range 19 East, Mount Diablo Meridian.
The parcel is currently vacant and undeveloped and is bordered to the north by Echo Avenue and undeveloped land, to the east by undeveloped land and commercial developments, to the south by undeveloped land, and to
the west by Military Road. Access to the site is obtained off of Echo Avenue or ungraded access off of Military
Road.
Structure/Development Information The building will be a single-story, Portland cement concrete (PCC) tilt-up panel structure with approximately
700,000 square feet and will be supported by PCC shallow footings with a PCC slab-on-grade floor. Truck loading
docks and associated truck ramps will be included on both long sides of the building. Asphalt concrete parking lots
and associated driveways will also be constructed for the project. Two detention basins are planned within the northeastern and southeastern limits of the project site.
Project Description
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Hazardous Waste Cleanup Based on the review of Google Earth® historical aerial images, the northern portion of the site hosted various improvements including pond-like features prior to 2000. These improvements have been demolished, and the
area has been graded/filled. Based on the Nevada Division of Environmental Protection (NDEP) Certificate of
Completion Voluntary Cleanup Program for the site area provided by you, the previous improvements appear to be associated with the former Dodd/Beal Fire Academy, a firefighting training facility. The NDEP certificate
indicates the hazardous materials within the site have been remediated and may have included removal of the
upper 8 feet of contaminated soils and backfilling with clean materials.
The project environmental consultant, McGinley and Associates (McGinley) of Reno, Nevada, is currently completing a Phase 1 Environmental Assessment. Several boring and test pit locations were located within areas
of possible contaminant remediation based on historical aerial images and the preliminary findings of McGinley.
Grading Concepts The preliminary grading plan, dated January 2, 2018 by Tectonics Design Group (Tectonics Design Group, 2018),
indicates the parcel will be mass graded cut to fill with on-site materials. Topography throughout the site slopes
gently to moderately south along Military Road and steeply along its southeastern boundary. Cuts and fills will be
up to approximately 35 and 40 feet, respectively. The majority of cut will be located within the northern two-thirds of the building pad and fill will be located within the southern one-third of the pad.
Site Conditions
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Site Conditions – View to southeast of demolition debris.
Site Conditions Previous Improvements The northern portion of the site was previously associated with the former
Dodd/Beal Fire Academy. Associated
improvements included several buildings,
storage tanks, fuel containers, and storage containers located within the north central
portion of the site. Metal fencing is present
surrounding the former fire academy
facilities. Three to five ponds were also present within the northeastern portion of
the site. Based on Google Earth® aerial
imagery, the improvements appear to have
been demolished prior to 2003. Additional grading/site remediation occurred between
2004 and 2006. During this time the
ponds were backfilled and several areas of
contaminated soils were removed and replaced with clean fill according to NDEP documents. The final work included filling several ditches and rough
grading the site to slope gradually to the east-northeast. The final surface was left windrowed within the northern
portion of the site. The resulting surface contains moderate amounts of PCC debris and minor construction debris
scattered around. Three large piles of debris are present in the southern portion of the former fire academy site including wooden debris from buildings and PCC fragments from foundations and various improvements.
The northwestern portion of the site has been mass graded to build a pad at grade with the adjacent roadways. An
existing fill slope trends southwest to northeast from Military Road to the intersection of Echo Avenue and Mt.
Limbo Street. The fill slope is about 8 to 10 feet tall.
Existing Improvements The eastern boundary of the site lies at the top of a cut slope associated with the commercial developments east
of the site. A subdued drainage channel is located behind the shoulder of the slope, and a PCC and rock lined brow ditch is present at the slope shoulder. The subdued channel is then directed to a PCC and rock lined
channel down the face of the slope into the commercial complex. Overhead utility lines extend along the southern
shoulder of Echo Avenue east across the site.
Site Conditions
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Site Conditions – View to south showing existing fill slope and
gentle bench topography.
Topography The site’s topography is complex and varied. Overall, the site slopes gently to the
south along Military Road, with gentle to
moderate cross slopes to the east-
northeast towards Lake Lemmon. Adjacent to Military Road, a gently sloping bench
extends to the east before steepening.
Total vertical relief across the site is about
85 feet. An elevation high of 5,045 feet above mean sea level (msl) is located in
the northwestern corner of the site, and a
low of 4,960 feet is located along the
southeastern boundary of the site. The northern graded portion of the site slopes
gently to the east before falling off to
depressions where former ponds existed
prior to remediation efforts. The southern portion of the site includes 2 moderate to
steep east sloping ravines with several other minor drainages. As noted above, the northwest corner of the site has
been graded to a relatively level pad, and an 8- to 10-foot tall fill slope exists.
Vegetation The overall site includes moderate populations of weeds, grasses and brush. Disturbed areas have regrown
vegetation to levels similar to the undisturbed portions of the site.
Exploration
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Drilling Exploration
Exploration The Military Road and Echo Avenue building site was explored by test pits and soil borings. The test pits were
located throughout out the site and includes 4 test pits within areas of possible fill or contamination remediation.
The borings were located in the northern portion of the site to confirm the depth/presence of fill soils and in areas of deep cut.
Drilling The site was explored on December 19, 2017 and January 4, 2018 by drilling 7 test borings. The borings were drilled
using 6-inch-outside-diameter (O.D.), 3-¼-inch-inside-
diameter (I.D.), hollow-stem augers and a truck-mounted
CME 55 soils sampling drill rig. Borings B-06 and B-07 were advanced using a 3-inch-diameter tri-cone bit and mud-
rotary drilling technique in order to penetrate rock materials
in the subsurface. The maximum depth of exploration was
30.5 feet below the existing ground surface. The locations of the test borings are shown on Plate 1.
The native soils were sampled in-place every 2 to 5 feet by
use of a standard, 2-inch-O.D., split-spoon sampler driven by
a 140-pound safety drive hammer with a 30-inch stroke operated with a rope and cathead. The number of blows to
drive the sampler the final 12 inches of an 18-inch
penetration (Standard Penetration Test [SPT] - American
Society for Testing and Materials [ASTM] D 1586) into undisturbed soil is an indication of the density and
consistency of the material.
Test Pits On December 18, 2017 the site was explored by excavating 14 test pits using a CAT® 416 B rubber-tired
backhoe. Locations of the test pits are shown on Plate 1. The maximum depth of exploration was 12.5 feet below
the existing ground surface. Bulk samples for index testing were collected from the trench wall sides at specific
depths in each soil horizon. Pocket penetrometer testing was performed in exposed, fine-grained soil strata to assess in-place, unconfined compressive strength for evaluating trench stability. Backfill was loosely placed and the
area re-graded to the extent possible with equipment on hand.
Exploration
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Material Classification A geologist examined and identified all soils in the field in accordance with ASTM D 2488. During drilling/test pit exploration, representative bulk samples were placed in sealed plastic bags and returned to our Reno, Nevada
laboratory for testing. Additional soil classification was subsequently performed in accordance with ASTM 2487
(Unified Soil Classification System [USCS]) upon completion of laboratory testing, as described in the Laboratory
Testing section. Logs of the test pits/borings are presented as Plate 2 (Test Pit and Boring Logs), and a USCS chart has been included as Plate 3 (USCS Soil Classification Chart).
Laboratory Testing
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Grain Size Analysis
Laboratory Testing
All soils testing performed in the BEC soils laboratory is
conducted in general accordance with the standards and
methodologies described in Volume 4.08 of the ASTM Standards.
Index Tests Samples of each significant soil type were analyzed to determine their in-situ moisture content (ASTM D
2216), grain size distribution (ASTM D 422), and
plasticity index (ASTM D 4318). The results of these
tests are shown on Plate 4 (Index Test Results). Test results were used to classify the soils according to ASTM
D 2487 and to verify field logs, which were then
updated as appropriate. Classification in this manner
provides an indication of the soil's mechanical properties and can be correlated with standard penetration testing and published charts (Bowles, 1996; Naval Facilities
Engineering Command [NAVFAC], 1986a and b) to evaluate bearing capacity, lateral earth pressures, and
settlement potential.
Chemical Tests Chemical testing was performed on representative samples of site foundation soils to evaluate the site materials’
potential to corrode steel and PCC in contact with the ground. The samples were tested for pH, resistivity, redox
potential, soluble sulfates, and sulfides. The results of the chemical tests are shown on Appendix A (Chemical Test Results). Chemical testing was performed by Silver State Analytical Laboratories of Reno, Nevada.
Geologic and General Soil Conditions
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Geologic and General Soil Conditions The site lies in Lemmon Valley north of the Truckee Meadows in an area mapped by the Nevada Bureau of Mines
and Geology ([NBMG] Bonham and Bingler, 1973) as Quaternary age Alluvium of Stead Airport and Tertiary sediments, with a narrow sliver of Quaternary age Pediment gravels along its eastern boundary (Cordy, 1985a).
The NBMG describes the alluvium as Reddish-brown, very poorly sorted, arkosic pebbly muddy sand derived from
Qpg (Pediment gravels) and Qpf. Moderately developed argillic (B2t) soil. Forms thin (≤ 2 m) veneer overlying Ts. The Alluvium of Stead Airport is mapped throughout the site and with isolated windows of Tertiary sediments exposed in east sloping ravines.
The native soils encountered during site exploration are consistent with the geologic map. The Alluvium of Stead
Airport generally consists of the upper 6 to 10 feet of the soil profile and includes massive silty to clayey sands
with little gravel, and isolated surficial clay and clay-rich soils. The underlying Tertiary sediments consist of poorly to
moderately indurated sandstone that has the consistency of slightly to moderately cemented soil. The sandstone
includes interbedded clayey sand, silty sand, silts and clays. Isolated silty sand with gravel soils similar to the
Pediment gravels are present downslope in the eastern portion of the site. Overall the native soils consist of
granular silty to clayey sands, with isolated clays near surface and as interbedded layers at depth.
Fill Materials
Several areas of undocumented fill are present in the northern portion of the site including a surface layer of fill
throughout from later grading activities. This later grading resulted in shallow, less than 2 feet thick, fill throughout the northern half of the site. Scattered debris related to demolition is also present. The majority of the
undocumented fills on the site result from 3 activities:
Mass grading of the northwestern pad area
Reclamation of pond areas and site demolition of the fire academy
Remediation of isolated contaminated soils areas
The northwestern pad area was mass graded to extend a pad at grade to the level of the adjacent roadways. Fill is
present in a wedge thickening to the southeast up to about 10 feet thick. Fill soils are generally silty or clayey sand
with gravel and include asphalt grindings and chunks. The fill is described as brown, moist, medium dense, and contains about 20 to 25 percent non-plastic to medium plasticity fines and 15 to 20 percent gravel. Asphalt
concrete and PCC fragments up to about 8 inches in diameter makes up to 5 percent of the total soil mass.
Geologic and General Soil Conditions
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6 Three known pond areas were filled during reclamation of the fire academy along the northeast boundary of the
site. Additional ponds or depressions are possible in the area, but could not be confirmed through exploration or
aerial images. During exploration, fill 8 to 10 feet thick was encountered in 2 of the ponds. The fill materials are generally silty sand soils with minor amounts of asphalt concrete and PCC fragments. The fill is described as brown
to light brown, slightly moist to moist, loose to medium dense, and contains about 20 percent non-plastic to low
plasticity fines and up to 10 percent gravel. Isolated layers of fill contain up to about 5 percent asphalt concrete
and PCC fragments and trace amounts of woody debris to 1 inch in diameter.
Several isolated areas of contaminated soil remediation are identified on figure(s) from McGinley and located via
aerial imagery. Two borings and two test pits were advanced near areas of possible removal of contaminated soil
and replacement with clean fill. Only one location, Test Pit TP-12, encountered fill approximately 8 feet thick. This
depth coincides with NDEP documentation of soil remediation plans. Like other areas, the fill consists of granular silty sand with non-plastic to low plasticity fines. A slight chemical odor was present within the fill and the
underlying soils through 16 feet in depth. It appears the areas of soil remediation (removal and replacement) are
isolated or limited in horizontal extent. Because no definitive coordinates/(as-built for these areas) are available, it
is likely that additional areas of remediation are present.
Native Materials
The native soils profile consists of predominantly granular silty and clayey sands through about 10 feet depth. A
surficial layer of silty sand is about 2 feet thick and cohesionless, while soils from 2 to 6 feet are generally strongly
cemented and very dense. Within the surficial soils, isolated areas of clay and clay-rich soils are present in the
central and northwestern portions of the site through depths of about 4 to 9 feet. The deeper native materials include poorly to moderately indurated sandstone that breaks down to silty and clayey sands with lesser amounts
of clay and silt. The deeper bedrock appears to be correlative to Hunter Creek Sandstone.
The alluvial soils up to about 10 feet in depth consist of isolated surficial clays and interbedded silty and low
plasticity clayey sands. Clay-rich soils, encountered in Borings B-05 through B-07, and in Test Pits TP-05 through TP-07 from about 2 to 9 feet depth, are generally 2 to 3 feet thick. The clay-rich soils are described as dark brown
to reddish brown to tan, moist to very moist, very dense (very stiff), and contain about 35 to 60 percent medium
to high plasticity fines and 40 to 65 percent fine to coarse sand. The granular silty and clayey sands, that dominate
the soils profile, are described as brown to light brown to tan, medium dense to very dense, and contain about 15 to 35 percent non-plastic to medium plasticity fines and up to 15 percent angular to subrounded gravel. Gravel is
generally present in trace amounts, and the soils are moderately to strongly cemented. Difficult digging and drilling
conditions were encountered due to cemented soils and the presence of underlying sandstone.
Geologic and General Soil Conditions
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6 From about 10 or 15 feet depth through the maximum depth of exploration (30.5 feet), the native materials
consist of Tertiary sediments consisting predominantly of sandstone that is relatively weak rock. The Tertiary sediments are a young, partially consolidated (poorly to moderately indurated) rock unit consisting of clastic basin
fill sediments. Generally, the Tertiary sediments are granular in nature. In SPT samples, the sandstone breaks
down to soil size clasts with consistency ranging from poorly graded to clayey sand and includes isolated clays.
The predominantly granular rock samples are described as tan to light reddish brown, moist, dense to very dense, and contain about 10 to 40 percent non-plastic to medium plasticity fines and up to 15 percent subrounded
gravel. The interbedded clays and silts are described as olive green to light gray, moist, very stiff to hard, and
contain about 60 to 80 percent non-plastic to high plasticity fines and 20 to 40 percent fine to coarse sand.
Groundwater was not encountered during exploration and is expected to lie at a depth well below that which would affect design or construction.
Geologic Hazards
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Geologic Hazards Seismicity Much of the western United States is a region of moderate to intense seismicity related to movement of crustal masses (plate tectonics). By far, the most seismically active regions, outside of Alaska, are in the vicinity of the San
Andreas Fault system of western California. Other seismically active areas include the Wasatch Front in Salt Lake
City, Utah, which forms the eastern boundary of the Basin and Range physiographic province, and the eastern
front of the Sierra Nevada Mountains, which is the western margin of the province. The Lemmon Valley area lies near the eastern base of the Sierra Nevada, within the western extreme of the Basin and Range. It must be
recognized that there are probably few regions in the United States not underlain at some depth by older bedrock
faults. Even areas within the interior of North America have a history of strong seismic activity.
Seismicity within the Lemmon Valley area is considered about average for the western Basin and Range Province (Ryall and Douglas, 1976). It is generally accepted that a maximum credible earthquake in this area would be in
the range of magnitude 7 to 7.5 along the frontal fault system of the Eastern Sierra Nevada. The most active
segment of this fault system in the Reno area is located at the base of the mountains near Thomas Creek, Whites
Creek, and Mt. Rose Highway, some 19 miles south-southeast of the project.
Faults The published earthquake hazards map (Cordy, 1985b) and the United States Geological Survey (USGS)
Quaternary Fault and Fold database (USGS, 2017a) show a fault approximately 800 feet to the east of the site. The fault is identified as an early to mid-Pleistocene in age. Because no faults of any age are mapped as passing
through or in the immediate vicinity of the project site, nor were any identified during our site investigation, no
additional fault hazard investigation or building setback are necessary for the project.
Recurrence intervals for Nevada earthquakes along faults that have been studied are estimated to be in the range of 6,000 to 18,000 years in western Nevada (Bell, 1984). The very active eastern boundary faults of the Sierra
Nevada Mountains may have a shorter recurrence interval of 1,000 to 2,000 years. Many of the smaller faults may
be the result of one-time events in response to movement along a better developed and more active fault system
a considerable distance away.
Geologic Hazards
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Ground Motion and Liquefaction Mapping by the USGS indicates that there is a 2 percent probability that a bedrock ground acceleration of 0.64 g will be exceeded in any 50-year interval (USGS, 2017b). Including the effects of potential attenuation and using
the procedures recommended by the 2012 International Building Code (IBC), a peak ground acceleration of 0.43
g is appropriate for use in analysis of this site (International Code Council [ICC], 2012). This value corresponds to the design spectral acceleration (two-thirds of the maximum spectral response acceleration) at zero period based
on a Site Class D and a peak bedrock ground acceleration of 0.64 g as noted above. Only localized amplification
of ground motion would be expected during an earthquake.
Flood Plains The Federal Emergency Management Agency (FEMA) has identified the site as lying in unshaded Zone X, or
outside the limits of a 500-year flood plain (FEMA, 2009).
Other Geologic Hazards A moderate potential for dust generation is present if grading is performed in dry weather. No other geologic
hazards were identified.
Discussion and Recommendations
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Discussion and Recommendations General Information The project will involve design and construction of an approximately 700,000-square-foot tilt-up panel building and associated asphalt concrete access drives and parking areas. As previously discussed significant cuts and fills
on the order of 35 and 40 feet, respectively, will be needed to achieve a level pad for construction of the
proposed improvements. The majority of cut will be located within the northern two-thirds of the building pad and
fill will be located within the southern one-third of the parcel.
The site exhibits areas of uncontrolled fill soils up to approximately 10 feet thick associated with previous
demolition, mass grading, and remediation of contaminated soils, however proposed grading is such that the
material cuts needed for the building pad will remove a significant portion of the uncontrolled fill. Sporadic layers
of clay soils are present at the site and will be encountered during mass grading. Clay soils should be separated from project improvements either by site filling or over-excavation and replacement with structural fill as discussed
in the Site Preparation section.
The recommendations provided herein, and particularly under Site Preparation, Mass Grading, Foundation, and
Quality Control, are intended to minimize risks of structural distress related to consolidation or expansion of native soils and/or structural fills. These recommendations, along with proper design and construction of the structure
and associated improvements, work together as a system to improve overall performance. If any aspect of this
system is ignored or is poorly implemented, the performance of the project will suffer. Sufficient quality control
should be performed to verify that the recommendations presented in this report are followed.
Structural areas referred to in this report include all areas of buildings, concrete slabs and asphalt pavements, as
well as pads for any minor structures. The term engineer, as presented below, pertains to the civil or geological
engineer that has prepared the geotechnical engineering report for the project or who serves as a qualified
geotechnical professional on behalf of the owner.
All compaction requirements presented in this report are relative to ASTM D 1557. For the purposes of this
project:
Fine-grained soils are defined as those with more than 40 percent by weight passing the number
200 sieve, and a plastic index lower than 15.
Clay soils are defined as those with more than 30 percent passing the number 200 sieve, and a
plastic index greater than 15.
Granular soils are those not defined by the above criteria.
Discussion and Recommendations
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8 Any detailed evaluation of the site for the presence of surface or subsurface hazardous substances is beyond the
scope of this investigation. When suspected hazardous substances are encountered during routine geotechnical
investigations, they are noted in the exploration logs and reported to the client. Soils exhibiting a petroleum odor were encountered in Boring B-07. Black Eagle Consulting, Inc. collected samples of soils from Boring B-07 and
notified Hunt Southwest. Based on the review of a site map provided by McGinley, Boring B-07 appears to be
located in the vicinity of former burn pads that have been demolished. We understand the requirements and
protocols for handling contaminated soils encountered during excavation activities associated with the project are being currently being established by McGinley.
Site Preparation All vegetation shall be stripped and grubbed from structural areas and removed from the site. A stripping depth of 0.2 to 0.3 feet is anticipated. Roots greater than ½ inch in diameter shall be removed, where necessary, to a
minimum depth of 12 inches below finished grade. Resulting excavations shall be backfilled with structural fill
compacted to 90 percent relative compaction.
The test pits were excavated by a backhoe at the approximate locations shown on Plate 1. Locations were determined in the field by approximate means. All test pits were backfilled upon completion of the field portion of
our study, and the backfill was compacted to the extent possible with equipment on hand. However, the backfill
was not compacted to the requirements presented herein under Mass Grading. The backfill should be removed
and recompacted in accordance with the requirements contained in this report. Failure to properly compact backfill could result in excessive settlement of improvements located over test pits.
Clay soils were found to exist sporadically and at variable depths. The clay soils were classified as moist to very
moist, medium dense/very stiff to very dense/hard, and as exhibiting medium to high plasticity. Laboratory testing
performed on these materials determined the clay soils exhibit plasticity indices on the order of 23 to 34 indicative of moderately to highly expansive soils (Nelson and Miller, 1992).
All clay soils shall be removed from beneath structural areas unless grading is such that those soils will be covered
by at least 3 feet of structural fill beneath footings and 2 feet beneath slabs and pavements. Aggregate base
course layers may be included as part of the required separation beneath slabs and pavements. The required separation may be achieved by any combination of site filling or over-excavation and replacement. It must be
emphasized that unless clay soils are completely removed from structural areas, some differential movement
should be anticipated. Any over-excavation shall be backfilled with structural fill to footing grade, or subgrade for
pavements and slabs. The width of over-excavation shall extend laterally from the edge of footings, concrete slabs or asphalt pavements at least one-half the depth of the over-excavation.
Discussion and Recommendations
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8 Clays to be left in place and covered with fill shall be moisture-conditioned to 2 to 4 percent over optimum for a
minimum depth of 12 inches. This moisture level will significantly decrease the magnitude of shrink-swell
movements in the upper foot of clay. The high moisture content must be maintained by periodic surface wetting, or other methods, until the surface is covered by at least 1 lift of fill. If allowed to dry out, subsequent expansion of
clay soils beneath foundations and floor slabs could significantly exceed the design criteria set forth previously.
If wet weather construction is anticipated, surface soils may be well above optimum moisture and impossible to
compact. In some situations, moisture conditioning may be possible by scarifying the top 12 inches of subgrade and allowing it to air-dry to near-optimum moisture prior to compaction. Where this procedure is ineffective or
where construction schedules preclude delays, mechanical stabilization will be necessary. Mechanical stabilization
may be achieved by over-excavation and/or placement of an initial 12- to 18-inch-thick lift of 12-inch-minus, 3-
inch-plus, well graded, angular rock fill. The more angular and well graded the rock is, the more effective it will be. This fill shall be densified with large equipment, such as a self-propelled sheeps-foot or a large loader, until no
further deflection is noted. Additional lifts of rock may be necessary to achieve adequate stability. The use of a
separator geotextile will prevent mud from pumping up between the rocks, thereby increasing rock-to-rock contact
and decreasing the required thickness of stabilizing fill. The separator geotextile shall meet or exceed the following minimum properties presented in Table 1 (Minimum Required Properties for Separator Geotextile).
TABLE 1 - MINIMUM REQUIRED PROPERTIES FOR SEPARATOR GEOTEXTILE
Trapezoid Strength (ASTM D 4533) 80 x 80 lbs.
Puncture Strength (ASTM D 4833) 500 lbs.
Grab Tensile Strength/Elongation (ASTM D 4632) 200 x 200 @ 50 %
As an alternate to rock fill, a geotextile/gravel system may be used for stabilization. Aggregate base (Standard
Specifications for Public Works Construction [SSPWC], 2012), Class C or D drain rock (SSPWC, 2012), or pit run
gravels shall be placed above the geotextile. Regardless of which alternate is selected, a test section is recommended to determine the required thickness of stabilization.
Trenching, Excavation and Utility Backfill The on-site surface and near surface soils may generally be excavated with mid- to large-sized earthmoving or excavation equipment. Some native soil horizons are strongly cemented. In addition, moderately indurated
sandstone will be encountered within the cut areas in the northern portion of the building pad. The excavation rate
will be considerably slower within the strongly cemented soil layers and sandstone beds. The use of more
aggressive excavation techniques, such as single-shank rippers or rock breaking equipment, may be needed to achieve proposed grades. Neat line trenching should be possible.
Discussion and Recommendations
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8 Temporary trenches with near-vertical sidewalls should be stable to a depth of approximately 4 feet. Temporary
trenches are defined as those that will be open for less than 24 hours. Excavations to greater depths will require
shoring or laying back of sidewalls to maintain adequate stability. Regulations contained in Part 1926, Subpart P, of Title 29 of the Code of Federal Regulations (CFR, 2010) require that temporary sidewall slopes be no greater than
those presented in Table 2 (Maximum Allowable Temporary Slopes).
TABLE 2 - MAXIMUM ALLOWABLE TEMPORARY SLOPES
Soil or Rock Type Maximum Allowable Slopes1 for Deep Excavations less
than 20 Feet Deep2
Stable Rock Vertical (90 degrees)
Type A3 3H:4V (53 degrees)
Type B 1H:1V (45 degrees)
Type C 3H:2V (34 degrees)
Notes:
1 Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from the horizontal. Angles have been rounded off.
2 Sloping or benching for excavations greater than 20 feet deep shall be designed by a registered professional engineer. 3 A short-term (open 24 hours or less) maximum allowable slope of 1H:2V ([horizontal to vertical] 63 degrees) is allowed in excavation in Type A
soils that are 12 feet or less in depth. Short-term maximum allowable slopes for excavations greater than 12 feet in depth shall be 3H:4V (53 degrees).
The State of Nevada, Department of Industrial Relations, Division of Occupational Safety and Health Administration (OSHA) has adopted and strictly enforces these regulations, including the classification system and the maximum
slopes. In general, Type A soils are cohesive, non-fissured soils with an unconfined compressive strength of 1.5
tons per square foot (tsf) or greater. Type B are cohesive soils with an unconfined compressive strength between
0.5 and 1.5 tsf. Type C soils have an unconfined compressive strength below 0.5 tsf. Numerous additional factors and exclusions are included in the formal definitions. The client, owner, design engineer, and contractor shall refer
to Appendix A and B of Subpart P of the previously referenced Federal Register for complete definitions and
requirements on sloping and benching of trench sidewalls. Appendices C through F of Subpart P apply to
requirements and methodologies for shoring.
On the basis of our exploration, the sandstone, native clay, and alluvial fan soils exhibiting various degrees of
cementation are generally Type B. The sand and gravel soils within the existing drainage are Type C. Any area in
question shall be considered Type C unless specifically examined by the engineer during construction. All
trenching shall be performed and stabilized in accordance with local, state, and OSHA standards.
Discussion and Recommendations
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8
Utility Trench Backfill
The maximum particle size in trench backfill shall be 4 inches. In general, bedding and initial backfill 12 inches
over the pipe will require import and shall conform to the requirements of the utility having jurisdiction. Bedding
and initial backfill shall be densified to at least 90 percent relative compaction. Native granular soil will provide adequate final backfill as long as any oversized particles are excluded, and it shall be placed in maximum 8-inch-
thick loose lifts that are compacted to a minimum of 90 percent relative compaction in all structural areas.
Mass Grading The site will be mass graded cut to fill to create a level building pad. Cut on the order of 35 feet and fill up to 40
feet are anticipated based on the grading plan prepared by Tectonics.
Native clay soils shall be placed as fill only in nonstructural areas. Native granular soils will be suitable for structural
fill provided particles larger than 4 inches are removed. If imported structural fill is required on this project, we recommend it satisfy the specifications presented in Table 3 (Guideline Specification for Imported Structural Fill).
TABLE 3 - GUIDELINE SPECIFICATION FOR IMPORTED STRUCTURAL FILL
Sieve Size Percent by Weight Passing
4 Inch 100
3/4 Inch 70 – 100
No. 40 15 – 70
No. 200 5 – 30
Percent Passing No. 200 Sieve Maximum Liquid Limit Maximum Plastic Index
5 – 10 50 20
11 – 20 40 15
21 – 30 35 10
These recommendations are intended as guidelines to specify a readily available, prequalified material.
Adjustments to the recommended limits can be provided to allow the use of other granular, non-expansive
material. Any such adjustments must be made and approved by the engineer, in writing, prior to importing fill to the site.
Discussion and Recommendations
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8 All fill placed on hillsides steeper than 5H:1V (horizontal to vertical) shall be keyed into existing materials in
equipment-wide benches. The maximum vertical separation between benches shall be 8 feet.
Any structural fill within the building area shall be placed in maximum 8-inch-thick loose lifts, each densified to at least 95 percent relative compaction. All other structural fill shall be densified to a minimum 90 percent relative
compaction.
Grading shall not be performed with or on frozen soils.
Fill Settlement Wedge-shaped deep fill up to approximately 40 feet is anticipated to create a relatively level pad for the building.
All fills consolidate due to their own weight (self-consolidation). Differential settlement across a wedge-shaped fill
of this magnitude could be significant. In general, the granular soils placed as deep fill can consolidate about 0.5 percent of the fill height (about 2.4 inches for 40 feet of fill). The time for the substantial completion of fill
settlement cannot be accurately calculated and will vary depending on the thickness of fill, compactive effort, and
the characteristics of fill material. We expect self-consolidation of fill on this project, clayey sand and gravel soils
from cut areas, can take as long as 60 days from the completion of filling to pad finished grade elevation. Project development shall be planned to delay the construction of footings and structural improvements in deep fill areas
through this period. In addition, a minimum of 3 benchmarks should be set in deep fill areas following mass
grading and surveyed weekly to evaluate the progress of self-consolidation settlement in the fill. The construction
of footings and structural improvements within deep fill areas (areas with fill greater than 10 feet) should not commence until it is confirmed that fill settlement has reached an equilibrium level (no more than 0.02 feet of
settlement in at least 3 consecutive, weekly settlement monitoring records).
Seismic Design Parameters The 2012 IBC (ICC, 2012), adopted by the City of Reno, requires a detailed soils evaluation to a depth of 100
feet to develop appropriate soils criteria. However, the code states that a Site Class D may be used as a default
value when the soil properties are not known in sufficient detail to determine the soil profile type. The Site Class D soil profile is for stiff soils with a shear velocity between 600 and 1,200 feet per second, or with an N (SPT) value
between 15 and 50, or an undrained shear strength between 1,000 and 2,000 pounds per square foot (psf).
Based on our experience and the geology at the project site, it is our opinion that the default Site Class D is
appropriate. With that assumption, the recommended seismic design criteria are presented in Table 4 (Seismic
Design Criteria Using 2012 International Building Code).
Discussion and Recommendations
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8
TABLE 4 - SEISMIC DESIGN CRITERIA USING 2012 INTERNATIONAL BUILDING CODE
Approximate Latitude 39.651
Approximate Longitude -119.869
Spectral Response at Short Periods, Ss, percent of gravity 163.2
Spectral Response at 1-Second Period, S1, percent of gravity 53.1
Site Class D
Risk Category II
Site Coefficient Fa, decimal 1.00
Site Coefficient Fv, decimal 1.50
Site Adjusted Spectral Response at Short Periods, SMS, percent of gravity 163.2
Site Adjusted Spectral Response at Long Periods, SM1, percent of gravity 79.7
Design Spectral Response at Short Periods, SDS, percent of gravity 108.8
Design Spectral Response at Long Periods, SD1, percent of gravity 53.1
Foundation The most economical method of foundation support lies in spread footings bearing on structural fill. Individual
column footings and continuous wall footings underlain by structural fill or granular native soil can be designed for
a net maximum allowable bearing pressure of 3,000 psf and should have minimum footing widths of 24 and 12 inches, respectively. The net allowable bearing pressure is the pressure at the base of the footing in excess of the
adjacent overburden pressure. This allowable bearing value should be used for dead plus ordinary live loads.
Ordinary live loads are that portion of the design live load that will be present during the majority of the life of the
structure. Design live loads are loads that are produced by the use and occupancy of the building, such as by moveable objects, including people or equipment, as well as snow loads. This bearing value may be increased by
one-third for total loads. Total loads are defined as the maximum load imposed by the required combinations of
dead load, design live loads, snow loads, and wind or seismic loads.
With this allowable bearing pressure, total foundation movements of approximately ¾ inch should be anticipated. Differential movement between footings with similar loads, dimensions, and base elevations should not exceed
two-thirds of the values provided above for total movements. The majority of the anticipated movement will occur
during the construction period as loads are applied. This settlement does not include any remaining internal
settlement of deep fill, as discussed in the Fill Settlement section.
Discussion and Recommendations
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8 Lateral loads, such as wind or seismic, may be resisted by passive soil pressure and friction on the bottom of the
footing. The recommended coefficient of base friction is 0.42 and has been reduced by a factor of 1.5 on the
ultimate soil strength. Design values for active and passive equivalent fluid pressures are 35 and 400 psf per foot of depth, respectively. These design values are based on spread footings bearing on and backfilled with structural
fill. All exterior footings should be placed a minimum 2 feet below adjacent finished grade for frost protection.
If loose, soft, wet, or disturbed soils are encountered at the foundation subgrade, these soils should be removed
to expose undisturbed granular soils and the resulting over-excavation backfilled with compacted structural fill. The base of all excavations should be dry and free of loose soils at the time of concrete placement.
Retaining Walls The project will include design and construction of a rockery wall at the top of the proposed 2H:1V cut slope in the northwest corner of the project where space limits the extents of the slope. Additionally, loading docks will be
constructed along the building perimeter. Rockery walls will require a site specific design. Design parameters for
small retaining walls such as dock walls and associated backfill recommendations are provided below.
Dock Wall Design Parameters
Table 5 (Retaining Wall Design Parameters) provides design parameters for small retaining walls, such as dock walls with vertical back faces and horizontal backfill. Surcharge loads, including construction and traffic loads, shall
be added to the following values. While the recommendations here may be suitable for other conditions, the
engineer shall be consulted for larger retaining walls or walls with unusual conditions such as sloping backfill or
sloping back faces.
TABLE 5 - RETAINING WALL DESIGN PARAMETERS
Bearing Pressure 3,000 psf
Coefficient of Friction 0.42
At Rest Equivalent Fluid Pressure 55 pcf*
Active Equivalent Fluid Pressure 35 pcf
Passive Equivalent Fluid Pressure 400 pcf
Unit Weight of Soil 125 pcf
*Pounds per Cubic Foot
Discussion and Recommendations
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8
Retaining Wall/Dock Wall Backfill
Backfill behind retaining walls shall be compacted to 90 percent of the material's maximum dry density in
accordance with ASTM D 1557, but it shall not be densified to more than approximately 92 percent relative
density to minimize pressure against the walls. Care must be exercised when compacting backfill against retaining walls and foundations. To reduce temporary construction loads on the walls, heavy equipment shall not be used
for placing and compacting fill within a region as determined by a 0.5H:1V line drawn upward from the bottom of
the wall, or within 3 feet of the wall, whichever is greater. We recommend that hand-operated compaction
equipment be used to compact soils adjacent to walls.
Subsidence and Shrinkage Subsidence of granular alluvial soils exposed in cut should be negligible. Granular alluvial soils excavated and
recompacted in structural fills should experience quantity shrinkage of approximately 10 percent, including removal of oversized particles. In other words, 1 cubic yard of excavated granular alluvium will generate about 0.9 cubic
yards of structural fill at 95 percent relative compaction.
Slope Stability and Erosion Control Project grading plans indicate significant cut and fill slopes are needed to create a level pad for this project. A
2H:1V cut slope is planned for the northwest corner of the building pad. The cut slope will generally be 20 to 35
feet in height. A 2H:1V fill slope is planned for the southeast corner of the building pad. The fill slope will be up to
approximately 40 feet in height.
Stability of cut and filled surfaces involves 2 separate aspects. The first concerns true slope stability related to mass
wasting, landslides, or the en masse downward movement of soil or rock. Stability of cut and fill slopes is
dependent upon shear strength, unit weight, moisture content, and slope angle. The IBC (ICC, 2012), adopted by the City of Reno, allows cut and fill slopes up to 2H:1V in the type of soils present at this site. The exploration and
testing program conducted during this investigation confirms 2H:1V slopes will be stable.
The second aspect of stability involves erosion potential and is dependent on numerous factors involving grain size
distribution, cohesion, moisture content, slope angle, and the velocity of water or wind on the ground surface. The City of Reno municipal code requires erosion control of cut and fill slopes that are 5H:1V or steeper. Slopes
between 3H:1V and 5H:1V can be stabilized by hydroseeding. Slopes steeper than 3H:1V require mechanical
stabilization. The City of Reno may accept other methods of stabilization on slopes steeper than 3H:1V if they can
be demonstrated to be as effective as mechanical stabilization. Details of the required erosion control are
presented in the Reno Municipal Code Section 18.09.040 and the City of Reno Public Works Design Manual (revised 2009).
Discussion and Recommendations
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8 Dust potential at this site will be high during dry periods. Temporary (during construction) and permanent (after
construction) erosion control will be required for all disturbed areas. The contractor shall prevent dust from being
generated during construction in compliance with all applicable city, county, state, and federal regulations. The contractor shall submit an acceptable dust control plan to the Washoe County District Health Department prior to
starting site preparation or earthwork. Project specifications should include an indemnification by the contractor of
the owner and engineer for any dust generation during the construction period. The owner will be responsible for
mitigation of dust after accepting the project.
In order to minimize erosion and downstream impacts to sedimentation from this site, best management practices
with respect to stormwater discharge shall be implemented.
Site Drainage Adequate surface drainage shall be provided so moisture is directed away from the structure. The ponding of
water on finished grade or at the edge of pavements shall be prevented by grading the site in accordance with IBC
and/or International Residential Code ([IRC] ICC, 2012) requirements.
Geotechnical Considerations for Detention Basins We understand that 2 detention basins will be constructed to temporarily retain stormwater runoff. The side slopes
of the detention basins shall not be steeper than 2H:1V. Where berms are to be built using native soils, they shall be overbuilt and cut back to the design slopes (particularly the basin side slopes) so that the slope face exhibits
compacted material. It should be understood that based on the soil conditions present throughout the site, the
infiltration characteristics of the on-site materials is such that water collected in the detention basins should not be
expected to infiltrate. Accordingly, the designer should anticipate the need for an outflow pipe within the proposed detention basins to drain collected stormwater.
Concrete Slabs All concrete slabs shall be directly underlain by imported Type 2, Class B aggregate base (SSPWC, 2012). The strength of the base material is particularly critical for impact loads (fork lifts) and point loads, such as occur with
storage racks. The thickness of base material beneath PCC flatwork shall be 6 inches beneath curbs and gutters, 4
inches beneath sidewalks, and 6 inches beneath floor slabs and private flatwork. Aggregate base courses shall be
densified to at least 95 percent relative compaction.
Discussion and Recommendations
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8 Final design of the floor slab shall be performed by the project structural engineer. Any interior concrete slab-on-
grade floors shall be a minimum of 4 inches thick. Floor slab reinforcement, as a minimum, shall consist of No. 3
reinforcing steel placed on 24-inch-centers in each direction, or flat sheets of 6x6, W4.0xW4.0 welded wire mesh (WWM). Rolls of WWM are not recommended for use because vertically centered placement of rolled WWM
within a floor slab is difficult to achieve. All reinforcing steel and WWM shall be centered in the floor slab through
the use of concrete dobies or an approved equivalent.
Any interior concrete slab-on-grade floors shall be a minimum of 4 inches thick. Final design of the floor slab (thickness as well as the reinforcement) shall be performed by the structural engineer. A coefficient of subgrade
reaction (K-value) of 200 pounds per cubic inch shall be used for design of concrete slabs.
The structural section for exterior truck ramps, aprons, and dolly pads shall be a minimum of 6 inches of 4,000
pounds per square inch (psi) concrete overlying 6 inches of Type 2, Class B aggregate base (SSPWC, 2012). Valley gutters shall include at least 6 inches of fibermesh concrete (4,000 psi) or thicker if necessary to meet the
City of Reno minimums. These exterior rigid pavements have been designed using the American Association of
State Highway and Transportation Officials (AASHTO, 1993) method for concrete with a 28-day flexural strength of 570 psi (approximately 4,000 psi compressive strength).
The Lemmon Valley area is a region with exceptionally low relative humidity. As a consequence, concrete flatwork
is prone to excessive shrinking and curling. Concrete mix proportions and construction techniques, including the
addition of water and improper curing, can adversely affect the finished quality of concrete and result in cracking, curling, and the spalling of slabs. We recommend that all placement and curing be performed in accordance with
procedures outlined by the American Concrete Institute (ACI, 2008) and this report. Special considerations shall
be given to concrete placed and cured during hot or cold weather temperatures, low humidity conditions, and
windy conditions such as are common in the Lemmon Valley area.
Proper control joints and reinforcement shall be provided to minimize any damage resulting from shrinkage, as
discussed below. In particular, crack-control joints shall be installed on maximum 10-foot-centers and shall be
installed to a minimum depth of 25 percent of the slab thickness. Saw-cuts, zip strips, and/or trowel joints are
acceptable; however, saw-cut joints must be installed as soon as initial set allows and prior to the development of internal stresses that will result in a random crack pattern. If trowel joints are used in the main living area floor slab,
they will need to be grouted over prior to installation of floor coverings.
Concrete shall not be placed on frozen in-place soils.
Discussion and Recommendations
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8 Any interior concrete slab-on-grade floors with moisture sensitive flooring will require a moisture barrier system.
Installation shall conform to the specifications provided for a Class B vapor restraint (ASTM E 1745-97). The vapor
barrier shall consist of placing a 10-mil-thick Stego® Wrap Vapor Barrier or an approved equal directly on a properly prepared subgrade surface. A 4-inch-thick layer of aggregate base shall be placed over the vapor barrier and
compacted with a vibratory plate.
The base layer that overlies the moisture barrier membrane shall remain compacted and a uniform thickness
maintained during the concrete pour, as its intended purpose is to facilitate even curing of the concrete and minimize curling of the slab. Extra attention shall be given during construction to ensure that rebar reinforcement
and equipment do not damage the integrity of the vapor barrier. Care must be taken so that concrete discharge
does not scour the base material from the vapor barrier. This can be accomplished by maintaining the discharge
hose in the concrete and allowing the concrete to flow out over the base layer.
Asphalt Concrete Asphalt Concrete Pavement Design
Paved areas subject to truck traffic shall consist of 4 inches of asphalt concrete underlain by 6 inches of Type 2,
Class B, aggregate base (SSPWC, 2012). Paved areas restricted to automobile parking can consist of 3 inches of asphalt concrete underlain by 6 inches of aggregate base. All aggregate base beneath asphalt pavements shall be
densified to at least 95 percent relative compaction.
Pavement Drainage Design Parameters
Pavement design is mostly a function of heavy truck traffic and subgrade strength. Inherent in the selection of design subgrade strength is the assumption that the subgrade will not become saturated. Subgrade strength drops
dramatically when moisture increases even slightly more than the selected design value. This is essentially true for
any material other than clean sands and gravels and is more critical in fine-grained and clay soils than in granular
soils. Soils at this site are considered to be of moderate moisture sensitivity. Where cut slopes are adjacent to the pavement section, we recommend that edge drains be constructed directly behind the curb. If proper drainage is
not provided, pavement subgrade may experience increases in moisture content which typically results in
increased maintenance costs and premature pavement (subgrade) failure.
The edge drain shall extend at least 12 inches below the street subgrade and can consist of either a narrow trench
backfilled with Class B or C drain rock (SSPWC, 2012) or a synthetic edge drain product. Drain rock shall be
separated from native soil backfill by a geotextile such as Mirafi® 140N or an equal. In cohesionless soils the fabric
shall also be placed on the upslope side, between the native soils and the drain rock/backfill. The edge drain shall
be tied into the storm drain or drain rock backfill around the storm drain. In some cases utility trenches located behind the street could be utilized as edge drains if designed and constructed with that intent.
Discussion and Recommendations
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8
Pavement Maintenance
Asphalt concrete pavements have been designed for a standard 20-year life expectancy as detailed above. Due to
the local climate and available construction aggregates, a 20-year performance life requires diligent maintenance.
Between 15 and 20 years after initial construction (average 17 years), major rehabilitation (structural overlay or reconstruction) is often necessary if maintenance has been lax. To achieve maximum performance life,
maintenance must include regular crack sealing, seal coats, and patching as needed. Crack filling is commonly
necessary every year or at least every other year. Seal coats, typically with a Type II slurry seal, are generally
needed every 3 to 6 years depending on surface wear. Failure to provide thorough maintenance will significantly reduce pavement design life and performance.
Corrosion Potential Metal Pipe Design Parameters
Laboratory testing was performed to evaluate the corrosion potential of the soils with respect to metal pipe in contact with the ground. The results of the laboratory testing indicate that the site foundation soils exhibit low
corrosion potential (American Water Works Association [AWWA], 1999). As a result, metal pipe in contact with the
ground will not require corrosion protection.
Portland Cement Concrete Mix Design Parameters
Soluble sulfate content has been determined for representative samples of the site foundation soils. The sulfate was extracted from the soil at a 10:1 water to soil ratio in order to assure that all soluble sodium sulfate was
dissolved. The results are reported in milligrams of sulfate per kilogram of soil and can be directly converted to
percent by dividing by 10,000. The percent sulfate in the soil is used to determine the sulfate exposure Class (S)
from the information presented in Table 6 (Sulfate Exposure Class).
TABLE 6 - SULFATE EXPOSURE CLASS*
S Sulfate
Water-Soluble Sulfate (SO4) in Soil, Percent by Weight
Not Applicable S0 SO4 < 0.10
Moderate S1 0.10 ≤ SO4 < 0.20
Severe S2 0.20 ≤ SO4 ≤ 2.00
Very Severe S3 SO4 > 2.00
*From Table 4.2.1 Exposure Categories and Classes. ACI 318, Buildings Code and Comments.
The results of the testing (Appendix A) indicate that concrete in contact with the site foundation soils should be
designed for Class S0 Sulfate exposure. Therefore, Type II cement can be used for all concrete work.
Anticipated Construction Problems
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Anticipated Construction Problems Depending on the season of construction, soft, wet surface soils may make it difficult for construction equipment
to travel and operate. Project scheduling should include delaying footing construction within deep fill areas. Some
difficulty will be encountered in trenching due to the cemented nature of the native soils. Careful identification and segregation of clay soils during mass grading will be required.
Quality Control
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10
Quality Control All plans and specifications should be reviewed for conformance with this geotechnical report and approved by the
engineer prior to submitting them to the building department for review.
The recommendations presented in this report are based on the assumption that sufficient field testing and construction review will be provided during all phases of construction. We should review the final plans and
specifications to check for conformance with the intent of our recommendations. Prior to construction, a pre-job
conference should be scheduled to include, but not be limited to, the owner, architect, civil engineer, general
contractor, earthwork and materials subcontractors, building official, and engineer. The conference will allow parties to review the project plans, specifications, and recommendations presented in this report and discuss applicable
material quality and mix design requirements. All quality control reports should be submitted to and reviewed by
the engineer.
During construction, we should have the opportunity to provide sufficient on-site observation of preparation and grading, over-excavation, fill placement, foundation installation, and paving. These observations would allow us to
verify that the geotechnical conditions are as anticipated and that the contractor's work is in conformance with the
approved plans and specifications.
Standard Limitations Clause
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Standard Limitations Clause This report has been prepared in accordance with generally accepted geotechnical practices. The analyses and
recommendations submitted are based on field exploration performed at the locations shown on Plate 1. This
report does not reflect soils variations that may become evident during the construction period, at which time re-evaluation of the recommendations may be necessary. We recommend our firm be retained to perform
construction observation in all phases of the project related to geotechnical factors to ensure compliance with our
recommendations.
It is anticipated that the site will be graded cut to fill. As such, minor deviations from the recommendations and assessments presented in this report are anticipated. Fills are to be generated on site using cut-to-fill methods and
will not be purchased from a commercial borrow source. Therefore, the potential exists for soils within the building
pad to fall outside the material limits recommended in this report. Unless these deviations can be proven to be
fundamental to any observed distress or performance issue, such deviations should not be considered a failure to adhere to the recommendations presented in this report or a design flaw, but should be considered an acceptable
variation in mass grading when on-site materials are used as the fill source. Acceptable performance of such
materials is formulated around the provisions and requirements of the IBC.
This report has been produced to provide information allowing the architect or engineer to design the project. The
owner is responsible for distributing this report to all designers and contractors whose work is affected by
geotechnical aspects. In the event there are changes in the design, location, or ownership of the project from the
time this report is issued, recommendations should be reviewed and possibly modified by the engineer. If the engineer is not granted the opportunity to make this recommended review, he or she can assume no
responsibility for misinterpretation or misapplication of his or her recommendations or their validity in the event
changes have been made in the original design concept without his or her prior review. The engineer makes no
other warranties, either express or implied, as to the professional advice provided under the terms of this agreement and included in this report.
References
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References American Association of State Highway and Transportation Officials (AASHTO), 1993, Design Manual for Design
of Rigid and Flexible Pavements.
American Concrete Institute (ACI), 2008, ACI Manual of Concrete Practice: Parts 1 through 5.
American Society for Testing and Materials (ASTM), 2015, Soil and Rock (I and II), Volumes 4.08 and 4.09.
American Water Works Association (AWWA), 1999, American National Standard for Polyethylene Encasement for Ductile-Iron Pipe Systems, American Water Works Association ANSI/AWWA C105/A21.5-99 (Revision of
ANSI/AWWA C105/A21.9-93).
Bell, J. W., 1984, Quaternary Fault Map of Nevada, Reno Sheet: Nevada Bureau of Mines and Geology (NBMG),
Map 79.
Bonham, H. F. and E. C. Bingler, 1973, Geologic Map, Reno Quadrangle: Nevada Bureau of Mines and Geology,
Map 4Ag.
Bowles, J. E., 1996, 5th ed., Foundation Analysis and Design, McGraw Hill.
Code of Federal Regulations (CFR), 2010, Title 29, Part 1926, Subpart P – Excavations.
Cordy, Gail E., 1985a, Geologic Map, Reno NE Quadrant: Nevada Bureau of Mines and Geology, Map 4Cg.
Cordy, Gail E., 1985b, Reno NE Quadrangle Earthquake Hazards Map, Nevada Bureau of Mines and Geology,
Map 4Ci.
Federal Emergency Management Agency (FEMA), 2009 (March 16, 2009), Flood Insurance Rate Map
32031C2836G, Washoe County, Nevada.
International Code Council (ICC), 2012, International Building Code (IBC).
ICC, 2012, International Residential Code (IRC).
Naval Facilities Engineering Command (NAVFAC), 1986a, Foundations and Earth Structure; Design Manual 7.2.
NAVFAC, 1986b, Soil Mechanics, Design Manual 7.1.
Nelson, John D. and Debora J. Miller, 1992, Expansive Soils: Problems and Practice in Foundation and Pavement
Engineering, John Wiley and Sons, Inc., New York.
Reno, City of, Public Works Department, Public Works Design Manual, 2009.
References
1345 Capital Boulevard, Suite A Tel: 775/359-6600 Fax: 775/359-7766 31
Reno, Nevada 89502-7140 Email: [email protected]
12 Ryall, A. and B. M. Douglas, 1976, Regional Seismicity, Reno Folio: Nevada Bureau of Mines and Geology.
Standard Specifications for Public Works Construction (SSPWC), 2012 (Washoe County, Sparks-Reno, Carson City, Yerington, Nevada).
Tectonics Design Group, 2018, Grading Plan, Military Road SUP, Reno, Nevada, dated January 2.
United States Geological Survey (USGS), 2017a, Online Quaternary Fault and Fold Database of United States,
Google Earth Files at https://earthquake.usgs.gov/hazards/qfaults/ accessed August 2017.
USGS, 2017b, Earthquake Hazards Program Using 2008 US Seismic Hazard Maps. Online at
http://earthquake.usgs.gov/designmaps/us/application.php, accessed August 2017.
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