HomeMy WebLinkAboutSW1180501_Geotech Report_20180712
Geotechnical Engineering
Exploration and Analysis
West Buncombe Volunteer Fire Station No. 2
Riverview Church Road
Asheville, North Carolina Prepared for:
Garner & Brown Architects, PA
1718 East Boulevard
Charlotte, NC 28203 Prepared by: Gentry Geotechnical Engineering, PLLC. Asheville, North Carolina April 6, 2018 Gentry Project Number 18G-0046-01
April 6, 2018
Garner & Brown Architects, PA
1718 East Boulevard
Charlotte, NC 28203
Attn: Mr. Neil F. Brown, AIA, LEED AP
Subject: Geotechnical Engineering Exploration and Analysis
West Buncombe Volunteer Fire Station No. 2
Riverview Church Road
Asheville, North Carolina
Gentry Project No. 18G-0046-01
Gentry NC Engineering License No. P-1170
Dear Mr. Brown:
As requested, Gentry Geotechnical Engineering, PLLC (Gentry) conducted a Geotechnical
Engineering Exploration and Analyses for the proposed project. The accompanying report
describes the services that were conducted for the project and it provides geotechnical-related
findings, conclusions and recommendations that were derived from those services.
We sincerely appreciate the opportunity to provide geotechnical consulting services for the
proposed project. Please contact the undersigned if there are questions concerning the report or
if we may be of further service.
Respectfully submitted,
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Michon T. Sentner, P.E.
Senior Geotechnical Engineer/
Project Manager
NC License #42383
TABLE OF CONTENTS
GEOTECHNICAL ENGINEERING EXPLORATION AND ANALYSES
WEST BUNCOMBE VOLUNTEER FIRE DEPARTMENT
RIVERVIEW CHURCH ROAD
ASHEVILLE, NORTH CAROLINA
GENTRY PROJECT NUMBER 18G-0046-01
Section No. Description Page No. 1.0 SCOPE OF SERVICES .................................................................................................. 1 2.0 SITE DESCRIPTION ....................................................................................................... 1 3.0 PROJECT DESCRIPTION ............................................................................................. 1 4.0 GEOTECHNICAL SUBSURFACE EXPLORATION PROGRAM ............................ 1 5.0 GEOTECHNICAL LABORATORY SERVICES .......................................................... 2 6.0 MATERIAL CONDITIONS .............................................................................................. 2
6.1. Surface Materials ............................................................................................... 2
6.2. Residual Soil ....................................................................................................... 2 7.0 GROUNDWATER CONDITIONS .................................................................................. 3 8.0 CONCLUSIONS AND RECOMMENDATIONS .......................................................... 3
8.1. Seismic Design Considerations ..................................................................... 3
8.2. Building Foundation Recommendations ..................................................... 3
8.3. Floor Slab Recommendations ........................................................................ 5
8.4. Retaining Wall Recommendations ................................................................ 5
8.5. Generalized Site Preparation Recommendations ..................................... 7
8.6. Generalized Construction Considerations .................................................. 8
8.7. Recommended Construction Materials Testing Services ...................... 9
8.8. Basis of Report ................................................................................................... 9
ATTACHMENTS:
Test Boring Location Plan
Records of Subsurface Exploration (8 Pages)
Photographs (1 Page)
Reference Notes for Boring Logs
GEOTECHNICAL ENGINEERING EXPLORATION AND ANALYSES
WEST BUNCOMBE VOLUNTEER FIRE DEPARTMENT
RIVERVIEW CHURCH ROAD
ASHEVILLE, NORTH CAROLINA
GENTRY PROJECT NUMBER 18G-0046-01
1.0 SCOPE OF SERVICES
This report provides the results of the Geotechnical Engineering Exploration and Analyses that
Gentry Geotechnical Engineering, PLLC (“Gentry”) conducted regarding the proposed
development. The Geotechnical Engineering Exploration and Analyses included several
separate, but related, service areas referenced hereafter as the Geotechnical Subsurface
Exploration Program, Geotechnical Laboratory Services and Geotechnical Engineering Services.
The scope of each service area was narrow and limited, as directed by our client and in consideration of the proposed project. The scope of each service area is briefly explained later.
Geotechnical-related recommendations for design and construction of the foundation, ground-
bearing floor slab for the proposed buildings are provided in this report. Site preparation
recommendations are also given; however, those recommendations are only preliminary since
the means and methods of site preparation will largely depend on factors that were unknown when this report was prepared. Those factors include the weather before and during construction,
subsurface conditions that are exposed during construction, and finalized details of the proposed
development.
2.0 SITE DESCRIPTION
The existing site is a relatively level grassy field that slopes down at the southeast side of the
property. Overhead power lines run through the site. The building corners had been marked at
the time or our arrival.
3.0 PROJECT DESCRIPTION
Ms. Christy Brown, PE of McGill Associates provided us with a Preliminary Boring Location Plan
dated November 2017. We understand that the proposed Fire Station will be constructed on
Riverview Church Road near the corner of Gorman Bridge Road. The proposed structure will be
a two-story metal building with a footprint of approximately 100 ft x 120 feet. The final construction
specifications and structural loads are unknown at this time.
4.0 GEOTECHNICAL SUBSURFACE EXPLORATION PROGRAM
The scope of the Geotechnical Subsurface Exploration Program included evaluating the
subsurface conditions by performing 8 soil test borings. The drilling company, Jordan
Environmental, performed the geotechnical test borings at the site on March 22, 2018. The soil
borings were completed using a Track Mounted Diedrich D50 drill rig with a 2 1/4" ID Hollow Stem
Auger. Seven test borings were extended to a depth of 20 feet, and one test boring was extended
to a depth of 50 feet, resulting in a total of 190 lineal feet. The approximate test boring locations
are shown on the attached Test Boring Location Plan.
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Samples were collected from the test borings, at certain depths, using a split-barrel sampler
during Standard Penetration Testing (SPT). Immediately after sampling, select portions of the
SPT samples were transferred from the sampler to zip lock bags that were labeled at the site for
identification. The retained samples were transported to Gentrys’ geotechnical laboratory as part
of the Geotechnical Subsurface Exploration Program.
5.0 GEOTECHNICAL LABORATORY SERVICES
Samples that were retained at the site were classified by a geotechnical engineer using the
descriptive terms and particle-size criteria, and by using the Unified Soil Classification System
(ASTM D 2488-75) as a general guide. The classifications are shown on the Records of
Subsurface Exploration, along with horizontal lines that show supposed depths of material
change. Field-related information pertaining to the test borings is also shown on the Records of
Subsurface Exploration. The natural moisture content and percent fines of select soil samples
was performed to aid in soil classification and estimating engineering properties of the site soils.
The laboratory test results are shown in Table 1 below.
Table 1 - LABORATORY TEST RESULTS
Test Boring No. Depth
(ft)
Percent Finer
than No. 200
Sieve (%)
Moisture
Content (%)
USCS Soil
Classification
B-1 1 – 2.5 62.6 32.4 MS
B-4 3 – 5.5 33.1 21.1 SM
B-8 6 – 7.5 21.4 15.4 SM
6.0 MATERIAL CONDITIONS
Since material sampling at the test borings was discontinuous, it was necessary for Gentry to
suppose conditions between sample intervals. The supposed conditions at the test borings are
briefly discussed in this section and are described in detail on the Records of Subsurface
Exploration. Also, the conclusions and recommendations in this report are based on the
supposed conditions.
6.1. Surface Materials
The surface material consisted of 4 to 5 inches of grass mat and silty, sand topsoil.
6.2. Residual Soil
Loose to very dense, red, tan, reddish brown, brown, gray, moist, micaceous, clayey, silty sand
or sandy silt was encountered to a depth of 20 feet in Test Borings B-1, and B-3 through B-8, and
to a depth of 50 feet in Test Boring B-2. The silty sand and sandy silt encountered was classified
as Residual soils.
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7.0 GROUNDWATER CONDITIONS
No groundwater was encountered at the test boring locations when the Geotechnical Subsurface
Exploration Program was conducted. It should be noted that ground water levels may fluctuate
several feet with seasonal and rainfall variations and with changes in the water level in adjacent
drainage features. Normally, the highest groundwater levels occur in late winter and spring and the
lowest levels occur in late summer and fall.
8.0 CONCLUSIONS AND RECOMMENDATIONS
8.1. Seismic Design Considerations
A soil site class D is recommended for seismic design. By definition, site class is based on the
average properties of subsurface materials to a depth of 100 feet below the ground surface. Since
100-foot test borings were not requested or authorized for the project, it was necessary to estimate
the site class based on the information obtained from the 50 foot deep test boring, subsequent
calculations, presumed area geology, and table 1613.5.2 of the 2012 North Carolina building
code.
8.2. Building Foundation Recommendations
Based on the assumed structural loads and the test boring findings, a foundation designed using
a 3,000 psf maximum, net, allowable soil bearing capacity is recommended for the proposed
structure. Strip footing pads are recommended to be at least 18 inches wide and isolated column
pads are recommended to be at least 24 inches wide for geotechnical considerations, regardless
of the calculated foundation bearing stress. Foundation walls are assumed to be built of
reinforced cast-in-place or reinforced masonry wall system. It is understood that specific
foundation details including footing dimensions, reinforcing, and other parameters will be
constructed per the most recent edition of the North Carolina State Building Code.
It is understood that City of Asheville requires a minimum 18-inch foundation. However, it is our
opinion that foundations have a minimum 24-inch foundation depth for stability and frost action
concerns. Therefore, footings for foundation walls and columns of the proposed structure are
recommended to bear at least 24 inches below the finished ground grade. The foundation analysis
was conducted assuming that the foundations will bear at about 24 inches below the exterior
ground surface. The top of footings must bear at least 5 feet horizontally from a slope face.
This includes footings bearing near the crest of a slope or within the slope itself. This may
result in the footings bearing deeper than the recommended minimum embedment depth to
provide 5 feet horizontally from a slope face.
Foundation excavations are recommended to be dug with a smooth-edge backhoe bucket to
develop a relatively undisturbed bearing grade. A toothed bucket will likely disturb foundation-
bearing soil more than a smooth-edge bucket, thereby making soil at the excavation base more
susceptible to saturation and instability, especially during adverse weather. It is critical that
contractors protect foundation support soil and foundation construction materials (concrete,
reinforcing, etc.). In addition, engineered fill is recommended to be placed and compacted in
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benched excavations along foundation walls immediately after the foundation walls are capable
of supporting lateral pressures from backfill, compaction, and compaction equipment. Earth-
formed footing construction techniques will likely be feasible considering that silty sand to sandy
silt was above the estimated foundation bearing elevations at the test borings.
Foundation Support Soil Requirements
Footing pads are recommended to be directly and entirely supported by suitable-bearing residual
soil. Based on the recommended 3,000 psf bearing capacity, the average corrected N-value
(determined from SPTs and correlated from other in-situ tests) is recommended to be at least 7
based upon a 3,000 psf maximum bearing capacity. Suitable bearing residual soils for foundation
support are anticipated to be available at a depth of 2 feet below the current surface and
elevations.
It is further recommended that the strength characteristics of soil within the entire foundation
influence zone (determined by Gentry during construction) meet or exceed the recommended
values, unless Gentry approves lesser values.
It is recommended that Gentry evaluate foundation support soil using appropriate means and
methods immediately before foundation construction. The purpose of the recommended
evaluation is to confirm that the foundation will be properly supported and confirm that the support
soil is similar to the conditions described on the Records of Subsurface Exploration. In the event
that another firm performs the recommended foundation elevation, Gentry must be notified if the
composition or strength characteristics of foundation support soil differ from those shown on the
Records of Subsurface Exploration.
Soil that is within a foundation influence zone but does not meet the recommended allowable
bearing capacity (described above), or is otherwise unsuitable, is recommended to be replaced.
Unsuitable bearing material could be replaced with engineered fill, such as No. 57 stone. It is
recommended that Gentry provide specific recommendations pertaining to soil over-excavation
and replacement at the time of construction including the need for wrapping the stone in a
geotextile fabric. As an option to soil replacement, strip footings could be stepped or thickened
to extend through unsuitable bearing materials. It is recommended that a structural engineer or
architect should provide specific details of stepped or thickened footings.
Estimated Foundation Settlement
The post-construction total and differential settlements of foundations designed and constructed
based on this report are estimated to be a maximum of about 1 and 1/2 inch, respectively. The
post-construction angular distortion is estimated to be a maximum of about 1/480 across a
distance of 20 feet or more.
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8.3. Floor Slab Recommendations
With proper sub-grade preparation, it is expected that site soil will be suitable for floor slab
support. Engineered fill that is selected, placed, and compacted according to this report could
also support a concrete slab. It is understood that the specific floor slab thickness, reinforcing,
joint details and other parameters will be constructed per the most recent edition of the North
Carolina State Building Code.
A minimum 4-inch-thick base course is recommended to be directly below the floor slab to serve
as a capillary break and help develop uniform support. It is recommended that the base course
consist of free-draining aggregate. It is recommended that Gentry test and approve base course
aggregate before it is placed. Depending on aggregate gradation, a geotextile might need to be
below the base course.
A minimum 10-mil vapor retarder is recommended to be directly below the base course
throughout the entire floor area. If the base course has sharp, angular aggregate, protecting the
retarder with a geotextile (or by other means) is recommended. It is recommended that a
structural engineer or architect specify the vapor retarder location with careful consideration of
concrete curing and the effects of moisture on future flooring materials.
Estimated Floor Slab Settlement
The post-construction total and differential settlements of an isolated floor slab constructed in
accordance with this report are estimated to be a maximum of about ½ and ⅓-inch, respectively.
8.4. Retaining Wall Recommendations
Cast-in-place concrete or concrete masonry unit cantilever retaining walls for the residence
should be designed as "restrained" retaining walls based on "at-rest" earth pressure, plus any
surcharges near the walls as described below, since the walls are expected to be part of the
residence and lateral movement is not acceptable. Cast-in-place concrete or CMU (concrete
masonry unit) cantilever walls that are not attached to the residence and that can accept some
lateral movement may be designed based on “active” earth pressures, plus any surcharges.
Based on the geotechnical test borings and our experience with similar soil conditions, an
allowable bearing pressure of 3,000 pounds per square foot (psf) may be used. Foundation
support soil requirements of the retaining walls should be performed as previously discussed.
The following Table 2 presents the recommended soil related design parameters for the site
retaining walls with a level back slope behind the walls (i.e. β=0 degrees). Gentry should be
contacted if an alternate retaining wall system is used for alternate recommendations or if a
different sloped backfill surface is planned.
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Table 2 – Recommendations for soil properties and lateral earth pressures
Active earth
pressures
At -rest earth
pressures
Passive earth
pressures
Material
Unit
Weight
(pcf)
Friction
Angle, Ф’
(degrees)
fs
Equiv.
fluid
pressure
(pcf)
Ka
Equiv.
fluid
pressure
(pcf)
Ko
Equiv.
fluid
pressure
(pcf)
Kp(1)
On-site
silty
SAND or
sandy
SILT
125
32
0.39
39
0.31
59
0.47
408(1)
3.26
Clean
washed
stone
(No. 57)(2)
100
40
0.5
22
0.22
36
0.36
460 (1)
4.6
(1) The passive earth pressure coefficient should be divided by a safety factor of 2 to limit
the amount of lateral deformation required to mobilize the passive resistance.
(2) In order for this coefficient to be used, the soil wedge within an angle of 45 degrees
from the base of the wall to about 2 feet below the finished exterior grade should be
excavated and replaced with compacted clean washed stone.
The compacted mass unit weight of the backfill soil presented in the previous table should be used
with the earth pressure coefficients to calculate lateral earth pressures. Lateral pressure arising
from surcharge loading should be added to the above soil earth pressures to determine the total
lateral pressures which the walls must resist. In addition, transient loads imposed on the walls by
construction equipment during backfilling should be taken into consideration during design and
construction. Excessively heavy grading equipment should not be allowed within about 5 feet
horizontally of the walls.
Surface water should be rerouted around the walls and not allowed to flow over or pond behind
the walls. In addition, to reduce the potential for the infiltration of surface water in the backfill, the
upper 24 inches of backfill should consist of relatively impervious soils (i.e., clayey or silty soils)
as backfill. This soil should be compacted to a minimum of 95 percent of its standard Proctor
maximum dry density within plus or minus three percentage points of the optimum moisture
content in accordance with ASTM D 698.
We recommend that positive, unblocked gravity drainage be provided from behind the walls. A
perforated, rigid conduit within free draining crushed stone backfill at the base of the wall can be
used to help provide the drainage required. A layer of nonwoven geotextile filter fabric should
wrap entirely around the crushed stone backfill. If drainage is not provided, the walls should be
designed to accommodate hydrostatic pressures that could develop.
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8.5. Generalized Site Preparation Recommendations
This section deals with site preparation including preparation of foundation, floor slab, and
engineered fill areas. The means and methods of site preparation will greatly depend on the
weather conditions before and during construction, the subsurface conditions that are exposed
during earthwork operations, and the finalized details of the proposed development. Therefore,
only generalized site preparation recommendations are given.
Clearing, Grubbing and Stripping
Surface vegetation, topsoil with adverse organic content, and otherwise unsuitable bearing
materials are recommended to be removed from the proposed building footprint and other
structural areas. Clearing, grubbing and stripping should extend at least several feet beyond
proposed development areas, where feasible.
When the geotechnical soil test borings were performed, the topsoil was about 4 to 5 inches thick.
Those topsoil thicknesses could be used on a preliminary basis to estimate topsoil stripping
quantities. However, since topsoil may be thinner or thicker away from the test borings, the actual
stripping quantity may be more or less than estimated. It might be beneficial to stockpile stripped
topsoil on the site for later use in landscape areas.
Proof-Rolling and Fill Placement
After the recommended clearing, grubbing, and stripping, and once the site is cut (lowered) as
needed, the sub-grade is recommended to be proof-rolled with a fully-loaded, tandem-axle dump
truck or other suitable construction equipment to help locate unstable soil based on sub-grade
deflection caused by the wheel loads of the proof-roll equipment. The entire site is recommended
to be proof-rolled and, where feasible, proof-rolling should extend at least several feet beyond
development areas. It is recommended that Gentry observe proof-roll operations and evaluate
the sub-grade stability based on those observations.
Soil that yields excessively or ruts during proof-rolling, or shows other signs of instability, is
recommended to be replaced with engineered fill. As an option to replacement, unsuitable soil
could be scarified to a sufficient depth (likely 6 to 12 inches, or more), moisture-conditioned
(uniformly moistened or dried), and compacted to the required in-place density. Unsuitable soil
could also be modified with hydrated lime or Portland cement, or mechanically stabilized with
coarse aggregate and/or geosynthetics (geogrids, geotextiles, etc.). It is recommended that
Gentry provide specific soil improvement recommendations based on the conditions during
construction.
The site is recommended to be raised, where necessary, to the planned finished grade with engineered fill immediately after the sub-grade is confirmed to be stable and suitable to support
the proposed site improvements. Engineered fill should have a maximum liquid limit of 50,
maximum plasticity index of 25, a maximum fines content of 50 percent, a maximum organic
content of 5 percent and be fee of deleterious or otherwise unsuitable material. Engineered fill is
recommended to be placed in uniform, relatively thin layers (lifts). It is recommended that
engineered fill slopes be placed no steeper than 2H:1V and be properly benched into the existing
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soils. Each layer of engineered fill is recommended to be compacted to at least 95 percent of the
fill material’s maximum dry density within 3 percent of the optimum moisture content as
determined by The Standard Proctor Compaction test (ASTM D698).
Engineered fill that does not meet the density and water content requirements is recommended
to be replaced or scarified to a sufficient depth (likely 6 to 12 inches, or more), moisture-
conditioned, and compacted to the required density. A subsequent lift of fill should only be placed
after Gentry confirms that the previous lift was properly placed and compacted. Sub-grade soil
may need to be recompacted immediately before construction since equipment traffic and
adverse weather may reduce soil stability.
Use of Site Soil as Engineered Fill
Site soil that does not contain adverse organic content, deleterious materials, or fines content
greater than 50 percent, could be used as engineered fill. If construction is during adverse
weather (discussed in the following section), drying site soil will likely not be feasible. In that case,
aggregate fill (or other fill material with a low water-sensitivity) will likely need to be imported to
the site.
Surface Water Management
Control of surface water from paved areas and roof drainage is very important for this site.
Surface water that is directed below the ground surface could cause instability or undermine
footings. All structures should incorporate gutters with downspouts that are connected to a pipe
system that will convey water to storm drains or offsite. Routine maintenance should include
inspecting, cleaning and repairing the gutters, downspouts and other stormwater handling
systems as needed to ensure they remain operable. Inspections and cleanings should be
performed at least annually. If conveyance of surface water into municipal storm drains is not
possible, the surface water should be directed well away from the structure. Surface water should
not be directed below the ground surface.
8.6. Generalized Construction Considerations
Adverse Weather
Site soil is very moisture sensitive and will become unstable when exposed to adverse weather
such as rain, snow, and freezing temperatures. Therefore, it might be necessary to remove or
stabilize the upper 6 to 12 inches (or more) of soil due to adverse weather, which commonly
occurs during late fall, winter, and early spring. At least some over-excavation and/or stabilization of unstable soil should be expected if construction is during or after adverse weather. Based on
the test borings, extensive over-excavation is not expected to be needed if construction is during
and after favorable, dry weather. Because site preparation is weather dependant, bids for site
preparation, and other earthwork activities, are recommended to be based on the time of year
that construction will be conducted.
In an effort to protect soil from adverse weather, the site surface is recommended to be smoothly
graded and contoured during construction to divert surface water away from construction areas.
Foundation construction should begin immediately after suitable support is confirmed.
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Dewatering
Groundwater was not encountered during or at the completion of the test borings. Some
dewatering might be needed during construction due to precipitation or if perched water is
encountered. Water that accumulates in construction areas is recommended to be removed from
excavations and other construction areas, along with unstable soil as soon as possible. Filtered
sump pumps, drawing water from sump pits excavated in the bottom of construction trenches, will
likely be adequate to remove water that collects in shallow excavations. Excavated sump pits
should be fully-lined with a geotextile and filled with open-graded, free-draining aggregate.
Excavation Stability
Excavations through silty sand and sandy silt residual soils should be no steeper than 1H:1V for
short term conditions and no steeper than 1.5H:1V for long term conditions. Excavations may
cave during construction, especially if granular soil is encountered. Excavations are
recommended to be made in accordance with current OSHA excavation and trench safety
standards, and other applicable requirements. Sides of excavations might need to be sloped or
braced to maintain or develop a safe work environment. Temporary shoring must be designed
according to applicable regulatory requirements. Contractors are responsible for excavation
safety.
8.7. Recommended Construction Materials Testing Services
This report was prepared assuming that Gentry will perform Construction Materials Testing
(“CMT”) services during construction of the proposed development. In general, CMT services are recommended (and expected) to at least include observation and testing of: foundation, floor slab,
concrete and other construction materials. It might be necessary for Gentry to provide
supplemental geotechnical recommendations based on the results of CMT services and provided
specific details of the project.
8.8. Basis of Report
This report is based on Gentry proposal No. 17P-194, which is dated December 11, 2017 and
authorized by you on our execution sheet dated March 8, 2018. The actual services for the project
varied somewhat from those described in the proposal because of the conditions that were encountered while performing the services and in consideration of the proposed project.
This report is strictly based on the project description given earlier in this report. Gentry must be
notified if any part of the project description is not accurate so that this report can be amended, if
needed. This report is based on the assumption that the structure will be designed and
constructed according to the building code that governs construction at the site.
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The conclusions and recommendations in this report are based on supposed subsurface
conditions as shown on the Records of Subsurface Exploration. Gentry must be notified if the
subsurface conditions that are encountered during construction of the proposed development
differ from those shown on the Records of Subsurface Exploration because this report will likely need to be revised.
Record of Subsurface Exploration
Boring:B-1
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Southwest corner of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose, red, moist, micaceous, clayey, sandy, SILT (Residual)SS 6
Firm to very firm, red, moist, micaceous, clayey, silty, fine to medium SAND (Residual)5 SS 14
SS 14
10 SS 18
15 SS 25
Firm, brown, tan, moist, micaceous, silty, fine to medium SAND (Residual)20 SS 19
Boring terminated at 20 feet
No groundwater encountered
Cave in at 15 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-2
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Northwest corner of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Firm, red, moist, micaceous, clayey, silty, fine to medium SAND (Residual)SS 12
5 SS 12
SS 18
10 SS 18
15 SS 15
Firm to very firm, brown, tan, moist, micaceous, silty, fine to medium SAND (Residual)
20 SS 16
25 SS 10
30 SS 24
35 SS 28
Dense, brown, moist, micaceous, silty, fine to medium SAND (Residual)
40 SS 39
Very dense, tan, moist, silty, fine to medium SAND (Residual)
45 SS 70
Dense, grey, brown, moist, micaceous, silty, fine to medium SAND (Residual)50 SS 36
Boring terminated at 50 feet
No groundwater encountered
Cave in at 39 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-3
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Center of west side of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose, red, moist, micaceous, clayey, sandy, SILT (Residual)SS 9
Firm, red, moist, micaceous, clayey, silty, fine to medium SAND (Residual)5 SS 11
SS 14
10 SS 13
Very firm, reddish brown, moist, micaceous, silty, fine to medium SAND (Residual)15 SS 22
20 SS 23
Boring terminated at 20 feet
No groundwater encountered
Cave in at 14.5 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-4
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Center of east side of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
4 inches of silty sand topsoil and grass
Loose, red, moist, micaceous, clayey, sandy, SILT (Residual)SS 9
Firm, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND (Residual)5 SS 12
SS 11
10 SS 13
15 SS 16
Firm, brown, white, moist, micaceous, silty, fine to medium SAND (Residual)
20 SS 17
Boring terminated at 20 feet
No groundwater encountered
Cave in at 16 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-5
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Center of south facing wall, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND (Residual)SS 9
5 SS 7
SS 11
10 SS 7
Very firm to dense, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND 15 SS 25
(Residual)
20 SS 38
Boring terminated at 20 feet
No groundwater encountered
Cave in at 14 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-6
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Southeast corner of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND (Residual)SS 8
5 SS 9
SS 9
Firm, dark reddish brown, moist, micaceous, silty, fine to medium SAND (Residual)10 SS 12
15 SS 20
20 SS 16
Boring terminated at 20 feet
No groundwater encountered
Cave in at 15 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-7
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Center of north facing wall, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose, red, moist, clayey, sandy, SILT (Residual)SS 10
Firm, reddish brown, moist, micaceous, silty, fine to medium SAND (Residual)5 SS 14
SS 14
10 SS 13
15 SS 16
Very firm, red, white, moist, micaceous, silty, fine to medium SAND (Residual)20 SS 23
Boring terminated at 20 feet
No groundwater encountered
Cave in at 14.5 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
Record of Subsurface Exploration
Boring:B-8
Project Name:West Buncombe Fire Department, Station 2, Riverview Church Road, Asheville, NC Elevation:2130 ft March 22, 2018
Location:Northeast corner of building, See Boring Location Plan Project No. 18G-0046-01
Driller:Baker Jordan, Jordan Environmental, LLC, Track Mounted Diedrich D50, 2 1/4" ID Hollow Stem Auger ASTM D1586
Description Depth Sample SPT
feet type N-Value
5 inches of silty sand topsoil and grass
Loose to firm, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND (Residual)SS 11
5 SS 9
SS 11
10 SS 9
15 SS 11
Dense, reddish brown, moist, micaceous, clayey, silty, fine to medium SAND (Residual)20 SS 31
Boring terminated at 20 feet
No groundwater encountered
Cave in at 14 feet after augers removed
GENTRY GEOTECHNICAL ENGINEERING, PLLC
Remarks
SS = Split Spoon Sample
load device.
SPT-N Value Consistency
0-4 0-2 Very Soft
5-10 3-4 Soft
11-20 5-8 Firm
21-30 9-15 Stiff
31-50 16-30 Very Stiff
over 50 Very Dense 31-50 Hard
over 50 Very Hard
Major
Component
of Sample
Boulders
Cobbles
Gravel
Sand
Silt/Clay
ST-Shelby Tube Sampler
RC-Rock Core: NX, BX, AX
HSA-Hollow Stem Auger
Sample/Drilling:
Drilling and Sampling Abbreviations:
SS-Split Spoon Sampler
Correlation of Penetration Resistances to Soil Properties:
Gradation Description and Terminology:
2.00-4.00
Unconfined Compressive
Strength Qp tsf
under 0.25
0.25-0.50
0.50-1.00
1.00-2.00
Loose
Firm
Very Firm
Dense
More than 50% retained onto the No. 200 sieve
SPT-N Value Relative Density
Over 12 inches Trace
4.00-8.00
over 8.00
Consistency Cohesive Soils
More than 50% passing the No. 200 seive
Very Loose
Relative Density -Sands, Silts
Size Range
Description of
Minor Components
Percent of
Dry Weight
No. 10 seive to No. 40 sieve
No. 40 seive to No. 200 sieve
Passing No. 200 seive
Coarse
Fine
Coarse
Medium
Fine
12 inches to 3 inches
3 inches to 3/4 inches
3/4 inches to No. 4 sieve
No. 4 sieve to No. 200 sieve
No. 4 sieve to No. 10 sieve
REFERENCE NOTES FOR BORING LOGS
Little
Some
And
1-9
10-19
20-34
35-50
3 inches to No. 4 sieve
In-Situ Tests:
SPT-Standard Penetration Test
PMT-Pressuremeter Test
VS-Vane Shear
DCP-Dynamic Cone Penetrometer
Qp-Estimated Unconfined Compressive
Strength using Pocket Penetrometer
Qu-Estimated Unconfined Compressive
Strength using strain-controlled axial
Proposed West Buncombe Volunteer Fire Department April 6, 2018
Riverview Church Road Gentry Project No. 18G-0046-01
Asheville, North Carolina Page 1
Photo 1 – Site
Photo 2 – Site