SW4240402_Soils/Geotechnical Report_20240809

SOLID ROCK ENGINEERING, PLLC
NCBELS #P-1523
W W W.SOLIDROCKENGINEERINGNC.COM
JEFFREY D.HOLCHIN,P.E. FOUNDER,OWNER,&PRINCIPAL ENGINEER
August 9, 2024
Mr. Greg Gotsch, PLA
Director of Planning and Design
Land Resource Management
[e-mail]
Re: Report of Engineering Evaluation of slopes steeper than 3H:1V
The Wilderness Reserve Phase 2 project on Wildcat Rd
Deep Gap,North Carolina
SRE Project#24-LRM-3
Dear Mr. Gotsch:
Solid Rock Engineering, PLLC (SRE) is pleased to provide this report of engineering
evaluation of the existing slopes steeper than 3H:1 V at the Wilderness Reserve Phase 2
project in Deep Gap, North Carolina. SRE was also asked to view the exposed soils in
the site swales and ditches and estimate an allowable shear stress for the site soils. The
following sections of this report provide a brief project description, findings from the site
visit for slope examination on August 2, 2024, and our conclusions and engineering
recommendations for the project. Note that SRE has had no prior involvement with this
project, including any involvement with a geotechnical assessment of the site, design of
the cut and fill slopes nor the actual construction of the slopes for this project. SRE was
hired now to examine the cut and fill slopes steeper than 3H:1V and provide a
professional engineering opinion on their current condition and stability status.
GENERAL PROJECT DESCRIPTION
The attached site plans that you provided show the project with the required cut and fill
slopes. Due to the variable topography at the project, it was not practical to use 3H:1V
slopes, so steeper slopes in the 2H:1 V range were built instead.
SRE FIELD WORK
On August 2, 2024, SRE visited the project and carefully examined all the Phase 2 cut
and fill slopes along the road system. SRE visually examined each slope, checked the
soils and bedrock for composition and used a steel T-handled probe rod to measure the
soil density by penetration. Some of the slopes had only exposed soil, while other slopes
had both soil and rocks exposed on the surface. All of the slopes had a grass cover. SRE
found no evidence that the slopes steeper than 3H:1V have experienced any erosion or
stability problems; the density of the natural soils in the cut slopes and the fill soils in the
fill slopes was adequate for good long-term stability and resistance to erosion in all cases,
on this date. The following photos were taken that day:
1 Solid Rock Engineering,PLLC 577 George Wilson Rd.,Suite 5,Boone NC 28607 828-303-6120

Engineering Evaluation of Slopes Steeper than 3H:1 V
The Wilderness Reserve Phase 2 project in Deep Gap,NC
SRE Project#24-LRM-3
Page 2
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Solid Rock Engineering, PLLC 577 George Wilson Rd., Suite 5, Boone NC 28607 828-303-6120

Engineering Evaluation of Slopes Steeper than 3H:1 V
The Wilderness Reserve Phase 2 project in Deep Gap,NC
SRE Project#24-LRM-3
Page 3
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SRE also examined the exposed soils in the swales and ditches along the road system,
and found that the typical soil is a sandy non-plastic silt with no to some mica and gravel
(ML or silt with low plasticity using the Unified Soil Classification System). SRE
experience indicates that this soil can typically withstand up to 2 psf shear stress during
rain events in an unprotected condition;no lab testing was performed to verify this value.
SRE CONCLUSIONS AND ENGINEERING RECOMMENDATIONS
Based on site reconnaissance, careful examination of the exposed materials in the site
slopes, and SRE experience with similar earthwork projects in the area, SRE concludes
that the site slopes steeper than 3H:1 V are currently stable and free of excessive erosion
or instability. SRE does recommend the addition of diversion ditches at the tops of all
cut slopes, to minimize the surface flow of rainwater on the cut slopes during storm
events.
Thank you for hiring SRE to provide professional engineering services for this project.
Let us know if there are any questions about this report, or if SRE can provide additional
engineering services for the project.
Solid Rock Engineering,PLLC 577 George Wilson Rd.. Suite 5, Boone NC 28607 828-303-6120

Engineering Evaluation of Slopes Steeper than 3H:1 V
The Wilderness Reserve Phase 2 project in Deep Gap,NC
SRE Project#24-LRM-3
Page 4
Sincerely,
SOLID ROCK ENGINEERING,PLLC
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Jeffre D. lchin, P.E., D.GE
Principal Geotechnical Engineer
Attachment: Site Plans for the Wilderness Reserve project showing the planned slopes
Solid Rock Engineering, PLLC 577 George Wilson Rd., Suite 5,Boone NC 28607 828-303-6120

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