HomeMy WebLinkAboutSW6221008_Soils/Geotechnical Report_20221027Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 27205
(336) 460-4554
Double D Engineering, PLLC
Attn: Mr. Lee Humphrey
150 S. Page Street
Southern Pines, NC 28387
April 29, 2022
Re: Seasonal High -Water Table Identification and Soil Infiltration Rates: "Stone Creek" Philippi Church
Road, Raeford, NC; Hoke County NC parcel 494540001006
Soil conditions and infiltration rates were evaluated and measured on the above -referenced property within
the proposed storm water BMP device. Work was conducted in accordance with Parts A-2 and C-I of the
North Carolina Department of Environmental Quality Stormwater Design Manual. Soil samples were
evaluated with a hand auger.
SEASONAL HIGH WATER TABLE IDENTIFICATION
Seasonal High Water Table depth is determined by field evaluation for soil wetness conditions which are
indicated by the presence of redoximorphic (redox) features with chroma colors of 2 or less (in Munsell
color notation) in mottles or the horizon matrix, and at times, saturated soil conditions and/or free water
within the soil profile. Colors of chroma 2 or less due to relic minerals from parent material (underlying
rock), anaerobic activity created by placement of fill material, or soil textural class transitions (perched
water) are not considered as indicators for seasonal high water. Upon determination of SHWT depth, an
additional 6" will be deducted from the observed depth to account for capillary fringe water movement
above the SHWT. Stormwater infiltration trenches are designed to ensure the lowest point is at least two
feet above the Seasonal High Water Table (SHWT).
SATURATED HYDRAULIC CONDUCTIVITY (K,,t)
Soils evaluated on this property are typical of those within the Blaney Soil series. These soils are
moderately well drained soils with varying rates of permeability. Infiltration rates are measured to
determine if soil conditions are suitable for the installation of stormwater infiltration devices. Infiltration
rates are measured using a Johnson Constant Head Permeameter. Measurements are recorded at varying
intervals until equilibrium was reached.
The SHWT and Infiltration rates for the stormwater BMP devices are reuorted in the table below.
BMP Device Site
Test Location
SHWT
Munsell Color
Ksat #1
Ksat #2
Ksat #3
(feet below
Notation
round surface
15' bgs
5Y 8/1
0-4'
4'-5'
5'-20'
BMP Site l
2.5Y 7/1
Loamy Sand /
Sandy Clay
Mixed soils
Elevation 173'
Sandy Loam
Loam
with drainage
12" / hour
5" / hour
mottles (Ksat
value not
measured
Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 27205
(336) 460-4554
CONCLUSION
Field evaluation of hydraulic conductivity provides estimations of soil infiltration rates; however, methods
used to measure these rates can influence the results. Side walls of the bore hole are "smeared" by the soil
auger as the hole is prepared and loose soil in the bottom of the hole is placed in suspension when water is
applied; both factors negatively influence water infiltration rates. To help overcome these issues, after
excavation of each infiltration trench, it is recommended the trench bottom and sidewalls be raked and
dusted with pulverized limestone. These are practices that have been in place within the on -site wastewater
industry to help loosen the soil and aid in restoration of soil structure.
I am pleased to be of service in this matter and can be contacted at your convenience should you have any
questions concerning information within this report.
Thank you,
Scott Cole
North Carolina Licensed Soil Scientist
-
NOTE.
RDII OF BEAVER CREEK IS FII`E PROPER LIME.
BEARINGANO OISTAtJC SH G4YN TAKING FROM AERIAL
PHOTO.
HEREO �.�Jt;
fJGODEOAREAT
110 FIELD SO RVEYWADE THIS DATE
REI:, AIfI NATURAL
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USAC WE TL.':'i2
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768
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Proposed Stormwater BMP
PROPOSED 2
,.aSER
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SHWT Elevation: 173'
o
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sat 0 S S
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Ksat 5'-20' mixed soils with drainage mottles:
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ORM WATER TREATMENT
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