SW6230502_Soils/Geotechnical Report_20230605

Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 27205
[phone]
Double D Engineering, PLLC
Attn: Mr. Lee Humphrey
150 S. Page Street
Southern Pines, NC 28387
November 4, 2022
Re: Seasonal High -Water Table Identification and Soil Infiltration Rates: Ducks Landing, Darroch Road,
Lillington; Harnett County NC parcel 010527 0012
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-1 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 W".0
Soils evaluated on this property are typical of those within 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 re orted for each Proposed
location in the tables below.
RMP nevire gitP is
Test Location
SHWT
Munsell Color
Ksat #1
Ksat 42
Ksat #3
(feet below
Notation
round surface
BMP Site 1
Not Observed
N/A
0-2'
Sandy Loam
24'
Sandy Clay
4-12'
Clay/Sap with
Elevation 208'
within 12' of
10" / hour
Loam
wetness
(lowest point)
surface
5" / hour
Not Measured

Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 27205
[phone]
BMP Device Site 02
Test Location
SHWT
feet below
Munsell Color
Notation
Ksat #1
Ksat #2
Ksat #3
round surface
0-4'
4-10'
10-12'
BMP Site 2
Not Observed
N/A
Sandy Loam /
Saprolite with
Saprolite
Elevation 196'
within 12' of
Sandy Clay
wetness
Not Measured
(lowest point)
surface
Loam
Not Measured
8" /hour
BMP Device Site #';
Test Location
SHWT
Munsell Color
Ksat #1
Ksat 92
Ksat #3
(feet below
Notation
round surface
0-4'
4-8'
8-12'
BMP Site 3
Not Observed
N/A
Sandy Loam /
Saprolite with
Saprolite
Elevation 192'
within 12' of
Sandy Clay
wetness
Not Measured
(lowest point)
surface
Loam
Not Measured
8" / hour
RMP Device Cite #d
Test Location
SHWT
Munsell Color
Ksat 91
Ksat #2
Ksat #3
feet below
Notation
round surface
0-3'
3-5'
8-12'
BMP Site 4
Not Observed
N/A
Sandy Loam
Sandy Clay
Saprolite
Elevation 188'
within 10' of
10" / hour
Loam / Sandy
Not Measured
(lowest point)
surface
Clay
2" /hour
RMP Device Cite #S
Test Location
SHWT
Munsell Color
Ksat #1
Ksat #2
Ksat #3
feet below
Notation
round surface
0-2'
2-5'
5-12'
BMP Site 5
Not Observed
N/A
Sandy Loam
Sandy Clay
SCL/Sap with
Elevation 192'
within 12' of
10" / hour
Loam
wetness
lowestpoint)
surface
5" / hour
Not Measured

Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 27205
[phone]
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 of these 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.

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