SW6210303_Watson Ridge Report Alternate Site 020721_20210329

Scott Cole, NCLSS
312 Copples Road Ext
Asheboro., NC 2 7205
[phone]
Double D Engineering, PLLC
Attn: Mr. Lee Humphrey
150 S. Page Street
Southern Pines, NC 28387
January 21, 2021
Re: Seasonal High -Water Table Identification and Soil Infiltration Rates: Watson Ridge; Harnett County NC Parcel
9557-57-4906
Soil conditions and infiltration rates were evaluated and measured on the above -referenced property within proposed
storm water BMP devices. Work was conducted in accordance with Parts A-2 and C- I of the North Carolina Department
ofEnvironmental 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 a chroma of 2 or less (in Munsell color notation) in mottles or the
horizon matrix. 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 Candor Sand series (CaB), Blaney Loamy Sand series
(BnB) and the Gilead Loamy Sand series (GaA). These soil series consist of deep, well drained soils with varying rates of
permeability. Infiltration rates were measured to determine if soil conditions were suitable for the installation of
ston-nwater infiltration trenches. Infiltration rates were measured using a Johnson Constant Head Permeameter.
Measurements were recorded at varying intervals until equilibrium was reached.
A summary of observations within each proposed Stormwater BMP Device is shown in the tables below.
BMP Device Site #1
SHWT
Munsell Color
Ksat
Ksat
(inches below
Notation
(0-48"; SL/LS)
(48"-72";
ground surface)
SCL/SC)
72" (elevation
2.5Y 8/1
18.15" / hour
.545" / hour
365.5')
2.5Y 7/1
BMIP Device Site #2
SRWT
Munsell Color
Ksat
Ksat
(inches below
Notation
(0-45"; LS)
(45"-56";
ground surface)
SCL/SC)
56" (elevation
2.5Y 8/1
20" / hour
.545" / hour
332')

Scott Cole, NCLSS
312 Copples Road Ext
Ash ehoro, NC 2 7205
[phone]
BMP Device Site #3
SHWT
Munsell Color
Ksat
Ksat
(inches below
Notation
(0-32"; LS)
(32"-72";
ground surface)
SCL/SQ
Depths vary
2.5Y 8/1
18.15" / hour
.545" / hour
between 32"-72"
2.5Y 7/1
bgs.
I
I
I I
Note: BMP site #3 has 18' of elevation change. Expansive clay layer present at depths ranging from 32-72" bgs.
BMP Device Site #3 (Alternate Location)
SHWT
Munsell Color
Ksat
(inches below
Notation
2round surface)
Not Observed
Heavy Gleying
Not measured
within 15' of
within expansive
ground surface.
Clay layer due to
(Evaluation
perched water,
conducted to
elevation 317')
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. --moommaw—
Thank you,
Scott Cole
North Carolina Licensed Soil Scientist
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