SW3160801_Soils/Geotechnical Report_20241021

a Hydrologic Soil Group—Union County,North Carolina
(5745-Soil Report) P1
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Map Scale:1:3,630 if printed on A portrait(8.5"x 11")sheet N
Meters
$ N 0 50 100 200 300 $
Feet
A
0 150 300 600 900
Map projection:Web Mercator Corner coordinates:WGS84 Edge tics:UTM Zone 17N WGS84
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Hydrologic Soil Group—Union County,North Carolina
(5745-Soil Report)
MAP LEGEND MAP INFORMATION
Area of Interest(AOI) p c The soil surveys that comprise your AOI were mapped at
Area of Interest(AOI) 1:24,000.
0 CID
Soils • D Warning:Soil Map may not be valid at this scale.
Soil Rating Polygons
0 A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
n A/D Water Features line placement.The maps do not show the small areas of
Streams and Canals contrasting soils that could have been shown at a more detailed
n B scale.
Transportation
Q B/D
r4-1. Rails Please rely on the bar scale on each map sheet for map
n C measurements.
ti Interstate Highways
n CID US Routes Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
0 D Major Roads Coordinate System: Web Mercator(EPSG:3857)
n Not rated or not available Local Roads
Maps from the Web Soil Survey are based on the Web Mercator
Soil Rating Lines Background projection,which preserves direction and shape but distorts
• • A distance and area.A projection that preserves area,such as the
1111 Aerial Photography Albers equal-area conic projection,should be used if more
• • A/D accurate calculations of distance or area are required.
^r B This product is generated from the USDA-NRCS certified data as
.v B/D of the version date(s)listed below.
• r C Soil Survey Area: Union County, North Carolina
Survey Area Data: Version 24,Sep 13,2023
• • CID
Soil map units are labeled(as space allows)for map scales
• • D 1:50,000 or larger.
• w Not rated or not available Date(s)aerial images were photographed: Apr 15,2022—May
Soil Rating Points 10,2022
p A The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
O A/D imagery displayed on these maps.As a result,some minor
• B shifting of map unit boundaries may be evident.
• B/D
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Hydrologic Soil Group—Union County, North Carolina 5745-Soil Report
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
CeB2 Cecil gravelly sandy clay B 23.0 77.2%
loam,2 to 8 percent
slopes, moderately
eroded
CeC2 Cecil gravelly sandy clay B 6.8 22.8%
loam,8 to 15 percent
slopes, moderately
eroded
Totals for Area of Interest 29.8 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential)when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential)when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (ND, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
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Hydrologic Soil Group—Union County, North Carolina 5745-Soil Report
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.None Specified
Tie-break Rule: Higher
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Engineering Properties---Union County,North Carolina 5745-Soil Report
Engineering Properties
This table gives the engineering classifications and the range of engineering
properties for the layers of each soil in the survey area.
Hydrologic soil group is a group of soils having similar runoff potential under
similar storm and cover conditions. The criteria for determining Hydrologic soil
group is found in the National Engineering Handbook, Chapter 7 issued May
2007(http://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?
content=17757.wba). Listing HSGs by soil map unit component and not by soil
series is a new concept for the engineers. Past engineering references contained
lists of HSGs by soil series. Soil series are continually being defined and
redefined, and the list of soil series names changes so frequently as to make the
task of maintaining a single national list virtually impossible. Therefore, the
criteria is now used to calculate the HSG using the component soil properties
and no such national series lists will be maintained. All such references are
obsolete and their use should be discontinued. Soil properties that influence
runoff potential are those that influence the minimum rate of infiltration for a bare
soil after prolonged wetting and when not frozen. These properties are depth to a
seasonal high water table, saturated hydraulic conductivity after prolonged
wetting, and depth to a layer with a very slow water transmission rate. Changes
in soil properties caused by land management or climate changes also cause the
hydrologic soil group to change. The influence of ground cover is treated
independently. There are four hydrologic soil groups, A, B, C, and D, and three
dual groups, A/D, B/D, and C/D. In the dual groups, the first letter is for drained
areas and the second letter is for undrained areas.
The four hydrologic soil groups are described in the following paragraphs:
Group A. Soils having a high infiltration rate (low runoff potential)when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential)when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
Depth to the upper and lower boundaries of each layer is indicated.
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Engineering Properties---Union County,North Carolina 5745-Soil Report
Texture is given in the standard terms used by the U.S. Department of
Agriculture. These terms are defined according to percentages of sand, silt, and
clay in the fraction of the soil that is less than 2 millimeters in diameter. "Loam,"
for example, is soil that is 7 to 27 percent clay, 28 to 50 percent silt, and less than
52 percent sand. If the content of particles coarser than sand is 15 percent or
more, an appropriate modifier is added, for example, "gravelly."
Classification of the soils is determined according to the Unified soil classification
system (ASTM, 2005) and the system adopted by the American Association of
State Highway and Transportation Officials (AASHTO, 2004).
The Unified system classifies soils according to properties that affect their use as
construction material. Soils are classified according to particle-size distribution of
the fraction less than 3 inches in diameter and according to plasticity index, liquid
limit, and organic matter content. Sandy and gravelly soils are identified as GW,
GP, GM, GC, SW, SP, SM, and SC; silty and clayey soils as ML, CL, OL, MH,
CH, and OH; and highly organic soils as PT. Soils exhibiting engineering
properties of two groups can have a dual classification, for example, CL-ML.
The AASHTO system classifies soils according to those properties that affect
roadway construction and maintenance. In this system, the fraction of a mineral
soil that is less than 3 inches in diameter is classified in one of seven groups
from A-1 through A-7 on the basis of particle-size distribution, liquid limit, and
plasticity index. Soils in group A-1 are coarse grained and low in content of fines
(silt and clay). At the other extreme, soils in group A-7 are fine grained. Highly
organic soils are classified in group A-8 on the basis of visual inspection.
If laboratory data are available, the A-1, A-2, and A-7 groups are further
classified as A-1-a, A-1-b, A-2-4, A-2-5, A-2-6, A-2-7, A-7-5, or A-7-6. As an
additional refinement, the suitability of a soil as subgrade material can be
indicated by a group index number. Group index numbers range from 0 for the
best subgrade material to 20 or higher for the poorest.
Percentage of rock fragments larger than 10 inches in diameter and 3 to 10
inches in diameter are indicated as a percentage of the total soil on a dry-weight
basis. The percentages are estimates determined mainly by converting volume
percentage in the field to weight percentage. Three values are provided to
identify the expected Low (L), Representative Value (R), and High (H).
Percentage (of soil particles)passing designated sieves is the percentage of the
soil fraction less than 3 inches in diameter based on an ovendry weight. The
sieves, numbers 4, 10, 40, and 200 (USA Standard Series), have openings of
4.76, 2.00, 0.420, and 0.074 millimeters, respectively. Estimates are based on
laboratory tests of soils sampled in the survey area and in nearby areas and on
estimates made in the field. Three values are provided to identify the expected
Low(L), Representative Value (R), and High (H).
Liquid limit and plasticity index(Atterberg limits) indicate the plasticity
characteristics of a soil. The estimates are based on test data from the survey
area or from nearby areas and on field examination. Three values are provided to
identify the expected Low (L), Representative Value (R), and High (H).
References:
American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of
sampling and testing. 24th edition.
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Engineering Properties---Union County,North Carolina 5745-Soil Report
American Society for Testing and Materials (ASTM). 2005. Standard
classification of soils for engineering purposes. ASTM Standard D2487-00.
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Engineering Properties---Union County,North Carolina 5745-Soil Report
Report—Engineering Properties
Absence of an entry indicates that the data were not estimated. The asterisk'*' denotes the representative texture; other
possible textures follow the dash. The criteria for determining the hydrologic soil group for individual soil components is
found in the National Engineering Handbook, Chapter 7 issued May 2007(http://directives.sc.egov.usda.gov/
OpenNonWebContent.aspx?content=17757.wba). Three values are provided to identify the expected Low (L),
Representative Value (R), and High (H).
Engineering Properties—Union County,North Carolina
Map unit symbol and Pct.of Hydrolo Depth USDA texture Classification Pct Fragments Percentage passing sieve number— Liquid Plasticit
soil name map gic limit y index
unit group Unified AASHTO >10 3-10 4 10 40 200
inches inches
In L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H
CeB2—Cecil gravelly
sandy clay loam,2
to 8 percent slopes,
moderately eroded
Cecil,moderately 85 B 0-6 Gravelly sandy clay SC,SC- A-2-4, 0-0-0 0-4-7 72-82- 44-66- 35-58- 19-34- 20-30 5-10-15
eroded loam SM A-4,A-6 95 95 90 56 -40
6-40 Sandy clay,clay, MH,ML A-5,A-7-5 0-0-0 0-3-5 96-98-1 89-94-1 65-85-1 46-65- 38-61 9-23-37
clay loam 00 00 00 87 -80
40-55 Clay loam,sandy CL,ML, A-4,A-6 0-0-0 0-0-1 93-96-1 82-91-1 65-81- 44-58- 20-28 3-10-17
clay loam,loam SC,SM 00 00 94 68 -40
55-80 Sandy loam,fine SC-SM, A-2-4,A-4 0-1-1 0-1-1 88-94-1 70-85-1 49-65- 22-33- 7-15-30 NP-4-7
sandy loam,loam, SM 00 00 84 46
gravelly sandy
loam
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Engineering Properties---Union County,North Carolina 5745-Soil Report
Engineering Properties—Union County,North Carolina
Map unit symbol and Pct.of Hydrolo Depth USDA texture Classification Pct Fragments Percentage passing sieve number— Liquid Plasticit
soil name map gic limit y index
unit group Unified AASHTO >10 3-10 4 10 40 200
inches inches
In L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H
CeC2—Cecil gravelly
sandy clay loam,8
to 15 percent
slopes,moderately
eroded
Cecil,moderately 80 B 0-6 Gravelly sandy clay SC,SC- A-2-4, 0-0-0 0-4-7 72-82- 44-66- 35-58- 19-34- 20-30 5-10-15
eroded loam SM A-4,A-6 95 95 90 56 -40
6-40 Sandy clay,clay, MH,ML A-5,A-7-5 0-0-0 0-3-5 96-98-1 89-94-1 65-85-1 46-65- 38-61 9-23-37
clay loam 00 00 00 87 -80
40-55 Clay loam,sandy CL,ML, A-4,A-6 0-0-0 0-0-1 93-96-1 82-91-1 65-81- 44-58- 20-28 3-10-17
clay loam,loam SC,SM 00 00 94 68 -40
55-80 Sandy loam,fine SC-SM, A-2-4,A-4 0-1-1 0-1-1 88-94-1 70-85-1 49-65- 22-33- 7-15-30 NP-4-7
sandy loam,loam, SM 00 00 84 46
gravelly sandy
loam
Data Source Information
Soil Survey Area: Union County, North Carolina
Survey Area Data: Version 24, Sep 13, 2023
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