HomeMy WebLinkAboutSDP199900141 Assessment - Environmental Minor Amendment 1999-10-27 USDA Natural Resources Conservation Service October 25, 1999
695 Berkmar Court - Ste 2
Charlottesville, VA 22901
TO: Margaret Pickart
Planning Department
RE: Soils Report for:
Pegasus
OCI 2,1
�g99
PLANNING AND
C
OMMUNt 0 VELOPMENT
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NONTECHNICAL SOILS DESCRIPTION REPORT
Pegasus
Map ( Soil name and description
Symbol
79B Starr silt loam, 2 to 7 percent slopes
This deep, gently sloping, well drained soil is on foot
slopes, in depressions, and along small drainageways.
permeability is moderate, and available water capacity
is high. Surface runoff is medium. The hazard of
erosion is moderate. This soil has good tilth. The
surface layer is friable and easily tilled through a
wide range of soil moisture. The subsoil has moderate
shrink-swell potential. The root zone extends to a
depth of 50 inches or more. The organic matter content
is low, and the natural fertility is medium. This soil
commonly is strongly acid to slightly acid throughout,
but reaction in the surface lyaer is variable because
of local liming. The depth to bedrock is generally more
than 6 feet.
12C catoctin silt loam, 7 to 15 percent slopes
Catoctin is moderately deep and well drained.
Permeability is moderately rapid, and available water
capacity is very low. Surface runoff is rapid. The
hazard of erosion is severe to very severe. This soil
has good tilth. The subsoil has low shrink-swell
potential. The root zone is 20 to 30 inches thick. The
organic matter content is low to moderate, and the
natural fertility is medium.This soil is commonly
strongly acid to slightly acid, unless limed. Depth to
bedrock is 20 to 40 inches.
23C davidson clay loam, 7 to 15 percent slopes
Davidson soils are deep and well drained. Permeability
and available water capacity are moderate. Surface
runoff and erosion hazard very with slope from moderate
to severe. This soil has fair tilth. The subsoil has
low shrink-swell potential. The root zone extends to a
depth of 60 iches. The organic matter content is
moderate, and the natural fertility is medium. This
soil commonly is medium acid to strongly acid
throughout, but reaction in the surface layer is
variable because of local liming. Bedrock is generally
at a depth of more than 5 feet.
71D rabun clay loam, 15 to 25 percent slopes
NONTECHNICAL SOILS DESCRIPTION REPORT
Pegasus
Map I Soil name and description
Symbol
Rabun soils are deep and well drained. Permeability and
available water capacity are moderate. The subsoil has
low shrink-swell potential. The root zone extends to a
depth of 40 inches or more. The organic matter content
is moderate, and the natural fertility is medium. This
soil commonly is slightly acid to strongly acid
throughout, but reaction in the surface layer is
variable because of local liming. Bedrock is generally
at a depth of more than 60 inches.
88 udorthents, loamy
This map unit is made up of areas that have been used
for cutting or filling during grading for roads,
housing development, recreational areas, quarries, and
other similar uses. Permeability ranges from moderately
rapid to slow. The available water capacity is low to
moderate. Surface runoff is medium to very rapid, and
the hazard of erosion is moderate to very severe. The
organic matter content and the natural fertility are
low. These soils are medium acid to very strongly acid
throughtout. Water stands in some areas during winter
and spring, or throughout the year.
23B I davidson clay loam, 2 to 7 percent slopes
Davidson soils are deep and well drained. Permeability
and available water capacity are moderate. Surface
runoff and erosion hazard very with slope from moderate
to severe. This soil has fair tilth. The subsoil has
low shrink-swell potential. The root zone extends to a
depth of 60 iches. The organic matter content is
moderate, and the natural fertility is medium. This
soil commonly is medium acid to strongly acid
throughout, but reaction in the surface layer is
variable because of local liming. Bedrock is generally
at a depth of more than 5 feet.
U.S. DEPARTMENT OF AGRICULTURE PAGE 1 OF 4
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
PHYSICAL PROPERTIES OF SOILS
Pegasus
(Entries under "Erosion factors--T" apply to the entire profile. Entries under "Wind erodibility group" and
"Wind erodability index" apply only to the surface layer)
1 I I I I I 'Erosion factorslWind 'Wind
Map symbol I Depth I Clay I Moist I Permea- !Available! Shrink- 'Organic! lerodi-lerodi-
and soil name I I 1 bulk 1 bility 1 water 1 swell l matter! l Ibilitylbility
1 l I density I 'capacity 'potential! l K I Kt T 'group 'index
I I 1 1 I 1
In l Pct l g/cc I In/hr I In/in I ! Pct I I ! I !
I I I I I 1 I I I I I I
79B: I I I I I 1 I I I I I I
STARR I 0-18 15-3511.20-1.501 0.60-2.00 10.14-0.18IModerate I0.5-2.01 0.281 0.281 5 l 6 l ---
1 18-68 18-3511.20-1.501 0.60-2.00 I0.14-0.18IModerate I --- 10.281 0.281 I I
68-72 ! 10-3511.30-1.501 0.60-2.00 10.10-0.151L0w I --- 10.281 0.281 I I
I I 1 1 1 I I 1 I I I
12C: I I 1 1 1 1 I I 1 1 I I
CATOCTIN 0-5 5-2011.20-1.501 2.00-6.00 10.14-0.201Low 10.5-2.01 0.321 0.321 2 1 5 l ---
5-18 1 10-3511.20-1.501 2.00-6.00 I0.08-0.16ILow I --- 1 0.171 0.241 I I
1 18-28 l 10-2511.20-1.501 2.00-6.00 10.04-0.151L0w I --- 10.171 0.281 I I
128-32 1 --- I --- 1 0.00-0.06 1 --- I I --- 1 --- 1 --- I I I
I I I 1 1 1 I I 1 1 I I
23C: I I 1 1 1 1 I I 1 1 I I
DAVIDSON I 0-4 ! 20-3511.30-1.551 0.60-2.00 I0.14-0.18ILow 10.5-2.0! 0.281 0.281 5 I 6 I ---
1 4-10 127-4011.20-1.501 0.60-2.00 I0.15-0.18ILow I --- 10.321 0.321 I I
l 10-63 140-7511.20-1.501 0.60-2.00 10.12-0.161L0w I --- 10.241 0.241 I I
163-88 25-6011.20-1.501 0.60-2.00 10.12-0.181L0w I --- 10.281 0.281 I I
I 1 1 1 1 I I 1 1 I I
71D: I I 1 1 1 1 I I 1 1 I I
RABUN I 0-6 18-3511.30-1.551 0.60-2.00 10.12-0.181Low 11.0-2.0! 0.321 0.321 4 I 6 I ---
6-48 35-8011.20-1.501 0.60-2.00 10.12-0.181L0w l --- 10.281 0.281 I
48-63 27-5011.20-1.501 0.60-2.00 10.10-0.151Low --- 10.281 0.281 I
63-67 --- I --- I --- I --- I I --- I --- I --- I I I
I I I I I I I I I I I I
88: I I I I I I I I
UDORTHENTS. I I I I ! ! I I I I
I I I I I I I I I I I I
23B: I I I I I I I I I I
DAVIDSON 10-4 1 20-3511.30-1.551 0.60-2.00 10.14-0.181L0w 10.5-2.01 0.281 0.281 5 1 6 I ---
1 4-10 27-4011.20-1.501 0.60-2.00 10.15-0.181L0w I --- 10.321 0.321 I I
110-63 40-7511.20-1.501 0.60-2.00 10.12-0.161Low I --- 10.241 0.241 I I
63-88 25-6011.20-1.501 0.60-2.00 10.12-0.181Low I --- 10.281 0.281 I I
I 1 1 1 1 I I 1 1_I 1
U.S. DEPARTMENT OF AGRICULTURE PAGE 2 OF 4
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
PHYSICAL PROPERTIES OF SOILS
Endnote -- PHYSICAL PROPERTIES OF SOILS
This report shows estimates of some characteristics and features that affect soil behavior. These estimates
are given for the major layers of each soil in the survey area. The estimates are based on field observations
and on test data for these and similar soils.
CLAY as a soil separate consists of mineral soil particles that are less than 0.002 millimeter in diameter.
In this report, the estimated clay content of each major soil layer is given as a percentage, by weight, of the
soil material that is less than 2 millimeters in diameter. The amount and kind of clay greatly affect the
fertility and physical condition of the soil. They determine the ability of the soil to adsorb cations and
to retain moisture. They influence shrink-swell potential, permeability, plasticity, the ease of soil
dispersion, and other soil properties. The amount and kind of clay in a soil also affect tillage and
earthmoving operations.
MOIST BULK DENSITY is the weight of soil (ovendry) per unit volume. Volume is measured when the soil is
at field moisture capacity, the moisture content at 1/3 bar moisture tension. Weight is determined after
drying the soil at 105 degrees C. In this report, the estimated moist bulk density of each major soil
horizon is expressed in grams per cubic centimeter of soil material that is less than 2 millimeters in
diameter. Bulk density data are used to compute shrink-swell potential, available water capacity, total
pore space, and other soil properties. The moist bulk density of a soil indicates the pore space available for
water and roots. A bulk density of more than 1.6 can restrict water storage and root penetration. Moist
bulk density is influenced by texture, kind of clay, content of organic matter, and soil structure.
PERMEABILITY refers to the ability of a soil to transmit water or air. The estimates indicate the
rate of downward movement of water when the soil is saturated. They are based on soil characteristics
observed in the field, particularly structure, porosity, and texture. Permeability is considered in
the design of soil drainage systems, septic tank absorption fields, and construction where the rate of
water movement under saturated conditions affects behavior.
AVAILABLE WATER CAPACITY refers to the quantity of water that the soil is capable of storing for use by
plants. The capacity for water storage is given in inches of water per inch of soil for each major soil layer.
The capacity varies, depending on soil properties that affect the retention of water and the depth of the root
zone. The most important properties are the content of organic matter, soil texture, bulk density, and soil
structure. Available water capacity is an important factor in the choice of plants or crops to be grown and in
the design and management of irrigation systems. Available water capacity is not an estimate of the quantity of
water actually available to plants at any given time.
SHRINK-SWELL POTENTIAL is the potential for volume change in a soil with a loss or gain of moisture. Volume
change occurs mainly because of the interaction of clay minerals with water and varies with the amount and type
of clay minerals in the soil. The size of the load on the soil and the magnitude of the change in soil moisture
content influence the amount of swelling of soils in place. Laboratory measurements of swelling of undisturbed
clods were made for many soils. For others, swelling was estimated on the basis of the kind and amount of
clay minerals in the soil and on measurements of similar soils. If the shrink-swell potential is rated moderate
to very high, shrinking and swelling can cause damage to buildings, roads, and other structures. Special design
is often needed. Shrink-swell potential classes are based on the change in length of an unconfined clod as
moisture content is increased from air-dry to field capacity. The change is based on the soil fraction less
than 2 millimeters in diameter. The classes are "Low," a change of less than 3 percent; "Moderate," 3 to 6
percent; and "High," more than 6 percent. "Very high," greater than 9 percent, is sometimes used.
U.S. DEPARTMENT OF AGRICULTURE PAGE 3 OF 4
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
PHYSICAL PROPERTIES OF SOILS
Endnote -- PHYSICAL PROPERTIES OF SOILS--Continued
ORGANIC MATTER is the plant and animal residue in the soil at various stages of decomposition. In report J,
the estimated content of organic matter is expressed as a percentage, by weight, of the soil material that is
less than 2 millimeters in diameter. The content of organic matter in a soil can be maintained or increased by
returning crop residue to the soil. Organic matter affects the available water capacity, infiltration rate, and
tilth. It is a source of nitrogen and other nutrients for crops.
EROSION FACTOR K indicates the susceptibility of the whole soil (including rocks and rock fragments) to
sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE)
to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The
estimates are based primarily on percentage of silt, sand, and organic matter (up to 4 percent) and on soil
structure and permeability. Values of K range from 0.05 to 0.69. The higher the value, the more susceptible
the soil is to sheet and rill erosion by water.
EROSION FACTOR Kf is like EROSION FACTOR K but it is for the fine-earth fraction of the soil. Rocks and
rock fragments are not considered.
EROSION FACTOR T is an estimate of the maximum average annual rate of soil erosion by wind or water that can
occur without affecting crop productivity over a sustained period. The rate is in tons per acre per year.
WIND ERODIBILITY GROUPS are made up of soils that have similar properties affecting their resistance to wind
erosion in cultivated areas. The groups indicate the susceptibility of soil to wind erosion. Soils are grouped
according to the following distinctions:
1. Coarse sands, sands, fine sands, and very fine sands.
These soils are generally not suitable for crops. They are
extremely erodible, and vegetation is difficult to
establish.
2. Loamy coarse sands, loamy sands, loamy fine sands, loamy
very fine sands, and sapric soil material. These soils are
very highly erodible. Crops can be grown if intensive
measures to control wind erosion are used.
3. Coarse sandy loams, sandy loams, fine sandy loams, and
very fine sandy loans. These soils are highly erodible.
Crops can be grown if intensive measures to control wind
erosion are used.
4L. Calcareous loams, silt loams, clay loans, and silty clay
loams. These soils are erodible. Crops can be grown if
intensive measures to control wind erosion are used.
4. Clays, silty clays, noncalcareous clay loams, and silty
clay loams that are more than 35 percent clay. These soils
are moderately erodible. Crops can be grown if measures to
control wind erosion are used.
U.S. DEPARTMENT OF AGRICULTURE PAGE 4 OF 4
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
PHYSICAL PROPERTIES OF SOILS
Endnote -- PHYSICAL PROPERTIES OF SOILS--Continued
5. Noncalcareous loans and silt loans that are less than 20
percent clay and sandy clay loans, sandy clays, and hemic
soil material. These soils are slightly erodible. Crops
can be grown if measures to control wind erosion are used.
6. Noncalcareous loans and silt loans that are more than 20
percent clay and noncalcareous clay loans that are less than
35 percent clay. These soils are very slightly erodible.
Crops can be grown if ordinary measures to control wind
erosion are used.
7. Silts, noncalcareous silty clay loams that are less than
35 percent clay, and fibric soil material. These soils are
very slightly erodible. Crops can be grown if ordinary
measures to control wind erosion are used.
8. Soils that are not subject to wind erosion because of
coarse fragments on the surface or because of surface
wetness.
The WIND ERODIBILITY INDEX is used in the wind erosion equation (WEQ) . The index number indicates the
amount of soil lost in tons per acre per year. The range of wind erodibility index numbers is 0 to 300.
U.S. DEPARTMENT OF AGRICULTURE PAGE 1 OF 2
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
HYDRIC SOILS LIST
NON-HYDRIC MAPUNITS
Pegasus
The "Hydric Soils Criteria" columns indicate the conditions that caused the mapunit component to be classified as "Hydric" or
"Non-Hydric". These criteria are defined in "Hydric Soils of the United States" (USDA Miscellaneous Publications No. 1491,
June, 1991. The "FSA Criteria" columns contain information needed for the Food Security Act determinations required by
Section 512.11(h) (4) of the National Food Security Manual (August, 1991) . See the "Criteria for Hydric Soils" endnote to
to determine the meaning of these columns. Spot symbols are footnoted at the end of the report.
I I I I FSA Criteria and
I I I Hydric Soils Criteria I Information I
Map Symbol IComponent(C)/I I I I I
Mapunit Name IInclusion(I) I Hydric I Local I Hydric I Meets I Meets I Meets I Natural I I
I Landform I Criteria ISaturationIFloodinglPonding (Condition' Needs
I I Code Criteria ICriterialCriterial of Soil IOn-Site I
I I I I I I I I I I
I I I I I I I I I I
79B: I I I I I I I I I I
starr silt loam, 2 to I I I I I I I I I I
7 percent slopes ISTARR (C)----I NO I I I I I I I I
I I I I I I I I I I
12C: I I I I I I I I I I
catoctin silt loam, 7 I I I I I I I I I I
to 15 percent slopes ICATOCTIN (C)-I NO I I I I I I
I I I I I I I I I I
23C: I I I I I I I I I I
davidson clay loam, 7 I I I I I I I I I I
to 15 percent slopes IDAVIDSON (C)-I NO I I I I I I
I I I I I I I I I I
71D: I I I I I I I I I I
rabun clay loam, 15 I I I I I I I I I I
to 25 percent slopes IRABUN (C)----I NO I I I I I I I I
I I I I I I I I I I
88: I I I I I I I I I I
udorthents, loamy IUDORTHENTS I I I I I I I I I
I (C) IUNRANKEDI I I I I I I I
I I I I I I I I I I
23B: I I I I I I I I I I
davidson clay loam, 2 I I I I I I I I I
to 7 percent slopes---IDAVIDSON (C)-I NO I I I I I I I
I I I I I I I I I I
U.S. DEPARTMENT OF AGRICULTURE PAGE 2 OF 2
NATURAL RESOURCES CONSERVATION SERVICE
HYDRIC SOILS CRITERIA CODES AND DEFINITIONS
Endnote -- HYDRIC SOILS LIST
The column 'Natural Condition of the Soil' indicates the following information: 'Wooded' indicates the soil supports
woody vegetation under natural condition; 'Farmable' indicates the soil can be farmed under natural conditions without
removing woody vegetation or other manipulation; and 'Neither' indicates neither of the above conditions are met.
1. All Histosols, except Folists, or
2. Soils in Aquic suborders, great groups, or subgroups, Albolls suborder, Aquisalids, Pachic subgroups, or Cumulic
subgroups that are:
a. somewhat poorly drained with a water table equal to 0.0 foot (ft.) from the surface during the growing season, or
b. poorly drained or very poorly drained and have either:
(1) water table equal to 0.0 ft. during the growing season if textures are coarse sand, sand, or fine sand in all
layers within 20 inches (in.), or for other soils, or
(2) water table at less than or equal to 0.5 ft. from the surface during the growing season if permeability is equal
to or greater than 6.0 in/hour (h.) in. all layers within 20 in., or
(3) water table at less than or equal to 1.0 ft. from the surface during the growing season, if permeability is less than
6.0 in./h. in any layer within 20 in., or
3. Soils that are frequently ponded for long or very long duration during the growing season, or
4. Soils that are frequently flooded for long or very long duration during the growing season.
U.S. DEPARTMENT OF AGRICULTURE PAGE 1 OF 3
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
WATER FEATURES
Pegasus
I I Flooding I High water table and ponding
I
Map symbol (Hydro-I I I I Water I I Maximum
and soil name (logic I Frequency Duration Months table I Kind of I Months Ponding I ponding
'group I depth (water tablel duration I depth
I I I I I I I
I I Ft I I Ft
I I I I I I I
79B: I I I I I I I
STARR I C (Occasional Brief NOV-APR >6.0 --- --- I --- I ---
I I I I I I I
12C: I I I I I I I I I
CATOCTIN C None ---
--- >6.0 --- --- --- ---
I I I I I
23C: I I I I I I I I I
DAVIDSON I B None --- --- >6.0 --- --- --- ---
I I I I I I I
71D: I I I I I I I I
RABUN I B (None --- I --- >6.0 --- I --- I --- I ---
I I I I I I I I
88: I 1 I I I I I I I
UDORTHENTS. I I I I I I I I I
I I I I I I I I I
23B: I I I I I I I I I
--- >6.0 ---
DAVIDSON I B None I --- ---
I --- I I --- I I
I I I I I I I I I
U.S. DEPARTMENT OF AGRICULTURE PAGE 2 OF 3
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
WATER FEATURES
Endnote -- WATER FEATURES
This report gives estimates of various soil water features. The estimates are used in land use planning that involves
engineering considerations.
Hydrologic soil groups are used to estimate runoff from precipitation. Soils not protected by vegetation are
assigned to one of four groups. They are grouped according to the infiltration of water when the soils are thoroughly
wet and receive precipitation from long-duration storms. The four hydrologic soil groups are:
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 permanent 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 two hydrologic groups in this report, the first letter is for drained areas and the second
is for undrained areas. Flooding, the temporary inundation of an area, is caused by overflowing streams, by runoff from
adjacent slopes, or by tides. Water standing for short periods after rainfall or snowmelt is not considered
flooding, nor is water in swamps and marshes. This report gives the frequency and duration of flooding and
the time of year when flooding is most likely. Frequency, duration, and probable dates of occurrence are estimated.
Frequency is expressed as "None", "Rare", "Occasional", and "Frequent". "None" means that flooding is not probable;
"Rare" that it is unlikely but possible under unusual weather conditions; "Occasional" that it occurs, on the
average, once or less in 2 years; and "Frequent" that it occurs, on the average, more than once in 2 years.
Duration is expressed as "Very brief" if less than 2 days, "Brief" if 2 to 7 days, "Long" if 7 to 30 days, and "Very
long" if more than 30 days. The information is based on evidence in the soil profile, namely thin strata of gravel,
sand, silt, or clay deposited by floodwater; irregular decrease in organic matter content with increasing depth;
and absence of distinctive horizons that form in soils that are not subject to flooding. Also considered are local
information about the extent and levels of flooding and the relation of each soil on the landscape to historic floods.
•
U.S. DEPARTMENT OF AGRICULTURE PAGE 3 OF 3
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
WATER FEATURES
Endnote -- WATER FEATURES--Continued
Information on the extent of flooding based on soil data is less specific than that provided by detailed engineering
surveys that delineate flood-prone areas at specific flood frequency levels.
High water table (seasonal) is the highest level of a saturated zone in the soil in most years. The depth to a
seasonal high water table applies to undrained soils. The estimates are based mainly on the evidence of a saturated
zone, namely grayish colors or mottles in the soil. Indicated in this report are the depth to the seasonal high
water table; the kind of water table, that is, "Apparent", "Artesian", or "Perched"; and the months of the year that
the water table commonly is high. A water table that is seasonally high for less than 1 month is not indicated in
this report.
An "Apparent" water table is a thick zone of free water in the soil. It is indicated by the level at which water
stands in an uncased borehole after adequate time is allowed for adjustment in the surrounding soil.
An "Artesian" water table exists under a hydrostatic beneath an impermeable layer. When the impermeable layer has been
penetrated by a cased borehole, the water rises. The final level of the water in the cased borehole is characterized as
an artesian water table.
A "Perched" water table is water standing above an unsaturated zone. In places an upper, or "Perched", water
table is separated from a lower one by a dry zone. Only saturated zones within a depth of about 6 feet are
indicated.
Ponding is standing water in a closed depression. The water is removed only by deep percolation, transpiration,
evaporation, or a combination of these processes.
This report gives the depth and duration of ponding and the time of year when ponding is most likely. Depth, duration,
and probable dates of occurrence are estimated.
Depth is expressed as the depth of ponded water in feet above the soil surface. Duration is expressed as "Very
brief" if less than 2 days, "Brief" if 2 to 7 days, "Long" if 7 to 30 days, and "Very long" if more than 30 days. The
information is based on the relation of each soil on the landscape to historic ponding and on local information about
the extent and levels of ponding.
U.S. DEPARTMENT OF AGRICULTURE PAGE 1 OF 2
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
SOIL FEATURES
Pegasus
Bedrock Cemented pan ( Subsidence I I Risk of corrosion
I Potential I
Map symbol I I I I I 'frost action Uncoated I
and soil name Depth Hardness l Depth I Kind Initiall Total I steel I Concrete
I I
In I I In I I In In I I
I I
79B: I I I I I
STARR >60 --- --- --- --- --- ( --- (Moderate (Moderate
I I
12C: I I I I I
CATOCTIN 20-40 Hard --- --- --- --- (Low (High (Moderate
( ( I I
23C: I ( I I I I I
DAVIDSON >60 --- --- --- --- --- --- (High (Moderate
( I I
71D: I I I I I I I
RABUN >60 --- --- --- ( --- ( --- --- (High (Moderate
( I I
88: I I I I I
UDORTHENTS. ( I ( I I
I I
23B: I I I I I I
DAVIDSON ( >60 --- --- ( --- ( --- ( --- ( --- (High (Moderate
( ( ( I I
•
•
U.S. DEPARTMENT OF AGRICULTURE PAGE 2 OF 2
NATURAL RESOURCES CONSERVATION SERVICE 10/26/99
SOIL FEATURES
Endnote -- SOIL FEATURES
This report gives estimates of various soil features. The estimates are used in land use planning that involves
engineering considerations.
Depth to bedrock is given if bedrock is within a depth of 5 feet. The depth is based on many soil borings and on
observations during soil mapping. The rock is either "Soft" or "Hard". If the rock is "Soft" or fractured, excavations
can be made with trenching machines, backhoes, or small rippers. If the rock is "Hard" or massive, blasting or
special equipment generally is needed for excavation.
Cemented pans are cemented or indurated subsurface layers within a depth of 5 feet. Such pans cause difficulty in
excavation. Pans are classified as "Thin" or "Thick". A "Thin" pan is less than 3 inches thick if continuously
indurated or less than 18 inches thick if discontinuous or fractured. Excavations can be made by trenching machines,
backhoes, or small rippers. A "Thick" pan is more than 3 inches thick if continuously indurated or more than 18
inches thick if discontinuous or fractured. Such a pan is so thick or massive that blasting or special equipment is
needed in excavation.
Subsidence is the settlement of organic soils or of saturated mineral soils of very low density. Subsidence
results from either desiccation and shrinkage or oxidation of organic material, or both, following drainage.
Subsidence takes place gradually, usually over a period of several years. This report shows the expected initial
subsidence, which usually is a result of drainage, and total subsidence, which usually is a result of oxidation. Not
shown in the report is subsidence caused by an imposed surface load or by the withdrawal of ground water throughout
an extensive area as a result of lowering the water table.
Potential frost action is the likelihood of upward or lateral expansion of the soil caused by the formation of
segregated ice lenses (frost heave) and the subsequent collapse of the soil and loss of strength on thawing. Frost
action occurs when moisture moves into the freezing zone of the soil. Temperature, texture, density, permeability,
content of organic matter, and depth to the water table are the most important factors considered in evaluating the
potential for frost action. It is assumed that the soil is not insulated by vegetation or snow and is not artificially
drained. Silty and highly structured clayey soils that have a high water table in winter are the most susceptible to
frost action. Well drained, very gravelly, or very sandy soils are the least susceptible. Frost heave and low soil
strength during thawing cause damage mainly to pavements and other rigid structures.
Risk of corrosion pertains to potential soil-induced electrochemical or chemical action that dissolves or weakens
uncoated steel or concrete. The rate of corrosion of uncoated steel is related to such factors as soil moisture,
particle-size distribution, acidity, and electrical conductivity of the soil. The rate of corrosion of concrete
is based mainly on the sulfate and sodium content, texture, moisture content, and acidity of the soil. Special
site examination and design may be needed if the combination of factors creates a severe corrosion environment. The steel
installations that intersect soil boundaries or soil layers is more susceptible to corrosion than steel in
installations that are entirely within one kind of soil or within one soil layer. For uncoated steel, the risk of
corrosion, expressed as "Low", "Moderate", or "High", is based on soil drainage class, total acidity, electrical
resistivity near field capacity, and electrical conductivity of the saturation extract.
For concrete, the risk of corrosion is also expressed as "Low", "Moderate", or "High". It is based on soil texture,
acidity, and amount of sulfates in the saturation extract.