Summary Statement:

This metadata summary applies exclusively to the data as it appears in this Loudoun County intranet/internet mapping application. To see the fully FGDC compliant version of this metadata click here.

Abstract:

Hydric Soils are those that are wet at or near the ground surface for significant periods of the growing season. Digital data consists of mapping units of the various soil types found in Loudoun County, Virginia.

Purpose:

Digital data are used to identify the mapping unit potential for a variety of uses, such as agriculture, drain field suitability, construction concerns, or development possibility.

Supplemental Information:

The data were collected by digitizing manuscript maps derived from USDA soil maps and supplemented by both fieldwork and geological data. Fieldwork for the soil survey was first conducted between 1947 and 1952. Soils were originally shown at the scale of 1:15840 and then redrafted by the County soil scientist to 1:12000; the data were redrafted a final time to fit Loudoun County's base map standard of 1:2400. Although the current data rely heavily on the original soil survey, there have been extensive field checks and alterations to the soil map based on current soil concepts and land use. The data are updated as field site inspections or interpretation changes occur.

Data are stored in the corporate ArcSDE Geodatabase as a polygon feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN.

Maintenance and Update Frequency:

As Needed; The data are updated as field site inspections or interpretation changes occur.

Completeness Report:

Features may have been eliminated or generalized due to scale and intended use. To assist Loudoun County, Virginia in the maintenance of the data, please provide any information concerning discovered errors, omissions, or other discrepancies found in the data.

Data Owner:

Department of Building and Development

Hydric Soils:

Hydric soils are one of the three parameters used to define wetlands. The other two parameters include hydrology (actual perched or apparent water tables) and vegetation (plants identified to survive only or best in wet areas). This list of Hydric Soils should be used only as a guide since soils maps are not intended for site-specific purposes.

Mapping units that are dominantly Hydric Soils

4A   =  Hatboro loam, 0 to 3 % slopes
6A   =  Bowmansville silt loam, 0 to 3 % slopes
66A  =  Waxpool silt loam, 0 to 3 % slopes
69A  =  Elbert silty clay loam, 0 to 3 % slopes
79A  =  Albano silt loam, 0 to 3 % slopes
99A  =  Kinkora-Delanco complex, 0 to 3 % slopes

Mapping units that contain significant inclusions of Hydric Soils

5A   =  Rowland silt loam, 0 to 3 % slopes
10B  =  Mongle loam, 0 to 7 % slopes
12B  =  Rohrersville cobbly loam, 1 to 7 % slopes
63A  =  Kelly silt loam, 0 to 3 % slopes
78A  =  Dulles silt loam, 0 to 3 % slopes
82B  =  Scattersville silt loam, 1 to 7 % slopes
98B  =  Clapham silt loam, 1 to 8 % slopes

HYDROLOGIC SOIL GROUPS

This section provides a description of hydrologic soil group classes used in determining soil-cover complexes in Chapter 2 of Technical Release 55, "Urban Hydrology for Small Watersheds", prepared by the USDA Soil Conservation Service.

The hydrologic parameter (A, B, C, or D) is an indicator of the minimum rate of infiltration obtained for a bare soil after prolonged wetting. By using the hydrologic classification and the associated land use, runoff curve numbers can be selected. Runoff curve numbers are used for determining peak quantity and total volume of surface water runoff for given conditions.

Classes Defined

     1.   A - Low Runoff Potential

    Soils having a high infiltration rate, even when thoroughly wetted, and consisting chiefly of deep, well to excessively drained sands or gravels.

    2.   B - Soils with Moderate Infiltration Rate

    Soils having a moderate infiltration rate when thoroughly wetted, and consisting chiefly of moderately well to well drained soils with moderately fine to moderately coarse texture.

    3.   C - Soils with Slow Infiltration Rate

    Soils having a slow infiltration rate when thoroughly wetted, and consisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine texture.

    4.   D - High Runoff Potential

    Soils having a very slow infiltration rate when thoroughly wetted, and consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a clay pan or clay layer at 
    or near the surface, and shallow soils over nearly-impervious material.

4A Hatboro
loam,

(0-3%)
         
frequent
flooding,
         
Hydric soil
         
(D)

6A 
Bowmansville
silt loam,

(0-3%)
         
occasional
flooding,
         
Hydric soil
         
(C)

66A Waxpool
silt loam,

(0-3%)
         
ponding,
         
(D)
         
Hydric soil

69A Elbert
silty clay
loam,

(0-3%)
         
ponding,
      
         
(D)
        
Hydric soil

79A Albano
silt loam,


(0-3%)
         
brief ponding,
      
         
(D)
        
Hydric soil

99A Kinkora-
Delanco
complex


(0-3%)
         
rarely flooded,
      
         
Hydric soil
        
(D/C)