How to Use and Read County = Ground Water Pollution Potentail Maps

How to Read and Use
Ground = Water=20 Pollution Potential=20 = Maps

A ground = water=20 pollution potential mapping program for = Ohio was=20 initiated in 1986 under the direction of = the=20 Ohio Department of Natural Resources, = Division=20 of Water. The DRASTIC mapping system, = developed=20 by Aller, et al., 1987, was chosen = because it=20 allows the pollution potential of an = aquifer to=20 be evaluated systematically using = existing=20 information. Vulnerability to = contamination is a=20 combination of hydrogeologic factors,=20 anthropogenic influences, and sources of = contamination for a given area. The = DRASTIC=20 system focuses on the hydrogeologic = factors that=20 influence ground water movement. Click = here for=20 a link to order the = DRASTIC Manual=20 by Aller, et al.

The system consists of two major=20 elements:

1. The designation of mappable units, = termed=20 hydrogeologic settings, and

2. The superposition of a relative = rating=20 system to determine the pollution = potential.

Hydrogeologic Settings

To facilitate = the=20 designation of mappable units, the = DRASTIC=20 system used the framework of an existing = classification system developed by Heath = (1984),=20 which divides the United States into 15 = ground=20 water regions based on the factors in a = ground=20 water system that affect occurrence and=20 availability. Of the 15 regions, two = fall within=20 Ohio: 6- Nonglaciated Central Region and = 7-Glaciated Central Region. Within each = major=20 hydrogeologic region, smaller units = representing=20 specific hydrogeologic settings are = identified.=20 Hydrogeologic settings form the basis of = the=20 system and represent a composite = description of=20 the major geologic and hydrogeologic = factors=20 that control ground water movement into, = through, and out of an area. A = hydrogeologic=20 setting represents a mappable unit with = common=20 hydrogeologic characteristics and, as a=20 consequence, common vulnerability to=20 contamination (Aller et al., 1987). The = figure=20 below is an example of a typical = hydrogeologic=20 setting in the glaciated region of=20 Ohio.

Example of a = DRASTIC=20 hydrogeologic setting.

This setting is 7D Buried Valley. = Hydrogeologic settings describe areas of = common=20 geologic and ground water = characteristics that=20 directly affect the vulnerability of an = aquifer=20 to contamination from the=20 = surface.

Relative Rating System
=
    Hydrogeologic=20 settings form the basis of the system = and=20 incorporate the major hydrogeologic = factors that=20 affect and control ground water movement = and=20 occurrence.

These seven factors are:

D epth to = Water
R=20 echarge (Net=20 Recharge)
A=20 quifer Media
S = oil=20 Media
T opography (% = slope)
I mpact of = the Vadose=20 Zone Media
C = onductivity=20 (Hydraulic) of the = Aquifer)

    DRASTIC uses = a=20 numerical rating and weighting system = that is=20 combined with the seven DRASTIC factors = listed=20 above to calculate a ground water = pollution=20 potential index or relative measure of=20 vulnerability to contamination. The = DRASTIC=20 factors are weighted from 1 to 5 = according to=20 their relative importance to each other = with=20 regard to contamination potential. Each = factor=20 is then divided into ranges or media = types and=20 assigned a rating from 1 to 10 based on = their=20 significance to pollution potential. = (Higher=20 numbers means higher pollution = potential) The=20 following table is an example of the = rating and=20 weighting system.

    Hydrogeologic = settings are combined with the pollution = potential indexes to create units that = can be=20 graphically displayed on a map (see = below=20 description).
Sand&Gravel/Silt&Clay

SETTING=20 7D6 GENERAL

FEATURE RANGE RATING WEIGHT NUMBER

Depth to Water 30-50 feet 7 X 5 =3D 35

Net Recharge 4-7 inches 6 X 4 =3D 24

Aquifer Media Sand & = Gravel 6 X 3 =3D 18

Soil Media Silt Loam 4 X 2 =3D 8

Topography 0-2% slope 10 X 1 =3D 10

Impact of Vadose Zone 6 X 5 =3D 30

Hydraulic Conductivity 300-700 gpd/ft 2 4 X 3 =3D 12

DRASTIC=20 INDEX 137

    Once a = DRASTIC index=20 has been calculated, it is possible to = identify=20 areas that are more likely to be = susceptible to=20 ground water contamination relative to = other=20 areas. The higher the DRASTIC index, the = greater=20 the vulnerability to contamination. The = index=20 generated provides only a relative = evaluation=20 tool and is not designed to produce = absolute=20 answers or to represent units of=20 vulnerability.

    The maps are=20 color-coded using ranges depicted on the = map=20 legend. The color codes used are part of = a=20 national color-coding scheme developed = to assist=20 the user in gaining a general insight = into the=20 vulnerability of the ground water in the = area.=20 The color codes were chosen to represent = the=20 colors of the spectrum, with warm colors = (red,=20 orange, and yellow) representing areas = of higher=20 vulnerability (higher pollution = potential=20 indexes), and cool colors (greens, = blues, and=20 violet) representing areas of lower=20 vulnerability to contamination.

Hydrogeologic settings are combined = with the=20 pollution potential indexes to create = units that=20 can be graphically displayed on a map. = (See=20 below description)

    Here the = first number=20 (7) refers to the major hydrogeologic = region=20 (Glaciated Central Region) and the upper = case=20 letter (D) refers to a buried valley=20 hydrogeologic setting. The following = number (6)=20 references a certain set of DRASTIC = parameters=20 that are unique to this setting and are=20 described in the corresponding setting = chart=20 shown above. The number on the bottom = (137) is=20 the calculated pollution potential index = for=20 this unique setting. The charts for each = setting=20 provide a reference to show how the = pollution=20 potential index was derived.

    A report = accompanies=20 each map that includes general geologic = and=20 hydrogeologic information and describes = the=20 mapping process used to determine the = ground=20 water pollution potential of areas = within a=20 county.

Applications of Pollution Potential = Maps=20

    The pollution = potential mapping program offers a wide = variety=20 of applications in many counties.The = ground=20 water pollution potential maps are = prepared to=20 assist planners, managers, and state and = local=20 officials in evaluating the relative=20 vulnerability of areas to ground water=20 contamination from various sources of = pollution.=20 This information can be used to help = direct=20 resources and land use activities to = appropriate=20 areas, or to assist in protection, = monitoring,=20 and clean-up efforts.

    An important=20 application of the pollution potential = maps for=20 many areas will be assisting in county = land use=20 planning and resource expenditures = related to=20 solid waste disposal. A county may use = the map=20 to help identify areas that are suitable = for=20 disposal activities. Once these areas = have been=20 identified, a county can collect more=20 site-specific information and combine = this with=20 other local factors to determine site=20 suitability.

    Pollution = potential=20 maps may be applied successfully where = non-point=20 source contamination is a concern. = Non-point=20 source contamination occurs where land = use=20 activities over large areas impact water = quality. Maps providing information on = relative=20 vulnerability can be used to guide the = selection=20 and implementation of appropriate best=20 management practices in different areas. = Best=20 management practices should be chosen = based upon=20 consideration of the chemical and = physical=20 processes that occur from the practice, = and the=20 effect these processes may have in areas = of=20 moderate to high vulnerability to = contamination.=20 For example, the use of agricultural = best=20 management practices that limit the = infiltration=20 of nitrates, or promote denitrification = above=20 the water table, would be beneficial to=20 implement in areas of relatively high=20 vulnerability to contamination.

    A pollution = potential=20 map can assist in developing ground = water=20 protection strategies. By identifying = areas more=20 vulnerable to contamination, officials = can=20 direct resources to areas where special=20 attention or protection efforts might be = warranted. This information can be = utilized=20 effectively at the local level for = integration=20 into land use decisions and as an = educational=20 tool to promote public awareness of = ground water=20 resources. Pollution potential maps may = be used=20 to prioritize ground water monitoring = and/or=20 contamination clean-up efforts. Areas = that are=20 identified as being vulnerable to = contamination=20 may benefit from increased ground water=20 monitoring for pollutants or from = additional=20 efforts to clean up an aquifer.

    Individuals = in the=20 county who are familiar with specific = land use=20 and management problems will recognize = other=20 beneficial uses of the pollution = potential maps.=20 Planning commissions and zoning boards = can use=20 these maps to help make informed = decisions about=20 the development of areas within their=20 jurisdiction. Developers proposing = projects=20 within ground water sensitive areas may = be=20 required to show how ground water will = be=20 protected.

    Regardless of = the=20 application, emphasis must be placed on = the fact=20 that the system is not designed to = replace a=20 site-specific investigation. The = strength of the=20 system lies in its ability to make a = "first-cut=20 approximation" by identifying areas that = are=20 vulnerable to contamination. Any = potential=20 applications of the system should also = recognize=20 the assumptions inherent in the=20 system.

Sample Preprinted Ground = Water=20 Pollution Potential = Map.

Enlarged area from above = sample=20 map.

Click=20 here for a map of available=20 counties.
To order = available=20 maps or for more information on mapping=20 contact:

The Ohio Department of Natural=20 Resources
Division of Water
Water=20 Resources Section
2045 Morse Road, = Bldg.=20 B
Columbus, Ohio 43229-6693

Phone: (614) 265-6740
Fax: (614)=20 265-6767
E-mail: mailto:water@dnr.state.oh.us

COST:=20 =      $10.00/Report=20 (Plus postage and handling, See chart = below)

Payment
Methods:=20
VISA, Mastercard or check.
( Make = checks=20 payable to: ODNR - Division of Water=20 = )

Postage and Handling=20 Costs

less = than or=20 equal to $10.00 add $ = 2.50

more than $10.00 = and less=20 than or equal to $20.00 add $ 3.75

more than $20.00 = and less=20 than or equal to $50.00 add $ 6.00

more than $50.00 = and less=20 than or equal to $100.00 add $ 8.50

more than = $100.00 add=20 = $10.00

You may also want to=20 = see:

State=20 Aquifer Mapping Project (1998 to=20 2000).=20
Ground=20 Water Resources=20 Maps
=20 =

How to Read and UseGround = Water=20 Pollution Potential=20 = Maps

Hydrogeologic Settings

Relative Rating System

Applications of Pollution Potential = Maps=20

Click=20 here for a map of available=20 counties.To order = available=20 maps or for more information on mapping=20 contact:

How to Read and Use
Ground = Water=20 Pollution Potential=20 = Maps

Click=20 here for a map of available=20 counties.
To order = available=20 maps or for more information on mapping=20 contact: