Protecting Local Groundwater Resources

Prepared by:
L. Steven Smutko, Leon E. Danielson and Dana L. Hoag
Agricultural and Resource Economics, Applied Resource Economics and Policy Group

Many North Carolina communities rely on groundwater for public water supplies for large municipal systems, as well as community systems serving small subdivisions, mobile home parks, schools, and churches. This makes protecting groundwater an important l ocal issue.

The foundation of a groundwater protection program is the delineation of protection areas surrounding public water supply wells where groundwater recharge will likely become the source of drinking water. Within these protected areas, good manage-ment ca n reduce the threat of contaminants entering the well recharge areas and polluting public water supplies.

Planning for Protection

Protection of groundwater resources requires good planning and concerted effort. Because groundwater contamination is often irreversible, taking steps to protect groundwater by preventing contamination is usually more effective and less costly than reme diation.

Planning for groundwater protection occurs in response to threats to the groundwater resource. The greatest threats to groundwater resources are created by human activity. Groundwater resources can be disrupted by contamination and by altering groundwater levels.

Figure 1-Sources of Groundwater Contamination

Contamination

Common contaminants consist of bacteria, minerals, and inorganic or organic chemicals that are present in the aquifer or introduced to it at the ground surface. Landfills, waste lagoons, and leaking underground storage tanks are the most common sources o f contamination from industrial sources.

The use of farm fertilizers, pesticides, and animal-waste lagoons can cause local contamination of shallow aquifers. Septic disposal systems, and improper storage, use or disposal of household and lawn chemicals are the most common contamination sources from domestic land uses.

Altered Groundwater Levels

Water quantity problems can stem from reduced groundwater levels as well as artificially increased levels. Reduced recharge occurs when water that would otherwise filter into the aquifer is diverted to surface water bodies or taken out of the groundwater recharge basin.

One of the most significant causes of recharge problems is the increase in impermeable surfaces, such as buildings, other structures, and pavement in recharge areas. Withdrawals from the aquifer that are not returned also lower the groundwater table. Thi s has been a problem in the Castle Hayne and Cretaceous aquifers in eastern North Carolina.

Problems of artificially increased groundwater levels can stem from an increased rate of groundwater recharge (from surface water irrigation), or a disruption in groundwater discharge. Common effects of elevated groundwater levels include mineralized soi ls in irrigated areas and property damage from basement flooding.

Figure 2. Sources of Hydrogeologic Data

Information concerning general aquifer characteristics can be found in the following publications and maps:

Basic Elements of Ground-Water Hydrology with Reference to Conditions in North Carolina. Ralph C. Heath. 1980. USGS Water Resources Investigations Open File Report 80-44.
Ground Water of the Piedmont and Blue Ridge Provinces in the Southeastern United States. H. E. LeGrand. 1967. USGS Circular 538.
Groundwater Resources of the Southern Pines Area; A Supplement to the Sandhills Capacity Use Study. 1980. NC Office of Water Resources.
Hydrologic Framework of the North Carolina Coastal Plain Aquifer System. M. D. Winner, Jr. and R. W. Coble. 1989. USGS Open File Report 87-690.
Hydrogeologic Unit Map of the Piedmont and Blue Ridge of North Carolina. Charles C. Daniel, III and Robert A. Payne. 1990. USGS Water Resources Investigations Report 90-4035.
Water Resources of Northeast North Carolina. H. B. Wilder, T. M. Robison, and K. L. Lindskov. 1978. USGS Water Resources Investigations Report 77-81.
Simulation of Ground-Water Flow in the Coastal Plain Aquifer System of North Carolina. G. L. Giese, J. L. Eimers, and R. W. Coble. 1990. USGS Open File Report 90-372.

Sources of Information on Groundwater Use

Information on community water supply wells is maintained by the Department of Environment, Health and Natural Resources, Division of Environmental Health, Public Water Supply Section. Information on each well system includes number of connections, popul ation served, data on well site, well, pump, treatment, monitoring results, and contaminant violations.

Some data are computerized and can be easily accessed through the Public Water Supply Section's computer, however, most information is kept on paper files in the Section's office in Raleigh.

Developing a Local Database

Effective protection measures require information about the groundwater resource and usage, human activities, and land uses that can have an impact on the resource and its use.

Hydrogeologic Data

Groundwater resources underlying the community must be identified and described in map format. Size, yield, and direction of flow must also be assessed. Determining the rate and direction of groundwater flow is important for identifying recharge areas a nd delineating areas needing protection.

Water quality data is also a necessary component of the local database since it provides information for identifying existing and potential management problems.

Groundwater Use Data

Effective planning requires data on quantities, withdrawal locations, and specific uses of groundwater. Community wells must be mapped and their rates of withdrawal documented.

Location and other characteristics of private wells must also be documented to understand overall use of the local aquifers. Data should be gathered on types of usage, e.g. residential, industrial, agricultural irrigation, in order to establish managemen t priorities.

Land Use Data

Existing and proposed land uses can be mapped along with hydrogeologic and water use data to obtain a clear picture of the relationship between land use and existing and potential groundwater problems.

This information helps identify sources of contamination and potential threats to groundwater.

Figure 3. Defining Hazardous Substances.
What is Hazardous?

Defining and assessing pollution hazards requires a knowledge of what is potentially hazardous and what is not. Limiting the storage and handling of hazardous substances in the vicinity of public water supply systems is one method of protecting groundwat er supplies.

However, selecting those materials which should be regulated is no easy task. One source of information is the federal government. Substances that are deemed potentially hazardous if allowed to escape into the environment have been defined in several fed eral laws that regulate their storage and use.

Lists of these substances can be found in the following laws:

The federal Clean Water Act (CWA) Section 311 contains a list of about 300 substances. The CWA list is printed in the Federal Register, Volume 54, August 14, 1989, p.33482.
Superfund Amendments and Reauthorization Act of 1986, Title III, (SARA) Section 302. This list contains 366 chemicals included in EPA's List of Extremely Hazardous Substances. The SARA list can be found in the Federal Register, Volume 52, April 22, 1987, p.13378.
The Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) lists 721 chemicals as hazardous substances. This list can be found in 40 CFR Part 302, Table 302.4.
Other listings are contained in Section 3001 of the Solid Waste Disposal Act at 42 U.S.C. 6921, and Section 2606 of the Toxic Substances Control Act.

These lists contain many overlapping entries. The US EPA has developed a consolidated "List of Lists" including SARA Section 302 substances and CERCLA substances.

This list may be obtained by calling the EPA Title III Hotline: 1-800-535-0202.

The CERCLA list of hazardous substances includes hazardous wastes identified in the Resource Conservation and Recovery Act (RCRA) which includes both specific chemicals and waste streams. The substances covered by Section 311 of the CWA include oil and o ther petroleum products.

Analytical Techniques for Developing Groundwater Protection Plans

Once a local groundwater database has been established, a variety of analytical techniques can be employed to develop groundwater protection plans.

Identification of Sensitive Areas

A sensitive area is an area that can be easily polluted or an area that once polluted will pose a substantive risk to water consumers. Sensitive groundwater protection areas are those that are within a public supply well's "zone of contribution" the area surrounding the well that directly contributes water to a pumping well. These areas are referred to as well-head protection areas.

Sensitive areas can also include recharge areas which, although quite distant from the well, recharge underground water supplies within a time frame considered relevant. An alternative to identifying sensitive areas is to classify the aquifer according t o use such as public drinking water supply, irrigation, or waste assimilation.

Groundwater Modeling

Modeling techniques can be used to predict movement of contaminants in the aquifer, estimate the effects of land use changes in recharge areas, and predict development effects on groundwater quality. Models can provide the water resource manager with the information necessary to determine residential densities compatible with groundwater quality objectives.

Ranking Existing and Potential Threats

Groundwater managers must assess existing and potential pollution hazards to identify management priorities. The risks that an activity poses depend on the hazards inherent in the particular activity, where it occurs, and how many people might be affecte d by it.

Establish Goals and Objectives

Community goals and objectives related to groundwater protection must be identified before management options can be selected. The community must define what needs to be protected and how much protection it can afford.

Protection can extend to the en tire aquifer within jurisdictional boundaries, to important recharge areas, or to areas surrounding public supply wells. The hydrologic regime, sources and kinds of threats to the aquifer, and water use in the community are the parameters from which such a determination is made.

The question of how much protection is needed or desired will depend again on the characteristics of the resource and its use and abuse, as well as other community goals. Some groundwater protection strategies will limit the types and amount of urban dev elopment relative to the groundwater supply. It may be necessary to forgo future industrial development in a particular area if protection goals are to be achieved. Decisions must be made as to how groundwater protection goals and economic development g oals can be integrated.

Figure 4-Protection of Sensitive Areas
Wellhead Protection Area

Prevention Options: Control of Contamination Sources

Groundwater protection measures can be directed toward two fronts: (1) control of the sources of contamination, or (2) protection of sensitive areas through land use planning measures. Although this discussion focuses on the latter set of alternatives, i t is worthwhile to discuss the options available for controlling groundwater pollution at the source. Communities may choose to adopt source controls for several reasons. It is often the case that a pollution problem is the impetus for a community to be gin groundwater protection measures. An existing land use, such as a landfill in a groundwater recharge area, is one example of such incompatibility. Source control techniques are necessary when development has occurred that can potentially threaten groun dwater supplies.

It may not be technically possible for a community to delineate sensitive areas. The underlying hydrogeologic formations may be so complex that a community may not have the resources to map the aquifer accurately or a highly permeable geologic formation may underlie the entire community. This is the case with the surficial aquifer in the Sand Hill region of North Carolina. Under these circumstances, source controls would be an appropriate means of groundwater protection. Three types of source control mea sures are discussed below.

Design Standards

Design standards are used to regulate the design and construction of new structures, infrastructure items such as parking lot runoff collection systems, and hazardous material storage systems.

Operating Standards

Operating standards are procedures to prevent or limit pollution. They usually take the form of agricultural or industrial Best Management Practices (BMPs). BMPs generally define a set of standard operating procedures that can be used in a particular in dustry or agricultural activity to limit the threat of groundwater contamination through accidental spillage, over application, or misuse of hazardous substances.

Source Prohibitions

These measures involve prohibiting the storage or use of dangerous materials in sensitive areas. Source prohibition regulations generally take the form of either prohibitions against certain kinds of activities that typically require the use of specific hazardous substances, or restrictions on the use of the substances themselves.

Figure 5. Management Tools for Groundwater Protection.

A number of commonly used land use controls, source controls, and other management methods can be effectively applied by local governments for protecting underground drinking water supplies. These management tools have been compiled by the US EPA in a publication entitled Wellhead Protection Programs: Tools for Local Governments.

Zoning ordinances: Direct land development and regulate land uses.

Subdivision ordinances: Protect land divided for development.

Site plan reviews: Help ensure compliance with development plan.

Design standards: Prevent groundwater contamination by setting

design and construction standards

Operating standards: Help regulate potentially hazardous practices.

Source prohibitions: Prohibit development or materials that

threaten groundwater.

Purchase of property: Ensures control of land uses in areas to

be protected.

Public education: Builds support for groundwater protection

activities.

Groundwater monitoring: Helps assess groundwater quality.

Household hazardous waste collection: Reduces threats to

groundwater from hazardous waste disposal.

Water conservation: Reduces contamination from salt water intrusion.

Source:
U.S. EPA. 1989. Wellhead Protection Programs: Tools for Local Governments. EPA 440/6-89-002. Washington D.C.: Office of Groundwater Protection, U.S. Environmental Protection Agency.

Prevention Options: Guiding Land Use in Sensitive Areas

Protection of sensitive areas by guiding land use and development provides the best opportunity for groundwater protection. These programs are particularly useful if the sensitive areas are largely undeveloped. Protection can be proactive and comprehens ive, providing a mechanism to guide local growth and development so that it is compatible with groundwater protection objectives. The earlier a groundwater protection plan is adopted and implemented, the lower will be the economic costs of protection, since fewer incompatible activities will be affected.

Sensitive area protection programs rely heavily on land use controls, particularly zoning and subdivision ordinances. But other non-regulatory alternatives such as land purchase, monitoring, and education can supplement these programs. In fact, the most effective groundwater protection programs integrate land use controls with other techniques to formulate a comprehensive response to ground-water contamination and misuse.

To enhance their effectiveness, land use controls should be tailored to: (1) area hydrologic conditions; (2) well characteristics (where applied to well-head areas); (3) associated development alternatives; and, (4) existing local, state and federal pro grams. Hydrologic conditions will affect the type and extent of land use controls that are most appropriate for a given community. For example, the spatial requirements of land use controls in a community underlain by an unconsolidated aquifer formation may follow a simple elliptical pattern or even a circular pattern around the zone of influence of a community well field.

In the case of wellhead and well field protection programs, well characteristics are important. Similar to hydrologic conditions, well characteristics, such as topographic location and average pumping rate, will affect the spatial application of land use controls.

Associated development goals will affect the intensity as well as the selection of land use control alternatives. Communities may wish to substitute source controls for land use options in areas where land uses are potentially incompatible with groundwat er protection objectives rather than forego the activity altogether.

Local land use alternatives must be evaluated in terms of their compatibility with existing local, state, and federal programs for groundwater and surface water protection. Many activities that are potentially damaging to the environment are currently re gulated under state and federal rules and regulations regarding source controls. Land use controls should be developed to complement existing programs.

The two most commonly employed land use planning tools for groundwater protection are zoning and subdivision ordinances.

Zoning

Zoning consists of dividing a municipality into land use districts and applying regulations uniformly within each district. Zoning both defines what kind of general land use can occur within a given district and specifies a set of applicable regulations for that district.

Zoning has been used as a tool to protect groundwater resources in a number of ways. It is best used as a method for directing future growth in ways that are compatible with development objectives (groundwater protection being one of them). It is not an effective method of altering land uses once they are established.

If a sensitive area is not yet zoned and undeveloped, the most direct approach would be to zone the area for some compatible use such as low-density residential with limited septic system use, or open space.

Several zoning techniques are available for protecting groundwater in a variety of circumstances. These include large-lot zoning, conditional zoning, floating zones, incentive zoning, overlay zoning, and planned unit developments.

Subdivision Regulation

Subdivision ordinances apply to a parcel of land that is to be divided for resale and future development. Subdivision regulations attempt to ensure that the subdivided lands appropriately relate to their surroundings. They contain provisions on the loca tion and construction of roadways, storm and sanitary sewers, open spaces, and public areas within the subdivision.

Subdivision regulations are particularly suitable for groundwater protection planning. Location and amount of open space, storm sewer design, amount and location of pavement and other impermeable surfaces, are all items relevant to groundwater protection that can be managed through subdivision ordinances. Source control regulations can be combined with subdivision ordinances to provide additional protection. However, like zoning ordinances, subdivision regulations are most useful for controlling future development, and have little application in previously developed areas.

Zoning and subdivision ordinances are only the most common tools for groundwater protection; there are a host of other regulatory and nonregulatory alternatives available. By integrating source controls with land use controls and nonregulatory protection measures, groundwater protection planning can be both effective and workable.

List of Resources

Jaffe, Martin and Frank DiNovo. 1987. Local Groundwater Protection. Chicago: American Planning Association.

U.S. EPA. 1990. Wellhead Protection Programs: Tools for Local Governments. Management Workshops in Innovative Techniques for Wellhead Protection. Workshop Proceedings, Sept. 11-12, 1990, Charleston, SC. Washington D.C.: U .S. Environmental Protection Agency.

U.S. EPA. 1989. Wellhead Protection Programs: Tools for Local Governments. EPA 440/6-89-002. Washington D.C.: Office of Groundwater Protection, U.S. Environmental Protection Agency.

AREP93 4 October 1993

bridgesj@unity.ncsu.edu

04/16/96