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III.F. Water Resources Management
Local governments may be responsible for managing the water resources within their borders. Water resources include surface waters (i.e., coastal bays, lakes, rivers, and streams) and groundwater. The water resources managed by the local government may be used to supply drinking water, industrial process water, or water for recreational opportunities. For each of these uses, local governments are primarily responsible for assuring the water is safe and available in sufficient quantities to be used for its intended purpose. Activities related to water resources management include protecting and managing surface waters, including reservoirs, and protecting groundwater drinking supplies. In contrast to the previously described local government operations, the implementation of water resources management activities have a minimal impact on the environment. Rather, the activities themselves are designed to reduce the environmental impact on water resources.
Local governments may be responsible for protecting surface waters for designated uses such as drinking water, habitat preservation, or recreation. Surface waters are generally protected through the implementation of Best Management Practices (BMPs), watershed monitoring, and in some cases, reservoir management BMPs. BMPs may be structural, or nonstructural. BMPs include managing existing sources or conduits of contamination such as roads, bridges, and storm water systems. BMPs also include new structures designed to prevent contaminants from reaching surface waters, such as wet ponds, extended retention dry ponds, and infiltration trenches (porous pavement, underground detention tanks, and water quality inlets). Nonstructural BMPs include grassed swales, street cleaning, and fertilizer application control. Finally, BMPs include pollution prevention activities. The potential impacts of building surface water protection structures and implementing surface water protection programs are reduced contamination of water sources and increased opportunities to use those sources for their intended purposes. (A Current Assessment of Urban Best Management Practices, Metropolitan Washington Council of Governments, 1992; and Wellhead Protection Programs: Tools for Local Governments, U.S. EPA, 1989; and Northern Virginia BMP Handbook, 1992)
Structural BMPs
Structural BMPs are designed to prevent, inhibit, or slow the rate at which storm water runoff or spilled contaminants reach a body of water. BMP structures such as extended detention ponds, wet ponds, and storm water wetlands prevent contaminants from reaching surface waters by capturing runoff and allowing it to filter through the soil or evaporate, rather than directly flowing to a water body. Additional filtering structures include sand filters, oil and grit separators, and infiltration basins. Containment structures may require periodic maintenance to remove accumulated sediment, while filtering structures may require maintenance to remove debris and assure the filters are working efficiently. Each of these structures help remove contaminants from rainwater to protect the surface water for its intended use.
Nonstructural BMPs
Local governments may be responsible for implementing nonstructural BMPs including operational activities such as street sweeping, or maintaining or preserving grassed swales, vegetative buffer areas, or marsh vegetation.
Street Sweeping
Local governments may sweep streets to prevent contaminants from vehicles from reaching surface waters. While many local governments may sweep the streets to improve community aesthetics or as part of their NPDES combined sewer or storm water permits, street sweeping is also an effective tool in protecting water resources. Contaminants typically found on streets include the following:
· Particulates from local soil erosion
· Nitrogen and phosphorus from local plants and soils
· Phenolic compounds from wear of asphalt street surfaces
· Grease, petroleum, n-paraffin, and lead from vehicle leaks and spills
· Lead, zinc and asbestos from tire wear
· Asbestos, lead, chromium, copper and nickel from clutch and break lining wear
· Chlorides from deicing compounds.
Street sweeping protects surface waters by removing solids such as sand, debris, and litter that would otherwise be transported to the surface water during a rain event. Street sweeping also prevents contaminants that may be absorbed by sand and debris from reaching surface water.
Vegetative Buffer Areas
Vegetative buffer areas are physical active controls designed and maintained to filter and infiltrate pollutants. These are areas specifically designed to prevent contaminants from reaching surface waters. These areas complement passive controls such as land use or zoning laws that prevent activities (e.g. paving, pesticide use) that could increase surface water contamination.
Marsh Vegetation
Marsh vegetation is used by local governments to help break down contaminants before they reach open bodies of water. Local governments may actively manage marsh areas by adding new plants, and removing accumulated sediment.
Watershed Monitoring
Watershed monitoring programs complement implementation of structural and nonstructural BMPs by providing the local government with a comprehensive tool to measure the effectiveness of the BMPs. Watershed monitoring programs include collection and observation of water, insects, aquatic plants, and fish from locations throughout the watershed. Chemical analysis is performed to determine whether specific contaminants have infiltrated a water body, while biological analysis is conducted to evaluate the impact of contaminants on various plant, animal, and insect species. Samples taken for chemical analaysis (e.g. phosphorus, metals) are generally analyzed in a laboratory, while physical attributes (turbidity, temperature, color) are analyzed in the field. Biological monitoring evaluates the health of a water body by determining the number and type of plant, fish, and insect species found in the water body. Samples for biological analysis may be analyzed in the field or in a laboratory. By allowing local governments to measure the effectiveness of various BMPs, and the relative health of a water body over time, watershed monitoring programs can promote the use of effective activities to protect surface waters. The sampling process has a minimal impact on the environment. Information on the potential impacts of chemical analysis in laboratories is provided in the section on Wastewater Treatment operations.
Reservoir Management
Protecting reservoirs is a key component to a local government's surface water protection program. Reservoirs provide aboveground natural or manmade open air containment of untreated water. Keeping reservoirs clean and free from contamination helps assure a safe supply of drinking water. In addition, preventing debris, sedimentation, litter, chemicals or other pollutants from entering a reservoir reduces the amount of treatment necessary for the water to meet drinking water standards. While managing reservoirs includes many of the BMPs described above, reservoir management includes additional measures as well, such as establishing security around the reservoir and creation of buffer zones.
Reservoir security includes controls to prevent direct litter, dumping, or inappropriate use. Security measures may include fencing at the water line, or fencing of a larger surrounding area. Dumping, litter, or inappropriate use of reservoirs can also be limited through indirect means, such as providing limited access roads or trails in the reservoir vicinity. While not preventing contamination, limiting access roads and trails can prevent large scale dumping (people can only pollute what they can carry), limiting pollution to litter or human waste, while allowing hiking or cycling recreation opportunities for community residents.
Managing reservoirs also includes creation of buffer zones to prevent off site contamination from reaching the reservoir. Buffer zones are zones of vegetation that filter or prevent off site spills and runoff from reaching the reservoir. These zones may be created by direct purchase and planting of vegetation on adjacent land, or through zoning laws that prohibit or limit development (thus using the land's natural existing vegetative filters). Buffer zones may also include structural controls such as storm water retention basins where runoff is collected and treated prior to being discharged or allowed to drain into groundwater. Retention basins prevent untreated storm water, which may contain sediment, oils and greases, pesticides, fertilizers, or debris, from reaching and contaminating the reservoir.
Pollution Prevention
In addition to the activities described above, local governments may be responsible for implementing or overseeing pollution prevention activities designed to prevent surface waters from being contaminated. These activities include limits or prohibitions of certain activities in protected areas, requirements for new construction, and public education. These activities are useful for both surface water and groundwater protection, and are described in more detail below.
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