Agenda - 05-05-1997 - 9c - Laserfiche WebLink

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12 ` S. Characterize the chemical quality of the County's ground water. If ground water is to continue to serve as a major source of potable water for Orange County residents,the quality of the water must be assured. In the Piedmont region of North Carolina, water supply problems generally involve quantity rather than quality. However,the project team will compile and map existing information of ground-water quality and pollution sources in the County and will develop and assist with implemeatatioa of a local well testing program which will enable the County to assemble the data necessary to formulate public information and land use policies. The expense involved in performing a detailed analysis of water quality dictates the necessity to limit this part of the investigation. Rather than test for all of the pollutants that could be found in ground water,tests will only be made for pollutants common to Orange County and in areas characterized by rural development. Nitrogen compounds and bacteria common to human and animal wastes are likely in an area characterized by agriculture and rural populations dependent on septic tanks. Furthermore,the agricultural nature of the County indicates the possible Presence of pesticidVIieftode residues. Screening tests will be conducted for the most likely pesticide/herbicide components. Screening techniques that enable the testing for selected constituents can provide general water-quality information and indicate possible problem areas without requiring great expense. In addition,existing data on water quality can provide a baseline level which can be compared to data generated by earlier or later water-quality tests to show a change in water quality. The project staff will compare newly obtained water quality data with data that will be obtained from various State and County agencies which are and have been traditional collectors and repositories of water quality and pollution data. The project staff will evaluate ground-water quality by collecting ground-water samples and performing chemical analyses. Samples will be collected at well sites selected according to a stratified sampling plan based on hydrogeologic units and the area of each unit in the county. Well sites within each unit will be selected to provide uniform areal coverage. As in the case of the ground-water quantity investigation,samples also may be drawn from wells in adjacent counties. About SO of the invootoded wells will be sampled to characterize the wafer quality of the major hydrogeologic units in the County. All SO wells will be sampled for specific conductance, pH,temperature,major ions,nutrients(including nitrate),and will be screwed for BTEX (organic compounds associated with gasoline)and selected pesticides using immunossaay methods(contingent on availability of pesticide-specific immunoassay kits). About 30 of these 50 wells will be sampled for radon and trace elements. All laboratory analytical results will be compiled and stored in WATSTORE data bases. Natural water quality,or those water-quality parameters not resulting from man-made pollution,such as hardness and iron,corrosivity,manganese and silica concentrations, determines the desirability of ground water as a source for human consumption. Radon can also occur at undesirable levels in ground water,especially in areas underlain by fiesic igneous or metamorphic rocks. Elevated levels of radon have recently been identified in nearby Guilford County which is underlain by crystalline rocks similar to Orange County. Maps of selected .. 8