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14 <br />C. ' Nutrients <br />Nutrients such as nitrogen and phosphorus are important to plant and animal <br />life, but higher concentrations of these nutrients can often threaten surface and <br />ground water supplies. Usually; increased levels of nutrients are the result of <br />human activity -the use of fertilizer ar manure, septic systems, or combustion of <br />fossil fuels. Nutrients in ground water usually take the form of nitrate, nitrite and <br />ammonia. In particular, a drinking water standard far nitrate (10 mg/L) is set to <br />protect against high levels, which are dangerous and can pose health risks of <br />anemia and other conditions for small children and the. infirm. <br />High concentrations of nutrients in County ground water may reflect excessive <br />human activity as mentioned above, or poor well construction. of the 51 wells <br />studied in the County, 82% of the samples contained nitrate. While there were <br />widespread findings of nitrate, most were of low concentration. The median <br />value of all wells sampled was 0.49. mg/L, although one well had a high reading <br />of ~.2 mg/L. All other wells sampled were below 3 mg/L. Ammonia and <br />orthophosphate were only detected at low concentrations. <br />D. Total Dissolved Solids <br />Dissolved solids measures the mass of solutes in a water sample after <br />evaporation. Higher or lower than average dissolved solids are indications of the <br />potential for scaling or clogging of plumbing from precipitate minerals. Dissolved <br />solids are generally lower in the Piedmont's crystalline rocks ,than in other <br />regions of the state and nation, and the median dissolved solids concentration in <br />the, County from the analysis is 125 mg/L. This level is typical of the Piedmont <br />.area of the southeastern U.S. <br />E. Metals and Trace Elements <br />Metals and trace elements were ~ detected infrequently in the County's well <br />sampling. Na trace elements exceeded the U.S. EPA's MCL's (maximum <br />contaminant levels), although some metals were found at levels worthy of note. <br />Zinc, manganese, iron and copper were the most frequently detected metals. <br />In three samples, the level of iron exceeded the level of N.C. drinking water <br />standards. Manganese exceeded drinking water standards in 12 of the 51 wells <br />sampled - and' in three cases both iron and manganese were exceeded. As has <br />been known for years, iron and manganese are sometimes a primary concern <br />with ground water supplies in the County, and cause significant water quality <br />nuisances in both the County and state. In excessive amounts, iron and <br />manganese can stain teeth, plumbing fixtures, skin or laundered products, and <br />also may cause odor or taste concerns. <br />Lead was detected in 8 of the 51 samples, although at levels below State and <br />Federal MCL. The levels were, however, greater than the zero-level goal that has <br /> <br />