Ground-water monitoring in support of non-point source nutrient TMDLs,Coastal Sussex County, Delaware

摘要

Delaware’s Department of Natural Resources and Environmental Control (DNREC) is conducting anrnassessment of ground-water quality in the Indian River, Indian River Bay, and Iron Branch watersheds located inrnSussex County, Delaware, to support non-point source nutrient Total Maximum Daily Loads (TMDLs). Groundwaterrnsamples are collected from existing wells completed in the unconfined aquifer and analyzed to assess thernoccurrence and distribution of major ions and nutrients.rnPreliminary analytical data for 81 samples1 collected from November 2001 through August 2002 indicaternthat the mean nitrate concentration, 8.25 milligrams per liter (mg/L) as nitrogen, is less than the U.S.rnEnvironmental Protection Agency’s Maximum Contaminant Level (MCL) of 10 mg/L as nitrogen in drinkingrnwater. Nitrate exceeds the U.S. Environmental Protection Agency’s MCL in 19 of 81 samples, and these 19rnsamples were collected at depths ranging from 10 to 80 feet below land surface. Nitrate concentrations greaterrnthan 20 mg/L as nitrogen were found in 3 of 81 samples. Although phosphorus has not been detected above the