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Hydrologic and water-quality data were collected in northern Bucks County, Pa., as part of a study conducted by the U.S. Geological Survey, in cooperation with Bridgeton, Buckingham, Nockamixon, Plumstead, Solebury, Springfield, TLnicum, and Wrightstown Townships and New Hope Borough. Hydrologic data on ground water and surface water were collected to provide basic information on the quality and quantity of water resources in northern Bucks County. Groundwater data include descriptions of 1,357 wells and water levels for 28 observation wells measured during 1990-93. Ground-waterquality analyses for 117 wells include physical properties and concentrations of major ions, nutrients, selected metals and other trace constituents, radon, and volatile organic compounds. Surface-water data include chemical analyses of water samples collected at sites on Beaver Creek, Cooks Creek, Geddes Run, Little Tinicum Creek, Paunnacussing Creek, Pidcock Creek, Rapp Creek, Smithtown Creek, and Tinicum Creek. O M C_<0 M C i 3 M IO SI ' 3 c 3 o.

Valley Forge National Historical Park is just southwest of the Commodore Semiconductor Group (CSG) National Priorities List (Superfund) Site, a source of volatile organic compounds (VOC's) in ground water. The 7.5-square-mile study area includes the part of the park in Lower Providence and West Norriton Townships in Montgomery County, Pa., and surrounding vicinity. The park is underlain by sedimentary rocks of the Upper Triassic age Stockton Formation. A potentiometric-surface map constructed from water levels measured in 59 wells shows a cone of depression, approximately 0.5 mile in diameter, centered near the CSG Site. The cone of depression is caused by the pumping of six public supply wells. A groundwater divide between the cone of depression and Valley Forge National Historical Park provides a hydraulic barrier to the flow of ground water and contaminants from the CSG Site to the park. If pumping in the cone of depression was to cease, water levels would recover, and the groundwater divide would shift to the north. A hydraulic gradient between the CSG Site and the Schuylkill River would be established, causing contaminated ground water to flow to the park. Water samples were collected from 12 wells within the park boundary and 9 wells between the park boundary and the groundwater divide to the north of the park. All water samples were analyzed for physical properties (field determinations), nutrients, common ions, metals and other trace constituents, and VOC's. Water samples from the 12 wells inside the park boundary also were analyzed for pesticides. Concentrations of inorganic constituents in the water samples did not exceed U.S. Environmental Protection Agency maximum contaminant levels. Very low concentrations of organic compounds were detected in some of the water samples. VOC's were detected in water from 76 percent of the wells sampled; the maximum concentration detected was 5.8 micrograms per liter of chloroform. The most commonly detected VOC was chloroform. The second most commonly detected compound was methyl tert-butyl ether (MTBE), which was detected in water from 24 percent of wells sampled. Several pesticides were detected in water samples collected from within the park boundaries: chlordane, DDD, dieldrin, endrin, heptachlor epoxide, and simazine. Concentrations of the detected pesticides were 0.1 micrograms per liter or less and did not exceed U.S. Environmental Protection Agency maximum contaminant levels.

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