U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 02-4282
Prime Hook National Wildlife Refuge is located in southeastern Delaware in coastal low-lands along the margin of Delaware Bay. For 37 years, the Broadkiln Sportsman's Club adjacent to the refuge operated a trap-shooting range, with the clay-target launchers oriented so that the expended lead shot from the range dropped into forested wetland areas on the refuge property. Investigators have estimated that up to 58,000 shotgun pellets per square foot are present in locations on the refuge where the lead shot fell to the ground.
As part of the environmental risk assessment for the site, the U.S. Geological Survey (USGS) investigated the potential for lead contamination in ground water. Results from two sampling rounds in 19 shallow wells indicate that elevated levels of dissolved lead are present in ground water at the site. The lead and associated metals, such as antimony and arsenic (common shotgun pellet alloys), are being transported along shallow ground-water flowpaths toward an open-water slough in the forested wetland adjacent to the downrange target area. Water samples from wells located along the bank of the slough contained dissolved lead conentrations higher than 400 micrograms per liter, and as high as 1 milligram per liter. In contrast, a natural background concentration of lead from ground water in a well upgradient from the site is about 1 microgram per liter. Two water samples collected several months apart from the slough directly downgradient of the shooting range contained 24 and 212 micrograms per liter of lead, respectively.
The data indicate that lead from a concentrated deposit of shotgun pellets on the refuge has been mobilized through a combination of acidic water conditions and a very sandy, shallow, unconfined aquifer, and is moving along ground-water flow- paths toward the surface-water drainage. Data from this study will be used to help delineate the lead plume, and determine the fate and transport of lead from the source area.
Purpose and scope
Methods of study
Water sample collection and analysis
Soil and sediment sampling
Summary and conclusions
Appendix: Prime Hook core lithologic descriptions
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For more information about USGS activities in Maryland, Delaware and the District of Columbia contact:
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Baltimore, MD 21237
Telephone: (410) 238-4200
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or access the USGS Water Resources of Maryland, Delaware, and District of Columbia home page at: http://md.water.usgs.gov/.
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Last modified: Thursday, September 01 2005, 02:22:06 PM