A 10-YEAR PERFORMANCE EVALUATION OF THE NEW CASTLE COUNTY, DELAWARE WATER RESOURCE PROTECTION AREA ORDINANCE

摘要

Researchers at the University of Delaware utilized GIS techniques to evaluate the performance of the decade-old New Castle County Water Resource Protection Area (WRPA) ordinance. The New Castle County WRPA ordinance was the first wellhead protection ordinance in Delaware and is designed to protect the quantity and quality of ground and surface water supplies in the First State's most populous county. The WRPA ordinance limits new development in mapped aquifer recharge, wellhead, reservoir watershed, and limestone formation areas to a maximum 20 percent impervious cover to protect water supplies. Utilizing percent impervious cover estimates as a measurable indicator, the research attempts to evaluate the effectiveness of the WRPA ordinance in limiting new development to protect underlying drinking water supplies. Using overlay techniques, the WRPAs were mapped utilizing Arc View shape files to calculate the area and extent of existing development within the WRPAs. Then the researchers computed the existing percent impervious cover (roof and pavement area) within the WRPAs and compared these values to the 20 percent impervious ordinance threshold set by the UDC. The analysis indicated that 138 new developments were proposed in the WRPAs since the ordinance went into effect in 1991. The overall impervious cover of the 89 square miles of WRPAs in New Castle County is 15 percent impervious ranging from 7 percent to 8 percent in Recharge and Hoopes Reservoir Areas to 41 percent in the Class A Transient/Noncommunity Wellhead areas. This research was performed in the UDWRA's capacity as one of seven appointed members of the New Castle County Resource Protection Area Technical Advisory Committee (RPATAC).