Delawareâs Inland Bays in southeastern Sussex County are valuable natural resources that have been experiencing environmental degradation since the late 1960s. Stresses on the water resource include land use practices, modifications of surface drainage, ground-water pumping, and wastewater disposal. One of the primary environmental problems in the Inland Bays is nutrient over-enrichment. Nitrogen and phosphorous loads are delivered to the bays by ground water, surface water, and air.
Water supply in the rapidly developing Lewes and Rehoboth Beach areas of coastal Sussex County in Delaware is provided by more than 80 individual public water wells and hundreds of domestic wells. Significant concerns exist about the future viability of the ground-water resource in light of contamination threats and loss of recharge areas. As part of Delaware's Source Water and Assessment Protection Program, wellhead protection areas (WHPAs) were delineated for the 15 largest public supply wells operated by three public water systems.
In June 1996, the U. S. Environmental Protection Agency (USEPA) proposed a regulation to require individual states to develop Pesticide Management Plans (PMPs) to protect their ground-water resources from pesticide contamination. The USEPA designated the predominantly agricultural pesticides atrazine, alachlor, cyanazine, metolachlor, and simazine as the first five that would require a PMP.
Water samples were collected from 63 wells in southern New Castle County to assess the occurrence and distribution of dissolved inorganic chemicals in ground water. Rapid growth is projected for the study area, and suitable sources of potable drinking water will need to be developed. The growth in the study area could also result in degradation of water quality. This report documents water quality during 1991-92 and provides evidence for the major geochemical processes that control the water quality.
Several common herbicides used on corn and soybeans were detected in ground water at two agricultural sites in Delaware as part of a study of the distribution of herbicides in shallow ground water and the environmental factors affecting their occurrence.
Subsurface temperatures were measured in instrumented boreholes for about one and one-half years at depths down to 10 feet below land surface at four locations in the State. In New Castle County, temperatures were measured periodically in the field about twice a month at three sites, and, in Sussex County, they were automatically recorded every 15 minutes at one site. The depths of interest are generally in the unsaturated zone and are subject to both daily temperature fluctuations and longer seasonal changes.
The unconfined aquifer is a major source of water supply in eastern Sussex County, Delaware. It also is an important source of water for surface-water bodies and deeper, confined aquifers. The aquifer consists mainly of permeable sand and gravel; its shallow water table is susceptible to contamination by nitrate and other chemical constituents associated with agricultural practices and effluent from septic systems.
This study has evaluated pre-treatment and physical and geochemical components of rapid infiltration basin systems (RIBS). The project was begun in 2008 with an evaluation of performance of treatment plants associated with RIBS in Delaware, Massachusetts, North Carolina, and New Jersey. Field and simulation evaluations of a RIBS located at Cape Henlopen State Park were completed in 2011. Simulation studies of infiltration and nitrogen cycling in the vadose zone were completed in early 2013. Multiple conference presentations, reports, and articles are now being released.
In view of the possible need for disposal of low-level radioactive waste in Delaware under the Nuclear Waste Policy Act of 1982, the Delaware Geological Survey has prepared this report to assist the citizens of our State in understanding this complex subject. Emphasis here is on geologic and hydrologic aspects of disposal. Health, social, and economic factors are outside the scope of this report and are not discussed. However, they are very important integral parts of the safe disposal of low-level radioactive waste, and must be considered when selecting suitable disposal sites.