| Potential contamination of groundwater and surface water from the discharge of septic effluent has been identified as a concern in the Town of Beverly Shores in the Indiana Dunes region. The approximately 1,000 full- and part-time residents rely on individual septic systems as their means for domestic wastewater disposal and on residential wells as their water source. The highly permeable dune-sand soils and generally shallow groundwater with short flow paths to surface waters are conducive to pollution through the release of household wastewater from septic systems to the environment.; In an effort to evaluate the degree and extent of local groundwater contamination from septic-effluent discharge, two rounds of sampling of domestic water-supply wells for indicator parameters (coliform bacteria, nitrate, ammonia, chloride, sulfate, electrical conductivity, pH, dissolved oxygen, and detergent surfactants) at about 70 residences were undertaken in the autumn of 1993 and the spring of 1994. An analysis of those data indicates that areas of noticeable, but limited, impacts from septic effluent exist in the town and that they are generally associated with the more highly developed areas. Exceedances of health-related drinking-water standards for coliform bacteria and nitrate were localized, suggesting failure of some septic systems. Statistical analyses of the data suggest that higher septic-system density, thinner unsaturated zones, the use of water treatment systems, and the use of dry wells to discharge septic effluent increase the impacts on groundwater quality from septic-effluent discharge.; More detailed studies of water quality and hydrologic conditions were conducted at specific residences located in typical hydrogeomorphic settings within the town. The data from those site-specific studies suggest that local effects from septic systems may be very pronounced, since frequent exceedances of drinking water standards occurred at two of the three sites studied. Consistent with the larger-scale monitoring, unsaturated zone thickness and the use of water treatment appear to be important characteristics that affect groundwater quality near septic-effluent discharges. In addition, potential adverse effects of improper design, construction, or maintenance of septic systems are suggested by the spatial and temporal distribution of septic-effluent indicator parameters in the groundwater at one of the sites. |
