Ground-water quality near a scavenger-waste-disposal facility in Manorville, Suffolk County, New York 1984-85

Abstract

Sludge from sewage-treatment plants and septic tanks was discharged to unlined infiltration basins at a scavenger-wastedisposal facility in Manorville, in south-central Suffolk County, during 1964-82, and solid waste was accepted during 1960-72. Three test borings were made at the site and groundwater samples collected in 1984 and 1985 to examine the effects of the waste on local groundwater quality in the upper glacial aquifer. The test borings reveal that 180 to 205 feet of well-sorted glacial outwash sediments overlie deposits of the Matawan Group and Magothy Formation, undifferentiated. A sandy facies of the Gardiners Clay may be present in the southern half of the 0.88square-mile study area. Observation wells were installed in clusters along flow lines hydraulically downgradient from the facility, and water samples were collected from 29 wells in 1984 and from 63 wells in 1985. Geochemical data indicate that a 1,300-foot-wide plume of contaminated water has moved 4,700 feet downgradient from the disposal site. Samples of plume water had higher specific conductance, lower dissolved-oxygen concentrations, and higher concentrations of dissolved solids, chloride, sodium, calcium, potassium, magnesium, and chlorobenzene than did samples from uncontaminated areas. The median background dissolved-solids concentration of 23 mg/L (milligrams per liter) in water from wells in areas unaffected by the plume is considerably lower than the median concentration of 190 mg/L for plume water, which indicates that dissolved-solids concentration and specific conductance are useful indicators of the plume's extent. Dissolved-iron concentrations in ground water are elevated for at least 1,400 feet downgradient from the site as a result of chemical (oxidation-reduction) alteration to the more soluble ferrous state. The geochemical condition of ground water near this facility shows general similarities and particular differences to previously studied landfills located in glacial outwash deposits.