Ground-water movement in the upper glacial aquifer in the Manorville area, Town of Brookhaven, Long Island, New York, in November 1983

Water levels in 52 wells near the Manorville scavenger-waste disposal facility in the Town of Brookhaven were measured in November 1983 to determine the direction and gradients of groundwater flow in the upper glacial aquifer. Groundwater moves south-southeastward (S22 degrees E) from the groundwater divide, about 6 miles north of the facility, to discharge points near East Moriches and beneath Moriches Bay. The hydraulic gradient beneath the disposal facility is 6.5 ft/mi (0.0012 foot/foot), and the rate of horizontal flow is 0.9 to 1.7 ft/day. Vertical movement of groundwater since closure of the disposal facility in 1982 is probably negligible because the vertical gradients are small and the upper glacial aquifer is anisotropic. During operation of the facility, however, groundwater mounding may have developed beneath the unlined settling basins, which could have induced downward movement of water in the upper glacial aquifer.