Monitoring Ground‐Water Quality Near a Sanitary Landfill

At the Hagman Road Landfill refuse is buried in lacustrine and glacial till deposits consisting mainly of silty clays. These clays overlie a thick carbonate aquifer used locally for water supply. The dominant direction of ground‐water flow is vertically down. Time of groundwater travel from the refuse to the aquifer is estimated at 12 years, putting first arrivals in 1978. Water quality monitoring of bedrock waters shows decreases in total dissolved solids, sulfates, calcium, magnesium, chlorides, and total hardness with increases in alkalinity to exist locally beneath the landfill. The principal chemical reaction felt to explain some, but not all of the water quality changes is sulfate reduction. Theoretical geochemical modellings help to support this interpretation. The landfill is hypothesized to have either triggered or accelerated sulfate reduction by creating the reducing environment.