Evaluating Options for Changing Groundwater Monitoring Requirements for Landfills to Reduce Mercury Used by Laboratories

Executive Summary: The State of Wisconsin requires aqueous environmental samples at solid waste landfills to be tested for chemical oxidation demand (COD). The typical COD analytical method generates toxic waste that includes mercury, chromium, and silver. The Wisconsin Department of Natural Resources (WDNR), in an effort to reduce mercury and other toxic metals waste, initiated this study to determine the effectiveness of COD monitoring, whether COD analyses can be replaced with an effective and less polluting alternative, or eliminated without sacrificing the ability to detect groundwater contamination from landfills.

The study was divided into three phases. Phase I determined the usefulness of COD for detecting groundwater contamination from landfills. Phase I] determined if other required monitoring parameters would identify groundwater pollution if COD was not used. Landfills selected for study in Phases I and II had known contamination problems. Phase III compared of other non-required analyses or combination of analyses to determine if they could detect groundwater contamination and redox condition with less environmental impact than COD. Analyses selected for the side-by-side comparison with COD included: redox potential (Eh), manganese (Mn), iron (Fe), ammonium (NHzg4), dissolved organic carbon (DOC), Hach Mn III COD, and dissolved oxygen (DO).

Based on the evaluation performed in Phases I and II, twenty-four landfills were selected as possible sites for field study. These sites included 14 municipal solid waste (MSW), 6 paper mill sludge, 1 demolition waste, 1 municipal solid waste combustor ash, | fly/bottom ash, and 1 foundry landfill. Landfill types represented by only one site were eliminated from Phase III field sampling for statistical purposes, leaving MSW and paper mill sludge landfills. Samples were collected in the spring and fall of 2000 at 12 municipal solid waste and 6 paper mill landfills. Sites selected for the study have at least one up-gradient and three downgradient groundwater monitoring wells. Phase III did not include leachate and lysimeter samples.