ABSTRACT

A flexible, phased approach to assessing the environmental conditions at a former landfill site should seek to: (1) define the landfill history and extent of landfill waste boundaries; (2) identify landfill gas generation, migration, and collection issues; (3) determine landfill leachate impacts to site surface water and ground water; and (4) adopt measures for implementation of possible viable, expedited, and cost-effective remedial actions.

The landfill was found to extend much farther north and west than expected, underlying several apartment complexes. Most degradable organic materials and the necessary methanogenic microorganisms were no longer present. Detected methane and hydrogen sulfide most likely are the result of residual entrapment by site hydrostratigraphy and fill-type materials. A combination of clay fill material, the building foundations, and paved areas produces a capping effect, thus preventing methane gas concentrations detected in the localized areas from venting to the atmosphere. Ground-water and surface water quality impacts resulting from leachate are negligible.

A landfill gas/ground-water monitoring well network was installed, which can be used for active or passive extraction of landfill gas. A remedial action report, prepared for the city, presented site remediation options based on the results of the assessment.