AFTER THE EMERGENCY:THE DESIGN AND CONSTRUCTION OF A MODULAR ACTIVE GAS EXTRACTION SYSTEM FORMIGRATION CONTROL

摘要

In April 2000, at the abandoned KAV Company Landfillrnsite north of Kalamazoo, the Michigan Department ofrnEnvironmental Quality (MDEQ) and Malcolm Pirnie Inc.,rnhad detected up to 40% methane in soils beneath thernhomes of a rural, residential neighborhood. MalcolmrnPirnie designed and supervised the installation of anrnemergency perimeter landfill gas extraction system tornintercept and withdraw landfill gas at the propertyrnboundary, and within a year methane concentrations inrnsoils beneath the homes were non-detect. This case studyrnexamines the aftermath to the emergency response at thernKAV Company Landfill and provides an example ofrnfactors that influence remedial design, includingrntechnological, geologic, economic, and political.rnMalcolm Pirnie established a regular monitoring program,rncollecting subsurface gas and pressure data using CESLandtecrnGEM?-500 and GEM?-2000 instruments.rnBecause of the expanse of the monitoring network and therninfluence of the site’s glacial geology, the evaluation of thernpressure data had to consider the effects of barometricrnchanges throughout the monitoring period as well as a lagrneffect between the changing atmospheric and subsurfacernconditions. The pressure data were used to developrnisobaric maps and distance-drawdown curves to evaluaternthe effective radius of the system and verify that thernmigrating gas had been effectively intercepted at thernlandfill property boundary. Malcolm Pirnie developed methane concentration isopleths to track the dissipation ofrnthe landfill gas plume.rnTo maintain amicable relations with the local residents, thernMDEQ requested assistance from Malcolm Pirnie tornprepare presentations for public meetings to inform thernlocal populace about the project and to support requests forrnvariances when the remedial design could not strictlyrnadhere to township ordinances. Malcolm Pirnie workedrnwith the MDEQ to develop an alternative gas treatmentrnsystem (a carbon and reduced-sulfur media rather than anrnexpensive, noisy, and highly visible flare) and tornincorporate general aesthetics (a ten-foot wooden fence tornscreen equipment from the public eye and to ensure thatrnnoise levels at the property line were within townshiprnordinance limits) that would meet the project objectives,rnprovide a flexible, cost-effective system for the MDEQ,rnand satisfy the concerns of the local populace.rnEvaluation of data collected from the emergency systemrnled Malcolm Pirnie and the MDEQ to select a modularrnsystem design, which may be implemented in two phases.rnDuring Phase I, eight additional extraction wells werernnetworked to the existing system along the western andrnsouthern property boundaries – the observed gas migrationrndirection. Additional monitoring wells were installed tornassess and monitor subsurface gas quality off the propertyrnboundaries opposite the extraction system. Two 15-hprnblowers, with a maximum capacity of approximately 1,000rnscfm, were installed at a permanent blower station. Shouldrnsubsequent monitoring indicate a need to control migrating