DESCRIPTION: THE TRI-COUNTY/LANDFILLS ARE FUNCTIONALLY ONE CONTINGUOUS DISPOSAL UNIT WITH SEPARATE OWNERSHIP AND OPERATING HISTORIES. THE SITE TOTALS APPROXIMATELY 66 ACRES OF WHICH ALL BUT ABOUT 4 ACRES CONTAINS FILL MATERIAL. THE SITE ACCEPTED SOILD AND LIQUID COMMERCIAL/INDUSTRIAL WASTE FROM 1961 THROUGH 1976. ALTHOUGH SOME RECORDS OF WASTE TYPE AND QUANTITIES EXIST FOR THE TRI-COUNTY LANDFILL, LOCATION OF HAZARDOUS WASTE DISPOSAL IS NOT KNOWN FOR EITHER LANDFILL IN 1984, THE U.S. EPA DETECTED VOLATILE ORGANIC COMPOUNDS (VOCS) IN GROUNDWATER MONITORING WELLS DOWNGRADIENT OF THE SITE. APPROXIMATELY, 10,000 RESIDENTS WITHIN 3 MILES OF THE SITE USE GROUNDWATER AS THEIR SOURCE OF DRINKING WATER. ENFORCEMENT HISTORY: * PLACED ON NPL - 03/31/1989. * RECORD OF DECISION (ROD) SIGNED - 09/30/1992. SELECTED AN IMPERMEABLE LANDFILL CAP WITH AN ACTIVE LANDFILL GAS COLLEC- TION SYSTEM AND GROUNDWATER EXTRACTION AND TREATMENT. * EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD) - 06/25/1996. DEFERRED DESIGN AND IMPLEMENTATION OF GROUND WATER EXTRACT- ION AND TREATMENT COMPONENT OF REMEDY TO ALLOW A 5-YEAR PERIOD OF MONITORING TO EVALUATE EFFECTIVENESS OF CAP AND GAS COMPONENTS ALONE IN REDUCING GROUND WATER CONTAMINATION. * FINAL REMEDIAL DESIGN FOR LANDFILL CAP APPPROVED - 09/30/ 1997. COVER PROFILE CHANGED FROM THAT SPECIFIED IN ROD TO ENSURE LONG-TERM EFFECTIVENESS, AND