BECAUSE OF THE DEFERRED GROUNDWATER COMPONENT, THIS SITE MAY NOT STRICTLY QUALIFY AS A CONSTRUCTION COMNPLETION UNTIL THE GROUNDWATER COMPONENT IS EITHER CONSTRUCTED RO ELIMINATED. THE GROUNDWATER CONTAMINATION AT THE SITE WILL BE ADDRESSED BY NATURAL ATTENUATION, ONCE THE PLACEMENT OF THE LANDFILL CAP AND ACTIVE LANDFILL GAS COLLECTION SYSTEM IS COMPLETED. A SUBSEQUENT RECORD OF DECISION (ROD) AMEND- MENT WILL BE REQUIRED IN THE EVENT THAT NATURAL ATTENUATION IS ACCEPTED AND FINALLY CHOSEN AS THE FINAL TREATMENT FOR THE CONTAMINATED GROUNDWATER. THE TRI-COUNTY/ELGIN LANDFILLS ARE FUNCTIONALLY ONE CON- TIGUOUS 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 SOLID 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 DISPOSA IS NOT KNOW 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. THE ELGIN LANDFILL CURRENTLY ACCEPTS CONSTRUCTION AND LAND- SCAPING MATERIALS. SEVERAL SMALL BUSINESSES ARE LOCATED AT THE EASTERN EDGE OF THE SITE. THERE