U.S. EPA ISSUED TWO CERCLA 106 UAOS TO SIX MAJOR PARTIES CONNECTED WITH THE POWELL ROAD LANDFILL SITE/DAYTON, OHIO. IMPACT: ON MAY 6, 1998, U.S. EPA ISSUED TWO SEPARATE CERCLA SECTION 106 UAOS TO 6 MAJOR CONTRIBUTORS OF HAZARDOUS SUB- STANCES TO THE POWELL ROAD NPL SITE, LOCATED OUTSIDE OF DAYTON, OHIO. THE FIRST UAO REQUIRES THE RESPONDENTS TO CONSTRUCT AND IMPLEMENT THE 100% FINAL APPROVAL REMEDIAL DESIGN FOR THE SITE, AND TO DESIGN, CONSTRUCT, AND IMPLEMENT AN ON-SITE LEACHATE TREATMENT SYSTEM WHEN SO DIRECTED IN THE FUTURE BY U.S. EPA. THE SECOND UAO REQUIRES THE RESPONDENTS TO DESIGN, CONSTRUCT, AND IMPLEMENT A GROUNDWATER PUMP AND TREAT SYSTEM WHEN SO DIRECTED IN THE FUTURE BY U.S. EPA. THE TOTAL ESTIMATED COST OF THE CLEANUP IS $23,000,000. BACKGROUND: THE POWELL ROAD LANDFILL SITE IS NPL SITE. THE SITE IS A FORMER GRAVEL PIT THAT WAS CONVERTED TO A LANDFILL IN 1959 AND OPERATED UNTIL 1984. COMMERCIAL, INDUSTRIAL, AND DOMESTIC WASTES WERE DISPOSED OF AT THE SITE. THE ROD WAS SIGNED IN SEPTEMBER 1993. IN AN EXPLANATION OF SIGNIFI- CANT DIFFERENCES ( ESD ) U.S. EPA HAD AGREED TO DELAY IMPLE- MENTATION OF THE GROUNDWATER COMPONENT OF THE RECORD OF DECISION ( ROD ) REMEDY PENDING THE OUTCOME OF A GROUNDWATER STUDY. IF THE STUDY DEMONSTRATES THAT GROUNDWATER CONTAMI- NATION LEVELS ARE DROPPING AS A RESULT OF SOURCE CONTROL MEASURES, THEN U.S. EPA CAN USE THE STUDY RESULTS TO CHANGE THE ROD'S REQUIREMENTS REGARDING GRO