THE BYRON SUPERFUND SITE (SITE) IS LISTED ON THE NATIONAL PRIORITIES LIST (NPL). THE SITE WAS FIRST LISTED ON THE NPL ON DECEMBER 30, 1982, 47 FED.REG. 58476. THE BYRON SUPERFUND SITE CONSISTS OF THE BYRON SALVAGE YARD (BSY) PROPERTY AND THE DIRKS FARM PROPERTY (DFP). THE CONTIGUOUS PROPERTIES ARE LOCATED IN RURAL OGLE COUNTY IN NORTHERN ILLINOIS, ABOUT HALFWAY BETWEEN THE CITIES OF BYRON AND OREGON, ILLINOIS. THE BSY IS LOCATED EAST OF RAZORVILLE ROAD AND THE DFP IS DIRECTLY WEST OF THE BSY ACROSS RAZORVILLE ROAD. SEE ATTACHMENT 1. THE SITE ORGINALLY WAS LIMITED TO THE BY BUT WAS EXPANDED TO INCLUDE THE DFP BASED ON THE EXTENT OF CONTAMINATION AND HISTORY OF DISPOSAL PRACTICES ON BOTH PARCELS. THE SITE HAS BEEN DIVIDED INTO FOUR OPERABLE UNITS. OPERABLE UNIT 1 WAS CONDUCTED TO LIMIT SITE ACCESS TO BSY AND PROVIDE RESIDENCES WITH BOTTLED WATER. OPERABLE UNIT 2 PROVIDED ADDITIONAL RESIDENCES WITH BOTTLED WATER AND THEN CARBON FILTERS. OPERABLE UNIT 3 INVOLVED CONCURRENCE WITH THE ILLINOIS ENVIRONMENTAL PROTECTION AGENCY'S (IEPA) DECI- SION TO PROVIDE A MUNICIPAL WATER SUPPLY TO THE AFFECTED RESIDENCES AND THE EXTENSION OF THE MUNICIPAL WATER LINE TO ADDITIONAL RESIDENCES. OPERABLE UNIT 4 ADDRESSES THE FINAL SOIL AND GROUNDWATER ACTION FOR THE SITE. THIS REPORT ADDRESSES THE GROUNDWATER COMPONENT OF OPERABLE UNIT 4 FOR BSY.