THE MEW SITE IS LOCATED IN SANTA CLARA COUNTY IN THE CITY OF MOUNTAIN VIEW, CALIFORNIA. THE MEW SITE CONSISTS OF TWO NATIONAL PRIORITY LIST ( NPL ) SITES, ONE PROPOSED NPL SITE, SEVERAL NON-NPL SITES, MOFFETT NAVAL AIR STATION (ANOTHER NPL SITE), AND NASA AMES RESEARCH CENTER, ALONG WITH LIGHT INDUSTRIAL, COMMERCIAL, AGRICULTURAL, RESIDENTIAL, AND MUNICIPAL LAND USES. VARIOUS OWNERS OR OCCUPANTS IN THE AREA AROUND THE INTERSECTION OF MIDDLEFIELD ROAD, ELLIS STREET, WHISMAN ROAD, AND THE BAYSHORE FREEWAY (U.S. HIGHWAY 101) ARE OR WERE INVOLVED IN THE MANUFACTURE OF SEMICONDUCTORS, METAL FINISHING OPERATIONS, PARTS CLEANING, AIRCRAFT MAINTENANCE, AND OTHER ACTIVITIES REQUIRING THE USE OF A VARIETY OF CHEMICALS. SIGNIFICANT QUANTITIES OF VOLATILE ORGANIC CHEMICALS WERE USED FOR DEGREASING, PROCESS OPERATING, AND GENERAL MAINTENANCE. PRODUCT AND WASTE SOLVENTS AND OTHER CHEMICALS WERE PIPED AND STORED IN UNDERGROUND TANKS, PIPELINES, AND SUMPS. CHEMICAL RELEASES OCCURRED, FOR THE MOST PART, BELOW THE GROUND SURFACE AND MIGRATED DOWNWARD INTO THE AQUIFER SYSTEMS. THE PRESENCE OF THESE CHEMICALS IN THE SUBSURFACE SOILS AND GROUNDWATER IS PRIMARILY THE RESULT OF LEAKS FROM THE SUBSURFACE TANKS AND LINES, SUMPS, CHEMICAL HANDLING AND STORAGE AREAS, AND UTILITY CORRIDORS. DURING 1981 AND 1982, SEVERAL OWNERS