SITE INFORMATION AND CORRESPONDENCE

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CLEANUP AND ABATEMENT ORDER NO. -2_ ° FOR DALLAS CORP. , DBA OVERHEAD/LODI DOOR COMPANY LODI , SAN JOAQUIN COUNTY the California Code of Regulations. Therefore, the waste was classified as hazardous, with nickel and zinc as the hazardous constituents. 8. The impoundment was found to be subject to the Toxic Pits Cleanup Act (TPCA) , Health and Safety Code, Section 25208 et seq. in November 1985. 9. As of 8 November 1985, wastes were no longer discharged to the impoundment. The Discharger completed the surface impoundment closure in November 1990 according to a closure plan approved by DHS (lead agency for closure of the n impoundment) and the Board. The Discharger satisfied the requirements of ILIJJI' the TPCA and was removed from the program as of 31 December 1990. 10. Six monitoring wells were installed at the facility. Wells MW-1, MW-2, and MW-3 were installed at the end of 1985, MW-4 in 1987, MW-6 in 1988, and MW-5 in 1989. Wells MW-1 through MW-5 were installed in the first water bearing zone, and MW-6 was installed in the second, deeper, water bearing II��JJ�UUU1 zone. The shallow wells are 63 feet deep (with the exception of MW-4 which is 57 feet deep) and the deeper well is 125 feet deep. 11 . MW-4 was dry during the third and fourth quarter 1991 sampling events. The other four shallow wells contained three to five feet of water. If the water table continues to drop, the wells will no longer be effective for p monitoring ground water. 12. Concentrations of nickel in the shallow ground water were originally as high as 90 µg/1 . Nickel has dissipated or migrated beyond the well influence to where it is no longer detectable in most of the wells above concentrations of 5 µg/l with the exception of MW-5. MW-5 has had nickel concentrations ranging from 7 to 12 µg/l within the last year. The proposed primary Maximum Contaminant Level (MCL) for Nickel is 100 ug/l . 13. Concentrations of chromium in the upgradient well , MW-4, have remained at or below detection limits. Wells MW-1 and MW-2 are downgradient from the impoundment. The concentration of chromium in MW-1 was 80 µg/l when the �' well was first analyzed in December 1985. The levels of chromium have fluctuated since that time. However, chromium concentrations have generally remained above the primary MCL of 50 ug/l in MW-1 and periodically in MW-2 since March of 1989. The maximum concentrations of total chromium reported in MW-1 and MW-2 were 130 and 81 4g/1 , respectively. 14. A Ground Water Monitoring and Reporting Program, Order No. 90-804, was issued to the Discharger in June 1990. The Order requires quarterly monitoring of all wells at the facility. Analysis for hexavalent chromium was added to the monitoring program in October 1990. 15. The primary MCL for chromium applies to total chromium in drinking water and does not distinguish between trivalent and hexavalent chromium. Hexavalent chromium is of greater concern because it is more mobile and