SITE INFORMATION AND CORRESPONDENCE

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ENVIRONMENTAL HEALTH DEPARTMENT "amu ' " ` SAN JOAQUIN COUNTY Unit Supervisors Donna K. Heran, R.E.H.S. 304 East Weber Avenue, Third Floor Carl Borgman, R.E.H.S. < Director Mike Huggins, R.E.H.S., R.D.I. AI Olsen, R.E.H.S. Stockton, California 95202-2708 Douglas W. Wilson, R.E.H.S. cP • Manager Program Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. 9CrFok g Laurie A. Cotulla, R.E.H.S. Robert McClellon, R.E.H.S. Program Manager Fax: (209) 464-0138 Mark Barcellos, R.E.H.S. LAWRENCE H BEASLEY 2120 PEBBLE DRIVE JUL 17 2003 ALAMO CA 94507 RE : Former Apache Plastics SITE CODE : 2313 2050 Fremont Street Stockton CA 95209 San Joaquin County Environmental Health Department (SJC/EHD) has reviewed the Work Plan Addendum dated October 1 , 2002 and the Site Conceptual Model dated September 24, 2002 that were submitted on your behalf by Stratus Environmental, Inc. and has the following comments. The addendum was written to address specific issues discussed by SJC/EHD in correspondence dated May 14, 2002. SJC/EHD recommends adjusting some screen depths as noted below to screen across specific sand intervals; final depths should be determined from samples collected while advancing the borings. SJC/EHD approves the addendum with the following noted conditions . 1 . SJC/EHD does not approve the installation of both down-gradient deep wells , noted in the addendum as MWA 3 and MWA 7. One well , at the proposed location of MW-17, is sufficient at this phase of the investigation to monitor the lateral extent of the plume at depth . MW-12, a deep -well that is proposed to be destroyed because it is compromised , has been non-detect for constituents analyzed over four quarters. 2. The installation of one shallow (screen interval from 40-60 feet bsg), one mid-zone (screen interval from 80-90 feet bsg ) and one deep-zone (screen interval from 110-120 feet bsg) groundwater monitoring well at the locations proposed southeast of CPT-10. 3. Monitoring well MW-3 will be destroyed by over drilling and replaced with a monitoring well screened in the deep zone from 100-120 feet bsg . 4. The proper destruction of manometer points MP-1 and MP-2 , vapor well VW-1 and monitoring well MW-12. 5. Analytical results from grab groundwater samples collected from CPT borings CPT-10 and CPT-11 indicate a possible highly contaminated water bearing sand interval at approximately 85-90 feet bsg. SJC/EHD recommends further investigation of this zone with conversion of VWA following destruction to a groundwater monitoring well discretely screened from 85-90 feet bsg , and installation of another well screened at this interval in the area of MW-2 and MW-8. 6 . Soil and groundwater samples from this phase of the investigation will be analyzed for TPHg , BTEX, fuel oxygenates , 1 ,2-DCA and ethylene dibromide; all peaks on the EPA Method 8260 run will be reported .