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PUBLIC HEALTH SERVICES co SAN JOAQUIN COUNTY < _-� :t JOGI KHANNA M.D.,M.P.H. Health Officer P.O. Box 2009 0 (1601 East Hazelton Avenue) •Stockton, Califomia 95201 (209) 468-3400 JOHN JOHNSON THE CUSTOMER COMPANY FEB 2 4 1993 P O BOX 886 BENICIA CA 94510 RE: 15 EAST GRANT LINE ROAD SITE CODE: 1404 TRACY CA San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has recently completed a comprehensive review of the activities to date at the above noted site. The following comments are based on that review and on the workplan for additional soil borings/grab water samples, dated December 4, 1992, and submitted by Parker Environmental. Based on the data collected to date for the soil and the groundwater, further investigation needs to be completed to fully define the extent of the contamination at this site. The following comments address the soil contamination: The soil samples obtained after the 1988 over-excavation activities indicate the soil contamination in the areas to the west and to the southwest of the former tank pit area has been effectively removed during the over-excavation. The soil samples obtained to the south and to the southeast of the former over-excavated area indicate residual soil contamination to be present. The full extent of the contamination in this area still needs to be determined and is not being addressed in the current workplan. This area must be addressed, either during this next scheduled phase of field work or in the following phase of field work when additional monitoring wells are to be installed. The presence or absence of residual soil contamination in the areas to the north, northwest and the northeast of the former tank pit area has neither been identified nor confirmed with soil samples. These areas appear to be addressed in the current workplan. The following comments address the groundwater contamination: The last round of groundwater sampling at this site indicates that at least three of the four wells have been impacted by hydrocarbons. Monitoring well #2 was obstructed and could not be sampled. Monitoring well #4 presented free petroleum product when it was monitored. Therefore, additional monitoring wells must be installed until the full extent of the groundwater contaminant plume is determined. Although monitoring wells are not proposed in this current workplan, the results from this phase of field work should allow for a more effective placement of the required additional monitoring wells. A Division of San Joaquin County Health(are Scrvices 10