SITE INFORMATION AND CORRESPONDENCE

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JOHN JOHNSON PAGE 2 to Maintaining High Quality of Waters in California) requires dischargers to cleanup releases impacting soil and groundwater to restore and/or protect groundwater to its original background levels. As the constituents of gasoline do not naturally occur in groundwater in this area,background levels are considered to be undetectable levels using the most stringent detection limits available. Please be advised that the remedial option chosen for this site must be capable of achieving this cleanup objective. PHS/EBD has determined the following deficiencies with respect to the Remediation Workplan. Section 1.2 and Section 4.1 The site background and contaminant information in the proposal is simplified and limited. It inadequately describes the scope of the known impacted area and fails to mention the impacted areas that still require assessment. Figures 1 and 2 are based on limited groundwater data from the last phase of field work and may not be entirely accurate. Groundwater monitoring wells must be installed to the north of monitoring wells MW#1 and MW#4 to determine the full extent of the groundwater contaminant plume in these directions. A monitoring well must be installed in the area between monitoring wells MW#1 and MW#3 as this area has no current data point to monitor the groundwater plume. Depending on the results of groundwater sampling from this well, an additional well may need to be installed to the southwest to determine the full extent of the plume in this direction. The simplicity and lack of geological and geochemical detail in these figures is alarming and indicate the need for additional physical data. Once this data is obtained, it is important that any discussions, assumptions,justifications and pictorial presentations based on the data is prepared by an appropriately qualified professional in an acceptable report format. An acceptable reporting format can be found in the Tri-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites-Appendix A (enclosed). It is not the geometry of the soil and groundwater plumes that is important but it is the concentrations ✓ and distribution of hydrocarbons within the complex strata of unsaturated and saturated soils underlying the site that is important. The concentrations and distribution of hydrocarbons in the soil at the site has not yet been definitively determined with physical data. This soil assessment is an absolute requirement and must be completed at this site. Section 4.2 The effectiveness of bioremediation at underground storage tank sites has been shown to be dependant on several complex site specific environmental and chemical factors. The statement made in this section on the sandy soils of this site is in error. The soil boring logs do show that some areas have sandy soils but, overall the soil lithology is much more complex and, as mentioned previously, not completely known. Written approval from the Central Valley Regional Water Quality Control Board is required before any substance can be introduced into the soil and/or groundwater at this site. The Regional Water Quality Control Board may require a permit to introduce the bacteria to ground and may also impose additional monitoring requirements. San Joaquin County well standards specify the construction and destruction standards for soil borings and monitoring wells. Any temporary soil borings used for the infiltration of bacteria would not be allowed to stay open overnight and must be destroyed as soon as the infiltration process is complete. All soil borings or monitoring wells must be destroyed with a neat cement grout. The construction of the proposed