SITE INFORMATION AND CORRESPONDENCE

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M. Scott Mansholt -2- 2 August 2005 ChevronTexaco Crude Oil Management &Remediation (pumped through the OVP and TAOC pipelines) such as San Joaquin Valley crude or Kern River crude have API gravity values of 13 to 15 placing them in the asphaltic-base range of crude oil classification. Heavy crude oil and the primarily fine-grained geological materials (relatively low hydraulic conductivity)present in the subsurface results in crude oil mobility being very limited. According to the report, San Joaquin and Kern River crude oils, at ambient groundwater temperatures, are significantly more viscous than other petroleum products such as gasoline, diesel, and light crude oil. Thus, the high viscosity of the crude oil severely minimizes the mobility thus limiting its flow into a well. Significant reductions in viscosity are not achieved until heavy the unsaturated eated to greater than zo e and water table t0echnicalyF) Consequently,the conditions make removal from infeasible and/or not economically viable. In addition to providing a description of the dynamic processes for movement of the weathered crude oil in the subsurface,the relationship between the various components is expressed mathematically. By using numerical values for the different components of crude oil in soil and groundwater, i.e., size and permeability/porosity of the geologic materials (generally fine sand, silt and clay) the report discusses combined with the crude oil's specific gravity and viscosity, it was concluded that free product removal is limited. In general, the evaluation described a variety of alternatives to address remediation of the weathered crude oil in soil and groundwater under the conditions described. The methods described included: mass removal of petroleum-impacted soil, extraction of product floating on groundwater,pump and treat impacted groundwater, or leaving free product and/or elevated TPH concentrations in soil in place. In the event it is subsequently determined that the latter may be the only viable option, a plan for implementing in-place management/natural attenuation(i.e.,monitored natural attenuation) combined with regulatory controls could be included as part of the consideration for possible NFA site closure. We have the following comments: • A discussion of one or more viable remedial options may be applicable for the HPP sites and each will be considered on a site-to-site basis even though the source is the same (crude oil). Depth to groundwater, the extent and concentration of petroleum hydrocarbons present, and the variable subsurface conditions will be evaluated in conjunction with the petroleum-impacted soil. • When considering a site for a no further action(NFA) closure request, the justification for the remedial option(s) selected, if any, should be described. The request may include a narrative for the different processes being considered for the conditions observed; each site will be addressed accordingly. Prior to evaluating an NFA request for closure, regardless of the remedial option, soil and groundwater characterization must be complete and approved by Regional Board staff, and a Human Health Risk Assessment (LIRA)must be reviewed and approved.