SITE INFORMATION AND CORRESPONDENCE FILE 2

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California Tank Lines, Inc. Page 2 3105 South EI Dorado Street April 1, 2011 Stockton, California 95206 Natural Attenuation Analysis, which presents evidence that natural attenuation is a viable remediation alternative, was also included in the Taber report. Taber cites historical groundwater analytical data to demonstrate that concentrations of contaminants of concern have declined in monitoring wells MW-1 and MW-3. Taber notes that the groundwater analytical results from the advancement of soil borings SG-1 and SG-2 provide evidence that the impacted areas are limited to the regions around MW-2 and MW-4. Taber suggests that the recent increase in volume of free-product removed from MW-2, and the recent increase of concentrations of contaminants of concern in groundwater collected from MW-2 and MW-4, may be related to the simultaneous increase in groundwater surface elevations. The EHD has reviewed the trend charts presented in Figures 5 and 7 of the Taber report that show the groundwater elevations versus total petroleum hydrocarbon as diesel (TPH-D) concentrations in MW-2, and groundwater elevations versus TPH-G concentrations in MW-4, respectively, but a noticeable correlation between increasing groundwater elevation and increasing contaminant concentration in groundwater is not very evident. The EHD does approve Taber's recommendation to continue monitoring contaminant concentrations and water level elevation trends and prepare a Mann-Kendall analysis to track concentration trends and plume stability over time. In the Taber letter, the CAP consists of Taber proposing to utilize the United States Environmental Protection Agency (USEPA) BIOSCREEN model to simulate and assess monitored natural attenuation using historical groundwater data from MW-4, and thereby, project when water quality goals will be achieved. The EHD had directed by letters dated 12 January 2009, 03 March 2010, and 21 July 2010, submittal of a CAP that included evaluations of several methods for site remediation, and directed that contaminant mass estimates, supported by calculations, for sorbed and dissolved TPH-G, benzene, 1,2-dichloroethane (1,2- DCA), TPH-D, and total petroleum hydrocarbons as motor oil (TPH-MO) be included in the CAP as well as an analysis for cost-effectiveness for the recommended remedial technologies. The CAP, as submitted, does not fulfill the directives from this department and the EHD now directs that a revised CAP be resubmitted by 09 May 2011 that includes all the information noted in this paragraph. In the EI report, EI presents results from removing oil from MW-2 using absorbent socks to increase the removal of floating oil from MW-2. A stainless steel bailer containing GeoSorb sock was utilized in three different tests over a period of approximately three months. EI concludes that absorbent socks do not increase the rate of removal of oil from MW-2 since "it appears that the rate controlling step is the movement of oil through the soil." EI recommends removal of floating oil monthly, or as needed based on the quantity of free product present in MW-2, by employing a standard disposable bailer. The EHD concurs that absorbent socks do not appear to be effective for expediting the removal of heavy oil from MW-2, and instead recommends that you employ an oil skimmer, possibly with a heater to maintain liquid flow, to expedite oil removal from MW-2. Another suggestion would be to install additional wells, screened between approximately 17 and 37 feet bsg, in the tank pit area to accelerate free product recovery. Submit a work plan to the EHD by 02 June 2011, if utilization of an oil skimmer or installation of additional wells is determined to be a viable option to remove the heavy oil from MW-2. While exploring this option, the EHD concurs with the recommendation for removal of free product monthly, or as needed, from MW-2 using a disposable hand bailer.