WORK PLANS - Laserfiche WebLink

Home Browse Search

r Environmental Mr.Harlin Knoll Resources 24 March 2010 Management Page 3 Regulatory drinking water standards for TPH-G (and petroleum in general) have not been developed. TPH-G and lower concentrations of aromatic hydrocarbons benzene, toluene, ethylbenzene, and total xylenes (collectively, BTEX, which do have regulatory standards for drinking water), are currently found in only 3 of the 8 wells onsite (MW-1, MW-4, and MW-6). Graphs depicting long term data trends for TPH-G and BTEX constituents were provided in our report entitled 2009 Annual Ground Water Monitoring Results. Although hydrocarbon concentrations have decreased dramatically since the removal of the USTs, it is evident that the natural attenuation processes are slow at this site and that it will take many more years for groundwater to ultimately reach water quality goals within these 3 wells. As we discussed during our recent telephone conversation, in the matter of a 1998 petition for a similar UST site (Walker vs. Napa County Department of Environmental Management (Order WQ98-04UST)), the State Water Resources Control Board (SWRCB) found that even if the requisite level of water quality has not yet been attained, a site may be closed if the level will be attained within a reasonable period (SWRCB Resolution 9249, III.A), and that a "reasonable period" may be decades to hundreds of years. Heinz does not believe that there are any significant increasing chemical trends or new receptors that have not already been evaluated and addressed that would require implementation of a remedial technology as referenced in your comment. Comment 5) The potential for residual petroleum hydrocarbon in soil and groundznater to migrate into nearby buildings and/or other receptors must be evaluated and reported to the EHD. Response to Comment 5) The evaluation of human health risk was provided in the Underground Storage Tank Closure Report dated 7 April 2000, which included site-specific risk based screening levels (RBSLs) for groundwater to be protective of indoor air. The RBSLs are summarized on the attached Table 1, along with the current groundwater concentration data from the Tank 1 and Tank 2 areas of the site. All of the current chemical concentrations are below these site-specific RBSLs. In addition, in 1997, the San Francisco Bay Regional Water Quality Control Board developed Environmental Screening Levels (ESLs; presented in Screening for Environmental Concerns at Sites with Contaminated Soil and Groundzvater, Revised May 2008) for a variety of