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vapors. Based upon this information it is our opinion that the soil vapor threat from the LIST contaminants is low. 2 7U AND (� s.RsnnWfiop�Fss, pa�rnmeter5 entenlatio s >lad Wgdgl used in any risk assessn nts CGROUND RL A, groundwater fate and transport model was not performed for this site. TFHD was detected at 51 ug/l in October 2009 and was not detected in September 2010 at MW-.l. The declining concentrations of the plume are interpreted as being due to site contaminant source removal and natural petroleum biodegradation processes of the dissolved plume. Z,;1$ Rationales why the conditions remaining at the site will not adversely impIct v_ater guali human health and safety and other beneficial uses, The underground fuel storage tank source and residual soil contaminants have been removed from the property. Groundwater monitoring events conducted in 2009 and 2010 documented a northwesterly groundwater flow direction away from nearby buildings. Reported concentrations of dissolved petroleum ;hydrocarbon constituents in the groundwater appear to have decreased markedly since the initial study conducted in 2j?03. A 2000-foot well search was conducted in 2008. That survey showed that there were d~inking water wells in the area but none located within the radius of search. The shallow aquifer in which the dissolved plume occurs is not known to be a drinking water aquifer nor is it used for any other water source to the available information. The nearest weds to the search radius are; a dairy well, Holly Sugar irrigation and industrial wells, Kennally domestic and a City of Tracy test well (see no. 2,3,6, 7, 8, 18 on Figure 1 and it the Well Search Table). The available well seal information collected in the search E appears to seal out the shallow aquifer. i The groundwater monitoring data has shown the dissolved. plume appears stable with concentrations declining to none detected in 2010 at MWWES-1. Based on the available data it is our opinion that shallow Aquifer water was affected but contaminants have declined to none detected and beneficial groundwater use of the deeper aquifer is not affected on the basis of this information. No soil vapor samples were collected. However the site soil and groundwater indicate ; vi.ry minimal contaminant residues present and on this basis the soil vapor risk is judged I as low. r 2.19_Ust of technkal reports. y A list of the technical reports is attached(see 2.22 References). 48991CSR1Rcpt Pulte 10 of 17