SITE INFORMATION AND CORRESPONDENCE

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Request!or arts Gioaaa 3 Chww USA PnWuds C nrpww.5481 west Grant Line Read.Sw CA Septaetw 22.1M EXISTING SITE CONDITIONS The site is currently an asphalt paved lot with the warehouse and office building as shown on Figure 2. As of May 26, 1995, water levels were approximately 10-11 feet BGS at the site. No dissolved petroleum hydrocarbons have been detected in groundwater(with the exception of TW-2)since sampling was initiated in March 1993(Table 2). Figure 1 shows the site location,topography,and surrounding features. Since groundwater Is not Impacted no survey of Department of Water Resources well records was completed. Figure 2 Is a site map showing the general site layout,current location of groundwater monitoring wells and the former location of soil borings and temporary groundwater monitoring wells. RATIONALE FOR SITE CLOSURE Current site conditions Indicate that environmental concerns at the site are of no immediate or future threat to current and potential beneficial uses of groundwater beneath the site. As stated in the Addendum to Appendix A of the Tri-Regional Guidelines(CRWQCB-NCR,SIB,CVR, 1990),a rationale for site closure should be included with the request for closure. Based on a review of the results of past Investigations and risk assessment,two compelling reasons exist as a bask for no further environmental action,including: Nan-extensive hydrocarbon impact and small mass of hydrocarbons remaining In the subsurface ■ Lack of significant leachate potential Non-Extensive Hydrocarbon-Impacted Sol/ Based on the data provided by the three site investigations conducted at the site in 1993 and 1994 and subsequent quarterly groundwater monitoring and sampling events,conclusions can be drawn as to the extent of hydrocarbon-Impacted material currently in place at the site. Non-detectable concentrations have been observed In borings drilled to the west(TW-2,MW-3),the east(MW-1),and to the north (TW-1). The three boreholes with soil samples that show hydrocarbon impact include B-3,SB-4 and MW-2. B-3 being nearest the suspected source(former USTs)contained the highest hydrocarbon concentrations(96 and 24 ppm TPH-G). SB-4 contained benzene concentrations of.007 ppm at 10 feet Oust.002 ppm over the detection limit)and no TPH-G. MW-2 contained 1 ppm TPH-G (equal to the detection limit)and no benzene. The three points are aligned approximately parallel to the prevalent groundwater flow direction. SB-4 and MW-2,downgradlent of the source,show concentrations of hydrocarbons in the 10 feet BGS sample at the soil/groundwater interface. Because the borings fall in a line and are bracketed by borings not impacted with hydrocarbons,the lateral and 01"CW." �taROUNDWAM TlMNOLOGY•