SITE INFORMATION AND CORRESPONDENCE

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a � Donna Heran 325 S. EI Dorado Street December 16, 1999 Page 2 . The site is located five blocks south of the eastern end of the Stockton Deep Water Channel, and four blocks north of Mormon Slough. The soils to groundwater in this, and surrounding areas, are predominantly clays. According to the San Joaquin County Flood Control District Maps, groundwater is located approximately thirty feet below ground surface. Previously on this site, an area contaminated with heavy metals and oil was identified as the site of an old auto-dismantling center. The dismantling center existed over thirty years ago. The soil was tested to find the limits of contamination, excavated and hauled to an;appropriate dumpsite. Evidence of transport of the j contaminant was not present, as the area required only four feet (4') of vertical - -. excavation;._even,after thirty y_ears_.J.his_is mentioned as a basis of,comparison as to _ the lack of movement of contaminants through the soils at this site. C c"4 .cs otVO z A recent study was sponsored by the State Water Resources Board (SWRB) on the cleanup practices for leaking underground storage tanks (LUFTs). The study found that low risk leaksrare stabilized.by microorganisms consuming the fuel, referred to as passive remediation, thereby stabilizing the plume. The study also showed that benzene, the most dangerous component, does not travel far from the.source;-'even_ overtime... The study supports the option of passive cleanup for low risk sites-.with shallow groundwater as opposed to the traditional aggressive methods. The-contaminated soil under one end of the twelve-foot (12') tank dobs'not:'qualify as a A . #ypical#resh or high-risk spice. The test results are more indicative of'an o1d leak,: '' a Y possible after the tank was predominantly_emptied, as no BTEX or Bt;were`detected at any of the sampling locations. Tests of the first tank removed were clean, also indicative of an isolated leak that is not spreading. Resistance to transport at this site is supported by the presence of predominantly clay soils, and lack of transport of oil and metal contamination at adjacent location. Additionally, this tank was located immediately adjacent to El Dorado Street. Any r - attempts to excavatemateriai-from-tlie site-would jeopardize tlle`iritegFity,of the street"" Even with shoring and supports, EI Dorado Street could suffer significant'damage. It is also important to note that this site is commercially zoned and that the Agency has. approved a project (plans available on request) that will provide for complete coverage of the property. The project will consist of single story retail facilities and!parking. Either building improvement's or asphalt paving will cover the entire site and there-will be no opportunity for migration of contamination due to percolation of surface water. Considering the specifics of this site, the low levels of contamination, thellrend by 3the SWRB towards passive methods for low risk sites, the potential risks to EI Dorado Street, and the proposed improvement project on this site; we would request this site be allowed to remain in place and undergo passive remediation.