ARCHIVED REPORTS XR0009933 - Laserfiche WebLink

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Sampling Plan - 152 East 11th, Street, Tracy, CA Page 4 installation of new tanks at the Beacon Station in October 1986 Components of fuel 1-1-AC" L" w hydrocarbons were detected in the pit excavated to accomplish the tank replacement zl. - c" X- project and the pit was over-excavated to remove approximately 1,155 tons of affected soul , Q = which was disposed off-site at a permitted facility Some 52,000 gallons of affected Yom' � U) ff groundwater was pumped from the excavation and similarly disposed by shipment off-site ' >- U.J for treatment at a permitted facility The over-excavated pit, which was backfilled withv clean material, had plan dimensions of 42ft by 40ft and was 15ft deep Its location is a indicated on Figure 2 La To further assess the extent to which the subsurface beneath and around the 152 and 153 East i nth Street sites is affected by hydrocarbons, the SJCPHS requested that a workplan be prepared for installation and sampling of additional monitoring well The requested plan titled Workplan for Further Sod And Groundwater Assessment at 152 East 11th Street, Tracy, Cahforrua, was submitted to the SJCPHS on February 26th 1993 and subsequently approved by that agency The new wells will be designated NAV 5, through NAV 8 Their proposed locations are shown on Figure 2 Permission to install the proposed monitoring wells in the public street is being sought from the City of Tracy who have requested that the well installation work be coordinated with the re-paving and refurbishment of 11th Street winch is currently ongoing San Joaquin County permits for these wells will also be obtained Groundwater Quality Data The results of periodic rounds of sampling of the wells installed as part of the investigations for both the Navarra property at 152 East 11th Street and for the Beacon Station at 153 East 11th Street are summarized in Table 1 The data in the table were synthesized from reports provided by Ultramar, review of available documents on file at the SJCPHS and our protect file Other Known and Potential Sites of Hydrocarbon Releases As part of the planning for installation of the new wells NAV 4 through NAV 8, a search was made for available records pertaining to known releases of hydrocarbons into the subsurface, or sites at which releases may have occurred, in the area around the 152 and 153 East 11th Street properties According to records on file at the SJCPHS, a 300 gallon underground gasoline storage tank and an oil and water separator were previously located at 208 East 11th Street on the site occupied by Tracy Auto Parts (See Figure 2 for location of that property) When the gasoline tank was removed in July of 1991 the soil beneath the tank was contaminated by petroleum products that included total petroleum hydrocarbons at a concentration of 1700 mgXg, Toluene at 570 pg/Kg, Ethylbenzene at 3200 µg/Kg and Xylenes at 9000 ILg/Kg, Given the hydrogeological conditions in the area, it as likely that contaminants from this . source have migrated north or northwest down the groundwater gradient so as to affect groundwater quality along, and possibly beyond, the south side of East 11th Street in the