FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Na Further Action Request 640 N.San Joaquin Street.Stockton,CA G October 9,2002 f ' Page 3 On June 27, 2002, soil surrounding TK-i was further excavated. No staining, odors, or other signs of contamination were noted in the excavated soil above TK-1. The tank measured five feet in diameter and ten feet in length; the approximate volume of TK-I is 1,500 gallons. The suction and return pipes were disconnected from TK-1 and the portions continuing beneath the basement of the Heritage Square building to the south were capped and left in place. The fill pipe was excavated approximately nine feet north of the UST into the sidewalk along the south side of E. Park Street where a former remote fill connection was identified (Figure 6, Appendix A). The horizontal portion of the fill pipe was removed for disposal. The vertical portions of the fill pipe and the vent pipe were capped and left attached to the UST to allow for UST closure to take place without re-excavation. The UST was pressure-washed and triple- rinsed and the rinsate removed and transported off site for disposal by American Valley Waste Oil, Inc. The excavation was backfilled with the clean excavated material and the fill and vent pipe locations marked for later identification. On Jul 26 2002 a Condor geologist was on-site to supervise the advancement of angle borings using Y � b g p g g g hollow stem auger (Figure 3, Appendix A). The borings were advanced in the asphalt-covered area east (TB-I) and west (TB-2) of TK-1 and angled in order to evaluate the soil directly underneath the UST for possible hydrocarbon contamination. Two soil samples were collected from each boring for laboratory analyses from depths of approximately ten feet bgs and 15 feet bgs (the latter two feet below the bottom of the UST). These depths corresponded to boring distances of approximately 15 feet and 21.5 feet, respectively. The borings were terminated prior to encountering groundwater. The'approximate sample locations are shown in Figures 3, 4 and 5,Appendix A. A log for boring TB-1 is provided in Appendix C. f After completion of the drilling and sampling program, the boreholes were backfilled with grout. - The.four soil samples collected from borings TB-1 and TB-2 were analyzed for BTEX, MTBE, TEPH-K, TEPH-D, TEPH-MO;and total lead('fable F, Appendix B). Toluene, total xylenes, TEPH-D, TEPH-MO, and total lead were detected in the soil sample collected.from boring TB-1 at approximately tell feet bgs. These same constituentsand ethyl benzene were detected in the soil sample collected from"boring TB-I at approximately 15 feet bgs. No petroleum hydrocarbons or BTEX constituents were detected at or above the laboratory reported detection limits in either of the soil samples collected from boring TB-2. The soil sample with the highest detected contaminant concentrations (TB-1., S-2T2I.5') was also analyzed for polynuclear aromatic hydrocarbons (PNAs) and for CAM 17 Metals(Table G). Due to the depth and proximity of TK1 to the structure (Figure 6, Appendix A), any attempts to excavate and remove the tank from the site, as are conventionally done to permanently close a UST, were determined by Condor to pose a threat to the integrity of the structure. The UST was permanently closed in place following established guidelines and according to the Underground Storage Tank Closure in Place Work Plan submitted to and approved by SJCEHD and the City of Stockton Fire Prevention Division (F.PD). Condor prepared a letter report dated August 28, 2002 describing the tank closure activities. 3.0 RISK EVALUATION Laboratory analytical results of the soil and groundwater.samples collected on June 10, 2002 and July 26, 2002 indicated that benzene, MTBE, and kerosene range petroleum hydrocarbons were not detected at or above the laboratory reported detection limits in any of the samples. Toluene and total xylenes were detected in three soil samples, ethyl benzene was detected in two soil samples, diesel range petroleum hydrocarbons were detected in three soil samples, and motor oil range petroleum hydrocarbons were detected in four soil samples and one _groundwater sample. No PNAs were detected at or above the laboratory reported detection limits in the one soil sample analyzed for those compounds. �, CONDOR