Laserfiche WebLink
1 <br /> 1 Site Background Information Sierra Lumber Manufacturers (Case#2) <br /> . <br /> Page 2of3 <br /> the estimated depth to ground water at the site is approximately 20 feet below surface grade (bsg) <br />' Review ofLtnes ofEqual Elevation of Ground Water Spring 1999(FCD&WCD)shows the regional <br /> ground water flow direction toward the northeast However,based on data collected during recent <br /> ground water monitoring events conducted at the site,ground water flow appears to fluctuate toward <br />' the northeast and southwest,flow direction vary due to local recharge and discharge patterns Review <br /> of historical depth to ground water maps (FCD&WCD) dating back to 1971 suggests that ground <br /> water depth near the site has fluctuated between 15 feet and 50 feet bsg, though in recent ground <br />' water monitoring events, ground water is encountered at approximately 20 feet bsg <br /> i <br />' PREVIOUS INVESTIGATIONS <br /> In June 2004, a series of soil borings were advanced at the site by Alta EM, Inc (AEI) as part of a <br />' property transfer Three soil borings (Alta-B3, Alta-B7, and Alta-B8) were advanced near the <br /> southeast corner of the Plant#2 building, in the area of a former underground storage tank (UST, <br />' Tank Area B) Petroleum hydrocarbons were detected in soil and ground water samples collected <br /> from the boring advanced within the presumed former tank pit excavation Total petroleum <br /> hydrocarbons quantified as gasoline (TPH-g) and volatile aromatic compounds benzene, toluene, <br /> I . ethylbenzene, and total xylenes (BTEX) were detected in soil samples at concentrations as high as <br /> 4,920 milligrams per kilogram (mg/kg) TPH-g and BTEX were detected in a grab ground water <br /> sample collected from boring Alta-B3 at concentrations as high as 400,000 micrograms per liter <br /> (µg/1)and 25,300µg/1,respectively The approximate locations of the borings advanced and sampled <br /> by AEI are illustrated on Figure 2 Analytical results of borings Alta-B3,Alta-B7,and Alta-B8 are <br /> summarized in Tables 1 and 2 of this appendix <br /> IOn 29 March 2005, three ground water monitoring wells (MW-9 through MW-11) were installed <br /> at the site Pilot borings MW-9 through MW-11 were completed as ground water monitoring wells <br /> of the same designations using 2-inch diameter, Schedule 40 polyvmylchlonde (PVC) casing with <br /> a 0 020-mch slotted screen installed from 20 feet to 40 feet bsg TPH-g was detected in soil samples <br /> MW9-25, MW9-30, MW9-35, and MW9-40 at concentrations ranging from 14 mg/kg to <br /> 2,400 mg/kg BTEX compounds were detected in samples MW9-25, MW9-30, MW9-35, and <br /> MW9-40 at maximum concentrations in sample MW9-35 of 17 mg/kg toluene, 59 mg/kg <br /> ethylbenzene, and 352 mg/kg total xylenes Analytical results of monitoring well installation soil <br /> samples are included in Table 3 of this appendix <br /> ISTRATIGRAPHY <br /> I In general, silty clay, clayey silt, and sandy silt were encountered from surface grade to between <br /> 20 feet and 25 feet bsg From approximately 25 feet bsg to the total depth of borings MW-9 through <br /> • MW-11 (40 feet bsg) sand, silty sand, sandy silt, and silt were encountered Saturated soil was not <br /> Advanced GeaEnvironmentah Inc <br />