ARCHIVED REPORTS XR0003281 - Laserfiche WebLink

Home Browse Search

v ASSOCIATEATC S INC ' In September and October 2002, cone penetration testing (CPT) borings CPT1 and CPT2, Geoprobe (direct push) borings CPTla and CPT2a, and groundwater monitoring wells MW-4 through MW-8 were installed at the site CPT1 and CP I'2 borings were advanced to 120 and 139 ' feet bgs, respectively, to provide continuous stratigraphic definition in the borings Grab groundwater samples were collected from CPTIa and CPT2a at depths of 109 and 114 feet bgs, respectively Monitoring wells MW-4 through MW-8 were completed to a total depth of 65 feet ' bgs CrVI was not detected in soil samples collected from the boreholes of MW-4 through MW- 8 CrVI was detected in groundwater samples collected from wells MW-2 through MW-7 in September 2002, with the highest concentration detected at 4 0 mg/I in the groundwater sample collected from well MW-3 CrVI was detected at concentrations of 0 170 and 0 012 mg/1 in grab groundwater samples collected from borings CPTIa and CPT2a, respectively These grab samples were collected from the deeper water-bearing zone Total chromium was detected in the water samples collected from all the wells, including the facility well, with the highest concentration detected at 6 2 mg/t in the groundwater sample collected from MW-3 The grab groundwater samples collected from CPT1 a and CPT2a were not analyzed for total chromium These findings and results were presented in ATC's report titled Summary Report of Additional Subsurface Investigation, dated November 1, 2002 On April 29 and 30, 2003, ATC supervised the installation of monitoring well MW-9 MW-9 was installed in the northern portion of the site to a depth of 113 feet bgs to correspond with the deeper water-bearing zone encountered in boring CPT1 Laboiatoiy analytical results of a groundwater sample collected from MW-9 on May 5, 2003, indicated that CrVI and total chromium were detected at concentrations of 0 0049 and 0 0081 mg/l, respectively Refer to ATC's report Summary Report of Additional Subsurface Invevtrgation Deep Well Inve,stiganon, dated May 8, 2003, for additional information ' 2.0 SOIL AND GROUNDWATER SAMPLE COLLECTION Soil and groundwater samples were collected at the site and submitted to PRIMA Environmental ' (PRIMA) in Roseville, California to be utilized in the bench scale treatability study Historical information indicates the soil sample collected by WA from below Vault 8 at a depth of 14 8 feet bgs contained the highest concentration of CrVI (75 milligrams per kilogram [mg/kg]) ' Groundwater samples collected from MW-3 have historically contained the highest concentrations of CrVI with respect to the other monitoring wells ' 221 Soil Sample Collection Activities On October 13, 2004, a geologist from ATC supervised the advancement of two soil borings, ' SB 10 and SBI I The locations of the soil borings are shown on Figure 2 The borings were advanced by Woodward Drilling, California License C57 710079, utilizing a hollow stern auger drilling rig Soil boring SB I O was advanced beneath a chiller unit in the vicinity of Vault 8 to collect soil samples potentially impacted by CrVI The decision to collect soil samples from beneath the chiller unit was a result of a meeting at the site with CRWQCB, DWG, and ATC staff on February 3, 2004 Soil boring SB10 was advanced at a 35 degree angle Flom vertical un a southerly direction to obtain soil samples fiom three depth intervals beneath the chiller unit S lenvironmental1625831rf purtslh4nclt test rpt doc 3