|
Raymond Investment Corporation Page 2
<br /> 730 Channel Street March 3, 2010
<br /> Stockton, California 95202
<br /> • Monitoring well MW-6 will be installed with a screen interval between approximately
<br /> twenty-five and forty-five feet bsg. Soil samples will be collected at 25, 35, and 40
<br /> feet bsg for laboratory analysis;
<br /> • Monitoring well MW-7 will not be installed at its originally proposed location near the
<br /> north side of the former underground storage tank (UST) area. In place of this
<br /> monitoring well, three soil borings (SB12, SB13, and SB14) will be advanced along
<br /> the southern perimeter of this site, south of the former UST area, to investigate the
<br /> vertical and lateral extent of petroleum hydrocarbon contamination. Soil samples will
<br /> be collected for chemical analysis during the advancement of the three borings at 8,
<br /> 10, 15, 25, and 35 feet bsg, along with a grab groundwater sample collected at
<br /> approximately 30 to 34 feet bsg, or"at the uppermost groundwater";
<br /> • Monitoring wells MW-7, MW-8, and MW-9 will be installed in the sidewalk or parking
<br /> lane on the west side of Grant Street and south side of East Channel Street, only if
<br /> analytical results from groundwater collected from MW-5, or field observations during
<br /> the installation of MW-5, indicate the presence of chemicals of concern in
<br /> groundwater. MW-7, MW-8, and MW-9, if installed, will each be screened between
<br /> approximately twenty-five and forty-five feet bsg, and no soil samples will be
<br /> collected;
<br /> • Soil and groundwater samples collected during the advancement of soil borings
<br /> SB12, SB13, and SB14, and installation of monitoring wells MW-41D, MW-5, MW-6,
<br /> and possibly MW-7 through MW-9, as well as groundwater samples collected
<br /> quarterly from the newly-installed monitoring wells, will be analyzed for total
<br /> petroleum hydrocarbons (TPH) quantified as gasoline (TPH-G), total extractable
<br /> petroleum hydrocarbons (TEPH) quantified as diesel (TEPH-D), TEPH-motor oil
<br /> (TEPH-MO), and benzene, toluene, ethylbenzene, and total xylenes (BTEX); and
<br /> • Soil gas samples collected from soil vapor wells SV-4, SV-5, and SV-6 will be
<br /> analyzed for BTEX, 1,1-difluoroethane, TPH-vapor (TPH-V), naphthalene, tertiary-
<br /> butyl alcohol (TBA), methyl tertiary-butyl ether (MTBE), ethyl tertiary-butyl ether
<br /> (ETRE), di-isopropyl ether (DIPE), and tertiary-amyl methyl ether (TAME) by
<br /> Environmental Protection Agency method TO-15, and TPH-D by EPA method TO-17.
<br /> In the revised work plan, Condor proposes to collect two ambient air samples, one near an
<br /> undesignated well (ambient blank), and one inside the building (indoor air) "for comparison to
<br /> soil vapor results and estimation of attenuation factors or for quality control." Various materials
<br /> and unknown factors within the building may contribute to the findings from the analysis of the
<br /> ambient air sample inside the building. For this reason, the EHD does not believe the results
<br /> from the collection of ambient air can be appropriately evaluated; therefore, the EHD does not
<br /> approve the collection of the two ambient air samples. If Condor can provide authoritative
<br /> guidance for collecting ambient air samples and evaluating their analytical results, the EHD may
<br /> reconsider its decision. i
<br /> l
<br />
|