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<br /> January 24,2025
<br /> Brusca File No. 260-004 Additional Groundwater Monitoring Well Workplan
<br /> SITE DESCRIPTION AND BACKGROUND
<br /> A 1,000-gallon diesel UST was previously located on the westerly portion of an approximate 140-
<br /> acre parcel(APN 091-030-130) situated directly southerly of East Comstock Road and about 2,400
<br /> feet easterly of Jack Tone Road in Linden, San Joaquin County, California. The majority of the
<br /> parcel and surrounding areas support farmland comprised of orchards. The UST was situated
<br /> within the Anderson Barrigrover farm facility, directly easterly of an older, sizable walnut huller
<br /> building and westerly of an office building (converted residence) associated with the farm (see
<br /> Plate 2). It is indicated that the UST was an exempt farm tank and neither San Joaquin County
<br /> permitting nor regulatory oversight was required or provided for the UST removal.
<br /> Laboratory testing of soil samples collected at the time of UST removal revealed that an
<br /> unauthorized release(s) had occurred from the UST system; it is reported that diesel-range
<br /> petroleum hydrocarbons and related volatile organic compounds (VOCs), including benzene,
<br /> ethylbenzene, xylenes, and naphthalene, were detected in soil samples collected beneath the
<br /> UST. Since that time, our firm has conducted investigations to evaluate the nature and extent of
<br /> subsurface impact conditions attributable to the former diesel UST, including a number of
<br /> exploratory borings for soil and groundwater sampling, soil gas sampling, performance of a water
<br /> well survey,sampling of the onsite water supply wells,and comparison of site information to Low-
<br /> Threat Closure Policy(LTCP)Criteria.2 s 4 s 6
<br /> In a letter dated December 12, 2023, the CVRWQCB relayed that additional site assessment is
<br /> necessary, for site closure consideration, including further evaluation of the extent of the diesel
<br /> groundwater plume to the west and installation of groundwater monitoring wells to evaluate the
<br /> groundwater flow direction, plume stability, and whether non-aqueous phase liquid (NAPL) is
<br /> present. Our firm directed the installation of three groundwater monitoring wells at the site and
<br /> conducted quarterly monitoring of the wells through the fourth quarter of 2024.'
<br /> The results of the fourth quarter 2024 groundwater monitoring at the subject property are
<br /> somewhat anomalous compared to previous monitoring results; the concentrations of diesel-
<br /> range petroleum hydrocarbons detected in the fourth quarter groundwater samples are
<br /> z Brusca Associates, Inc.; "Soil Investigation, Area of Removed Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property,APN 091-030-130, 14290 East Comstock Road, Linden,San Joaquin County, California";April 7,
<br /> 2023.
<br /> 3 Brusca Associates, Inc.; "Additional Site Investigation, Area of Removed Underground Fuel Tank, Anderson
<br /> Bamgrover Ranch Property, APN 091-030-130, 14290 East Comstock Road, Linden, San Joaquin County,
<br /> California";June 8,2023.
<br /> 4 Brusca Associates, Inc.; "Additional Plume, Area of Removed Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property, APN 091-030-130, 14290 East Comstock Road, Linden, San Joaquin County, California";
<br /> September 11,2023.
<br /> s Brusca Associates, Inc.; "Additional Plume, South of Former Underground Fuel Tank, Anderson Barngrover
<br /> Ranch Property,APN 091-030-130, 14290 East Comstock Road,Linden, San Joaquin County, California"; October
<br /> 31,2023.
<br /> e State Water Resources Control Board; "Low-Threat Underground Storage Tank Case Closure Policy"; effective
<br /> August 17,2012.
<br /> Brusca Associates, Inc.; "Installation and Initial Sampling of Groundwater Monitoring Wells, Anderson
<br /> Bamgrover Ranch Property, APN 091-030-130, 14290 East Comstock Road, Linden, San Joaquin County,
<br /> California";April 5,2024.
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