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Brusca File No. 137-002
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<br />Page 2
<br />January 8, 2021
<br />Murphy Parkway Property Soil Gas Monitoring
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<br />BACKGROUND
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<br />The approximate 48-acre subject parcel is located about 500 feet easterly of Murphy Parkway and
<br />about 1,500 feet southerly of East Louise Avenue in a commercial and industrial area of Lathrop,
<br />San Joaquin County, California (See Plate 1, Vicinity Map). A large light-industrial/warehouse
<br />building and associated pavements were constructed on the property in 2018. The general layout
<br />of the onsite development is shown on Plate 2, Site Map.
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<br />The lead agency overseeing environmental conditions at the site is the San Joaquin County
<br />Environmental Health Department (SJCEHD). CalRecycle and the Central Valley Regional
<br />Water Quality Control Board (CVRWQCB) also have been involved with review of site
<br />conditions. These agencies have indicated that implementation of a soil gas monitoring program
<br />is required due to the presence of uncharacterized wastes that reportedly exist offsite to the west
<br />of the subject property (property formerly occupied by a cogeneration facility). As requested by
<br />the SJCEHD, our firm prepared a Soil Gas Monitoring Workplan dated August 10, 2017.1 Upon
<br />review, the SJCEHD requested minor modifications to the Workplan, and we prepared an
<br />Addendum to the Workplan dated November 7, 2017.2 The required soil gas monitoring program
<br />consists of monthly monitoring for a period of one year, and quarterly monitoring for a period of
<br />four years thereafter. The SJCEHD indicated approval of the monitoring program via email on
<br />November 8, 2017. The soil gas monitoring wells (identified as SGMW1 and SGMW2) were
<br />installed on January 16, 2018; the locations of the wells are shown on Plates 2 and 3.3 Monthly
<br />soil gas monitoring was performed through the end of 2018, and quarterly groundwater
<br />monitoring was initiated in 2019. One of the soil gas monitoring wells (SGMW1) was
<br />accidentally damaged by construction equipment in July 2018; this well was replaced in August
<br />2018.4
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<br />SOIL GAS MONITORING/SAMPLING
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<br />The Fourth Quarter 2020 soil gas monitoring/sampling was performed at the site on December
<br />18, 2020. At that time, the soil gas monitoring wells were inspected to confirm they were sound
<br />and without damage. Prior to sample collection, each well was screened with a portable gas
<br />indicator (RKI Eagl e) connected to the sampling ports on the wells. Screening measurements
<br />(including methane percentage, carbon dioxide concentration, oxygen percentage, and hydrogen
<br />sulfide concentration) were recorded and are presented on the attached Table I. As shown on
<br />Table I, methane was not detected in either of the soil gas monit oring wells via field screening.
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<br />Following screening, laboratory-provided sampling containers (one-liter Summa canisters) w ere
<br />attached to the sampling ports on the wells and soil gas samples were collected from each well.
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<br />1 Brusca Associates, Inc.; “Soil Gas Monitoring Workplan, Murphy Parkway Property, APN 198-120-009, 17100
<br />Murphy Parkway, Lathrop, California”; August 10, 2017.
<br />2 Brusca Associates, Inc.; “Addendum to Soil Gas M onitoring Workplan, Murphy Parkway Property, APN 198-120-
<br />009, 17100 Murphy Parkway, Lathrop, California”; November 7, 20 17.
<br />3 Brusca Associates, Inc.; “Soil Gas Monitoring Wells Installation, Murphy Parkway Property, APN 198-120-009,
<br />17100 Murphy Parkway, Lathrop, California”; February 12, 2018.
<br />4 Brusca Associates, Inc.; “Replacement of Soil Gas Monitoring Well SGMW1, Murphy Parkway Property, APN
<br />198-120-009, 17100 Murphy Parkway, Lathrop, California”; August 31, 2018.
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