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<br /> Mike Infurna [EH)
<br /> To: Barclay, Diane
<br /> Subject: RE: 76 (Former BP)Service Station No. 11192, 1403 West Country Club Blvd, Stockton
<br /> From: Barclay, Diane —�—
<br /> Sent: Tuesday, December 28, 2010 2:51 PM
<br /> To: 'minfurna@sjcehd.com'
<br /> Subject: 76 (Former BP) Service Station No. 11192, 1403 West Country Club Blvd, Stockton
<br /> Hello Mike,
<br /> We have reviewed the site history, numerous work plans for this site, and your concerns, and we propose
<br /> the following path forward to address the delineation data gaps in the multiple water-bearing zones. We
<br /> will conduct an initial CPT investigation consisting of three to four borings offsite along Elmwood Avenue,
<br /> and two borings onsite. The results of this investigation will allow us to immediately thereafter propose
<br /> installation of additional monitoring wells, as appropriate. The additional monitoring wells will be installed
<br /> using sonic drilling methods to provide continuous cores while protecting against cross-contamination of
<br /> water-bearing zones. The investigation areas are detailed below, and the proposed locations are shown
<br /> on the attached map.
<br /> Three offsite CPT borings (CPT-4, CPT-5, and CPT-6)will be pushed along Elmwood Ave to provide soil
<br /> stratigraphic and groundwater data for the shallowest three water-bearing intervals at the following
<br /> approximate depths: A- 15 to 20 feet; B - 35 feet; and C -60 feet, and deeper zones indentified in the
<br /> 2002 CPT investigation (97 to 100 feet and 121 to 124 feet). If other potential water-bearing zones below
<br /> the depth of the C zone are identified in the field, samples will also be collected from these zones.
<br /> Groundwater samples will be collected at these depths in the CPT borings with the exception of the A zone
<br /> at CPT-6; due to the proximity of A—zone monitoring well MW-9 to CPT-6, additional A-zone data is not
<br /> warranted at this location. CPT-4 will be the first location investigated during the mobilization, and
<br /> groundwater samples from this location will be analyzed by the lab on a 2-day turnaround time. The data
<br /> from CPT-4 will be discussed with you, COP, and BP, and a decision regarding the need for the additional
<br /> boring CPT-9 will be made prior to the field investigation being completed.
<br /> Two onsite borings (CPT-7 and CPT-8)will be pushed to collect soil stratigraphic and groundwater data at
<br /> depths greater than the existing well network can provide, allow comparison to the data from previous CPT
<br /> investigation conducted in 2002, and provide upgradient delineation. CPT-7 will be located adjacent to the
<br /> existing C zone well (MW-11 —screened from 68.5 to 78.5 ft bgs), and will be pushed to a maximum depth
<br /> of 140 feet (or refusal). Groundwater samples will be collected at water bearing depths identified at CPT-3
<br /> in 2002 (approximately 97 to 100 ft bgs and 121 to 124 ft bgs); samples from additional depths may be
<br /> collected based on the soil stratigraphy and pore pressure data obtained in the field. CPT-8 will be located
<br /> in the west-central portion of the site to provide upgradient delineation information, and will also be pushed
<br /> to approximately 140 ft bgs (or refusal). Groundwater samples will be collected from CPT-8 at the
<br /> approximate known hydrologic intervals for A, B, and C described above, and the deeper intervals as
<br /> described for CPT-7.
<br /> Groundwater samples will be analyzed for TPH-g, BTEX, fuel oxygenates (MtBE, DIPE, TAME, EtBE, TBA,
<br /> and ethanol), and lead scavengers (1,2-DCA and EDB) by a California-certified laboratory.
<br /> Upon completion of the initial field work,we will provide you with the preliminary data and
<br /> recommendations for installing additional monitoring wells. Upon your concurrence, we will install the
<br /> additional monitoring wells using sonic drilling. Soil samples will be collected from the well borings at five-
<br /> foot intervals above the water table for the purpose of logging soil stratigraphy, moisture content, odor, PID
<br /> readings, and other physical characteristics. Based on positive PID readings and field observations, at
<br /> least two samples from the vadose zone from each well boring will be selected for laboratory analysis for
<br /> the same compounds as listed for groundwater, above. In the event that no positive PID readings are
<br /> encountered, one soil sample will be selected from just above the water table and one sample will be
<br /> collected from an intermediate depth.
<br /> The report will include data and conclusions based on both mobilizations.
<br /> Please let me know if you approve of the plan above, and if your email approval will suffice; otherwise,we
<br /> would be happy to revise and/or develop a comprehensive work plan and submit it to you.
<br /> 2/17/2011a - V, f . '! '-P_ /
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