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<br /> ,.� `..'
<br /> Mike Infurna [EH]
<br /> From: Barclay, Diane [Diane.Barclay@stantec.com]
<br /> Sent: Tuesday, December 28, 2010 2:51 PM
<br /> To: Mike Infurna [EH]
<br /> Cc: Lathrop, Shelby S (Shaw Environmental, Inc.); Shelton, Brad
<br /> Subject: 76 (Former BP)Service Station No. 11192, 1403 West Country Club Blvd, Stockton
<br /> Attachments: FIG1-11192-SITEPLAN WITH PROPOSED CPT LOCATIONS-12-22-2010 11X17L .pdf
<br /> Hello Mike,
<br /> We have reviewed the site history, numerous work plans for this site, and your concerns, and we propose the
<br /> following path forward to address the delineation data gaps in the multiple water-bearing zones. We will conduct
<br /> an initial -T investigation consisting of three"to four b6rings offsite along Elmwood Avenue, and twoborings
<br /> onsite. The results of this investigation will allow us to immediately thereafter propose installation of additional
<br /> monitoring wells, as appropriate. The abditicbf-Ml Ivi6bif rinVwells will be installed using soli aWfilft'ifiethods to
<br /> provide continuous cores while protecting against cross-contamination of water-bearing zones. The investigation
<br /> areas are detailed below, and the proposed locations are shown 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 afe �bearipg intervals at the following approximate
<br /> depths: A- 15 to 20 feet; B - 35 feet; and C-60 feet, anMa tone's indentified in the 2002 CPT investigation
<br /> (97 to 100 feet and 121 to 124 feet). If other potential water-bearing zones below the depth of the C zone are
<br /> identified in the field, samples will also be collected from these zones. Groundwater samples will be collected at
<br /> these depths in the CPT borings with the exception of the A zone at CPT-6; due to the proximity of A—zone
<br /> kA monitoring well MW-9,,to._Ql'T_-6, additiorial'A zd 'e'dataisIi6t 6et6 ted MhiVt6d5tJ . CPT-4 will be the first
<br /> location investigated during the mobilization, and groundwater samples from this location will be analyzed by the
<br /> lab on a 2-day turnaround time. The data from CPT-4 will be discussed with you, COP, and BP, and a decision
<br /> regarding the need for the additional 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 depths
<br /> greater than the existing well network can provide, allow comparison to the data from previous CPT investigation
<br /> conducted in 2002, and provide upgradient delineation. CPT-7 will be located adjacent to the existing C zone
<br /> well (MW-11 —screened from 68.5 to 78.5 ft bgs), and will be pushed to a maximum depth of 140 feet(or
<br /> refusal). Groundwater samples will be collected at water bearing depths identified at CPT-3 in 2002
<br /> (approximately 97 to 100 ft bgs and 121 to 124 ft bgs); samples from additional depths may be collected based on
<br /> the soil stratigraphy and pore pressure data obtained in the field. CPT-8 will be located in the west-central portion
<br /> of the site to provide upgradient delineation information, and will also be pushed to approximately 140 ft bgs (or
<br /> refusal). Groundwater samples will be collected from CPT-8 at the approximate known hydrologic intervals for A,
<br /> B, and C described above, and the deeper intervals as described for CPT-7.
<br /> Groundwater samples will be analyzed for TPH-g, BTEX, fuel oxygenates (MtBE, DIPE, TAME, EtBE, TBA, and
<br /> ethanol), and lead scavengers (1,2-DCA and EDB) by a California-certified laboratory.
<br /> Upon co Ietion of the initial field work,we will provide you with the preliminary data lt�Ff[ei3 :.fdr x
<br /> S CIilt► i I rritsnific ung wells;4Upon your concurrence,we will install the additiona monitoring wells using
<br /> sonic drilling. Soil samples will be collected from the well borings at five-foot intervals above the water table for
<br /> the purpose of logging soil stratigraphy, moisture content, odor, PID readings, and other physical characteristics.
<br /> Based on positive PID readings and field observations, at least two samples from the vadose zone from each well
<br /> boring will be selected for laboratory analysis for the same compounds as listed for groundwater, above. In the
<br /> event that no positive PID readings are encountered, one soil sample will be selected from just above the water
<br /> table and one sample will be 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 would
<br /> be happy to revise and/or develop a comprehensive work plan and submit it to you.
<br /> 12/28/2010
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