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<br /> Mike Infurna [EH]
<br /> To: Barclay, Diane
<br /> Subject: 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 the
<br /> following path forward to address the delineation data gaps in the multiple water-bearing zones. We will
<br /> conduct an initial CPT investigation consisting of three to four borings offsite along Elmwood Avenue, and two
<br /> borings onsite. .The results of this investigation will allow us to immediately thereafter propose installation of
<br /> additional monitoring wells, as appropriate. The additional monitoring wells will be installed using sonic drilling
<br /> methods to provide continuous cores while protecting against cross-contamination of water-bearing zones. The
<br /> investigation 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 three water-bearing intervals at the following approximate
<br /> depths:A- 15 to 20 feet; B- 35 feet; and C-60 feet, and deeper zones indentified,in the 2002 CPT
<br /> investigation (97 to 100 feet and 121 to 124 feet). If other potential water-bearing zones below the depth of the
<br /> C zone are identified in the field, samples will also be collected from these zones. Groundwater samples will be
<br /> collected at these depths in the CPT borings with the exception of the A zone at CPT-6; due to the proximity of
<br /> A—zone monitoring well MW-9 to CPT-6, additional A-zone data is not warranted at this location. CPT-4 will be
<br /> the first location investigated during the mobilization, and groundwater samples from this location will be
<br /> analyzed by the lab on a 2-day turnaround time. The data from CPT-4 will be discussed with you, COP,and
<br /> BP, and a decision regarding the need for the additional boring CPT-9 will be made prior to the field
<br /> 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 of
<br /> 140 feet(or 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
<br /> on the soil stratigraphy and pore pressure data obtained in the field. CPT-8 will be located in the west-central
<br /> portion of the site to provide upgradient delineation information,and will also be pushed to approximately 140 ft
<br /> bgs(or refusal). Groundwater samples will be collected from CPT-8 at the approximate known hydrologic
<br /> intervals for A, 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 completion of the initial field work,we will provide you with the preliminary data and recommendations for
<br /> installing additional monitoring wells. Upon your concurrence,we will install the additional monitoring wells
<br /> using sonic drilling. Soil samples will be collected from the well borings at five-foot intervals above the water
<br /> table for the purpose of logging soil stratigraphy, moisture content, odor, PID readings, and other physical
<br /> characteristics. Based on positive PID readings and field observations, at least two samples from the vadose
<br /> zone from each well boring will be selected for laboratory analysis for the same compounds as listed for
<br /> groundwater, above. In the event that no positive PID readings are encountered, one soil sample will be
<br /> selected from just above the water 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
<br /> would be happy to revise and/or develop a comprehensive work plan and submit it to you.
<br /> Diane Barclay, PG, CEG, CHG . Principal Geologist ,Stantec
<br /> 2/17/2011
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