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Page 4 of 5 �—We have reviewed the site history, numerous work plans for this site, and your concerns, and we propose the following path forward to address the delineation data gaps in the multiple water-bearing zones. We will conduct an initial CPT investigation consisting of three to four borings offsite along Elmwood Avenue, and two borings onsite. The results of this investigation will allow us to immediately thereafter propose installation of additional monitoring wells, as appropriate. The additional monitoring wells will be installed using sonic drilling methods to provide continuous cores while protecting against cross-contamination of water-bearing zones. The investigation areas are detailed below, and the proposed locations are shown on the attached map. Three offsite CPT borings(CPT-4, CPT-5, and CPT-6)will be pushed along Elmwood Ave to provide soil stratigraphic and groundwater data for the shallowest three water-bearing intervals at the following approximate depths:A- 15 to 20 feet; B- 35 feet; and C-60 feet, and deeper zones indentified in the 2002 CPT investigation (97 to 100 feet and 121 to 124 feet). If other potential water-bearing zones below the depth of the C zone are identified in the field, samples will also be collected from these zones. Groundwater samples will be collected at these depths in the CPT borings with the exception of the A zone at CPT-6; due to the proximity of A—zone monitoring well MW-9 to CPT-6, additional A-zone data is not warranted at this location. CPT-4 will be the first location investigated during the mobilization, and groundwater samples from this location will be analyzed by the lab on a 2-day turnaround time. The data from CPT-4 will be discussed with you, COP, and BP, and a decision regarding the need for the additional boring CPT-9 will be made prior to the field investigation being completed. Two onsite borings(CPTand CPTI)will be pushed to collect soil stratigraphic and groundwater data at depth greater than the existing well network can provide, allow comparison to the data from previous CPT investigation conducted in 2002, and provide upgradient delineation. CPT-7 will be located adjacent to the existing C zone well (MW-11 — screened from 68.5 to 78.5 ft bgs), and will be pushed to a maximum depth of 140 feet(or refusal). Groundwater samples will be collected at water bearing depths identified at CPT-3 in 2002(approximately 97 to 100 ft bgs and 121 to 124 ft bgs); samples from additional depths may be collected based on the soil stratigraphy and pore pressure data obtained in the field. CPT-8 will be located in the west-central portion of the site to provide upgradient delineation information, and will also be pushed to approximately 140 ft bgs(or refusal). Groundwater samples will be collected from CPT-8 at the approximate known hydrologic intervals for A, B, and C described above, and the deeper intervals as described for CPT-7. Groundwater samples will be analyzed for TPH-g, BTEX, fuel oxygenates(MtBE, DIPE, TAME, EtBE, TBA, and ethanol), and lead scavengers (1,2-DCA and EDB) by a California- certified laboratory. Upon completion of the initial field work,we will provide you with the preliminary data and recommendations for installing additional monitoring wells. Upon your concurrence, we will 1 S install the additional monitoring wells using sonic drilling. Soil samples will be collected from the well borings at five-foot intervals above the water table for the purpose of logging soil �j stratigraphy, moisture content, odor, PID readings, and other physical characteristics. Based 17 on positive PID readings and field observations, at least two samples from the vadose zone from each well boring will be selected for laboratory analysis for the same compounds as listed for groundwater, above. In the event that no positive PID readings are encountered, one soil sample will be selected from just above the water table and one sample will be collected from an intermediate depth. 4-r The report will include data and conclusions based on both mobilizations. Please let me know if you approve of the plan above, and if your email approval will suffice, otherwise, we would be happy to re .sdor develop--a comprehensive work plan-and- submit lan-and - submit it to you. r"--i ''�--- -- -— ' Diane Barclay, PG, CEG, CHG Principal Geologist Stantec 1/24/2011