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Ms.Kerry Heckman - 2 - 29 April 2005 River City Petroleum/Fortner Connell Motor Lift Truck Soil cores were collected every 10 feet bgs from MW-36 and MW-37. Petroleum hydrocarbons were only detected at 60 and 70 feet bgs in the saturated zone. Results are shown in milligrams per kilogram: TPHg B T E X TBA 1,2-DCA* MW-37-60 470 1.6 6.1 3.4 23 <0.025 0.19 MW-37-70 5.4 1.1 0.12 0.09 0.41 0.036 0.063 "detected at very low levels in all soil samples to 150 feet bgs,which may be the result of dissolved phase contamination in groundwater,or releases occurring during historical low groundwater levels(>90 feet bgs),per discussions with San Joaquin County Environmental Health Department(SJCEHD). AGE concludes in the Workplan that groundwater contamination has not been fully characterized by the existing groundwater monitoring well network and previous Cone Penetrometer Testing(CPT)groundwater investigations. Enclosed Figure 2 shows the locations of five proposed Continuous Multi-chamber Tubing (CMT)monitoring wells screened vertically at target depths(preferential pathways) from 60 to 200 feet bgs,to complete vertical and lateral characterization of the groundwater plume. Each CMT well is capable of independently monitoring up to seven discrete hydrologic zones. Five hydrologic zones previous identified will be targeted(first water): 50 to 60 feet bgs, 75 to 85 feet bgs, 95 to 100 feet bgs, 145 to 150 feet bgs, and 195 to 200 feet bgs. Comments: a. In a phone conversation with AGE on 10 March 2005 during the 1"quarter of 2005 groundwater monitoring event, I was informed that MW-1 was purged and sampled. Please be prepared to redevelop MW-1 if silting continues to be a problem. b. Workplan Appendix G,page 3 gives potential target screened zones (zones)for the CMT wells as 50-65 feet bgs, 75-80 feet bgs, 95-100 feet bgs, 145-150 feet bgs, and 195-200 feet bgs. Note that these zones are not applicable to all five of the proposed wells,but may be considered during construction if nearby wells do not provide monitoring of those zones. For example,the well proposed west of the building(near MW-17) should be screened at depths greater than 135 feet bgs,the deepest nearby well. The zones for new monitoring wells should target more permeable strata identified as potential preferential pathways during geologic logging of the borings. c. Workplan Figure 2 shows the northern CMT well approximately 50 feet north of Cone Penetrometer Test (CPT)boring CPT9. Text on page three of Appendix G says the CMT well will be installed 8 feet north of CPT9. Based on the previous CPT9 results shown on enclosed Figure 5 (maximum 1,2-DCA, 18 µg/L at 110 feet bgs, <0.5 gg/L at 150 and 180 feet bgs),a new CMT well located 50 feet north of CPT9 is not justified at this time. Please submit a letter addendum to the Workplan with a figure showing the correct location of all CMT wells,including the well described in the text as 8 feet from CPT9. The corrections are due by 6 May 2005. d. A draft Monitoring and Reporting Program(MRP)for River City Petroleum and Connell Motor Lift Truck is enclosed for your review. Due to the need for consistency in monitoring,the complex hydrogeology and the number of monitoring wells,an MRP is appropriate for your site. Please provide comments by 1 July 2005. e. Provided my comments in b. and c. are addressed,the five CMT monitoring wells described in the Workplan appear to be appropriate to complete vertical and lateral delineation of the petroleum hydrocarbon groundwater plume. I will delay final approval the CMT wells until your consultant AGE resolves outstanding issues with CMT wells with SJCEHD for the well permits. If you have cost effective alternatives to CMT wells that will meet SJCEHD permit requirements and State Water