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Mr. Donald Rodgers - 3 - 1 April 2008 <br /> 515 West Charter Way, Ston, San Joaquin County 0 <br /> i` <br /> standard. The boring diameter must be increased to comply with the SJCEHD permit <br /> requirements. Your comments should address this requirement. <br /> 2) The Workplan specifies using Helium (He) as a tracer gas during baseline, injection and <br /> post-injection testing of well headspace measurements in all wells listed above. The <br /> rational for collecting He data is "...to further determine the ROI for oxygen distribution, as <br /> well as assess the migration, if any, of the volatilized organics from groundwater into the <br /> vadose zone and if a pneumatic control of offgas from the biosparging operation will be <br /> necessary." Considering that monitoring DO and water levels will be the primary method for <br /> determining ROI, and a PID will be used to measure off-gassing in the existing vapor wells, <br /> provide additional clarification (expand on) why He testing is needed, and also state what <br /> additional cost and benefit will be provided by He testing over the primary methods of <br /> testing. If we determine that there is a cost benefit to He testing, then we will consider <br /> adding He back to the testing. <br /> 3) The Workplan proposes PID monitoring for petroleum hydrocarbons off-gassing from vapor <br /> extraction wells VW-1 S, VW-2S, and VW-3S during the biosparging pilot study. Based on <br /> the locations of these wells, there is no off-gassing monitoring point for the vadose zone to <br /> the north of the sparge well, in the direction of the drapery shop located 10 feet away. <br /> While MW-4RS is located in that direction, its well screen is submerged approximately <br /> 15 feet below the water table and is not screened in the vadose zone. Provide a method to <br /> monitor for off-gassing to the north in your response to comments. <br /> 4) A schedule is necessary for the pilot study field activities and the submittal of this report in <br /> the Final Remediation Plan. Please provide a detailed schedule for the pilot study field <br /> activities in your response to the above listed comments by no later than <br /> 15 April 2008. <br /> 5) In a phone conversation with Charlie So, Senior Engineer for Shaw on 27 March 2007, <br /> Mr. So stated that if the letter approval were granted in the next week, the fieldwork could <br /> be concluded by mid-June of 2008. When asked, Mr. So could not commit to a submittal <br /> date for the FRP, citing concerns that biosparging may prove ineffective and that another <br /> remedy and pilot study may be required. Not wanting to delay the process, I suggested we <br /> discuss the data within one month of completion of the fieldwork, to determine a reasonable <br /> schedule for the FRP. To that end, I have scheduled a meeting in my office on <br /> 14 July 2008 at 10 AM to discuss the biosparging pilot study results and to set the FRP <br /> schedule. Please confirm your attendance in the response to comments. <br /> Once final approval is given, please procure all necessary permits and clearances, and provide the <br /> SJCEHD and myself at least three working days notice prior to commencement of <br /> field activities. If you have any questions you may call me at (916) 464-4615, or email me at <br /> jbarton@waterboards.ca.gov. <br /> l <br /> L i <br /> i <br /> James L. L. Barton, P.G. <br /> Engineering Geologist <br />