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Joe Lentini . -2- • 22 March 2010 <br /> Former Pipelines, Tracy <br /> If no petroleum hydrocarbons are detected, no additional sampling will be conducted. If <br /> pollutants are detected, an additional confirmation sample will be collected within 14 days. If <br /> petroleum hydrocarbons are detected in the confirmation sample, then a sample plan will be <br /> developed. If petroleum hydrocarbons are above drinking water standards, then arrangements <br /> will be made to provide potable water or install a filtration system. If a filtration system is <br /> installed, a sampling plan will be developed for the well and an investigation will be conducted <br /> to determine the source of pollution. <br /> Our comments are presented below. <br /> 1. In the Response, Item No. 4 repeats the information provided in Section 2.4.5 of Shell's <br /> 9 October 2009 Work Plan but provides no clarification on how many, if any, soil samples <br /> will be collected from each boring. Therefore, we will require Shell to submit a minimum of <br /> three soil samples from above the groundwater table, from each of the proposed Area 2, 3, <br /> and 4 borings for chemical analysis for the constituents of concern (CDCs). These soil <br /> samples generally should be collected based on photoionization detector (PID), olfactory, <br /> or visual detectons, or else where other physical parameters indicate that chemical <br /> analysis would provide additional data on the distribution of vadose zone contamination. <br /> Item No. 3 provides no clarification on how soil vapor sampling will be conducted for the <br /> proposed risk assessment. Shell's 6 November 2009 Scope of Work states that soil vapor <br /> sampling will be performed, if necessary. Therefore, we will require Shell to submit a soil <br /> vapor sampling plan if it is determined that soil vapor data are needed to conduct the <br /> proposed risk assessment. <br /> 2. We concur with the well Monitoring Plan. However, the report of results must (1) describe <br /> the protocol that will be used to calculate how many well casings are purged and (2) state <br /> how many well casings were purged by running the tap for five minutes. The report must <br /> also provide an update on Shell's efforts to obtain access to sample well No. 4. <br /> In a 27 January 2010 email, Shell estimated that well installation would have to be delayed <br /> until the onset of drier weather to permit heavy equipment access, and the well installation <br /> report would be submitted by June 2010. In discussions during our 23 February meeting, Shell <br /> estimated that the residential well sampling would commence on 5 April 2009. Therefore, by <br /> 18 June 2010, please submit a report of the soil and groundwater investigation and the <br /> residential well monitoring. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4811 or by <br /> email at betaylor@waterboards.ca.gov. <br /> rian ylor, P.G. <br /> Engin ering Geologist <br /> cc: Mr. Jeff Gaarder, Conestoga-Rovers & Associates, Sonoma <br /> Mr. Mike Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Ms. Eileen Nottoli, Allen Matkins Leck Gamble & Mallory LLP, San Francisco <br /> Mr. Shailendra Ganna, Shell Global Solutions (US) Inc., Houston, TX <br /> Mr. David Corliss, Golden State Developers, Walnut Creek <br />