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Stantec Co ting Corporation vd�— ID 3017 Kilgore Road Suite 100 Rancho Cordova CA 95670 Tel:(916)861-0400 SEP u u 2008 Fax:(916)861-0430 Stantec PERPAIT%SERV10ES September 19, 2008 Mr. Brian Taylor California Regional Water Quality Control Board — Central Valley Region 11020 Sun Center Drive, #200 Rancho Cordova, California 95670 RE: Response to RWQCB July 30, 2008 Letter Stockton Terminals Technical Committee Facilities Port of Stockton Stockton, California Stantec Project No. 77OT.43673.014.0002 Dear Mr. Taylor: On behalf of the Stockton Terminals Technical Committee (STTC), Stantec Consulting Corporation (Stantec, formerly SECOR) submits this response to the July 30, 2008 Regional Water Quality Control Board (RWQCB) letter, related comments in the May 30, 2008 RWQCB letter, and an email from the RWQCB caseworker on September 10, 2008. In general the comments relate to formally establishing a list analytes for the evaluation monitoring program (EMP) and a recommendation to include tertiary butyl alcohol (TBA) in that list. This issue was also discussed during the June 5, 2008 meeting at the RWQCB attended by representatives of STTC and Stantec. The May 30, 2008 RWQCB letter had not been received by Stantec or STTC prior to the June 5, 2008 meeting. Specifically, the issue was first raised by the RWQCB in Comment Number 2 of the May 30, 2008 letter. • "The data trends show that TBA sustained concentration increases over three consecutive quarters, in excess of the only existing historical data point of <5.0 ug/L, from May 2006 to November 2006, and from August 2007 to February 2008. The February 2008 detection of 9.4 ug/L is the highest TBA concentration ever observed in AR/MW-18B. However, TBA is not among the list of trigger hydrocarbons in the ozone injection monitoring program. The recent detections of TBA in remedial observation well AR/MW-18B shows that the STTC needs to calculate an historical average for this constituent, establish a list of "trigger" hydrocarbons including the historical average for TBA, and monitor this constituent to ensure that off-site migration is not occurring." In the July 30, 2008 letter, Page 2 Paragraph 2, the RWQCB stated in part regarding discussions held in the June 5th, meeting: • ...However, the document does not list the specific hydrocarbons that trigger application of the contingency plan. On behalf of ARCO, Mr. Haeck, said that he would be in touch I:\STTC-Stockton\Reports\Resp to RWQCB July 30,2008\Response to RWQCB July 30,2008 Letter final.doc