SITE INFORMATION AND CORRESPONDENCE

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Mr. Marshall Cloud March 13, 2008 Page 2 be rebounding in concentrations. Please revise the section to account for the contaminants rebound at Area 3. 6. Page 2-1, Section 2.2.2, first sentence; The report should note that summer temperatures have routinely exceeded the 100 degree benchmark in the summer in the San Joaquin Valley. The text in the report should state "...temperatures range from 60 to over 100 degrees Fahrenheit..." 7. Page 2-11, Section 2.7.6, third sentence; The report should be revised to acknowledge that the use of ground water analytical data in conjunction with modeling outputs are used to determine whether contaminant plumes in groundwater are effectively being drawn into extraction wells' hydraulic influence. The report should be revised to state "Modeling in conjunction with analytical data has been used to determine..." 8. Page 2-20, DDJC-Tracy Water Supply Wells; DDJC-Tracy Water Supply Wells (WSW) WSW007, WSW008, and WSWO09 are indicated to have a total construction depth ranging from 810 feet below ground surface (bgs) to 930 feet bgs and supply DDJC-Tracy with all of its potable water. WSW007 thru WSWO09 are not depicted on Figures 1.2A or 1.26 showing Well Locations for DDJC-Tracy's North End and South End, respectively. DTSC recommends that these wells be shown on relevant figures and diagrams due to the wells' ability to create vertical hydraulic gradients with deeper screen intervals and the casing structure can act as preferential pathway for contaminants to migrate to deep uncontaminated aquifers. In addition, these WSWs should be identified so they can be used as inputs on the DDJC-Tracy Groundwater Model to assist in model calibration. 9. Page 3-3, Section 3.2.3.3, second sentence; The report states that demolition of Solid Waste Management Unit 20 (SWMU 20) -Warehouse 10 is planned. Please identify in the report the timeline of the scheduled demolition and DESJC's plan to notify the regulatory agencies in advance of the fieldwork activities for participation. 10. Page 3-8, Section 3.4.3, Dieldrin in Groundwater; The report does not present the vertical and horizontal extents of dieldrin in groundwater despite dieldrin being the contaminant with the lowest aquifer cleanup level of all the Contaminants of Concern with an Aquifer Cleanup Level of 0.05 micrograms per liter (Ng/L). For consistency the report should present and discuss all relevant dieldrin data to depict its lateral and vertical extents as done with TCE and PCE.