SITE INFORMATION AND CORRESPONDENCE 1993-1995

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James L. Tjosvold, P.E. April 12, 1995 Page 3 groundwater plume in the A and B Zones. Upon approval of this Work Plan by DTSC and the RWQCB, PG&E will install these additional wells. PG&E will also take monthly groundwater level measurements to determine the groundwater flow gradient in A, B and C Zones (for the next six months). At the February 28, 1995 meeting, the groundwater monitoring program was modified to the following: • Interior monitoring wells; MW-4 (A Zone), MW-5 (B Zone), MW-8 (A Zone) and MW-13 (C Zone), will be monitored semi-annually (March and September schedule). • All other monitoring wells (perimeter wells) will be monitored quarterly. • Monthly groundwater level measurements well be taken for six months. After six months, the need to continue monthly water level measurements will be evaluated. • One round of TPH as diesel and gasoline, and barium and antimony sampling will be performed in March, 1995. After this, the need to continue monitoring for these parameters will be evaluated. The RWQCB mentioned that the odor threshold for gasoline and diesel is fairly low (in the range of 100 ppb for diesel and 5 ppb for gasoline). Therefore, they suggested that the detection limit for TPH-gasoline be lowered. • Quarterly monitoring reports are to be submitted one month after the end of the quarter (e.g. at the end of April for the first quarter of this year). On March 14, 1995, PG&E submitted the"Final Phase III Technical Memorandum, Stockton Former Manufactured Gas Plant Site, Pacific Gas and Electric Company", to DTSC and the RWQCB. This final Technical Memorandum incorporates DTSC and RWQCB comments on the January, 1995 Technical Memorandum. The first round of groundwater sampling for 1995 occurred on March 13-14, 1995. Laboratory results were available April 10, 1995. A quarterly monitoring report containing the results of this groundwater monitoring round will be submitted to DTSC by May 1, 1995.