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r- I I were analyzed fin• selected geochemical properties for 5 quarterly monitoring events (the 5/1/00 event inunediatelyprior to ITRC injection through (fie 5/23/01 event). Table I provides a tabulation ofgeochcmical analytical results. VOC Concentration Graph MW-3 (within HRC grid, adjacent to 00LIrce area) 14,000 - -- — j Excavatio j 12,000 - - j HRC � 10,000 I I nfection I � I 8,000 I i C 6,000 - N U 4,000 2,000 ,SII 0 Y-tib�;� -- /----f�, I ��.✓ -- 1/5/1998 7/24/1998 2/9/1999 8/28/1999 3115/2000 10/1/2000 4/1912001 11/512001 Time(days) -9---PCE '-TCE - —cis-1,2-OCE FIGUKE 2. Chlorinated Hydroem-hon Concentrations W MW-3. DISCUSSION OF COC DATA Figure 2 presents the COC analytical data for the past several years. Near the source arca, groundwater contaminant concentrations for PCE' (4,500 micrograms/liter, ug1l),TCE(1,000 ug/1),cis-DCE(7,300 ug/1),and VC(870 ug/l) were recorded in MW-3 immediately prior to HRC injection (May 2000). As of October 2001 (approximately 18 months after HRC injection), PCL;, TCE, cis-DCE, and VC levels in M W-3 had decreased to 408, 87.4, 438, zinc[ 132 ug/I,respectively. As of the May 23,2001 sampling event,all COC concentrations were below the applicable site target concentrations. Source area monitoring well MW-3 is undoubtedly the most important indicator of the effect of the HRC injection, as it is the well located nearest to the contaminant source area. '['his well has historically had very high PCE concentrations(maximum of 39,600 ug/l on 2/21/96). As recently as 12/2/99, conccutration of PCF in this well was 10,000 ug/l. h»mediately following TIRC inicction, PCE concentrations decreased from 4,500 ug/I (5/1/00 sampling event)to 1,030 ug/l(8/10/00 event). All other COCl, except trans-DCE, also showed decreases in concentrations fi-om the 5/1/00 event(immediately prior to HRC