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Groundwater sampling was performed March 19 through March 20, 2001.� Ten onsite wells were sampled: 1, 2, 9, 10, 11, 16, D, I, MW1, and MW2.� In addition, one of the offsite wells, Well LS-7, was sampled.� As noted in the Introduction to the Quarterly Groundwater Monitoring Program at CSSA, Wells G and H were not sampled due to inoperable sucker rods in these wells.� The data package RL74-15 contains the VOC and metals analytical results.� The data package was received by Parsons ES on April 13, 2001, validated and submitted to AFCEE on April 26, 2001.� Analytical results for March 2001 are presented in Table 2.� VOC trends over time for Well 16 are depicted graphically in Figure 3.� Historical VOC and metals data can be found in Tables 6 and 7, respectively, of the Introduction to the Quarterly Groundwater Monitoring Program at CSSA (Parsons ES, 2001).
Maximum contaminant levels (MCLs) for TCE, PCE, and cis-1,2-DCE were exceeded in Well 16 during the March 2001 sampling event.� The PCE concentration was 125.68 �g/L, the TCE concentration was 150.60 �g/L, and the cis-1,2-DCE concentration was 141.18 �g/L.� The initial run for these three Well 16 VOC analytes (TCE, PCE, and cis-1,2-DCE) exceeded the calibration range.� The sample was reanalyzed at a dilution factor of 5.� The concentrations of these compounds from the undiluted run are inaccurate.� The concentrations of all three compounds increased from the levels found in Well 16 during the December 2000 monitoring event.� The December 2000 levels of PCE (85.65 �g/L), TCE (95.7 �g/L), and cis-1,2-DCE (110.75 �g/L) in Well 16 were the lowest concentrations recorded for this well since December 1995 (see Figure 3). A low concentration of trans-1,2-DCE was detected in Well 16 at 0.49 �g/L and a chloroform concentration of 0.13 �g/L was also found.
The TCE (91.4 �g/L), PCE (63.55 �g/L), and cis-1,2-DCE (77.73 �g/L) concentrations in Well D were also above MCLs.� The initial run for these three Well D VOC analytes (TCE, PCE, and cis-1,2-DCE) exceeded the calibration range.� The sample was reanalyzed at a dilution factor of 5.� The concentrations of these compounds from the undiluted run are inaccurate.� The December 2000 levels of TCE (82.5 �g/L), PCE (63.62 �g/L), and cis-1,2-DCE (83.72 �g/L) in Well D were similar to the results from this monitoring event. Well D had a trans-1,2-DCE concentration of 1.93 �g/L and chloroform was detected at 0.11 �g/L.
The concentrations of PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE in Well MW1 were 24.56 �g/L, 27.8 �g/L, 27.2 �g/L, and 2.55 �g/L, respectively. The concentrations of all these compounds increased from December 2000 levels of 15.76 �g/L, 16.8 �g/L, 16.94 �g/L, and 1.36 �g/L, respectively.� As was true for the December 2000 results, the MCLs for PCE and TCE were exceeded. The relative proportion of these compounds in Well MW1 remained stable.
Well MW2 also experienced an increase in PCE, TCE, and cis-1,2-DCE concentrations from December 2000 levels but an increase in the trans-1,2-DCE concentration was not observed.� PCE and TCE concentrations were above the MCLs in this well at 9.31 �g/L and 9.80 �g/L, respectively.� The trans-1,2-DCE concentration was 0.27 �g/L and the cis-1,2-DCE concentration was 4.63 �g/L.� The duplicate groundwater sample from Well MW2 exhibited approximately equivalent concentrations of PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE as the normal sample.
Off-post Well 1 had a sub-RL TCE concentration of 0.2 �g/L which is a reduction from the December 2000 level of 1.2 �g/L.� The December 2000 result was significant because it was the first occurrence of a TCE concentration exceeding the RL in this well. The first recurrence of PCE in Well 1 since March 2000 was observed during this monitoring event at exactly the same level (0.11 �g/L) that was found at that time.
PCE was detected at levels below the RL in Wells 9, 10, and 11 at concentrations of 0.11 �g/L, 0.11 �g/L, and 0.16 �g/L, respectively.� PCE has not previously been found in Wells 9 and 10, which are generally down gradient from Well 11, but was detected in Well 11 during June 2000 at a concentration of 0.41 �g/L.� Additionally, cis-1,2-DCE and TCE were detected in Well 11 for the first time at concentrations of 0.38 �g/L and 0.2 �g/L, respectively.� These compounds were not observed in Wells 9 or 10, however.� Chloroform was detected below the RL in Well 10 at a concentration of 0.21 �g/L but was not detected in Wells 9 and 11.
Cadmium was not detected in Well 1 during this monitoring event after exceeding the MCL of 0.005 mg/l during December 2000.� The lead concentration of 0.0131 mg/L in Well 1 was just below the action level (AL) of 0.015 mg/L after two consecutive detections that exceeded the AL in this well.� The AL for lead was exceeded in Well 11 for the first time during the December 2000 monitoring event but the lead concentration of 0.0072 mg/L detected in Well 11 during this monitoring event was below the AL.� No metal concentrations exceeded MCLs/ALs during this monitoring event.
A sample was collected from private Well LS-7 during this sampling event and was analyzed for VOCs only.� No contaminant levels above MCLs were found.� PCE was detected at a concentration of 3.76 mg/L, which is a slight increase above the December 2000 level of 3.73 mg/L.� Aside from the June 2000 results, where the PCE level dropped below its initial level, the presence of PCE has generally been increasing in Well LS-7 since sampling began over a year ago in December 1999.
TCE exceeded the RL for the first time in this well during the December 2000 sampling event at a concentration of 1.2 mg/L. It was detected at a concentration below the RL, 0.2 mg/L, during this sampling event.� Chloroform was not detected in Well LS-7 for the second consecutive monitoring event after being identified at levels below the RL during the three monitoring events prior to December 2000.� The results of all sampling events for offsite wells are listed at the end of Tables 4 and 5 in the Introduction to the Quarterly Groundwater Monitoring Program at CSSA.