Laserfiche WebLink
Mr. Marshall Cloud <br /> May 17, 2006 <br /> Page 2 <br /> DTSC has reviewed the technical memorandum and has the following comments: <br /> Comments: <br /> 1 . Page 1, section 1.0, last paragraph; DTSC agrees that the South Balloon location <br /> selected for the in-situ chemical oxidation injection pilot study does have <br /> downgradient monitoring wells to monitor the oxidant performance. In addition, <br /> the associated drilling costs for the South Balloon will be less than the Central <br /> Area due to the shallower TCE contamination. DTSC recommends that DDJC- <br /> Sharpe evaluate implementing an alternative in-situ technology pilot study for the <br /> Central Area TCE plume. The Central Area plume has concentrations almost <br /> four times greater than the South Balloon plume, occupies the largest aerial <br /> extent of TCE contamination, and the plume's leading edge is located beneath <br /> part of the Lyon Estate Homes development west of the DDJC-Sharpe base <br /> boundary. Given the current hydraulic influence from downgradient extraction <br /> wells (EW) EWCC1 and EWCC3 in the Central Area and the presence of several <br /> multi level monitoring wells, the Central Area might be a viable location to <br /> evaluate an in-situ chemical oxidant injection/extraction system. <br /> 2. Page 2, second paragraph, first sentence; Please indicate in the report the <br /> average distance of the second cone-penetrometer (CPT) push location to the <br /> initial CPT location. DDJC should verify that the second CPT push location's <br /> lithologic results are not skewed by being placed too close to the initial CPT <br /> lithology hole. DTSC's concerned that the localized deformation of the soil matrix <br /> from the first CPT push might skew the results of the second CPT push if placed <br /> too closely together. <br /> 3. Page 3, second paragraph, first sentence; The report should discuss the <br /> orientation of the three pushes to each other and describe whether a discernable <br /> sample orientation was established for each set of CPT borings. <br /> 4. Page 19, Table 1; Table 1 identifies nested wells <br /> MW300A/MW300AB1/MW300AB2 as being located in the North Balloon. <br /> Reviewing Figure 1 showing sampling and well locations in the North Balloon <br /> does not contain the previously identified wells. Figure 1 shows <br /> MW300A/MW300AB/MW300B but does not identify <br /> MW300A/MW300AB1/MW300AB2. Similarly, Figure 4 cross-section of the North <br /> Balloon presents only MW300A/MW300AB/MW300B. It appears there are <br /> discrepancies in the report misidentifying the above-mentioned monitoring wells. <br />