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3. Section 3.1, Background, Page 4 and Section 3.2, North Balloon Results: It appears <br /> that one of the two cross gradient wells as identified in section 3.2 is within the area of <br /> the plume;but the Environmental Protection Agency(EPA) guidance Technical Protocol <br /> for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water indicated <br /> that wells located laterally to the plume should be in areas that are not impacted by the <br /> plume. It appears that well CP1067 is in an impacted area and well CP1066 is in an <br /> unaffected area. Please resolve this discrepancy. <br /> 4. Section 3.2.1, Soils, Page 5 and Figure 1,Monitoring Wells and CPT Locations in <br /> North Balloon, DDJC-Sharpe,Page 18: The description of the cross sections in <br /> relationship to groundwater flow is confusing. The text indicates that the cross sections <br /> are roughly 45 degrees from groundwater flow; but the three flow arrows drawn on the <br /> map suggest different groundwater flow directions,ranging from due north to northwest. <br /> Please revise the text to more accurately describe the relation between the cross section <br /> and groundwater flow. <br /> 5. Section 3.2.2 Groundwater,Page 6: It is unclear from the first paragraph if any <br /> oxidation reduction potential (ORP) values were considered valid. Also variable ORP <br /> and dissolved oxygen(DO)values should not be disregarded as suspect without <br /> considering reasons for fluctuations of these data. For example DO, ORP as well as most <br /> other parameters may change significantly as formation water enters the well and which <br /> is more representative of the aquifer. Please reevaluate DO and ORP data and determine <br /> if the data show a changing trend or if the data are stabilized. <br /> 6. Section 3.2.3,EPA Scoring,Page 7: In the second paragraph, the first and second <br /> sentence use"natural attenuation"to represent two different processes. It appears that the <br /> first sentence refers to natural attenuation as bioattenuation and the second sentence <br /> refers to other attenuation mechanisms. Please distinguish between the different types of <br /> natural attenuation being addressed by each sentence. <br /> 7. Section 3.2.4, other Conclusions and Figures 2 and 3, Geologic Cross Sections A-A' <br /> and B-B': This section indicated that the VOC plume did not migrate horizontally <br /> through Zone A because of low permeability lithology,but it appears from the cross <br /> sections that the plume migrated horizontally through the lower portion of Zone A. In <br /> order to evaluate the conclusions made in this section it would be helpful to include the <br /> zone distinctions for Zone B and C on the cross sections. Also, cross sections <br /> perpendicular to A-A' and B-B' have not been provided; therefore it is difficult to assess <br /> horizontal migration in the east-west direction. Please include saturated Zones B and C <br /> on Figures 2 and 3. Also,please consider providing a cross section perpendicular to the <br /> cross sections of Figures 2 and 3. <br /> 2 <br />