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Mr Peter MacNicholl February 21, 2009 Page 4 12.Section 3.2.1 The detection of dieldrin in LM109B should be addressed. Note also the vertical downwards gradient in the lower zone. The section should be revised. 13.Section 3.3.3 It is not clear that the dieldrin is sorbed at all. The observation that dieldrin is in filterable form does not prove it is sorbed to anything, only that it is not dissolved. The section should be revised. 14.The distance that dieldrin can move under pumping gradients is indeed a function of particle size in the aquifer, and if the observation wells are not screened in exactly the same channel stringer will yield misleading results. The Cooper-Jacob straight-line method is inappropriate for these materials, and yields results that do not match the observed behavior of the plume. The section should be revised. 15.Figure 3-1 An overlay of the hydraulic head contours (using TIN) would be useful on this figure. The figure should be revised 16.Section 4.1.1 The first sentence obviously contradicts the plume maps. The extent of the plume can be explained by dieldrin traveling at groundwater velocities as an unretarded and non degraded particle. Adsorption behavior would be shown as strong retardation, and this is not observed. Instead, it looks like dieldrin is simply being filtered out. There is no compelling evidence for dieldrin being in soluble form or for adsorbing onto carbon or anything else. Instead, the dieldrin is behaving like a nanoparticle that moves if the velocity is high enough. The observation that dieldrin can be remobilized by pumping directly contradicts the statement that it is adsorbed. The conceptual model is flawed and does not explain the observed movement of the plume. The section should be revised. 17.Section 4.4.1 GSU disagrees that sorption is a significant mechanism. Kos is a measure of partitioning to organic matter, not soil particles which are principally silica. Dieldirin is not sorbing to soil, if it sorbs to anything, it sorbs to organic carbon. No organic carbon data has been presented. Revise or remove. 18.Section 4.4.1 GSU disagrees that volatilization is a significant mechanism. In any case, unless organic carbon is present, the assumption that sorption is involved is questionable. Revise or remove. 19.Please present data for the amount of organic carbon in the aquifer. If data are available, they should be discussed, and if no data are available, then this must be considered conjecture. The section should be revised.