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centralizers. Your comment about well destruction is correct and should be <br /> written into the permit. <br /> 4. I have included an ExCell spread sheet with some chloride concentration <br /> data from wells near the proposed Atherton and Sandman sites. The <br /> concentrations in these wells are elevated relative to background but not <br /> yet excessive. I do not anticipate very high concentrations (about 1000 <br /> mg/L) at any point in the borehole. I spoke with Gary Williams (661) <br /> 345-9301 who is a technical point of contact for Aquaguard grout. The grout <br /> is a sodium bentonite grout having 30 percent solids when mixed according <br /> to specs in fresh water it has a permeability of 3 x 10-4 cm/sec. Gary <br /> Williams indicated that there would be no problem with the grout upto a <br /> chloride concentration of about 1,250 mg/L. If water having a chloride <br /> concentration of 2,500 mg/L was used to make up the grout 25 percent of the <br /> solids would not set. This would increase the permeability by about 25 <br /> percent (possibly making the grout behave as if it were 25 percent <br /> solids--my comment not his). We should be no where near these <br /> concentrations. <br /> 5. I have attached an article you may be interested in. The authors did a <br /> post audit assessment of well seal performance using sonic logging tools. <br /> They found nor significant problem with pumped grout seals (20 percent <br /> solids) in either the saturated or unsaturated zones. They did however find <br /> problems with the performance of unhydrated chips (which we do not use) and <br /> with concrete seals. I would argue against the use of a concrete based seal <br /> for other than sanitary seal purposes in these wells as concrete seals <br /> crack and separate from the PVC casing with time. Concrete also is <br /> susceptible to degradation with poor water-quality especially sulfate. <br /> I hope I have addressed some of your concerns. The final wells should be a <br /> nice product and I agree with you that we want these wells to preform as <br /> designed long into the future. Let me know how to proceed on this to meet <br /> your needs. <br /> Izzy <br /> (619) 225-6131 <br /> PS--The info I sent Friday did not get through to your e-mail. I resent it <br /> this morning. Let me know if you did not receive it. <br /> (See attached file: Christman et al on Well Seals (2002).pdf) <br /> 4 <br />