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CG III IIIIIIIIIIIII III 'NMENTAL • CONSTRUCTION • COMPLIANCCE~ <br />T~ <br />~pR •~.0 ~~pO <br />~ ` ~uotoBY <br />~,nccs <br />,~; ~~s~;.n c.. <br />March 14, 2000 <br />Mr. Roger Doak <br />Colorado Department of Public Health and Environment (CDPH&E) <br />Hazardous Materials and Waste Management Division <br />4300 Cherry Creek Drive South <br />Denver, CO 80246-1530 <br />RE: Rcsponse to Column Testing Comments <br />Proposed Varna Coal Ash Proposal <br />Weld County, Colorado <br />CGRS No. 1-135-2755 , ,l - ,t `'t~~ L` - ~ `' 7 <br />Dear Mr. Doak: <br />This letter address issues presented in your correspondence and attachments dated Febmary 23, <br />2000 regarding our proposed column testing method. I have attached your letter for reference. My <br />comments to your issues are provided below. <br />I. We do anticipate using bottom ash during the pilot project. The reuse of bottom ash is on the <br />order of 100% because of its value and would not be used in any large-scale project. <br />Nevertheless, we will conduct column testing of the bottom ash in addition to the fly ashes. <br />2. Information provided by Terracon Geotechnical Services indicate the in place density of <br />gravel at the Varna quarry is approximately 118 pounds per cubic foot (1.89g/cc) at an <br />average moisture content of 13 percent. This means the dry bulk density is approximately <br />1.67 grams per cubic centimeter. The dry bulk density of ash used on previous experiments <br />varied between 0.90 and 1.20 grams per cubic centimeter, which is comparable to published <br />values for ash. <br />CGRS has initiated a leaching experiment using the ashes as described in the enclosed <br />Quality Assurance Project Plan (QAPP). The calculated density of the gravel for this <br />experiment is 1.91 grams per cubic centimeter. The calculated density of the ash is 0.915 <br />grams per cubic centimeter. Calculations are presented in Attachment A. These data show <br />that the in situ field density o(the gravel is closely approximated. The in-place density of the <br />ash is also comparable to published data and previous experiments. <br />P.O. BOX 1489 FORT COLLINS, COLORADO 80522 PHONE: 970-493-7780 FAX: 970-493-7986 <br />