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III IIIIIIIIIIIII III ~ ~ <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Dnpdrlmenl of Ndhrra Resourres <br />1 { I S Sherman SL. Room ? I3 <br />Drnver, GJrrrarlu NO'_OS <br />Phone: 1311 it 966-3 Shi <br />F,47(: I SU h 932~NIU6 <br />February 12, 1999 <br />Mr. Scott Hoover <br />B & B Excavating. Inc. <br />Drawer 249 <br />si <br />DEP,gRT1~tENT O~ <br />NATURAL <br />RESOURCE: <br />Ruy Romer <br />Governor <br />Lime. 5. Lnchhavl <br />E~eu~nve Dveaor <br />hurha,~l P Lung <br />Vai1,C0 S16~3 Uivi~ion Dvi¢ior <br />RE: Amendment to Sampling and Analysis Plan, Montgomery Pit, Permit No. M-36-104 <br />Dear blr. Hoover: <br />The Division of Minerals and Geology (DMG) has completed a review of the "Amendment to <br />Sampling and Analysis Plan" (SAP amendment) for the Montgomery Pit herbicide release. The SAP <br />amendment was prepared by Greg Lewicki and Associates and submitted to DMG on February 2, <br />1999. The following issues remain to be addressed to the satisfaction of DMG prior to implementation <br />of the SAP amendment. <br />Please provide a statement that those portions of the Draft Sampling and Analysis Plan <br />prepared by Dames and Moore and submitted to DMG on December 13, 1999 that are not <br />modified by the SAP amendment will remain as components of the sampling and analysis plan. <br />Specifically, sections 4.4, 4.~, 4.6, 4.7, 5.0, and Appendix D from the Dames and Moore <br />sampling and analysis plan must be adhered to during implementation of the SAP amendment. <br />Tn addition, pertinent portions of section 43 must be adhered to relative to the procedure for <br />conducting ambient temperature headspace testing with the photo-ionization detector. <br />2. Under the terms of the SAP amendment, an on-site hazardous waste repository and treatment <br />cell may or may not be needed depending on whether or not contamination in excess of 10 <br />mg/kg 2,4-D is found at [he site. The DMG suggests that the treatment cell be constructed with <br />a composite liner rather than with the clay liner that is proposed, for the following reasons: <br />a) It is not known how long i[ will take for the 2.4-D to decompose to below the 10 mg/kg <br />limit in the treatment cell. During the period that the hazardous material is present in <br />the cell a clay liner would be susceptible [o damage by desiccation cracking and <br />freeze/thaw effects. <br />h) 2,4-D, bromacil. or diesel fuel may permeate through the day and be released to the <br />environment during the period of storage in the treatment cell. The likelihood of [his <br />occurring would be increased if any precipitation were to accumulate in the cell. <br />Assuming a hydraulic conductivity for the clay of 4.7 x l0' m/s and an areal extent for <br />the cell of LS00 square fee[, permeation of contaminants through the proposed 6 inch <br />