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April 2014 3 10381640A <br />titanium dioxide (TiO2), and zinc oxide (ZnO). The results are provided in Appendix A. The CKD samples <br />were primarily composed of the following: <br />■ Greater than 50% calcium oxide (CaO), <br />■ 10 — 20% silicon dioxide POO <br />■ Less than 20% sulfur trioxide (SO3) <br />■ Less than 10% combined metal oxides including: aluminum oxide (Al2O3), iron oxide <br />(Fe2O3), manganese (III) oxide (Mn2O3), strontium oxide (SrO), titanium dioxide (TiO2) <br />and zinc oxide (ZnO). <br />Holcim tested the CKD by the Toxicity Characteristic Leaching Procedure (TCLP) using US EPA Method <br />1311. The TCLP is specifically designed to assess leaching potential of a material from contact with <br />municipal solid waste leachate. The TCLP leachate was analyzed for the following list of metals: <br />antimony, arsenic, barium, beryllium, cadmium, chromium, copper, lead, manganese, mercury, nickel, <br />selenium, silver, titanium, and zinc. These results are generally at least an order of magnitude below the <br />regulatory limit used for hazardous waste classification (40 CFR 261). The exception is selenium, which <br />has a regulatory limit of 1 milligram per liter (mg /L) while TCLP values ranged from < 0.1 to 1 mg /L. The <br />results are provided in Appendix A. <br />2.3 Previous Hydrogeologic Investigations <br />Secor performed a hydrogeological assessment of the CKD disposal area A2 on behalf of Holnam Inc. <br />(Holnam). Details of the Secor hydrogeologic investigation are reported in Secor (1998). Three <br />groundwater monitoring wells (MW -1, MW -2, and MW -3) were installed in June 1998 and a fourth <br />monitoring well (MW -4), was installed in April 1999 in the vicinity of CKD disposal area A2. Based on the <br />Secor report ( Secor 1998), the monitoring well screens were installed across the Niobrara /Codell contact <br />for MW1 through MW -3; this information was not provided for MW -4. Table 1 provides a summary of the <br />known well construction details of these monitoring wells. Appendix B provides monitoring well <br />construction and lithological logs for monitoring wells MW -1, MW -2 and MW -3. No monitoring well <br />construction details are available for monitoring well MW -4. <br />Slug tests were completed in the wells to estimate the hydraulic conductivity of the surrounding geologic <br />formation. Secor conducted in -situ hydraulic conductivity testing in three monitoring wells (MW -1, MW -2, <br />and MW -3) in 1998. Golder performed a hydraulic conductivity test on monitoring well MW -4 as part of the <br />September 2010 groundwater monitoring event. Table 2 provides a summary of the hydraulic testing <br />results. <br />h <br />Golder <br />\, Associates <br />i 0\81640a\ 0400\ gv charwellinstallfiNdrep _fnl- 30apr14 \10381640a gwcharrpt _holcim- hoettcher_(nl- 28apr14- with holcim edi[s.docx <br />