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<br />' C-PIT HYDROGEOLOGIC INVESTIGATIONS <br />' TECHNICAL REVISION N0. 8 <br />MINING PERMIT M-1977-208 <br />2. SITE ANALYSIS AND FIELD ACTIVITIES <br />This portion of the report outlines the analysis of relevant historical information fox the Site as well as the <br />specific methods followed by personnel during field activities and data collection. The methods were selected <br />in consultation with DRMS staff during meetings and site inspections held at the CEMEX plant on <br />February 22, 2007 and March 20, 2007. <br />2.1 Historical Records and Aerial Photograph Review <br />Historical aerial photographs of the Site were obtained to aid in determining the chronology of the relocation <br />of the Boulder Feeder Canal to its present alignment, and to determine the timing and extent of mining in <br />and around the C-Pit area. Photos were reviewed fox the following dates: <br />^ May 12, ]979 <br />• October 6, 1986 <br />• September 15, 1989 <br />• May 10, 1993 <br />This date range was selected after a review of the M-1977-208 permit file maintained by DRMS and the <br />historical records for the Boulder Feeder Canal obtained from the Northern Colorado Water Conservation <br />District (NCWCD). A DRMS inspection report indicates that topsoil at the Site had been stripped and C-Pit <br />was ready fox mining by September 13, 1985. Another inspection report dated February 19, 1993 indicates <br />that the "western portion" of C-Pit would be "mined out within two months." Other mine permit <br />documents confirm that CKD placement commenced in C-Pit in 1999. <br />NCWCD records indicate that the relocation of the Boulder Feeder Canal to its present alignment spanned <br />the years from late ]981 to 1987. The relocated portion of the Canal west of C-Pit first carried water during <br />the 1987 irrigation season. The design and initial construction was performed by CEMEX predecessor <br />company Martin Marietta Corporation, working in conjunction and cooperation with the Bureau of <br />Reclamation and NCWCD. The relocated portion of the canal was cut into bedrock at the northern end <br />(immediately west of C-Pit) and transitioned into afill-section at the south end, See Figure 2. The <br />construction of the Canal relocation was performed concurrently with the [Wining of the Foxt Hays Limestone <br />in the area. Once the relocation was completed, title to the Canal right-of--way was eventually transferred to <br />the Bureau of Reclamation. <br />' NCWCD documents dated October 1977, early in the design of the canal relocation project, indicate that the <br />Bureau of Reclamation had concerns that sections of the canal cut into bedrock may require lining to preven[ <br />excessive seepage, depending upon permeability testing. (See the 1977 Bureau of Reclamation memorandum <br />in Appendix B.) However, bedrock seepage tests/data could not be located by NCWCD in its review of <br />historical records. Canal design dxawtngs dated 1981 and prepared by Martin Marietta's engineering <br />consultant have general notes indicating that areas of excessive seepage would require canal hning by either <br />' "shotcxete" or compacted soil. Field inspections by Brown and Caldwell have confirmed the presence of a <br />shotcrete lining in the Boulder Feeder Canal. The lining is now degraded, presumably due to water erosion <br />2.7 <br />' Use of contents on this sheet is Subtecl to the Iimilali0n5 specilied flt the end of this document. <br />\\f3GDEN02tpro)ectslDalalGEN\Gemex\TR-B1Reponmg\CEMEX Report OB-31-0Ltloc <br />