Laserfiche WebLink
Ms. Erica Crosby <br />October 29, 2007 <br />Page 3 <br />although the absence of selenium in the ground water is a positive sign that supports <br />limited hydraulic connectivity. <br />CEMEX Response: CEMEX agrees. <br />h. Conclusions <br />On page 4-1, reference is made that a hydraulic "connection is not evident at <br />compliance well CEM-005." <br />Response: An insufficient number of samples [has] been collected from CEM-005 <br />to confidently draw that conclusion. However, DRMS acknowledges that the <br />presence of only 4 feet of water in the 400-ft deep CEM-005 well is a strong <br />indication of low hydraulic connection. <br />CEMEX Response: CEMEX agreer. At indicated in e. above, we will continue to monitor the depth <br />to water at CEM-0O5. <br />2. The report notes the degxadafion of shotcrete lining within the Boulder Feeder Canal <br />and possibly water migrating to the C-Pit as noted by seeps in the highwall and well <br />vegetated areas. Based on the report, it appears that water from irrigation ditches [is] <br />migrating into the C-Pit. In order to reduce the water Elowing into the C-Pit and coming in <br />contact with the cement kiln dust (CKD), CEMEX will need to provide a plan to limit the <br />seepage flow of water into the C-Pit. <br />CEMEX Response: CEMEX proposes to addnsr the ditch seepage issue in a step-wire fashion, <br />initially focusing an solutions to known problems and assessing the recultr, prior to .pending resources on <br />solvin~potentialproblems that baveyet to be proven. <br />Observations made this part irrigation season along the Boulder Feeder Canal south of the bridge crossing to <br />B-Pit lndicated drat seepage from the Canal in this reach, wlric-b is built on an engineered fill, maker ib~ way <br />to the 54-inch culvert under the Canal discharging to the pond southwest of C-Pit. (See Figure 2 of the <br />TR-8 Report, and photos in Appendix C) In addition, the southwest pond has siren several feet over the <br />course of the summer, and is currently at its highest point. Conversations with the Northern Colorado <br />Water Conservancy District (Northern) have confirmed that flow in the Feeder Canal in recent weeks has <br />been running at 2050 CFS, and will continue to run at approximately Y 0 CFS tenlil November 6, 2007, <br />at which time it will be shut down for this season. <br />In contract to the continuing fZmv in the Feeder Canal, flow in the Swede Ditch (that it contained in the <br />CMP culvert along the top of the western C-Pit hiBhwall) ceased in mid September, 2007 Field <br />observations on October 23, 2007 confirmed that seepage rontinuec to enter C-Pit through fractures and <br />bedding planer in the western highwall. CEMEX has therefore concluded that the primary if not role <br />source of this highwall seepage is from the Feeder Canal and not the Swede ditch. <br />CEMEX proposes the following as an initial phase of work to address seepage into C-Pit: <br />Line 800 feet of the southern reach of the Feeder Canal (that is built on the fill embankment south <br />of the B-Pit bridge) with clay, in the area known to be leaking into the 54-inch culvert Discussions <br />regarding this plan have already taken place with Northern, who will cooperate with CEMEX in <br />this ~orl. This lining project will be completed prior to the 2008 irrigation season, at which time <br />the bighwall and C-Pit water levels will be monitored to assess the ~ect of lining this reach of the <br />Canal. <br />Draft Response to 70-5-07 tldcynncy Revicw_'PR-9_REV2 <br />