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Mr. Joe Intermill <br />May 6, 2005 <br />Page 3 <br />CIVIL RES7~URCES,LLC <br />ENGINEERS 6, PLANNERS <br />Summary of Chronology: <br />We originally proposed that the mine dewatering volume be conveyed through the box culverts and/or <br />ciroular pipes directly. CDOT responded that they did not believe the structures had sufficient capacity to <br />convey this flow along with the storm flows that would be tributary to each structure. We demonstrated that <br />these structures do have more than adequate capacity and CDOT subsequently responded that they would <br />not allow any of the dewatering volume to be conveyed through the box because of erosional concerns. We <br />offered to discharge the water in an encased pipe through the box culvert or inside the existing <br />circular pipes (pressurized discharge pipe inside an encasement pipe that would be inside a concrete box <br />culvert or pipe) and to add riprap erosion protection as necessary to address their concerns with regard to <br />erosion. CDOT responded that they just weren't going to allow any discharge of water under the highway <br />through the existing structures because if this project was allowed to discharge through these structures <br />then they would have to let everybody else. We stated that we do not believe anybody else has a legal right <br />or desire to access the subject property (that is privately owned) through these culverts. Further, the Porter <br />Seepage Ditch and the Ogilvie Seepage Ditch have the legal right to return water to the South Platte River. <br />Historic Use <br />Historically, these culverts have been used for flow from tail water return ditches from the agricultural lands. <br />Civil Resources' staff stood at the top of the erosion escarpment with DMG staff (Erica Crosby and Tom <br />Schriever) during our site visit and watched agricultural return water being discharged to the Porter <br />Seepage ditch and through the box culvert. The sources of return water have historically included <br />groundwater from agricultural wells and surface rights that were used to irrigate the crops. Testimony from <br />the surrounding land owners, observed use of the ditches for agricultural return flows, and the presence of <br />functioning discharge conveyances is physical proof that this is an historic use of these structures. In <br />response to CDOT's claim that those seepage ditches may have been abandoned, Mr. Villano said, "What <br />do you mean those rights have been abandoned, I watch my tailwater flow through those culverts ditches <br />every time I irrigate my fields." Further, note that the seepage ditches (late 1800's) were of record long <br />before CDOT acquired its Highway 85 right-of-way (1950's) and therefore, the highway right-of-way is <br />subject to prior rights of these ditches. <br />Other mitigating factors with regard to use of the existing structures to convey discharge water include: <br />The miner is responsible for repair of any damage resulting from discharge from the site. The <br />DMG would require corrective actions if any erosional damage is observed. <br />Based on experience on other sites (with larger saturated thickness, coarser aggregates and <br />larger active mining area) we believe that 10 cfs is a more realistic estimate. We intend to <br />use: (1) 2 to 4 cfs of this flow to recharge the aquifer upstream of the project to as a hydrologic <br />mitigation measure; (2)1to 2 cfs in the gravel operation (washing, dust suppression, concrete <br />production); and (3) evaporation and natural silt pond infiltration will further reduce the <br />discharge volume from the site. <br />451 DAK STREET, SUITE ZO9 • P.O. BoX 680. C-REO ERICK, CO BO530 • 1303) 833-1 41 6. (3031 833-285^ - FAx <br />