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<br /> <br />~_ - <br />• <br />,~ III IIIIIIIIIIIII III <br />STATE OF COLC>RADO <br />pEPARTMENT OF HIGHWAYS <br />4201 East Arkansas Ave. ~~t`. <br />Denver, Colorado 80222 <br />(303) 757-9011 ~W~ ;~~8 <br />`~ September 25, 1986 <br /> <br />Mr. James McArdle <br />Mined Land Reclamation Division <br />Room 423 Centennial Building <br />1313 Sherman Street <br />Denver, CO 80203 <br />Dear Mr. McArdle, <br />Nov t a uses <br />MINED LAND <br />RECLAMATION DIVISIOPI <br />We have serious concerns with Valco's mining operation north of Lamar in the <br />Arkansas River immediately downstream of our two state highway 50 bridges. <br />This pit is referred to as the Lamar North Pit with MLR permit no. 77-572. <br />Our first concern is with the large dike that is blocking a mayor poc•tion of <br />our two 568' long, nine span bridges; structure numbers L-26-D and L-26-H. <br />Attached is a contour map showing our roadway fill, bridge location e.nd <br />Valco's dike. These bridges will handle the estimated 100 year discb.arge of <br />40,000 cfs as published in the May 1982 Federal Emergency Management Agency <br />(PEMA) study for the city of Lamar. with Valco's dike blocking our bridge <br />opening, the flood capacity is reduced to about 8,000 cfs before causing <br />overtopping of SH 50 north of our bridges. <br />Our second concern is the high risk of structure failure that is likely to <br />occur during a mayor flood as a result of Valco's deep excavation within 200 <br />feet of our bridge foundations. When a flood flow increases sufficiently to <br />breech Valco's dike, flow into the pit excavation will result in rapid <br />headcutting progressing upstream under our bridges. Our bridge faundaations <br />are not designed to withstand this amount of streambed degradation. :fhe <br />replacement value of these two bridges is over three million dollars. The <br />roadway user cost would be 526,000 per day since a ten mile detour would be <br />needed. <br />