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X-2 8. Because of the permanent nature of Rocky Flats, it was ilssumed that the land use in basins A and B will not appreciably change. 9. Since It i,; unl ikely that Great Wester" Reservoir or Standley l.ake would be fill I coincident with a large storm, It was assumed that no runoff would be tributary from either reservoir except for normal, clear-water releases. 10. All other hasins are assumed to be fully urbanized in the future. I I. There are 2200 acres of open water surf.3ce In the study are., and 75 miles of ditches and canals In the basin. 12. As development occurs in-bas In, there .Ii 1 I be greater emphas is on better bridges and Improved roads. Most existing bridges wi 11 be rep 1 aced fo,r non-hydrau I Ie reasons, 13. The Union Pacific RaJ 1 road embankment Clnd the Sheridan Boulevard embankment necessitate detailed hydraulic investigations due to the I ife hazard Involved if the embankments fa i 1. (Sheets 2, 3, 4 and 5). 14. The study ol'/as limited to the fiood plain of Big Dry Creek and by defi- nition did not give detaIled consideration to the channeis and the basins tributary to the main channel; however, certain alternates are affected by the tributaries. 15. The drawings used to examine the alternates in Ph'lse A are on fi Ie in the offices of the Urban Drainage and Flood Controi District. 16. Once the major drainage system Is planned, designed and constructed, the Initial drainage system falls Into order more easily. 17. The alternates studied were: 1. Flood plain zoning wi th the s tr'uctura I Improvements. 2. Flood plain zoning wi th minimal structura " Improvements. 3. Lined open channel - either gr<lss-I ined or European type. 4. Closed conduit - velocities up to 20 f ps . 5. Pondlng - main channel, tribuU'lry channels and on-site dete'ltion. 6. Deep Tunne I 1,8. The hydrologic Investigations performed for Phase A were reviewed and refined for specific use with the alternate chosen to be studied fur- ther In Phase B.