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VI. PRELIMINARY DESIGN A. General Based on the results of the alternatives evaluation and comments from the public m(~etings and the City, the concepts from the chosen alternative weTl~ developed into preliminary designs. Each major system in the Orchard A venue drainage basin is delineated on the conceptual plans contained in Appendix B with the associated costs for the facilities included in a summary table in the Economic Analysis section. Although specific types of erosion protection and drop slructures arc delineated on the Preliminary Estimate of Probable Construction Costs, that does not preclude the use of other design materials or design schemes that will serve the intended purpose as well as or better than those presented herein both hydraulically and environmentally. The designs presented in this snldy represent one method of stabilizing the channel. Other methods of stabilization are permined as long as Ihey meet with the approval of the Canon City Engineering Department and other afj(:cted agencies. VII WATER QUALITY A. General Concern regarding storm water quality has been growing through the past decad(~. Recently the Environmental Protection Agency (EP A) has be<m working on regulations for monitoring and the use of best management practices to control storm water. The actual design for any necessary control facilities will vary according to the type of pollutants present. Pollutants enter stormwater in many ways, among which are the following: 1. Pollutants are absorbed as the raindrops pass through the atmosphere. 2. Pollutants are washed off the paved and unpaved surfaces by stormwater runoff. 3. Pollutants that have accumulated since the last storm in sewers, ditches, and channels are picked up by the storm water. B. Treatments Most of the pollutants expected to reach the main stern of the channel should be of the suspended solid variety. However, it may be necessary to sample and analyze the stormwat'~r to determine the exact control measures to implement. Dry basins should be designed in areas where tile ma.in pollutants are suspended :mlids which simply settle out in the basin when the channel velocity drops. However, if dissolved solids, nitrates and nitrites, and soluble phosphorus are present, a wet pond will need to be constmcted to reduce these pollutants. VIII. ECONOMIC ANALYSIS A. General The economic analysis of the channel improvements listed in this study was derived from current construction prices for materials and labor in the Canon City,Fremont County area. In addition, the 1993 edition of the Colorado Department of Highways "Cost Data" was utilized. Estimated probable construction costs were determined for each channcl reach for the selected alternative utilizing the protection scheme delineated in the Alternate Drainage Systems section and on the Conceptional Plans located in Appendix B.