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<br />e <br /> <br />Additional study, more public meetings, and new hydrological analysis resulted in four <br />options of the storage and diversion alternative being identified. The four additional <br />alternative options are mutually cxclusive versions of the combination of storage and <br />diversion combined with the East Vine Diversion Canal. Each alternative combines <br />existing detention storage with common features. These four alternative options are: <br /> <br />. Option A) Existing detention, common features, and one 540 acre-feet of new <br />detention on the City of Thornton Property (COTP) plus seven smaller detention <br />facilities, see Figure ES-Al. <br /> <br />. Option B) Existing detention, common features, and one 720 acre-feet of new <br />detention at Dam #5 and #6 site, see Figure ES-B I. <br /> <br />. Option C) Existing detention, common features, and one 320 acre-feet of new <br />detention on the COTP and a 220 acre-feet of new detention at Dam #6 site, see <br />Figure ES-Cl. <br /> <br />e <br /> <br />. Option D) Existing detention, common features, and one 540 acre-feet of new <br />detention on COTP and a new 210-acre feet of new detention at the Happy Cow <br />site, see Figure ES-Dl. <br /> <br />The facilities contemplated for construction as part of the Dry Creek Flood Control <br />Project may lend themselves to phased construction. The proposed phasing schedule is <br />outlined in detail later in thc report. <br /> <br />Benefits generated by implementing the selected alternative include: the removal of 800 <br />structures from the lOa-year flood plain; increased devclopment potential in the lower <br />basin; improved capacity of the L-W Canal; needed flood protection in the Middle Basin; <br />and increased land values throughout the two basins. The recommended projcct also <br />eliminates the direct damage from the 100-year flood event that is estimated at $15 <br />million and expected to further increase. A flood of this magnitude could also result in <br />loss of life, which is not measurable in dollar terms. Damages from lesser, but more <br />frequent, 50 year floods and ten year floods would also be avoided through development <br />of the recommended project. The estimatcd benefit of avoided flood damages, over a fifty <br />year project lifc, is approximately $42 million in year 2001 dollars. To the damage <br />avoidance benefit the Company estimates the value of improvement in water handling due <br />to the pipeline would be $5 million over the fifty year project life, which brings the total <br />benefit to $47 million. The estimated benefit to cost ratio, including other capital projects <br />anticipated by the utility, is 2.19. <br /> <br />After initial field investigation by environmentalists from the City and County plus past <br />environmental work, the identification of jurisdictional wetlands that may be impacted <br />will be required. Threatened and endangered species have not been found, nor has the <br />required habitat for such species in the proposed detention sites. Wetland impacts and the <br />need for mitigation was discussed on October 2,2001 when the wetland expert from the <br />regional US Army Corps Of Engineers (COE) office visited the site with the team's and <br />City's environmentalists. In that meeting it was determined that the potential exists to <br />classify the wetlands in the reach of Dry Creek above the L- W Canal as non-jurisdictional. <br />This would eliminate the nced for a COE 404 permit. A report and a letter requesting this <br /> <br />e <br /> <br />7 <br />