Agenda - 01-30-1989 - Laserfiche WebLink

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Mr. John M. Link, Jr. December 30, 1988 Page 7 The estimated total project costs for the alternative projects are shown on line 11 of Table 1 , and unit costs per gallon of total and net safe yield are shown, respectively, on lines 12 and 13. Individual project cost summaries are included in the appendix. . Costs have been updated to reflect the revised property requirements and major cost items in dam construction. Previous cost estimates are shown on line 14 of Table 1. Please recognize that the revised estimates are made without benefit of detailed site evaluations that would normally be carried out during the preliminary design process. Such detailed studies would be required to determine the technical and economic feasibility of RCC as an alternative to conventional earthfill dam as well as to refine overall design concepts. For example, alternative spillway designs could be investigated during the preliminary design to help reduce impacts of reservoir construction on the local residents. The feasibility of constructing a dam in two phases, which has been proposed by the Town of Hillsborough, is another concept that can only be fully evaluated after detailed study. While these and other important issues remain to be resolved, we hope that the present report, combined with previous reports, provides the County with an adequate basis for deciding which of the two sites should be developed to provide for the county's future water supply needs. Once this decision is made, we hope that the County will continue to provide an appropriate level of protection for the other site to preserve the long term potential for additional water supply development. The Phase I report identified the Eno River at McGowan Creek and Seven Mile Creek as the two : .� most favorable dam sites in northern Orange County. The County may continue with to consider non-local but othese stwo csites Jwillnremaino the�best contracts available local options. The findings of the present study can be summarized as follows: 1 . The Eno River site above McGowan Creek will yield more water for the County and at a lower unit cost than an alternative _ reservoir on Seven Mile Creek. 2. Development of the Eno River alternative would impact four significance: Fau cette s Mill structures of know historical g would be completely inundated; Chatwood, Little Ayr Mount, and The Elms would be affected to some extent, the buildings themselves would not be inundated. Development of the Seven Mile Creek site would not have any significant impact on any structure of known historical significance. For this reason, permitting requirements for the Seven Mile Creek -:site:-should be less complicated.. -. 3. Development of the Seven Mile Creek site to create an impoundment volume of 2100 million gallons and a safe yield of 6 mgd would have the least environmental impacts of the alternatives that have been evaluated. This project would permanently inundate approximately 360 acres of land as compared with•400 acres for the higher yielding reservoir at the Eno River site. The reservoir proposed by the Town of Hillsborough would permanently inundate over 700 acres.