Agenda - Public Works Committee - 01/18/2000

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,Disadvantages Valuable commercial property is being used for stormwater pending. Water could potentially remain in the pipe to elevation 854.7, which is higher than the pipe inverts. However, even if the pipe would freeze to elevation 8,54.7, more than 1/,3 of the pipe would remain open. It is unlikely that the pipe would freeze pa.st the 48" ReP's since the pipe is deep. Summary of Alternative 3 Descri0tion , This alternative is simila~r to Alternative 2 except that the proposed pond outlet would connect to an existing storm sewer to the south as shown on Figure 3. The total cost of this alternative is $4:~4,098. Advantages Provides better flood protection that the three "non-pending" alternatives. All pipe inverts are above the pond normal elevation. The portion of storm sewer west of the proposed pond could be installed when needed. Disadvanta¢les · Valuable commercial property is being used for stormwater ponding. A portion of Tungsten Street will need to be reconstructed to install the outlet. Approximately 210 feet of pipe would need to be jacked under Highway 10. tt may be difficult to control the pipe invert at the proposed slope of 0.15%. Discharging to the Tungsten Street storm sewer would influence the existing flood elevation in that system. Summary of Alternative 4 D~es_cription Alternative 4'is similar to Alternative 1 except that the control structure which controls the pond overflow would be located directly south of the existing stormwater pond as shown on Figure 4, All Iow flows would be conveyed to the existing pond for water quality treatment, Flows above elevation 854 would be conveyed to the Sunfish Lake Bird, system with a separate storm sewer line, The total cost of this alternative is $441,375. Page 2 of 3 \\Ha01\Shaxad Docs\Munlcipal~RAMSEY~417~RA417AItSummaria~,doc