Agenda - Public Works Committee - 01/18/2000

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pond alternative. When compared to the recommended Alternative #1, the pond alternative is actually more expensive: These two pond alternatives were eliminated from consideration because of project economics, and because the land lost due to ponding is likely to have significantly more value in the future as developable land. The difference between Alternatives #I and #4 and Alternative #5, is the ultimate location of the outlet. The suggestion to evaluate the use of the Sunwood Drive storm sewer came out of the December 20th meeting with the property owners. Initially, there was concern over the capacity of this storm sewer. However, discharge to this storm sewer would be an infrequent event and would occur after the peak discharge from an intense storm had passed. It is a viable alternative and one which is less costly than crossing Highway #10 and discharging to Tungsten Street. The difference between Alternatives #1 and #4 relates to an issue of water quality treatment and the directional movement of stormwater in the sewers. Alternative #4 has a storm sewer carrying all storm flows to the regional pond, and a separate overflow pipe carrying the filled pond discharge back to the Sunfish Lake Blvd. outlet. Alternative #1 utilizes a single pipe to handle both functions. Under most storm events, runoff would be carried to the regional pond, In rare events, when the pond becomes full, flow would back up and rise within the storm pipe until it would reach an elevation of 855.2 in a control structure on the west end of the storm line. The flow in the storm pipe would then reverse direction and flow westward into the Sunfish Lake Blvd. storm outlet. Staff is recommending finalizing the study utilizing Alternative #1. Finally, in completing the feasibility study, the value of the outfall from the regional pond will need to be identified as a cost being contributed from outside the taxing district. I would suggest that the cost of the 15" and 18" outfall sewer, identified in Alternative #4, be used for this purpose, however other cost-shared methods may be considered between the Business Park 95 and Highway #t 0 based on proportional areas. Committee Action: Motion to direct staff to finalize the feasibility study utilizing one or more of the alternatives presented. Provide direction on how the value of the outlet from the Business Park 95 pond should be quantified. Reviewed by: City Administrator City Attorney Director of Public Works PW: 01/18/99