Drainage_and_Flooding_Report-dated_03-10-08

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�-1 A - REQUEST FOR CITY COUNCIL AGENDA ITEM Agenda Date Requested: November 12 2007 Requested By: Wa ne J. S o� Department: Planning Report: X Resolution: Ordinance; — Appropriation Source of Funds: NA Account Number: NA Amount Budgeted: NA Exhibits: 4/ 4 SUMMARY The Flooding and Drainage Committee, at their October 29, 2007, meeting directed Staff to bring forward to Council a list of short term drainage projects for near -term consideration and future funding. This list contains the projects, in priority, that Staff feels will have a favorable impact on several areas in La Porte. A power point presentation will be given at the meeting. Cost estimates are preliminary and will be refined when the projects go into design; 1) Lower Catlett Drive at its termination point along Big Island Slough near Roseberry Drive which would help residents in Fairmont Park West. In the past Public Works has cut off some of the top bank in order to lower the ponding elevation impacting the homes at the intersection of Catlett and Roseberry Drive. However, in order to alleviate the recent flooding, it is required to cut the street in order to further decrease the ponding elevation. There are two options to the City in this regard. First option is to cut Catlett at one of the two driveways intersecting it and making this the new high point, at which point the new concrete would gently slope down and terminate at its present location. This option would not require the City to replace the two driveways. Jhe second option is to replace the entire length of Catlett from its intersection with Roseberry. This would allow the terminus of Catlett to be further lowered but would result in more concrete being poured as well as the replacement of the two existing driveways from one of the existing joints. The first option would cost roughly $10,000 while the second would cost $65,000. Planning Department is currently analyzing how much mor drop �can be obta� fro implementing Option II in order to determine if the benefit warrants the cos .�"$" a 2) filer the parking lot accessing the City Park at the end of Willow Creek Drive in Creekmont Section II. T1@400-year event in this area is sheet flowing through the park in order to access City maintained ditches which ultimately outfalls into Big Island Slough. The existing parking lot is higher than the GL� finished floor elevations of the homes along Willow Creek and therefore the 100-year event will flood these homes before it is able to sheet flow through the park. Lowering the parking lot and cutting out some of the park will minimize this, The cost for this project is approximately $35,000 and includes the excavation costs associated with the park. Another separate project being suggested by Parks would improve the conveyance to Big Island Slough. 3) Replace the junction box along Driftwood Drive in order for the storm runoff from Fairmont Park East to discharge directly into the detention pond along Driftwood, thereby decreasing energy losses and allowing more water to be taken off Driftwood. In conjunction with this, replace one of the outfall pipes to B 106-02, a tributary of Big Island Slough, with a larger pipe. The impact -to B 106-02 would actually decrease because of the time it would take for the detention pond to fill versus the present situation of the storm runoff discharging directly to B 106-02. Engineering division has run the calculations verifying this assertion. The cost for this project would be approximately $35,000. 4) Upsize the outfall pipe discharging Fleetwood Drive to 13106-02, potentially helping residents in Fairmont Park East. This would decrease energy losses in this drainage system. However, since Fleetwood Drive is the street intended to sheet flow the storm runoff to its ultimate outfall for this area but