03-23-09 Drainage and Flooding Committee meeting minutes

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3. Partial Pavement Improvements with Partial Storm hppTovements - Lower Fleetwood Drive between South Spruce and Mesquite Drive to convey surface runoff from Spencer Road to an overflow swale at Mesquite Drive combined with an additional parallel trunk line from Linwood Drive to the outfall. 4. Pavement and Storm Im rovements - Lower Fleetwood Drive and replace existing storm sewer between South Sycamore and Mesquite Drive. Each configuration was modeled to determine the most economical solution and optimize performance. The overland slope generally decreases from north to south. LiDAR shows that the slope of the land to be at a high point in the vicinity of Dogwood and gradually decreasing from Dogwood to Mesquite. Examination of overland flow shows that storm water generally collects in the depressed streets of Dogwood and Linwood, this is supported by the repetitive loss data in Exhibits 3, 4 and 5. To solve this, Fleetwood Drive can be lowered from South Spruce to Mesquite approximately 1.5-feet. However to keep the HGL below Fleetwood Drive for a 3-year design frequency storm sewer improvements are required up to South Spruce. This alternative is comparable in cost and disruption for the public to other more effective solutions and is not considered. Another consideration is to replace or augment the existing storm trunk line in addition to lowering Fleetwood Drive entirely. This option is considered least desirable by the City of La Porte and most costly at $2.0 million, (See Appendix C) and will not be considered further in this study. 2.5.1 Design Frequency: Alternatives were evaluated based on a 5-year design storm for the main trunk line using a 25-year water surface in the receiving channel and adding additional inlets to accommodated increases in runoff. The 25-year starting water surface is at an elevation 1-7 Klotz Associates Project No. 0127.009.000 Fairmont Park East & Brookglen Drainage Study May 2009 City of La Porte