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of about 15.8 (NAVD 88, 2001 Adj.) and was determined by plotting the 100-year water <br />surface (EL=18.0) and 10-year water surface (EL=14.4) on Log -Normal paper. <br />Evaluation of a 3-year design and 5-year design resulted in similar hydraulic results. The <br />resulting cost differences between a 3-year and 5-year design is approximately twenty <br />percent (20%). Fairmont Park East is located in an area that does not have overland relief <br />for sheet flow for the extreme even; for this reason, the storm systems presented as <br />Alternatives were developed based on a 5-year frequency for additional level of <br />protection. <br />2.5.2 Hydraulic Grade Line <br />Ponding in the side streets adjacent to Fleetwood Drive is a result of the theoretical <br />hydraulic grade line (HGL) is above the natural ground. When the theoretical HGL is <br />maintained in the pipe or below natural ground then the storm sewer is considered <br />adequately sized. Fleetwood Drive is approximately 1.0 feet to 1.5 feet above the sag <br />locations of the crossing streets; therefore, to keep water from ponding in these areas the <br />theoretical HGL should be at about 1.5 feet lower than the profile of Fleetwood Drive. <br />Each of the alternatives presented here keep the HGL below the profile of Fleetwood <br />Drive until Linwood or S. Spruce. This is can is easily remedied based on additional <br />capacity downstream. For the purpose of this report, the areas of repetitive losses were <br />the focus. The added cost of increasing pipe sizes is negligible for the additional <br />protection upstream. <br />1-8 <br />Klotz Associates Project No. 0127.009.000 Fairmont Park East & Brookglen Drainage Study <br />May 2009 City of La Porte <br />