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July 22, 2009 <br />Mr. Ron Bottoms <br />City Manager <br />City of La Porte <br />604 W. Fairmont Parkway <br />LaPorte, Texas 77571 <br />RE: City of La Porte, Texas <br />Diversion of HCFCD Unit B 112-02-00 to Unit B 109-03-00 <br />Klotz Associates Project No. 0 127. 011.000 <br />Dear Mr. Bottoms: <br />Klotz Associates was authorized in July 2009, by the City of La Porte, to perform a <br />hydrologic and hydraulic analysis to evaluate Harris County Flood Control District <br />(HCFCD) Unit B 112-02-00 and determine if redirecting the channel to drain east to Unit <br />B109-03-00 provides a benefit to the Brookglen Subdivision. This report documents <br />downstream benefits and impacts for Unit B 112-00-00 and Unit B 109-00-00 and costs <br />associated with these improvements. This is a preliminary assessment intended to <br />support City staff in identifying possible projects to relieve flooding in Brookglen <br />Subdivision. Klotz Associates is pleased to submit this draft letter report for the City in <br />coordinating with the Harris County and the HCFCD. <br />Understanding <br />A review of the local drainage for the Brookglen subdivision area indicates that the <br />subdivision is drained by storm sewers. The storm sewers have about a 3 year capacity <br />before ponding begins to occur within the subdivision. A review of the subdivision area <br />indicates that there is not any apparent sheet flow path to provide a relief of the excess <br />flows when the storm sewers are at capacity. The LIDAR map also substantiates this <br />issue. During heavy rainfall events the water will pond up within the streets and <br />subdivision areas and causes local flooding of the structures. <br />The Brookglen area has experienced flooding of many of the residential structures. A <br />review of the drainage ditches draining the area including B 112-00-00, B 112-02-00, <br />B109-03-00 and B109-00-00 all indicate that the adjacent channels have fairly good <br />capacity in the channels up to the 100 year event. <br />The B 112-00-00 channel in the area of the Brookglen subdivision is concrete lined and <br />appears to have about a 100 year capacity and is draining part of the City of La Porte and <br />part of the City of Deer Park. This B112-00-00 channel does not have any large detention <br />