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<br />Taylor Bayou Watershed Master Drainage Plan <br /> <br />1.0 EXECUTIVE SUMMARY <br /> <br />A Master Drainage Plan was developed for the Tax Increment Reinvestment Zone #1 (TIRZ) <br />and areas contributing to the Taylor Bayou watershed within the City of La Porte. This master <br />drainage plan addresses mitigation and drainage infrastructure requirements and consists of a <br />complete impact analysis for the ultimate development of the TIRZ. A detailed watershed <br />analysis was performed using HEC-l computer models. .The impact analysis concluded that the <br />proposed development of the TIRZ would increase peak flows in Taylor Bayou at the <br />confluence of Taylor Bayou (HCFC Unit Al04-00-00) and its unnamed tributary (HCFC Unit <br />A104-l2-01) by 1,200 cfs. <br /> <br />A detailed mitigation analysis was performed using PONDP ACK pond routing analysis. The <br />routing analysis concluded that approximately 339 ac-ft of detention mitigation would be <br />required to offset the increase in peak flows due to the TIRZ development. The drainage <br />analysis determined that three separate detention ponds and two waterway corridors totaling <br />about 53 acres in size will provide the necessary detention volume. <br /> <br />This study also investigated the hydraulic capacity of proposed channel improvements within the <br />TIRZ. The hydraulic analysis was performed using Manning's Equation and calculating the <br />normal depth of the proposed channels at ultimate conditions. Waterway corridors were also <br />proposed within the TIRZ to provide additional detention and conveyance. Since the waterway <br />corridors were sized primarily for additional detention volume, a hydraulic analysis of the <br />waterway corridors was not necessary. <br /> <br />The estimated construction cost of the proposed improvements associated with the master <br />drainage plan is $10,759,020 including a 20 percent contingency. <br /> <br />2.0 INTRODUCTION <br /> <br />The City of La Porte identified the need to prepare a Master Drainage Plan (MDP) for the Taylor <br />Bayou Watershed to accommodate the planned future development within the Tax Increment <br />Reinvestment Zone #1 (TIRZ). The MDP would analyze the existing development and <br />associated drainage facilities within the TIRZ and identify the additional drainage infrastructure <br />requirements and the detention facilities needed to serve planned future development within its <br />boundary limits and other contributing areas. The general planning objectives for this study are <br />noted as follows: <br /> <br />CivilT ech <br />Engineering, Inc. <br /> <br />1 <br />