05-21-09 Regular Meeting,Public Hearings,and Workshop Meeting of the La Porte Planning and Zoning Commission

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Preserve at Taylor Bayou June 24, 2009 Page 3 of7 Right Turn Lane - The study mentions the future TxDOT Highway 146 improvements, existing conditions and future development in the vicinity. However, full implementation of these developments at this intersection will have significant impact on the traffic circulation/flow in relation to level-of-service ratings because of the limited access between McCabe Road and State Highway 146 now and in the future. A right turn lane must be constructed to ensure that traffic congestion does not occur as a result of this development. Drainage - Hydrologic/Hydraulic Impact Analysis by Dodson & Associates, Inc. (June, 2009) determine mitigation measures required to account for impacts resulting from the development of entire 107 -acre tract. Proposed drainage plan will consist of an on-site mitigation/storm water quality (SWQ) basin in order to attenuate the peak runoff conveyed by the proposed internal storm sewer system. The General Plan shows that all storm drainage sheet flows directly on to the undevelopable portion of the development. Concentrated sheetflow within the streets will be conveyed to the southern portion of the development where it will be discharged into the wetlands preserve area. Runoff collected within the on-site mitigation pond will be drained via 24-inch RCP and outfall into Taylor Bayou. An excess runoff entering the wetland preserve area will be ponded in an existing low lying area within the wetland preserve and slowly discharge into the TxDOT drainage system serving State Highway 146. The increased runoff will be stored within this natural depression by providing a berm around the area in order to contain the excess runoff and to attenuate and decrease runoff rates. An existing earthen berm has been constructed along the southern portion of the project site. This berm is located within the city limits of the City of Shoreacres and extends from the southwest comer of the project site to east for about 900 feet. The berm prohibits ponded water within the wetlands from sheet-flowing to the south. However, the study recommends to extend the earthen berm about 700 feet to the north where it meets an outfall swale from the ponding area and then about 200 feet north of this swale. As per land plan for the developed area, approximately 11.2 acre-feet of storage volume will be provided within the proposed mitigation pond. A 24-inch RCP will drain the basin approximately 700 feet to the east and outfall into Taylor Bayou. A constant tailwater equaling the top of pipe is used to create a discharge versus headwater relationship, using these parameter, it will have no adverse impact on the drainage system of the adjoining Shady River Subdivision.