07-09-18 Drainage and Flooding Committee Meeting

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IML TABLE 1 - RAINFALL INTENSITY COEFFICIENTS 70 7.7 0.749 81 7.7 0.724 91 7.9 0.706 The Kerby-Kirpich Method was used in adherence with the TxDOT Hydraulic Design Manual Chapter 4 Section 11 to calculate the Time of Concentration for each basin. The peak flow values were used to determine the storage coefficient for each individual drainage area on site. City of La Porte Design Criteria The City of La Porte Public Improvement Criteria Manual (PICM) Chapter 5, Storm Water Design Criteria, was reviewed and adhered to wherever there was no overlap with the TxDOT Hydraulic Design Manual. Where standards or methods were listed in both documents, the TxDOT regulations were used. 2.5. REGULATORY COORDINATION TxDOT (Highways) Coordination Internal TXDOT coordination will be necessary for any alteration to infrastructure entering the storm sewer in Spencer Highway, as that is a TxDOT controlled highway. City of La Porte Coordination It was discussed at the kick off meeting with the City of La Porte Public Works Director that the design storm event for the drainage evaluation to be considered at the capacity of the receiving system (the storm sewer in Spencer Highway). The storm sewer system along Spencer Highway has a capacity for 10-year storm event. As a result, the 10-year storm was used as the design storm. Federal Emergency Management Agency (FEMA) Coordination Any alteration to FEMA effective floodplain will require coordination with FEMA. The proposed improvements will not result in any changes in the existing floodplain, and FEMA coordination is not expected. United States Department of the Army Section 404 Permit Requirements We do not anticipate a need to consider the Section 404 Permit, as no dredged or fill material will be discharged into any waters of the United States. The National Wetlands Inventory through the U.S. Fish and Wildlife Service was reviewed as well, and there are no wetlands on the La Porte Municipal Airport site. Page 17