Common use of Preparation of Drainage Impact and Mitigation Analysis Report for submission and approval of Fort Bend County Drainage District Clause in Contracts

Preparation of Drainage Impact and Mitigation Analysis Report for submission and approval of Fort Bend County Drainage District. Determine existing and proposed condition discharge rates from the proposed roadway alignment limits. Confirm limits of the analysis with Preliminary layout for the proposed roadway. Discharge rates for proposed conditions will reflect the change in Tc and change of the drainage system from open ditch to storm sewers. Additionally, all new areas of Proposed Right-of-Way (ROW) will be accounted for in the drainage calculations. • Develop hydrographs for existing and proposed conditions for design storms and determine required detention volume requirements to offset the increase in peak runoff rates for storm s up to the 100-year events. Storms to be evaluated for the analysis will include the 2-year and 100- year events using Atlas 14 rainfall data. • Perform drainage area delineations for the proposed conditions and develop onsite flow calculations for proposed conditions. Perform extreme event sheet flow analysis. • Identify all mitigation requirements, including measures needed to eliminate impacts on flow rates and floodplain storage. Such measures may include proposed detention pond, floodplain excavation, etc. • Provide options for detention pond(s) size and location. • Update calculations and hydrologic modeling data to reflect required mitigation measures and features.

Preparation of Drainage Impact and Mitigation Analysis Report for submission and approval of Fort Bend County Drainage District. Determine existing and proposed condition discharge rates from the proposed roadway alignment and limits. Confirm limits of the analysis with Preliminary preliminary layout for the proposed roadway. Discharge rates for proposed conditions will reflect the change in Tc and change of the drainage system from open ditch to storm sewers. Additionally, all new areas of Proposed Right-of-Way (ROW) will be accounted for in the drainage calculations. • Develop hydrographs for existing and proposed conditions for design storms and determine required detention volume requirements to offset the increase in peak runoff rates for storm s storms up to the 100-year events. Storms to be evaluated for the analysis will include the 2-year and 100- 100-year events using Atlas 14 rainfall data. • Perform drainage area delineations for the proposed conditions and develop onsite and offsite flow calculations for proposed conditions. Perform extreme event sheet flow analysis. • Identify all mitigation requirements, including measures needed to eliminate impacts on flow rates and floodplain storage. Such measures may include proposed detention pond, floodplain excavation, etc. • Provide options for detention pond(s) size and location. • Update calculations and hydrologic modeling data to reflect required mitigation measures and features.