Laserfiche WebLink
I In <br />40 <br />®► <br />Contract #SD624AA <br />3-13 Technical Analysis -Existing System — The information provided in Task 2 by the <br />- Consultant and the model developed by ECT will be utilized by DISTRICT in the <br />modeling of the IRFWCD drainage system. Existing conditions and future conditions <br />j (Year 2020) shall be modeled by DISTRICT. The models shall simulate actual existing <br />storage and runoff conditions using the SWMM model. <br />Calibration and verification of the runoff model shall be completed by comparing the <br />flows generated by the model with recorded data from historic storm events, results of <br />previous studies of the basin, results from studies or data from similar watershed in the <br />area, and recorded hydrologic data from the gauging program in progress in Indian River <br />County. <br />Flow rates and water -surface profiles for existing and one future land use scenario shall <br />be obtained using the SWMM model. The future scenario shall include the year 2020 <br />Future Land use map from the comprehensive plan. The modeling will include the <br />following storm events: <br />• 2 -Year, 24 Hour <br />• 5 -Year, 24 Hour <br />• 10 -Year, 24 Hour <br />• 25 -Year, 24 Hour and <br />• 100 -Year, 24 Hour <br />Development of runoff hydrographs for future land use conditions shall estimate <br />attenuation of peak rates of runoff for new development required in accordance with <br />current regulations. <br />The water quality portion of the SWMM model shall include average annual pollutant <br />loadings to the IRL, pollutant loading rates for specific land uses, and pollutant removal <br />efficiencies for typical stormwater treatment systems. <br />DISTRICT modeling shall include a pollutant -loading model for at least the following <br />parameters: <br />• Total nitrogen <br />• Total phosphorus <br />j • Orthophosphorus <br />• Suspended solids <br />• TSS <br />I <br />The model prepared by DISTRICT shall be updated as necessary to calculate average <br />annual pollutant loadings for future land use in the basin. Calculations by DISTRICT <br />shall take into account pollutant removal efficiencies of stormwater treatment facilities <br />for major developments permitted after 1980, which is the effective date of stormwater <br />treatment facilities requirements. Calculated results shall be compared with similar prior <br />studies and existing water quality data for consistency. <br />Page 14 of 19 <br />