Point Of Discharge Stability Analysis
When infiltration practices are proposed, an alternate analysis (failure analysis) must be provided which ignores infiltration (no dead storage volume available, no static or dynamic infiltration loss rates in the routing calculations, etc.) and demonstrates that no erosion will occur at the point of discharge if infiltration fails to function. Flow rates based solely upon basin inlet and outlet hydraulics must be used in comparison to Table 21-1 (below) to document a stable outlet.
A failure analysis has been provided within the Appendix of this report, which ignores infiltration and demonstrates that no erosion will occur at the point of discharge if infiltration fails to function. To summarize, when disregarding any infiltration and dead storage within the proposed basin the peak outflow for the 25 year storm is 1.06 CFS which complies with the point discharge requirements within the Standards for Soil Erosion and Sediment Control in New Jersey.
Infiltration may be used to meet peak flow reduction requirements (outlined below) for the purposes of documenting stability of the downstream receiving channel, provided that the complete loss of infiltration function does not result in an increase in peak flow values above the predevelopment levels.
Analysis below the points of discharge to the downstream receiving channel have been provided below.
Point of Discharge - Methods for Achieving Stability
There is a well-defined waterway (Dove Mill Branch Tributary) below the point of discharge; therefore, this method will be used.