Roadway Standards Section 450 - Detention And Downstream Impacts

1. Bridges and other major conveyances identified as deficient in a downstream analysis shall be designed to accommodate the 100 year storm.
2. The outfall of detention facilities may be required to accommodate the 100 year storm depending on the downstream impacts.
3. Detention structures shall not be constructed in the public right-of-way without prior approval from Engineering.
4. Conveyance facilities shall be designed to carry a 25 year storm event with the basin built with 85% impervious.
5. Infiltration testing is required for all detention ponds and other surface water management facilities proposed that utilize infiltration. In rural areas, the simplified method for infiltration testing may be used if coordinated with County staff.