City of Frisco Engineering Standards

Engineering Standards
2. Off-site Flows for Undeveloped Upstream Watershed
If an undeveloped upstream property exists, the Engineer shall assume fully developed
conditions without detention for the off-site area unless a Downstream Assessment shows the
downstream facilities cannot convey the fully developed peak flows.
4.03 Downstream Assessment
The design of a storm drain facility must account for the offsite flows that are routed through the
development, flows generated by the development, and the impacts of the development and the
drainage system on downstream facilities. The storm water discharge from the development shall
not cause adverse impacts to adjacent or downstream properties or facilities. In order to determine
the impacts to the downstream properties or facilities, a Downstream Assessment may be
required. The following summarizes the process for a Downstream Assessment.
Section 4 – Drainage Design Requirements May 2012 Page 4-7