3.8 Step 8 – Delineate Threshold Discharge Areas (if applicable)

Threshold Discharge Areas (TDAs) may be applicable for rural (outside the UA and UGA) residential sites that are 5 acres or greater.

If a TDA approach is being implemented, delineate the TDAs within the site. See the definition of TDA for guidance on how to delineate a TDA. For each minimum requirement that is applicable to the project (per Step 7), use the TDA thresholds to determine which, if any, BMP(s) must be constructed within each TDA to satisfy that minimum requirement. The TDA thresholds are provided within the text of Minimum Requirements #6, #7, and #8. Minimum Requirements #1–#5 and #9 do not have separate TDA thresholds and must be applied to the entire project if they are applicable.

Implementation of a TDA approach requires downstream analysis (KCC 12.10.070). Other technical analyses may be required depending on site conditions including, but not limited to, geotechnical analysis (KCC 12.10.080) and critical drainage area evaluation (Chapter 12.28 KCC and Title 19 KCC ). The director has the authority to require additional technical analysis if warranted. See Volume II, Chapter 1 for plan and submittal requirements related to TDAs. Note that a professional engineer is required when a TDA approach is implemented (Volume II, Chapter 1).