§ 24.30.312. Wetlands—Stormwater facilities—Engineered stormwater dispersion.

The dispersion area of stormwater dispersion systems, as defined by the Thurston County DDECM, shall not be considered a stormwater facility as described in TCC 24.30.300—24.30.310, and regulated as such, unless a physical structure is incorporated within the design that impacts the standard wetland buffers. Stormwater dispersion facilities whose dispersion area includes any portion of a wetland buffer are allowed as an element of a stormwater system under the following circumstances:

A.

Dispersion of runoff from back yards of development and downspout dispersion, done in accordance with the Thurston County DDECM, is allowed at the outside edge of the wetland buffer.

B.

Sheet flow and concentrated flow dispersion, done in accordance with the Thurston County DDECM, of stormwater meeting runoff treatment requirements of the Thurston County DDECM is allowed at the outside edge of the wetland buffer.

C.

The required dispersion area, calculated under the DDECM, for sheet flow and concentrated flow dispersion from pervious and impervious surfaces, done in accordance with the Thurston County DDECM, may only include that portion of a wetland buffer outside of the minimum area considered necessary for water quality as shown in Table 24.30-1.

D.

Native vegetation in the wetland and buffer may be increased but shall not be cleared or altered to accommodate stormwater treatment.

E.

In no case shall dispersion methods be approved that may cause water quality impacts to the wetland. If water quality impacts are anticipated or observed, additional stormwater treatment methods shall be implemented.

(Ord. No. 14773, § 3(Att. B), 7-24-2012)