Watershed Management Plan - Mason County

Appendix
C Key Issues and Options – Water Quality
for maintenance of roadside ditches, including regular inspections and
cleaning, planting of vegetation, and examination of culverts for evidence of
scour. The manual also recommends – but does not require – that
jurisdictions install bioswales and filter strips to treat runoff from roads,
and to use engineered topsoils when needed to establish and maintain
roadside vegetation. Bioswales are ditches ranging from two to ten feet in
width that use plants and topsoil to filter pollutants from stormwater. A
filter strip is a flat area that performs the same functions as a bioswale.
Filter strips consist of a narrow band of gravel that borders a roadway and a
wider swath of vegetation adjacent to the gravel (Washington Department
of Ecology, 2001).
The Planning Unit could request that the Washington Department of
Transportation implement these recommended best management practices
for treating stormwater runoff from highways, particularly when highway
repairs are conducted.
Option 51.
Adopt the most current Stormwater Management
Manual for Western Washington or equivalent
manual
The Puget Sound Water Quality Action Team’s Puget Sound Water Quality
Management Plan (2000) calls for cities and counties to adopt a stormwater
management manual to guide their water quality efforts. Specifically, the
Management Plan encourages local governments to adopt the Department of
Ecology’s Stormwater Management Manual for Western Washington. The most
recent version of the manual was released in early 2005 (Washington
Department of Ecology, 2005b).
Should a local government opt not to adopt Ecology’s manual, the
Management Plan recommends adopting an “equivalent” manual (Puget
Sound Water Quality Action Team, 2000). Jurisdictions must submit their
chosen manuals to Ecology for review and approval. Other manuals
developed in Washington State include the 2005 King County Surface Water
Design Manual (King County Water and Land Resources Division, 2005),
and the Stormwater Manual for Eastern Washington, published in 2004
(Washington Department of Ecology, 2005c). Although King County is
more urbanized than Mason and Jefferson Counties, significant portions of
the county are still rural, with agriculture and forestry as primary land uses.
Therefore, the King County manual may be useful in WRIA 16. The
Eastern Washington manual likely is not appropriate for WRIA 16 because
of climatic differences.
The US EPA’s national best management practices for NPDES Stormwater
Phase II can be downloaded from their website 14 . However, the EPA
intends that these best management practices serve as guidance for local
14 http://cfpub.epa.gov/npdes/stormwater/menuofbmps/bmp_files.cfm
page 120 Final Plan for County Adoption – May 11, 2006