17.140.050 General requirements.
(1) The 2005 Edition of the Washington State Department of Ecology’s “Stormwater Management Manual for Western Washington” is hereby adopted by reference and is hereinafter referred to as the “manual.” Local exceptions are included in Chapter 3 of the Street and Utility Standards (Chapter 14.14 SMC) and are included herein by this reference.
(2) Design for stormwater systems shall be consistent with the street and utility standards (Chapter 14.14 SMC).
(3) Stormwater Best Management Practices (BMPs).
(a) General. BMPs shall be used to control pollution from stormwater. BMPs shall be used to comply with these standards. BMPs may be found in the manual.
(b) Experimental BMPs. In those instances where appropriate BMPs are not in the manual, experimental BMPs should be considered. Experimental BMPs are encouraged as a means of solving problems in a manner not addressed by the manual in an effort to improve stormwater quality technology. Experimental BMPs must be approved in accordance with the approval process outlined in the manual.
(4) Illicit Discharges. Illicit discharges to stormwater drainage systems are prohibited.
(5) Design Requirements for Stormwater Facilities.
(a) Low impact development (LID) techniques for stormwater are encouraged.
(b) New stormwater ponds shall be designed with an irregular shape that utilizes the natural contours of the site and limits the use of manmade concrete walls to no more than 50 percent of the length of the perimeter pond embankment, measured at the pond bottom.
(c) Ponds that are bounded by fences shall utilize chain link fencing coated in black vinyl to reduce the aesthetic impact of the fencing.
(d) Stormwater ponds shall incorporate landscaping that provides visual screening of the pond for a minimum of 40 percent of the pond perimeter using either shrubs and evergreen trees or living fences. Spaces between planting clusters shall utilize ground cover. Trees and shrubs shall be grouped to provide a minimum of six feet for consideration of mowing equipment. Deciduous trees and shrubs shall not be provided within or around the pond area. Irrigation will be required from a homeowners’ association if non-drought-tolerant species are used in the planting design.
(i) Plants considered acceptable for living fences include barberries (Berberis darwinii and B. veruculosa), camelia (Camelia sasanqua), quince (Chenomeles), cotoneaster (Cotoneaster horizontalis, C. simonsii), forsythia (Forsythia suspensa sieboldii), winter jasmine (Jasminum nudiflorum), euonymous (Euonymous fortunei), bittersweet (Celastrus orbiculatus), and Russian vine (Polygonum).
(ii) Plants considered acceptable for shrubs include English laurel, photinia, yew, arbor-vitae, hemlock, western red cedar, hornbeam (Carpinus), hawthorn (Crataegus), cypress (Cupressocyparis) and beech (Fagus).
(e) Functional integration (such as fountains, basketball courts, tennis courts, open play areas, etc.) is strongly encouraged with stormwater facilities. (Ord. 1356 §§ 25, 26, 2013; Ord. 1207 § 1, 2007; Ord. 1110 § 3, 2002; Ord. 929 Ch. 10(J)(5), 1995).