Development Standards | Design Standards—Landscaping and Irrigation
i. Bioretention shall be evaluated in accordance with the Surface Water Design Manual to the maximum extent feasible. Vegetated areas within parking area landscaping that function as bioretention for the treatment of storm water runoff shall consist of the following: a) Trees, shrubs, perennials and groundcovers tolerant of summer drought, ponding fluctuations and saturated soil conditions for prolonged lengths of time anticipated by the facility design and hydrologic conditions. b) Plants should be tolerant of typical pollutants from surrounding surfaces, such as petroleum hydrocarbons, dissolved metals, and fertilizers. c) Plantings should consist of native plant types; at least 15 percent of the plant palette shall be evergreen. Planting and grading for drainage features should be designed to be integrated aesthetically with the surrounding landscape and urban design elements. d) Visual buffering, sight distances and setbacks should be considered for landscaping adjacent to roadways. e) The planting and bioretention soil media shall consist of a bioretention soil mix in accordance with the January 2009 WSU Pierce County Extension “Bioretention Soil Mix Review and Recommendations for Western Washington,” or equivalent.
f) No plants that are included on the King County noxious weed list. ii. Other parking area landscaping not devoted to storm water management shall consist of the following: a) Canopy-type deciduous trees, evergreen trees, evergreen shrubs and groundcovers planted in islands or strips; b) Shrubs that do not exceed a maintained height of 42 inches; c) Groundcover pursuant to SDC 21.06.020C.7.; and
d) At least 50 percent of trees are coniferous.
iii. Plantings contained in planting islands or strips shall have an area of at least 100 square feet and with a narrow dimension of no less than five feet.
6. Landscaping – General standards for all landscape areas
All new landscape areas proposed for a development shall be subject to the following provisions: a. Berms shall not exceed a slope of two horizontal feet to one vertical foot (2:1). b. All new turf areas, except all-weather, sand-based athletic fields, shall: i. Be augmented with a two-inch layer of stabilized compost material or a four-inch layer of organic
308 | Title 21: Sammamish Development Code
Effective | January 1, 2022
Made with FlippingBook Ebook Creator