Design Standards—Landscaping and Irrigation | Development Standards
0.4 to 0.6 for average water use plants
ii. Using proper irrigation equipment and schedules, including features such as repeat cycles, to closely match application rates with infiltration rates; and iii. Considering special problems posed by irrigation on slopes and in median strips. b. All irrigation water outlets, except those using alternative water sources, shall be downstream of the meter used to measure irrigation water use. c. Irrigation systems shall be subject to the following additional provisions:
0.7 to 1.0 for high water use plants
c. For each hydrozone, plant factor values may be determined and adjusted by the designer (based on professional judgment and applicable reference materials) considering the relevant factors such as: i. Water requirements of the various plant species proposed;
ii. Density of the plantings;
iii. Microclimate of the site; and
i. Systems shall not be located on any:
iv. Soil conditions.
a) Turfgrass slopes exceeding a slope of three horizontal feet to one vertical foot (3:1); and b) Turfgrass portions of median strips less than eight feet width. ii. Systems in landscape strips less than five feet in width shall be designed to ensure that overspray and/or runoff does not occur by use of system design options such as low volume emitters or microspray systems. iii. Systems shall be designed to be consistent with the requirements of the hydrozone in which they are located. iv. Systems shall be designed with the minimum average irrigation efficiency of 0.625 for spray type and 0.925 for low volume, low pressure emitter type systems.
4. Water use – Irrigation efficiency goals and system design standards For purposes of this section, irrigation shall include any means of applying water to landscaped areas. All irrigation is at the applicant’s option. Manually applied irrigation methods shall comply with subsections 1. and 2. of this section. Irrigation applied through installed irrigation systems shall comply with subsections 1. through 3. of this section: a. Irrigation water shall be applied with goals of avoiding runoff, low head drainage, overspray, or other similar conditions where water flows onto adjacent property, nonirrigated areas, and impervious surfaces by:
i. Considering soil type and infiltration rates;
Effective | January 1, 2022
Title 21: Sammamish Development Code | 321
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