Town Center | Development Standards—Landscaping and Irrigation
purposes shall be established for all new development, except for: 1. Individually platted single dwelling (attached or detached) residential lots; provided, that developer-installed landscaping in common areas of residential projects is not exempt; and 2. Any project with a total landscaped area less than 500 square feet.
ETO REFERENCE TABLE
Month
Net Irrigation Req. (Inches)
January February
.00 .00 .00 .00
March
April May June
1.59 3.13 4.46 3.51 1.77 .03 .00
July
August
M. Water use – Irrigation water budget calculated
September
1. The water budget (WB) allocation shall be calculated using the following formula:
October
November December
.00
WB = (ETO) x (AF) x (LA) x (CF)
Season Total
14.49
ETO: Referenced evapotranspiration rate (net seasonal irrigation requirement in inches; see table below) AF: Adjustment factor value of 0.8 (i.e., 0.5 x (ETO)/0.625 irrigation efficiency coefficient)
*These figures are based on a 30-year average of National Weather Service Data and represent the amount of additional irrigation required for turf grass. The figures are adjusted for turf typically used in commercial landscaping. 2. The City shall periodically undertake an evaluation of the WB calculation formula outlined in subsection 1. of this section. The evaluation shall include a recommendation to retain or modify the adjustment factor or components thereof, and shall be made in consultation with groups including landscape professionals and water purveyors. 3. The water budget will be calculated upon the total area of the site in landscape areas and in landscape water features (such as decorative ponds, pools or fountains) that are fed by irrigation water. For the purpose of calculating the water budget, “landscape area” shall mean the entire parcel, less:
LA: Landscape area (square feet)
CF: Conversion factor value of 0.62 (ETO inches to gallons per square foot)
518 | Title 21: Sammamish Development Code
Effective | January 1, 2022
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