Development Standards—Landscaping and Irrigation | Town Center
N. Water use – Estimated water use calculated
a. Sensitive areas and their buffers;
b. The building footprint;
The estimated water use shall be calculated using the following provisions. 1. Estimated water use (EWU) shall be calculated for each hydro zone by using the following formula:
c. Driveways;
d. Paved portions of parking lots; and
e. Hardscapes (e.g., decks, patios, sidewalks, and other nonporous areas).
EWU=[(ETO) x (PF) x (HA) x (CF)]/IE
ETO: Referenced evapotranspiration rate (net seasonal irrigation requirement in inches. See table in SDC 21.07.070M.
4. Areas such as playgrounds, sport fields, golf courses, school yards, or other recreational spaces where the turf provides a playing surface or serves other recreational purposes may be allowed additional water beyond the calculated water budget. In order to receive additional water for such turf areas, the applicant shall submit a statement designating such turf areas for recreational purposes and specifying additional water needs above the water budget. This additional water need will be based upon the ETO information for the turf grass species or species mix used in such turf areas. 5. Landscape water features shall not use potable water unless the water feature recirculates water used in its operation. 6. The irrigation water use may be monitored by the water purveyor after the date of release of the performance bond. 7. Alternative water sources such as recycled wastewater or rainwater are encouraged as permitted by the Department of Ecology. Such water sources shall not be subject to the limits of the water budget.
PF: Plant factor value (see subsection 2. of this section)
HA: Hydro zone area (square feet)
CF: Conversion factor value of 0.62 (ETO inches to gallons per square foot)
IE: Irrigation efficiency value
2. Plant factor values shall be as follows, but may be adjusted pursuant to subsection 3. of this section:
0 to 0.3 for low water use plants
0.4 to 0.6 for average water use plants
0.7 to 1.0 for high water use plants
3. For each hydro zone, 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:
Effective | January 1, 2022
Title 21: Sammamish Development Code | 519
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