Design Standards—Landscaping and Irrigation | Development Standards
Financial guarantees
I.
LA: Landscape area (square feet)
Financial guarantees shall be required consistent with the provisions of SMC Title 27A. This time period may be extended to one year by the director, if necessary to cover a planting and growing season.
CF: Conversion factor value of 0.62 (Eto inches to gallons per square foot) REFERENCE TO TABLE - HISTORICAL DATA* Month Monthly Net Irrigation Requirements (in. January .00 February .00 March .00 April .00 May 1.59 June 3.13 July 4.46 August 3.51 September 1.77 October .03 November .00 December .00 Season total 14.49
J. Water use and irrigation
1. Water use – Applicability of water budget for landscape areas Irrigation systems of any type are optional components of a landscape area. However, a water budget for irrigation purposes shall be established for all new development, except for: a. Individually platted single dwelling (attached or detached) residential lots; provided, that developer- installed landscaping in common areas of residential projects is not exempt; and b. Any project with a total landscaped area less than 500 square feet.
*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. b. The City shall periodically undertake an evaluation of the WB calculation formula outlined in subsection 2. 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
2. Water use – Irrigation water budget calculated
a. The water budget (WB) allocation shall be calculated using the following formula:
WB = (ETo) x (AF) x (LA) x (CF)
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)
Effective | January 1, 2022
Title 21: Sammamish Development Code | 319
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