Environment & Sustainability | Surface Water Management (Title 13)
paving of existing dirt or gravel. Permeable pavement and vegetated roofs are considered new impervious surface for purposes of determining whether the thresholds for application of minimum requirements are exceeded, as are lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains designed to collect stormwater runoff. Open, uncovered retention/detention facilities shall not be considered impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling. 53. New pervious surface. The conversion of a native vegetated surface or other native surface to a nonnative pervious surface, including, but not limited to, pasture land, grassland, cultivated land, lawn, landscaping or bare soil or any alteration of existing nonnative pervious surface that results in increased surface and stormwater runoff as defined in the Surface Water Design Manual. 54. Open space. Any parcel, property or portion thereof classified for current use taxation under Chapter 20.36 KCC and Chapter 84.34 RCW, or for which the development rights have been sold to King County under Chapter 26.04 KCC. This definition includes lands which have been classified as open space, agricultural or timber lands under criteria contained in Chapter 20.36 KCC and Chapter 84.34 RCW. 55. Parcel. The smallest separately segregated unit or plot of land having an identified owner, boundaries and surface
area which is documented for property tax purposes and given a tax lot number by the King County assessor. 56. Person. An individual and his or her agent or assign, municipality, political subdivision, government agency, partnership, corporation, business or any other entity.
Pervious surface. Any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, and native vegetation areas. Note: For purposes of threshold determination and runoff volume modeling for detention and treatment, vegetated roofs and permeable pavements are to be considered impervious surfaces along with lawns, landscaping, sports fields, artificial turf without an underdrain, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains.
57.
58. Pollution-generating impervious surface. An impervious surface considered to be a significant source of pollutants in surface and stormwater runoff. “Pollution-generating impervious surface” includes those surfaces subject to vehicular use or storage of erodible or leachable materials, wastes or chemicals and that receive direct rainfall or the run-on or blow-in of rainfall. A covered parking area would be included if runoff from uphill could regularly run through it or if rainfall could regularly blow in and wet the pavement surface. Metal roofs are also considered pollution- generating impervious surfaces unless they are treated to prevent leaching. Pollution-generating impervious surfaces include roofs that are exposed to the venting of significant amounts of dusts, mists, or fumes from manufacturing, commercial, or other indoor activities. They also include vegetated roofs exposed to pesticides, fertilizers, or loss
Revisions | June 29, 2022 Effective | January 1, 2022
138 | Title 21: Sammamish Development Code
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