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Part 3 Stormwater Management Plan <br />residence time is a duration equal to that which would be provided by a 200 ft long <br />swale,flow depth of 4 inches, and maximum velocity of 1.5 feet-per-second,or about <br />two and one-half minutes. <br />Biofiltration swales on the Suncadia project will not be irrigated and,therefore,must be <br />seeded with drought resistant vegetation suitable for the upper Kittitas County climate. <br />The typical seed mixture used for the Suncadia biofiltration swales is as follows: <br />Seed Mixture Type Percentage <br />Sherman Big Blue Grass 10 <br />Joseph Idaho Fescue 30 <br />Sodar Streambank Bunch Grass 30 <br />Secar Blue Bunch Wheat Grass 30 <br />(Source:Wildland,Inc.,Richland,WA,October 2000.) <br />This mixture may be changed to accommodate site conditions or recommendations <br />from design professionals. <br />Overflow Routes <br />Each existing stormwater facility in Phase 3 has a controlledoverflow structure.The overflow <br />discharges to an overflow drainage swale or enclosed pipe where it is conveyed to a <br />downstream facility or controlled dispersion area.In the case of infiltration ponds,overflow <br />routes are provided to the next downstream infiltration facility where feasible.This provides <br />for the infiltration of stormwater even if one facility is partially clogged or out of operation. <br />February 2019 Phase 3 Divisions 15 &16 Engineering Summary <br />ESM Consulting Engineers,L.L.C.3 -3 <br />\\Esm8\engr\ESM-JOBS\998\718\016\document\P3Dl5&l6 Eng Summ_Part 3.doc <br />Index #11