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Option 3. Detention Design Worksheet <br />Table 3: Small Project Detention Sizing <br />Sizing <br />Selected <br />Total Contributing Area to <br />Detention System, (sf) <br />At least but less than* <br />Acres <br />(max) <br />Orifice Size <br />(in) <br />Riser Height, overflow <br />elevation above invert <br />of outlet pipe, (ft) <br />Riser <br />Diameter <br />(in) <br />Detention <br />Pipe Diameter <br />(in) <br />Detention Pipe <br />Length Required <br />(ft) <br />200 <br />400 <br />0.0092 <br />0.375 <br />1.5 <br />6 <br />18 <br />20 <br />400 <br />600 <br />0.0138 <br />0.375 <br />1.5 <br />8 <br />18 <br />24 <br />600 <br />800 <br />0.0184 <br />0.375 <br />1.5 <br />8 <br />18 <br />28 <br />800 <br />1000 <br />0.0230 <br />0.5 <br />1.5 <br />8 <br />18 <br />33 <br />1000 <br />1200 <br />0.0275 <br />0.5 <br />1.5 <br />8 <br />18 <br />40 <br />1200 <br />1400 <br />0.0321 <br />0.5 <br />1.5 <br />8 <br />18 <br />55 <br />1400 <br />1600 <br />0.0367 <br />0.5 <br />1.5 <br />8 <br />18 <br />70 <br />1600 <br />1800 <br />0.0413 <br />0.5 <br />2.0 <br />8 <br />24 <br />60 <br />1800 <br />2000 <br />0.0459 <br />0.5 <br />2.0 <br />8 <br />24 <br />65 <br />*For projects directing more than this total area draining to the detention facility, size using a continuous runoff model (WWHM, <br />MGS Flood etc.). Do not use this table to size facility. <br />Outlet pipe shall be set 3" above bottom of detention pipe to allow for sediment storage. <br />• Net new impervious area requiring mitigation (ft): <br />• Contributing impervious area to BMP: <br />• Total contributing area including landscaped area (ft2): <br />All underground stormwater facilities shall be setback from any structure or property line a distance equal to the depth of the <br />ground disturbed in setting the structure. <br />Applicable access requirements of DCSS 4-4.2 (3) have been met. <br />