Volume 2-05, Chapter 3 - City of Wichita

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Section 3.2.8 - Surface Sand Filter Soils • No restrictions. Special Downstream Watershed Considerations Aquifer Protection: Use polyliner or impermeable membrane to seal bottom of sand filter if historically high water table is within 5 feet of surface or use watertight structure. 3.2.8.6 Design Procedures Step 1 Step 2 Compute runoff control volume. Calculate the WQ v using equation 1-1. Confirm local design criteria and applicability. Consider any special site-specific design conditions/criteria. Check with local officials and other agencies to determine if there are any additional restrictions and/or surface water or watershed requirements that may apply. Step 3 Compute peak discharge for the WQ v , called Q wq , using equation 4-18. The peak rate of discharge for water quality design storm is needed for sizing of off-line diversion structures. a. Using WQ v , compute CN using equation 4-3. b. Compute time of concentration (Chapter 4, Section 4). c. Determine appropriate unit peak discharge from time of concentration (Chapter 4, Section 8). d. Compute Q wq from unit peak discharge, drainage area, and WQ v using equation 4-18. Step 4 Size flow diversion structure if needed. A flow regulator (or flow splitter diversion structure) should be supplied to divert the WQ v to the sand filter facility. Size low flow orifice, weir, or other device to pass Q wq . Step 5 Size filtration basin chamber. The filter area is sized using the following equation (based on Darcy’s Law): Equation 3-4 A f WQ = k * v * d ( h f + d f )* t f f Page 3 - 106 Volume 2, Technical Guidance
Section 3.2.8 - Surface Sand Filter where: A f = surface area of filter bed (ft2) d f = filter bed depth (ft) (typically 1.5 ft, no more than 2 ft) k = coefficient of permeability of filter media (ft/day) (use 3.5 ft/day for sand) h f = average height of water above filter bed (ft) (1/2 h temp , which varies based on site but h temp is typically ≤ 6 feet) t f = design filter bed drain time (days) (1.67 days or 40 hours is recommended maximum) Set preliminary dimensions of filtration basin chamber. Step 6 Size sedimentation chamber The sedimentation chamber should be sized to at least 25% of the computed WQ v and have a length-to-width ratio of 2:1. The Camp-Hazen equation is used to compute the required surface area: (Claytor & Schueler, 1996) o Equation 3-5 A = − * Ln( 1 − E) s Q w where: As = sedimentation basin surface area (ft 2 ) Q o = rate of outflow = the WQ v over a 24-hour period w = particle settling velocity (ft/sec) E = trap efficiency Assuming: • 90% sediment trap efficiency (0.9); • particle settling velocity (ft/sec) = 0.0033 ft/sec for imperviousness ≥ 75%; • particle settling velocity (ft/sec) = 0.0004 ft/sec for imperviousness < 75%; • average of 24 hour holding period. Then: As = (0.0081) (WQ v ) ft 2 for Imperviousness ≥ 75% As = (0.066) (WQ v ) ft 2 for Imperviousness < 75% Set preliminary dimensions of sedimentation chamber. Step 7 Step 8 Compute V min for 75% of the WQ v , as required by the design specifications. Equation 3-6 V 0.75*WQ min = v Compute storage volumes within facility and sedimentation chamber orifice size (Claytor & Schueler, 1996). V min = 0.75* WQ v = V s + V f + V f −temp Volume 2, Technical Guidance Page 3 - 107
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CHAPTER 3 STORMWATER CONTROLS TABLE
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Chapter 3 - Table of Contents 3.2.8
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Chapter 3 - Table of Contents LIST
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Section 3.1 - Stormwater Management
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Section 3.2.1 - Stormwater Pond 3.2
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Section 3.2.1 - Stormwater Pond Fig
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Section 3.2.1 - Stormwater Pond For
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Section 3.2.1 - Stormwater Pond •
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Section 3.2.1 - Stormwater Pond 1'
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Section 3.2.1 - Stormwater Pond 3.2
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Section 3.2.1 - Stormwater Pond Ste
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Section 3.2.2 - Extended Dry Detent
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Section 3.2.3 - Vegetative Filter S
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Page 67 and 68: Section 3.2.4 - Grassed Channel 3.2
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Page 75 and 76: Section 3.2.5 - Enhanced Swale 3.2.
Page 77 and 78: Section 3.2.5 - Enhanced Swale Chan
Page 79 and 80: Section 3.2.5 - Enhanced Swale B. G
Page 81 and 82: Section 3.2.5 - Enhanced Swale High
Page 83 and 84: Section 3.2.5 - Enhanced Swale Side
Page 85 and 86: Section 3.2.5 - Enhanced Swale 3.2.
Page 87 and 88: Section 3.2.6 - Infiltration Trench
Page 99 and 100: Section 3.2.7 - Soakage Trench 3.2.
Page 101 and 102: Section 3.2.7 - Soakage Trench •
Page 103 and 104: Section 3.2.8 - Surface Sand Filter
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Page 117 and 118: Section 3.2.9 - Bioretention Areas
Page 133 and 134: Section 3.2.10 - Stormwater Wetland
Page 151 and 152: Section 3.3 - Secondary TSS Treatme
Page 153 and 154: Section 3.3.1 - Proprietary Treatme
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Page 157 and 158: Section 3.3.2 - Gravity (Oil-Water)
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Section 3.3.3 - Alum Treatment 3.3.
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Section 3.3.3 - Alum Treatment •
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Section 3.3.4 - Underground Sand Fi
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Section 3.3.5 - Organic Filter 3.3.
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Section 3.3.5 - Organic Filter •
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Section 3.4 - Other Stormwater Mana
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Section 3.4.1 - Conventional Dry De
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Section 3.4.2 - Underground Dry Det
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Section 3.4.3 - Porous Pavement 3.4
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Section 3.4.3 - Porous Pavement The
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Section 3.4.3 - Porous Pavement Fig
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Section 3.4.4 - Modular Porous Pave
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Section 3.4.5 - Green Roof 3.4.5 Gr
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Section 3.4.5 - Green Roof Signific
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Section 3.4.5 - Green Roof 3.4.5.3
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Volume 2-05, Chapter 3 - City of Wichita

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