Volume 2-05, Chapter 3 - City of Wichita

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Section 3.2.1 - Stomwater Pond • Earth Dams • The dam construction plans shall indicate allowable soil materials to be used, compaction required, locations of core trenches if used, any sub-drainage facilities to be installed to control seepage, plus horizontal and vertical dimensions of the earthen structure. • The sub-grade of the dam shall be scarified prior to the placement and compaction of the first lift of soil backfill to ensure a good bond between the existing soil and the earthen dam. • Placement of earth fill shall be in controlled lifts with proper compaction. • Placement of spillway or outflow pipes through the dam shall be per the plan details, with proper backfill and compaction of any excavated trenches. Hydraulic flooding or other compaction methods of saturated soil shall not be allowed. • Topsoil and soil additives necessary for the establishment of permanent ground cover above the normal water surface elevation and on the downstream side of the dam shall be installed and seeded as soon as practical to avoid rilling and erosion of the dam’s earthen embankment. • Do not plant trees or shrubs on the earth dam. Their root systems cause seepage and damage to the structure. • Concrete Dams • Concrete dams shall be designed and built in accordance with the American Concrete Institute’s (ACI) latest guidelines for Environmental Engineering Concrete Structures. Particular attention shall be paid to water tightness, crack control, concrete materials and construction practices. • The construction plans shall indicate materials, plus horizontal and vertical dimensions necessary for the construction of the dam. Details and information shall be provided on joint types and spacing to be used. • At least half of the water surface perimeter of the pond at normal pool elevation shall be constructed with a vegetated earthen embankment or graded slope. • Principal and emergency spillways can be incorporated into a weir overflow over the weir if splash pads or another type of control structure is provided to protect the downstream toe of the concrete structure. • Placement of drain valves, overflow controls and other penetrations of the concrete wall shall not be located on the same vertical line to prevent creating a weakened plane where uncontrolled cracks can form. Locations should also anticipate operation during storm events when overflow weirs will be operating. Page 3 - 38 Volume 2, Technical Guidance
Section 3.2.1 - Stormwater Pond 3.2.1.6 Design Procedures for Stormwater Ponds Step 1 Step 2 Step 3 Step 4 Compute runoff control volumes using the Integrated Design Approach: Calculate the WQv, CPv or channel protection inflow hydrograph, and the peak flow control inflow hydrographs using methods discussed in Volume 2, Chapter 4. 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. Determine pretreatment volume: A sediment forebay is provided at each inlet, unless the inlet provides less than 10% of the total design storm inflow to the pond. The forebay should be sized to contain 0.1 inches per impervious acre of contributing drainage and should be 4 to 6 feet deep. The forebay storage volume counts toward the total WQ v requirement and may be subtracted from the WQ v for subsequent calculations. Determine permanent pool volume and water quality extended detention volume: Wet Pond: Size permanent pool volume to 1.0 WQ v Extended Detention Wet Pond: Size permanent pool volume to 0.5 WQ v . Size extended detention volume to 0.5 WQ v . Extended Detention Micropool Pond: Size permanent pool volume to 0.1 acre-inch per impervious acre. Size extended detention volume to remainder of WQ v . Step 5 Step 6 Layout pond grading and determine storage available for permanent pool and extended detention water quality pool, as applicable: This step involves designing the grading for the pond (establishing contours) and determining the elevation-storage relationship for the pond. This typically requires a trial and revision approach as the design is refined. Include safety and aquatic benches. Set WQ V permanent pool elevation based on calculated permanent pool volume and the elevation-storage curve for the pond (see above). Determine elevation and orifice size for extended detention portion of WQ V (for extended wet detention ponds and micropool ponds): Set orifice elevation at top of permanent pool. Set top of extended detention pool based on extended detention volume and pond elevation-storage curve. By trial and revision, select an orifice size that will drain 90% of the WQ V in 24 hours. The 90% criteria is intended to address the tendency of the drawdown method (see Chapter 4 of Volume 2) to oversize the orifice. Volume 2, Technical Guidance Page 3 - 39
Page 1 and 2: CHAPTER 3 STORMWATER CONTROLS TABLE
Page 3 and 4: Chapter 3 - Table of Contents 3.2.8
Page 5 and 6: Chapter 3 - Table of Contents LIST
Page 7 and 8: Section 3.1 - Stormwater Management
Page 31 and 32: Section 3.2.1 - Stormwater Pond 3.2
Page 33 and 34: Section 3.2.1 - Stormwater Pond Fig
Page 35 and 36: Section 3.2.1 - Stormwater Pond For
Page 37 and 38: Section 3.2.1 - Stormwater Pond •
Page 39 and 40: Section 3.2.1 - Stormwater Pond 1'
Page 41 and 42: Section 3.2.1 - Stormwater Pond •
Page 43: Section 3.2.1 - Stormwater Pond •
Page 47 and 48: Section 3.2.1 - Stormwater Pond Ste
Page 53 and 54: Section 3.2.2 - Extended Dry Detent
Page 59 and 60: Section 3.2.3 - Vegetative Filter S
Page 67 and 68: Section 3.2.4 - Grassed Channel 3.2
Page 73 and 74: Section 3.2.4 - Grassed Channel max
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
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Section 3.2.6 - Infiltration Trench
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Section 3.2.6 - Infiltration Trench
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Section 3.2.7 - Soakage Trench 3.2.
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Section 3.2.7 - Soakage Trench •
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Section 3.2.8 - Surface Sand Filter
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Section 3.2.9 - Bioretention Areas
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Section 3.2.10 - Stormwater Wetland
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Section 3.3 - Secondary TSS Treatme
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Section 3.3.1 - Proprietary Treatme
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Section 3.3.1 - Proprietary Treatme
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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 com
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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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