Volume 2-05, Chapter 3 - City of Wichita

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Section 3.1 - Stormwater Management Controls Overview Site Feature 100 Year Floodplain Local Stormwater review Authority Utilities Local Review Authority Roads Structures Water Wells Location and Permitting Guidance Grading and fill for structural control construction is generally discouraged within the 100 year floodplain, as delineated by FEMA flood insurance rate maps, FEMA flood boundary and floodway maps, or more stringent local floodplain maps. Floodplain fill cannot raise the floodplain water surface elevation by more than limits set by the appropriate jurisdiction. Call appropriate agency to locate existing utilities prior to design. Note the location of proposed utilities to serve development. Structural controls are discouraged within utility easements or rights of way for public or private utilities. Consult KDOT for setback requirements from State maintained roads. Consult Wichita or Sedgwick County authority for setback requirements for City or County streets and roads. Consult Wichita or Sedgwick County authority for required structural control setbacks from structures. Consult Wichita or Sedgwick County authority for required minimum setbacks for stormwater infiltration and other structural controls. 3.1.3.2 Example Application A 15-acre institutional area (e.g., church and associated buildings) is being constructed in a dense urban area. The impervious coverage of the site is 40%. The site drains to an urban stream that is highly impacted from hydrologic alterations (accelerated channel erosion). The stream channel is deeply incised and hydraulically disconnected from the original floodplain; consequently, flooding is not an issue. The channel drains to a larger sediment-laden stream. Low permeability soils limit infiltration practices. Objective: Avoid additional accelerated erosion to receiving channel and reduce TSS loads to the sediment-laden stream. Target Removal: Provide stormwater management to mitigate for accelerated channel incision and reduce TSS loadings by 80%. Activity/Runoff Characteristics: The proposed site is to have large areas of impervious surface in the form of parking and structures. However, there will be a large contiguous portion of turf grass proposed for the front of the parcel that will have a relatively steep slope (approximately 10%) and will drain to the storm drain system associated with the entrance drive. Stormwater runoff from the site is expected to exhibit fairly high sediment. Table 3-4 lists the results of the selection analysis using the screening matrix described previously. The highlighted rows indicate the controls selected for this example. The X’s Page 3 - 12 Volume 2, Technical Guidance
Section 3.1 - Stormwater Management Controls Overview indicate inadequacies in the control for this site. The ’s indicate adequate control capabilities for this site. The process involves moving left to right across the matrix for each control. Note that after a control is excluded, no further evaluation is performed for that control. While there is a downstream sediment-laden stream to consider, there are no special watershed factors or physiographic factors to preclude the use of any of the practices from the structural control list. Due to the size of the drainage area, most stormwater ponds and wetlands (permanent pools) are removed from consideration. However, an extended detention micropool would be acceptable. In addition, the site’s impermeable soils remove infiltration controls from being considered. Other controls are ruled out on the basis of aesthetics, cost and other subjective factors. The micropool can probably be used to achieve channel protection and flood control. If not, a dry extended detention pond (with forebay) may be used. Table 3-4 Sample Structural Control Selection Matrix Structural Control Alternative TSS Removal Suitability Site Applicability Implementation Considerations Physiographic Factors/Soils Special Considerations Other Issues OK Stormwater Pond Conventional Dry Detention Pond Dry Extended Detention Pond Underground Dry Detention Basin Enhanced Dry Swale Grass Channel Infiltration Trench Soakage Trench X ED micropool X Filter Strip Surface Sand Filter Underground Sand Filter X turf too steep X turf too steep X X X turf too steep Aesthetics and High Cost 2 acres max drainage area Organic Filter High Cost Volume 2, Technical Guidance Page 3 - 13
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 17: 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 45 and 46: Section 3.2.1 - Stormwater Pond 3.2
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
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Section 3.2.4 - Grassed Channel 3.2
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Section 3.2.4 - Grassed Channel 3.2
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Section 3.2.4 - Grassed Channel max
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Section 3.2.5 - Enhanced Swale 3.2.
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Section 3.2.5 - Enhanced Swale Chan
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Section 3.2.5 - Enhanced Swale B. G
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Section 3.2.5 - Enhanced Swale High
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Section 3.2.5 - Enhanced Swale Side
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Section 3.2.5 - Enhanced Swale 3.2.
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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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