Volume 2-05, Chapter 3 - City of Wichita

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Section 3.1 - Stormwater Management Controls Overview Ability to provide Nutrient Treatment: This column indicates the capability of a structural control to remove nutrients (nitrogen and phosphorus) in runoff. Ability to provide Bacteria Removal: This column indicates the capability of a structural control to remove bacteria in runoff. Ability to accept Hotspot Runoff: The last column indicates the capability of a structural control to treat runoff from designated hotspots. Hotspots are land uses or activities which produce higher concentrations of trace metals, hydrocarbons, or other priority pollutants. Examples of hotspots might include: gas stations, convenience stores, marinas, public works storage areas, garbage transfer facilities, material storage sites, vehicle service and maintenance areas, commercial nurseries, vehicle washing/steam cleaning, industrial sites, industrial rooftops, and auto salvage or recycling facilities. A check mark indicates that the structural control may be used for a hotspot site; however, it may have specific design restrictions. Please see the specific design criteria for the structural control for more details. Please note that hotspot treatment must be tailored to the characteristics of the hotspot runoff pollutants to be removed. Designation of a control as suitable for accepting hotspot runoff does not necessarily mean it is the appropriate treatment facility for that particular hotspot condition. Such a designation simply indicates that the facility is commonly used for treatment of some types of hotspot runoff. For example, and oil-water separator is appropriate for runoff containing some types of floatable greases or oils, whereas a surface sand filter would not be suitable. Site Applicability The third category of the matrix provides an overview of the specific site conditions or criteria that must be met for a particular structural control to be suitable. In some cases, these values are recommended values or limits and can be exceeded or reduced with proper design or depending on specific circumstances. Please see the specific criteria section of the structural control for more details. Drainage Area: This column indicates the approximate minimum or maximum drainage area considered suitable for the structural control practice. If the drainage area present at a site is slightly greater than the maximum allowable drainage area for a practice, a variance would be required. Likewise, the minimum drainage areas indicated for ponds and wetlands should not be considered inflexible limits, and may be increased or decreased depending on water availability (baseflow or groundwater), the mechanisms employed to prevent outlet clogging, or design variations used to maintain a permanent pool (e.g., liners). Slope: This column identifies general slope restrictions for the specific structural control practice. Minimum Head: This column provides an estimate of the minimum site elevation difference needed from the inflow to the outflow to allow for gravity operation within the structural control. Water Table: This column indicates water table or groundwater separation requirements for certain controls. Page 3 - 8 Volume 2, Technical Guidance
Section 3.1 - Stormwater Management Controls Overview Implementation Considerations The fourth category in the matrix provides additional considerations for the applicability of each structural control option. Residential Subdivision Use: This column identifies whether or not a structural control is suitable for typical residential subdivision development (not including high-density or ultraurban areas). Ultra-Urban: This column identifies those structural controls appropriate for use in very highdensity (ultra-urban) areas, or areas where space is a premium. Relative Capital Cost: The structural controls are ranked according to their relative construction cost per impervious acre treated, as determined from cost surveys. Maintenance Burden: This column assesses the relative maintenance effort needed for a structural stormwater control, in terms of three criteria: frequency of scheduled maintenance, chronic maintenance problems (such as clogging), and reported failure rates. It should be noted that all structural controls require routine inspection and maintenance. Step 2 - Specific Criteria The last three categories in the screening matrix, shown in Appendix E, Table E-2, provide an overview of various specific design criteria and specifications, or exclusions for a structural control that may be present due to a site’s general physiographic character, soils, or location in a watershed with special water resources considerations. Physiographic Factors Three key factors to consider are low-relief, high-relief, and karst terrain. Low relief (very flat) areas are common throughout Sedgwick County. High relief (steep and hilly) areas are rare but do exist in limited lot-scale areas. Karst areas (due to dissolution of salt beds) are limited to the northwest part of Sedgwick County. Special geotechnical testing requirements may be needed in karst areas. • Low relief areas need special consideration because structural controls require a hydraulic head to move stormwater runoff through the facility. • High relief may limit the use of some structural controls that need flat or gently sloping areas to settle out sediment or to reduce velocities. In other cases, high relief may impact dam heights to the point that a structural control becomes infeasible. • Karst terrain can limit the use of some structural controls as the infiltration of polluted waters directly into underground streams found in karst areas may be prohibited. In addition, ponding areas may not reliably hold water in karst areas. Volume 2, Technical Guidance Page 3 - 9
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 13: 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
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Section 3.2.3 - Vegetative Filter S
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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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