Volume 2-05, Chapter 3 - City of Wichita

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Section 3.2.1 - Stomwater Pond bacteria, and organics as stormwater runoff resides in the pond. Another mechanism for pollutant removal is uptake by algae and wetland plants in the permanent pool – particularly of nutrients. Volatilization and chemical activity also work to break down and eliminate a number of other stormwater contaminants such as hydrocarbons. Channel Protection A portion of the storage volume above the permanent pool in a stormwater pond, or above the water quality ED pool in an extended detention pond, can be used to provide control of the CP v . This is accomplished by detaining the 1-year, 24-hour storm runoff volume for 24 hours. On-Site Flood Control A stormwater pond located within the development (i.e., not at the project boundary) can provide detention storage for on-site peak flow control, if required. Downstream Flood Control A stormwater pond can be used to provide detention to control the peak flows at the project boundary and downstream of the project for the 2 through 100-year floods, in accordance with the peak flow control requirements for new developments. In all cases, the pond structure is designed to safely pass extreme storm flows (i.e., the 100-year event). 3.2.1.3 Pollutant Removal Capabilities All of the stormwater pond design variations are presumed to be able to remove 80% of the total suspended solids load in typical urban post-development runoff when designed, constructed, and maintained in accordance with the specifications discussed herein. Undersized or poorly designed ponds can drastically reduce TSS removal performance. The following design pollutant removal rates are typical percentages for design purposes derived from sampling data, modeling, and professional judgment. In a situation where a removal rate is not sufficient, additional controls may be put in place at the given site in a series or “treatment train” approach. • Total Suspended Solids – 80% • Total Phosphorus – 55% • Total Nitrogen – 30% • Heavy Metals – 50% • Fecal Coliform – 70% (if no resident waterfowl population present) Page 3 - 28 Volume 2, Technical Guidance
Section 3.2.1 - Stormwater Pond For additional information and data on pollutant removal capabilities, see the National Pollutant Removal Performance Database (2nd Edition) available at www.cwp.org and the National Stormwater Best Management Practices (BMP) Database at www.bmpdatabase.org. 3.2.1.4 Application and Site Feasibility Criteria Stormwater ponds are generally applicable to most types of development and can be used in both residential and nonresidential areas. The following criteria should be evaluated to ensure the suitability of a stormwater pond for meeting stormwater management objectives on a development site. General Feasibility • Suitable for Residential Subdivision Usage – YES • Suitable for High Density/Ultra-Urban Areas – Land requirements may preclude use • Regional Stormwater Control – YES Physical Feasibility - Physical Constraints at Project Site Drainage Area: As a guideline, a minimum of 25 acres is needed for a wet pond and an extended detention wet pond to maintain a permanent pool. Ten acres minimum is required for an extended detention micropool pond. Drainage area requirements must be checked with a water balance analysis (See Volume 2, Chapter 4) or other approved method for determining the drainage area necessary to sustain a permanent pool. A smaller drainage area may be acceptable if supported by an approved water balance analysis. Space Required: Approximately 2 to 5% of the tributary drainage area. Site Slope: Typically slopes are not more than 15% across the pond. Minimum Head: Elevation difference needed at a site from the inflow to the outflow: 6 to 8 feet. Minimum Depth to Water Table: A minimum separation distance of 5 feet is required between the bottom of the pond and the elevation of the historical high water table for unlined ponds, 2 feet for lined ponds. Soils: Underlying soils of hydrologic group “C” or “D” should be adequate to maintain a permanent pool. Most group “A” soils and some group “B” soils will require a pond liner. Evaluation of soils should be based on an actual subsurface analysis and permeability tests. Other Constraints / Considerations Local Aquatic Habitat: Consideration should be given to the thermal influence of stormwater pond outflows on downstream local aquatic habitats. Volume 2, Technical Guidance Page 3 - 29
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: Section 3.2.1 - Stormwater Pond Fig
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 49 and 50: Section 3.2.1 - Stormwater Pond Fig
Page 51 and 52: Section 3.2.1 - Stormwater Pond Fig
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
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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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