Volume 2-05, Chapter 3 - City of Wichita
Volume 2-05, Chapter 3 - City of Wichita Volume 2-05, Chapter 3 - City of Wichita
Section 3.2.1 - Stomwater Pond Figure 3-11 Permanent Pool Length to Width Ratio • Minimum depth for the pond bottom shall be 3 to 4 feet, though a minimum depth of 10 feet is recommended for ponds where fish habitat is desired. Deeper areas near the outlet will yield cooler bottom water discharges that may mitigate potential downstream thermal effects. • Side slopes to the pond may not exceed 5:1 (h:v) unless a safety bench is provided, and in no case shall exceed 3:1 (see Figure 3-12). Alll side slopes should be verified with a geotechnical evaluation to ensure slope stability. • Safety benches shall have a maximumm slope of 10:1, and a minimum width of 10’. • The perimeter of all deep pool areas (3 feet or greater in depth) shall be surrounded by an aquatic bench. The aquatic bench shall extend inward from the normal pool edge 10-15 feet on average and have a maximumm depth of 18 inches below the normal pool water surface elevation (see Figure 3-12). • The pond edgee shall have turf reinforcing mesh or riprap covering the area from 2 feet above the normal pool to 2 feet below the normal pool to protect areas of the pond that will be exposed to wave action. Appendix D provides wind roses for Wichita during each month of the year to aid in locating areas that will require reinforcement. Local winds are most pronounced coming from the north and south directions. • The contours and shape of the permanent pool should be irregular to provide a natural landscape effect. Page 3 - 32 Volume 2, Technical Guidance
Section 3.2.1 - Stormwater Pond 1' MIN. FREEBOARD 100 - YEAR ELEVATION PERMANENT POOL ELEVATION 12" - 18" 10' - 15' AQUATIC BENCH 10' SAFETY BENCH IF NEEDED 5:1 MAX, OR 10:1 MAX 10:1 MAX 3:1 MAX EXISTING GRADE BASIN FLOOR 2:1 MAX EMERGENT WETLAND VEGETATION Figure 3-12 Typical Stormwater Pond Geometry Criteria D. PRETREATMENT / INLETS • Each pond shall have a sediment forebay or equivalent upstream pre-treatment at each inlet. A sediment forebay is designed to remove incoming larger sediment from the stormwater flow prior to dispersal in the larger permanent pool. Pretreatment consists of a separate cell, formed by an acceptable barrier between the forebay and pond. A forebay is to be provided at each inlet, unless the inlet provides less than 10% of the total design storm inflow to the pond. In some design configurations, the pretreatment volume may be located within the permanent pool. • A forebay must be sized to contain 0.1 acre-inch per impervious acre of contributing drainage and should be 4 to 6 feet deep. The pretreatment storage volume is part of the total WQ v requirement and may be subtracted from WQ v for permanent pool sizing. • A fixed vertical sediment depth marker shall be installed in the forebay to measure sediment deposition over time. The bottom of the forebay may be hardened (e.g., using concrete, paver blocks, etc.) to make sediment removal easier. • Pond inflow channels are to be stabilized with flared riprap aprons, or the equivalent. Inlet pipes to the pond can be partially submerged. Inflow pipe, channel velocities, and exit velocities from the forebay must be nonerosive. E. OUTLET STRUCTURES • Flow control from a stormwater pond is accomplished with the use of a principal spillway consisting of a concrete riser and barrel. The riser is a vertical pipe, typically with several weirs and/or orifices at various levels. The outlet barrel is a horizontal pipe attached to the riser that conveys flow under the embankment (see Figure 3-13). Where practicable, the riser should be located within the embankment for maintenance access, safety and aesthetics. Volume 2, Technical Guidance Page 3 - 33
- 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
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- Page 53 and 54: Section 3.2.2 - Extended Dry Detent
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- Page 57 and 58: Section 3.2.2 - Extended Dry Detent
- Page 59 and 60: Section 3.2.3 - Vegetative Filter S
- Page 61 and 62: 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.
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Section 3.2.1 - Stomwater Pond<br />
Figure 3-11 Permanent Pool Length to Width<br />
Ratio<br />
• Minimum depth<br />
for the pond bottom shall be 3 to<br />
4 feet, though a minimum depth <strong>of</strong> 10<br />
feet is recommended for ponds where fish habitat is desired. Deeper areas near the outlet<br />
will yield cooler bottom water discharges that may<br />
mitigate potential downstream thermal<br />
effects.<br />
• Side slopes to the pond may not exceed 5:1 (h:v) unless a safety bench is<br />
provided, and in<br />
no case shall exceed 3:1 (see Figure 3-12). Alll side slopes should be<br />
verified with a<br />
geotechnical evaluation to ensure slope stability.<br />
• Safety benches<br />
shall have a maximumm slope <strong>of</strong> 10:1, and a minimum width <strong>of</strong> 10’.<br />
• The<br />
perimeter <strong>of</strong> all deep pool areas (3<br />
feet or greater in depth) shall be surrounded by an<br />
aquatic bench. The aquatic bench shall extend inward from the normal pool edge 10-15<br />
feet on average and have<br />
a maximumm depth <strong>of</strong> 18 inches below the normal pool water<br />
surface elevation (see Figure 3-12).<br />
• The<br />
pond edgee shall have<br />
turf reinforcing mesh or riprap covering the area from 2 feet<br />
above the normal pool to 2 feet below the normal pool to protect areas <strong>of</strong> the pond that will<br />
be exposed to<br />
wave action. Appendix D provides wind roses for <strong>Wichita</strong> during each<br />
month <strong>of</strong> the year to aid in<br />
locating areas that will require reinforcement.<br />
Local winds are<br />
most pronounced coming from the north and south<br />
directions.<br />
• The<br />
contours and shape <strong>of</strong> the permanent pool should be irregular to provide a natural<br />
landscape effect.<br />
Page 3 - 32<br />
<strong>Volume</strong> 2, Technical Guidance
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