11.01.2015 Views

Volume 2-05, Chapter 3 - City of Wichita

Volume 2-05, Chapter 3 - City of Wichita

Volume 2-05, Chapter 3 - City of Wichita

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Section 3.2.1 - Stormwater Pond<br />

1' MIN. FREEBOARD<br />

100 - YEAR<br />

ELEVATION<br />

PERMANENT POOL<br />

ELEVATION<br />

12" - 18"<br />

10' - 15'<br />

AQUATIC BENCH<br />

10'<br />

SAFETY BENCH<br />

IF NEEDED<br />

5:1 MAX, OR<br />

10:1 MAX 10:1 MAX<br />

3:1 MAX<br />

EXISTING<br />

GRADE<br />

BASIN<br />

FLOOR<br />

2:1 MAX<br />

EMERGENT WETLAND VEGETATION<br />

Figure 3-12 Typical Stormwater Pond Geometry Criteria<br />

D. PRETREATMENT / INLETS<br />

• Each pond shall have a sediment forebay or equivalent upstream pre-treatment at each<br />

inlet. A sediment forebay is designed to remove incoming larger sediment from the<br />

stormwater flow prior to dispersal in the larger permanent pool. Pretreatment consists <strong>of</strong> a<br />

separate cell, formed by an acceptable barrier between the forebay and pond. A forebay<br />

is to be provided at each inlet, unless the inlet provides less than 10% <strong>of</strong> the total design<br />

storm inflow to the pond. In some design configurations, the pretreatment volume may be<br />

located within the permanent pool.<br />

• A forebay must be sized to contain 0.1 acre-inch per impervious acre <strong>of</strong> contributing<br />

drainage and should be 4 to 6 feet deep. The pretreatment storage volume is part <strong>of</strong> the<br />

total WQ v requirement and may be subtracted from WQ v for permanent pool sizing.<br />

• A fixed vertical sediment depth marker shall be installed in the forebay to measure<br />

sediment deposition over time. The bottom <strong>of</strong> the forebay may be hardened (e.g., using<br />

concrete, paver blocks, etc.) to make sediment removal easier.<br />

• Pond inflow channels are to be stabilized with flared riprap aprons, or the equivalent. Inlet<br />

pipes to the pond can be partially submerged. Inflow pipe, channel velocities, and exit<br />

velocities from the forebay must be nonerosive.<br />

E. OUTLET STRUCTURES<br />

• Flow control from a stormwater pond is accomplished with the use <strong>of</strong> a principal spillway<br />

consisting <strong>of</strong> a concrete riser and barrel. The riser is a vertical pipe, typically with several<br />

weirs and/or orifices at various levels. The outlet barrel is a horizontal pipe attached to the<br />

riser that conveys flow under the embankment (see Figure 3-13). Where practicable, the<br />

riser should be located within the embankment for maintenance access, safety and<br />

aesthetics.<br />

<strong>Volume</strong> 2, Technical Guidance Page 3 - 33

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!