Page 460 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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418 Chapter 12 Urban Runoff and Combined Sewer Overflow Management

Maximum elevation
of safety storm
Maximum elevation Emergency
of ED pool spillway
Existing
vegetation retained
Aquatic
RIP-RAP pilot channel bench
Inflow Sedi-
ment
forebay Outfall
Micropool
Safety
bench

Maintenance access
to micropool
Plan view

Embankment

Riser
Flood control Emergency
Overbank protection spillway
Channel protection
Water quality
Hood
Stable
Inflow outfall

Forebay
Micropool Barrel
Anti-seep collar or
filter diaphragm
Profile

Figure 12.6 Extended Detention Dry Pond
(Source: New York—Department of Environmental Conservation)

Maintenance Requirements. Maintenance of water quality dry ponds is important.
Regular mowing, inspection, erosion control, and debris and litter removal are
necessary to prevent significant sediment buildup and vegetative overgrowth. Also, periodic
nuisance and pest control could be required. The pond slopes should allow for mowing,
and access roads should be provided.

Limitations on Use. Like other stormwater structures used in large watersheds, a physical
constraint on the construction of water quality dry ponds is their large land requirements.
For this reason, locating dry ponds in new developments is usually more practical than
constructing them in already developed areas. Other physical constraints include the to-
pography and the depth to bedrock.

12.5.3.2 Wet Ponds The design of wet ponds is similar to that of dry ponds and con-
structed wetlands. In wet ponds, stormwater runoff is directed into a constructed pond or
enhanced natural pond, in which a permanent pool of water is maintained until being