Page 461 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch12_398-456.qxd 8/4/10 9:37 PM Page 419

12.5 Urban Runoff Control Practices 419

Pond buffer Emergency
(25 feet minimum) 25´
spillway
Overflow spillway

Hardened pad
Forebay

Inflow Irregular pool shape
6 to 8 feet deep
Berm Outfall
Riser/barrel
Riser in
Maintenance embankment
access road Aquatic bench

Safety bench
Native landscaping around pool
Plan view

Embankment
Riser
Extreme flood control Emergency
spillway
Overbank flood control
Channel protection
Overflow Safety
spillway Aquatic bench
bench
Water quality
Inflow Stable
Wet pool outfall
Forebay
Pond drain
Barrel
Reverse pipe Anti-seep collar or
filter diaphragm
Profile

Figure 12.7 Wet Pond. Conversion factor: 1 1 ft 0.3048 m
(Source: New York Department of Environmental Conservation)

replaced with runoff as shown in Fig. 12.7. Once the capacity of a wet pond is exceeded,
collected runoff is discharged through an outlet structure or an emergency spillway.
Pollutant Removal. The primary pollutant removal mechanism in wet ponds is settling.
The ponds are designed to collect stormwater runoff during rainfall and to detain it until
additional stormwater enters the pond and displaces it. While the runoff is detained, set-
tling of particulates and associated pollutants takes place in the pond. Wet ponds can also
remove pollutants from runoff through vegetative uptake. Wet ponds should be vegetated
with native emergent aquatic plant species, which can remove dissolved pollutants such as
nutrients from the runoff before it is discharged to the receiving water.
Design Considerations. Wet ponds typically are designed with a number of different
water levels. One level of the pond has a permanent pool of water. The next level