FLOOD09481

• County: Statewide
• Community: State
• Stream Name: All
• Basin: Statewide
• Title: Practices in Detention of Urban Stormwater Runoff
• Date: 1/1/1974
• Prepared For: American Public Works Association
• Prepared By: American Public Works Association
• Floodplain - Doc Type: Educational/Technical/Reference Information

the drains for the parking lot should be
designed in anticipation of litter, clogging of
the drains will still be possible. The lot should
be kept as litter-free as possible and drains
should be cleaned of debris periodically.
Large ponds in open spaces will also
collect much debris, not only from the runoff
but from debris generated in adjacent areas.
Even grass clippings can be a problem by
clogging the grating protecting the outlet
structure. Permanent ponds also attract
children who may throw debris into the
water. A debris-retention device on the drain
should be installed to prevent plugging of
outlet structures.
Sediment Control: The reduction of the
velocities of stormwater inflows to a
detention pond causes much of the sediment
carried by the runoff to be deposited in the
pond. Stormwater detention facilities serve as
very efficient sediment traps, and
sedimentation is perhaps one of the most
serious maintenance problems. A typical
installation in northeastern illinois, in an area
where 80 percent of the land is developed,
will accumulate about 3 1/2 acre-feet of
sediment a year per 1,000 acres of drainage
area, based on computation methods and data
oft he United States Soil Conservation
Service. A detailed description of the
sediment collection efficiency of a detention
pond and methods of cleaning the sediment
from the pond are discussed in Chapter 6.
In addition to the solids that enter
detention facilities with runoff flows, another
source of sediment is from erosion of the
banks of the facility. If such areas can be
planted in grass, and the grass not cut, erosion
may be minimized.
Safety Features: Safety features of
detention facilities include fencing, outlet
guards and other measures and devices to
protect the public from the hazards of the
detained water. Although provision of such
safety features does not remove the liability
of the owner for accidents (in some areas of
the country), such devices do minimize safety
hazards and they should be checked regularly
to make sure that they are in good operating
condition.
Maintenance of Equipment: Typical
maintenance of operating equipment installed

in stormwater detention facilities includes the
cleaning of inlet and outlet channels, repairing
all breaks and leaks in pipes, and preventive
maintenance of pumping equipment for those
ponds and basins that require pumped
drainage. The use of pumps for draining
detention facilities can be the most costly
item of operation and maintenance. It is also
one of the most important maintenance items
for ponds and basins that use pumping
because it is necessary to remove stored
storm water when the rainfall subsides to
provide storage for the next rainfall event.
General Maintenance: General
maintenance includes all those items which
are necessary for the efficient operation of
the storage facility and for preserving the
aesthetics of the facility and the surrounding
area. This includes cutting the grass above the
high water level, trimming shrubbery and
painting where needed.
Summary: Proper maintenance and
operation of stormwater detention facilities
will help insure safe, efficient and satisfactory
operation of such facilities. Eight categories
of maintenance and operation that require
attention were outlined and discussed briefly.
The two most important maintenance items
are the proper main tence of the hydraulic
equipment and devices and the control of
sedimentation. Hydraulic maintenance and
operation will be similar to the maintenance
and operation of other stormwater drainage
systems. The control of sedimentation is
discussed in detail in Chapter 6. In addition to
dealing with these two areas of maintenance,
it is also necessary to maintain the detention
facility as an aesthetically pleasing part of the
community.

Costs and Financing of F acili ties
The construction of storm water
detention facilities requires a means of
fmancing. Although the estimation of costs
and methods of fmancing on-site detention
facilities are not particularly unique, when
built by public agencies a discussion of these
two factors is, nevertheless, important.
Requirements imposed by local jurisdictions
for the construction of on-site detention
facilities by land developers, where the
benefits of such storage occur to the general

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