This article was submitted for the May / June 2006 issue of the newsletter.
New Columbus Stormwater Drainage
By , Central Ohio Water Quality Coordinator
The City of Columbus Division of Sewerage and Drainage
has updated policies and requirements for managing
stormwater (rain and snow runoff). Although far from
perfect, changes in the manual improve municipal
stormwater requirements for land development in
Columbus. The Manual is based on Ohio EPA requirements
in its General Construction Stormwater Permit.
so much of the urban area is covered with buildings or
blacktop, there are vast volumes of runoff. Undeveloped
agricultural land sheds about 20 percent of rain volume.
Forested land sheds even less. Paved commercial and
business areas are calculated to run off 80% of
precipitation—and greater volumes of stormwater move
more quickly. There is increased erosion when flooding
carries away sediment and rocks and scours stream
channels. Stormwater flowing on streets goes through
inlets into storm sewer pipes, which empty into a river
or stream. Higher peak volumes can cause flooding
damages along with erosion.
New regulations for land development in the City of
Columbus require keeping stormwater release rates below
certain levels, installing controls like basins or ponds
to filter pollutants, and leaving setback strips along
“Stormwater quantity controls” are constructed
features to catch and hold peak stormwater volumes so
they can be released more slowly. While the new
requirements do allow increases in stormwater runoff
volumes after development, they require that the rate
of release be controlled. Suggested quantity
controls include detention basins, parking lot storage,
underground tank storage, and even “green roofs”
(planted areas on top of buildings that take up
precipitation and reduce runoff).
“Post-construction quality controls” are permanent
features to catch small rain events on-site and reduce
pollutants. The specific list of these controls in the
manual includes: stormwater basins, media filters,
vegetated swales and filter strips, and controls for
commercial activities. Stormwater basins can be dry,
seasonally wet, or constructed wetlands. Media filters
remove pollutants by passing stormwater through a bed of
sand, peat, or some other substance to trap contaminants
- they can look like a large box or a planted garden
with shrubs. Vegetated swales are usually broad, shallow
ditches with grass or other plants. Filter strips are
gently sloping areas with robust vegetation to treat
storm water from small areas less than 5 acres. The
Manual requires that commercial enterprises conduct
activities indoors, cover materials, or use approved
One of the biggest changes is the requirement for a
stream corridor protection zone—50 feet on the smallest
streams and a maximum of 250 feet on the largest
waterways. The required corridor is wider for steep
slopes or wetlands. Building, commercial activities,
dredging and filling, mining, and disturbance of
vegetation are restricted.Unfortunately, the
City continues its policy of allowing the filling of
floodplains if a nearby area is dredged. Also, the
stream corridor protection zone is not required downtown
or in redevelopment areas.
For development, a stormwater report and plan
prepared by professional engineers must be submitted.
Long-term maintenance must be provided. Existing
requirements to control erosion and sediment during
construction remain in place.
The biggest improvement in the manual, other than the
stream corridor protection zone, is the emphasis on
choosing native plants for stormwater facilities. It is
a great achievement that the Columbus Division of
Sewerage and Drainage will now be promoting the use of
adapted native plant species.
The Manual unfortunately does not change the City’s
development policy that allows filling of the floodplain
if an equivalent volume is removed nearby. The Manual
only applies to new development and will not remedy or
restore the many degraded existing waterways in the City
- incentives for stream restoration would help.
Controls reduce post-development rate of release
but allow increased volumes. The new requirements will
result in many more detention basins dotting the
The clay soils of Central Ohio make managing urban
stormwater even harder because water cannot percolate
through soil easily here. Given these soil challenges
and the constraints of past history, the new Columbus
Stormwater Drainage Manual is an important step forward.
Based on Sierra Club recommendations, Columbus Division
of Sewerage and Drainage included wetlands in protection
zones and is promoting the use of native plants. Mud
from construction is one of the biggest polluters of
The Edwin H. and Nellie M. Rausenberger Fund of the
Columbus Foundation has awarded the Ohio Sierra Club a
grant to continue the Central Ohio Sewers Campaign.
Please see in-depth article on page 7 of the
Ohio Sierran newsletter.
Today for a Presentation to Your Community Group
The Columbus Foundation grant is helping the Sierra
Club offer a slide show to civic, religious,
neighborhood and other organizations. The program
explains how sewers and stormwater affect your streams
and neighborhoods. Find out what you can do to reduce
stormwater runoff and how to deal with basement sewage
backups. There are exciting success stories. Contact .
Undeveloped agricultural land sheds about 20 percent
of rain volume. Forested land sheds even less. Paved
commercial and business areas are calculated to run
It is a great achievement that the Columbus Division
of Sewerage and Drainage will now be promoting the use
of adapted native plant species.