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Smaller municipalities and other agencies were
brought under the stormwater regulations of the Clean Water Act three
years ago. The five-year implementation cycle will be complete in 2008.
Road and street construction and maintenance are
affected by the program’s six goals:
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Initiate a comprehensive, independent analysis
of stormwater treatment practices now in use.
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Develop a stormwater treatment practice
assessment.
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Develop a draft assessment protocol that
includes a decision tree to aid in deciding on treatment and monitoring.
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Test the assessment protocol on selected field
sites.
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Collaborate with other agencies and groups to
further develop the protocol.
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Begin outreach and dialogue with workshops and
public forums.
These same agencies, as they work their way into
using the regulations, can control costs by using low-impact-development
practices for stormwater management.
What is LID?
Low-impact-development strategies let water
infiltration occur as closely to the original area of rainfall as
possible.
Landscaping, including soil placement and
vegetation, can help reduce the need for expensive engineered runoff
removal systems.
Designs need to include ways to avoid pollution
from stormwater runoff — another reason for absorbing the moisture as
quickly as possible.
Most pollutants get carried along in the first
half inch of the storm. LID Systems need to include a buffer to filter
the pollutants, particularly during this period. Several companies make
retrofits for existing stormwater inlets to do this job, including
AquaShield, Stormtreat Systems, Stormceptor, and Stormwater Management.
Best LID stormwater practices include:
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Reduction of the volume of runoff and
decentralizing flows. This can be created with a series of smaller
retention/detention areas that allow localized filtration rather than
carrying the runoff to a remote collection area.
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Bioretention cells generally are made up of
grass buffers, sand beds, a ponding area for excess runoff, planting
soil, and vegetation. These provide storage for the water away from
roadways and buildings.
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Grass swales can function as alternatives to
curb and gutter systems, generally along residential streets or roads.
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Filter strips can be designed as landscape
features and direct water into vegetation detention or sand filter
areas.
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Directing stored water to localized detention
cells where it can be used for dry-period irrigation.
On site
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LID site design elements include decreasing
impervious surfaces that prevent natural filtration, such as:
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Reducing roadway surfaces and retaining more
permeable land. Using longer, undulating roads that create more
available lot frontage can reduce pavement needs and runoff at the same
time. Shared driveways, landscaped detention islands within cul-de-sacs,
or alternate designs for turn-around areas can be used.
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Permeable pavement surfaces can be built from
a variety of materials, including traditional asphalt, concrete, gravel,
or pavers. A permeable road or street lets water flow through, reducing
or eliminating the need for stormwater structures.
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Vegetative systems create a lightweight
permeable surface on an area, such as along streets.
LID costs
Use of engineered grass swales and other LID
methods may cost only 35 to 50% of more conventional controls.
Even so, large or highly industrialized cities
may have pollutant levels that can’t be handled by LID filtration. And,
local regulations may need to be overhauled to allow use of LID methods.
In Minnesota
Minnesota is a good example of a state that has
provided municipalities with help in meeting stormwater regulations.
Assessment protocol progress is a key part of their program, with a
project team working with the University of Minnesota Extension Services
offering help to consultants as well as municipal and county engineers.
The team drafted an Assessment Protocol Outline last year.
Their program will monitor various stormwater
management practices as the protocol continues to be developed. Work
will include assessment of three underground proprietary devices for the
Local Road Research Board.
Input sessions last year were geared to several
objectives:
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To determine the priority of stormwater
practices to have assessment protocols developed for and to be
monitored.
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To determine specific performance information
to be known as priority stormwater practices.
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To discover opportunities to partner with
on-going stormwater practice installation and monitoring activities.
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To gather lessons learned from on-going and
past water-quality monitoring efforts.
Revised stormwater rules now require stormwater
permits for cities over 10,000, or over 5,000 if the municipalities are
located within a half mile of outstanding value resource water or
impaired water.
Small municipalities must develop a Stormwater
Pollution Prevention Program that covers:
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Public education and outreach.
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Public participation/involvement.
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Illicit discharge detection and elimination.
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Construction site runoff control.
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Post-construction site runoff control.
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Pollution prevention/good housekeeping.
Wading through regs
Stormwater regulations are complicated and
likely to become more so.
Dr. Stephen J. Souza at Princeton Hydro in
Ringoes, New Jersey has developed an introduction to help municipal
officials understand the new regulations.
“Over 60% of existing water quality problems are
the result of non-point source pollution linked to stormwater runoff,”
Souza says. Stormwater runoff can degrade the quality of wetlands,
surface water, and groundwater. This impacts the ecological,
recreations, and aesthetic attributes of these resources. Degraded
surface and groundwater can cause or lead to human health impacts.
Use of a control program is especially needed in
developed areas where storm runoff is about 55% of the total downfall
compared to 10 to 15% runoff on undeveloped land.
“States were required to adopt municipal
stormwater management rules by March of 2003,” Souza says. The rules
pertain to MS4s — Municipal Separate Storm Sewer Systems. The intent of
the new rules is to improve the quality of surface waters, letting them
meet designated uses.
Rules affect both large and small
municipalities, but requirements differ. Both Tier A (large) and Tier B
(small) cities must develop and adopt stormwater management plans,
develop and adopt a stormwater management ordinance, conduct public
education, and implement additional measures as needed.
The regulation timetable is full implementation
by 2008.
Construction site regulations especially affect
agencies and erosion control practices must be enforced at all
construction sites, Souza says. Pollution prevention measures must be
implemented at construction sites. The practices apply to disturbances
of greater than one or more acres of land. The regulations do not do
away with the need for county permits for disturbances of 5,000 square
feet or more.
After construction, continued stormwater
measures include adoption of a stormwater management plan, adoption and
implementation of a stormwater management ordinance, ensured maintenance
of stormwater best-management practices, implementation of state
stormwater management regulations, and meeting design standards for
storm drain inlets.
Source control activities required include
pollution prevention, salt and sand storage, and road erosion control.
For a copy of Souza’s presentation, e-mail him
at
Ssouza@princetonhydro.com.
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