B. Management Measure for
BridgesSite, design, and maintain bridge structures so that
sensitive and valuable aquatic ecosystems and areas providing important
water quality benefits are protected from adverse effects.
This management measure
is intended to be applied by States to new, relocated, and rehabilitated
bridge structures in order to control erosion, streambed scouring, and
surface runoff from such activities. Under the Coastal Zone Act
Reauthorization Amendments of 1990, States are subject to a number of
requirements as they develop coastal NPS programs in conformity with this
management measure and will have some flexibility in doing so. The
application of management measures by States is described more fully in
Coastal Nonpoint Pollution Control Program: Program Development and
Approval Guidance, published jointly by the U.S. Environmental Protection
Agency (EPA) and the National Oceanic and Atmospheric Administration
(NOAA) of the U.S. Department of Commerce.
This measure requires that
NPS runoff impacts on surface waters from bridge decks be assessed and
that appropriate management and treatment be employed to protect critical
habitats, wetlands, fisheries, shellfish beds, and domestic water
supplies. The siting of bridges should be a coordinated effort among the
States, the FHWA, the U.S. Coast Guard, and the Army Corps of Engineers.
Locating bridges in coastal areas can cause significant erosion and
sedimentation, resulting in the loss of wetlands and riparian areas.
Additionally, since bridge pavements are extensions of the connecting
highway, runoff waters from bridge decks also deliver loadings of heavy
metals, hydrocarbons, toxic substances, and deicing chemicals to surface
waters as a result of discharge through scupper drains with no overland
buffering. Bridge maintenance can also contribute heavy loads of lead,
rust particles, paint, abrasive, solvents, and cleaners into surface
waters. Protection against possible pollutant overloads can be afforded by
minimizing the use of scuppers on bridges traversing very sensitive waters
and conveying deck drainage to land for treatment. Whenever practical,
bridge structures should be located to avoid crossing over sensitive
fisheries and shellfish-harvesting areas to prevent washing polluted
runoff through scuppers into the waters below. Also, bridge design should
account for potential scour and erosion, which may affect shellfish beds
and bottom sediments.
management measure was selected because of its documented effectiveness
and to protect against potential pollution impacts from siting bridges
over sensitive waters and tributaries in the coastal zone. There are
several examples of siting bridges to protect sensitive areas. The Isle of
Palms Bridge near Charleston, South Carolina, was designed without scupper
drains to protect a local fishery from polluted runoff by preventing
direct discharge into the waters below. In another example, the Louisiana
Department of Transportation and Development specified stringent
requirements before allowing the construction of a bridge to protect
destruction of fragile wetlands near New Orleans. A similar requirement
was specified for bridge construction in the Tampa Bay area in Florida
As discussed more fully at the
beginning of this chapter and in Chapter
1, the following practices are described for illustrative purposes
only. State programs need not require implementation of these practices.
However, as a practical matter, EPA anticipates that the management
measure set forth above generally will be implemented by applying one or
more management practices appropriate to the source, location, and
climate. The practices set forth below have been found by EPA to be
representative of the types of practices that can be applied successfully
to achieve the management measure described above.
Additional erosion and sediment control management practices are listed
in the construction section for urban sources of pollution (Management Measure IV.A).
a. Coordinate design with FHWA, USCG, COE, and other State and
Federal agencies as appropriate.
b. Review National Environmental Policy Act requirements to
ensure that environmental concerns are met (FHWA, T6640.8A and 23 CFR
c. Avoid highway locations requiring numerous river crossings.
d. Direct pollutant loadings away from bridge decks by diverting
runoff waters to land for treatment.
Bridge decks should be designed to keep runoff velocities low and
control pollutant loadings. Runoff waters should be conveyed away from
contact with the watercourse and directed to a stable storm drainage,
wetland, or detention pond. Conveyance systems should be designed to
withstand the velocities of projected peak discharge.
e. Restrict the use of scupper drains on bridges less than 400
feet in length and on bridges crossing very sensitive ecosystems.
Scupper drains allow direct discharge of runoff into surface waters
below the bridge deck. Such discharges can be of concern where the
waterbody is highly susceptible to degradation or is an outstanding
resource such as a spawning area or shellfish bed. Other sensitive waters
include water supply sources, recreational waters, and irrigation systems.
Care should be taken to protect these areas from contaminated runoff.
f. Site and design new bridges to avoid sensitive
Pristine waters and sensitive ecosystems should be protected from
degradation as much as possible. Bridge structures should be located in
alternative areas where only minimal environmental damage would result.
g. On bridges with scupper drains, provide equivalent urban
runoff treatment in terms of pollutant load reduction elsewhere on the
project to compensate for the loading discharged off the bridge.
Effectively controlling NPS pollutants such as road
contaminants, fugitive dirt, and debris and preventing accidental spills
from entering surface waters via bridge decks are necessary to protect
wetlands and other sensitive ecosystems. Therefore, management practices
such as minimizing the use of scupper drains and diverting runoff waters
to land for treatment in detention ponds and infiltration systems are
known to be effective in mitigating pollutant loadings. Tables 4-7 (34k) and 4-8 in Section II
provide cost and effectiveness data for ponds, constructed wetlands, and
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