Transcript stormwater_bmps_for_highways.ppt

STORMWATER BMPS
FOR HIGHWAYS
CHALLENGES
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Stormwater Mgt. Vs Highway Safety
Limited Right-of-way
Highly Impervious Drainage Areas
Extensive Cuts and Fills
Spill Potential
Use of Deicing & Anti-skid Materials
Higher Concentrations of Pollutants
Thermal Impacts in Summer & Winter
TYPICAL POLLUTANTS
IN HIGHWAY RUNOFF
Pollutant
Source
Particulates
Pavement wear, vehicles, atmosphere, anti-skid,
maintenance activities
Nitrogen, Phosphorus
Atmosphere, fertilizers
Lead
Leaded gasoline, tire wear
Zinc
Tire wear, motor oil and grease
Iron
Auto body rust, steel highway structures, engine
parts
Copper
Metal plating, bearing & bushing wear, brake linings,
fungicides & insecticides
Cadmium
Tire wear, insecticides
Chromium
Metal plating, engine parts, brake lining
Nickel
Diesel fuel, gasoline, lubricating oil, metal plating,
brake lining, asphalt paving
Manganese
Engine parts
Cyanide
Anti-caking compounds in deicing salts
Sodium Chloride & Calcium Chloride
Deicing salts
Sulphates
Roadway beds, fuel, deicing salts
TYPICAL POLLUTANTS
IN HIGHWAY RUNOFF
Pollutant
Concentration (mg/l)
Total Suspended Solids (TSS)
45 - 798
Volatile Suspended Solids (VSS)
4.3 – 79
Total Organic Carbon (TOC)
24 – 77
Chemical Oxygen Demand (COD)
14.7 – 272
Biochemical Oxygen Demand (BOD)
12.7 – 37
Nitrate + Nitrite (NO3 + NO2 )
0.15 – 1.636
Total Kjeldahl Nitrogen (TKN)
0.335 – 55.0
Total Phosphorus (P)
0.113 – 0.998
Copper (Cu)
0.022 – 7.033
Lead (Pb)
0.073 – 1.78
Zinc (Zn)
0.056 – 0.929
Fecal coliform (organisms/100 ml)
50 - 590
BMP CONSIDERATIONS
• Higher levels of Suspended Solids
– Vegetated Systems
• Grassed Swales
• Filter Strips
• Bioretention
– Structural Elements
• Catch Basin Inserts
• Filters
• Manufactured Treatment Units
– Maintenance Measures
• Street Sweeping
• Vacuuming
BMP CONSIDERATIONS
• Vegetated BMPs effective in
removing pollutant loads if properly
designed
• Spill Containment
– Subsurface, infiltration, or vegetative
systems may have to be replaced
• Deicing & Antiskid application may
adversely affect BMPs
BMP CONSIDERATIONS
• Temperature Impacts on aquatic life in
receiving waters
– Vegetated Systems replace Concrete
– Discharge from Extended Detention
through Vegetated Swales or Buffers
– Extended Detention Design
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Minimize Permanent Pool
Preserve existing Shade Trees
Align Pond in North-South Direction if possible
Avoid excessive Riprap & Concrete
HIGHWAY/ROAD
STRATEGIES
• Utilize sod-forming grasses adjacent
to Roadway Shoulders & for
Vegetated Swales to serve as Filters
for Suspended Solids and Metals
HIGHWAY/ROAD
STRATEGIES
• Utilize non-invasive native species
vegetation in lawn areas, on slopes and
within wetland reconstruction/ banking
areas to enhance Water Uptake and the
storage of certain pollutants in plant
tissue.
HIGHWAY/ROAD
STRATEGIES
• Limit use of curb-gutter sections as
much as practical for Filtering and
Temperature considerations
HIGHWAY/ROAD
STRATEGIES
• Limit use of storm sewers as much
as practical for Filtering and
Temperature considerations.
HIGHWAY/ROAD
STRATEGIES
• Consider Bioretention capability in
the design of new detention basins
(Dry Extended Detention Basin
design)
HIGHWAY/ROAD
STRATEGIES
• Monitor the effectiveness of existing
Constructed Wetlands, updating the
current design practices as necessary
HIGHWAY/ROAD
STRATEGIES
• Consider alternative methods of
energy dissipation (in lieu of rock
aprons) at culvert and storm sewer
outfalls for Temperature
considerations
Perforated Pipe in an Aggregate
Aggregate Trench Spreader with
Filter Strip
Trench
HIGHWAY/ROAD
STRATEGIES
• Where practical, discharge storm
sewers into wetland areas or
vegetated swales for Filtering &
Temperature considerations
HIGHWAY/ROAD
STRATEGIES
• Consider vegetated islands in lieu of
concrete islands for Filtering and
Temperature considerations
HIGHWAY/ROAD
STRATEGIES
• Consider use of Infiltration Berms
and Retentive Grading in areas
downslope of the roadway
Infiltration Berm Cross-section
Series of Woodland Infiltration Berms
HIGHWAY/ROAD
STRATEGIES
• Continue to monitor & minimize
volume of winter maintenance
materials to Minimize Pollutant
Loadings
HIGHWAY/ROAD
STRATEGIES
• Continue to protect all salt storage &
loading areas from weather
influences to Minimize Pollutant
Loadings
HIGHWAY/ROAD
STRATEGIES
• Consider practices to dilute flows
where high concentrations of salts
are anticipated to Minimize Pollutant
Loadings
HIGHWAY/ROAD
STRATEGIES
• Consider Porous Pavement on Parkand-Ride sites and for Department
building site parking lots
HIGHWAY/ROAD
STRATEGIES
• Consider Dry Wells and other
Subsurface Infiltration for
Department building roof drains