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Innovative Approaches for Managing Stormwater Runoff: Constructed Wetlands

Innovative Approaches for Managing Stormwater Runoff: Constructed Wetlands

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Innovative Approaches for Managing Stormwater Runoff: Constructed Wetlands

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  1. Innovative Approaches for Managing Stormwater Runoff: Constructed Wetlands March 4, 2009 32nd Annual Airport Conference Hershey, PA

  2. Project Background Kim Minkel, NFTA

  3. Buffalo Niagara International Airport • 110 daily flights, 25 gates • 96” Avg. snow fall • ~330,000 gallons glycol • 1.2 MGD stormwater runoff

  4. Deicing operations and practices • Deicing at the gates. • Storm sewer design. • Parallel system routes storm and glycol water. • Glycol storage before discharging to a POTW. • Glycol capture by GRV’s 45-48%.

  5. Environmental Concerns • 1994 - SPDES permit • 30 mg/L BOD5 and 500 mg/L glycol limit • Frequent permit exceeded • 1995 - Vacuum sweeping • 3/1998 - The Citizen Alliance Group targets NYSDEC • 4/1998 NYSDEC issues Order on Consent - Comply by 2/99

  6. Over the next 4 years… • ~$13.1 million spent • deicing controls, • storage and • treatment • Permit limits still exceeded • Neighbor complaints • Town prohibits discharge

  7. Concerns • Point source limit applying to a non-point source operation – Permit modification • It’s not working –treat everything or reduce use? • Large volumes – how do you treat this cost effectively? • How do you pay for this?

  8. Action Items • Modify permit – stream impact • Treatment Alternatives (non-point source) • Eliminate (reduce) glycol • Open SPDES permit • 2004 – Generic RFP issued • Petition for funding

  9. Alternatives considered • Dedicated sewer line to POTW • Anaerobic/aerobic onsite treatment • Membrane bioreactors • Recycling • Infratek systems • Reed bed subsurface wetland • Centralized deicing recycling

  10. Subsurface engineered wetland • Advantage – • Lowest 20 year combined capital and operating cost • Effective treatment for stormwater • Totally Green process • Disadvantage – • Space constraints • Public acceptance (Will it work?)

  11. Go for it! • 2005 - RFP for a Treatability Study and Conceptual design • 2006 - Awarded to Jacques Whitford/NAWE/Urban • Treatability study showing >95% reduction in BOD • 2007- Design phase completed

  12. Stormwater ManagementImpacts GARRET A. MEAL, P.E., URBAN ENGINEERING

  13. URBAN ENGINEERS Buffalo Engineering firm with 10 offices 475 staff along the East Coast Extensive airport and civil transportation experience NY and local environmental permitting experience

  14. Existing Infrastructure • Storm System • Extensive Storm Network • Stormwater Vault (3+ MG) • Outfall • Glycol Containment • Major pipes • Glycol storage tanks • Snow melt pad • Sanitary sewer pump station

  15. Objectives • Treat Glycol Concentrate • Treat Glycol Contaminated Storm • Maintain Runoff Control • Reduce or Control Deicing costs

  16. What needs to be treated? • Concentrate – 100% • Simple • Common Pumped Discharge to sanitary • Replace pumps, discharge to WTS

  17. What needs to be treated? • Storm • Would require 15 Million Gallons storage for 10 yr storm • 25 Million Gallons for 100 yr storm • First Flush

  18. Stormwater Management • Existing Design – Detention • Design Storm • Proposed Design for WTS Influent

  19. Design Storm

  20. First Flush Collection

  21. Stormwater Management Strategies • Divert upstream areas directly to wetlands, where possible • Utilize wetlands for storm detention • Utilize glycol infrastructure year round • Design additional pumping capacity • Evaluate emergency overflows • Surface storage of severe storms

  22. Conclusions • Storm Water Management Plan • Know what you are handling • How will you capture and hold water for treatment • Evaluate Resources – Can primary use be modified

  23. Glycol Treatment Scott Wallace, JW NAWE

  24. Treatment Objectives • Provide treatment of contained deicing fluid • Design system for integration into airfield • Integrate system into existing stormwater management

  25. Why Wetlands? • Subsurface flow constructed wetlands do not pose a bird-aircraft strike hazard (BASH) • More stable than mechanical treatment systems • Biggest challenge is oxygen transfer into subsurface flow beds!

  26. Engineered Wetlands

  27. Designed for Treatment

  28. Subsurface Bed Cross Section Mulch Layer Influent Line Water Level Air Line Drain Line

  29. Glycol Treatment • Glycols are readily degradable by bacteria

  30. Managing Peak Events

  31. Cells are designed for a total load of 10,000 pounds of oxygen demand per day The equivalent to 50,000 people Process Sizing and Layout

  32. Construction

  33. Conclusions • System operation scales to glycol usage • In this case, the design had to handle variable flows and concentrations from at gate deicing • The design provides flexible operations • Winter = glycol treatment • Summer = storm storage

  34. Lessons Learned • Communicate early and often • Never forget your key mission • Every airport is different • Design with flexibility in mind • Listen to your stormwater engineer