Economics of Low Impact Development (LID)

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Economics of Low Impact Development (LID)

• Houston Land/Water Sustainability Forum

David W. Peters, P.E., CFM, D.WRE February 6,
2008
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Summary

• The Private Public Private Responsibility
  Shift
• EPA Case Studies
• Local Church Revision to LID
• Final Notes

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The Private Public Private Responsibility
Shift

• Agricultural Beginnings prior to 1940
• Farmers Objective Capture and retain as much
  moisture as possible

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The Private Public Private Responsibility
Shift

• Subdivisions developed rapidly form 1950 through
  1985
• Homeowners Objective Drain and remove rainfall
  as quickly as possible

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The Private Public Private Responsibility
Shift

• Through the decades the responsibility for the
  rain has shifted from the private land owner to
  the public agencies (City, County, Flood Control)
• Economic Question to ponder is which is less
  costly
• Private Owner handling the raindrop where it
  falls
• Private Owner passing the raindrop to Public
  Entity to handle

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EPA Case Studies

• The EPA presented 17 case studies in a report
  titled Reducing Costs through Low Impact
  Development (LID) Strategies and Practices
• Report is available online at
• http//www.epa.gov/owow/nps/lid/costs07/
• Primary LID Techniques are
• Bioretention
• Grassed Swales
• Reduced Impervious Area
• Cluster Building

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EPA Case Studies

• Auburn Hills Subdivision, Wisconsin
• Overall Savings 32
• 56 of savings was in storm water management
  using bioswales and vegetated swales
• Development used cluster development with 40
  percent open space
• Savings reduction were also realized in water and
  sewer installation and are not including in the
  32 LID savings

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EPA Case Studies

• Mill Creek Subdivision, Illinois
• 1,500 acre mixed use community with overall
  savings of 30. Savings was 3,500 per lot.
• 70 of savings was in storm water management
  using vegetated swales
• Development used cluster development with 40
  percent open space
• In addition to savings on development, the lots
  near amenities with view of open space and bike
  trails were sold at 3,000 to 17,000 premiums

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EPA Case Studies

• Somerset Subdivision, Maryland
• 80 acre residential community with 200 homes on
  0.25 acre lots. Overall savings of 32. Savings
  was 4,000 per lot.
• Half of subdivision was conventional and half was
  LID
• Each 10,000 sq. ft. lot had a 400 sq. ft.
  bioretention cell.
• LID runoff was 20 percent less and metals showed
  an average of 30 percent reduction

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Local Church Revision to LID

• Church construction required a 10 ac-ft detention
  pond to meet County standards.
• Pond location at rear of property required piping
  to rear and then back to discharge at front.
• Shallow outfall required shallow pond or pumped
  discharge

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Local Church Revision to LID

• LID Options Considered
• Add grass strip filter to parking areas and allow
  parking areas to flood to 6 inches during extreme
  events (gt 10 year recurrence)
• Convert grassed areas near front and side of
  church to depressed rain gardens
• Flooding of parking lot and rain gardens
  controlled by regulated outlet at discharge from
  property

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• Church Site Layout

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Final Notes

• Project overall objectives need to be examined
  when LID options are considered
• Economic benefits may not only be in initial
  construction cost savings, but increased values
  of LID developed properties
• The closer to the source that storm water can be
  mitigated the lower the transmission costs will
  be
• Creativity and flexibility needs to be applied to
  each project based on final objectives
• Shifting storm water maintenance to the private
  homeowner may be problematic unless legally
  encumbered into the property deed requirements