Economics of Low Impact Development (LID)

1. Economics of Low Impact Development (LID) Houston Land/Water Sustainability Forum David W. Peters, P.E., CFM, D.WRE February 6, 2008

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

3. The Private – Public – Private Responsibility Shift • Agricultural Beginnings – prior to 1940 • Farmers Objective – Capture and retain as much moisture as possible

4. The Private – Public – Private Responsibility Shift • Subdivisions developed rapidly form 1950 through 1985 • Homeowners Objective – Drain and remove rainfall as quickly as possible

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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 (> 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

12. Church Site Layout

13. 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