Feasibility of Stormwater Harvesting in Southern California


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Feasibility of Stormwater Harvesting in Southern California

  1. 1. Richard Lucera, PE RBF Consulting November 3, 2010
  2. 2. <ul><li>Rainwater Harvesting Concept </li></ul><ul><li>Historic Applications </li></ul><ul><li>Notable Nationwide Programs </li></ul><ul><li>Evolution of California MS4 Regulations </li></ul><ul><ul><li>Bay Area MRP </li></ul></ul><ul><ul><li>Involves Inherent Challenges to Implementation Not Faced Elsewhere </li></ul></ul>
  3. 3. <ul><li>Technical Feasibility </li></ul><ul><ul><li>Water Balance Considerations, Stormwater Supply Versus Demand </li></ul></ul><ul><ul><li>Water Quality Considerations </li></ul></ul><ul><li>Economic Feasibility </li></ul><ul><ul><li>Cost Data Residential Installation </li></ul></ul><ul><ul><li>Operational Cost </li></ul></ul><ul><ul><li>Valuating Harvested Water </li></ul></ul><ul><ul><li>Return on Investment </li></ul></ul><ul><li>Conclusions and Recommendations </li></ul>
  4. 4. <ul><li>Golden Rule of Rainwater Harvesting </li></ul><ul><ul><li>Supply Must Equal or Exceed Demand </li></ul></ul><ul><ul><ul><li>Urban Landscape Demand – Seasonally Influenced </li></ul></ul></ul><ul><ul><ul><ul><li>Turf is Major Traditional Dictating Driver of Demand </li></ul></ul></ul></ul><ul><ul><ul><ul><li>1 Inch Per Week Traditional Rule of Thumb </li></ul></ul></ul></ul><ul><ul><ul><ul><li>On Going Evolution of Landscape Ordinances in California </li></ul></ul></ul></ul>
  5. 5. <ul><li>Golden Rule of Rainwater Harvesting </li></ul><ul><ul><li>Supply Must Equal or Exceed Demand </li></ul></ul><ul><ul><ul><li>Acceptable Household Demands – Non Influenced Seasonally </li></ul></ul></ul><ul><ul><ul><ul><li>Toilets, Laundry, Car Washing, Dish Washing </li></ul></ul></ul></ul><ul><ul><ul><ul><li>“AWWA Residential End Use Study” </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>1.6 Gal/Flush, 6 Flushes Per Day </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>18-25 Gal/ Wash Load, 2.6 Wash Loads Per Week </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>8 Gal/Dishwashing Cycle, 0.7 Cycles Per Day </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Typical Household Range Indoor Use 2,000 – 3,000 Gal/Month </li></ul></ul></ul>
  6. 6. <ul><li>No System is 100% Efficient </li></ul><ul><ul><ul><li>Precipitation Losses </li></ul></ul></ul><ul><ul><ul><ul><li>High Intensity Rainfall Losses – Gutter Splash-out, Capacity Limitations on the Collection System </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Infiltration within Pervious Areas </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Evaporation (Applicable to “Rough” Collection Systems) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Overflow When Storage is Full </li></ul></ul></ul></ul><ul><ul><ul><li>Traditional Rule of Thumb 75% - 90% Capture Rate (“Texas Manual on Rainwater Harvesting”) </li></ul></ul></ul><ul><ul><ul><ul><li>Southern California Could Realistically Be Lower </li></ul></ul></ul></ul>
  7. 17. <ul><li>Advantages of Rainwater </li></ul><ul><ul><li>Naturally “Soft” </li></ul></ul><ul><ul><ul><li>Benefit for Appliances </li></ul></ul></ul><ul><ul><li>Sodium Free </li></ul></ul><ul><ul><ul><li>Benefit if Intended for Potable Use </li></ul></ul></ul><ul><ul><li>Promotes Healthy Plant Growth </li></ul></ul><ul><ul><li>Generally Suitable for Irrigation and Potable Use (When Incorporated with Adequate Treatment, Testing, and Dependable System Maintenance Plan) </li></ul></ul>
  8. 18. <ul><li>General Challenges Associated with Rainwater </li></ul><ul><ul><li>Tends to be Slightly Acidic </li></ul></ul><ul><ul><li>Contact and Transport of Pollutants within Catchment Area </li></ul></ul><ul><ul><ul><li>Dust, Dirt, Fecal Matter, Plant Debris </li></ul></ul></ul>
  9. 19. <ul><li>Southern California Challenges with Rainwater Harvesting </li></ul><ul><ul><li>No Specific Federal or State Standards for Harvested Rainwater </li></ul></ul><ul><ul><ul><li>Not Addressed in AB 1420 or AB 1560 </li></ul></ul></ul><ul><ul><li>Large Scale Implementation Would Prove Problematic for Compliance with Local Hydromodification Standards </li></ul></ul>
  10. 20. <ul><li>Dependant Upon Location and End Use </li></ul><ul><ul><li>Geographic Location, Which Dictates Size of Required Storage </li></ul></ul><ul><ul><ul><li>Tank Size and Material Are Largest Factors in Overall Cost </li></ul></ul></ul><ul><ul><ul><li>Other Typical Minimum Requirements </li></ul></ul></ul><ul><ul><ul><ul><li>Collection/Gutter System </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Roof Washers (Necessary for Drip Irrigation) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pumps and Potentially Separate Pressure Tanks </li></ul></ul></ul></ul>
  11. 21. <ul><li>Potable or Contact Uses Also Require Additional Filtering and Disinfection </li></ul><ul><ul><li>Typical Filters </li></ul></ul><ul><ul><ul><li>Cartridge Filter, 3 micron or greater removal </li></ul></ul></ul><ul><ul><ul><li>Reverse Osmosis Filter, 0.001 micron or greater removal </li></ul></ul></ul><ul><ul><li>Disinfection Techniques </li></ul></ul><ul><ul><ul><li>UV Light – Effective for Low/Moderate Coliform Influent </li></ul></ul></ul><ul><ul><ul><li>Chlorine – Potential Health Risk From Overdose </li></ul></ul></ul><ul><ul><ul><li>Ozone - Requires Frequent Testing and Monitoring, Also a Circulation Pump </li></ul></ul></ul>
  12. 22. <ul><li>Typical Initial Cost Range 10,000 Gallon System </li></ul><ul><ul><li>Fiberglass Tank…………………………....$20,000 </li></ul></ul><ul><ul><li>Vinyl Gutters/Collection………………....$1,500 </li></ul></ul><ul><ul><li>“Smart Valve” Roof Washer………………..$200 </li></ul></ul><ul><ul><li>Pump and Pressure Tank………………....$1,000 </li></ul></ul><ul><ul><li>RO Filter…………………………………….$2,000 </li></ul></ul><ul><ul><li>UV Disinfection………………………...….$1,500 </li></ul></ul><ul><ul><li>Backflow Prevention (Cross Connection)…$500 </li></ul></ul><ul><ul><li>Total $26,700 </li></ul></ul>
  13. 23. <ul><li>Approximate Annual Operation and Maintenance Cost </li></ul><ul><ul><li>Replace UV Bulb (One Time)……..……...$500 </li></ul></ul><ul><ul><li>Clean Gutters/Collection Pipe.…………..$500 </li></ul></ul><ul><ul><li>Clean “Smart Valve”……………...............$200 </li></ul></ul><ul><ul><li>Allowance for Other Miscellaneous..……$100 </li></ul></ul><ul><ul><li>Total $1,300 </li></ul></ul>
  14. 24. <ul><li>San Diego $1.79 (OMWD) </li></ul><ul><li>Austin $0.75 (Austin Water Utility) </li></ul><ul><li>Sydney $1.15 (Sydney Catchment Authority) </li></ul>
  15. 25. <ul><li>Stormwater Supply Versus Demand </li></ul><ul><ul><li>Overall Rainwater Supply in Southern California Cannot Realistically Meet Traditional Landscaping (i.e. Turf) Needs </li></ul></ul><ul><ul><li>Residential Application for “Indoor Only” Needs Much More Technically Feasible, However….. </li></ul></ul><ul><ul><li>Potable/Contact Use Not Advisable Given the Risks Versus the Rewards </li></ul></ul><ul><ul><li>High Density/Commercial Use Can Become Highly Problematic Due to Limitations on Storage Necessary for Increased Per Capita Demand – More Suitable to Address Limited Irrigation Needs </li></ul></ul>
  16. 26. <ul><li>Water Quality Considerations </li></ul><ul><ul><li>Southern California Faces Similar Water Quality Challenges as Other Parts of the Country Plus….. </li></ul></ul><ul><ul><li>Lack of Technical Guidance or Regulation at State Level </li></ul></ul><ul><ul><li>Potential Risk Associated with High Particulate Matter </li></ul></ul><ul><ul><li>Conflict Between Local Hydromodification Discharge Standards and Large Scale Rainwater Harvesting </li></ul></ul>
  17. 27. <ul><li>Economic Feasibility </li></ul><ul><ul><li>Capital Cost Residential Household – Approximately $25,000 </li></ul></ul><ul><ul><li>Operation and Maintenance – Conservative Range $1,500 </li></ul></ul><ul><ul><li>Return on Investment - Southern California (Like Other Regions) Requires a Capital Investment that Far Exceeds the Retail Value of “Harvestable” Water, Even When Based Upon Local Rates </li></ul></ul><ul><ul><ul><li>Local Rates Would Have to Escalate to Approximately 25 Times Current Levels to Justify Use Annually, Assuming 20 Year Life </li></ul></ul></ul>
  18. 28. <ul><li>“ Texas Manual on Rainwater Harvesting”, Texas Water Development Board, Third Edition, 2005. </li></ul><ul><li>“ City of Tucson Water Harvesting Guidance Manual”, City of Tucson Department of Transportation Stormwater Management Section, October 2005. </li></ul><ul><li>“ Managing Wet Weather with Green Infrastructure, Municipal Handbook, Rainwater Harvesting Policies”, Christopher Kloss, Low Impact Development Center, December 2008. </li></ul><ul><li>“ Rainwater Harvesting with Cisterns for Landscape Irrigation”, Florida Rainwater Harvesting Initiative, First Edition October 2009. </li></ul><ul><li>“ Water Use Classification of Landscape Species, A Guide to the Water Needs of Plants”, L. R. Costello and K.S. Jones, University of California Cooperative Extension, April 1994. </li></ul><ul><li>“ San Diego County Water Authority Agricultural Water Management Plan” </li></ul><ul><li>“ Operation H2O Annual Report 2009”, San Diego County Water Authority. </li></ul><ul><li>“ Ohio Department of Health Final Rules, 3701-28-09 Continuous Disinfection”, www.odh.ohio.gov/Rules/Final/Chap28/Fr28_lst.htm </li></ul><ul><li>“ Guidelines on Rainwater Catchment Systems for Hawaii”, Manoa (HI): College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. </li></ul>
  19. 29. Richard Lucera, PE RBF Consulting 9755 Clairemont Mesa Blvd, Suite 100 San Diego, CA 92127-1324 858.614.5000 [email_address]