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Source Water Determination

Source Water Determination. And Watershed Sanitary Surveys. October 4, 2013. 2 nd Annual CalDesal Conference. Greg Wetterau, PE, BCEE. Outline. Defining Seawater Intake Alternatives Rules Impacting Classification Treatment and Monitoring Requirements.

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Source Water Determination

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  1. Source Water Determination And Watershed Sanitary Surveys October 4, 2013 2nd Annual CalDesal Conference Greg Wetterau, PE, BCEE

  2. Outline • Defining Seawater • Intake Alternatives • Rules Impacting Classification • Treatment and Monitoring Requirements

  3. Challenges Defining the Ocean as a Source Water • Not envisioned in SDWA regulations, created for “rivers, lakes, reservoirs, springs, and groundwater wells” • Regulations don’t necessarily address health risks specific to seawater • Pathogens different in seawater • Mineral toxicity considerably different in seawater • Water quality monitoring techniques may differ • Permitting approaches need to work with existing classifications, while working to address unknowns

  4. Is Seawater a Surface Water? • SWTR defines as “all water open to the atmosphere and subject to surface runoff” • Giardia and Crypto have low survivability • 1 day survivability 1/8 of rate in freshwater • Primary concern for shellfish • Pathogens of largest concern may bemuch different in seawater Courtesy of Animal Planet, Monsters Inside Me

  5. Pathogens in the Ocean • Risks of contamination from birds, marine mammals and human activity are small, but do exist • Highest risk of microbial contamination from red tides • May exceed 100,000 cells/L • Algae can release harmful toxins • Pathogen removal not specifically required in Florida • In California ocean is classified as surface water

  6. Source Water Alternatives • Two types of Seawater Intakes • Open Intake • Subsurface Intake • Classification of source will determine treatment requirements • Source water assessment and other WQ monitoring used to classify source

  7. Rules Governing Source Determination • Requirements based on various state and federal rules (SWTR, LT2, Title 22) • Source water assessment • Watershed sanitary survey • Determination of GWUDI • LT2 Crypto monitoring Surface water or GWUDI Groundwater Non-Impaired Impaired Highly Impaired Bin 1 Bin 2 Bin 3 Bin 4

  8. Classification of Subsurface Intakes • Groundwater under direct influence (GWUDI) defined as: • “Significant occurrence of insects or other macroorganisms, algae or large diameter pathogens such as Giardia lamblia” • Significant and relatively rapid shifts in water characteristics such as turbidity, conductivity or pH which closely correlate to climatological and surface water conditions • Classification depends on design of wells, however, CDPH generally considers beach wells GWUDI

  9. Dana Point Slant Well • Test Slant Well at Doheny State Beach installed in 2010 • Extends 350’ beneath ocean with 220’ well screen • Maintained 50 ft horizontal separation from creek and 50’ vertical separation from ocean floor • Proposed testing to determine hydraulic connection and microbial presence • Classified as GWUDI

  10. Subsurface Options • Vertical Wells • Slant Wells • Horizontal Wells • Ranney • HDD • Infiltration galleries • Of these alternatives, vertical wells have the highest likelihood of not being classified as GWUDI Photo courtesy of Dennis Williams

  11. Source Water Assessment • Required by CDPH for all water supplies, including surface waters and groundwaters • Must include: • A delineation of the area around a drinking water source through which contaminants might move and reach that drinking water supply; • An inventory of possible contaminating activities (PCAs) that might lead to the release of microbiological or chemical contaminants within the delineated area; • Adetermination of the PCAs to which the drinking water source is most vulnerable

  12. Watershed Sanitary Surveys • Similar requirements to SWA, however, includes control measures for identified risks • Required for all surface waters and GWUDI • Identify potential sources of contamination • Characterize quality of source water • Identify control measures for potential contaminants • Duration of testing not specifically identified, but typically 1 to 2 years is minimum • Must be updated every 5 years

  13. Pathogen Removal Requirements • Results of SWA and WSS used to determine treatment requirements • Non-Impaired: total coliform < 1,000 MPN/100 mL • 2-log Cryptosporidium • 3-log Giardia • 4-log virus • Impaired: TC > 1,000 and < 10,000 MPN/100 mL requires 1-log additional for each • Highly Impaired: TC > 10,000 MPN/100 mL requires 2-log additional • Additional Cryptosporidium requirements may be needed based on LT2 monitoring

  14. Additional Monitoring for Cryptosporidium • LT2 requires 2 years of Cryptosporidium monitoring for systems with > 10,000 connections • Bin classification determined by initial water quality monitoring • Treatment requirements based on bin classification

  15. Defining Watershed in Santa Cruz • Terrestrial watershed of rivers and creeks in vicinity • Near shore area around intake extending 1.5 miles from coast and 2 miles along coastline • Potential contamination from: • Wastewater discharges to bay • Hazardous materials spill • Marine mammals and birds • Recreational boating and commercial fishing • Harbor dredging and disposal of dredge material • Large commercial vessels • Cruise ships • Harmful algal blooms Courtesy of Archibald Consulting

  16. Santa Cruz Water Quality Modeling • Modeling used to identify risk of contamination from potential sources • Low risk identified

  17. Santa Cruz WQ Monitoring • Two years of monitoring potential water quality risks • Total and fecal coliforms spiked during rain events • Max TC 214 MPN/100 mL (avg 13) • Max FC 44 MPN/100 mL (avg 3) • Two Giardia detections at 0.1 cycts/L • Avg 0.009 cycsts/L • No Cryptosporidium detected

  18. MF RO UV Treatment to Achieve Pathogen Goals • Open intakes will employ some type of pre-filtration • Pathogen reduction can be met for any classification with filters + RO + chlorine • Subsurface intakes may require UV if considered GWUDI • UV credit must exceed 3-log unless bank filtration credit achieved Cl2

  19. Conclusions • SDWA did not envision the ocean as a drinking water source, making it challenging to adapt regulations for unique risks • Type of intake could have an impact on the source water determination, but most subsurface intakes still considered GWUDI • While traditional microbial risks in seawater are low, they do exist, requiring monitoring and treatment to ensure safe drinking water supply is maintained

  20. Questions?

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