Buckhorn Disinfection Byproducts / Backwash Disposal Project Board of Directors Meeting June 14, 2012

 Project Purpose and Issues  Backwash Management Strategies  DBP Reduction Alts and Recommendations  Recommended Phasing Plan Presentation Outline

 Project Purpose:  Assure Compliance with Stage 2 Disinfection Byproduct (DBP) Rule (a) & Develop An Integrated Backwash Management Strategy  Key Project Issues:  Elevated DBPs in the Buckhorn WTP Distribution System  Insufficient Pond 7 Storage Capacity for Backwash Waste Water Disposal Project Purpose and Issues (a) Effective October 1, 2013.

1.Expand Pond 7 to Contain 100-Yr Storm Event per WDR 2.Remove Solids at WTP to allow Recycle to WTP and/or Discharge Treated Backwash Water (BWW) to Pond 7 a)No WDR Required 3.Select Best Long-Term and Most Cost Effective Backwash Water Management Strategy Backwash Water Management Strategies for the Buckhorn WTP

Comparison of Solids Removal Alternatives Alternative Comparison Criteria (Score 1 to 5, 5 = best) Score Regulatory Construction Cost Applicability ParticulateChemical ComplianceRemovalCompatibility 1. Bag Filter w / Recycle3 5 ($255k) Bag Filter w / Discharge2 1 ($760k – $910k) Mech. Dewatering w / Recycle3 3 ($525k) Mechanical Dewatering w / Discharge2 2 ($660k) Conventional Drying Beds3 1 ($1,525k) (site constraints) 6. Proprietary Drying Beds5 4 ($355k) Reuse Old Plant (Conv. Drying Beds)3 1 ($1,515k) Leachfields1 5 ($200k) Micro Screen3 2 ($595k – $900k) Expand Pond4 3 ($500k - $650k)35520

Proposed Flow Schematic

Potential Site Layout Recommended Deskins TM System (Solids Removal and Dewatering)

Stage 2 DBR Rule Compliance Historical TTHM/HAA5 Results

 TOC Removal  Coagulation/Filtration  Adsorption  Oxidation  Reduce Chlorine Dose  Maintain Disinfection CT  Maintain Residual Disinfectant throughout System  Distribution System Modifications  Reduce Water Age  Tank Materials DBP Removal Strategies

Buckhorn WTP Distribution System DBP Sample Location

Comparison of DBP Reduction Alternatives DBP Reduction Alternative Capital Cost (1-5, 5 = Lowest) Operating Cost (1-5, 5 = Lowest) DBP Reduction (1-5, 5 = Greatest) Complexity (1-5, 5 = Simplest) Total Score TOC REMOVAL Chlorine Dioxide 2 ($180,000) 1 ($30,000/yr) ACH 4 ($25,000) 3 ($20,000/yr) Ferric Chloride 3 ($45,000) 2 ($25,000/yr) REDUCE CHLORINE RESIDUAL Clearwell Baffling/ Chlorine Booster Stations 1 ($160,000) 3 ($20,000/yr) pH Adjustment Location 4 ($20,000) 5 ($0/yr) Reduce CT Provided 5 ($0) 5 ($0/yr) DISTRIBUTION SYSTEM MODIFICATIONS Tank Mixing 3 ($175,000) 5 ($0/yr) 24 14

ACH DBP Reduction

Recommended Phasing Plan Goal: ACH feed system operational Summer 2013; highest DBP concentrations have historically occurred during summer season a Step / ActivityEst. Construction Cost ($) JJASONDJFMAM 1. Solids Removal Project355,000 DesignBConstruct & Startup 2. Full Scale Testing to Minimize Chlorine Dose 0b0b 3. Tank A Modifications50,000 DBConstruct 4. ACH Improvements25,000 DBC & SU Total Est. Construct Cost430,000 a First set of Stage 2 DBP compliance testing to be conducted prior to October 1, 2013 b Testing conducted by Agency operators and staff

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