Clearlake Oaks CWD Tracer Study Tank Farm Summary

Tracer study conducted on a tank farm with 19 poly tanks operated in series using liquid fluoride as tracer. Sampling at three stations to determine fluoride dose. Configurations, baffling factor, and HRT details provided. Transmission line volume and flow data summarized.

• Tracer Study
• Tank Farm
• Liquid Fluoride
• Baffling Factor
• Transmission Line

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1. Clearlake Oaks CWD CA1710001 Tracer Study Tank Farm Feb 10, 2022 By Guy Schott, P.E

2. Table of Contents Clearwell Design Specifications and Tracer Sampling Points Summary of Tracer Results and Procedures Tracer Injection Point Recorded Tracer Data (Tables) Graphs: Modified Step-Dose Curves for sample points 2 and 3 And Normalized Modified Step-Dose Curve to F-Curve for sample pts 2 & 3 Purpose of a Tracer Test Disinfection Exposure Time of Fluid in Vessel for Determining Ct10 Ct10Value Baffling Factor (BF), Definition Tracer Test Method (Modified Step-Dose) Method of Analysis and Equipment

3. Pipeline & Tank Design Specifications Pipe volume to Tank 1: 1,350 gal Pipe volume from Tank 4 - Tank 5: 470 gal Pipe volume from Tank 19 to sample point: 915 gallons Operating Tank 1 to Tank 5: 10-ft Operating Tanks 6 - 19: 9.5-ft Tank Diameters: 12-ft (846 gal/ft) Pipes connected to Tanks: 10.3 inner Diameter Total operating volume end of Tank 5: 44,120 gallons Total operating volume from injection point to post Tank 19 sampling point: 156,638 gallons T4 T1 T2 T3 Tracer (F) T5 T7 T6 T8 T9 T10 T12 T11 615 gpm Tracer (F) Tracer (F) T19 T18 T17 T16 T15 T14 T13 Treatment Plant Tracer (F) FM 640 gpm

4. Summary of Tracer Procedures Tracer study was conducted on the temporary installed tank farm that consist of 19 x 10,000-gallon poly tanks operated in series. Liquid fluoride was used as the tracer that was injected at the chlorine injection point upstream of the tank farm. Sampling were conducted at three stations Station 1: Inlet to Tank 1 to determine fluoride dose (mg/L) Station 2: Outlet of Tank 5 Station 3: Downstream of Tank 19 and flow meter near high lift pump Tank 5 exit flow was 615 gpm Tank 19 exit flow was 640 gpm

5. Pipeline & Tanks 1- 5 Configurations Baffling Factor: 0.54 t10 = 39 minutes HRT: 72 minutes T5 T4 T1 T2 T3 Tracer (F) 615 gpm Tracer (F) 615 gpm Pipe volume to Tank 1: 1,350 gal Pipe volume from Tank 4 - Tank 5: 470 gal Operating Tank 1 to Tank 5: 10-ft Tank Diameters: 12-ft (846 gal/ft) Pipes connected to Tanks: 10.3 inner Diameter Total operating volume end of Tank 5: 44,120 gallons Treatment Plant Tracer (F)

6. Tracer Test Result Summary Transmission Line & Tanks 1 to 5 Volume of Transmission Line + Tanks: 44,120 gallons Flow thru Tank 1 - 5: 615 gpm HRT: 72 minutes (44,120 gal/ 415 gpm) t10: 39 minutes Tanks 1 5 Baffling Factor (t10/HRT): 0.54 Modified Step-Dose Test Date: 2/10/22 Pipe volume from injection point to Tank 1: 1,350 gal Pipe volume from Tank 4 to Tank 5: 470 gal (~10.3-in Dia) Tanks 1 - 5 Operating Level: 10-ft Tank Diameter: 12-ft (846 gal/ft)

7. Tracer Test Result Summary Transmission Lines + all 19 Tanks Tank Diameter: 12-ft (846 gal/ft) Volume of Transmission Lines + Tanks: 156,638 gallons Exit Tank 19 Flow: 640 gpm HRT: 245 minutes (156,638 gal/ 640 gpm) t10: 150 minutes (minimum) Tanks 1 19 Baffling Factor (t10/HRT): >= 0.6 Note: tracer test wasn t run long enough to determined actual t10value. Modified Step-Dose Test Date: 2/10/22 Pipe volume from injection point to Tank 1: 1,350 gal Pipe volume from Tank 4 to Tank 5: 470 gal (~10.3-in Dia) Pipe volume from Tank 19 to high lift pumps: 915 gal (~10.3-in Dia) Tanks 1 - 5 operating level: 10-ft Tanks 6 19 operating level: 9.5-ft

9. Clearlake Oaks CWS Tracer and Fluoride injection location Tracer: H2SiF6, Fluoride (F) Feed pump capacity 17.2 gal/hr set at 50% during test Background Fluoride: 0.164 mg/L as F Measured dose: 1.86 mg/L as F (excluding background fluoride) Fluoride (tracer) was injected into a vault at chlorine injection point.

10. Feed Pump and Tracer Injection Fluoride chemical crock and pump Fluoride Injection Point (same location of post NaOCl)

11. Tank 1 Sample Pt. #1 To determine Fluoride dose F Dose: 1.88 mg/L

12. Tanks 2-4 Tank 1 Post Tank 19 Flow Meter

13. Tank 5 Sample Pt. #2 BF (t10/HRT): 0.54

14. Temporary Tank Farm (Tanks 5 19)

15. Post Tank 19 Sample Pt. #3 BF (t10/HRT): 0.6 Post Tank 19 Flow Meter

16. Tracer Fluoride Dose, Inlet to Tank 1, Table 1 Elapsed Time minutes 28 Elapsed Time minutes 69 Tracer Fluoride mg/L 1.82 Tracer Fluoride mg/L 1.89 Fluoride-Dose to Tank 1 2.50 Tracer Concentration (mg/L) 2.00 1.50 1.00 39 1.86 78 1.88 0.50 45 1.88 84 1.92 0.00 21 27 33 39 45 51 57 63 69 75 81 87 93 99 105 111 51 1.88 90 1.92 Time (minutes) 57 1.89 96 1.91 63 1.88 102 1.91

17. Tracer Dose and Background Residual Average background fluoride concentration: 0.164 mg/L as F Average steady-state measured fluoride concentration exiting pipeline and entering the first tank (steel): 2.046 mg/L as F Fluoride dose: 2.046 0.164 = 1.88 mg/L as F Results are based on tracer dose of 1.88 mg/L as F 10% of tracer dose is 0.188 mg/L as F

18. Elapsed Time, (t) min Sample Interval, min. Reactor Water Level, ft Reactor Exit Flow, gpm Operating Volume Gallons Weighted Avg Residence Time ( ), min Normalized Time t/ Measured Tracer, mg/L Adjusted Concentration, mg/L Tracer Results for Tanks 1 -5 Normalized Cadj/Co Sample # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 0.0 4.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0 31.0 32.0 33.0 34.0 35.0 36.0 37.0 38.0 39.0 40.0 41.0 42.0 43.0 44.0 45.0 46.0 47.0 48.0 49.0 50.0 55.0 60.0 65.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0 150.0 0 4 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5 5 5 5 10 10 10 10 10 10 10 10 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 615.0 - 0 0.000 0.056 0.112 0.125 0.139 0.153 0.167 0.181 0.195 0.209 0.223 0.237 0.251 0.265 0.279 0.293 0.307 0.321 0.335 0.348 0.362 0.376 0.390 0.404 0.418 0.432 0.446 0.460 0.474 0.488 0.502 0.516 0.530 0.5436 0.558 0.572 0.585 0.599 0.613 0.627 0.641 0.655 0.669 0.683 0.697 0.767 0.836 0.906 0.976 1.115 1.255 1.394 1.533 1.673 1.812 1.95 2.09 0.1640 0.1630 0.1640 0.1620 0.1660 0.1650 0.1610 0.1620 0.1610 0.1630 0.1650 0.1650 0.1660 0.1700 0.1720 0.1730 0.1740 0.1760 0.1780 0.1890 0.1920 0.2010 0.2030 0.2200 0.2450 0.2260 0.2540 0.2630 0.2620 0.2750 0.2890 0.3080 0.3170 0.3530 0.3580 0.3790 0.4000 0.4160 0.4150 0.4400 0.4840 0.48 0.50 0.52 0.56 0.60 0.85 0.92 1.06 1.26 1.42 1.47 1.62 1.72 1.81 1.87 1.92 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0020 0.0020 0.0030 0.0070 0.0090 0.0100 0.0110 0.0130 0.0150 0.0260 0.0290 0.0380 0.0400 0.0570 0.0820 0.0630 0.0910 0.1000 0.0990 0.112 0.126 0.145 0.154 0.190 0.195 0.216 0.237 0.253 0.25 0.28 0.32 0.32 0.33 0.36 0.39 0.44 0.68 0.75 0.90 1.10 1.26 1.31 1.46 1.56 1.65 1.71 1.76 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.002 0.004 0.00 0.01 0.01 0.007 0.008 0.01 0.02 0.02 0.02 0.03 0.04 0.034 0.049 0.053 0.053 0.06 0.07 0.08 0.082 0.101 0.104 0.12 0.13 0.13 0.13 0.15 0.17 0.17 0.18 0.19 0.21 0.23 0.36 0.40 0.48 0.58 0.67 0.70 0.78 0.83 0.88 0.91 0.94 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 42,300 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72

19. Step-Dose Curve Tanks 1 - 5 1.9 1.8 1.7 1.6 1.5 1.4 Tracer Concentration (mg/L) Dose: 1.88 mg/L 0.188 mg/L at t10 t10: 39 min HRT: 72 min BF: 0.54 (t10/HRT) 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 Time (minutes)

20. Normalized F-Curve- Tanks 1 - 5 1.00 0.90 0.80 0.70 Tracer Normalized 0.60 Baffling Factor (BF) = 0.54 0.50 0.40 0.30 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 t/HRT)

21. Elapsed Time, (t) min Sample Interval, min. Reactor Water Level, ft Reactor Exit Flow, gpm Operating Volume Gallons Weighted Avg Residence Time ( ), min Normalized Time t/ Measured Tracer, mg/L Adjusted Concentration, mg/L Normalized Cadj/Co Sample # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 0.0 10.0 15.0 20.0 25.0 30.0 33.0 36.0 39.0 42.0 45.0 48.0 51.0 54.0 57.0 60.0 63.0 66.0 69.0 72.0 75.0 78.0 81.0 84.0 87.0 90.0 93.0 96.0 99.0 102.0 105.0 108.0 111.0 114.0 120.0 123.0 126.0 132.0 138.0 144.0 147.0 150.0 0 10 5 5 5 5 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 6 3 3 6 6 6 3 3 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 640.0 - 0 0.000 0.041 0.061 0.082 0.102 0.123 0.135 0.147 0.159 0.172 0.184 0.196 0.208 0.221 0.233 0.245 0.257 0.270 0.282 0.294 0.306 0.319 0.331 0.343 0.355 0.368 0.380 0.392 0.404 0.417 0.429 0.441 0.454 0.466 0.490 0.503 0.515 0.539 0.564 0.588 0.601 0.613 0.16 0.164 0.158 0.158 0.159 0.159 0.159 0.159 0.160 0.160 0.161 0.160 0.159 0.158 0.158 0.159 0.157 0.161 0.157 0.158 0.159 0.160 0.161 0.173 0.164 0.161 0.159 0.161 0.166 0.161 0.161 0.161 0.159 0.160 0.164 0.164 0.164 0.169 0.179 0.182 0.192 0.191 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.009 0.019 0.022 0.032 0.031 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.005 0.010 0.012 0.017 0.02 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 156,638 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245 245

22. Step-Dose Curve, Tanks 1 - 19 0.035 0.030 0.025 Tracer Concentration (mg/L) 0.020 Baffling Factor (BF) >= 0.6 0.015 0.010 0.005 0.000 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Time (minutes)

23. Normalized F-Curve, Tanks 1 - 19 0.018 0.016 0.014 0.012 Normalized Concentration 0.010 Baffling Factor (BF) >= 0.6 0.008 0.006 0.004 0.002 0.000 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 t/HRT

24. Purpose of a Tracer Study To determine the hydraulic efficiency or disinfectant exposure time of water through one or more reactors. The addition of known quantities of a nonreactive chemical (tracer) is added in the form of a pulse (slug) or step-input. The time of travel or disinfectant exposure time through the reactor is related to: Flow rate Reactor water volume Water Depth Reactor configuration Hydraulic mixing

25. Disinfection Exposure Time of Fluid in Vessel for Determining Ct10 C is the disinfectant residual (mg/L) at the point of inactivation compliance. The disinfection exposure time of water used for Ct10 calculation is the time (t10) it takes for the first 10 percent of the water entering the reactor to exit the reactor. To determine this, a marker (nonreactive tracer) is introduced into the water and is monitored leaving the reactor. Example: 2.7 mg/L of tracer is continuously dose during testing; t10 is that time when 0.27 mg/L of tracer concentration (10% of dose) has exit the reactor.

26. Ct10 Value Log inactivation is based on the Delivered Dose, Ct10 C is the disinfectant residual (mg/L) t10 is the exposure or contact time (minutes) Multiply them: C t10= mg/L min (delivered dose to pathogens) The calculated Ct10 value is looked up in EPA Cttables to determine the log inactivation based on specific monitoring parameters (pH, disinfectant residual and temperature).

27. Baffling Factor (BF) Baffling factor or short-circuiting factor: Determined from tracer study or estimated BF = t10/ HRT from tracer study HRT (hydraulic residence time) = reactor volume divided by reactor flow Once the BF is determined, then it is applied to the operations of the reactor for determining the disinfectant exposure time. Example: Total Clearwell operating volume: 157,000 gallons Exit flow: 640 gpm (0.922 MGD) BF: 0.6, from tracer study Calculated contact or disinfection exposure time: 157,000 gal 640 gpm 0.6 = 147 minutes = t10

28. Test Method Modified Step-Dose Method It is a continue feed of tracer at constant rate and inlet plant flow throughout the duration of the test. The Step-Dose test has a duration of 3-4 HRT to achieve reactor outlet steady-state tracer concentration. The time t10 is determined when 10% of the tracer dose concentration has exist the reactor. The Modified Step-Dose test allows the test to be completed in less than 1 HRT by physical measurements of the tracer inlet flow and/or channel basin concentration.

29. Method of Analysis and Equipment Intellical Selective Electrode (ISE) HQ40d Portable ISE Multi-Parameter Meter Fluoride Ionic Strength Adjustor (ISA) Fluoride Standards (0.2 & 2.0 mg/L) 25 mL graduated cylinder Finnpipette F2 variable volume pipette, capacity 0.5 - 5 mL Electrode stirrer stand 50 mL beakers Stir Bar, Magnetic, Polygon ISEF121 Fluoride (F-) Ion

30. Contact Guy Schott, P.E. State Water Resources Control Board Division of Drinking Water Santa Rosa, CA Go to Tracer Test Results for review www.waterboards.ca.gov/drinking_water/programs/districts/mendocino_district.html Email: Guy Schott - Guy.Schott@waterboards.ca.gov Office Number: 707-576-2732