Overview

CT calculations should be completed daily including weekend and/or Holiday rounds. You are calculating the CT time for the previous day. You can enter the required info onto the Draft copy located to the left of the SCADA computer or at Z:\Drinking Water Plant\Monthly Reports and selecting the Month and Year you wish to enter. This is to be completed daily so that the DRC and/or Department Manager can be contacted if we failed to meet the required CT and to begin public notification requirements if needed.

Gathering Data and Entering Data on the OHA spreadsheet

For the Minimum Cl2 Residual at the 1^st User (C) you will need to select the Historical Tend Tab on the HMI, Click the Browse button at the top right of the page, scroll through and right click on the “PCP.W_RES_CL2_SCALED” text, then click on the OK button. This will bring up the trend for that analyzer. You can move the trend by selecting the “Scroll Left” or “Scroll Right” buttons on the page or also by entering in the Day you wish to see in the text box at the bottom of the page, example – “July 4 12:00 AM” , then click on the Chart Start Time button. You will now see the trend for the complete 24 hrs. Move the scroll bar to see and document the lowest reading of that day.

Contact Time (T) is 90 minutes per Tracer Study on Record.

Actual CT is C X T

Temp can be taken from the Turb/Temp/pH Daily rounds sheet from the previous day (Treated) or if using the online temperature probe, take the temp reading during the Peak Hourly flow period.

pH can be taken from the Turb/Temp/pH Daily Rounds sheet from the previous day (Treated) or if using the online pH meter use the pH reading during the Peak Hourly flow period.

The Required CT will be calculated automatically if entered into the OHA Excel spreadsheet noted above, otherwise you can use the CT Values from the Quick sheets provided by OHA.

CT Met? Yes or No. Yes if the Actual CT is greater than or equal to the Required CT. Contact DRC and/or Operations Manager immediately if the answer is NO.

Consult SOP #15 at Z:\Drinking Water Plant\WTP O & M manual\Appendix F – SOPs for a more detailed explanation of State Reporting information. The DRC will verify the CT Calculations before submitting the Report.

Please consult with the OAR’s from Oregon Drinking Water Rules for the most up-to-date process.