Washington State’s Turbidity Verification Project

Inspired by an AWOP data integrity workshop in October 2013, regional office field staff from the Washington State Office of Drinking Water recently completed a turbidity data verification project.  We took the original AWOP workshop, which was a day-long effort involving three teams, and scaled it down to a 2 to 3 hour field visit with a team of two staff.  Over a period of about one year, we visited all 25 rapid rate filtration plants in our northwest region.   We found deficiencies in all 25 plants that could or did affect the accuracy of the turbidity data reported to the DOH.


Prior to each field visit, we contacted the lead operator by phone or email to schedule a convenient date.  We explained the background and purpose of what we were doing and were careful to emphasize that this was not a regulatory compliance activity.  We used the following language in communicating with utilities:

“We are working on a turbidity verification project, with the goal of improving the integrity/reliability of the turbidity data that gets reported to DOH.  The project grew out of a EPA training on data integrity that was done at the Anacortes filter plant last October. We are looking at the turbidimeter/controller settings to gain an understanding of industry practices and possible areas for increased data integrity.”

Prior to each visit, we asked the operator to supply the make and model of each on-line turbidimeter and controller, so we could review the equipment manuals ahead of time.  We also retrieved a recent monthly operations report to bring along.

Field Visit/Data Collection

We started each visit explaining again the background of why we were there.  We then interviewed the operator(s) about turbidimeter setup and maintenance practices at their plant (see the operator interview sheet: TVP Operator Interview Questions).

After the interview we toured the plant and inspected each on-line turbidimeter.  All of our plants used HACH equipment, so we structured our data sheet around the most common configuration:  HACH 1720E with an SC100 or 200 controller.  Since many operators were not familiar with the instrument setup screens on their equipment, we found it useful to set up the data sheet to match the menu screens in the equipment.

HACH 1720E SC100 Turbidity Settings

We ended each visit with a review of the monthly operations report.  We found it worked best to pick a random day and ask the operator to retrieve the data from that day and show us how the four hour readings and the maximum daily reading were extracted from the data.

For the field visit we found a team of two was ideal:  with one person you have trouble capturing the information; with too many people the dynamics of your group dominates the discussion and the interaction with the operator is not as effective.

Documentation and Followup

We followed up each visit with a one page summary including recommendations for changes.  This was emailed to the operator within a week of our visit.

Turbidity Verify Project Form

Example Data Record Sheet

Project Followup

During the project we uncovered one case of data falsification, six systems that had non-functional or inaccurate data recording and thirteen systems that were not correctly reporting daily turbidity values.  We are following up with each of these systems to correct the problems identified.  Recognizing that we needed better written guidance for turbidimeter setup and turbidity reporting, we worked with our other two regional offices to develop consistent guidelines.

Turbidity Monitoring Guidelines NWRO

We are currently working to communicate these to operators through our Water Tap newsletter, and local operator training events.   Staff in our other regional offices are working to extend the project to rapid rate plants throughout the state.

Nancy Feagin, PE
Regional Engineer
Washington State Department of Health

Steve Deem, PE
Regional Engineer
Washington State Department of Health