Building a Better Community

May 11, 2005

About the author: Marcia Kinley is a marketing services manager for Marsh-McBirney, Inc. She can be reached at 301/874-5599 or by e-mail at [email protected].

Kennewick is known as one of Washington state’s most progressive cities. Located on the banks of the Columbia River in the wine-growing region of the state, the city is home to approximately 58,000 residents. Recently celebrating their centennial anniversary, Kennewick is a community on the move. Anticipated population increases in this scenic, family-friendly, region has city planners on their toes in an effort to remain ahead of necessary infrastructure improvements.

Integral to Kennewick’s growth plan is the modification of the city’s current sewer system. Kennewick Wastewater Plant crews maintain 15 sewage lift stations through the collection system. Thorough and accurate monitoring of wastewater flows will guide the planners as they update their comprehensive plan and flow models.

Tim Richman, project engineer for the city of Kennewick stated, “flow data is needed to update our comprehensive sewer plan as well as our sewer models. We are looking at trends for increased demands for our current system so we can get an idea of how long it will be before we need to make major improvements.”

The city had previously purchased three flowmeters with submerged-style sensors. The meters were used on a rotational basis to monitor sewer system flows.

“We only had enough flowmeters to monitor each site for about two weeks twice a year and that wasn’t enough time to get a good shot at what the performance was of each line,” Richman added.

Opportunities to collect flow data at each monitoring site was further limited due to submerged sensors that would foul with debris during the limited data collection periods, unbeknownst to public works personnel. The loss of valuable flow data due to fouled sensors was becoming a frequent occurrence.

With a desire to remain abreast of needed sewer system modifications during the city’s current growth juncture, a decision was made to purchase updated flowmeters. It was the hope of city personnel to procure meters that did not require frequent site visits for maintenance due to fouled flow sensors.

Working with Marsh-McBirney’s local representative, Bainbridge & Associates, as well as the consulting firm of Anderson Perry & Associates, Inc., a demonstration of the Marsh-McBirney Flo-Dar Flowmeter was scheduled and performed.

According to Richman, city personnel had seen the meter at several trade shows and seminars and really liked the Flo-Dar technology, especially the fact that the sensor was not in the flow stream.

This particular flowmeter utilizes advanced radar technology that can monitor flows from above the fluid, eliminating the maintenance headaches associated with submerged sensors. Flo-Dar combines advanced Digital Doppler Radar velocity sensing technology with ultrasonic pulse echo level sensing to remotely measure open channel flow.

The flowmeter’s easy installation requires no manhole entry and the sensor can be installed and/or removed from street level. With this model flowmeter, costs associated with confined space entry manpower and equipment can likely be eliminated.

Flowmeter operation

Flo-Dar transmits a digital Doppler radar beam that interacts with the fluid and reflects back signals at a different frequency than that which was transmitted. These reflected signals are compared with the transmitted frequency.

The resulting frequency shift provides an accurate measure of the velocity and the direction of the flow. Accordingly, the level is detected by ultrasonic pulse echo.

Flow is then calculated based on the Continuity Equation: Q = V x A, where Q = flow, V = average velocity and A = area.

The flowmeter’s sensor is mounted above the flow utilizing either a temporary or permanent sensor mount. Once the sensor is installed above the flow it can be easily removed or reinstalled from street-level using a sensor installation/retrieval tool without the need for confined space entry and its associated costs.

“We purchased ten Flo-Dar units from Marsh-McBirney,” said Richman. “There were two major reasons why we chose the Flo-Dar’s. One reason was the ease of installation and the fact that there really wasn’t much as far as maintenance that we had to do on them. They are pretty self-contained and there’s not a lot the operator has to do except read them on a monthly basis and take a look at the data.”

“Secondly, it was a safety issue for our personnel,” he added. “Now, we don’t have to go down into the manholes. We’ve got the sensor removal pole in case we do need to pull them out. It now takes a lot less time to take the readings and keep the meters maintained simply because we don’t have to spend the time to gear up for confined space entry. We also purchased a temporary mount (jack-bar style) that we can use if we want to monitor a particular problem area or look at something in particular.”

The units have been installed for over two years now. Nine of the units are semi-permanently mounted at the base of each of the city’s nine major drainage basins.

“We have been using them to collect flow data that will be compiled for use in our sewer comprehensive plan,” Richman added. “The tenth meter is currently being used as a spare.”

Stored flow data is downloaded monthly via a laptop computer that is taken to the monitoring site. Reports are generated utilizing Marsh-McBirney’s Flo-Ware software. “When we download the data, we look at the graphs and make sure there are no problems and we verify that it looks accurate.” he added.

Flo-Ware is an easy-to-use Windows-based data management software tool that allows users to efficiently manage their flowmeter data. Collected flow data is utilized to evaluate if the sewer system is flowing properly as well as evaluating the impact of upstream lift stations on flow in the pipes.

Regarding the performance and accuracy of the meters, Richman commented, “we have been real pleased with the performance. As far as the accuracy, it has been pretty accurate. We have a velocity meter that we check them against every once in a while. The meters have been doing a fine job.”

A recent case study written by the city on their wastewater lift station and flow logging project stated, “these improvements have made operation and maintenance of the city’s sewage collection system safer, more manageable and more reliable.”

The insightfulness of city personnel in selecting flowmeters that utilize cutting-edge technology will serve them well as they move forward in their goal of “Building a Better Community.”

About the Author

Marcia Kinley

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