Nov 25, 2019

Boom & Rake Retrofit

This article originally appeared in the Water & Wastes Digest November 2019 issue as "Backup, No More"

Backup, no more

Before a series of upgrades totaling $27 million over five years at the city of Washington wastewater treatment plant in Indiana, even the smallest amount of rainfall would cause an overflow. $27 million is a significant sum of money of course, but as any municipal plant superintendent will tell you, funding is a long and complicated process.

Prior to the installation in 2012 of a fixed bar screen, Superintendent Scott Rainey and his team at the Washington Wastewater Treatment Plant (WWTP) could be forgiven for any choice words uttered as they painstakingly pulled out large debris from a fixed overflow weir installed in 1988 that had been overwhelmed during storm events.

With a collection system comprised of combined sanitary and storm sewers with four combined sewer overflows (CSOs), treatment had sometimes been as complicated as funding, but again, learning to be patient, resilient and resourceful is part of responsible wastewater treatment plant life.

“Our old screen just kept on blinding,” Rainey, who has served the city of Washington’s WWTP for the past 16 years, said. “Backups were all too regular. We knew and we wanted to take action, as of course did the state’s Department of Environmental Management, but our hands were tied until we had funding in place. In the meantime, we simply had to get on with it. With talk of a fine hanging over our heads, this wasn’t always easy.”

Finally, when approval was given to go ahead with a new screen, to the tune of between $1 million to $1.2 million, Rainey set about researching the best possible solution, speaking to operators across the U.S. He also sought advice from his trusted contact, Ken Sobbe at FACO Waterworks in Indianapolis, who had helped supply the plant, which opened in 1952, with equipment on many occasions. 

“Serving a small community [12,000], we all have several hats to wear,” Rainey added, “so getting away isn’t easy. But I attended trade shows, and trust me, I listened to all sorts of solutions that were put forward. I knew that while we certainly needed something robust and of good quality to cope with heavy debris, we didn’t necessarily need a full-blown mechanical screen, just for the sake of it. We’re not trying to reinvent the wheel.”

Considering Alternatives

A key factor in the decision-making process was the possibility for retrofit. During the previous upgrades, a forward-thinking approach saw the main storage tank designed, so it could be retrofitted if required—with only slight modifications. Rainey also consulted with the treatment plant’s engineer of record, Midwestern Engineers, which developed the idea of integrating an automated rake system to clean and clear the bar screen during storm events.

“Attending the WEFTEC show was well worth the time in the end, and when I showed my engineers the Hydronic T screening system from Lakeside Equipment Corp., they liked it immediately,” Rainey added. “Seeing a video of the Hydronic T pull a log out of a creek was very impressive and when I spoke to other operators, they, like Ken Sobbe, confirmed what high quality and precisely engineered equipment it is.”

While he and his team agreed the plant could purchase something bigger and more expensive, they knew the economical solution of using existing infrastructure would be more effective, assuming the mechanical transition would be simple to execute.

The hydraulically operated telescoping boom and rake mechanism uses hydraulic cylinders to pivot the boom to extend and retract the it and the rake for depths up to 50 ft.
The hydraulically operated telescoping boom and rake mechanism uses hydraulic cylinders to pivot the boom to extend and retract the it and the rake for depths up to 50 ft.

Timing, Engineering & Delivery

As those saddled with funding issues or ultimately benefiting from it know, the next obstacle to negotiate, when all has been agreed upon, is timing. Twelve months may at first sound like a long time, but achieving everything from scratch, including research and design, in just three months was a considerable feat. Together with a skilled contractor, the goal-oriented and product delivery-driven team is what enabled the project to stay on budget and finish ahead of the U.S. EPA mandate.

The contractor in this case was Bowen Eng. Corp., established in 1967 in Indianapolis, Ind. Bowen engineers were confident its joint effort would deliver the right results while sticking to the original cost estimates for
the project.

“We wanted to deliver a really high-quality product while always challenging ourselves as to how can we do something better for less money,” said Sam Hill, project manager for Bowen Eng. “The city of Washington is a long-time customer of ours, so by knowing and understanding their needs, we feel that we are working with them as a team rather than as separate entities. 

“The storm water combined sewer overflow tank is intended to be a storage tank during major rain events to prevent sewage from discharging into local waterways, but with a clogged screen, the sewer and storm water is diverted into the waterway, in effect making the tank totally ineffective. Retrofitting the existing system with Lakeside’s Hydronic T Rake brings the tank into play as it should, and in doing so, cleans up the area’s waterways. Most importantly, it helps to prevent the city from being fined large sums of money by government environmental agencies for diverting flow.” 

Installing the Boom & Rake

The Lakeside Hydronic T is a hydraulically operated telescoping boom and rake mechanism that utilizes hydraulic cylinders to pivot the boom and to extend and retract the boom and rake for depths up to 50 ft. A hydraulic power pack provides large lifting capacities, and it has all of its components accessible above the channel for ease
of maintenance. 

The screen’s flexible design saves money when designing indoor headworks systems with deep channels, low headroom or retrofit needs. In Washington, the system features a double 12-ft-wide telescoping design to rapidly remove the anticipated debris from storm events. Unlike the previous operation, a level sensor in the channel will intelligently switch the screen on until the water elevation returns to the required level.

“We weren’t trying to cut any corners,” Rainey said, “But from a potential outlay of up to $1.2 million, the big plus of having a retrofit was that we spent $750,000 instead. We do want our bang for the buck.”

The very nature of retrofitting existing equipment and integrating it with new equipment can often present many unforeseen challenges and issues, but apart from a couple of very minor points, the installation of the new Lakeside rake went very smooth according to Hill.

“Perhaps it seems a petty, and maybe obvious thing to say, but the equipment that was shipped matched the drawings! Often this is a challenge when modifications to equipment don’t match current drawings. Hugely frustrating and time-consuming,” Hill said.  “From main structural members to the smaller items like hydraulic tubing, all of the prefabricated parts came together very well. The shipping package from Lakeside was engineered, so the equipment was pre-assembled to the maximum allowable prior to shipping, which always helps the owner cut down on site cost.”

Backups with the old screen were regular problems for Washington, Ind., so when funds were released to upgrade the equipment, operators at the facility saw it as relief.
Backups with the old screen were regular problems for Washington, Ind., so when funds were released to upgrade the equipment, operators at the facility saw it as relief.

Hill said the equipment has worked as intended, and Sobbe agreed.

“We all knew that it would be a tight call, but I have to say that it came together very nicely indeed, with the new screen doing everything we said it would,” Sobbe, who has attended 41 WEFTECs, said. “I’ve seen the Hydronic T put through its paces, and it’s a great example of quality engineering.”

Rainey said he and his team had to change the angle of elevation and adjust hydraulic pressures for heavy debris to get settings just right. But he said he expected those kinds of tweaks as part of the installation process.

“You have to expect a bit of fine tuning for the specific needs of your own plant. Overall, everyone is very pleased with it,” Rainey said. “Throughout the process, Lakeside did a very good job. They turned things round quickly but always with quality. And despite the delay in getting the project released, which initially would have meant project completion after the deadline for crucial compliance purposes, the tenacity of Bowen Eng., together with us all as a team, saw construction completed ahead of schedule at no extra cost to the city. The option to retrofit has proved an excellent fit for what we needed
here.” 

About the author

Chris French is a freelance writer on water, environment and renewable energy. French can be reached at [email protected].

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