California Utility Uses Creativity to Combat Manhole Infiltration

A California sanitary district makes an agreement with Oatey to develop a manhole sealant product

California Utility Uses Creativity to Combat Manhole Infiltration

Truckee Sanitary District has a standard operating procedure in which any manhole that is removed has a bead of Hercules Shutout applied to the lip before the cover is replaced. This small effort has already sealed a third of the system’s manholes from infiltration.

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Living in paradise is demanding for anyone charged with keeping it unpolluted. That’s the responsibility given to Blake Tresan, general manager and chief engineer of the Truckee (California) Sanitary District.

Truckee is located next to a river of the same name, which flows from nearby Lake Tahoe. The town sits nearly 6,000 above sea level in the Sierra Nevada Mountains. This combination of lake waters and mountain slopes in a pristine California setting lures weekend tourists year-round. They trek there to visit Mother Nature in all her paradisiacal glory — hundreds of thousands of them every year.

That is a lot of people, which translates into a lot of wastewater. The sanitary district’s mission is to handle it without making a big deal of it. Out of sight, out of mind, just move it along, nothing to see here, folks. Go enjoy the scenery.

“Handling wastewater without incident is business as usual, but we take it very seriously because of the environment we have up here,” says Tresan. “The main economy of our community is tourism — environmental tourism. Our job is to keep our lakes and rivers and mountains clean and uncontaminated. We work hard at it every day.”

Tresan has been working at it for 20 years, in fact, the last eight as general manager. How does he account for such a long tenure? “Great job. Great people. Great location,” he says.

Trouble in paradise

However, like many other wastewater systems, Truckee Sanitary District battles inflow and infiltration. Yes, there are leaks in paradise!

After all, we are talking about one of the oldest sewer systems in California, dating back more than a century. It operates in challenging terrain, with 44 lift stations moving water across a system with an elevation change of 1,600 feet. The area receives 200 to 300 inches of snow each year with attendant freeze-thaw problems.

The system’s legacy pipe has all been replaced, and the oldest of the infrastructure — including some 24-inch segments — was laid in the ground in the 1960s. A flurry of subdivision conversions from septic tanks to sewer occurred in the 1970s and 1980s, but most of the system is 6-inch stock put in place since the 1990s.

“We’ve done a lot of pipe lining,” Tresan says. “So some of the older and bigger pipe is just host pipe, having been lined.” The type of pipe varies, reflecting the different eras in which it was installed. The mix includes asbestos cement and vitreous clay, with the bulk of it being PVC.

So, what’s the cause of the I&I? Tresan calls that the million-dollar question. “We are still dealing with flow from connections we don’t know about. Sump pumps. Basement drains that are flowing into the system and are almost impossible to find.”

Sewer laterals on private property are being systematically checked, pressure-tested, whenever a property changes hands to determine if the laterals are letting in groundwater. About 500 properties are tested every year.

The district also is aggressively examining laterals on the district’s side of property lines using a CUES camera. The camera moves on tracks along a mainline and then launches a secondary camera called a lateral and mainline probe. The LAMP unit can move up to a hundred feet into a lateral.

“It’s a time-consuming process, but we’re getting data on the lower portion of laterals,” Tresan says. “We actually have found a lot more damage in the laterals than we expected, much of it pipe that has been inadvertently damaged by crews working on other utilities.” The damaged pipe is found across the district.

Truckee Sanitary District tries to video inspect the entire system every four years. While that seems a fairly long interval between visual inspections, Tresan says the schedule has proven effective. “We have a couple of hot spots we visit more frequently to keep an eye on tree roots, but the four-year program seems to find defects before they become problematic.”

Creative solutions

The district hit its stride as an I&I battler when it began concentrating on its 4,500 manholes. That came about after some heavy rainfall in 2017 that had Federal Emergency Management Agency implications. The storms forced the district to contract with tanker-truck operators to bypass excess water from lift stations so wastewater wouldn’t overflow them.

Because the overflow threat coincided with the rain, district engineers were confident they faced a surface water issue rather than infiltrating groundwater. That narrowed the problem to manholes and/or lateral clean-outs. In response, field crews did some major smoke-testing. Uncapped lateral clean-outs were capped. Still, the infiltration continued.

Because the district had long used chimney seals, O-rings under covers and pick holes that didn’t penetrate the covers, the operating assumption was that water wasn’t entering there. Yet reputed “watertight” solutions weren’t solving the problem.

“We decided to ring a manhole with sandbags and build up water pressure above the manhole,” Tresan says. With a camera recording what was happening beneath the cover, the maintenance staff discovered steady leakage into the manhole from the pooled water above. A larger diameter O-ring was inserted, but that didn’t stem the deluge.

“Then we had an aha! moment,” Tresan recalls. “One of the field guys said, ‘Boy, if we could only put down some kind of jelly to seal it.’ And we thought that was a good idea.”

Back in the maintenance shop, crew members had a tub of Duck Butter, which is a lubricant for pipe joints. A bead of Duck Butter was applied between a manhole lip and the cover. Once more, water was pooled above the test manhole. This time, voilá, No leaking.

“Not a drop of water got through and we had the water sitting on it for a couple of days. It was an easy solution,” Tresan says. It was not, however, a permanent one. After a few months of testing, district crew members saw inflow return after the water-soluble Duck Butter either washed away or evaporated.

So, the district got into the product development business. Online, they found a petroleum pipe-thread compound called Pro Dope, also manufactured by Oatey. It seemed promising and was applied. Satisfied that they had a workable idea, the district went to Oatey and suggested that it formulate a lubricant-sealant specifically for sewer manhole covers. Oatey lab people bought into the idea and earlier this year the company introduced its Hercules Shutout product.

A worker with the Truckee Sanitary District uses a caulking gun to apply Hercules Shutout lubricant and sealant to a manhole lip.
A worker with the Truckee Sanitary District uses a caulking gun to apply Hercules Shutout lubricant and sealant to a manhole lip.

“We are all proud of having come up with that,” Tresan says. “It was sort of a case of smacking your forehead and saying, ‘Why didn’t someone think of that before?’”

An auxiliary benefit of applying Shutout is that manhole covers are easier to remove. That’s because the product not only seals the manhole components against water passage but also lubricates them against corrosive binding. This results in fewer strained backs and shoulders from trying to remove covers.

That is not an incidental concern. Tresan contacted an insurance organization and learned that in the previous two years, 25 workers’ compensation claims had been filed from injury while removing a stuck cover — with an average payout of $15,000.

Truckee Sanitary District is expected to earn between $10,000 and $100,000 during its five-year royalty agreement with Oatey. Tresan says all royalties will help fund scholarships for community members. 

The district’s novel and successful response to an I&I issue was a team effort, according to the general manager. “It was only through feedback from field staff that we came up with a cheap and easy solution to the problem. Two dollars in materials and it will work on any manhole.”

Staff engineer Raymond Brown echoes Tresan in giving credit to the Truckee Sanitary team. “The big part of our success as an organization is the core values we’re trying to implement that make sure staff members are heard and responded to. Keeping staff feeling good about their jobs makes a big difference in productivity.”

Inspecting new installations

Aside from coming up with a whole new water-resistant lubricant-seal for manholes, what else is Truckee Sanitary District doing to combat I&I? One significant initiative is fostering a proactive relationship with property developers.

“If the pipe is installed correctly, we can avoid a lot of problems over the life of that product,” Tresan says. Consequently, the district has three employees dedicated to inspecting new installations. The supervision is not pro forma. District personnel peer into open trenches to confirm the pipe is bedded well and is on grade. They revisit each new installation before a 12-month warranty runs out to see if the function of the infrastructure has been degraded in any way.

With the new manhole cover product now available, the district has established a standard operating procedure in which any manhole that is removed has Hercules Shutout applied before the cover is replaced. This systematic application of Shutout during routine manhole work already has sealed a third of the system’s manholes.

The impact of the Shutout compound on I&I still is being evaluated. Tresan says FEMA-level storms historically have raised wastewater flow in the district to 6 mgd or higher from the average of 2 mgd. The next big storm should be telling. “Because of what we’re doing, I feel pretty good about our chances of significantly reducing I&I. I would like to think we are making progress.”

While he believes the Hercules Shutout solution is going to help the district, he has concerns about other sewer agencies. At a conference in the spring, Tresan asked the audience of professionals how many of them had manhole covers in their systems with penetrating holes for picks or for ventilation. “Just about everyone in the room raised a hand. To me, their I&I problem is obvious. If they’ll systematically replace those covers, I believe they’ll see a dramatic decrease in their I&I.”


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