Ambitious Tunneling Project Saves Nature Preserve

Instead of tearing apart a wilderness area by trenching, a creative solution achieved lofty goals for the city of Clifton, New Jersey, when it set out to relocate a failing sewer line

Ambitious Tunneling Project Saves Nature Preserve

(Photo credit Jon Grove/Friends of Bonsal Preserve)

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It would have been easy to trench in a new gravity sewer line, replacing the failing pipe in the heart of New Jersey’s Alonzo F. Bonsal Preserve. It also would have devastated the state-designated wilderness area.

But there were few options, and the city of Clifton was ready to go ahead with trenching until an innovative engineer came up with a plan to relocate the pipe by tunneling underneath an area on the edge of the preserve.His big idea had a big problem, however. 

“This was a brilliant strategy, there was one problem with it. If you visualize the preserve, that part is uphill, and the current sewer was running with gravity, alongside a creek,” says Jonathan Grupper, a representative of the Friends of Bonsal Preserve group.

City officials didn’t want to install pump stations or use mechanical means, and a 40-foot incline stood between them and the new pipe’s destination.The solution was to drop a tunnel boring machine into a series of 20-by-50-foot pits about 35 feet deep.

“Everybody looked at me like I was this crazy person,” says Dominick Villano, former city engineer turned city manager. “Even when I pitched it to the engineering firm, although I worked for them at one point, they looked at me like ‘Are you out of your mind?’

 “The environmentalists loved it, because it was minimizing the disturbance, but honestly, they’d never seen anything like this before.”

A Much-Needed Solution

Villano’s idea came at a desperate time for the city and the Bonsal Preserve. The existing line, nearly 80 years old, followed a creek running through the preserve.

“That was pretty common when these sewers were installed, but with the Clean Water Act and so forth, we all started making sure we were addressing inflow and infiltration issues,” Villano says. “Being that it’s close to a creek, it was taking in a lot of extraneous flow.”

There was no access to manholes, except via a small road that ran overtop a 72-inch brick water tunnel owned by another utility. The weight limit on that path meant that the city of Clifton couldn’t even bring in cleaning equipment — even excessive vibration could endanger the water main.

Pipe displacement was also out of the question because of the proximity to the creek and water main. All of this meant no cleaning or maintenance, no relining, and no pipe bursting.

“Clifton was at a loss. They knew they couldn’t maintain the line and it was getting older,” Grupper says. “This was a game of Russian roulette that they were playing. Waiting, holding out hope that they could bide their time, but it snuck up on them.”

A major line break in 2008 forced the city’s hand. Just repairing that section left a scar in Bonsal Preserve that lingers today, as the city had to carve a new access road to reach the segment. 

“They put it in the category of a public health emergency, which entitled them to really decimate a stretch of the preserve,” Grupper says. “It was a disaster for the preserve, and it was an indication of what we could expect if they were to go through with their original plan of trenching the line.”

Villano’s entrance was remarkably fortuitous, as he joined the city as an engineer a matter of months after the disastrous break.

To prevent similar issues with access and I&I in the future, Villano suggested rerouting the pipe from the heart of the preserve to a less-impactful area skirting the edge of the property, using a trenchless AVN 1200 tunnel boring machine from Herrenknecht to limit the impact.

“Villano — who I consider the hero of this story — I can tell you that when he suggested it, there was a lot of resistance to it, because it was a wildly ambitious effort,” Grupper says.

Building Trust

Even more challenging than the topography was completing the project without upsetting the delicate balance of Bonsal Preserve — or its supporters.

Those fears were realized when an incident occurred last November, partway through the tunneling operation. 

“The boring head intercepted an active sewer, a tributary sewer that was coming in,” Villano says.

Wastewater leaked out into some of the wetlands in the preserve. Fortunately a hiker noticed it before too much damage had been done. 

“The way that we chose to deal with it is emblematic of the amount of trust that had been built. The knee-jerk reaction would have been to exploit this moment as an opportunity to lash out and to express our frustration,” Grupper says. “But the first call we made was not to the press, it was not to harangue city officials. It was to make sure that they were alerted to it, and to get their feedback and perspective and collaborate with them on how to contain it. That is a testament to them, because it takes an awful lot to build the trust of a community like that.” 

Although environmental impact was a big concern, the city also had to think financially, and both sides recognized that there were monetary benefits to the project as well. The nearly mile-long stretch of sewer was taking in I&I and adding to the city’s wastewater treatment costs. The project’s budget reflected its fiscal importance — Clifton set aside $6 million when it was used to taking on smaller projects in the $1 million to $2 million range.

“As much as we are indebted to the city, and we applaud their stewardship, there was definitely a selfish motivation because their sewer line was losing lots of money because of seepage. Over the years, they were paying a lot of money for an inefficient system,” Grupper says. “Part of their motivation was that they needed to address that, to have a sewer line that was efficient, and that they could reline when they needed to. So this plan was mutually beneficial.”

Part of Grupper and the environmental community’s acceptance of the city’s monetary motivations was due to the transparency and communication that built trust between the groups throughout the planning and execution of the project.

“We built a relationship over time, and it’s key to keep these groups, and even the residents, informed,” Villano says. “The more they know, the more relaxed they are. Otherwise they panic over every little noise they hear. So I always make it a point to hold resident meetings, I welcome any of these groups, so that they have a better understanding of what we’re doing.”

Meetings and information dissemination are important, but equally essential is simply the effort by engineers and stakeholders to put environmental concerns at the forefront. 

“How do you build trust in a community? The first line of approach is communication. They would supply us with periodic updates on the progress of the effort, and most importantly they would tell us when things were not going well, and put us in the know,” Grupper says. “That’s a hugely comforting statement to us. We were in the hands of an effort that was trying its best to minimize the impact on the preserve and see to our interests. So it was an incident-by-incident bolstering of that trust. They did it step by step along the way.”

Taking the Hard Way

Though tunneling began in May 2018, Villano says the project’s origins go back to 2010, when the plan was accepted by city leaders and Neglia Engineering was hired to design the project.

“Now, nine years later, we’re actually seeing the results. It went fairly smooth, not too many residents complaining, not too many problems in the field,” Villano says.

With tunneling now complete, restoration efforts are getting started. Despite the lessened impact of tunneling, each bore pit had 50 square feet of surface clearance or more, and at least 40 trees in addition to brush plants were removed.

“It’s a narrow patch of land, so any impact is really felt immediately, because you can feel when a handful of trees come down,” Grupper says. “It cuts deep into the swath that defines the preserve. It’s prized by the community, it’s beautiful, it’s a little bit of paradise here, so that’s why there’s a lot of sensitivity to any impact.” 

The city is investing $250,000 into restoration and will be planting 200 trees with accompanying plants, all native to the area, with input from Friends of the Bonsal Preserve.

“We’re now moving toward the restoration phase, and we have a lot of faith that they’re going to do it right,” Grupper says. “We have a lot of faith that they’re going to restore the areas they’ve impacted. Because they’ve built that trust.”


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