Fighting Inflow and Infiltration From the Inside

Texas utility successfully tackles inflow and infiltration problems on its own.

Fighting Inflow and Infiltration From the Inside

Pipe bursting helps Lufkin limit excavation to entry and exit pits and connection points.

Sometimes you just need to do things yourself.

The Lufkin (Texas) Water and Sewer Utilities Department management culture emphasizes doing things in-house whenever possible. And while adhering to that ethic, the city has been pressing ahead with a comprehensive sewer rehab program that is targeting a long-standing stormwater inflow and infiltration problem.

The I&I reduction effort has been underway for more than a decade and won’t be finished until 2023. But the results are already apparent.

“We’re seeing next to zero stoppages,” says Jason Arnold, assistant to the city manager and former utilities director. “When we’re seeing major rain events, those neighborhoods just aren’t having issues anymore.”

Located about 120 miles northeast of Houston in eastern Texas, Lufkin sees its population triple every working day.

“We’re a town with a population of a little over 35,000,” Arnold says. “But our daily population is well over 100,000. The number goes up during the day because we are surrounded by several small communities. People come here to work, shop, dine and do business. We’re also a major medical hub.”

Taking control

Lufkin’s I&I problems go back decades. Nearly 75 percent of the collections system is made up of clay tile pipe, which is notorious for its vulnerability to cracks and root penetration that contribute to I&I. Before the I&I abatement program really took hold, a couple of inches of rain is all it would take to overload the city’s sewer treatment plant.

“The lines just couldn’t handle the flow. We’d have overflows in low-lying areas,” says Patrick Lynch, a water and sewer utilities department foreman for 27 years who has the day-to-day task of helping to carry out the subsequent rehab programs. “Pretty much the whole system was overloaded — manhole covers were floating off.”

In the year 2000, Lufkin undertook an in-depth study tracking the impact of I&I-related overflows. With extensive smoke testing, the study also identified hot spots.

Many of the leaks showed up in the private portion of sewer laterals, and the city wrote to homeowners, informing them of their obligation under city codes to have repairs made. But the study also identified plenty of work needed on city-owned lines.

Setting priorities

In 2003, the city launched its sweeping 20-year repair and replacement program. The city was divided into five separate sectors that were ranked by priority. Work has finished on the two highest-priority sectors. Work on the third sector is underway now, and the lowest-priority fourth and fifth sectors will follow.

Projects have ranged from point repairs for localized leaks to complete replacement of sewer lines.

For full replacement, Lufkin has opted for pipe bursting where possible rather than open-trench replacement. “A lot of our lines are under roadways, so it’s more economical to do it by pipe bursting,” Lynch says.

For some bigger projects, such as a recent trunk line main replacement using 24-inch pipe, the city will turn to outside help. But for most of the work, “We try to do as much as we can in-house,” Lynch adds. “It’s easier for us to get material and to service our equipment.”

Lufkin uses Vermeer pipe bursting equipment — chosen because the company has a regional office less than 100 miles away, as well as for the quality of its machinery. The new pipe going in is all PVC.

“We’ve become experts in the whole pipe bursting process,” Arnold says.

In more than a dozen years since the work started, Lynch has seen the equipment evolve. Where Lufkin once used an 8-ton winch to pull new pipe through the old, the city has upgraded to a 12-ton winch that allows for longer pulls — especially through the region’s unforgiving clay soil that hampered the smaller tool’s pulling capacity.

Perfecting the system

More recently, the city has begun using Perma-Liner Industries cured-in-place products when that approach is feasible. In keeping with its do-it-yourself ethic, the city has been training its own crews and acquiring the lining equipment rather than contracting out for that work. But it remains in the early stages. “We’re still perfecting the system,” Arnold says.

In choosing where to use pipe bursting and where to use lining, Lynch says it depends on the situation. Pipe bursting requires some localized excavation, such as where laterals connect to the mains. Since CIPP lining is an entirely no-dig system, it’s especially useful where lots of other utilities — waterlines and electrical conduits, for example — are close to each other.

For lining projects, the city is now aided by a TRY TEK Machine Works robotic cutter that it sends through the lines to trim up the material where there are pipe transitions. Arnold says the city also developed its own winch system to help pull the liner material through. The vehicle used for lining work has been supplied with modified refrigeration units to store the liner material.

“Where we’re still having to pipe burst are in those areas where we’re not comfortable putting that cutter in the ground,” Arnold says. “And then there are areas that are so long it’s difficult to store (lining) stock that long or blow it in.” Longer stretches require precision that can be challenging, he notes. “The biggest we’ve done so far is 575 feet.”

But Lufkin is sold on the trenchless approach wherever it’s practical. “The benefits are pretty obvious,” Arnold says. “You’re saving a lot of time; you’re saving a lot of money. But most important, you’re not risking a trench accident.

“We want to get people out of those trenches every chance we get, and that’s what we’re working toward.”

Moving forward

The city has been happy with the outcome. “We can definitely see that we’re making progress on the problems,” Lynch says. “If you go through a spot where previously the sewer system was overflowing and where we have gone in and redone a section of it, you can see the system is able to handle it. Just knowing you’re making a dent in the problem gives us the motivation to keep moving forward.”

Training employees to do the work and acquiring the necessary equipment has given the city greater flexibility, Arnold says. “Because we have the expertise, we do everything that we can ourselves.”

Doing the work in-house just makes problems easier to solve, the director explains. There are a lot fewer worries about who the city will have to call in an emergency or where the money is going to come from to hire a contractor to fix it.

“Rare is the construction project that we don’t do,” Arnold says. “We have a good engineering department. We have extremely qualified operators — guys who can really do just about everything, and looking at the whole scope of a job, can do it the best and the safest.”

Keeping the work in-house also builds morale. “It changes the whole attitude,” Arnold says. “Our whole attitude is that there’s nothing we can’t take care of. Our guys take a lot of pride in not needing to call in contractors to do what we’re doing. They enjoy the fact that they’re given the tools and the people to do what they need to do.”



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