The city of Minden, La., might be easy to miss on a map. Its population of 13,000 people could fit in the Mercedes-Benz (Louisiana) Superdome five times over with seats to spare. And Rick Broussard, who manages water and wastewater services for the city, says his department isn’t anything too special.

Broussard is being modest.

Despite its small size and budget, Minden has been steadily improving its sewer infrastructure over the last decade. It has undertaken a series of repair programs to reduce inflow and infiltration and improve the condition of its pipes and manholes.

And it has done so, as Broussard is proud to note, without having to borrow money. Funds for some maintenance work have come out of the city’s ordinary cash flow, and Minden has also made canny use of grant money from various state and federal sources to cover the costs.

Mapping the problems

If you want to see the newest pieces of sewer maintenance machinery in action, you won’t find any of them here. “Our biggest piece of equipment is a backhoe,” Broussard says.

Instead, what you’ll find is a story of professionalism and can-do equal to that of any big city department. And while Minden may not be able to invest in many of the newer tools of the field as quickly as larger cities do, the city also doesn’t shy away from thoughtful commitment to the technology it needs to do the job.

It’s had a GIS-based utility mapping and asset management system in place for 10 years, and Broussard hears from vendors and colleagues in the municipal sewer field that it’s on a par with cities several times larger.

“There are no small towns that I know of that have this system,” he says.

Minden made “some significant leaps” about a decade ago when it contracted with an engineering firm to do a major study of its sewer system using smoke tests and other tools. The study produced the GIS map that Minden still uses to keep tabs on the system.

The study was prompted by chronic sewer system overflows largely due to I&I. The city had little clue where the system’s main I&I problems were located, and Broussard was able to persuade city officials that the study would be a good use of Minden’s sewer rehabilitation funds.

“We did it because we felt like we had to,” Broussard says. “It cost us half a million dollars to do the study. It’s paid for itself over and over and over again.”

The map is precise within a little more than three yards, making location far more accurate than previously was possible. “We’re able to pull up manholes and accurately measure the distance between them,” he says.

It also stores detailed data about each manhole, including its composition and condition, along with photos of the site.

“The contractors gave us a huge book of information that prioritized leaks in the sewer system,” Broussard says. “It allowed us to identify places in the city that needed immediate attention.”

Working down the list

In the years since that first study, the city has worked its way down that list. The steps are generally the same: hiring a contractor to clean and conduct video inspections of the lines, further identifying the top priorities for repairs or replacement, and then lining or replacing the sewers with the worst damage.

“We were running on an annual budget for sewer rehabilitation of about half a million dollars a year,” Broussard says. “But budgets have gotten tighter the last couple of years, and we’re relying almost exclusively on grants.”

Typical projects run in the neighborhood of $500,000, which might cover about 6,000 feet of sewer.

Broussard says his department has been able to spend about $2 million dollars over a two- or three-year period and make major improvements. The city’s far enough along on the list that officials can now go back and look at less obvious and less serious areas in the system.

Trenches and trenchless

Some of the rehab projects have required open cut and full replacement, while others have used cured-in-place pipe lining. It isn’t always initially clear which is the right approach.

Broussard recalls a 550-foot segment of sewer that was supposed to be lined. “After I looked at the video, though, I said, ‘No, we’ll have to open cut it,’ ” he says. The video inspection had uncovered numerous dips in the line that inhibited flow — a problem that lining the existing pipe wouldn’t rectify.

That experience points out another thing that Minden has learned: how to work closely with its outside contractors. Broussard isn’t in favor of simply handing the project over and letting contractors make all the decisions.

Most of the city’s original sewer lines are clay tile pipe, with some cast iron lines. When they’re replaced, Minden uses PVC pipe, with ductile iron where a line is crossing a creek or has to be close to the surface of the ground. “We like to keep at least 3 feet of cover over the top,” Broussard says.

When lining is involved, products from Suncoast Infrastructure and Insituform Technologies are usually closest to the specs Minden uses. Up to now, the city has primarily relied on heat-activated epoxy liners, but may consider ultraviolet-cured products in the future.

Major project

One of the bigger projects in recent years took place in 2012. It covered a total of 11,000 feet of sewer, with 6,400 feet of that using CIP rehabilitation and another 4,500 feet of open cut replacement. Additionally, 30 new manholes were installed in the open-cut segments, and 28 manholes were rehabilitated in the designated repair areas.

For manhole rehab, Minden specifies SpectraShield from CCI Spectrum. Broussard says the product gained favor over standard epoxy because it uses a layer of expanded foam over epoxy. That proved to be less likely to crack all the way through when used in unstable ground or where the area is subject to vibration from heavy vehicle traffic, he says.

“We tried it, and on our first job with it we were delighted with the process,” he says. “We’ve been satisfied with it ever since. It’s been seven or eight years, and we have not had any of the manholes give us a problem.”

The whole 2012 project, funded by a Louisiana community development block grant, came in at $732,000. That wasn’t all one stretch of line, Broussard explains; sewer block grants generally are capped at $800,000, so the city has learned how to bundle several projects together to get as close to that ceiling as possible.

Noticeable impact

The succession of repairs over the years has had a noticeable impact. “When we first started, our wastewater treatment plant had 1.8 mgd go through,” Broussard says. “That could easily go up to 7 mgd when we had a rain event of 2 or 3 inches of water in a day.”

The plant’s three screw pumps, capable of 2,200 to 2,500 gallons a minute each, couldn’t keep up with the flow during those peak times.
It’s been years since problems have gotten that bad, he says. Average flow has fallen to 1.4 mgd, and while a couple years of below-average rainfall in 2010 and 2011 contributed to the lower flow, the moisture picked up in 2012 to slightly above average. The highest flow produced by a significant rain event now, however, is down to about 3 mgd.

And sewer overflows, which occurred at least monthly before the city began the repair program, are now no more frequent than once every three months. “We’ve had a significant reduction,” Broussard says. “A lot of it has been these rehabilitation projects.”

The road ahead

Broussard does hope, eventually, to see the city invest in a sophisticated pan-and-tilt camera with more powerful lighting. He thinks he could probably put two full-time operators to work conducting further sewer system evaluations and inspections with the camera. Currently, he points out, it costs about $6 per foot to clean and inspect, which works out to nearly $2,500 just for a 400-foot stretch of sewer.

The city’s water system is next on the mapping agenda. The source of a water system malfunction can often be a lot harder to diagnose than sewers, Broussard notes. Stopping the flow in a water main break  might require trial and error to find which valve or valves will do the trick. And valves need to be exercised frequently — something that hasn’t always been done in the past — or else crews risk breaking an old valve when they try to shut it off.

All that means mapping the system is going to be a lot more complicated and undoubtedly a lot more expensive, Broussard says.

Given the city’s track record, it’s a fair guess that he’ll find a way to get it done.