Some jobs only require a week or two of work. Others mandate shifts that span 24 hours a day, seven days a week and take three years to finish. This was the second kind of job.

It started when The Central Nebraska Public Power and Irrigation District decided to recoat an irrigation pipe that ran along a canal. The goal was to extend its life by up to 30 years.

“The siphon is in pretty good shape, despite the fact that it’s almost 70 years old,” Cory Steinke, the Central Nebraska Public Power and Irrigation District civil engineer overseeing the project, said via the district’s newsletter. “Tests showed that the steel in the siphon has retained plenty of thickness, but we wanted to stop the corrosion that was occurring on the inside.”

The district needed someone to apply a flexible polymer coating to the inner surface of the pipe to stop corrosion of its steel walls. “The coating will also provide a smooth surface that will improve the siphon’s capacity to carry water by reducing hydraulic friction,” according to the district’s newsletter.

That is where Jim Stotler and the Allen Blasting and Coating, Inc. crew came in. The New London, Iowa-based coatings contractor opened for business in 2003 and specializes in providing services that include tank linings, floor toppings, industrial coatings, painting, ceramic insulation, and fireproofing.

The client was “looking at a supplier we use all the time, so we got the lead,” Stotler said. “They asked us to come out and look at it, and we followed up with them.” Allen Blasting and Coating got the job, and it was a big one. They would be working on more than 6,900 linear feet (2.1 km) of underground irrigation pipe that was 6 feet (1.8 m) in diameter. It was heavily corroded carbon steel with thick pack rust and debris built up.

“It was just really rough — a lot of debris,” Stotler said. So how did they manage the long-lasting project?

On Demand
The job spanned a three-year period beginning in 2011 and wrapping up in 2013. “This project always had to be performed in the winter months due to water running through the pipe throughout the rest of the year for irrigation season,” Stotler said.

The team worked for two weeks in 2011, two months in 2012, and another month and a half in 2013. But this was not your average 9-to-5 job. 

“We had 15 to 18 crew members on rotating schedules with five on a day shift and five on a night shift for seven days a week, 24 hours a day for two weeks,” Stotler said. “Then one crew would go home for a week, and the relief crew would come in and do the same thing. After the crew that went home was off for a week, they came back and relieved the next crew.” 

The reason for this around-the-clock schedule was that the job required keeping the compressors going 24 hours a day so they did not freeze up. Remember, this work was done in the winter when the irrigation pump was not in use. “It’s an irrigation district, so the job had to be done during the winter months because they run water through it,” Stotler said. “Our solution to handle it was we ran multiple shifts, kept guys going 24 hours a day so we could keep productive and keep the equipment going.”

This constant work was a challenge, Stotler said. “If it wasn’t done we would have had multiple equipment problems not wanting to start after sitting all night,” he said. “Also the pipe was cold so it had to be heated and it is a lot easier to keep heated than to start from scratch every day.”

The demanding schedule made it difficult for Stotler to keep his crew fresh. “Going seven days a week, the guys would get worn out, so we had to keep rotating them, but bringing in new guys was a challenge because they’ve been out a week so they get out of the swing of things,” he said. “We have to bring them back and get them back into the swing of things.” 

The jobsite itself added to the complications. “Normally we work on a job with a guard shack and fence around it, and this one was in the middle of a cornfield,” Stotler said. “In turn, that meant we were facing directly any kind of weather that happened, whether it was rain or snow.”

Safety Conscious
To start, the crew sandblasted the inner walls of the pipe to remove any corrosion, sediment, and organic deposits that accumulated on the surface. They then applied Polibrid 705 Elastomeric Polyurethane Lining in one 80- to 100-mil (2,032.0–2,540.0 microns) pass to the entire inner surface of the pipe.

To put the coating down, the crew used a Graco plural component pump with a specially designed trailer that had its own generator, and they used climate control to keep the spray pump and material warm while the application process was under way.

“We used abrasives from Abrasive Inc., and they were delivered on truck loads,” Stotler said. “We used approximately 7,500 to 8,000 gallons [28.4–30.3 kL] of Polibrid in the month period on the biggest section we did in 2012 and over 500,000 pounds [226,796.19 kg] of abrasive.”

Before the job began, the Central Nebraska Public Power and Irrigation District decided on the coating after testing it on the pipe. “The tests revealed a sustained increase in flow capacity of about 8 cubic feet per second [0.2 m³ per second], which indicated that significant capacity gains could be obtained by coating the entire siphon,” according to the district’s newsletter.

For the entire blasting and spraying process, the crew used air-fed hoods with fresh air being pumped through. They also set up tripod retrieval systems on the access holes in case of an emergency, and they put carts inside the hole. “In the event we couldn’t get someone out of the hole, they could be wheeled out the entrance or exit ends,” Stotler said. “The local fire department was notified of our work in case of an emergency, and air monitoring was done on a regular basis as stated in our confined space program.”

Life Cycle Extended
After many long hours and years of work, the job was finally done. And it was worth it, because the irrigation pipe serves an important purpose. It carries water from a supply canal to the Elwood Reservoir to two Nebraska counties. “It’s a critical part of the E65 delivery system,” Steinke told the district’s newsletter. “Extending its useful life by applying this coating removes the need to consider siphon replacement until well into the future.”