Written by Tracy Weaver

It was just a typical day at company headquarters in Portland, TN, when Vice President Mike Woodcock received a telephone call in the summer of 2017. On the line was Justin Weiler P.E., Assistant Chief of Operations and Maintenance for Hanover County Public Utilities in Virginia. Hanover Utilities, Justin explained, needed a solution for repairing a 375 linear foot (LF) section of deteriorated sewer pipe. With Justin’s phone call, the process began for what Portland Utilities Construction Company does best; helping clients solve inflow/infiltration pipe line problems via trenchless technology.

THE PROBLEM: TOO MUCH WATER

A section of sewer pipe identified by Hanover Utilities greatly in need of repair was a 375 LF 12-inch asbestos sewer line installed circa 1979. Located in a residential area, between an upstream manhole and a downstream manhole, the buried pipe was down in a wooded area near Dabney Lake. There were six (6) joints spraying water into the line, each pouring in an amount with the consistency of a running garden hose. The County had considered UV CIPP lining to repair this section, but was looking into alternative rehabilitation methods due to the excessive infiltration. During a brainstorm meeting with colleagues about how best to make the repair, the pipe burst method came to light. County representatives then spoke with a local contractor about pipe bursting as a possible solution. The local contractor suggested the County call our offices. 

 

On the day Justin telephoned PUCC, he wanted to know if Mike thought pipe bursting would solve the 12-inch sewer line’s water infiltration problem. He described the tremendous amounts of ground water from Dabney Lake infiltrating into the 12-inch sewer pipe through leaking joints. Justin explained that he was most concerned about a pipe collapse, as the pipe appeared to be deteriorated. In the event of a pipe failure, the County would then be forced to dig up the entire section in an area saturated with ground water.

Pipe bursting would be a viable option for this project, but because the line was within close proximity to the small lake, digging the launch pits in the saturated ground would be expensive. To successfully pipe burst the section, the ground would most likely have to be dewatered by well pointing below the sewer line. Mike suggested revisiting the UV CIPP liner option. After exchanging plan details, CCTV, and a site visit, PUCC proposed to line the pipe with UV CIPP after installing internal point repairs by Pipe Robotec. Mike then turned the project over to long-time PUCC veteran Gary Testa.  

THE WORK VIA UV CIPP METHOD 

To assess the job and measure the line, PUCC general superintendent Gary Testa took along PUCC estimator Vince Bayles and UV CIPP lining superintendent Troy Goforth. 

“The site was doable,” Vince shared later after the job was complete. “I had reviewed the County’s pre-television tapes and saw the line had a lot of ground water infiltration. Most of the water was coming from the deteriorated pipe joints and holes in the pipe. The biggest problem was the saturated ground from the nearby lake which set above most of the line. The upstream manhole was at the edge of the lake. Water was literally pouring over the pipe. Gary, Troy and I agreed that if we were going to line this section of pipe via UV CIPP, we would have to pick the right day without rain. The challenge was going to be stopping the water long enough to cure the line with the UV light train. Because of the age and condition of the existing pipe, we didn’t know if the pipe integrity would allow us to use the interior Robotec clamps to seal off the water infiltration or if the pipe would collapse under the pressure needed to seal the clamps against the walls of the pipe. If we succeeded and the seals held, we also risked other leaks further down the line from weak points in the pipe.” 

The schedule to begin the UV CIPP lining operation was established for Monday September 11. The County had set up the sewer bypass when PUCC’s UV CIPP lining crew arrived on site. Once the sewer was bypassed to another manhole, the crew pre-televised the line. 

“We estimated at a bare minimum about a million gallons of water a week infiltrating into the pipe,” said Troy Goforth. “We knew for the UV CIPP liner to be successful, we had to slow the water down from flowing into the pipe. We attempted to install Robotec Seal clamps on the six (6) active leaks, but the pipe was so flakey, it came apart at the joints. The internal Robotec pipe seals did manage to slow the water down, however.” 

After the installation of the pipe seals, a flow of about 2-inches of groundwater infiltration still ran down the bottom of the host pipe, even while the sewer flows were being bypassed around the line segment. The water was generated from the remaining leaks in the 12-inch host pipe line about to receive the UV CIPP liner. The team discussed ordering six (6) more seals. It was agreed all around, however, that more pipe seals probably would not be effective at stopping entirely all of the water infiltration. 

“The pipe was so deteriorated it leaked around the patches,” said Gary Testa. “But I knew there was no way I was going to sink a bucket into that ground. It was too wet, and without well pointing, pipe bursting or digging up that 375 LF section of pipe was not going to be a good option. We would have to give the UV CIPP liner a shot.” 

The key would be to blow the liner up slowly and in such a manner that would squeeze the infiltrating water out of the host pipe until the liner was able to eventually seal off the leaks. In essence, the liner had to be pressurized with more air than the water pressure infiltrating. It took about 7psi of air in the liner to hold back the water pressure. Once the liner bag was aired up, the light train with video inspection equipment was pulled through the inflated liner to inspect and verify the pre-cure condition was acceptable. 

“We were more than a little worried, but we were very pleased with how the liner looked during the inspection. It was holding back the groundwater pressure just as we had hoped,” says Testa. 

After the liner inspection, the UV lights were turned on and the crew pulled the light train back through the inflated liner bag to cure the pipe in place. The entire cure process took about 120 minutes between the firing of the bulbs on the light train and until cut-off. Once the cure process was complete, the client had a 375-linear foot, structurally sound, piece of fiberglass pipe. The issue of groundwater infiltrating into the sewer system through the leaky pipe had been solved by the UV CIPP method. 

THE FOLLOW-UP: A SOLID PIECE OF PIPE 

PUCC’s founder, Ernie Woodcock, dates his sewer and water pipe line experience back to the 1960s. Then and now, getting the job done and making the client happy has always been Mr. Woodcock’s top priority. After the liner was installed, Mr. Woodcock telephoned Justin Weiler to ask if Hanover Utilities was satisfied with the UV CIPP lining of the 375-linear foot section of pipe. “ 

Absolutely,” said Justin. “We really appreciate Portland coming to do the line. The crews did a great job! They worked well with the neighbors, not tearing up the yards and successfully installed the UV CIPP liner. We are extremely satisfied with the job.” 

Mr. Woodcock believes the challenges presented by the Hanover Utilities project and overcome by the UV CIPP lining method shines new light on the capabilities of the UV CIPP liner product. “Of particular interest,” says Mr. Woodcock, “is the 2-inches of water on the bottom of the host pipe that we were able to successfully line and rehabilitate anyway due to the UV light train curing process. Regardless of the presence of actively infiltrating water and the water’s temperature, the liner was able to cure and manifest into a strong, solid piece of fiberglass pipe. The system owner now has a 50-year lifespan for what is basically a new pipe in this section of their collection system.” 

To learn more about the viable trenchless technology services offered by Portland Utilities Construction Co., visit www.pucc.org. Helping solve sewer and water pipe line problems is just a typical day in the neighborhood for them.