Maximum Effort

Pipe bursting enables a Louisiana contractor to replace a blocked sewer lateral after a failed directional boring attempt.
Maximum Effort
The 4-inch HDPE pipe advances through the enlarged holes in the concrete stormwater vault. Behind the pipe are two 36-inch-diameter concrete drains. The original clay tile lateral switched to cast iron at this point.

Interested in Relining/Rehab?

Get Relining/Rehab articles, news and videos right in your inbox! Sign up now.

Relining/Rehab + Get Alerts

For more than 25 years, blockages and backups were a way of life for the owners of a two-story pier-and-beam house in Shreveport, Louisiana. In 2011, local plumbing contractor Pioneer Comfort Systems began responding to emergencies.
“Service calls took two to three hours because the blockages were so difficult to remove, even when using our RIDGID K-60 cable machine,” says operations manager Michael Smith. “Massive root intrusion in the 4-inch clay tile lateral caused bathroom tissue stoppages. We removed tons of it.”

The lateral ran through a concrete stormwater vault in the neighbor’s driveway, then 15 feet across her yard to an abandoned 12-inch clay sewer discharging to a manhole in the street in front of the property. As the only lateral tied to the capped sewer, and with no flow from upstream to help wash away the client’s solids, blockages occurred when solids built up in the sewer and dammed the lateral.

On Smith’s last service call — only six months after a previous visit — he used a RIDGID SeeSnake to inspect all 230 feet of the clogged line, then cleaned it with a Cam Spray cart-mounted jetter. The amount of the bill, with no guarantee of how long the lateral would remain open, convinced the owners to replace the pipe.

GOOD NEIGHBORS

The home, built more than 50 years ago at the bottom of a hill, has two laterals. One runs from the front of the house and connects with the second lateral from the laundry room and full bath. The pipe passes through the 30-inch-deep vault, then turns 45 degrees shortly before a wye connects it to the sewer. Both fittings are under the neighbor’s flower beds. Developers would never obtain building permits for the site today.

“Our initial plan was to directional drill a replacement lateral from the customer’s backyard, under the square vault with two 36-inch concrete storm drains, and straight out to the manhole,” says Smith. “The boring contractor said the grade was going to be close, but he saw no problems. Boy, was he wrong.”

When Smith’s crew excavated beside the manhole, they uncovered a water main crossing the path where the bore bit would enter the structure. Their alternative solution was to excavate upstream from the manhole to expose the old sewer, then bore to it and cap the downstream end of the main. With the city’s approval, the team trenched 15 feet back from the manhole following the sewer, then dug the bore pit.

Both sewer excavations were in the neighbor’s front yard. At some point, the deteriorating main had created a large void under her house, causing the city to abandon the line and reroute it alongside her driveway. “She understood what our customer was going through and cooperated fully,” says Smith. “We are indebted to her.”

THREE STRIKES AND OUT

The boring contractor arrived the next morning. On his first attempt, the bit deflected off a 12- to 18-inch-thick concrete mass beneath the vault and dove straight down. The operator changed the machine’s location three times to find a route under the obstruction, but there wasn’t enough distance for the bit to regain sufficient fall before reaching the exposed sewer.

“We fought the problem for six hours, then the operator packed up and went home,” says Smith. “That left pipe bursting and the possibility of destroying the rest of the neighbor’s front lawn. I talked to her again and she gave us permission to continue.”

On the third day, the crew burst the laterals. Smith’s major concern was lodging the 6-inch O.D. bursting head in the vault or downstream fittings. To avoid problems in the vault, they cut out the section of lateral running through it, then enlarged the entry and exit holes with a hammer drill.

Workers dug a 6- by 6- by 5-foot entry pit 6 feet upstream from the vault and enlarged the sewer excavation to create a 6-foot-wide by 8-foot-deep pulling pit. Wishing to use the main as a sleeve for the 4-inch HDPE pipe, Smith set the C20 pipe bursting system (TRIC Tools) as low as possible, enabling the lateral to rest on the bottom of the pipe. The ram is rated for 8,000 psi or 19.24 tons of pull.

It took 60 minutes to send the rodder through the lateral and pull back the 3/4-inch swage cable attached to the bursting head, erect shoring and the resistance plate, and set the pulley and ram. Meanwhile, other workers fused two 40-foot sticks of HDPE pipe in the customer’s backyard, then snaked it through a gate to the entry pit.

“We painted a green mark on the HDPE pipe to indicate when the bursting head had passed through the wye,” says Smith. “Once the mark disappeared into the pit, we knew we’d be home free.”

HITCHIN’ A RIDE

The first pull was 80 feet from the entry pit to the pulling pit. Smith stationed himself at the stormwater vault to make sure the head passed through it uneventfully, then he controlled the ram and monitored the hydraulic pressure. Pressures for a normal pipe burst on this machine run 2,000 to 3,000 psi (5 to 7 tons of pulling force), and sometimes reach 3,500 psi (8.5 tons of pull). They will hit 6,000 psi (14 to 15 tons of pull) when going through a 45-degree elbow.

As soon as the head entered the vault’s downstream side, the pressure jumped to 6,500 psi, then hovered between 6,800 to 7,200 psi (17 tons of pull) for 30 minutes. Twice, the needle hit 7,800 psi (19 tons of pull). “I was a nervous wreck,” says Smith. “We’d never pushed the machine that hard before and had no idea how the equipment would react.” Once the head entered the sewer, the pressure returned to 3,500 psi.

When workers extracted the head, they found a 4-inch cast iron check valve wrapped around it. “We were amazed,” says Smith. “The ram had pulled that valve 20 feet through the lateral, then through the two fittings and 60 feet to the exit pit.”

While two laborers moved the ram to a hand-dug 4- by 4- by 2.5-foot pit in the customer’s backyard, another person butt-fused a 20-foot stick of HDPE pipe to connect the new lateral to the manhole, then sealed the
sewer opening.

BUBBLE TROUBLE

The second pull, 130 feet from the entry pit to the backyard, replaced the house lateral. It was uneventful. The crew backfilled on the fourth day and spent a few hours laying sod on the fifth. When Smith returned a few days later to check on the sod, the customer’s wife ran out to meet him.

“On a service call, I’d noticed water and soap suds around the floor drain in the laundry room,” says Smith. “The owner assured me the drain had always worked that way. His wife was as excited as she could be because the wash water was no longer bubbling out.”



Discussion

Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.