An old 6-inch vitrified clay pipe running along the face of a 100-foot cliff in St. Helens, Ore., had cracked. Sewage streaming through it quickly created a 5-inch hole, sending the flow down the cliff to collect in an unpaved area of the Boise/Cascade Veneer Mill parking lot.
The Department of Environ-mental Quality was scheduled to inspect the mill in four days. An uncontrolled raw sewage spill would cost untold dollars in fines and close the mill until the area was decontaminated. The situation required an immediate response.
Justin Rush, engineer I at the City of St. Helens, met with Sondi Edwards, project manager for Zwald Industrial Services in Tillamook, Ore. “We stood at the top of the cliff and stared down at 211 feet of pipe running mostly underneath a bed of blackberry briars on unstable ground,” says Edwards, who recommended a cured-in-place pipe (CIPP) lining system from Perma-Liner Industries Inc.
In one of the most complicated jobs in the company’s history, Zwald established a bypass system, lined 150 feet of pipe, and met the mill’s inspection deadline, all with a perfect safety record.
What lies beneath
Loose soil, rocks the size of bowling balls, and litter covered the cliff’s rock face. Safety was paramount, as the ground shifted with every step. “The trickiest part was knowing where to start,” says Edwards. “We were in uncharted territory, trying to develop safety strategies without full knowledge of potential dangers.”
Edwards called safety adviser Greg McDonald of Public Works Supply Inc. in Donald, Ore., for advice. He recommended the safety equipment to purchase and called for a rope-grab system for workers to use as a lifeline when scaling the cliff. Footing was treacherous. “Boulders slid under our feet as soon as we applied weight, and overgrown vegetation made it impossible to tell whether our next step would be on ground or on nothing at all,” says Edwards.
Little of the trail following the pipe was visible or traversable. Clearing a path through the impenetrable briars posed another major problem. “Walking along the edge of the cliff was dangerous enough without operating a gasoline-powered, metal-bladed weed trimmer,” says Edwards.
Certified installer Steve Neal accepted the challenge. Strapped in his safety harness to the lifeline anchored at the top of the cliff, he cautiously worked his way up the path, being careful not to tangle the line in the metal blade. After many grueling hours, he had blazed a trail to the top of the pipe.
Sanitary bypass
A temporary bypass rerouted the sewage and prevented further leakage. Neal and lead technician and certified installer Eric Manning carried 20-foot lengths of 6-inch 3034 snap-fit PVC pipe up the cliff, while other workers snapped the sections together from the bottom up. They followed the contour of the sewer line, which had ample slope to maintain hydraulic flow.
The Zwald crew plugged the old sewer with a pig at the hub in the manhole and detached the pipe at a joint. Using a Fernco QwikSeal connection, they hooked up the bypass, deflated the pig, then walked the entire line checking for leaks. None appeared.
To stabilize the bypass line over the Memorial Day weekend, workers lashed it to trees or drove 18-inch stakes in the ground. They coned off the contaminated area and work site to keep out unauthorized persons. City officials visited regularly over the holiday to verify that the line was undisturbed and not leaking.
On Tuesday morning, the Zwald crew arrived with the Perma-Liner trailer. They cleaned the old pipe with a Spartan mini-jetter, televised the line using a Ratech pushrod camera, measured the length of the repair, marked the start and stop points, and laid out 160 feet of liner material.
“We chose the Perma-Lateral single-access pipe relining system because we could position the air inversion tank at the top of the cliff and connect directly to host pipe with the delivery hose,” says Edwards.
Everything associated with the lining process – calibration tube (heavy-duty balloon), pull tape, resin, oil, plywood – was measured and double checked for accuracy. The team connected the 15-foot delivery hose with inversion head to the air inversion tank, then practiced swinging the hose over the edge of the cliff and using the rope tied near the inversion head to lower it to the open end of the host pipe. “We did everything we could to plan our safety and the installation process,” says Edwards.
Wednesday morning
The team’s meticulous preparations paid off. Working on a plastic-covered plywood sheet, they impregnated the felt with two-part resin, then rolled the liner into the air inversion tank. Edwards quickly scaled the cliff to position the inversion head and signal when it was safe for air pressure to invert and blow the liner through the pipe. She repeated her journey to insert the calibration tube, which was inflated to 14 psi to force the liner against the walls while the resin cooked.
Four hours later, the crew removed the calibration tube and inspected the work. “Our liner marks were dead on, and the liner looked awesome,” says Edwards. After removing the bypass system, Dan Jones Conveyor Trucks Inc. in Portland delivered several cubic yards of gravel, covering a portion of exposed, unlined pipe to help prevent damage from exposure.
The City of St. Helens removed the contaminated soils where sewage had seeped, sanitized the area, and backfilled it. On Thursday, DEQ officials had no issues with that portion of the mill’s property, and no evidence remained that Zwald Industrial Services had ever been there.
