Getting Down and Dirty

Pipe InspectionWhen a pipe needs to be inspected, there is no shortage of options for choosing the proper camera, software and other technology to assess the underground pipe — no matter its size and location. The process is done remotely by sending the small camera into the pipe to gather data via photos and videos, with crewmembers remaining aboveground to assess it.

But there are instances when all the technology in the world can’t compete with a completely broken pipe, necessitating the old school walk-through (or crawl-through in this case) by a crewmember to take the needed photos and video of deteriorated pipe. That’s what happened on a project in Marin County, Calif., near the Golden Gate Bridge.

Miksis Services was called in to help rehabilitate a 265-ft section of 24-in. corrugated metal culvert, as part of an extensive road overlay project in the Golden Gate National Recreation Area. The culvert was located in a hillside on the northern side of Golden Gate Bridge and carried water under three roadways, which have access to the main highway.

Established in 1981, Miksis Services Inc. is a sewer and storm pipe inspection and repair company that services Northern California, including CCTV, pipe location and smoke testing. Based in Healdsburg, Calif., the company provides pipe cleaning services (jetting, buckets and winches, and vacuum), as well as trenchless pipe rehab methods, such as cured-in-place pipe (CIPP) relining, pipe bursting, centrifugally cast concrete pipe (CCCP) and fold-and-form.

The Golden Gate National Recreation Area is a U.S. National Recreation Area that protects 80,002 acres of ecologically and historically significant landscapes surrounding the San Francisco Bay Area. Much of the park is land formerly used by the U.S. Army. The Golden Gate National Recreation Area is managed by the National Park Service and is one of the most visited units of the National Park system in the United States, with more than 13 million visitors a year — so minimal disruption (to the tourists and surrounding wildlife and habitat) in addressing this culvert was critical.

To say the area is environmentally sensitive is an understatement, said Miksis Services president Gary Miksis. “Digging the pipe up and replacing it was not an option,” he said. Also, due to the environmentally sensitive area, the project owner ruled out using CIPP as a rehabilitation method. Miksis Services would use fold-and-form pipe rehabilitation on the project.

Pipe InspectionBut before Miksis Services could develop a rehabilitation plan, the contractor needed to know specifically what was wrong with the pipe and how extensive the damage was — was the entire culvert damaged or were just certain parts? A complete inspection was required. The pipe was about 50 years old, about 25 years beyond its life expectancy. “We initially put a flashlight down in it during some preliminary work and realized there wasn’t any bottom to the pipe. Water had eroded the culvert to the point where the invert was completely gone.” Miksis said.

The original plan involved televising the culvert to assess the damage and then put in a concrete liner. However, those plans were scuttled once Miksis Services realized the extent of the problem.

“The invert first needed to be re-established,” Miksis said. “The problem with the [existing] invert was that there wasn’t any bottom to it to allow us to put a camera through the pipe.”

The Miksis crew proposed mounting an R.S. Technical ProTRACK camera on a skid and sliding it through the 265-ft culvert. “The skid was made like a large spoon so it could ride up higher in the culvert, which had a 16 percent slope. We pushed [the skid] in the pipe with fiberglass poles to try to get video of the pipe. We tried from both directions but it didn’t work. The skid fell out of the pipe and we had to retrieve it.”

So Plan B: having a crewmember do a walk-through inspection of the pipe. “We opted to put a man in the confined space. The pipe diameter was 24 in. and the void underneath the pipe was about 3 ft deep. [TJ Sales] strapped a camera to his [hardhat] and crawled through the pipe.”

Video interfaced with RST’s POSM software revealed to the crew the enormity of the damage, which included heavy rust on the top of the pipe in addition to the void at the bottom of it. The invert had to be re-created before the culvert could be rehabbed — no small task. Using 35 yards of lightweight grout mix (the equivalent of about three cement trucks) and building the invert in 5-ft sections, the Miksis crew filled the void, which took about four days to complete. Then the crew turned its attention to relining the culvert.

The crew planned to use DynaLiner LLC’s PVC fold-and-form pipeline rehabilitation system to create the “new” pipe.  The liner is extruded in a factory in the same manner as conventional PVC pipe, but unlike sectional pipe, DynaLiner is (while still hot) folded into either a “C” or “H” shape prior to being wrapped on a coil. The Miksis crew used steam heat to mold in tight conformity to the host pipe. The thermoforming properties of the PVC resin allows for greater conformity to deformities in the existing host pipe
“After we re-established the pipe, we did another inspection, just like any other pipe (using camera technology),” Miksis said. “But to get to that point, it was an enormous amount of labor and strategy.”

Sharon M. Bueno is managing editor of Trenchless Technology.
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