California City Notching Steady Wins in Fight Against I&I

Workers battle California’s coastal terrain, pursuing steady infiltration reduction.

California City Notching Steady Wins in Fight Against I&I

Subcontractor Aegion Insituform installs heat-cured CIPP liners in sewer mains for the city of Arcata, California.

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The Northern California coastal city of Arcata receives 45-plus inches of rain each year, and too much of that rainwater ends up in the city’s network of sewer pipes. In the older downtown section, some downspouts once emptied into sewer pipe. Consequently, during the wet season, an average of 5.9 mgd of water — sometimes more — flows into the sewer system.

Or it did until recently. City officials hope they have curtailed the infiltration. The first phase in overhauling the system is virtually complete after 18 months’ work, during which crews overcame underground surprises, pushed CUES and RapidView IBAK North America inspection cameras to their limits in small-diameter pipe and weathered wet winters.

“Our goal in this project was to lower the inflow and infiltration by at least 1 mgd during the wet season,” says Netra Khatri, Arcata’s city engineer. “We have to look at the data to see if we succeeded, but indications are that we did. One pipe, for example, that ran a lot is not running a lot now.”

Of such incremental victories are sewer systems made whole. After all, the city’s rehabilitation project was termed an I&I reduction task. Elimination of I&I is never envisioned in such undertakings. This is especially true when, as in Arcata, the pipeline has segments 65-70 years old — infrastructure well past its prime.

Antique infrastructure

Arcata is situated on an inlet of Humboldt Bay and dates to the 19th century. It was incorporated in the early 20th century, and Khatri, working for the city for six years, has seen remnants of the wooden pipes that once carried sewage beneath city streets. While recently replaced pipe was constructed of vitrified clay, after being in the ground for 70 years, clay pipe qualifies as antique.

The chronic I&I has concerned Arcata sewer officials for nearly 20 years. In 2001, 2004 and again in 2006, the city contracted CIP rehab work to begin to stem the flow. More recently, it adopted regulations that require replacement of leaking laterals on private property when the pipes are 25 years old or older and ownership of a property changes hands or is significantly remodeled.

In 2018, flows sometimes reached 5.9 mgd — exceeding the capacity of the treatment plant. The resulting excess was only partially treated and subject to fines when discharged into bay waters. City officials weighed what to do. They first contemplated a complete makeover, with leaking pipes dug up and replaced. The cost of such a wholesale undertaking was pegged at $15 million.

In the end, officials opted to replace the worst of the pipe, insert a CIP liner in better sections of pipe, fix a slew of laterals and seal leaking manholes. That approach resulted in lining 7.5 miles of pipe and digging up and replacing 2,200 feet of clay pipe with North American Pipe’s PVC. Some 6,500 feet of lateral pipe was rehabbed — which involved work on 460 of the 4-inch pipelines — and 22 manholes were sealed.

That’s a start, Khatri says. “It’s a long process. There still are some areas with older pipe, mainly in downtown. We started this six years ago and have 50 more miles or so to go. But if every five years we’re able to do 8 or 9 miles, that’s a good achievable goal for upgrading the system.”

The city contracted the work to GR Sundberg, an Arcata general engineering contractor whose bread-and-butter work is underground, according to Casey Poff, project manager. While GR Sundberg has contracted with the city on numerous occasions, this project was the company’s first sewer lining and replacement job. GR Sundberg self-performed the excavation part of the project and subbed out relining to Quam Trenchless Technologies. Sometimes the dirt moving and pipe lining activities were going on at the same time in different areas.

The result was a hive of activity. Quam sometimes had a dozen people working on laterals, according to Judd Stattine, company president, while GR Sundberg had another 15-20 on site. A Quam subcontractor, Aegion Insituform, installed heat-cured liners in main sewer pipes, with another GR Sundberg sub, Michels, rehabbing manholes by spray-applying a SewperCoat PG sealant.

Challenging terrain

Though all this work essentially was confined to downtown and the Sunny Brae neighborhood, as a practical matter, crews were widely separated. To be more precise, about half of the work was concentrated on the east side of U.S. Route 101 and half on the west side. That gave the project a split personality. Poff says terrain east of the 101 is basically flat, while the west side has mountainous slopes and redwood trees. “Grade changes in the pipe were on the west side. That’s where roots disrupted things and pipes were broken.”

The west-side work also was marked by offsets in the pipeline. These developed when the pipe was improperly installed or the ground shifted, dropping or bumping up the end of a pipe and misaligning the pipe’s interior. The result is disrupted flow of sewage.

The offsets sometimes prevented relining. As little as a quarter-inch variation where pipes join can pose problems. The offsets also impeded the travel of inspection cameras “A 6-inch-diameter sewer line, which much of this line is, doesn’t have that much tolerance for large video equipment,” Poff points out. Khatri had anticipated maybe a dozen such misalignments, but the actual number turned out to be nearly 40.

“That was a surprise. It was way more than we had anticipated,” Poff says. Quam crews running video cameras through the line in prelining inspections sometimes failed to navigate these offsets. Meanwhile, Stattine doesn’t recall exactly how many times cameras got wedged inside the pipe, only saying that “based on how big the project was, getting stuck as many times as we did was within the parameters of what we could have expected.”

In most cases, the camera operators were able to extricate the equipment by pulling it back or otherwise wiggling it out of the predicament. Sometimes, however, a call for an excavator went out to Poff. “That was the last resort,” Stattine says of having pipe dug up. “It happens, and it will happen again.”

Poff agrees that getting stuck is one of the hazards of sending a camera into a pipe. “Especially at the beginning of a project when operators are feeling their way through and learning the limits of the cameras.” When he was asked for a rescue, Poff would send over a crew and one of the company’s Caterpillar 304 or 308 mini-excavators.

In each case, a 70 hp mini-excavator would unearth the line, take out the offset area of pipe and drop in a 2- or 3-foot PVC segment to smooth the transition between pipes and let sewage flow smoothly. Aside from these emergency runs, GR Sundberg routinely dug up pipe joints when discovered offsets measured 2 or more inches.

The Aegion Insituform subcontractor installing the company’s felt and polypropylene liner worked in pipe ranging from 6 to 15 inches in diameter. Mostly it was 6-inch, which made the work more difficult. “The biggest challenge was the small diameter of the pipe,” Poff says. “Tolerances were minimal. There was little room for error for the lining crew or for us.”

Stattine agrees: “Small-diameter pipe always presents challenges. And when the new lining is installed, the diameter becomes even smaller. When we went inside to make the lateral service connections, it was very tight.”

Schwalm USA cutter and reinstatement robotic machines worked in these claustrophobic conditions as they cut access holes in the pipe for T-Liner lateral connections. The LMK Technologies T-Liner phase of the job especially pleased Khatri. “We’re excited we were able to upgrade the lateral connections. In the old days, a lateral was just one pipe running into another, not even sealed. The lateral connection always is the weakest point in a system.”

Deteriorating lateral pipes frequently were dug up by GR Sundberg crews and a length of new PVC pipe inserted, on average about 20 feet. Trenches for the sewer main ranged from 3 to 6 feet deep. While trenches of that depth were easily excavated — and required minimal hydraulic shielding for safety — the shallowness of the water table in Arcata played havoc with digging in the wet winter months of December through March. “The work is pretty tough in winter,” Poff says.

 rchaeological supervision

Meanwhile, all the excavation work was performed under the scrutiny of archaeologists looking for artifacts of ancient Native American cultures that lived in the area. Wiyot and Yurok tribal members still live in and around Arcata, and the work area was considered archaeologically and culturally sensitive.

“They wanted to see what was coming out of the dirt,” Poff says of the watchers. Had they spotted something, the digging would have ceased, the discovered artifact evaluated and the project put on indefinite hold. To the relief of contractors, nothing was found to trigger that process.

With the first phase of the ongoing Arcata I&I project essentially complete, planning for the next phase begins. However, what can’t be planned for in this or any other Northern California sewer and water district is the possibility of an earthquake. When the earth shakes, bad things can happen underground. “Things are shifting all the time in the systems,” Stattine says of ongoing minor tremors in the region.

Khatri notes that the city’s old pipe, even when properly laid last century, is affected by subtle quaking in the seismologically active area. “Clay pipe comes in short sections, and even a tremor rated a 3 or 4 has an effect. You don’t feel it, but over a period of time, the pipe joints shift.” And when did the last tremor occur? “Last year,” Khatri says. “A 4-point-something quake was recorded last year.”



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