SEWER: Around and Under

Horizontal directional drilling helps the Ogunquit Sewer District work around challenges of tourists, tides, and environmental restrictions.

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Ogunquit is a seasonal resort town on the coast of Maine, but its sewer district faces some big, non-seasonal problems: relentless tides, environmental challenges, and older infrastructure.

Since the Ogunquit Sewer District is considerably older than much of the town, which was incorporated in 1980, many pipes pass directly under major hotel and housing developments, as well as other utilities.

The town’s tidal locations mean that environmental agencies closely scrutinize any work on the system. There is even an endangered bird nesting area in the seawall dunes, affecting the window of time in which some work can be done. That window is already constricted by weather, tides and the tourist season, reports district superintendent Phil Pickering.

The district also has major seasonal problems with inflow and infiltration. Storm events over four or five inches — which include Maine’s famous nor’easters — cause trouble. In addition, tourist season drives the district’s flows from the normal 300,000 gpd to 800,000 gpd.

In the face of these and other challenges the district uses horizontal directional drilling (HDD) aggressively for line installations and replacements. The town also keeps current with other modern technologies and techniques, notably geographic information systems (GIS).

Small but challenging

The district’s staff of seven serves 1,700 accounts and manages a modest amount ­of pipe — about four miles. Much of that lies within tidal flats, and some runs underneath a tidal river. The area is drained by the Josias and Ogunquit rivers. The town’s 3.5 miles of beach and dunes form a barrier peninsula, connected to the mainland by bridge.

“The district got started with town-owned sewer going back to the 1930s, so we still have some pipe going back to the 1940s, mostly clay tile,” says Pickering. “We also have a lot of ductile iron.

One factor working in the district’s favor on directional drilling projects is favorable soil conditions. “There’s marine base clay at 30 feet, and other than that we’re usually dealing with sand,” Pickering says. “Clay works well because it holds drilling fluids. Sand is also pretty good, but you have to be cautious of frac-out, and cleanup costs are higher.” (Frac-out is the forcing of drilling fluids out of the drilled hole).

HDD got started in 2004, when the district sent a 900 foot “shot” under the Ogunquit River. Another project in 2005 that showed the promise of HDD took place in 2005 involved replacement of a segment of force main with 8-inch HDPE.

“Directional drilling was the obvious choice for that project,” says Pickering. “The old cast-iron pipe installed in the 1960s was deteriorating, and we needed to increase capacity. We could excavate to put in new pipe, but the system had to remain in service, and that made pipe bursting impractical, too. A long bypass system would have been necessary, and that would have been very costly.”

The only way

Ultimately the district completed a 1,100-foot shot that passed under a bridge, several utilities and a 16-inch sewer main, and around a hotel pier and rocky outcrops. “HDD was really the only way to do this job,” says Scott Kelly of Enterprise Trenchless Technology Inc. (ETTI), the district’s contractor.

“Other alternatives would have been extremely time consuming, costly and disruptive. Not one single house, business, or utility was disrupted as a result of our operations.” The firm used Ditch Witch HDD equipment.

Even though it went smoothly, the project was challenging, even by HDD standards. A stone pad had to be constructed in a tidal area to support the drill rig, and work had to be scheduled to take advantage of low tides. But the bottom line is that HDD pulled off a project that might have been impossible otherwise.

The district’s most recent project, replacing more than a mile of ductile iron force main with 10-inch HDPE, represents Phase Two of a project that began in 2005. “We’re doing this because we have concerns about the older force mains,” says Pickering, “It’s an old cast-iron line, and we hope to get it replaced before it fails. It’s also a bottleneck in the system.” That stretch of pipe handles about 80 percent of the district’s flow and is a major source of I&I.

Environment friendly

A main benefit of HDD in this case is the avoidance of environmental restrictions, as much of the new pipe has to pass through tidal areas and across a river. “We don’t believe we could have gotten permitting for another approach,” says Pickering, “But doing it this way, we didn’t have any permitting problems.”

HDD shots for this project were as long as 1,800 feet. Locating for the project had to be done between tides, and there were other challenges as well. “We had to construct a gravel road to get support equipment to the site,” says Kelly, “and we used a footbridge that spanned a river to transport water and slurry to the drill from a remote parking lot.”

The project’s first phase passed final testing on a Saturday and was flowing the next day, just in time for an extremely high tide and nine inches of rain on Monday: “This line couldn’t have come at a more crucial time,” said Kelly.

Initial plans for the project called for even longer shots. Load calculations showed that pressures would be very close to safe limits for 10-inch HDPE. The district hired a consulting engineer to reroute the HDD shots. “His calculations were nearly perfect,” says Kelly, “and saved damaging the pipe on final pullback. The engineering paid huge dividends on this project.”

Preparing for tourists

Summer tourist season always challenges the district staff. “For one thing, it would not be advisable to close any streets between Memorial Day and Labor Day,” says Pickering. “That means any construction has to fall outside the most convenient work period.” Grease is also a problem.

“We’ve always had a bit of a grease issue, probably because we have 55 restaurants in our district,” Pickering says. To mitigate those issues, Ogunquit passed a grease ordinance that gives the district a way to work with restaurants.

“We’ve been picking away at the problem,” says Pickering. “We require grease traps, and we require inspections to make sure that they’re installed properly. We also work with the restaurants on maintenance and cleaning issues, and we require them to keep records, which we collect each fall.”

In the weeks before tourist season, the district gets ready by conducting a massive spring cleaning. “We spend quite a bit of time in spring making sure that all our lines are cleaned out and that we have no grease issues,” Pickering says. “At the treatment plant, we go over pumps and other equipment to make sure we have maximum capacity. In-house, we’re getting all our tanks cleaned out and online, and we’ll check details, like making sure that air diffusers don’t have algae buildup. It’s like getting ready for battle.”

Using technology

Other equipment used by the district includes a John Bean 2,000 psi/75 gpm waterjetter with 600-gallon tank, an Aquatech JV1000 vacuum truck, a Thompson portable pump, and an a Silver Bullet mini-crawler camera from InsightVision.

“We’ve only had the track camera about a year,” says Pickering, “and so far we’re using it reactively, taking it to problem areas. I don’t really like that, and we’ll be using it more proactively, on a schedule, soon.”

In addition to grease, the staff encounters roots. “Lately, we’ve found a lot of areas invaded by roots, particularly in the areas where we still have a lot of clay tile in use,” Pickering says. Rather than use chemical root control, the district replaces root-bound pipe with new HDPE for a more permanent fix.

The district’s GIS is about a year old, built on ESRI software and laid over recent 6-inch pixel, high-resolution orthophotography (each pixel in the final images translates to six inches on the ground). All manholes are located, either by orthophotography or by GPS. Information tracked includes line sizes, types of inverts, slopes and rim elevations.

Other information, such as property lines and ownership, was provided by the Town of Ogunquit in exchange for access to the orthophotography — a trade that worked out well for both parties.

Close collaboration

To get an idea of what kind of system he wanted, Pickering cooperated with the nearby towns of Westbrook and Sandford, which consulted with him on GIS design. The district is working on including video footage of pipelines, cleaning and repair status, and information from two Flo-Tote flowmeters, which are used to investigate I&I issues.

“We’re still working on issues with our IT guy, and I’m very hopeful that we’ll be using it much more than we are now,” says Pickering. Eventually, the GIS will be used proactively to schedule maintenance and repair.

The flowmeters are deployed as needed to investigate I&I issues. They were immediately helpful in discovering areas where infiltration groundwater was leaking into pipes. They also helped the district find residential and commercial sump pumps that were illegally tied into the sanitary sewer system.

The wastewater needs of even a small community require dedicated, skillful, and an imaginative staff. The Ogunquit Sewer District is doing what is necessary to get the job done. By recognizing and adapting to the special challenges of the tourist season, the district keeps service reliable, without keeping excess capacity in place year-round.

By using horizontal directional drilling skillfully, the staff can complete even huge projects that can be worked on only in the off-season. The people of Ogunquit — especially the “summer people” — benefit greatly from the district’s aggressive, innovative use of this and other technologies.



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