Wilmington, Del., was the first permanent Old World settlement in the Delaware River Valley. Discovered by the Swedes in 1638, it became the main port of America’s First State. Now the old city’s municipal sewer and water col­lection and conveyance system is showing its age, its earliest extant parts dat­ing from 1907.

Wilmington joins nearby Newark and Middletown in an area about a third of the tiny state’s size, whose sewer and water needs are served by the New Castle County Department of Special Services. Serving 118,000 sewer customers who generate 50-plus million gallons of wastewater daily, the county maintains more than 150 pump stations, 43,000 manholes, and more than 1,700 miles of san­itary sewer pipe.

Department Civil Engineer II Kevin Penoza is responsible for maintaining the aging infrastructure. He had to decide recently how to repair parts of the sys­tem, which began as vitreous clay pipe in 1907 but is mainly a post-WWII system updated from the 1940s to the ’70s. They began putting clay back in some areas along with other materials, creating a melange of pipe types to consider when planning repairs.

Big Problems, Limited Options

The oldest part of the system is in a gentrified neighborhood called Bran­dywine Hundred, covering about 10 miles from the Pennsylvania state line to Wilmington, between the Delaware and Christina Rivers and historic Brandy­wine Creek. Slicing through this narrow corridor is Interstate 95, the East Coast’s busiest roadway, juxtaposing pressing modern needs with the constraints of historic surroundings.

Inflow & infiltration issues were rampant here at the turn of this century, causing residential basements to flood and illegal surface discharges to local waterways during storms. The state Department of Natural Resources and Envi­ronmental Conservation (DNREC) issued a Secretary’s Order to Penoza’s depart­ment to eliminate these SSOs.

Such an order is roughly the state level equivalent of a federal consent de­cree, so a solution had to be found, and quickly. The high-traffic, historic locale meant projects would require innovative technologies to rehabilitate the sewer system as economically and with as little disruption of the activities and properties of residents and business owners as possible.

Inspection And Evaluation

The system was inspected with closed-circuit TV and meters installed at critical measuring points. Much of the capital program CCTV inspection is contracted out, but the county does most of the preventive work in-house. Its three CUES trucks are custom-fitted with Cobra Technologies cameras and data tracking software.
Once evaluations were completed, 60 structured overflows had been identified. Extensive observations revealed that rainwater and groundwater were entering the system through leaking collector sewer pipes and manholes, streams flooding over sewer manholes and cross connections to storm sewer pipes. Clearwater connections, including sump pumps, roof drains, punctured floor drains and foundation drains from buildings unlawfully connected to the sanitary sewer system were also major contributors to the I&I-induced capacity overflows.

Phased Plan Prioritizes Work

The result was the CSO Elimination Plan for Brandywine Hundred Sewer Rehabilitation, the goal of which was to reduce peak flow rates in the sewer system by 35 percent. The program prioritized problems most critical for flow conveyance, along with those determined to contribute the most inflow to system volume, in Phase 1. Four major sewer studies are ongo­ing now, informing Phase 2, which will take place from 2015 to 2018, continuing the effort in areas where sewer pipes haven’t deteriorated to a critical stage, but are still a measurable source of intrusion.

Phase 1 began in 2002 to eliminate or reduce the worst of the SSOs in the Brandywine Hundred neighborhood. This work is sched­uled for completion this year, but significant progress has already been made, with only 10 or 15 overflows still remain­ing. Areas outside the neighborhood had also been identified as needing similar attention, and would require something other than traditional dig-and-replace.

Mutually Beneficial Cooperation

Tom Wyatt, a consulting engineer with KCI Technologies Inc. out of Newark, Del., serves as a project manager on this comprehensive rehabilitation effort. He points out the special considerations of doing underground work in New Castle County, including the fact that many sewer lines cross major thoroughfares.
“Between I-95 and 495, there are 12 crossings just from Naamans Road to Wilmington. There are 12 on other parts of 95, and on 495 there are nine more,” Wyatt says. “For us to go and dig up everything would cost us a fortune, especially when you get into redoing the roads.”

So, Penoza explains, “Tom and I started a coordination program where DelDOT, which is responsible for all the road­ways, would provide us with lists of what roadways they were going to pave the following year. That would give us an opportunity to go TV all the sewer lines and try to make our sewer repairs before their contracts came out. With our repairs being already done, we weren’t digging up newly paved roads, which makes everyone happy. From the residents to the state representatives, coordination works and saves money.

“As a result of all that TV work, we were doing the traditional dig-ups needed, but we had started compiling lists of lines we knew we could rehabilitate trenchlessly. This was the first time we got the funding to start installing liners on some of the lines we identified as not needing to be dug up, but that were going to become problems down the road. So we’re able to rehabilitate them now.”

Neighborhood Considerations

One such area identified outside Brandywine Hundred was more of a residential neighborhood. “On this particular job, we bid 12,377 feet of 8-inch pipe, and 1,250 feet of 10-inch,” Penoza recalls.

These 52 sanitary sewer main segments were aging and deteriorated. All were suffering infiltration problems, some of them significant. The average length of each main pipe was 266 linear feet, with an average of seven to eight laterals per segment.

In the neighborhood setting, noise and traffic disruption were major considerations in choosing the rehabilitation solution. Trenchless was the only real option, but particular application packages weren’t completely nailed down in the bid request. However, one system — Blue-Tek from Reline America — had the advantage of requiring just two box trucks on site with a blower and a couple winches, whereas other systems would require boilers and additional equipment.
“When the bid went out, it was open to both heat-cured felt and ultraviolet-cured resin,” recalls Penoza. “Felt sys­tem installations create a lot more noise, and it can sometimes be difficult to get equipment into a backyard, so that is a huge advantage to a UV system.”

Wyatt concurs. “With UV, they can carry the compressor and winches to the manholes in the smaller sizes. I actually had kind of pushed the Blue-Tek a little bit. I’ve been to their plant. I like the process of the way resins are put into the fiberglass. I just think the product is a lot better. It’s a lot easier to work with, thinner, stronger and seeing the liner before curing with UV makes for a consistent liner application. We don’t have to worry about hydraulics and losing any kind of capacity. Also Reline America not only trains their installers, they trained our engineers and our inspectors. They also were present on the project periodically to help if needed.”

Demanding Specs

As it turned out, cost and written specifications were on Blue-Tek’s side. “I don’t know if there was another technology that could have met these specifications,” Penoza says. “Their resins are a little different.”

Wyatt explains, “By law, we had to go with the low bidder,” so the job went to Abel Recon of Mountville, Pa., a contrac­tor specializing in infrastructure rehabilitation.

Abel Recon’s project manager, Dustin Squires, took a crew out into the field to measure the actual “pull run” and depth of each pipe. Those measurements, along with pipe diameter and deterioration conditions, soil density around the pipe, the area’s water table, and intensity of infiltration, determined the design thickness of each liner.

“With this project, we went in using RA-75 for most of the 8-inch pipe lining,” Squires says. “We used a little bit of RA-120, primarily on the 10-inch pipe.”

In And Out

New Castle County set a 90-day time frame for completion of the project, which began the second week of June. “Most pipe­lines were in neighborhoods, so we had to be sensitive to the hours we worked,” says Hap Witmer, Abel Recon’s general manager. “Because some locations had quite a few laterals going into the mains, we had to make sure we had enough time to line the pipe and then reinstate all the laterals.”

The crew would show up on site around 7 a.m. with two trucks — one staged at the entry and one at the exit manhole. They would first set up traffic control measures, then reroute wastewater flow to bypass the pipes involved. They would TV inspect and clean the pipes, then install a slip sheet for the liner.

The liner was pulled into place with a constant tension winch and then inflated with a blower pow­ered by the service truck’s hydraulic PTO (power take off), the inner film acting as a bladder to hold the air and create the pressure needed to press the liner open against the pipe walls. The UV light train and bottom rollers were as­sembled and a pre-curing video of the formed, uncured liner was made and viewed to be sure the liner properly formed before curing. When everything was ready, crews fired up the lights, pulled the train through to cure the liner, and the inner “bladder” film was subsequently removed. By 1 p.m. they were usually restoring lateral services by cutting through the new liner with a Dominator 430 reinstatement cutter from Bowman Tool Company. Work stopped at 7 p.m. each day to prevent unnecessary neighborhood disruption.

Ahead Of Schedule

“One major advantage of the Blue-Tek system is its ability to be installed even while some dampness remains after cleaning, or a bit of infiltrated water remains in low spots,” says Witmer. “You can pull the liner in place and not have to worry about [remnant water] emulsifying or washing any resin out of the fiberglass, because it’s protected by the outer film.”

This helped the crews finish nearly 20 days ahead of schedule

There was one other major factor that contributed to such a smooth project: an on-site inspector who understood how the liner system design, manufacturing controls, structural design and construction controls work together to ensure that the as-built complies with the as-specified and results in a successful project.

“It’s a benefit because — especially when you’re doing your pre-inspection before starting the lining process — if you come across unforeseen obstacles like an offset joint or protruding lateral, we can discuss that with the inspector and decide whether it’s something we should still line,” explains Squires. “If the inspector’s there, it saves time.”

Witmer sees another advantage to having an inspector onsite. “With a new technology, it educates the inspectors and engineers by having them there to understand the good points about a product. They can also see for themselves that some of the problems we might have with it aren’t that big a problem, so they understand [the realities of the product]. It’s a valuable education for them.”

In fact, each use of such new trenchless technologies becomes a valuable education for everyone involved as they gain more experience and knowledge of improving tools of their trade. And the advantage accrues right down to the service customer, who may not fully comprehend the benefits of an effective solution to infrastructure issues that affect everyone’s quality of life.

More Information

Bowman Tool Company & Systems - 717/432-1403 - www.bowmantool.com

Cobra Technologies - 800/443-3761 - www.cobratec.com

CUES - 800/327-7791 - www.cuesinc.com

Pipeline Renewal Technologies - 866/936-8476 - www.pipelinert.com

Reline America, Inc. - 866/998-0808 - www.relineamerica.com