Bursting the Conventional Wisdom

An Oklahoma city is achieving success and saving big dollars by conducting a multi-year, $90 million sewer rehabilitation program with in-house workers
Bursting the  Conventional  Wisdom
Crew members Raymond Armstrong, foreground, and Justin Gilliland prepare for a sewer rehabilitation project by fusing lengths of sewer pipe using the McElroy TracStar 500 fusion machine. (Photography by Jeff Dixon)

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Faced with a consent decree from federal and state environmental agencies and a compliance program with financial burdens, the City of Lawton, Okla., looked inward for a solution that would allow the city to save money and still meet the regulatory agencies’ requirements for reducing sanitary sewer overflows.

The answer was a dynamic construction and rehabilitation program, using in-house personnel to design and perform rehabilitation for the city’s sewer infrastructure. Lawton has created a team that can compete with the private contracting sector along with a new mindset that has led to the city exceeding its production goals — reducing SSOs and inflow and infiltration (I&I) swiftly and beyond expectation, while saving millions of dollars.

Pipe bursting has been a key to the rehabilitation program, as its simplicity enabled crews to learn the technique quickly, and the process minimizes site disruption and the costs of surface repairs and restoration.


Due diligence

Lawton, in southwest Oklahoma with a population of 97,000, has 400 miles of sanitary sewers, mostly built from the 1940s to the 1960s. At the time, Lawton was home to two large concrete pipe manufacturing plants, and the community supported those businesses by installing mostly concrete sewers.

In time, hydrogen sulfide and aging began to contribute to numerous SSOs, putting Lawton on the radar at the U.S. EPA. In May 1995, the state Department of Environmental Quality (ODEQ) and the EPA issued a consent order for Lawton to perform a sanitary sewer evaluation study (SSES).

“The purpose was to identify repairs required to improve our collection system and to identify areas that required expansion as a result of undersized pipes in our collection system,” says Jerry Ihler, director of public works and city engineer. “The main goals were to eliminate SSOs, reduce I&I, and improve our pipes’ carrying capacity.”

The SSES called for installation of 37 flowmeters scattered across the city’s three large drainage basins, inspection of 6,000 manholes, and CCTV inspection of more than 111,000 linear feet of pipe. System modeling was performed on all of the city’s lines 10 inches and larger, and smoke testing was conducted on more than 75 percent of the system.

Once the study was complete, Lawton began negotiations with the EPA and the ODEQ, proposing a 21-year program in three seven-year phases, each covering one of the three drainage basins. The agencies accepted the proposal, but there remained the challenge of getting the engineering and construction done cost-effectively.


Cutting costs

In 1996, the program costs were estimated at $61 million, and that has grown to $90 million in today’s dollars. In anticipation of rising costs, Ihler was asked to see whether the city could do the work with in-house labor instead of contractors.

Ihler was skeptical, but he agreed to take a look. The SSES provided cost estimates, so Ihler and his team looked at places to trim costs. For one thing, the city did not have to earn a profit, and so if the crew could be as efficient as the construction contractors, there would be some automatic savings there, Ihler decided.

“We had established relationships with our gas, telephone and electric utilities, to where we thought we could get better response times from relocations or locates than a contractor could,” Ihler adds. “We also had a working knowledge of our system, so if there were going to be changes in the field, we could eliminate contract modifications and change orders and experience some savings through that.”

Altogether, Ihler and his team identified $2.6 million savings in the first seven-year phase of the program if the work were brought in-house. The program was funded through capital improvement budget dollars raised through a 1 percent sales tax and through several state revolving fund loans from the Oklahoma Water Resources Board, being repaid through a sewer bill increase of $2.35 per month per customer.


Setting the tone

Before work began, the organization needed a new mindset and approach. The sewer rehabilitation program had to mesh design with construction and required teamwork between those functions. In addition, maintaining a regimented production schedule would be a new challenge for city workers.

Everyone had to agree that the team needed to accomplish a specified amount per day and that work would not stop on a given day until that happened. It was essential to work that way if the city was to stay on schedule and remain in compliance.

“This was going to be a long-term commitment, financially for the city and physically for the employees,” says Keith Duncan, engineer for the Sanitary Service Technical Division. “We had to do our homework to make our case that we could do it just as well as a contractor. To be successful, we had to develop a solid plan, a business plan of sorts, because what we were about to do in essence was to set up a contracting business within the city.”

One way to keep production on track and on budget was to establish remote construction yards close to project sites instead of bringing crews back to the central yard each day and losing the production time involved in moving employees and equipment.

The team also changed the way budgets were viewed, abandoning the typical “use it or lose it” approach for a given year. The finance staff agreed to review yearly budgets based on actual production rather than on what was budgeted for the previous year.

Lawton also drew on the experience and expertise of the employees who had the most background in construction programs, selecting leaders based on ability to coordinate crews, boost efficiency, and achieve the most productive hours per day.

The crews also received support from management and the city council. Even when the powers that be did not understand fully what was being recommended, they accepted the team’s suggestions and allowed them to proceed.


The best fit

Lawton looked at a number of trenchless technologies for its rehabilitation program and settled on pipe bursting as the primary solution. “With pipe bursting we would be able to use conventional equipment and construction methods, avoid proprietary technology, and do it ourselves,” says Duncan.

“Bursting was attractive for its price point, but also because crew members and new hires who may have had limited trenchless experience could be brought up to speed quickly through manufacturer training and ongoing support from more seasoned personnel.”

Lawton equipped its crews with everything they needed for an efficient and effective program. Equipment and machinery included trackhoes, dump trucks, excavators and a variety of utility vehicles.

For pipe bursting, the city chose a variety of tools from HammerHead, an Earth Tool Company, including two HG12 winches on tracks, an HG20 winch, 7- and 8-inch air reverse hammers, and a 12-inch air impactor. This along with a 3650 boring machine from Vermeer Corporation, enabled crews to rehabilitate 8- to 20-inch lines. For larger lines, the city can rent bursting equipment as needed.

Lawton created many new jobs with its program: The city hired staff for four crews, each with six to seven permanent team members, and several temporary seasonal workers.


Pattern for success

Crews follow a set procedure to ensure that each rehabilitation project has the best chance of success. A typical project consists of one run from manhole to manhole, averaging 300 feet. The first step is to clear the right-of-way and locate and mark all utilities.

Bypass pumping is set up so that customers are never without service during a project, and access pits are dug for each service tap. A pre-bursting CCTV inspection pinpoints any issues — such as extreme sags — that may make bursting difficult or inappropriate. If possible, where sags exist, crews may open-cut that portion of the line to correct the grade and “grease” the pipes to smooth travel for the bursting head.

As the crews feed the lead winch cable down the line from the manhole entry point, the new HDPE pipe is fused and prepared. Once ready, the pipe is loaded onto the bursting hammer. The bursting equipment is then deployed. Once the pull is complete, the bursting head is cut off or removed in the manhole, the winch is cooled down, and the service connections are ready to be tied back into the new main.

At each service connection, holes are drilled and using electro-fusion equipment, a poly saddle is fused to connect the lateral to the main, creating a sealed connection. Once all the service connections are fused, the bypass can be removed and the line returned to service. The entire process for an average-size segment takes about one week. A final CCTV inspection is conducted for quality control.


Long-term vision

As Lawton winds down Phase II, the crews have completed the rehabilitation of 214,000 linear feet of pipe at 4,200 to 4,400 feet installed per month, about 63,000 linear feet above what the initial program had identified.

At the start of the program, Lawton was experiencing an average of 250 wet-weather SSOs. During the last year of Phase I, overflows were down 95 percent. Monitoring by a third-party firm has shown a 40 percent reduction in I&I, beating the goal of 25 to 30 percent.

By doing its homework and staying committed to its team, Lawton has proven that a small municipality can bring a major project in-house and compete on a cost and production basis with the private sector.


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