A Coordinated Effort Saves Money for Moorhead Public Service

In-house crews and careful planning lend efficiency to Minnesota utility’s main replacement program.

A Coordinated Effort Saves Money for Moorhead Public Service

Lead heavy equipment operator Chris Perlichek changes out a hydraulic plate compactor for a breaker hammer as equipment operator Shane Werre prepares to break sections of a residential street. The two were part of a crew responding to a residential water main break. (Photography by Brad Stauffer)

Interested in Infrastructure?

Get Infrastructure articles, news and videos right in your inbox! Sign up now.

Infrastructure + Get Alerts

A well-thought-out approach to water main replacement is saving money and minimizing  disruption in Moorhead, Minnesota.

The Moorhead Public Service utility works closely with the city of Moorhead to plan replacement of the aging cast iron pipes in its 220-mile distribution system, applying a variety of trenchless technologies and doing much of the work itself.

“We meet every summer with the city to go over its capital improvement program,” says Kris Knutson, MPS water division manager. “We focus on the city’s transportation projects and identify roadwork plans in locations where we have old cast iron pipe that needs replacement or where we’ve experienced main breaks.”

Using this coordinated approach, MPS rehabs or replaces 8,000 to 9,000 feet of cast iron pipe in its system each year, using trenchless technologies for about half the work. The trenchless techniques include horizontal directional drilling, pipe bursting and sliplining.

A unique approach to resurfacing entry and exit pits and other opencut areas yields additional savings.

“We resurface the bottom 4 inches of the area above our excavations,” says Jake Long, water distribution supervisor. “We leave the top 2 inches to the city because they are going to mill and overlay that area anyway.” 

Managing assets

A consumer-owned electric and water utility, MPS provides drinking water to more than 46,000 customers in Moorhead, Oakport Township and the city of Dilworth — part of the metropolitan area of Fargo-Moorhead, which has a combined population of approximately 209,000.

The water system has undergone more than $20 million in improvements since 1986, including the completion of a state-of-the-art water treatment plant in 1995. The plant includes lime water-softening, filtration and ozone for primary disinfection and odor/taste removal. The upgrade has significantly reduced the generation of chlorinated disinfection byproducts. Raw water comes from the Red River of the North, as well as three local aquifers.

The replacement work is performed according to the Watermain Asset Management Plan that MPS started using about five years ago, Knutson says.

The goal of the plan is to provide a safe and reliable water distribution system by strategically replacing cast iron as well as undersized mains to meet flow requirements, through coordination with the city’s road construction plans.

“We generally meet with the city during the summer prior to the next round of work,” Knutson says. “We work cooperatively with the city, using the transportation projects in its capital improvement plan for the coming year.”

MPS begins its water main replacement program in April, completing it in early August — in time for the city to wrap up its street work before winter.

Long says breaks often indicate areas where work is needed. “We don’t use a specific leak detection technology.” Rather, the clay soils in the area cause water to bubble to the surface, allowing the MPS team to visually spot main breaks.

GIS data help identify “hot spots” and other areas needing replacement, based on pipe material and pipe conditions, as well as break history.

Since 2013, MPS has replaced an average of approximately 8,500 feet of its 30 miles of cast iron pipe each year. “We are optimistic that we can replace all 30 miles by 2035,” Knutson says. Much of the cast iron pipe was installed in the 1950s and ’60s, with some dating back to the early 1900s.

Before adoption of the asset plan, the utility was replacing significantly less than 1% of its cast iron a year — a schedule of replacement that exceeded the design life span of most materials. Under the asset plan, the cycle is about every 100 years, more in line with the PVC pipe being used as the replacement.

Knutson estimates a little more than half of the work will be done with trenchless techniques and the rest by opencut excavation. “It depends. If the city is replacing an entire roadway, then we’ll use the opencut approach.”

If the city is completing a mill and overlay, typically HDD or pipe bursting is used. The choice between HDD and pipe bursting depends on the location of conflicting utilities, Long explains. “If we like the location of the pipe (meaning there are no other utilities interfering), we’ll use pipe bursting. If we need to place the water main in a different location to avoid existing utilities, we’ll choose HDD.” For transmission mains, “where the pipe size can be downsized, we’ll use sliplining, but that’s more on the transmission side than the residential side because there are not as many individual service lines to reconnect.”

In-house replacement

While close coordination with roadway construction is proving to be cost-effective, MPS saves additional money by doing a large portion of the water main replacement with its own crew.

Long estimates that the utility does about 50% of the work, contracting out the other half to local contractors.

“Our crew of six to eight labor/equipment operators is experienced,” he says. “Many have a strong background in the construction industry, so they are knowledgeable and familiar with this type of work.”

MPS provides training, as well. And Long adds that many of the local organizations offer training and seminars in pipe-laying certification and appropriate safety measures.

“We have a great team that is knowledgeable and works hard. Over the past several years, MPS crews have learned various tactics to become more effective and efficient using trenchless technologies. We continue to learn and improve each year.”

Sharing success

Several recent projects were featured in a paper MPS, Underground Solutions and Apex Engineering Group staffs presented at the North American Society for Trenchless Technology conference in Chicago in March 2019, and they represent the range of work the utility is undertaking.

One major job involved the pavement mill and overlay of two state trunk highways and the main street in the middle of town. Trenchless technology was included in the bid package, and the utility was able to use HDD to replace 4,000 feet of cast iron pipe with 8-, 10- and 12-inch fusible PVC pipe.

“The fact that the roadwork was mill and overlay versus full-scale reconstruction made trenchless construction of the water main an ideal fit,” the authors of the paper report. The approach diminished disruption of traffic in the busy downtown area and allowed MPS to piggyback on the road project, saving on the design, permitting, traffic management and construction administration costs.

In another project, MPS had experienced a number of breaks in a 1,200-foot section of water main along Sixth Street, as well as sloughing of iron deposits. Before the city began a total reconstruction of the street, MPS was able to execute a pipe bursting project, doing 300-foot pulls that took between three and five hours each.

Costs were kept at approximately $80 per foot since MPS did not have to replace any asphalt at the pipe bursting connection pits because the city fully restored the road surface following pipe replacement. “For a time, the pavement levels are different and we post uneven pavement traffic signs to warn drivers,” Long says.

Finally, in a project in a densely populated residential area in the southern part of town, MPS used pipe bursting to replace 3,300 feet of 6-inch cast iron pipe with 8-inch fusible PVC. Because the project was coordinated with an upcoming mill and overlay of the street, MPS achieved significant savings on the cost of patching the many service connections that were required in this densely populated area.

“Contractors were given the choice between opencut excavation and pipe bursting,” the NASTT paper reports. Trenchless was chosen due to the high cost of gravel and asphalt needed for roadway repairs with opencut.

Pipe was pulled in three- to five-hour periods during the early morning to allow residents access to their driveways.

Again, coordination between the city and MPS proved cost-effective.

Close coordination

Replacing the aging infrastructure across the nation represents a huge investment of funds that are not always available from government or that require significant water rate increases that must be borne by customers.

At MPS, the use of trenchless technologies and close coordination with the city’s road construction projects is turning out to be highly cost-effective.

Knutson estimates that the average cost per foot of replacing water mains is around $165. By coordinating the replacement with the city’s roadway projects and leaving the top 2 inches of the entry and exits pits for the city to resurface, that cost has been reduced to around $135 per foot. That number can come in even lower when the utility does the replacement work itself.

The utility’s Watermain Asset Management Plan is paying dividends.


Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.