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From Sub-Par to Superior Water

From Sub-Par to Superior Water

Photo courtesy of Great West Engineering

HDPE Pipe Now Carries Clean Potable Water To Rural Montana Communities 

HARLOWTON, Mont.- For nearly a century, a group of communities in central Montana have struggled with poor water quality.  Served by a variety of surface and groundwater sources, including a well drilled into an abandoned mine shaft, residents experienced firsthand the impact of water laden with minerals, total dissolved solids (TDS), and metals such as iron and manganese. 

Although drinking water in these communities met federal water quality standards, it was aesthetically unpleasant and generally considered to be unpalatable by residents.  Some homeowners resorted to installing water softeners and reverse osmosis filtration systems, and many reported having to frequently replace appliances like hot water heaters because of corrosion.  With the added challenge of intermittent drought conditions that affected the amount of available water, regardless of its poor quality, these central Montana communities were in dire need for a new source of drinking water.

Planning for the Future

The Central Montana Regional Water Authority (CMRWA), a coalition of eight incorporated communities, several unincorporated communities and many rural families in central Montana, was established in 2004.  Its purpose was the realization of a regional water project that would address the long legacy of water quality and quantity issues that had plagued these rural communities.

After 15 years of planning, environmental assessments, feasibility testing, and funding applications, the Musselshell-Judith Rural Water System (MJRWS) project received federal authorization in December 2020.  Drawn from deep wells, – some nearly 3,000 feet deep – high-purity water from the Madison Aquifer will flow to communities through some 230 miles of transmission pipeline.  Water from the new source is of such a high quality that it will require no treatment other than chlorination.

Photo Courtesy Curt Wood, C&C Excavation

Coming to Fruition

Construction of Phase 1 of the MJRWS project concluded in August 2023.  In addition to a new wellhead, a partially buried 560,000-gallon storage tank, and chlorination building, Phase 1 included the construction of approximately 24 miles of HDPE distribution pipeline that will deliver much-needed clean drinking water to the town of Harlowton, Montana., as well as other rural users along the route.

One of the early decisions that needed to be made was the type of pipe material that would be used to convey drinking water from the new source to end users.  “This area has a lot of very corrosive soil,” explained Bob Church, senior project engineer with Great West Engineering, the engineer of record for the MJRWS project.  “So, the project is designed to absolutely minimize the amount of metallic pipe in it.”

Selecting the Pipe Material

According to Church, the choice of pipe really came down to two options: polyvinyl chloride (PVC) or high-density polyethylene (HDPE).  Although the project was originally bid with PVC in mind, the compelling advantages of HDPE had to be considered.  “My project engineer, Susan Hayes, who I’ve worked closely with on the project, believed the combination of ease of installation, durability of the pipe, and the fact that it would be cost-competitive to PVC made HDPE the better choice,” he said. “So, that’s what we selected.”

Ultimately, the project specifications for Phase 1 of the MJRWS called for a total of 125,042 feet of 10-inch and 18-inch HDPE pipe in a combination of IPS (iron pipe size) and DIPS (ductile iron pipe size) sizes and Dimensional Ratios from 9 to 13.5.

“Rural communities are by the very definition in areas that are isolated and many times do not have access to basic necessities such as clean potable water,” stated Camille George Rubeiz, P.E., F. ASCE, co-chair, HDPE Municipal Advisory Board, and senior director of engineering for the Plastics Pipe Institute’s (PPI) Municipal & Industrial Division.  “Now, there is a great push to rectify that problem even it is means conveying water many miles.  And the use of HDPE pipe makes it practical and economically feasible.  The projected service life of a 100 years, leak-free joints,  plus the pipe’s ability to tolerate freezing temperatures, ground movements and withstand corrosive soils is well known.  All of which are important for any project and especially critical when your installing 24 miles of pipe 30 feet underground in rugged country”  PPI is the major North American trade association representing the plastic pipe industry.  The pipe on the Musselshell project comes from WL Plastics (Ft. Worth, TX), a member company of PPI.  

Labor and Safety Benefits

Putting pipeline in the ground is no easy task; it’s a difficult, time-consuming, and can be a hazardous endeavor.  Using HDPE on the MJRWS project simplified the process while keeping workers safe.  “The bidding requirements for HDPE are significantly less than for PVC,” explained Church, “so the workers don’t need to be in the trench as much.”  That was an important consideration, he said.  “We are horizontal drilling things like stream crossings,” Church explained, “and we’re boring under all wetland and county road crossings, but the lion’s share of the project is open cut.” 

Unlike PVC, the vast majority of HDPE installation work – heat fusing the sections together – is done aboveground.  “The contractor keeps his crews up on top,” explained Scott Peters, HDPE specialist with distributor Core & Main. “They fuse the pipe and then drop it down the hole using their machinery.  They don’t have to worry about anything caving in on them.” Crews only need to descend into the trench occasionally to install valves, he added.

Photos Courtesy Curt Wood, C&C Excavation

The contractor for the project, C&C Excavation Inc. (Havre, Mont.), has been installing HDPE for more than 20 years.  “That’s why we were attracted to this project,” said Curt Wood, owner of C&C Excavation.  “We’ve laid so much of it, and we realize the savings on labor and the liability because nobody has to get in the trench to stab pipe.  That’s the great advantage.”

Tough Soil, No Problem

Wood said the trenches on the first phase of the MJRWS project ranged from about eight feet on the 10-inch pipe to about nine feet on the 18-inch pipe.  “And we had to maintain six feet of cover,” he added. 

The soil could be challenging at times.  “We didn’t find any really good soil — I’ll put it that way,” he noted.  “We had about five miles of what’s called cemented gravel, which is excavatable 

but slow.”  His crew, which numbered about 14, also ran into some limestone.  “We ended up having to use a hydraulic jackhammer on that,” he said.  When working in the rocky soil, Wood said they padded the ditch bottom with select material, “and then we bedded it or shaded it with that same material to protect the pipe,” he added.

Crossing the Streams

The crew also crossed several wetlands and three creeks, Wood said. “The lengths varied, but we had one 900-footer and one 700-footer — and we had them all the way down to 30 feet.”  For the crossings, they used directional drills with pulling heads they had built and welded on to the end of the pipe.  “We would drill it and then back-ream it to get our opening larger than our pipe.  And then we’d go back through, grab our pipe and pull it through,” he explained.  The bore holes had to be 18 inches for the 10-inch pipe and 24–30 inches for the 18-inch pipe, depending on the soil type and the length of the bore, he explained.

C&C Excavation used three different drills, all Vermeers.  The smallest, which was used on a lot of the 10-inch pipe, is a 24 x 40, Wood said.  “We also have a 50 x 100 that we use on the bigger, shorter runs,” he added.  The crew’s biggest drill is a 100 x 140, which is rated for 100,000 pounds push/pull with 14,000 pounds rotational torque.

Fusing the Pipe

Peters explained that up to 2,000 feet of HDPE pipe at a time can be fused aboveground before it’s lowered down, which speeds up installation time significantly.  “You can then hook onto 

it, drag it to where you need it to be, and do your tie-ins,” he said.  It’s such a quick process that production can be 20 percent faster with HDPE than with PVC, he noted.

For the fusion process, Wood’s crew used several different machines. “For the 10-inch pipe, we used the two smaller machines we have a McElroy 412 and a 618,” Wood said.  For the larger pipe, they used two McElroy TracStar® 630s — one they own, and the other they rented.

“We had days where the contractor put in over a mile of pipe in a day,” Church exclaimed. Granted, it is a rural area where there isn’t much traffic to contend with, “but given the size of our 18-inch pipe, it was still quite remarkable that we could install the pipe that quickly,” he added. 

Cost Savings

In addition to the ease and speed of installation, HDPE pipe delivered cost savings on the MJRWS project.  Contributing to the cost-effectiveness of the HDPE was the experience of Wood’s team. “We’ve been doing it for so long and we’ve done so many projects that our footage adds up to where we can meet the qualifications to do the welding ourselves.  We don’t have to sub that out to somebody else,” he said.  “And, we bought our own boring machine so we don’t have to sub that out either.” 

Furthermore, because of HDPE’s pliability, it requires fewer fittings.  “There are a lot of instances where, rather than putting in a fitting, HDPE can bend,” Peters explained.  “PVC is rigid and wouldn’t necessarily be able to make that same bend.  So, with HDPE, we’re able to save quite a few dollars just in fittings.”

The flexibility of HDPE provides other advantages as well. “If the ground starts to shake or move or bend, the pipe will go with it,” Peters explained.

Dependable and Leak-free

Perhaps one of the most compelling features of using HDPE on a water distribution project like MJRWS is that it doesn’t leak.  “It’s all fused together,” Peters pointed out, “so it’s a no-leak system.”

Usually on water distribution projects, there is some sort of “snafu” — a joint or fitting that leaks — when pressure is first introduced to a main, Church said.  “But we recently did our first pressure test on three and a half miles of Phase 1,” Church said, “and it passed the first time!”

“It’s failsafe,” Wood added. “As long as you’ve got good welds, nothing goes wrong with HDPE pipe.”

Very soon, the first phase of the MJRWS project will be delivering fresh, clean drinking water to residents eager to receive it, and Phase 2, which will comprise another 65 miles of HDPE pipe, is underway. 

Peters noted that the MJWRS project exemplifies the benefits of using HDPE pipe.  “It checks all the boxes,” he said.  “Price, cost and ease of installation, no-leak system, 50-to-100-year life.  I think if we were going to explain to prospective customers why HDPE should be used, we would drive over to this project and say, ‘Here it is.  This is why we use HDPE for our water systems.  It’s perfect.'”

Additional information can be found at the Plastics Pipe Institute’s website www.plasticpipe.org/MABpubs