New water mains will cross Missouri, Sun rivers

A $5.5 million project begins Monday in Great Falls to bore water main pipe 100 feet beneath the Missouri and Sun rivers, the first time in almost a half century the city has installed a water main across the river.

The two new water mains will boost the city’s water supply but disrupt local traffic for a few weeks, city officials said.

“I haven’t seen a project of this scale in the city of Great Falls for a number of years,” said Rick Johnson, a civil engineer for the city. “This is something most of us haven’t seen.”

The city has hired HDD Company out of El Dorado Hills, Calif. to complete the horizontal directional drilling project underneath the two rivers that meet in the city.

A 24-inch pipe will be drilled 90 feet below the Missouri River.

The length of the drill is 3,600 feet.

That’s about the distance of 12 football fields.

“It’s what we do every day,” Neil Swope, president and founder of HDD, said of horizontal directional drilling. “We drill in places that cannot be trenched.”

Drilling rigs will be staged in Meadowlark Park on the west side of the river, and in Verde Park on the east side.

On the west side of the river, HDD will begin the horizontal drill under Alder Drive on the east end of Meadowlark Park, then cross under the southern end of Meadow Lark Country Club golf course, then the river.

On the east side of the river, HDD will cross under Upper River Road, the railroad tracks, Lower River roads and then the river.

“They will both be drilling toward the center of the Missouri River,” said Johnson said, with the horizontal directional drilling meeting under Park Island in the river.

The drilling rig in Verde Park will drill into a larger bore hole drilled from Meadowlark Park, Swope said.

“It’s known as an intersect,” Swope said.

“Once we’ve made the hole we actually pull the welded PVC pipe into the bore hole,” Swope added.

A pilot hole will be drilled first. That hole will then be made larger in a process called reaming.

As part of the project, periodic road closures will be necessary with the first being Fox Farm Road adjacent to Meadowlark Park.

Fox Farm will be closed beginning Monday and remain closed through Aug. 28.

“It’s not going to be any fun, guaranteed, but it’s necessary,” Public Works Director Jim Rearden said of the road closures.

Closing the street is necessary to connect the new 24-inch water main to an existing water main in Fox Farm Road, Johnson said.

United Materials of Great Falls is a subcontractor and will complete the “open cut water main work,” Johnson said.

“We need to get in and out of Fox Farm Road before School starts, which his Aug. 29,” Johnson said. “We have to dig across Fox Farm Road to make our connection. They will actually be digging all the way across Meadowlark Park.”

Meadowlark Park will be closed as well so it can be used as a staging area for assembling pipe needed to cross under the country club golf course and the Missouri River.

Once the bore underneath the Missouri is completed, work will begin on boring a 30-inch water main underneath the Sun River.

The route of the Sun River bore will stretch from a point near the Dairy Queen on Alder Drive and proceed north and under 10th Avenue South and the Sun River paralleling the 6th Street Southwest bridge before tying into a water main at 10th Avenue Southwest.

“It’s been a project that’s been looked at and recommended for a number of years and the funding has now just become available to do it,” Johnson said of  the Missouri and Sun river water main projects.

The new water mains are needed to ensure adequate water pressure and quantity for the expanding city, Johnson said.

“This will add additional capacity and what I call redundancy in the case of failures somewhere else in the system,” he said.

There are three existing water main crossings under the Missouri River and one under the Sun.

The first water main was installed in 1930. The last time a water main was installed was 1975. The 1975 water main was installed using a barge and excavator, Johnson said. To his knowledge, this is the first time horizontal directional drilling has been used to install water mains under the city’s rivers.

 “The environmental impact is quite a bit less,” Johnson said.

Fox Farm closure

Periodic road closures are necessary because of water main installations. The first will be on Fox Farm Road adjacent to Meadowlark Park. The closure begins Monday. It continues through Aug. 28. Meadowlark Park also will be closed.