Leavitt expansion reaches halfway point

About halfway through its two-year construction timeline, the engineers and contractors tasked with completing the $78 million Leavitt Reservoir expansion say they are pleased with the progress that’s been made so far and plan to work through the winter.

“(The contractors) are not expecting to do a complete shutdown of the project, but when it’s too cold, they might stop temporarily, and they’ll have much smaller crews,” said Kevin Mininger of RJH Consulting, the engineering firm coordinating the project for the Shell Valley Watershed Improvement District. 

“Their plan is to get the tower done this winter, so it’s at full height and all the concrete work is done, and they’ll also be working on the pipe coming off the tower that goes through the flow meter vault and ultimately back into the creek, assuming the weather cooperates.”

Mininger visited the construction site last week, not only to get a first-hand look at the progress but also to meet with officials from the Wyoming Water Development Commission, who were expected Wednesday, Nov. 20.

While cautioning that the actual numbers vary depending upon what activities are happening, Mininger estimated the size of the workforce at between 55 and 60 working onsite and in offices offsite, with 40 of them connected to the joint venture of Montana Civil and Big Sky Civil, another 12 with Mountain View Builders and six with RJH Consultants/Stantec.

Montana Civil and Big Sky Civil are carrying out the $36.4 million Contract A (construction of the dam, outlet works, wetland mitigation area and recreational facilities) and the $17.9 million Contract D (production of aggregate materials from the terrace borrow areas).

Mountain View Builders secured the $8.6 million Contract B (construction of supply pipeline and associated structures) and the $14.5 million Contract C (construction of transfer pipeline and diversion structure).

Peering out over the construction activity, Mininger said in an interview Tuesday, Nov. 20 that construction of the tower and outlet works for the piping to get water out are ahead of schedule, but that the earthwork is a little behind.

“The original plan was to be at this elevation by the end of October, rather than the by end of November,” he said. “We gave them another 30 days.  Besides trying to keep things moving along because whatever they don’t place this year they will have to place next year, there is also a technical reason because the materials we are using are clay and high plastic clay that’s common out here needs to sit over the winter to give that material a chance to consolidate so it can gain some strength.

“As the excess moisture comes out of the material, it gets a little stronger, and that needs to happen so that by next spring, it’s ready to take the next 65 feet to get to the top.  That’s about what they’ll have to do next year.  The crest elevation is 4,860 feet; when they’re done here, they’ll be at 4,790 or 4,795 and will have about 65 or 70 feet to go.”

To the north and the east, meanwhile, “the supply pipeline is in the ground and they are working on the diversion structure off Beaver Creek.  That supply pipeline will take water from Beaver Creek to the wetland mitigation area.  There will be some outlet structures to work on up there. The reason for that, one, we had to build 20 some acres of wetland to mitigate what was lost, and two, by putting water in there first, it allows some of the larger sediment to settle out before it enters the reservoir, improving water quality.”

Mininger said the contractors are tentatively planning to ramp up the work rate around April 1.

This summer, crews were routinely working 10-days-on, four-days-off shifts; this fall and before the time change, they were working 7 a.m. to 7 p.m., six days a week.

Mininger said the filling of the reservoir may begin in the winter of 2025-26, “if there’s enough water,” but most of it will happen with the spring runoff.  Whenever that time comes, expect a very deliberate process.

“The first filling of any dam is a controlled fill,” Mininger said. “We limit how fast it fills — usually it’s about a foot a day, then every so often, like once every 10 days, we stop filling it for a few days to monitor it and make sure the dam isn’t moving or doing anything it shouldn’t do. That first year, it may not completely fill.”

Mininger said the project is about $1 million under budget. “With the change orders and things we’ve done, the current contract  prices are actually lower than the awarded prices.  The contractors have been a big part of that, identifying potential opportunities to reduce the price and improve their efficiency.”