Millsite Reservoir dam project moving forward

By PATSY STODDARD Editor

It’s a project that’s been talked about for many years and now it looks like it’s a go. The project to raise the Millsite Dam four feet and rehabilitate the dam to meet current dam safety standards is in the design phase. The funding for the project has been secured.
A monthly dam information meeting is held to keep all involved up to date on the dam project. Currently the Environmental Assessment is being prepared and will soon go out for a 30 day public comment period. The EA is currently in draft form and will be finalized soon. The county has signed an agreement to receive the funds for the project and to be the sponsor. The state can only release their funds to the owner of the dam which is the Ferron Canal and Reservoir Company. So the canal company will forward this money to the county. Funds will be paid for construction costs as well as engineering and analyst work along the way and any mitigation which must be done.
Mitigation work will be needed for Millsite State Park and the Millsite Golf Course. As the project moves forward concerns will be addressed for all those involved. The irrigators and the Hunter Power Plant will be impacted by the construction work. The reservoir will need to be lowered significantly for the rehabilitation work to take place. Irrigators will see impacts for two seasons. The time frame for the construction is estimated to be one and a half years. The design work is being done by Matt Call and Eric Dixon. They are looking at areas for borrow materials. The engineers have put together a conceptual schedule as follows:
The spillway approach excavation and spillway removal and reconstruction will begin in fall of 2016; during late summer and fall of 2016 the downstream slope excavation will take place as well as the foundation excavation and backfill with the foundation being backfilled in fall of 2016.
In the spring/summer of 2017 the new berm will be constructed. The downstream slope reconstruction will take place in the summer/fall of 2017. The outlet works extension will be worked on throughout the project with most of the work happening in the late fall and winter of 2016.
Raising the dam four feet will increase the storage capacity of the reservoir to return it to the original capacity. The intent of the project is to increase the safety to meet current dam safety and engineering performance criteria. The project will extend the life of the dam by 66 years. Ferron City receives their drinking water from Millsite Reservoir. The reservoir also serves as a recreation area for the community with camping, fishing and water sports at the Millsite State Park. Hunter Power Plant uses the reservoir for water storage for their power generation plants.
The dam provides flood damage reduction and sediment retention. The existing concrete box inlet spillway structure will be replaced with a concrete labyrinth weir structure with capacity to safely pass flows up to 31,000 cubic feet per second and raise the inlet elevation by four feet. Four feet of compacted earthen materials will be added to the top of the dam. A stability berm which is 102 feet wide by 35 feet tall by 1,500 feet long will be installed at the approximate northern half of the downstream toe of the dam. An additional 9,000 cubic yards of rock rip-rap will be added to the upstream face of the dam. Monitoring equipment will be added for long-term monitoring of the embankment material phreatic waterline. An auxiliary gate control will be installed for back-up of the existing gate operation. The project will extend the steel 54-inch diameter principal spillway outlet pipe 100 feet and rebuild the associated outlet works. The 8 inch diameter steel water pipe in the outer gallery will be replaced. This is the pipe used by Castle Valley Special Service District to deliver water for the Ferron City drinking water.
The project will involve excavation and reconstruction of the downstream face of the dam with earth fill and a new internal drain collection system and toe drain will be installed.
The Millsite State Park and golf course holes two, three and four will need restoration work done as a result of the work on the dam. This restoration work will be coordinated with representatives of Ferron City and the golf course personnel. Additional fill and a berm may be needed to protect the Millsite State Park from wave action during high water periods. Jonathan Hunt from Millsite State Park was going to take the engineers on a tour at Millsite State Park to confirm the potential impacts there and possible solutions.
At the Millsite Golf Course, hole three will be destroyed as work begins on the downstream face of the dam. Heavy equipment will fill the area with material stripped from the face of the dam while work on the internal workings of the dam is completed. A new hole will need to be constructed after the work is complete and sod may be used to get play back on the hole quicker.
Another issue for the golf course is if the other holes on the front nine will be accessible during the construction period. That isn’t known at this time.
There are also areas which will be used for storage of the rock materials pulled off the downstream side of the dam. Some materials may be stored within the reservoir itself as it is drawn down for the work.
Beginning next July the reservoir will be drawn down during the summer as much as possible to get as much work done as possible before winter. All the slope protection will be taken off. The internal drain system of the current dam does not meet current dam safety standards. The rehabilitated dam will have more support in the event of an earthquake.
The existing concrete spillway will be taken out and replaced with a concrete labyrinth spillway. It will be wider and deeper to allow for more water capacity during runoff events. To meet the planned schedule of this project, it’s possible the concrete work for the new spillway could take place in the winter.
Depending on how much work is completed before the spring, there will be a partial fill of the reservoir in 2017. During the majority of the foundation work in 2016 the reservoir will be taken to its lowest possible level.
The canal company and other waters users will revise how water is used from spring 2016-through July 2016 when the draw down will take place. Water will need to be rerouted during the construction phase.
Ferron Canal and Reservoir Company has a permit to dredge sediment from the Millsite dam reservoir. They are experimenting with this and hope to continue to dredge after the new dam is constructed to help slow the sediment accumulation in the reservoir. The issue they have had with the permitting is the turbidity downstream cannot be more than what’s coming into the reservoir upstream.
Tracy Behling the chairman of the Ferron Canal and Reservoir Company said they need to coordinate to use as much water as possible next spring. Coordination with the power company is essential to determine the most beneficial time for the power plant to take their water from Millsite. There will need to be cooperation between not only the Ferron Canal and Reservoir Company but the other canal companies as well to work around the water needs of the power plants.
“It kills us to run water downstream, but the benefits in the long run will be very good,” said Behling. “It will extend the (water) season by one month, it will bring opportunities that way.”
The Division of Wildlife Resources will adjust the fishing limits at Millsite as the time to lower the reservoir approaches. Justin Hart, aquatics manager said they might also use this opportunity to restore the Colorado cutthroat to the drainage a project they have been involved with for some time. The reservoir will be drained to a depth of about 23 feet. Once the foundation work is complete a partial fill could occur in the spring. If the new spillway is completed the first winter a partial fill could occur in the spring. The project will have a manager who has not been named at this time. The contractor will go through this person. Someone will be there all day all the time to manage and deal with issues as they come up and to keep the contractor on schedule.
Jay Mark Humphrey expressed his concern the project has a short timetable of a year and a half to completion.
Dixon said that is an accurate timetable based on their best estimates of the project scope. Dixon said they will issue a weekly report to all entities involved for the weekly progress once construction begins. They will also look at the option to keep their website updated with pictures and reports on the project.
The county will take care of the paperwork for the project and pay the bills incurred. The selected contractor will need to put up performance bonds and there will be deadlines for each phase of the project. These are motivators for contractors. There will be a required site showing for contractors and contractors wishing to bid must prequalify.
Total sponsor cost for the project is: $9,800,000; federal cost is $18,200,000; total project cost is $28 million. Funds from the state of Utah included in the sponsor cost are $8,820,000. Bidding for the project will take place in spring 2016. Bronson Smart said, “This is a neat project for this area. The canal company has done a great job of taking care of Millsite.”
Laren Huntsman, plant manager from Hunter wondered if there are steps the power plant should be taking now to more effectively use the water available at Millsite Reservoir before the reservoir is drawn down. There will be a meeting after the next dam meeting to discuss what can be done now to utilize the water at Millsite Reservoir. He also suggested building all of the outworks back to the existing structure and then making those connections. Dixon said they would speak to their consultant about that.
Behling said they have talked to the irrigators and they would like to continue watering into November this year to use more of the water. Temporary connections will have to be maintained throughout the project to keep Ferron City in water. Cody Allred from PacifiCorp asked that at the next meeting a timeline and schedule be ready to identify times when water would not be available for use at the power plants. BLM representatives said that since the NRCS is conducting an EA for the rehabilitation of the dam that they use what areas they need to complete the project. The BLM has surveyed 10-12 acres in the area.
The next dam meeting will be on Sept. 28 with the meeting consulting with water users directly after.