The Millsite Dam rehabilitation project is moving along towards completion this winter. The project took a month’s hiatus when cracks were discovered in the concrete. The cracks were in the intake structure as well as the walls and floor of the spillway.
Eric Dixon said, “It was the day after our meeting with the media in May when we discovered a design issue. The concrete design didn’t have enough steel to allow for shrinkage and temperature. Structurally the concrete was fine.
“There were not enough steel bars to reduce the cracking. The cracks went all the way through the walls. The concrete met all the structural requirements. We have been working on how to address the cracks. We were ready to backfill at the spillway and the outlet works.
“The question was what do we do with the concrete that’s already been installed. What do we do with the areas waiting for backfill. We have to make sure the concrete has the right design and we needed to address the cracks.
“A waterproof coating has been applied. It has to dry before backfilling can take place. The product is called Xypex. It is a water proofing for cement. The workers have applied the product, you rub the mixture on the surface and it is absorbed into the cracks where crystallization takes place. You coat the entire wall with a brush. First the concrete was cleaned really good. There is a curing time for the product. The compound must sit for a day and a half then it will be backfilled.
“When the cracks were discovered, the state and federal agencies had to review the project. We were down about a month.
“Who is responsible is still being resolved. It was a design deficiency. The concrete met all strength requirements.
“We will present change orders in commission meeting for the redesign.
“The walls that still need to be poured will be reviewed. The walls were underdesigned. They had about half the amount of reinforcement they needed.
“The design change needs to go clear to Washington for approval. We understand the urgency, but we have to go through the process. In fact, the NRCS guys from Fort Worth, Texas came in and inspected the project. It’s important we find out what happened so it doesn’t happen again.
“The dam is going again, the work is about one month behind. We will need to move the milestone dates for the stakeholders. The reservoir right now is using as much as is coming into the reservoir, but the reservoir will begin to drop again. The reservoir is 17 feet below its normal full point. The canal company will pull the reservoir down low again this year. The allocation this year was 5/8ths share.
“It was a big glitch, but with the redesign we will keep moving forward. The shouldering machine is in place, and we’ve started rebuilding the dam. We’re putting in the materials, filtered sand and gravel,” said Dixon.
Jeremy Guymon with Nielson Construction said crews are working around the clock with two 12-hour shifts. They have 32 Nielson Construction workers and Wall Contractors have their workers who will be busy again when pouring resumes on the spillway walls.
Dixon wanted to stress the fact it wasn’t Nielson Construction or Wall Contractors that caused the hitch, it was a design flaw. “An independent company is doing the review right now. The walls can’t resume until the review is complete. The Dec. 15 completion date will be revised. We looked at several options but the Xypex works back into the concrete and seals the cracks. Water could get into the cracks and cause problems if it wasn’t fixed. The problem was discovered by a rain storm when the tunnel became slushy and wet, water was dripping through the cracks in the tunnel. Concrete always cracks, but it wasn’t supposed to crack enough to cause leakage.
“The outlet works are operational. There are still a few things that need to be done at the state park. The golf course is now using all the holes. There will be a spotter for golf carts during construction work. The bridge across the spillway may be installed in July sometime,” said Dixon.
The spillway wall at its highest spot will be 33 feet tall.
The Xypex will coat the walls and tunnel that were already poured when the design flaw was discovered.
Millsite dam rehabilitation project moving forward again
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