PHASE II:
Phase II of the project will begin on November 1, 2018. This leg of the project will involve a new intake and guard gate structure,repair work to the outlet tunnel, and a new valve house.
PROJECT FUNDING:
On April 3rd, 2018 the District held a special election to allow electors to decide whether or not to enter into contract for a $15 million dollar loan, in addition to a $10 million dollar grant to be received by the Colorado Water Conservation Board to complete the Rio Grande Reservoir Rehabilitation Project. District landowners voted in favor of the funding package.
CONSTRUCTION CONTRACTOR:
Moltz Civil, LLC was awarded as the preferred contractor for the completion of Phase II of the Rio Grande Reservoir Rehabilitation Project.
PHASE II:
Phase II of the project will begin on November 1, 2018. This leg of the project will involve a new intake and guard gate structure,repair work to the outlet tunnel, and a new valve house.
PROJECT FUNDING:
On April 3rd, 2018 the District held a special election to allow electors to decide whether or not to enter into contract for a $15 million dollar loan, in addition to a $10 million dollar grant to be received by the Colorado Water Conservation Board to complete the Rio Grande Reservoir Rehabilitation Project. District landowners voted in favor of the funding package.
CONSTRUCTION CONTRACTOR:
Moltz Civil, LLC was awarded as the preferred contractor for the completion of Phase II of the Rio Grande Reservoir Rehabilitation Project.
RIO GRANDE RESERVOIR REHABILITATION UPDATE:
Rio Grande Reservoir Rehabilitation Update
October 2, 2018
The San Luis Valley Irrigation District’s (SLVID) rehabilitation of Rio Grande Reservoir is underway. Moltz Construction of Salida Colorado was selected as the contractor. The rehabilitation involves replacing the 100-year old outlet works, which requires draining the Reservoir and controlling inflows while a 10 ½ foot diameter pipe is installed in the outlet tunnel and the existing outlet gates are replaced. The project is especially challenging because the Rio Grande constantly flows into the Reservoir and these flows must be bypassed while the outlet works are undergoing repairs.
What has happened so far:
SLVID drained the Reservoir throughout the summer with the last major release occurring during September. Up to 100 cfs per day was released from August 13th through September 23rd and diverted at the Farmers Union Canal near Del Norte. This release provided increased late summer streamflows during an especially dry year. The release lowered the water level in the Reservoir to just below the top of the coffer dam which was constructed during prior repairs of the Reservoir in the 1980s and was used during repairs in the 1990s to control the flow of water through the outlet gates.
The coffer dam is a small dam and headgate constructed in the Reservoir immediately behind Rio Grande Dam which provides temporary stoarge of water behind the coffer dam while work is performed on the outlet tunnel and gates. When the coffer dam is nearly full, workers and construction equipment will be putlled out the Reservoir bottom and outlet and the water behind the coffer dam is released to the Rio Grande. The workers and construction equipment then go back to work until the coffer dam is nearly full. the amount of time that water can be stored behind the coffer dam varies based on inflows into the Reservoir, which is the reason this type of work occurs during October through March, when flows in the Rio Grande are low.
Near the end of September, SLVID started to lower the remaining water behind the coffer dam to inspect it and test whether it was operational. When the water level is dropped for repairs, water is stored behind the dam.
Existing Site Conditions:
The coffer dam has been underwater since the last Reservoir repairs were performed in the early 1990's. As the water level was lowered it became apparent that the headgate structure controlling the release of water behind the coffer dam had been damaged. As shown in the picture above it was leaning and, once the coffer dam was completely drained, SLVID discovered that the pipes has separated from the headgate structure. This separation occurred sometime between the last outlet repairs in 1990s and 2018 but was not visible because the coffer dam was underwater until now.
Left: Closeup of separated pipes at the coffer dam
Tilted headgate structure at coffer dam
As the water behind the coffer dam drained, the bed of the Reservoir was exposed and the Rio Grande inflows started to cut into the 100 years of silt that has accumulated at the bottom of the Reservoir. Therefore, the water released from the Reservoir was muddy. To repair the coffer dam, SLVID is going to build a second temporary dam which will store water away from the coffer dam headgate structure. SLVID has requested an exchange of inflow/release from the Santa Maria Reservoir while water is stored during the structure repair period which will provide clear water to the river below the confluence of Rio Grande and Clear Creek. Repairs of the headgate structure will take approximately three weeks. These unexpected repairs and the construction of the temporary dam are estimated to cost $150,000.
FUTURE OPERATION DURING CONSTRUCTION
Once the coffer dam headgate structure is repaired, water will be stored behind the coffer dam for approximately two to three weeks at a time, depending on inflow, and the evacuation and release process described above will be initiated. Whenever possible, the contractor plans to make these releases over a weekend or holidays. Because water flowing into the Reservoir will continue to cut through silt in the Reservoir bottom, when it is released behind the coffer dam, particularly when the last of the water behind the coffer dam is released, it will contain some of this silt and will be muddy. There are five planned releases from the coffer dam between now and February 15, when the installation of the new outlet guard gates should be complete. Once the guard gates are installed, releases from the coffer dam will no longer be required.
For additional information on the construction project contact Rob Phillips, SLVID Superintendent at 719-754-2254. SLVID will be posting updates to its website at www.slvid.org/project.
UPDATE: November 14, 2018
RIO GRANDE RESERVOIR RELEASE
Final Phase
FROM THE SUPERINTENDENT:
AUGUST 21, 2019
The Moltz Civil crew are near completion of the select rock fill for the lower foundation of the new valve house downstream from the dam. They are scheduled to have the new valve house near completion by the end of September. The large valves will have to be placed upon arrival, which is sometime in October. All of their efforts right now are focused on this area of the project.
August 21, 2019
We shut down the reservoir the last two days so Moltz Civil could have a dry stream channel to begin with and turned back on today, passing approximately 130.0 cfs of inflow. We are going to start moving more stored water with the inflow tomorrow at a slower rate while they are working in the channel. We hope to have the reservoir drained to a small pool again by the first week in October. Everyone was excited to begin again and all are looking forward to another productive construction season.
November 01, 2019
November 05, 2019
November 05, 2019
November 05, 2019