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

There will be a release of stored water behind the coffer dam at Rio Grande Reservoir beginning in the morning on Thursday, November 22 and lasting until the morning of Monday, November 26. It can be expected that there will be flows in the range from 0 - 150cfs from the reservoir during this time frame with the higher amounts of water at the beginning of the release on Thursday and tailing off by Monday morning. This procedure is necessary for the safety of the project working staff and their efforts towards the rehabilitation of the outlet tunnel through the dam at Rio Grande Reservoir during the winter months. 
UPDATE:
 
Update for December,  2018:
 
Reservoir:  The Reservoir continued to store all available inflows during the month.  Approximately 1,067.0 acre feet was stored behind the cofferdam November 1 through November 21 while crews worked in the tunnel.  There was a release of 1,023.5 acre feet over a four day period in November.
 
Project:  Work at the reservoir during the month of December included demolition of the existing intake structure,  completion of a new concrete intake structure, mud mat and intake flooring.  The rock at the intake structure was found to be in worse condition than originally thought and the situation was addressed accordingly by Deere and Ault Consultants.
 
The downstream high wall in the river bottom was excavated in preparation for the pipeline and new valve house that will be completed next year.
 
Sub-Contractor Harrison Western performed necessary blasting and installed rock bolts in the downstream,  upstream and brow of the tunnel.  Harrison Western also completed the mucking out of the downstream invert to allow for construction of a leveling mat for the installation of the 126" diameter pipe.

November and December,  2018:
 
Reservoir:
The Reservoir continued to store all available inflows during the month.  Approximately 1,067.0 acre feet was stored behind the cofferdam November 1 through November 21 while crews worked in the tunnel.  There was a release of 1,023.5 acre feet over a four day period in November.
 
Moltz Civil back filled the steel liner / pipe in the downstream tunnel with 495 yards of SCC concrete within 1.5 feet of the crown of the tunnel.  They also began excavating the valve house foundation and high wall excavation for shotcrete and bolting processes.
 
Project:
Work at the Reservoir during the month of November included demolition of the existing intake structure, completion of a new concrete intake structure, a mud mat and intake flooring.  The rock at the intake structure was found to be in worse condition than originally thought and the situation was addressed accordingly by Deere and Ault Consultants.
 
The downstream high wall in the river bottom was excavated in preparation for the pipeline and new valve house that will be completed next year.
 
Sub-Contractor Harrison Western performed necessary blasting and installed rock bolts in the downstream, upstream and brow of the tunnel.  Harrison Western also completed the mucking out of the downstream invert to allow for construction of a leveling mat for the installation of the 126" diameter pipe.
 
January,  2019:
 
Reservoir:
A second release / drawdown took place December 22 through December 26,  leaving 43.5 acre feet stored in the Reservoir behind the coffer dam.
 
Project:
A Concrete mat and narrow gage rail were placed in the invert from the portal extending to the slide gates to transport the 126" pipe into the tunnel.  Three pieces of the steel pipe was installed and Mountain Man Welding welded the pipe and end pieces.  An inspector was onsite,  checking each weld as completed.
 
Moltz Civil completed the concrete placement of the three intake structure walls and intake floor.
 
Harrison and Western installed Class I and Class II rock bolts,  brow anchors and rock anchors,  conducted prop work for shotcrete in the upstream tunnel,  and excavated the upstream invert up to the lower rib walls for the pier wall at the intake structure.
 
February,  2019:
 
Reservoir:
A third draw down took place between January 25 and January 29,  releasing approximately 1,417.5 acre feet to allow the crew to safely work in the tunnel.
 
Project:
Moltz Civil completed the placement of the concrete intake structure walls and a 4.0 ft. deck on top.  They also finished the concrete invert placement of the upstream tunnel.  All concrete supplied for these projects was produced at the local ACA Products cement batch plant.
 
Harrison Western installed all 47 contract Class I spot bolts and completed Class III shotcrete in the upstream tunnel.
 

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

The cofferdam gates were shut off this morning and Moltz Civil has began access to the tunnel.  There doesn't appear to be any damage caused by the high flows this past summer. 
 
We started 25.0 cfs of recharge water in the Farmers Union Canal today and we will try to maintain at least that much flow for as long as the weather permits this Fall.
 
This is a photo of manhole no. 5 being placed for the additional pipeline that will make drainage for the large pipe and  toe drains of the dam.

November 05,  2019

We are enjoying the mild weather and currently have 4 crews working onsite. 
This is a photo of shotcrete being placed along both outside walls of the intake structure by Harrison Western.  They will also drill and chemically grout the south rock wall along the intake structure.

November 05,  2019

Moltz Civil has completed their last placement of concrete for the walls and valve support pillars in the lower floor of the valve house.  Outstanding!

November 05,  2019

 The south gate was opened in the dam for the last time this morning.  It will be a historical moment today,  as one of the dam gates will be filled with cement.