Dam construction underway at LA Reservoir

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By Arin McKenna

After 12 years of delays, it may seem as though government bureaucracy and Mother Nature have been at war with the Los Alamos Dam and Reservoir. But construction is finally underway and if Deputy Utilities Manager Tim Glasco has anything to say about it, the dam will be completed by the end of the year. 


The reservoir has been closed since the Cerro Grande fire impacted it in 2000. The Department of Energy transferred the water system to Los Alamos County shortly after the fire. Since the transfer placed the dam under state jurisdiction, the State Engineer Office was required to conduct a detailed analysis of capacity and stability. That analysis called for a redesign of the dam, which was not approved until 2009.

Reconstruction finally got underway in March 2011 and was approximately 30 percent complete when disaster struck — literally. Los Alamos Canyon was declared a national disaster three times in just over a year: after the Las Conchas fire and again after subsequent floods in August 2011 and again in August 2012.

The 2011 flood obliterated 75 percent of the road and sand and silt filled newly dredged areas of the reservoir. 

A temporary road was constructed this spring and dredging began again, with a goal of having both efforts completed so reconstruction could begin promptly after monsoon season. 

Those efforts were again undermined by this year’s flood. When ASI Construction arrived to begin work in September, they lost more than a month rebuilding the road yet again. 

In spite of that, Glasco is confident that the reconstruction will be completed this year. Crews have finished the foundation for the spillway and laid 3/8 inch pea gravel laced with slotted piping for drainage over that. 

It now becomes a race against the clock to pour 10 feet of roller compacted concrete on the spillway before cold weather sets in, since the material is temperature sensitive. 

The concrete must be built up one foot at a time. The mixture will be sent down a long conveyer belt to the dam, spread to the right thickness by one machine then compacted by equipment with vibrating rollers. That process was to begin early last week, but has been delayed pending the arrival of an auger for the concrete mixer. The auger is scheduled to arrive this Friday, and crews will lay three to four feet a day until the job is finished. 

In the meantime, crews are constructing the cutoff walls on either side of the spillway, and dredging began on Friday. 

The reservoir is completely filled with topsoil loosened by the Las Conchas fire. Department of Public Utilities staff estimate 44,000 cubic feet of soil will be removed to the landfill. 

Glasco said that topsoil erosion should be finished now. There is already a layer of the more usual mix of sand and gravel, and more of that will wash down with the winter run off. When the reservoir is dredged again in the spring, the sand/gravel sediment will be used to lay the foundation of a new roadbed.  The road must be built up three or four feet in some areas to avoid future flooding problems.

When the dam is complete, it will provide non-potable water to irrigate parks, schools, ball parks the golf course and cemetery. Previously, reservoir water was used for irrigation only at the high school and football field, but the county has spent several years building backbone infrastructure pipeline to channel water from the dam to key facilities. The non-potable water will provide irrigation at a fraction of the cost for potable water. 

“But the main use of the reservoir is for the public, for recreation use,” Glasco said. “This is a very nostalgic place. The citizens of Los Alamos really want this reservoir done. It’s a great place to come, teach your kid to fish.”

Still, it will be several years before the reservoir provides fishing opportunities. Based on experience from the Cerro Grande fire, Glasco estimates that spring runoff will fill the reservoir with large quantities of sediment for at least five years, meaning it will have to be drained and dredged every year until 2016. Glasco does not know how long after that it will take for the ecosystem to recover enough to sustain a fish population. 

But there could be other recreation opportunities opening up. An agreement reached with the National Forest Service as part of the land transfer to San Ildefonso and Santa Clara Pueblos makes six parcels of land available to Los Alamos County for purchase. One of those parcels is the land surrounding the reservoir. 

NFS is in the process of writing up deeds and determining easements. It will then get an appraisal on the land, at which point council will decide whether to appropriate money for the purchase. 

Whether the county purchases the land or not, Glasco expects the reservoir to open for recreation as soon as construction of the new access road is complete, probably sometime next summer. He is as eager as other residents to see that happen. 

“My kids grew up and didn’t get to come up here because it was closed in 2000,” Glasco said. “But my grandkids can come up here and and I can teach them to fish here.”  

More photos of the construction project can be found in the Multimedia section of LAMonitor.com.