The Comstock Lode Silver Rush, which was part of the California Gold Rush, took place in the late 1850s and ran until around 1880. Virginia City, Nevada — just 1 mile east of Lake Tahoe — boomed due to the rush. In 1873, the nearby Marlette Lake Dam in the Sierra Nevada mountains was constructed.
The dam continues to function today and provides drinking water for Storey County and nearby Carson City, Nevada. Granite Construction is leading a rehabilitation project to stabilize the dam and ensure it continues to serve the communities that count on it.
The dam contains some of the original 1873 materials. However, the upgrade is focusing on pipes and a section of the dam installed in 1956.
While the dam was functioning as needed, it was at risk of catastrophic failure due to seepage issues and structural integrity issues.
"They were starting to see water infiltrating the dam and coming out outside of the outlet pipes, so they did some exploratory investigation," said Granite's Ryan Murray, who is serving as the Project Manager. "They found that the pipes were getting eroded, and seepage was occurring."
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Besides the natural decline due to its age, a FEMA fact sheet notes that the dam is in an area of high seismic hazard. According to FEMA, “annual inspections of the dam indicate a high probability of a dam breach due to an earthquake of 6.5 magnitude or larger, and seepage at the downstream toe of the dam along the primary outlets also increases the risk of dam failure."
FEMA classifies the Marlette Lake Dam as a “High Hazard Dam,” which makes securing and repairing the dam even more critical.
The construction team is installing a new outlet structure, new outlet pipes, a dissipation structure, and then rebuilding the dam.
"You could look at it as just a very deep underground job with only 267 feet of pipe," Murray said, "but we have roughly 17,000 cubic yards of existing embankment that was on the dam, and we have to move that earth upstream and into the lakebed."
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The team is installing a dam system built by AquaDam that includes three different cofferdams/water-filled barriers that hold back the lake and give the team room to stockpile the 17,000 cubic yards of dirt. Once the excavated material stockpile is in place, the team will remove the existing dam controls.
The final element of the project is an intricate seepage collection system.
"It's comprised of an 8-inch HDPE [high-density polyethylene] slotted drainpipe with a filter material and a drain material to intercept natural seepage through the dam,” Murray said. “Seepage that goes through the dam will then get collected in the seepage collection pipe and spit out at the headwall."
Finally, the team is importing in approximately 9,000 tons of buttress fill material to bolster the backside of the dam and hold back the lake.
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The team is facing two main challenges on the Marlette Lake Dam rehabilitation project — location/access and time.
The dam is located within Spooner Lake State Park. The only way to access the dam is via a 6-mile backcountry access road from State Route 28 up to the lake and dam location. Trees surround the 12-foot-wide access road.
Tahoe Regional Planning Agency guidelines restrict access and construction on the dam from May 1 to October 15, and that is weather-dependent. The team knew they had to be ready to go as soon as May 1 rolled around. They were on the access road by mid-April, clearing some snow drifts on the road.
"It took us almost a month and a half to improve that access to get our water-filled cofferdams up to the site," Murray said.
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The team was able to mobilize the cofferdams at the end of May. The cofferdams are massive — the largest AquaDam has ever built. The largest of the cofferdams were 60 feet long and 80,000 pounds in a rolled configuration for shipping. Once set, it is 75 feet wide, 220 linear feet long, and 34 feet tall, and full of water.
The team considered using a helicopter to transport the cofferdam or sliding it along the snow, but they determined it was too big and heavy. Ultimately, the cofferdams were transported on the back of a large Peterbilt transport and towed up that dirt road.
As the transport occurred, there were points along the dirt road that the truck could not pass due to its width. So, the transport truck was stopped, and the team made the necessary improvements to the access road.
The area where the work is taking place is also constrained.
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"There are rock walls on either side of the project, which is why we had to hold back the lake where we did to have room to stockpile materials," Murray said. "It's very challenging to have multiple operations going at once, because the work area is incredibly constrained."
The tightness of the work area has caused some issues.
"What we're dealing with, if one truck goes in there and a piece of equipment comes down, until that equipment moves, it's staying there,” Murray added. “We have a truck that has been staged on the opposite side of the trench where the new outlet pipe goes, and it's been there for six weeks [physically locked in], and it won't come out until we can backfill that pipe."
The 14-ton Prinoth Panther rotating crawler dump trucks have proven especially useful due to their ability to navigate the area. The cab and bed part of the truck rotate, eliminating the need for a complete turnaround when dumping material or returning to the site.
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"Because [of] the rotating cab and bed, the dump trucks don't have to do a three-point turn. We didn't have to build turnarounds," Murray said. "So, the dump trucks accelerated our schedule by being able to do more trips."
To stay on schedule, the team needed to complete the rehabilitation project in one construction season during 2025. Murray emphasized the importance of making every day count and credited the team for keeping the project on track.
FEMA, along with the Nevada State Public Works Division, Nevada Division of Forestry, and Nevada Department of Wildlife, worked together to get ahead of issues and to create quick turnarounds and solutions when problems occurred.
While construction is taking place over one season, Granite has been part of the project for years. The project is being delivered via the construction manager at risk (CMAR) method, so Granite was brought on to the project in 2019 during preconstruction.
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Because the team was involved early on, they saw the design concepts, provided feedback, and considered constructability. They also saw how the plans changed.
"The scope of the project evolved from its original concept of being a soil improvement project, where essentially you drill into the dam and reinforce to taking the entire dam out, replace those pipes at the bottom, and re-embank the dam," Granite Preconstruction Coordinator Ryan Floyd said.
The construction budget for the project is $20 million, with FEMA chipping in $10 million. The State of Nevada is funding the remainder.
Floyd, Murray, and the Granite team were confident that they would come up with a guaranteed maximum price that would gain them the project. They have delivered many projects via CMAR and have found that during preconstruction, the team builds relationships and trust with the owner. They also demonstrate that they have the ideas and ability to get the job done successfully.
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The Gold Rush and Silver Rush are long over, yet the need for water in Storey County remains. The rehabilitation of Marlette Lake Dam ensures it will continue to provide this vital resource to the area for years to come.
- Owner: Nevada State Public Works Division
- General Contractor: Granite Construction, Watsonville, California
- Designer/Engineer: Lumos and Associates, Reno, Nevada
