Reusing excavated dirt saves more than $11 million and nearly a half-million pounds of carbon emissions

Los Alamos National Lab’s use of engineered fill is a win-win

December 11, 2023

The Sigma Mesa Clean Fill Stockpile collaborators: (left to right) Leonard F. Sandoval, James Gallegos, Gary McMillan, Martin Owens, Paul Luik, Thaddeus Kostrubala, Santiago (Santi) Scheer Salazar, Sergio Marquez and Daniel Maes (general foreman and Teamster) on front loader.

Los Alamos National Laboratory has saved $11.7 million by processing and reusing soil already excavated on-site for new building foundations, roads, and utility and stormwater lines.

“Cost savings to the Laboratory is only one of the benefits,” said Jen Payne, chief operating officer for the Associate Lab Directorate for the Environment, Health, Safety and Quality. “The reduction of greenhouse gas emissions is also important and helps us to meet our sustainability goals while also decreasing the number of trucks on our already heavily trafficked roads.”

This program stands to save the Lab significant money for years to come while avoiding 1,850 round trips for trucks on the roads, saving 19,300 gallons of diesel and eliminating 428,000 pounds of carbon dioxide emissions.  

Big plans, big projects

Los Alamos National Laboratory is planning more than a million square feet of construction in the next five years in the Pajarito Corridor, and that means the Lab needs thousands of cubic yards of usable dirt, free of debris, called engineered fill, for foundations, roads and infrastructure. 

The soil at the Lab and in surrounding Los Alamos County generally comprises poor-quality volcanic tuff so, without a local source, soil had to be hauled up to the Lab. This created additional costs, emissions and vehicular traffic.

But the collaborative initiative recently launched by the Lab is cutting costs significantly. It costs about $13/cubic yard to process engineered fill onsite, whereas purchasing engineered fill from a vendor costs around $247/cubic yard, saving the Lab $11.7 million for the 50,000 cubic yards recently processed.

Expansion inspires innovative solutions

For more than 10 years, the Lab has been hauling dirt from construction project excavations to the Sigma Mesa Clean Fill Stockpile in Technical Area (TA)-60 hoping to find a use for it. The material met environmental requirements and was verified clear of trash, wood, concrete, other construction debris and hazardous materials.

But this 50,000 cubic yards of dirt still wasn’t the engineered fill that construction projects require, so it wasn’t being used.

In late 2022, the TA-51 warehouse complex project in the Pajarito Corridor began site preparations for four new 20,000-square-foot structures that would require approximately 130,000 cubic yards of engineered fill material. The TA-51 warehouse project team began the process of screening, testing and blending the Sigma Mesa Clean Fill Stockpile material with on-site soils to create the desired engineered fill. In recognition of this waste reduction and innovative repurposing of materials from the stockpile, the team won a Patricia E. Gallagher Environmental Award.

Capitalizing on the success of the warehouse project, Paul Luik, strategic improvement management lead for the Associate Laboratory Directorate for Infrastructure and Capital Projects, contacted the environmental and logistics teams to see how this resource could be further used. Engineering joined the collaboration to develop a plan for testing and ensuring the soil meets engineered fill standards, and Infrastructure and Capital Projects came through with funding.

Sigma Mesa Clean Fill Stockpile being processed to become engineered fill in 2023.

Clean fill dirt transforms to engineered fill

During the last two months of the 2023 fiscal year, the Logistics Heavy Equipment Roads and Grounds group processed more than 50,000 cubic yards of fill dirt. The crew ran the excavators and loaders for 10 hours a day and some weekends, screening to remove materials one inch and larger such as roots, cement and asphalt. After every 2,000-3,000 cubic yards of soil was processed, the Engineering Services Materials Testing Laboratory team performed a proctor test — which measures compaction and moisture levels.

With the processing and testing formalized and the initial projects completed efficiently and safely, the Lab is now creating its own engineered fill while dirt continues to be excavated from projects.

Loading engineered fill will go out to sites after processing.
Santiago Salazar, Ryan Keyser, Carl Griego and Benjamin McHugh collaborated with internal construction at Weapons Facility Operations on the recent Vault Type Room Magazine project to use engineered fill from the Sigma Mesa Clean Fill Stockpile, saving $50,000 in material.

What happens with old concrete and asphalt after demolition projects?

Besides reusing dirt at the Lab, recycled concrete and asphalt materials from demolition projects will soon be available for construction projects, roads and parking lots.

In 2021, the Lab sent 850 tons of asphalt and 990 tons of concrete to Los Alamos County Eco Station for disposal. But in 2022, the county ran out of storage space on-site. Until July 2023, the Lab’s asphalt and concrete were being sent to GM Emulsion, a vendor in Española.

As of this summer, GM Emulsion has an operational permit to process waste concrete at the Los Alamos Eco Station, so the Lab no longer needs to transport these materials to Española, reducing trucking costs. 

“This mixture of concrete and asphalt is called conphalt and is known industry-wide as recycled base course,” said Michael Moss of Environmental Protection and Compliance. “As the Lab continues to grow, there will be many uses for this material in the coming years.”

Los Alamos County Eco Station is now able to process waste concrete.