Asphalt Barrier Prevents Contaminants in the Soil from Reaching Groundwater

For the past several years, the WAPA Paving Innovation Awards have been dominated by the ever-increasing use of porous pavements. For instance, last year, street paving jobs at Gonzaga University for the City of Spokane and in Tacoma on East 40th Street took home the prizes. Porous asphalt is a favorite material for reducing the environmental footprint of paved streets and for returning storm infiltration systems in urban areas to a more natural groundwater recharge profile.

But this year the Special Use and Innovative awards have “flipped” this competition on its head and today, instead of featuring porous pavements that mimic nature, we honor two impermeable pavements, on each side of the state, protecting nature from man-made hazards.

This year’s Special and Innovative use award for Eastern Washington goes to Washington River Protection Solutions at Hanford, Inland Asphalt Company’s Richland operations, Mat-Con, Inc. and Fowler General Construction for the SX Nuclear Waste Tank Farm Impermeable Asphalt (MATCON) Barrier/ Cap paving project

This project involved the installation of an engineered impermeable hot mix asphalt (HMA) cap over the Hanford Nuclear SX Farm. The SX Farm has 15 buried waste tanks holding 22.7 million curies of Strontium-90 and Cesium-137. Eight of the 15 tanks are confirmed or suspected of leaking.

The MatCon, Inc. (MatCon) engineered impermeable asphalt cap is meant to stop migration of the liquid nuclear waste toward the natural groundwater table, reduce the cost of safety monitoring/ maintenance activities at the site and to provide a stable and clean platform for future closure operations. Retrieval and final treatment of the waste is scheduled for 2028.

MatCon has been engineering and overseeing construction of specially designed asphalt liners and asphalt caps all across the county since 1989. This proprietary asphalt technology was invented and pioneered by Dr. Ron Terrel, who was a Professor Emeritus at both the University of Washington and Oregon State University. Jerry Thayer, MatCon’s President, has led MatCon’s sales and operations for most of the company’s history.

Inland Asphalt, Matcon and the entire project team had to undergo extensive safety training to even enter the SX Farm site. Inland’s paving crews worked in protective suits and often required “supplied air” equipment during the operations. Imagine paving in hazmat gear on a sunny day in Richland Washington, where 100oF days are very common! This team really went above and beyond to place 5,200 tons of specialized hot mix asphalt on this nearly 4-acre site, often needing to place the highly modified HMA by hand.

Thank you to this team for doing very important work, using an essentially “souped up” asphalt pavement, to better protect the SX Farm tanks and the soils around them until 2028.