Los Alamos County Landfill Closure

Background

APTIM served as the primary engineering contractor, planning and designing the reuse, recycling, and vegetative management in a comprehensive landfill re-use project in New Mexico. This project is an example of innovation and how to successfully transform a closing landfill into a sustainability asset for the community through expanding recycling opportunities, constructing a LEED-certified Eco Station (transfer station), and developing a state of the art solar photovoltaic installation. Through promotion of reuse, recycling, and renewable energy, this project greatly benefits current and future generations. In addition, the research associated with the solar photovoltaic system and smart grid portion of the project, helps advance the deployment and development of renewable energy around the world.

Our Approach

An ~8.5 acre outdoor recycling area was developed. The final cover system includes 12-inches of intermediate soil cover, a geocomposite clay (GCL) liner, 18-inches of protective soil cover, and 6-inches of gravel. A wearing surface of varying thickness consisting of asphalt millings was placed on top of the cover to provide additional protection. On an additional plateau, the west half of the landfill, the recycling area has grades of 2% to 5% to promote drainage.

Outdoor Recycling Area

The outdoor recycling area is used to process recyclables including concrete, tires, metal, manure, compost, and brush, as well as provide storage for containers. This intensive use area involves heavy equipment to load and process large quantities of recyclable material. For this type of activity, the principal concern is maintaining the integrity of the underlying landfill cap against abrasion. The cover system in the outdoor recycling area also features a GCL for infiltration reduction, and a gravel top layer.

Sideslope Areas

The balance of the landfill, ~12 acres, is capped with an Evapotranspiration (ET) cover system. The profile of the ET cover, from bottom to top, includes 12 inches of intermediate soil cover, an 18-inch infiltration reduction soil layer, and a 6-inch erosion protection layer. The ET cover system is planted with native species for vegetative cover. Grades in these areas are generally 4H:1V, although one section along Sandia Canyon has steeper slopes of 3H:1V.

The ET cover system reduces infiltration of precipitation into the landfill through storage of moisture in the soil cap and through natural processes of evaporation and plant transpiration. The advantage of the ET cap is that construction is relatively straightforward and inexpensive. The ET cover system is constructed using standard earthwork techniques to place and grade soil materials, notably under light compaction to foster plant growth. This type of cover system is suitable for passive end use and the vegetative cover provides a landscape representative of the native vegetation of northern New Mexico.

Solar Project Area

The solar power area is ~14.7 acres and is located on a plateau area on the east half of the landfill. This area features grades of 2% to 5% to promote drainage. 1 MW of solar photovoltaic arrays were installed on the closed landfill and 8.3 megawatt hours of batteries immediately adjacent to the closed landfill as part of the Los Alamos County Smart Grid Project.

Eco Station

A Leadership in Energy and Environmental Design (LEED) certified transfer station was constructed adjacent to the closed landfill to efficiently manage and transport waste and recyclables to distant processing facilities and end markets.

Outcomes

The undervalued land of a closed landfill was used to create a solid waste management park and renewable energy generation site. The county now provides integrated solid waste services, despite its remote location, and serves as a model of excellence for other small counties and for larger jurisdictions looking to adaptively reuse closed landfills. This project was awarded the Solid Waste Association of North America Landfill Re-use Excellence Award, whose highlights include successfully transforming a closing landfill into a sustainability asset for the community through the expansion of recycling opportunities, the construction of LEED-certified Eco Station (transfer station), and the development of a state of the art solar photovoltaic installation.

Aesthetically, the closed landfill incorporates a vegetated ET cover system on the slopes of the landfill. The plantings include native vegetation to provide a landscape representative of northern New Mexico and a pleasing view to observers located across Sandia Canyon. The solar panels are located on a plateau area on the east half of the landfill, and are low mounted to the ground, providing visual interest without being obtrusive.