Constructability and stormwater management were two of the challenges our project team faced. Construction oversight was critical to ensure that tight specification requirements were met and proper sand deployment was achieved in order to reduce sand migration due to stormwater erosion. Given the impermeability of the landfill cap, a stormwater conveyance system was developed that redirected stormwater using side-slope diversions and downchutes integral to the cap.
In addition to working closely with the City of Hartford and the Materials Innovation and Recycling Authority, internal collaboration was required between our civil engineering, stormwater management, structural engineering, and electrical engineering teams. As the engineering consultant on this project, we were responsible for landfill closure design and permitting, as well as requesting and receiving approval of the pioneering capping system by the Connecticut Department of Energy and Environmental Protection.
This cutting-edge capping system significantly reduces the landfill’s carbon footprint, utilizing only 18% the carbon footprint of a traditional cover according to Geosynthetics. It also allows greater landfill capacity, results in substantial soil cover savings, and provides long-term durability. The system combines six functional layers of traditional Subtitle D cover into three components: a 50-mil thick structured geomembrane; a tufted geotextile known as engineered synthetic turf; and approximately .5 inches of infill placed into the engineered turf, which can be either sand or cementious infill. This design won the Solid Waste Association of North America (SWANA) Bronze Excellence Award in the Landfill Redevelopment category in 2015, as well as two awards from the American Society of Civil Engineers (Environmental ACE Award and Sustainability ACE Award).
This aesthetically pleasing synthetic cap encapsulates approximately 10 million tons of waste within the Hartford Landfill and adds value to the community by turning an unattractive municipal element into an additional power source. The project exemplifies sustainability by offering the dual benefit of closing and capping the landfill in a sustainable way, while solar cells generate clean, renewable energy.