New Industrial Landfill

This project consisted of the construction of an industrial landfill. This first phase required extensive site preparation, which comprised the clearing and grubbing of 50 acres at the landfill site, the stockpiling of the trees and the excavation of 150,000 cubic metres of peat moss. Graham’s groundwater dewatering system was used to lower the water table to allow for the excavation of the peat moss. Site preparation also included the clearing, grubbing, tree stockpiling and excavating of topsoil for a 1.8 kilometre access road.

The next phase was made up a 120,000 square meter landfill base and perimeter sand berms. The sand construction phase of the landfill included the development and reclamation of two sand borrow pits, the levelling of 45,000 cubic metres of suitable sand for the construction of the base and perimeter berms. The common fill sand was placed in maximum 150 mm lifts and was compacted to a minimum of 95% of the standard proctor at the optimum moisture content. This phase of the landfill project also included the topsoiling and seeding of the outer perimeter berm slopes.

The final phase included the placement of 140,000 square metres of 1.5 mm flexible membrane HDPE liner above the landfill clay base and inside the perimeter berm sideslopes. Above the impermeable HDPE liner, on the inside perimeter berm sideslopes, is a layer of HDPE geonet drainage material followed by a layer of non-woven geotextile. Following the construction of the leachate collection system, cushion sand and drainage gravel layers, a layer of non-woven geotextile was placed over the entire landfill base.

Also included was a leachate management system to collect and remove wastewater from the landfill. The system included a network of sloping HDPE collection pipes on the landfill floor that drained into two manholes. The wastewater was pumped from the two manholes, through our newly constructed pumphouse and into a leachate forcemain. The 1.8 kilometres of leachate forcemain was buried a minimum 3 metres below grade and included one air release manhole. The leachate system tied into the existing waste water handling system. Surrounding the HDPE collection pipes on the landfill floor was a layer of protective cushion sand and drainage gravel that acted as a filter system to the collection pipes, and a protective layer above the HDPE liner.