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Landfill Cap – Eugene, OR




PROBLEM: A Landfill cell had reached its full capacity. The landfill owner was required to close the landfill to prevent future rain falls from getting into the hill of garbage creating additional leachate, containing the waste and managing gas emissions.

SOLUTION: Install a geomembrane cap over the garbage and cover it with soil, place grass seed on the soil and create stable, long term containment closure of the waste.

CONSTRUCTION DETAILS: The first step was to shape the landfill and cover it with a layer of select semi impermeable soils. Step two was to install vents to allow the methane gas to be managed and removed from under the new cap. Once the venting system and soil layer were placed, they were rolled and prepared for the placement of a 60 mil LLDPE integrated drain structure geomembrane. The pan- els of 60 mil LLDPE gemembrane are deployed from rolls 23’ x 280’ onto the ap- proved grade, then fusion and extrusion welded together to create a complete barrier above the waste. The 60 mil LLDPE geomembrane has an integrated drain structure on the top side that is part of the 60 mil geomembrane that only requires a nonwoven geotextile layer to be placed over it to create a fully functioning drainage collection and transmis- sion layer for rainwater. This takes the place of drainage soils or additional geocomposite layers that are not stable and require more work on top of the barrier geomembrane. A dirt cover was placed on top of the 60 mil LLDPE and 8 oz nonwoven geotextile. The entire surface was then seeded to prevent erosion over time. The 60 mil LLDPE SuperGrip Net (integrated drain structure) and 8 oz nonwoven geotextile were selected because they offered a high friction angle as well as superior drainage of rainwater.

PROJECT: Short Mountain Landfill

LOCATION: Eugene, Oregon

ENGINEER: Vector Engineering, Richard Thiel

CONTRACTOR: Tri-State Construction

LINER INSTALLER: Northwest Linings & Geotextile Products, Inc.

MATERIAL: 60 mil LLDPE S6N (integrated drain liner) with an 8 oz nonwoven geotextile over the integrat- ed drain structure of 60 mil LLDPE

AREA: 830,000 SF