Landfill Management Technical Division

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Looking for info on use of permeable caps or alternative capping schedules at landfills

By John Welch posted 09-10-2014 05:33 PM

  

In Wisconsin, current code requires landfill operators to install final cap within two years after an area of the landfill has reached final waste grades.  We have seen this lead to decreased gas production and presumably extended organic stability timeframes at several landfills statewide.  Also, we have seen sites with substantial settlement within the first 5-7 years that are unable to refill the settlement airspace because it was capped within 2 years.  As a result, we are doing some research into the state of the industry regarding permeable caps and/or delayed capping schedules. 

What are the capping requirements in other parts of North America?
Have you seen permeable caps allowed in other States/areas?
Do other States/areas allow alternative or delayed capping schedules?

Thank you for any information you can share!

Respectfully,
John Welch, P.E.
Solid Waste Manager
Dane County Public Works, Solid Waste Division
welch@countyofdane.com
office: 608-267-8815
cell: 608-516-4154

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02-11-2015 11:14 AM

Landfill Operating Approvals in the Province of Alberta typically establish the Top of Waste as the final elevation. What some landfill managers will do is complete the fill to a few meters below this elevation to avoid triggering placement of the final cap. Doing so allows for initial settlement and consolidation to occur prior to reaching the final elevations. This gains additional airspace, and reduces the impact of settlement on the final cap. In these cases, the landfill manager will apply an interim cover over the incomplete area. This interim cover can be removed or breached at the time when fill operations continue over the area.
This does not mean that a landfill operator doesn't apply any final cover. In fact, outside slopes are often completed to design grade, capped, and vegetated. You can think of the landfill closure being progressive over the life of the landfill from the ground up, rather than being top down.