Considerations for underground electrical on closed landfill

[nhee2]

We are developing design for installation of underground electrical conduits for outdoor application on a closed, uncapped landfill. There are no classification drawings or similar to suggest that the below-grade installation has previously classified, and I am currently not considering the below grade area classified. My intent is to specify PVC conduits, with risers to outdoor electrical equipment terminating in an intermediate vented box, with a separate conduit leaving the vented box and run above ground to the equipment (panel board, switch, misc controls). I plan for the conduits to be sealed with duct seal to prevent (or minimize) any migration of landfill gas into the electrical equipment, and am thinking that any gas which makes it past the primary seal (on underground riser) will be vented rather than migrating past the secondary seal (in aboveground conduit) into the equipment.

Have others performed similar installs on closed landfills and if so were there any other design considerations that were implemented (successfully or unsuccessfully)?

 

[Fulthrotl]

We are developing design for installation of underground electrical conduits for outdoor application on a closed, uncapped landfill. There are no classification drawings or similar to suggest that the below-grade installation has previously classified, and I am currently not considering the below grade area classified. My intent is to specify PVC conduits, with risers to outdoor electrical equipment terminating in an intermediate vented box, with a separate conduit leaving the vented box and run above ground to the equipment (panel board, switch, misc controls). I plan for the conduits to be sealed with duct seal to prevent (or minimize) any migration of landfill gas into the electrical equipment, and am thinking that any gas which makes it past the primary seal (on underground riser) will be vented rather than migrating past the secondary seal (in aboveground conduit) into the equipment.

Have others performed similar installs on closed landfills and if so were there any other design considerations that were implemented (successfully or unsuccessfully)?

if you are 24" deep, pvc is acceptable in classified locations.
stub up in GRC, put a seal off on it, pour it, and move on.

a poured eys works well against methane.

waste methane is pretty corrosive, iirc. i'd be more concerned
with corrosion and ick than explosions.

 

[peter d]

I've read that landfills settle about 6" a year once they become inactive. How is this amount of settling dealt with?

 

[Fulthrotl]

I've read that landfills settle about 6" a year once they become inactive. How is this amount of settling dealt with?

never even thought of that.... leaves you with GRC for the whole thing, with scotch wrap for corrosion protection...... or rob roy.

ow. that's gonna leave a mark.

 

[nhee2]

if you are 24" deep, pvc is acceptable in classified locations.
.

Actually I believe this is only true for article 514 applications - 501.10(1)(a) requires concrete encasement for buried PVC. Regardless, in this case the existing area is not classified.

 

[shortcircuit2]

Landfills I've seen are done above grade with cable tray.

 

[JFletcher]

if you are 24" deep, pvc is acceptable in classified locations.
stub up in GRC, put a seal off on it, pour it, and move on.

a poured eys works well against methane.

waste methane is pretty corrosive, iirc. i'd be more concerned
with corrosion and ick than explosions.

Methane isnt corrosive, but Hydrogen Sulfide and Sulfur Dioxide are. Both are heavier than air and will collect in low lying areas.