Landfill groundwater quality 1

[morgcolt]

I need to discuss groundwater seepage velocities for a landfill site, yet have not actually performed any form of calculation. Apparently, I am looking for info regarding generic groundwater seepage velocity discussions......

 

[KRSServices]

Groundwater seepage?

Are you referring to leachate migration over time within the landfill? Or the percolation rate of the leachate through the liner? Or is leachate migrating into a groundwater source? Or are you needing information for a new site?

KRS Services

http://www.krs-services.com

 

[morgcolt]

I am referring to leachate migration over time within the landfill (average linear velocity)? I am in the process of closing an old Landfill that was unlined, yet have to respond to the state about information that was compiled by another engineering firm, so the info. is scarce. A river is located 200 feet away and the soils in the landfill are silty sands. So far groundwater is pretty clean except for a bit of manganese and nitrate, so I am hoping and attempting to have the state be less stringent about closure. Anyhow, I am trying to calculate how long it takes for the groundwater from the landfill to reach the river. I used a typical permeability for soil types of this sort (10 -4)and an assumed porosity of .25. The average gradient is .004 feet per foot, so I guess I can calculate this way unless another better way is out there that I am not aware of at this time. Thank you so much for your time.

Jennifer Stonecipher
Environmental Manager

 

[KRSServices]

Ouch!

Realizing of course that depending on the size, post closure is going to be between 50 to 75 years, and I would assume that the landfill has been in operation for about 25 years? Yes? No?

The concern is not going to be migration into the river per se, unless the lanfill is located on a large hill upgradient from the landfill, but the location of the groundwater relative to the floor of the landfill. It will be a determination of how long until the leachate comes into contact with the groundwater and the "flow" characteristics of the groundwater. With a river in the proximity, I would conclude that there would be significant stratified layering of a soils characteristic with fluvial depositing within the zone of influence of the lanfill. If this is the case, there may be groundwater migration over time, if it has not occured yet, of the leachate plume to the river or other users (say domestic water wells).

The task will be to dermine whether this condition exists and what is the flow in the groundwater. The State may then determine or order what they deem as appropriate post closure.

Up here liners, including clay liners, require a permeability of less than 1 x 10-8 m/s immediately
beneath all waste disposed at or below the original grade, and is less than 1 x 10-8 m/s to a depth of at least 5 metres beneath the clayey deposit.

Be prepared to have to look into a leachate collection system and extensive monitoring. Hope this helps.

KRS Services

http://www.krs-services.com

 

[rogerstv]

You may want to try the Illinois EPA as a resource. Their Tiered Approach to Cleanup Objectives (TACO)guidelines are geared mainly towards contaminant movement in groundwater.

The idea is for a landowner to show that the contamination will not migrate off his/her property. This allows for less stringent cleanup standards and usually no cleanup at all.