McCommas Bluff Sanitary Landfill, Dallas

Date ant Time:  July 30, 2011  12:00Noon

Tour Guide:  Jon Picha

                    McCommas Bluff Sanitary Landfill

This is the largest landfill in Texas and is owned and operated by the City of Dallas.  It accepts waste from City collections as well as commercial haulers.  The area owned by the City encompasses 2000 acres of which approximately 1000 acres is currently being used by the landfill.  The landfill is bordered on the east by the Trinity River.  Much of the site is in a flood plain area.  The elevation of the landfill begins at approximately 320 feet and will extend up to a maximum of 550 feet.  Presently, they are up to 490 feet elevation.

McCommas Bluff Landfill Site Plan

Approximately 600,000 tons of waste is generated annually by the residents.  It is estimated that the landfill can serve current needs for about 120 years; however, new technology will possibly replace the need for landfills in about 50 years.  Currently ‘Dirty MRF’ systems for recycling waste are being tested in California.  A ‘Dirty MRF’ system accepts a mixed solid waste stream and then proceeds to separate out designated recyclable materials through a combination of manual and mechanical sorting.  The City of Dallas is investigating using this system to recover recyclable materials.  With this type of system a separate trash bin for recyclable materials would not be necessary.

a 'Dirty MRF' system for recycling of domestic waste

The McCommas Landfill is using ‘Enhanced Leachate Recirculation’ which introduces liquids into the landfill to increase production of landfill gas and also helps speed up the waste decomposition process.  When water percolates through waste, Leachate is the liquid that is produced.  Depending on the waste in the landfill, Leachate can be harmless or toxic.  There are currently water retention ponds at the site.  The water from these ponds is being pumped into the landfill.  Leachate goes to a storage tank and eventually gets pumped back into the lake.  It is not used for anything else.

landfill showing leachate piping

The leachate system is designed as a ‘layered’ system.  Leachate pipes are embedded into the landfill at every two ‘lifts’.  Each ‘lift’ being approximately 20 feet.  This means there is a new water line every 40 feet.  Every other ‘lift’ also gets a gas line.  There is a layer of ground glass at each ‘lift’ that helps percolate the water into the soil.  You can see where the gas is being extracted along the perimeter of the landfill.  There is a system for monitoring if there is gas escaping from the site.  Following is a picture of the gas extraction pipe.  These can be found along the perimeter of the landfill.

gas extraction pipe

Currently, Dallas collects approximately 5 Million cubic feet of landfill gas daily.  This gas is sold to a public utility for royalties in the amount of $1.2 Million per year.  If you include tip fees, the landfill generates revenues of approximately $15-$20 Million annually for the City of Dallas. 

Here is a short video that shows an example of a ‘Landfill Gas to Energy Power Plant'.

Following is the web page for the landfill:
 http://www.dallascityhall.com/sanitation/mccommas_bluff.html