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Push-In Collector
Landfill operators are realizing that it is important to retain the liquid found in the upper portions of a landfill where the freshest refuse is located. If a large diameter collector is blindly drilled into and through a liquid layer, this liquid will drain to the bottom of the landfill and into old refuse and possibly to the groundwater. For co-gen. operations it is important to keep the liquid where it will produce the most LFG.


Once a 3-D Profile is completed the information can assist in designing a collection system to address a compliance problem or to just recover LFG for a co-gen plant. The profile will provide data that will indicate where the screen sections of a collector should be installed, which should be only where the LFG is being produced. The PPT rig is used to push-in a 2" diameter steel collector at 1/3 the cost of 4" PVC collector.
The figure below describes a 2" diameter steel push-in collector installation.

The table below is a comparison between the PPT method and the conventional drilling method.
Cost Comparison


Based on California prices the following is a cost comparison between the 2" dia. steel push-in collectors and larger diameter collectors.


A 100-foot deep PPT sounding and a 2" diameter steel collector costs about $16.34 per foot.


A 100-foot deep 4" dia. PVC collector by hollow stem auger, costs about $38.80-43.90 per foot, depending on the cost of cuttings disposal.


A 100-foot deep 24" dia. bucket auger with 4" dia. PVC costs about $55.00-75.00 per foot, depending on the cost of cuttings disposal.


Currently, 4 inch and larger diameter collectors are installed in landfills for two reasons. One is to accommodate a water pump in case it floods. The second reason is that it is thought that it will produce more gas. However, these collectors are connected to the header with 2"-3" dia. laterals and the valve that is placed in the line is opened only a fraction of an inch because otherwise it will overpull and pull in air. Why spend money on larger pipe when it will not be used to it's fullest capacity. The PPT will prevent the placement of the 2" dia. pipe into an area where there is liquid to flood the collector so no pumps will ever be required. A landfill will never produce enough gas to exceed the flow capacity of the 2" pipe, thereby saving costs.


In conclusion, the PPT Profile and Push-in steel collectors are better, faster and cheaper than standard drilled collectors.

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