STI Engineering has been working to keep landfills in compliance for over 30 years. Over the years STI has
developed many procedures and devices to improve the ability to understand what was causing various
impacts on the environment and causing violations.
In 1978 Reg Renaud assisted in introducing the Cone Penetrometer Test (CPT) to the American market. This
instrument was used primarily in the geotechnical industry for foundation studies. In 1981 a pressure
transducer was placed in the tip of the cone and the Piezo-Penetrometer Test (PPT) was born.
It has become the best instrument for investigating the current conditions inside the waste prism of landfills.
Piezo-Penetrometer Cone
20 Ton Cone Truck 20 Ton Side-Sensing PPT Cone
PPT Cone With Extra Wiper
Internal Conduit To Expand
Vacuum Influence
Various Cone Instruments
It is possible to increase the production of existing collectors by mapping out the actual zone of influence of
the collector. If a PPT is being performed within 50 feet of an existing collector the vacuum should be
increased so that the vacuum will be very apparent if it is encountered in a zone in the PPT sounding. This
information will assist in determining the zone of influence of the collector. The PPT has shown that vacuum
influence flows outward from a collector like fingers, not like a balloon.
PPT Log For Internal Conduit
When the PPT encounters a high induced vacuum from a nearby collector and gas pressures in the same
sounding, which is common, it is not necessary to install another collector. As demonstrated in the above
diagram, an Internal Conduit can be installed using 3/4" diameter perforated PVC pipe connecting the
vacuum zone to the gas pressure layer. The PVC pipe provides a pathway for the gas pressure to flow through
to the vacuum zone and into the existing collector. The top of the PPT hole is grouted up. This eliminates the
need to connect a collector to the header and the associated possibilty of air infiltration. This can increase the
amount of gas being extracted by this collector by as much as 100%.
If this process is used around every existing collector in a landfill it could double the amount of gas for use in
co-gen. operations, without the cost of adding another collector. It will also assist in keeping the landfill in
compliance at a fraction of the cost.
At about $5.00 per foot for materials to install an Internal Conduit it can save the cost of conventional drilled-in
gas collectors. There is no well control head, no lateral and no connection to the header. Also there is no
continuing costs of monitoring, sampling and controlling another well. A 1/4" poly tube can be attached to the
top of the conduit and brought to the surface of the landfill if monitoring is required.
developed many procedures and devices to improve the ability to understand what was causing various
impacts on the environment and causing violations.
In 1978 Reg Renaud assisted in introducing the Cone Penetrometer Test (CPT) to the American market. This
instrument was used primarily in the geotechnical industry for foundation studies. In 1981 a pressure
transducer was placed in the tip of the cone and the Piezo-Penetrometer Test (PPT) was born.
It has become the best instrument for investigating the current conditions inside the waste prism of landfills.
Piezo-Penetrometer Cone
20 Ton Cone Truck 20 Ton Side-Sensing PPT Cone
PPT Cone With Extra Wiper
Internal Conduit To Expand
Vacuum Influence
Various Cone Instruments
It is possible to increase the production of existing collectors by mapping out the actual zone of influence of
the collector. If a PPT is being performed within 50 feet of an existing collector the vacuum should be
increased so that the vacuum will be very apparent if it is encountered in a zone in the PPT sounding. This
information will assist in determining the zone of influence of the collector. The PPT has shown that vacuum
influence flows outward from a collector like fingers, not like a balloon.
PPT Log For Internal Conduit
When the PPT encounters a high induced vacuum from a nearby collector and gas pressures in the same
sounding, which is common, it is not necessary to install another collector. As demonstrated in the above
diagram, an Internal Conduit can be installed using 3/4" diameter perforated PVC pipe connecting the
vacuum zone to the gas pressure layer. The PVC pipe provides a pathway for the gas pressure to flow through
to the vacuum zone and into the existing collector. The top of the PPT hole is grouted up. This eliminates the
need to connect a collector to the header and the associated possibilty of air infiltration. This can increase the
amount of gas being extracted by this collector by as much as 100%.
If this process is used around every existing collector in a landfill it could double the amount of gas for use in
co-gen. operations, without the cost of adding another collector. It will also assist in keeping the landfill in
compliance at a fraction of the cost.
At about $5.00 per foot for materials to install an Internal Conduit it can save the cost of conventional drilled-in
gas collectors. There is no well control head, no lateral and no connection to the header. Also there is no
continuing costs of monitoring, sampling and controlling another well. A 1/4" poly tube can be attached to the
top of the conduit and brought to the surface of the landfill if monitoring is required.
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The diagram below shows three instruments. The first piezo-penetrometer cone is the side-sensing
piezo-cone. This cone is used in the trash prism because it can better withstand the harsh enivronment
than the tip-sensing cone, which is the second cone shown below. The tip-sensing cone is more sensitive
than the side-sensing cone and is used in the vadose zone and native soil.
Tranducers with different pressure ranges can be installed in the cones for greater sensitivity. A porous
element is placed around the transducer chamber to allow gas or liquid to enter. Inclinometers are
installed inside the cones to insure more precise depth control.
The third cone shown below is a slide sampling cone. The slide sampler is closed and sealed with an
o-ring and pushed to the desired sampling depth. Once the depth is achieved the push rods are pulled up
which opens the screened section. Teflon tubing, attached to the sampler and is threaded through the
push rods conveys the sample to the surface, where it is collected and analyzed.
Other devices can be attached to the CPT cone which will be discussed on another page.
piezo-cone. This cone is used in the trash prism because it can better withstand the harsh enivronment
than the tip-sensing cone, which is the second cone shown below. The tip-sensing cone is more sensitive
than the side-sensing cone and is used in the vadose zone and native soil.
Tranducers with different pressure ranges can be installed in the cones for greater sensitivity. A porous
element is placed around the transducer chamber to allow gas or liquid to enter. Inclinometers are
installed inside the cones to insure more precise depth control.
The third cone shown below is a slide sampling cone. The slide sampler is closed and sealed with an
o-ring and pushed to the desired sampling depth. Once the depth is achieved the push rods are pulled up
which opens the screened section. Teflon tubing, attached to the sampler and is threaded through the
push rods conveys the sample to the surface, where it is collected and analyzed.
Other devices can be attached to the CPT cone which will be discussed on another page.
Yellow - Indicates gas pressure layers.
Pink - Indicates an applied vacuum from a
nearby collector.
Note the layers of gas between the layers of
vacuum.
A 3/4" diameter PVC Internal Conduit with
slots placed across the gas layers and the
vacuum layers, giving a pathway for gas to
the collector.
The top portion of the conduit was grouted in.
Pink - Indicates an applied vacuum from a
nearby collector.
Note the layers of gas between the layers of
vacuum.
A 3/4" diameter PVC Internal Conduit with
slots placed across the gas layers and the
vacuum layers, giving a pathway for gas to
the collector.
The top portion of the conduit was grouted in.