Methane Mitigation Construction
Why do I need to do a smoke test and thickness test on my methane vapor barrier?
Quality control of methane barriers is an essential aspect of Methane Mitigation Construction. Throughout time, it was determined that spray-applied membranes are extremely difficult to install and require high skill and relevant expensive equipment. Spray-applied membranes are extremely easy to incorrectly install, which will result in a methane barrier that has insufficient membrane thickness.
The thickness of the standard spray-applied asphalt emulsion methane barrier material is 60 mils. There is a high chance of accidentally installing one with a lower thickness during the methane mitigation construction. This is why during all methane inspections, a Methane deputy inspector is required to be regularly on site to oversee the installation of a methane barrier. It is the contractor’s responsibility to ensure that they are meeting the design specifications. Still, it is the responsibility of the Methane deputy inspector to verify the results of the methane test and confirm that the methane barrier is installed per the manufacturer’s and the design engineer’s requirements.
Often, to ensure that sufficient spray-applied material is installed correctly, a thickness test measuring Methane barrier coupon thickness is conducted. At approximately every 500 ft.², a coupon is cut out of the membrane and is measured with a caliper by the Methane deputy inspector to ensure that the thickness complies with the design requirements. If the methane barrier is lacking sufficient thickness, the methane deputy inspector is required to inform the contractor that they must continue to install and spray the methane barrier until sufficient thickness is reported. This can take a significant amount of additional time, so it is important that the contractor that is being hired is experienced in Methane Mitigation systems to ensure that schedules are not deterred. Essentially, if it is found that a Methane barrier lacks sufficient thickness, it will require a minimum of an additional day to install the methane barrier again with the correct thickness.
In addition to thickness Tests, Methane Mitigation insulations will require a smoke test. Naturally, frequent void holes and inadequate sealing of seams or termination points will be present on the methane barrier during its construction and insulation. However, it is sometimes difficult to accurately locate these insufficiently sealed seams or voids. This is why a smoke test is conducted 24 hours after the curing time of the methane barrier.
The smoke test is conducted with pressurized smoke positioned beneath the foundation where the membrane is applied. This is done so that if any leaks occur, smoke emerging from the seams will make them easily patchable on site immediately. This ensures that there are no voids or areas of possible leaks within the membrane. After completing the smoke test, the Methane Mitigation contractor and deputy inspector will certify that the Methane barrier is installed correctly and that no further testing or insulation is required.
At this point, the contractor responsible for laying down the rebar and pouring concrete is required to continue with their work. This is a susceptible aspect of the Methane Mitigation Construction because it is likely that any failure in rebar installation could induce damage onto the Membrane. Although there is a protective sheet that is typically applied on top of a membrane to reduce possible damages, this is not a full-proof method of protection. Construction workers must be diligent in identifying holes and preventing any additional holes from forming inside the membrane. This is why it is often required for deputy inspectors to constantly be on site during the installation of rebar to monitor the crew and ensure that no damage is induced onto the methane barrier.