PVC Liner - Delta Landfill Fire Case Study

 

DELTA LANDFILL FIRE CASE STUDY
Submitted by: Scott Payne
Technical Sales Representative

Introduction:

In November of 1999 a fire started at the Delta Shake and Shingle site in Delta. A state of emergency was declared in Delta to help the firefighters battle the underground blaze at the landfill. A state of emergency provided the firefighters access to property and equipment and potentially funding to battle the fire. This case study examines how PVC was used in sand pad to contain the fire when conventional attempts to douse the flames were unsuccessful.

Overview:

The Delta Landfill is located beside the Fraser River. The site is a dump for demolition materials, such as wood and asphalt shakes, resulting in an environmentally hazardous smoke. At the peak of the fire it covered an area more than a hectare and burned 20 meters deep. The entire operation took over six months at a cost of four million dollars.

Design Considerations:

Since a state of emergency had been declared time was critical on this project. Conventional attempts to douse the flames were unsuccessful. The water sprayed on top of the burning landfill would just vaporize. Water that did not instantly turn into steam ran off the site carrying contaminate with it. Firefighters would set up catchments to catch the water and treat it. They were gathering about 1800 liters of contaminated water per minute. The futility of fighting the blaze with water hoses led the Delta Fire Department to the conclusion that the only way to safely put out the blaze was to dig up the burning embers, truck them away to another site and spread them over the property and extinguished them before returning them to site.

Geosynthetic Solution:

Since traditional attempts to put out the fire were not working, other methods were explored. Sperling Hansen engineers were hired to design a sand pad where the burning embers would be extinguished.

Two sand pads were constructed adjacent to the landfill on reclaimed land due to the state of emergency regulations. The sand pads were constructed with a 300mm compacted sand base, 30 mil Layfield Plastic Polyvinyl Chloride 30 mil liner and 600 mil compacted sand cover. Each pad was approximately 12,000 m2 in size. After looking at different lining options, Sperling Hansen chose PVC for the leachate collection. Polyvinyl Chloride was selected because it can be fabricated into large sized panels (up to 2,800 m2 in a 4,000 pound panel) under controlled conditions. Having the liners prefabricated by LP reduced the installation time required on site. Once on site the liner can be deployed and unfolded quickly.

Thirteen panels were required for the two sand pads:

  • 9 panels – 42.7 x 42.7 m
  • 1 panel – 30.5 m x 61 m
  • 2 panels – 59.4 m x 42.7 m
  • 1 panel – 27.4 m x 85.3 m

The PVC geomembrane panels were prefabricated in our Bellingham manufacturing plant. The material factory welds were tested for shear and peel strength (one test is performed every 5th seam) and wrapped in UV stable packaging.

Because the fire was declared a state of emergency timing was critical on this project. Sperling Hansen contacted Layfield Plastics on Friday, November 26, 1999 about the situation. We determined PVC would be the best material and that we would be on site the next day Saturday, November 27, 1999 with a crew to install the first section of the pad, which was 2 panels 59.4 m x 42.2 m and one panel 27.4 m x 85.3. The panels were unrolled and pulled into place using the general contractors (JJM) labour force.

The entire field welding of the PVC is done by hot wedge welding technology. Field Wedge welding of PVC is faster on large installations and gives a stronger seam. All repair work and secondary seaming is done with a chemical called Tetrahydrofuran. It is a solvent that works well on PVC materials.

Conclusion

Fire could have been contained if the operators of the site had adequately compacted the demolition debris within the landfill. The owners of the landfill did not and that failure allowed air pockets to become trapped underground and continue to feed the fire compounding efforts to put it out. Ministry standards require cells to have an intermediate cover of soil or sand that would limit the spread of fire. The sand layer stops the fire from migrating into other areas. Since this method was not in place, a disaster took place. Layfield Plastics fast turn around with the PVC material and its twenty-year history of experience in intallations led to a solution to put out the fire.

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