In early November 1999, landfill owners at the Delta Shake and Shingle Landfill in North Delta, Canada, sounded the alarm. It was just about midnight when smoke began to fill the air. A 250,000-cubic-yard cell in the landfill had erupted in flames. The landfill operator tried to put out the fire, but initial efforts only accelerated combustion of the construction and demolition (C&D) waste.
A few weeks later, with the landfill still burning, the city became worried. Smoke from the fire began to cast a thick haze over the nearby Vancouver skyline. Streams in the area were threatened by leachate pools forming from the firefight, and workers on adjacent properties were being affected by smoke and odors.
On November 27, Delta's Mayor declared a state of local emergency, and the British Columbia Fire Commissioner ordered the Delta Fire Department to extinguish the blaze.
But quelling a landfill fire is not that simple, firefighters found. Complicating their efforts was the presence of a high-pressure natural gas main that provided heating fuel for nearly half-a-million customers in Vancouver, as well as a large-volume sewer force-main, a water supply main, a high-voltage transmission line and a railway line. All of these utilities were located adjacent to the landfill in unstable peats, and were potentially threatened by slope failure or excessive settlement.
Additionally, careful attention had to be paid to the geotechnical design and monitoring of the areas on top of and adjacent to the landfill to avoid stressing or displacing the nearby gas pipeline.
With these things in mind, the fire department created a strategy to close the 200-yard by 200-yard burn zone, rapidly construct PVC-lined cool down areas on expropriated property, excavate and wet down the burning material, and ultimately replace the extinguished material back in the landfill.
Nary a Spark The Delta Shake and Shingle Landfill is a privately run C&D facility located in North Delta, near Vancouver, British Columbia. Developed on a soft foundation, including organic peats, unconsolidated clays and silts, the landfill began operations in 1989. It was permitted to receive 20,000 tons of waste per year. And by November 1998, almost the entire 32-acre footprint was covered with waste to a height of 60 feet above grade, with the exception of a horseshoe-shaped area on the north side. The landfill was developed in 10-feet-high lifts that were capped with soil and/or a hog fuel (shredded wood waste) intermediate cover. The horseshoe originally housed the scale and administration facilities.
To maximize revenues, the new landfill owner, who purchased the property in 1998, relocated the scale and offices onto an adjacent property north of the railway tracks and began to fill in the horseshoe. The bottom of the horseshoe first was covered with a 10-foot to 15-foot thick lift of inert concrete and blacktop demolition material from the 1986 World's Fair Expo site.
During the next 10 months, the landfill received a steady stream of demolition waste, including crushed dimensional lumber, tar roofing shingles, plastic and metal. Because materials were pushed into place with a bulldozer, the waste was loosely deposited in a single 50-foot deep layer throughout the entire horseshoe without proper compaction or soil fire breaks - contrary to operating permit requirements.
After issuing several non-compliance citations to the landfill, the British Columbia Ministry of Environment, Lands and Parks (MoELP) ordered the landfill to close on Nov. 9, 1999. But by that time, more than 250,000 cubic yards of waste already had been deposited in the horseshoe.
Anyone Smell Smoke? Ironically, steam and smoke had been emerging from the site for several weeks before the closing, but no one realized the landfill was on fire until flames broke through the surface on Monday, Nov. 8 around midnight, when the landfill owner placed a 911 emergency call. The Delta Fire Department responded with several pumper trucks that brought the surface fire under control during the next 24 hours. Managers thought the problem had been solved.
However, on Wednesday, Nov. 11, when a 50-yard by 100-yard sinkhole fell approximately 10 feet on the crest of the horseshoe and flames erupted on the steep face, the Delta Fire Chief realized that the fire was much more complicated than he first believed.
Concerned that the fire would spread, Delta Shake and Shingle operators began excavating 20-foot deep trenches around the burning areas, which they completed on Sunday, Nov. 14. But it quickly became apparent that these trenches would not be effective in stopping the fire because they penetrated less than one half of the fill thickness.
Seeing it was time to bring in a landfill fire specialist, the owners hired North Vancouver-based Sperling Hansen Associates (SHA) on Nov. 12. SHA's plan involved establishing perimeter fire guards down to solid soil around the horseshoe, excavating and extinguishing all burning material from the horseshoe, and conducting thorough geotechnical monitoring to ensure that surrounding utilities would not be damaged by the firefighters' efforts. A previous slope failure at the landfill had displaced the gas pipeline by more than 10 feet and had resulted in several million dollars in damages.
Sound the Alarm Over the next few days, the fire gained intensity. Fearing a serious environmental emergency, the British Columbia Fire Commissioner on Nov. 25, ordered the landfill to extinguish its fire following SHA's plan. However, because of the large anticipated cost of extinguishing the fire, the company ignored the order and eventually went into receivership.
By this time, smoke from the plume was starting to pose a health hazard to adjacent businesses. A thick haze began to choke much of the Delta area. Additionally, the potential spread of fire into the main landfill posed a serious threat to the British Columbia gas pipeline. Leachate from the firefight also began to pool, and was starting to affect the environment and threaten groundwater resources.
Consequently, the British Columbia Fire Commissioner determined that the fire was posing a serious threat to life and property and ordered the Delta Fire Department to extinguish the landfill fire according to SHA's plan on Nov. 27, 1999. To alleviate the landfill owner's cost concerns, the British Columbia Provincial Emergency Program (PEP) committed to help fund the effort.
However, some of the adjacent private property owners were less than cooperative. So to secure access, the Corporation of Delta's mayor declared a local state of emergency.
By Nov. 27, much of the 250,000-cubic-yard horseshoe was in flames, and a thick plume of smoke was rising into the skies.
Forming the Fire Safety Plan To extinguish the blaze, firefighters knew they had to eliminate one of three ingredients: the fuel supply, oxygen or the high-temperature ignition source. SHA considered six methods, including:
- Accelerating high-temperature combustion;
- Capping the landfill burn area with soil;
- Capping the landfill burn area with a geomembrane;
- Flooding the burn area with water from the nearby Fraser River;
- Injecting an inert gas such as CO2 to displace oxygen; and
- Excavating the burning material and then extinguishing it with foam.
The only feasible solution that seemed apparent to the SHA team was to excavate the burning material then transport it to an area where it could be soaked with water and fully extinguished. Specialists from Key Safety in Red Dear, Alberta, which were retained by the Delta fire chief confirmed the strategy.
The idea of accelerating the burn was abandoned due to air quality concerns and the risk of spreading the fire into the landfill's main fill zone. Because operators did not want to risk further slope failures, they could not cap the landfill with soil. Applying a geomembrane cap was not practical on the steep slopes approaching 1.5 horizontal:1 vertical. Also, firefighters were concerned that the membrane would melt before the fire was extinguished. Flooding the burn area with large volumes of water was not pursued due to geotechnical stability concerns and potential leachate impacts. And, oxygen displacement using CO subscript 2 was not feasible because of the waste's porous nature and the lack of cover soils that would prevent the injected gas from escaping.
Rescuers to the Scene SHA's first step in controlling the fire was to fill in the trenches previously excavated by the landfill owner. This reduced the amount of air fanning the burn and made the landfill surface safer. Next, firefighters smothered the fire zone with a 6-foot to 10-foot thick lift of refuse. For two days, two bulldozers covered the fire zone with unburned waste to limit oxygen. This dramatically reduced the burn rate and the amount of smoke.
Initially, water was applied to the fire in high-pressure streams in excess of 2,000 gallons per minute (gpm). This extinguished flames at the surface but did not quell the fire brewing deep in the landfill. In fact, most of the water quickly ran off the surface, draining to the landfill toe where pools of toxic black leachate were forming. So, to improve the effectiveness of the monitors, operators misted the water at a reduced rate over the fire. To improve penetration, a Class A foam was added to the water.
Moving Material Once the blaze was under control, the team mobilized two large excavators and six Caterpillar D350D articulated off-road trucks to excavate and transport burning waste from the horseshoe to the cool down areas. To avoid the nightmare of the landfill's main fill zone igniting, excavators worked around the horseshoe's perimeter until a reliable fire guard was established down to inert soil and concrete rubble. Only at that point did the firefighters work over the remaining 250,000 cubic yards.
To ensure safety, each excavator worked with a spotter throughout the firefight. The spotter also used an infrared temperature sensor to screen each bucket load placed in the truck. If all material placed in the truck was below 122 degrees, it could be sent to the cold storage area. Loads above that temperature were directed to the hot pad where they could be extinguished. Screening the excavated material also reduced by approximately 45 percent the amount of product that required extinguishing.
Hot loads were transported to two large pads that were constructed on industrial properties north of the landfill. There, firefighters spread out and foamed the burning material. The hot pads, each approximately 100 yards by 150 yards in area, were constructed using a 20 mil polyvinyl chloride (PVC) membrane liner on top of a 12-inch sand cushion layer to prevent leachate loss and avoid contaminating the private properties temporarily expropriated during the firefight. A second 18-inch sand cushion layer was placed over the PVC to provide protection from above.
Lined ditches were constructed around the pad perimeter to collect leachate and convey it to a central sump. Water collected in the sump was recirculated into the firehoses to minimize the amount of leachate needing discharge and to reuse Class A foam additives.
A Careful Watch Throughout the firefight and landfill restoration, Horizontal Engineering, SHA's geotechnical subconsultant, conducted geotechnical temperature and gas composition monitoring to ensure that firefighting activities would not lead to a slope failure and that the fire was not spreading into the main fill zone.
To determine whether earth-moving activities - particularly relocation of the cold waste to the top of the landfill and construction of storage areas adjacent to the sewer and water mains - were causing instability in the utility corridors, Horizon installed a network of geotechnical instrumentation and monitored it daily. Nine inclinometers capable of recording as little as 0.1 inch of deflection provided the primary warning mechanism against excessive movement.
Also, Horizon established total station survey benchmarks along the crest and mid-slope on the north and south landfill sides, and along the sewer main/water main right-of-way. Workers also installed piezometers that measured water levels in the fill zone to provide early warning of pore pressure buildup within the refuse, which could potentially trigger slope failure.
The geotechnical monitoring program confirmed the effectiveness of the height restrictions on storage piles and setbacks from utility corridors. Movements in all sensitive areas proved to be less than 1 inch.
As the fire spread throughout the horseshoe, the firefighting team became concerned that the fire would spread into the main fill zone, especially when they discovered a fire on the back side of the landfill (later determined to have been a separate spontaneous combustion). Consequently, to establish how far the fire had penetrated within the landfill, thermistor strings were installed in five boreholes around the horseshoe. Temperature measurements were obtained by lowering three thermistors into the cased boreholes at 15 feet, 30 feet and 45 feet below surface.
The hand-held infrared heat sensors also were used to monitor temperatures from surface vents and test pits. Based on this experience, SHA concluded that temperatures above 167 degrees Fahrenheit are a strong indication of a fire.
Gas composition monitoring also provided additional data about the location and intensity of the fire. Landfill areas that were on fire showed carbon monoxide concentrations above 1,000 parts per million (ppm); oxygen levels between 15 percent and 20 percent; and little, if any, methane. On the other hand, landfill areas that were not on fire exhibited elevated methane concentrations (20 percent to 45 percent), no oxygen and little carbon monoxide (less than 100 ppm).
Restoring the Land Nearly two months after the firefighting began, the landfill was finally extinguished on Jan. 18, 2000. Because there was pressure on the municipality to return the expropriated lands to their owners quickly, placing the extinguished material back into the horseshoe became a priority.
To ensure that fire would never again spread from the horseshoe into the main fill, the entire horseshoe area was lined with 3 feet of clay to provide a continuous and reliable fire wall. Extinguished waste then was placed back into the landfill in cells that measured 40 yards by 75 yards by 4 yards deep. The waste was thoroughly compacted during placement. Each cell was covered with 2 feet of inert soil cover prior to placing of the next overlying lift.
The SHA team worked with local excavation contractors to obtain clean cover soil for free in return for providing them with a free dump site.
Although SHA originally anticipated that available air space would not be sufficient to hold all the extinguished product and extra cover soil, in the end, proper compaction reduced the refuse volume by more than 40 percent. Also, SHA noted that if the landfill had been compacted properly beforehand, the fire may not have started or spread as quickly, and the operator would have been able to generate more revenue from his operation.
Lessons Learned This experience provided several key lessons:
- Uncontrolled deposition and poor compaction of demolition waste can pose an extreme fire hazard.
- Spontaneous combustion presents the most likely triggering mechanism for fires at C&D landfills.
- Soil berm fire guards, which were created around the horseshoe, can be effective in containing fires.
- Refuse should be placed in cells no larger than 20,000 cubic yards, and each cell should be fully encapsulated within 2 feet of inert soil material, not ground wood waste.
- During a fire, excavating shallow trenches that do not fully penetrate the refuse is ineffective. Trenches should be excavated only if they can penetrate the full thickness of refuse reaching inert material.
- Regulations should be strictly enforced to ensure that poorly managed landfill operations are shut down before large fire liabilities are accrued.
- Fire insurance should be a mandatory requirement at all C&D landfill sites.
In total, extinguishing the fire for slightly more than two months cost more than $2 million (Canadian). Currently, extinguished material is being placed back in the landfill in a fire-proof manner, and properties expropriated during the fire fight are being restored to their owners.
Strong evidence suggests that the Delta Shake and Shingle Landfill was caused by spontaneous combustion. Sperling Hansen Associates Inc., North Vancouver, British Columbia, Canada, noted that the second fire, which broke out on the back side of the landfill midway through the firefight, was in an old, inactive area of the site filled with mixed roofing material and wood waste. Because the fire started beneath a 6-foot-deep berm that was not accessible from the surface, spontaneous combustion was determined the most likely ignition mechanism.
However, the mechanics of spontaneous combustion in refuse are not well- understood. Wood starts to burn with an open flame once temperatures rise above 600 degrees Fahrenheit. Pyrolysis, the process by which wood chemically oxidizes, can start at temperatures of 200 degrees Fahrenheit. The reaction becomes exothermic (heat-producing) and self-sustaining at temperatures as low as 300 degrees Fahrenheit.
But, temperatures approaching the 300 degrees Fahrenheit ignition point seldom are reached in properly operated landfills where refuse decomposition is occurring under anaerobic conditions. Anaerobic bacteria thrive at temperatures that seldom exceed 140 degrees. Aerobic bacteria generally thrive at temperatures below 167 degrees and typically die once temperatures climb above 176 degrees.
Thus, heat released during rapid oxidation of pyrophoric substances in the landfill is believed to be the triggering mechanism that elevates internal temperatures above the 300 degrees Fahrenheit required to create spontaneous combustion in wood. Common pyrophoric substances include rags soaked in vegetable oils, linseed oil, low-grade coal, grass, straw and certain metal compounds such as iron sulphite.
Besides spontaneous combustion, other potential causes of landfill fires include:
- Embers in a hot load;
- Careless smoking;
- Methane flash from an equipment spark; and
The first step in any firefight is to ensure protection of all firefighters and support staff involved. To combat the Delta Shake and Shingle fire, a comprehensive health and safety program was developed in cooperation with the Workers Compensation Board of British Columbia (WCB) and implemented before firefighters were permitted to enter the fire zone. The health and safety program involved:
- Controlled access and site security;
- All persons sign in and sign out;
- Radio communication;
- Air horn warning;
- Spotters working with all equipment;
- Onsite first-aid attendant;
- Warning fences around all trenches; and
- Daily safety meetings.
All workers also were required to wear the following protective equipment:
- Fit-tested respirator (fit certified);
- Hard hat;
- High-visibility vest;
- Steel shank/toe boots;
- Gloves; and
- Safety eyewear.
A key aspect of the health and safety plan was determining whether it would be necessary for all workers to wear self-contained breathing apparatus (SCBA) in the fire zone. SCBA use would have resulted in a significant burden on firefighters and hampered progress.
Fortunately, air composition testing conducted by the Greater Vancouver Regional District (GVRD) determined that the smoke was not acutely toxic and that properly fitted respirators would provide adequate protection to field personnel.
Based on experience gained at Delta Shake and Shingle and other landfill fire projects, temperatures above 167 degrees Fahrenheit are cause for alarm, and temperatures above 200 degrees Fahrenheit are a very strong indication that a fire exists. Following is a practical reference guide to evaluating field temperature measurements.
140 degrees Fahrenheit Anaerobic Decomposition <167 degrees Fahrenheit Aerobic Decomposition 176 degrees Fahrenheit Microbes Die-off 200 degrees Fahrenheit Pyrolysis Starts 300 degrees Fahrenheit Exothermic Oxidation of Wood Starts 600 degrees Fahrenheit Wood Ignites Spontaneously (Combustion)