EMERGENCY: Engineers help fight landfill fire in Delta

A massive effort to control and extinguish a fire in a construction waste landfill has earned a 2001 Award of Merit for engineering excellence from the Association of Consulting Engineers of British Columbia. Several engineering firms helped to contain the potential disaster in Delta, B.C.

The fire broke out in the Delta Shake and Shingle landfill site early in November 1999. The site owner’s efforts to extinguish the combustion only made matters worse, and by the end of the month the fire was casting a thick haze over the Vancouver skyline. After a state of emergency was called on November 27, Delta’s Fire Chief took charge and delegated tasks to the consulting engineers who won the award. Sperling Hansen Associates looked after the fire control plan and environmental issues, and Horizon Engineering with Knight Piesold oversaw the geotechnical and engineering design.

The team quickly had to find a way to contain and move the huge amount of burning material out of the pit and onto adjacent pads where it could be doused and the fire extinguished. In total, 1,400 cubic metres of hot waste and 43,200 cubic metres of cold waste was excavated and trucked to “lay-down” pads.

These two-hectare pads had to be constructed in less than a week under difficult conditions. The subsurface was unstable and shifting, so the engineers had to drill and test extensively to calculate what were safe heights for piling the excavated material. Nearby is a major gas pipeline — had it been fractured it would have caused a catastrophic failure. Smoke hampered the crews’ vision and breathing as they worked, and access across the soils and adjacent peat bogs was treacherous. Heavy drilling equipment and excavators had to be tracked across the unstable fill, and the only access for trucks was across a water and force sewer main.

Six weeks and four million dollars later the fire was extinguished and the material could be returned to the fill. This time the waste was compacted in cells and covered with inert soil to form fire breaks.

The potential environmental impacts of the fire could have been disastrous, especially if it had spread to the main fill area. Tar and plastics in the burning waste emit large quantities of air pollutants including dioxins and furans. And water was applied at 1,300 litres per second to the fire, which meant there was a danger of run-off toxins damaging the local habitat that contains endangered species. To offset this risk, the engineers designed a leachate collection system, which was constructed in 24 hours. A lined aeration lagoon was built to provide low cost on-site treatment, and much of the fire-fighting water was recycled back into the pumps.

Besides the consulting engineers mentioned above, other local firms who helped in the efforts were Kerr Wood Leidal, McElhanney Consulting Services, Key Safety, and the contractor, JJM Group.

EVENT: Sprinkler changes identified at CFSA

Changed requirements for automatic sprinklers were the topic at a Canadian Fire Safety Association meeting in January in Toronto. Kevin Maughan of Tyko International came from the U.S. to speak about the changes introduced in the 1999 edition of NFPA 13, the National Fire Protection Association standard for the installation of sprinkler systems.

Maughan first pointed out just how complex the work of designing fire protection has become by holding up what was the standard “bible” when he started in the business in 1980. He compared this thin red NFPA pamphlet to today’s equivalent publication — a heavy reference tome at least one inch thick. He noted that criteria for sprinkler systems are now mentioned in over 40 NFPA documents, covering everything from transit system guideways to places of worship.

One major change in the 1999 edition of NFPA 13 is that from this year every manufacturer has to permanently stamp a unique SIN number on each sprinkler to identify the type. The number consists of a letter prefix — each manufacturer has its own — followed by four digits. The rationale for the new system is to make it possible to identify the equipment more precisely and avoid the confusion that arose when every manufacturer used different names for their models. Tyco has adopted a numbering system whereby the first of the four digits will represent the orifice size, the second orientation, the third operating element and the fourth hazard. Among other changes, the revised NFPA 13 brought in new obstruction criteria and coverage rules for residential sprinklers.

Maughan also discussed at length new extended coverage sprinkler systems for big box storage areas. And he talked about how Factory Mutual is testing alternative anti-freezes for sprinklering refrigerated storage areas. Some of the big problems with sprinklering such facilities is that the systems tend to plug up with ice. When false alarms trigger a water flow, the water freezes and piping sections have to be replaced. Maughan mentioned that a 1993 survey in Milwaukee found that 90% of sprinkler systems in refrigerated facilities had ice plugs, and 45% were completely blocked.

Maughan explained that Factory Mutual has recently tested three antifreezes for use in commercial systems: calcium chloride (used in ice hockey rinks, but corrosive), potassium acetate (an airport de-icing fluid that has a pungent smell), and potassium lactate (USDA approved as a food additive). He recommended the merits of potassium lactate, but noted that it is more viscous than water and might need more pressure at the sprinkler head.

Maughan’s final remarks were to praise the merits of a simple fire protection design, “A stupid system is the best system,” he said.

RESEARCH

Risks found with handheld fire extinguishers

Tests by the NRC/Institute for Research in Construction’s Fire Risk Management program in Ottawa have found some risks when handheld fire extinguishers containing halocarbon streaming agents are used to fight fires in small compartments. The tests were done in partnership with the Department of National Defence using four different halocarbon extinguishers. Extinguishers that use halocarbon streaming agents such as FE-36, Halotron I, FM-200 and CF3I instead of ozone-depleting halon are now commercially available.

A series of experiments was done using the extinguishers on liquid fuel fires of different intensities in small compartments (45 m3 and 120 m3) and in a large burn hall (21,000 m3).

The tests found that in all the test scenarios the concentrations of the streaming agents were below the levels that would pose a health risk to the operator or other personnel according to the toxicity restrictions of the U.S. Environmental Protection Agency.

However, in the small compartments, the tests showed that dangerous levels of acid gas by-products were generated during fire suppression. Hydrogen fluoride (HF) was one of the major by-products, and one extinguisher produced hydrogen chloride (HCI). Exposure to intense heat from the fires was another safety concern, especially in small confined spaces.

The research indicates that operators of such extinguishers in small confined spaces must have self-contained breathing apparatus and wear heat-protective clothing. It would also be important to take measures to prevent potential corrosion to sensitive equipment since acid gases are a by-product of halocarbons. –Source Construction Innovation, Winter 2001.

Let them burn?

The growth in big-box distribution centres in the United Kingdom has spawned a radical new approach to fire risk.

Some of these single-storey sprawling sheds are being designed simply to burn down in a fire. While U.K. rules require a retail outlet of more than 2,000 square metres to have sprinklers, they are not required in certain other warehouse buildings. Their owners have consequently decided that it is more economical to let the buildings burn rather than installing fire protection and suppression systems. As long as the occupants can be safely evacuated, they’re prepared to sacrifice the buildings themselves. Apparently, the insurers have gone a
long with this approach.

The Midlands chapter of the U.K.’s Institute of Fire Engineers held a conference in March involving firefighters, engineers and code authorities to study the issue. They looked at a typical case of such a disposable building, 150 metre x 150 metres large, 13 metres high, with 11 metre-high storage racking. The warehouse might contain up to 60 workers at any time, but the “engineered solution” to fire protection simply assumed the workers would evacuate in time.

Steve Rowe of the Institute of Fire Engineers is one person with concerns. He says that some of these disposable buildings have escape routes as long as 75 to 100 metres, which might leave the margin of safety too tight, especially since the buildings could flash over into a fire within five or six minutes and people don’t always act as predicted.

The Institute was to hold a follow-up session this spring to look at the environmental aspects of the burn-down approach. British engineering firm Ove Arup was investigating the potential problems.