BY SAKARI HALMEMIES, YRJÖ MÖTTÖNEN, AND TUULA TUHKANEN
Most chemical accidents occur during the transportation of hazardous materials.1 Gasoline tankers, the most common types of large-capacity trucks carrying hazardous materials on the road, are often involved in such incidents.2 In these incidents, the emergency services mainly are restricted to preventing the spread of chemicals on the ground or on the surface water and recovering the spilled chemicals from pools. The present methods of recovering liquid contaminants from the soil consist mainly of excavation and disposal of the contaminated soil or the pumping of liquids from excavations. However, when liquid petroleum hydrocarbons, such as fuels, are released into the subsurface, they can be best recovered as mobile during a free phase, before sorbing into the soil particles. At the moment, emergency services lack this kind of response method.
The power slurping response (PSR) was developed to satisfy this need. An effective vacuum extraction-based response (power slurping) can minimize environmental consequences by effectively recovering fuel, restricting its spread in the soil, and even preventing groundwater pollution—the prime target of PSR.
The existing vacuum extraction-based techniques (soil vapor extraction, dual-phase extraction) are normally applied to a weathered soil, after the fuel has remained in the soil for an extended time, spread, and changed. Therefore, a yield cannot be more than vapors with a small capacity. Because the spill is fresh and the vacuum is much higher when using the PSR, the yield could be both liquid and vapors, and the total recovery is considerably greater than with traditional vacuum-based extractions. The idea of the PSR is to decrease the fuel concentration below the retention capacities of the soil in question during the first hours. In permeable sandy soils, gasoline could reach the groundwater during the first two hours if no response actions are taken. To our knowledge, vacuum extraction-based techniques have not been used earlier as an emergency response method.
 (1) A jeep and a trailer transport the SAMI-response equipment. (Photos courtesy of authors.) |
null
MATERIALS AND METHODS
The PSR technique has been studied for two years. The aim was to develop vacuum extraction-based response equipment for the emergency services. The first tests were conducted with small columns; fresh fuel spills were successfully recovered from different soils using a strong vacuum.3 Bigger column tests concerned determining the seepage velocities of fuels in different soils and the retention capacities of soils for different fuels. By combining the existing equations of the seepage and vaporization, a simplified gasoline spill model was developed.4 The last experiments concentrated on the development of vacuum-based response equipment by testing it first in a tank and then in a big basin (29.5 2 29.5 2 9.8 ft.). The response equipment is comprised mainly of a vacuum pump, a collection tank, an incinerator, and perforated pipes with hoses. During basin experiments, the possibility of recovering 100 liters of fuels from different soils (gravelly sand and sandy till) were studied. The best results were achieved in the most vulnerable environment, in a sandy soil, where an easily volatile gasoline was recovered.5
 Table 1. Comparison Between the SVE and the PSR Technologies |
null
Table 1 shows the comparison between the traditional soil vapor extraction (SVE) and the power slurping response (PSR), developed for an acute emergency use.
SAMI-RESPONSE EQUIPMENT
 |
As a result of the experiments mentioned before, so called SAMI-response equipment was developed and manufactured, mainly for emergency services’ responses to accidental fuel spills on the ground but also for other trained persons. The SAMI-response equipment uses a strong vacuum extraction in which any volatile hydrocarbons, especially fuels, can be effectively recovered from the soil as a liquid and as vapors. Vapors are continuously separated from the liquid in the collecting tank under a vacuum by a spiral perforated pipe: Vapors go to an incinerator for controlled burning. The SAMI-response equipment is easy and quick to use and can be transported to an accident site in a trailer. The working principle of the SAMI-response equipment is shown in Figure 1. When liquids with a low vapor pressure and low flammability (i.e., diesel and heating oils) are pumped from a pool, the collecting tank can be bypassed, and the vacuum pump can be used for transferring the liquids from a pool directly to a temporary basin.
POWER SLURPING OF FLAMMABLE LIQUIDS
Let’s imagine a typical road accident during the transportation of fuels as an example. As a result of a tanker’s turning over, 2,642 gallons of gasoline spills on the ground. It is summertime, and the ambient temperature is 20ºC, 68ºF. Emergency responders are normally at the accident site 15 minutes after receipt of the alarm. On arrival at the scene, their first actions depend on whether there is a fire or a fuel spill.
Fire
If there is a fire and it threatens people or the environment, the fire is extinguished first. If the fuel is burning only on the ground and there is no danger the fire could spread into the tanker or the environment, it could be allowed to burn until it is under control.
No Fire
If there is a pool of gasoline but no fire, the gasoline is covered with foam, after which both the fuel and foam are pumped from the pool to a temporary basin using a vacuum pump and a suitable suction head of the SAMI-response equipment. In this case, the collection tank is bypassed. When all visible liquid from the ground has been recovered, or if there is no pool of gasoline at all, the PSR can be started.
Power Slurping Response
First, for safety and to minimize an ignition risk, the spill area is covered with an extinguishing foam or powder. The risk of fire is very small and controllable, because there is not enough oxygen in the soil to maintain a bigger fire. Then a minimum of two perforated pipes are sunk in the center of the spill area to a depth of about 3.9 feet using a drill and a hammer. If the first responders arrive at the accident site during the first half hour, the fuel will not have penetrated more than 3.3 feet. After that, or simultaneously with it, the vacuum pump would be grounded, and antistatic hoses would be coupled between the suction pipes and the collecting tank, the transfer pump and the temporary basin, and the vacuum pump and the incinerator; the latter would be in a safe place upwind from the spill area (an explosimeter would help determine a safe place for the incinerator). The vacuum pump can be started after igniting a pilot flame of propane in the incinerator burner.
 2) The SAMI-response equipment in use. |
null
With the aid of the peristaltic pump, a vacuum is generated in the collecting tank (for example, 0.5 bar—see Figure 1), and fresh gasoline, as a liquid and as vapors (because of the vacuum, gasoline is recovered mainly as vapors), enters into it through a suction pipe. If a vacuum is low, it can be improved by covering the spill area with plastic such as polyethylene. To maximize a yield, it is useful, by lifting perforated pipes in holes and by measuring simultaneously with an explosimeter fuel concentrations from a sample incinerator valve, to find the right depth for the pipes for the extraction that will produce the highest fuel yields. Liquid and possible solid particles will be collected from the bottom of the tank, but vapors are sent by the vacuum pump to the incinerator and burned. Emptying the collecting tank to the temporary basin is done by the same vacuum pump after stopping the extraction for a short time and turning valves. Occasionally, it is useful to increase the vacuum in the collecting tank with a few minutes’ throttling of the closing valve in action. Vacuum peaks keep holes in the suction pipe clear and improve a yield. When extracting a fresh spill of gasoline, the vapors are combustible (> 1.4 v-%). Therefore, use only propane if you want to burn lean vapors of gasoline (< 1.4 v-%) for a cleaner release into the atmosphere.
Power slurping continues with a perforated pipe as long as the vapors burn. After that, extraction continues from other suction pipes. To treat a larger spill area, a few suction pipes (about six pieces) must be sunk in different places of the spill area. The same suction pipe can be raised from the soil with a special tool after the extraction and be sunk into another location.
The main purpose of the PSR—to stop the spread of fuel in the soil—can be achieved in a few hours, but the extraction needs to be continued to lower the fuel concentrations in the soil. Depending on the soil, a lot of gasoline (and particularly diesel-like more viscous and less volatile liquids) can be recovered directly from a pool. However, the longer the gasoline pool remains on the ground surface without penetrating the soil, depending on weather conditions, as much as 20 to 30 percent of it will vaporize into the atmosphere. The diameter of the fuel pool and the speed of the wind greatly affect the vaporization rate. (4) The maximum recovery of gasoline from a sandy soil with the SAMI-response equipment can reach 66 gallons/hour.
INCIDENTS AT WHICH PSR COULD HAVE HELPED
Two incidents at which PSR could have been used successfully are described below.
Gasoline Spill in Ragunda
On July 30, 1997, at 7:30 p.m., a tanker-trailer transporting 12,416 gallons of gasoline overturned in the Ragunda community of Sweden. A total of 4,887 gallons of gasoline leaked into the soil of gravelly sand. During the first two hours, half of the spilled gasoline had reached the groundwater 26 to 33 feet below the ground surface. It was later estimated that the seepage velocity of the gasoline was more than 1.1 feet/minute.
During the first hours, a fire brigade plugged a leak in the wall of a tank, covered the spill area with foam, and put temporary basins below the tanker’s leaking holes. A crane, an excavator, and an empty tanker were ordered to the site. The tanker was emptied at 4 a.m., and the trailer was lifted at 8:30 a.m. the next day. During the afternoon, the polluted soil was dug up; a total of 298 tons of polluted soil was removed from the accident site. Booms were used to protect a river near the accident site. The fire brigade stopped its acute response work at 12 p.m. on July 31.
The remediation work included the soil vapor extract (SVE), which began three weeks after the accident. The SVE took more than seven months, recovering an average of 18.5 gallons/day. An estimated total of 3,963 gallons of gasoline was recovered as follows: approximately 1,453 gallons were extracted; more than 1,057 gallons were excavated and transported away; about 1,057 gallons were expected to resolve biologically; and a few hundred liters were removed from the pumped groundwater. The remediation cost $200,000 to $400,000 or euros.6
If the SAMI-response equipment had been used in this case, the PSR could have begun 15 minutes after the fire brigade arrived at the site, and the remediation costs could have been lowered remarkably. It is impossible to say whether the pollution of the groundwater could have been prevented, but the environmental consequences could have at least been minimized. A need for a massive excavation probably could have been avoided.
Vacuum extraction makes a great difference, whether it is done when the spill is fresh or after the spill has weathered for three weeks. It is much easier for the emergency services to start a vacuum because it is a part of their acute response than it is for environmental organizations to start the SVE, which in many cases requires special permits. On the other hand, emergency services—unlike many other organizations—are accustomed to working under explosion and fire hazards. Environmental consequences can be best minimized when there is cooperation between the emergency services and the environmental experts.
Leakage of Underground Pipe of Liquefied Petroleum Gas in Finland
On February 9, 2001, there was a massive leak of highly flammable liquefied petroleum gas (LPG) from an underground pipe connected to an aboveground tank holding 12,944 gallons of LPG in Finland. The accident took place in a cardboard factory in the Juankoski region. As a result of the leak, it was observed a few days later that 16.5 to 22 tons of LPG leaked into the soil. Some of the LPG vaporized, some poured into the nearby river, and some remained in the soil. Because of the fire and explosion risk, the factory area was isolated for four months. The LPG tank had to be emptied, which caused the stoppage of a coating machine (a lamination machine in a board mill) for 10 hours. According to measurements made by consultants, the nearby river included 12 mg (26 millipounds) of LPG/liter water. Moreover, there were flammable LPG concentrations inside buildings in the factory area. On February 13, there was still an explosion risk in one of the buildings. The buildings were safely ventilated, but there was no way to recover the heavy LPG gas from cavities in the soil. The presence of the LPG in the soil was determined by soil vapor samples taken by extraction.7
A consulting company began SVE about four weeks after the leakage. The process took a full year, because the LPG had drifted to a nearby ridge and moved from one place to another. Remediation costs were about $50,000 or euros.9
Again, if the emergency responders had used SAMI-response equipment, they would have been able to start a PSR immediately and would not have been delayed for the four weeks it took to prepare for the traditional SVE technique. The remediation costs could have been lowered. In addition, the isolation period for the site would have been shortened.
The Finnish company Pohjois-Savon Palontorjunta Oy began manufacturing the SAMI-response equipment in 2002. That same year, the Finnish Emergency Services College in Kuopio added to its fire officer and firefighter curriculum SAMI-response equipment and PSR training. The idea for developing the PSR method and the SAMI- response equipment came from environmental organizations.
Thanks to Pekka Suomi, sales manager for Pohjois-Savon Palontorjunta Oy, and Mika Arffman, engineer for Pohjois-Savon Polytecnic, for their ideas related to developing and manufacturing the SAMI-response equipment.
References
1. Halmemies, S., K. Nenonen, and T. Tuhkanen, “Development of chemical response methods for fire and rescue services.” Geological Survey of Finland, Current Research 1999 – 2000. Edited by S. Autio. Special paper 31, 123 – 131, 2001.
2. Hollins, Leigh T, “MC-306/406 Transport tanker incidents,” Haz Mat Points to Ponder, Fire Engineering, Nov. 2000.
3. Halmemies, S., M, Vuorinen, A Mayer, and T. Tuhkanen, “Vacuum Based Recovery of Fresh Fuel Components in Laboratory Scale Column Experiments,” Ground Water Monitoring and Remediation, submitted, 2002.
4. Halmemies, S., S. Grondahl, K. Nenonen, and T. Tuhkanen, “Estimation of the time periods and processes for penetration for selected spilled oils and fuels in different soils in the laboratory,” Spill Science & Technology Bulletin, submitted 2002.
5. Halmemies, S., S. Grondahl, M. Arffman, K. Nenonen, and T. Tuhkanen, “Power Slurping Based Response Equipment for Acute Recovery of Fuel Spills from Soil.” Journal of Hazardous Materials, submitted, 2002.
6. Räddningsverket 1999. Utveckling av kunskaperna om sanerings- och återställningsarbete. Risk- och miljöavdelningen. Karlstad, Sverige. Swedish.
7. Savon Sanomat, Finnish magazine, March 13, 2001.
8. Erkki Nieminen, Stromsdal Ltd., personal communication, Apr. 17, 2002.
Source: “EPA 1993. Decision-Support Software for Soil Vapor Extraction Technology Application: HyperVentilate,” Cincinnati, OH: Office of Research and Development. EPA/600/R-93/028.
SAKARI HALMEMIES, Lic. Eng., has worked for 10 years as a head instructor in hazardous materials at The Emergency Services College in Finland. This article is a part of his dissertation on developing a new environmentally friendly vacuum extraction-based response method and equipment for use by emergency services for accidental fuel spills on the ground.
YRJÖ MÖTTÖNEN is CEO of Pohjois-Savon Palontorjunta Oy, a Finnish company that sells equipment to fire departments and other safety agencies. The company has manufactured the SAMI-response equipment, among other products.
TUULA TUHKANEN, Ph.D., is a professor of environmental engineering and biotechnology at the Tampere University of Technology in Finland. Previously, she had worked in the environmental department of Kuopio University. Her dissertation concerned purification of wastewaters with the aid of new advanced technologies. She is currently focusing on risk assessment associated with water and land contamination.
