INTRODUCTION
On December 7, 1998 and December 9, 1998, the Air Toxics Analytical Support Team (ATAST) team conducted an investigation relating to a spill of sodium hydrosulphite along Interstate 26 in Polk County, North Carolina. A tractor-trailer crashed and spilled sodium hydrosulphite on December 6, 1998. The ATAST team was initially notified of the spill but was not requested to assist with the situation. On December 7, 1998, Robert Griffin with the Regional Response Team #6 requested ATAST presence at the spill. ATAST members Mike Chapman, Lori Cherry, Betty Gatano, Jim Bowyer, Kevin Ours, and Jeff Hayward responded to this request. On December 9, 1998, Paul Muller, on behalf of Robin Proctor of the Asheville Regional Office, requested that the ATAST team monitor for sulfur dioxide during the neutralization of sodium hydrosulphite at the Polk County landfill. ATAST members Mike Chapman, Lori Cherry, and Betty Gatano returned to Polk County to carry out the requested monitoring.
REASON FOR INVESTIGATION
This ATAST investigation was in response to the spill of sodium hydrosulphite along Interstate 26. Sodium hydrosulphite is a white powdery material that ignites on contact with water. At the crash site, moisture in the air had reacted with the spilled sodium hydrosulphite creating a fire and causing the emission of sulfur dioxide to the atmosphere. An eight-mile stretch of the highway was closed and approximately 100 residents evacuated from the area due to the spill and subsequent fire. In the first phase of this investigation, the ATAST team was asked to determine ambient air levels of sulfur dioxide around the crash scene in anticipation of the north-bound lane of the highway being re-opened. After the sodium hydrosulphite was removed from the highway, it was taken to the Polk County landfill to be neutralized. Batches of sodium hydrosulphite were to be introduced into a tank containing caustic water to neutralize the chemical. Since the neutralization process was experimental and had never been carried out on such a large scale, ATAST was requested to monitor sulfur dioxide levels at the landfill during the neutralization process.
INVESTIGATION METHODS
Interstate 26 in Polk County
On December 7, 1998 at 13:30, Robert Griffin with the Regional Response Team #6 requested ATAST presence at the spill of sodium hydrosulphite. The ATAST team of Mr. Chapman, Ms. Cherry, and Ms. Gatano arrived on scene at approximately 17:30 on December 7, 1998. After notifying the incident commander that the ATAST team had arrived, the team members established power with the generator and set up the response equipment. At the time of ATAST arrival, several containers of sodium hydrosulphite remained in the south-bound lane of Interstate 26, and one of these containers was still smoldering. ATAST members made preparations to enter the area around the smoldering container and sample for sulfur dioxide in the air. Lamotte pumps were calibrated and prepared for sulfur dioxide sampling. ATAST members then suited up in Tyvek suites and supplied air respirators and entered the area immediately around the spill at 18:25. The air sampler was set up approximately 10 yards downwind (south) of the smoldering container. Dräger tube readings were also made for flammable and toxic impurities (i.e., the polytest Dräger tube), sulfur dioxide, acid gases, and amine gases. The ATAST members remained in the area for approximately 30 minutes until the Lamotte sample was completed. After the sample was returned to the emergency response vehicle, the analysis of the Lamotte sample was completed.
At approximately 19:30, an ATAST backup team of Mr. Bowyer, Mr. Ours, and Mr. Hayward arrived on scene. At that time, ATAST members decided to take additional samples from the area to determine if the situation had changed. ATAST members then suited up in Tyvek suites and supplied air respirators and entered the immediately around the spill at 20:44. Two Lamotte air samplers for sulfur dioxide were set up approximately 10 yards and 250 yards downwind (south) of the smoldering container. The ATAST members remained in the area for approximately 40 minutes until both Lamotte samples were completed. After the results of the second sampling set were analyzed, the ATAST team determined that the situation was stable. ATAST departed the area at approximately 22:30. Polk County Landfill
The ATAST team of Mr. Chapman, Ms. Cherry, and Ms. Gatano arrived at the landfill at approximately 10:45 on December 9, 1998. The sodium hydrosulphite containers had been placed in a clear area in the landfill away from trees and debris that could catch fire. At the time of ATAST arrival, containers of sodium hydrosulphite were being broken open in preparation for the neutralization process. A plume of sulfur dioxide was emitted from the containers as they were opened. Concerns over the plume prompted ATAST members to take a Dräger tube reading for sulfur dioxide. The plume subsided when the containers were finished being opened. The team members then established power with the generator and set up the response equipment.
Throughout the day, the clean-up contractors were constructing a reaction vessel for the neutralization process. The reaction vessel consisted of a tank containing caustic water. The reaction of the sodium hydrosulphite with the caustic water was expected to generate steam and sulfur dioxide.
While they were waiting for the reaction vessel to be completed and the neutralization to get under way, ATAST decided to scout the area where the neutralization process would occur. ATAST members suited up in Tyvek suites and supplied air respirators and entered the neutralization area to take an initial Dräger tube sample. The Lamotte pumps were calibrated and prepared for sulfur dioxide sampling for a more detailed analysis. ATAST members returned to the neutralization area at 15:10. At approximately 16:00, the clean-up contractors started the neutralization process. Three Lamotte air samplers configured to sample for sulfur dioxide were set up 20 feet east, 35 feet north, and 50 feet west of the reaction vessel. Samples were taken in the neutralization area for approximately 30 minutes, until the first experimental batch was neutralized. After the samples were returned to the emergency response vehicle, the analysis of the Lamotte samples was completed. Once the values were reported to Ms. Proctor, the ATAST team departed the landfill at approximately 17:30.
INVESTIGATION RESULTS
Interstate 26 in Polk County
Dräger tube samples and Lamotte sampling were conducted while the ATAST team was onsite at the crash scene. The results for the sampling are given in the following tables.
| Dräger Tube Results for Crash Scene in Polk County on December 7, 1998 |
| Dräger Test |
Results |
| Sulfur dioxide |
1-2 ppm concentration |
| Acid gases |
Positive reaction |
| Amine gases |
No response |
| Poly test |
No response |
Lamotte Kit Sampling Results for Crash Scene in Polk County
on December 7, 1998 |
| Sample |
Time |
Location |
Concentration |
| 1 |
18:32 - 19:02 |
Approximately 10 yards downwind of smoldering container of sodium hydrosulphite |
0.44 ppm or 440 ppb |
| 2 |
20:49 - 21:19 |
Approximately 10 yards downwind of smoldering container of sodium hydrosulphite |
Non-detect |
| 3 |
20:54 - 21:24 |
Approximately 250 yards downwind of smoldering container |
Non-detect |
Polk County Landfill
Dräger tube samples and Lamotte sampling were conducted while the ATAST team was at the Polk County landfill. The results for the sampling are given in the following tables.
| Dräger Tube Results for Polk County Landfill on December 9, 1998 |
| Dräger Test |
Location |
Results |
| Sulfur dioxide |
Near guard house at the landfill |
Non-detect |
| Sulfur dioxide |
In plume emitting from broken container of sodium hydrosulphite |
2.5 ppm or 2,500 ppb |
| Lamotte Kit Sampling Results for Polk County Landfill on December 9, 1998 |
| Sample |
Time |
Location |
Concentration |
| 1 |
16:03 - 16:33 |
Approximately 20 feet east of reaction vessel |
Non-detect |
| 2 |
16:03 - 16:33 |
Approximately 35 feet north of reaction vessel |
10 ppb |
| 3 |
16:03 - 16:33 |
Approximately 50 feet west of reaction vessel |
<430 ppb |
CONCLUSION
The goal of this ATAST investigation was to determine sulfur dioxide levels at the scene of the sodium hydrosulphite spill and at the landfill during neutralization. The goal was accomplished using the Lamotte air samplers for sulfur dioxide. To put the results of the Lamotte sampling into perspective, one can consider the ERPG-1 level and the ambient air quality standard for sulfur dioxide. The ERPG-1 level is defined as the maximum airborne concentration below which nearly all persons exposed for up to one hour will experience only mild transient adverse health effects or will not detect a clearly defined objectionable odor. The ERPG-1 level for sulfur dioxide is 300 ppb (0.3 ppm). Maximum levels measured with the Lamotte samplers at both the spill area and the landfill were only slightly higher than the ERPG-1 level for sulfur dioxide. Thus, the results of the ATAST investigation indicated that the residents around the spill area and the landfill were not in danger from sulfur dioxide emissions. An additional comparison can be made against the ambient air quality standard for sulfur dioxide in North Carolina. The three-hour standard for sulfur dioxide is 0.5 ppm. The concentration of sulfur dioxide measured at the sodium hydrosulphite spill was 0.44 ppm, and the concentration at the landfill was less than 0.430 ppm. Both concentrations are below the ambient air quality standard for sulfur dioxide.
ATAST Team Members
- Lori Cherry, Supervisor, Toxic Protection Branch
- Michael Chapman, Chemical Accident and Prevention Coordinator
- Kevin Ours, Environmental Engineer II
- Betty Gatano, Environmental Engineer I
- Jeff Hayward, Industrial Hygiene Consultant
- Jim Bowyer, Chemist III
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