Advanced Specialty Chemicals Co., LC (AdSpec) - Executive Summary |
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Advanced Specialty Chemicals Co., LC (AdSpec) is involved in the purification, repackaging and delivery of ethyl mercaptan (ethanethiol: CAS# 75-08-1). Ethyl mercaptan is used as an odorant in propane gas to enable leaks of propane gas to be detected by smell. Ethyl Mercaptan can be detected (human nose) at less than 1 part-per-billion (ppb) in air. It is an obnoxious, unpleasant odor. One (1) pound of ethyl mercaptan is sufficient to odorize 10,000 gallons (42,000 pounds) of propane. Ethyl mercaptan has a TLV (8-hour exposure) of 0.5 ppm (500 ppb; 1.3 mg/m3) and an IDLH of 500 ppm. Ethyl mercaptan is the only CAAA 112r regulated material on the AdSpec site. For the purposes of this regulation, EPA addresses ethyl mercaptan as a "flammable." Ethyl mercaptan is received in 6350-gallon ISO containers (tanks), containing a net load of 38000 - 42000 pounds. At the Blackwell site, ethyl mercaptan is offloaded from the ISO tanks into over-the-road tank trailers (capacities: 37,0 00 - 43,000 pounds) for delivery to propane distributors. Some ethyl mercaptan is transferred from the trailers into smaller containers (57-gallon or 120-gallon) for delivery to specific customers. All transfers are monitored by a trained technician. AdSpec's "Worst Case Scenario" addresses the catastrophic rupture of the 43,000 pound delivery trailer (the largest single container of ethyl mercaptan on the Blackwell site). Using EPA's "RMPComp" program, the furthest extent of a 1-psi overpressure caused by an unconfined vapor-cloud explosion is 0.2 miles radius from the center of the vapor cloud. There is only one residence within this radius. AdSpec's "Alternate Case Scenario" addresses the more plausible situation where a fitting, flange, or valve develops a small leak and looses liquid material at a rate of 4.3 pounds per hour. For planning purposes, AdSpec has this leak continue for 10 hours (43 pounds total released). In reality, it is unlikely that a release would continu e for more than the 2-3 hours it could take to detect, respond to, and abate the leak. "RMPComp" shows the 43-pound leak (total leak) producing a 1-psi overpressure through unconfined vapor-cloud explosion extending out less than 0.1 miles radius (approximately 275 feet) from the center of the vapor cloud. This 1-psi overpressure does not impact any structures or receptors off the AdSpec site. Although EPA addresses ethyl mercaptan only as a flammable material, AdSpec has looked at what offsite consequences might arise from its Alternate Case, other than those of overpressure from vapor-cloud explosion. Using the ALOHA dispersion model, a release of 43 pounds of material over a one-hour duration (Note that for the Alternate Case vapor-cloud explosion, AdSpec used 43 pounds over ten hours; however, the ALOHA model will not accept a 10-hours leak time.) would extend a zone of concentration above the IDLH for approximately 14 feet radius from the point of discharge and would extend a zone of concentration above the TLV for approximately 1500 feet radius from the point of discharge. Ethyl Mercaptan's very low odor threshold makes it unlikely that any leak would go undetected for any appreciable amount of time. Using an odor detection level of 5 ppb (fives times the accepted value), it is estimated (using the ALOHA dispersion model) that a leak of only 5 gallons of liquid would be detectable by smell up to five and one-half (5=) miles away from the leak site. A leak of 8 ounces per day is easily detectable within 150 feet of the leak. Since its founding in 1995, AdSpec has not had any situation at its site that has caused an evacuation (or "sheltering") of its neighbors. AdSpec desires to continue its good relations with its neighboring businesses and with the city of Blackwell. Therefore, onsite equipment is monitored for leaks (odor) on a daily basis. Any trace of odor is tracked down and stopped. AdSpec has an Emergency Action Plan in place that includes joint training with emergency responders from the City of Blackwell. AdSpec relies on municipal emergency response personnel for off-hours first response and for response to situations that have grown out of AdSpec's control. AdSpec has provided the local hospital emergency room with information about the materials it has on site and has had a local doctor visit the site to gain some familiarity with AdSpec's operations. AdSpec's Standard Operating Procedures include notifying neighboring establishments, the Blackwell Fire Department, and the ARKLA Gas Company whenever a situation arises that might involve the odor of ethyl mercaptan migrating off of AdSpec's site. AdSpec has enterred a service agrement with an Oklahoma HazMat Incident Response contractor. The primary advantages seen are the ability to pre-train the contractor's responders and to make an additional resource available to the Blackwell emergency responders for off-hours situations. In addition to being an OSHA PSM -regulated facility, AdSpec operates under an ISO 9001 (Quality Management) program. This requires documented operating procedures as well as maintenance of product quality. AdSpec continues to work with its suppliers to improve the condition of the containers of ethyl mercaptan being shipped into the United States. Significant improvements have been made in the selection of gasketting materials, the use and installation of blind flanges, and the maintainence of adequate ullage at filling. |