Seminole Pipeline Co. should not be allowed to expand and reopen a Southeast Texas natural gas liquid (NGL) storage site where three persons died in a 1992 explosion.
So recommended Texas Railroad Commission hearings examiners studying Seminole's application to increase to 1 million bbl the capacity of its NGL underground storage site near Brenham, Tex., about 40 miles northwest of Houston. TRC examiners said Seminole failed to prove the facility would be operated in a way that would protect fresh water, public welfare, and physical property.
"Accordingly, the examiner, recommend that Seminole's application to expand the capacity of the facility be denied and the permit granted Aug. 10, 1981, (to operate the NGL storage site) be revoked," the hearings panel's proposal for decision said.
The Brenham salt dome cavern is one of three storage sites on a 14 in., 1,300 mile products pipeline system in Texas owned by Seminole, which in turn is owned 80% by Mapco Natural Gas Liquids Inc. (Mapco NGL).
Mapco NGL was formed in January 1993 as a unit of Mapco Inc., Tulsa, in a merger of Mapco's pipeline operating subsidiaries. At the time of the accident, Mapco Transportation Inc. held controlling interest in Seminole. Mapco NGL also owns Mid-America Pipeline Co., which operates a remote dispatching center for all Mapco pipelines, including the Seminole system.
Under TRC rules, parties to the case have 15 days to file comments with TRC examiners, followed by a 10 day period to file rebuttals to others' comments. Based on those filings, TRC examiners may change their recommendations before placing the case on a TRC open meeting agenda for a final decision by the three TRC commissioners.
NTSB FINDINGS
The Brenham blast killed a young boy and two adults, injured 21 persons, and caused an estimated $9 million in damage to property within a 3 mile radius.
TRC examiners relied mostly on testimony presented by Seminole and by opponents to expanding and reopening the Brenham salt dome. However, the panel also considered the findings of a November 1993 National Transportation Safety Board report on the Apr. 7, 1992, accident.
The NTSB report said seismographs at three Texas universities within 75 miles of the scene recorded surface tremors ranging from 3.5-4 on the Richter scale. Windows were rattled of homes more than 130 miles away.
NTSB investigators found that the explosion occurred when highly volatile liquids (HVLs) were accidently released after the Brenham facility was overfilled.
Mapco was not aware of the volume of product in storage at the site because its management procedures lacked oversight adequate to confirm employee measurements and the ability to balance cavern receipts against withdrawals. In addition, employee measurement procedures did not adequately take into account specific gravity variation of NGLs in storage, NTSB said.
Following the accident, Mapco, with TRC supervision from July 8 Aug. 16, 1992, emptied the Brenham cavern, removing 338,995 bbl of NGL. That volume was about 50,600 bbl more than the volume Mapco reckoned to be in storage.
NTSB's accident investigation found that from july 13, 1991, the last time before the accident Mapco had emptied the Brenham cavern, until the explosion, Mapco's on-scene employees made almost 700 errors calculating the volumes of NGL entering and leaving the facility. Mapco auditors refiguring NGL volumes to correct the mistakes reduced the volume of NGLs injected into the cavern by 19,196 bbl and the volume withdrawn by 50,872 bbl.
NTSB said other factors - including lack of several failsafe features on the cavern's shutdown system, inadequate emergency response training and procedures, and poor communication among Mapco employees responding to the emergency-contributed to the accident.
