Photo courtesy of Enbridge
Enbridge is using trailer-mounted flare stacks to burn off vapors from a natural gas liquid spill on Aug. 25.
Canadian energy firm Enbridge has temporarily halted construction of its $1-billion Line 5 pipeline reroute project in northern Wisconsin after the state’s Dept. of Natural Resources requested the shutdown while a cleanup and resolution are sought following an Aug. 25 accident that caused a natural gas liquids spill near Saxon, Wis.
“The agency is deeply concerned about this spill and immensely frustrated by other recent noncompliance events and has several outstanding questions of Enbridge and would appreciate written responses as expeditiously as possible,” Wisconsin DNR Secretary Karen Hyun
wrote in an Aug. 27 letter.
“The department requests that you halt work on the pipeline re-routing project until this event on the existing pipeline is sufficiently resolved and Enbridge has demonstrated that measures are in place to prevent future spill events related to all pipeline work.” she added.
The construction pause was expected to start on Aug. 31 and last two days.
The incident occurred when an unoccupied, parked, third-party-owned semi-truck delivering equipment rolled into an excavation site on the east side of the pipeline, striking a bypass valve being added by Enbridge to connect the existing pipeline to a new pipeline under construction.
Enbridge is constructing the 41-mile-long pipeline to avoid tribal lands, while still operating its disputed 12-mile pipeline segment on reservation land owned by the Bad River Band of Lake Superior Chippewa, which is the subject of legal proceedings seeking its removal. The pipeline on which the accident occurred is part of a network that brings oil and gas to the U.S. from Canada and is expected to be non-operational until Sept. 5, Enbridge said.
In an Aug. 30 update, Enbridge said 150 people are helping with the cleanup, and crews are using trailer-mounted flare stacks, which can safely burn excess hydrocarbon vapors in a controlled manner, to remove remaining vapors from the impact area.
Natural gas liquids, mainly propane and butane, are transported by pipeline. When exposed to normal outdoor conditions, they rapidly vaporize into gases. As of Aug. 29, about 2,000 barrels of natural gas liquids remain in the excavation area. Enbridge noted that about 31,000 barrels of primarily propane and butane have vaporized and dispersed into the atmosphere.
Among several requests, DNR is asking Enbridge to provide its plans for controlling and mitigating the vapor release; the depth to groundwater; information on soil types at the spill location; when Enbridge anticipates providing a plan for installing groundwater monitoring wells and for modeling; whether air dispersion modeling is being performed; what materials were involved in the accident and being carried; and whether Enbridge has involved the U.S. Environmental Protection Agency.
NGLs are hydrocarbons—including ethane, propane, butane, isobutane, and natural gasoline—that are separated from natural gas during processing. They are used as fuels and as feedstocks for producing plastics, medical supplies, electronics, clothing, fertilizers and other products.
Annemarie Mannion is editor of ENR Midwest, which covers 11 states. She joined ENR in 2022 and reports from Chicago.
