Dangers of excavation work on display in deadly Sun Prairie blast

The aftermath of a gas explosion in downtown Sun Prairie is seen on Wednesday. The blast is illustrative of the dangers faced by contractors and excavators nearly every day on the job. (John Hart/Wisconsin State Journal via AP)

After severed gas lines led to both a deadly explosion in Sun Prairie and an evacuation in Fond du Lac this week, industry officials are saying now’s a perfect time to reflect on the dangers of reckless excavations.

It’s still unclear exactly what caused the blast that destroyed buildings, killed a firefighter and injured at least a dozen others in downtown Sun Prairie on Tuesday night. The Kansas-based fiber-optic installer Bear Communications has merely said that a subcontractor, which hasn’t yet been named publicly, was working for it at the site.

For industry officials, the incident was both shocking and illustrative of the dangers they are faced with nearly every day on the job.

“You don’t hear of this happening,” said Bob Bartel, executive director of the Wisconsin Underground Contractors Association. “My contractors, they are so aware of this issue from a total safety standpoint. You just don’t want anybody to get hurt. You’ve got to be careful. It’s a dangerous job.”

Before the explosion on Tuesday, Bear Communications’ contractor was working to expand Verizon Wireless’ internet service in downtown Sun Prairie, company officials said. Like Bear and Verizon, local officials have declined so far to identify the subcontractor that was at the site, although the Sun Prairie Police Department has acknowledged that a contractor ruptured a 4-inch natural gas line, causing the leak. The Sun Prairie Police, which are investigating the incident, did not return a message seeking information about the contractor by press time on Friday.

Sun Prairie wasn’t the only city in the state where a contractor hit a gas line this week.

On Wednesday morning, officials in Fond du Lac evacuated between 16 and 20 homes after a contractor hit a natural-gas line there. Crews from Alliance Energy shut off gas service for about 30 customers before allowing people to return to their homes that afternoon.

Bartel said it’s “very rare” for crews to sever two natural gas lines in one week. He said contractors, utility companies and local authorities take the threats posed by cut lines very seriously.

Bartel said it may be unusual for a leaking gas line to cause an explosion, but it’s not unheard of.

In 2008, crews working for the Luxemburg-based contractor Dorner were excavating a road to make way for new sewer lines in front of a church in Oconomowoc when they came upon a gas line that they thought was inactive. It wasn’t. When they tried to move the pipe, it ruptured. The resulting explosion destroyed the church, damaged nearby houses and injured seven people.

Anyone who digs — be it a road contractor or a homeowner with a shovel — is prohibited from beginning work without first calling the Wisconsin Diggers Hotline. The hotline relays the callers’ plans to local utility companies, which then go out and mark the locations of underground utility lines such as gas and electric lines.

“The risk of not calling is hitting an unknown buried utility line,” said Chad Krueger, a spokesman for the Diggers Hotline. “It could be a fiber optic cable, which is very expensive to replace, or it could be a natural gas line.”

But even with a thoroughly marked work site, risks remain, Bartel said. Marks may show an underground line’s position parallel to the ground, but they will seldom provide an indication of how deep it lies.

“It’s yet another reminder of the need to be safe and careful,” he said. “You’re dealing with an unknown.”