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Minneapolis water-main repair filled with challenges

A 13-foot-long chuck of damaged cast-iron pipe, 3 feet in diameter and more than an inch thick, is stored securely under Minneapolis Department of Public Works control, following last week’s construction accident that spilled 14 million gallons of water onto downtown streets.

“It was one of the largest breaks we have seen in many, many years,” City Engineer Steve Kotke told members of the Transportation and Public Works Committee Tuesday.

 “A large main like that, you can’t just shut it down,” he explained, saying there is so much pressure in a pipe that size that shutting it down quickly produces new damage.

Instead, the flow in the main had to be “pinched off,” which left water flowing for about an hour and a half.

The water main was ruptured Thursday afternoon by a construction worker attempting to connect a sewer for a downtown development at Hennepin Avenue and Second Street North.

Downtown Minneapolis and the area south of downtown lost water pressure until Thursday evening. A three-block area with six buildings had no water until Sunday evening.

One of the first problems encountered was removing a large piece of construction equipment from the hole where the main was damaged.  That was accomplished when the contractor brought in a crane.  Gas mains and fiber optic lines also had to be secured.

On Saturday, city crews had hoped to hook up a new section of pipe but discovered that the old pipe, from the 1890s, was in good condition but was no longer round -- and therefore not an exact match for the new pipe.  That delayed completion of the repairs because it required custom milling on the two sleeves that connect the old line with the new section.

Meanwhile, early Sunday morning, crews installed temporary pipes to restore water service to the three-block area.

The old cast-iron main and the new section were successfully joined Monday morning and are currently being disinfected. The line is expected to be in service sometime Wednesday.

The entire cost of the damage will not be known for some time. The cost of the 14 million gallons is estimated at $65,000, but that is only the beginning.

City crews have been working around the clock and will not be turning in their time slips until later this week. Kotke said he expects to have an idea of the cost of labor and materials sometime next week.

Crews inspected Hennepin Avenue for cavities under the road surface before it was re-opened to some traffic and found that the “road held up pretty well,” Kotke said. He does not expect to see an increase in potholes along the flooded sections of the street.

“The crews, clearly, had miserable working conditions,” said Council Member Sandy Colvin Roy, noting that one of the main obligations of a city is to provide “clean drinking water and the ability to flush.”

“It has been a lesson in the importance of infrastructure,” said Council Member Elizabeth Glidden, who congratulated city working for an “amazing” job.

Adding to the damage total will be the vehicles in the Post Office garage that were submerged under water and additional damage to the Post Office basement.

Hennepin Avenue reopened for one lane of southbound traffic Tuesday morning but will need repairs before more lanes south can reopen. Northbound lanes reopened earlier.

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Comments (1)

Cost burden?

Ms Boros: The speed with which service was restored was amazing. City staff deserve kudos & I'm glad we don't live in the Grover Norquistian paradise of no government. But I was surprised not to find any answer in your story of the question that readers (especially Mpls readers) certainly have: who will pay? Surely Ryan is responsible to make the city whole for its damages and costs, and in turn can look to its contractor for indemnification, no? Or are Mpls residents again being set up to eat the costs?