The extent of water and sewer line breaks in the past couple of years might have more to do with aging infrastructure and a high water table than after-effects of the 2011 flood, according to Minot's public works director.
Dan Jonasson said the one lingering issue from the flood relates to problems with water quality because usage is low in areas where buyouts have occurred or people haven't returned to their homes yet. The city continues to flush water lines to address the problems.
In some instances, the city is experiencing broken water or sewage pipelines because groundwater levels since the flood are higher than they have been in the past. A wet cycle has been affecting the entire region.
Workers confer on a city water line break at Fourth Street and Second Avenue Southwest in Minot Monday. Strata Construction is pumping water from the trench, dug after the break was discovered Thursday.
Last year, the city dug up a sewer line on 16th Street in west Minot after it collapsed due to soft, moisture-laden soil.
"It's essentially like quicksand under there," Jonasson said.
The city last week was investigating the cause and exact location of a water line break at Fourth Street and Sixth Avenue Southwest, which closed the intersection while repairs were made. The pipeline broke near a spot where a 6-inch pipe comes off the 18-inch main to serve I. Keating Furniture World.
Jonasson said water-line breaks often are due to age of the line and to frost that leads to ground pressure on the line. The line at Fourth Street and Sixth Avenue is older cast iron pipe. Newer PVC pipe is more flexible and less prone to breakage when ground conditions shift.
The city has about 300 miles of water lines. Fifty percent is older cast iron, Jonasson estimated.
The cast iron produced before World War II has held up. Jonasson said the city has dug up pipe in places and found it still looks like new. Cast iron produced after the war hasn't endured as well.
"It's a lot more susceptible to soils," Jonasson said. "Soil will eat it away inside and out."
The city increased its annual budget for a watermain replacement from $400,000 to $700,000. However, Jonasson noted, "Materials are getting more expensive so I am not sure if we are gaining a lot of length of pipe that we are replacing."
A project to update the downtown infrastructure will enable the city to replace the cast iron water pipes and clay tile sewer system, heading off potential future problems. Both the water and sewer lines downtown are about 100 years old.