By JILL SCHRAMM
With downtown Minot as a backdrop, work continues on a dike running east from the Broadway Bridge in this June 22, 2011, photograph. The dike was originally constructed to defend against a flow of 10,000 cubic feet per second of water, then raised substantially as the flood forecast increased. The issue of how high to build a possible permanent levy is scheduled to be discussed during meetings of Minot City Council committees this week.
Contractors worked furiously to raise the dike that protected a portion of northwest Minot and prevented Broadway from flooding in late June 2011. The dike held against a record flow of nearly 30,000 cubic feet per second.
Scaling back a $543 million flood-control project through Minot would do little to save money, according to an engineering study completed for the City of Minot.
The Minot City Council had requested last April that Barr Engineering calculate the cost of reducing the project's design elevation from 27,400 cubic feet of river flow the 2011 record to 10,000 cfs, 15,000 cfs and 20,000 cfs.
The biggest savings in any scenario amounted to only $30.7 million, or less than 6 percent of the $543 million, and involved reducing protection to 10,000 cfs.
The Minot City Council's Finance and Improvements and Public Works and Safety committees will hear from the engineering team this week during regularly scheduled meetings. Meetings are open to the public. The finance committee meets Tuesday and the public works committee meets Wednesday, both at 4:15 p.m. in City Hall.
"This isn't the result that we were hoping for as a city, but it does provide us with a deeper understanding of the realities of building a large-scale flood protection plan," city council member Dave Lehner said in a prepared statement. "Since only a portion of the $543 million price tag is directly tied into levees and flood walls, only a relatively minor amount of cost savings can be reached by dropping the height of these protective features by three to seven feet."
The study assumed the project footprint and property acquisitions would not change because the city wants to maintain the ability to eventually build out to 27,400 cfs. The city also wants to be able to raise levees to the 27,400 cfs protection level in an emergency.
The assessment looked at the savings made possible by dropping the height of earthen levees and flood walls. Engineers evaluated multiple scenarios, including constructing permanent levees to lower heights but with space on top to add more material in an emergency.
According to the assessment, the $66 million in costs related to planning, engineering, design and construction management and the $133 million for levees, flood walls and transportation closures represent 37 percent of the cost of the flood plan within city limits. These are the costs that would be affected by a change in levee height.
The remaining 63 percent of costs would not be directly affected by lowering the design elevations. These costs include buying land and easements, upgrading pumping stations, reconstructing roads and bridges and making channel improvements.
The enhanced flood protection plan calls for 8.8 miles of levees and 2.2 miles of flood walls in the city of Minot, along with 20 transportation closure structures.
Engineers noted that reducing protection to 10,000 cfs leaves a number of properties without permanent flood protection. Should another flood threaten the city, there would need to be significant effort, cost and time invested in emergency efforts to raise the levees, the report stated.
Engineers listed flood fighting implications for a scaled-down project as:
- Fully modifying flood walls, closure structures, pump stations and other structures might not be possible in the time frame of a flood fight.
- Suitable material to raise more than eight miles of levees might be difficult to find and deliver to needed locations on short notice.
- During a dry cycle, the public perception of flood risk decreases. As time passes, there could be a shift in focus from improving the flood protection system to other needs, putting the city at risk should another flood threaten.
The Federal Emergency Management Agency has classified the 2011 Souris River flood as a 260-year event. The probability of another 260-year event within the the 30-year time frame of the average home mortgage is about 11 percent. There is a 26 percent chance of a 5,000 cfs event Minot's current protection level in the next 30 years.
The State Water Commission is funding much of the design work on a flood protection plan for the Souris River Valley. A preliminary alignment for the valley between Burlington and Velva to protect against another 2011-scale event estimates construction will cost $820 million.