Dredging becomes primary direction for Lake Mitchell

In excess of $10 million for the two primary options, the costs of dredging Lake Mitchell and working to solve the city’s issues with water quality are better known following Monday’s Mitchell City Council meeting.

Officials from Fyra Engineering pointed toward dredging -- either mechanically or hydraulically -- as its top recommendation in front of a capacity crowd in the meeting room at Mitchell City Hall.

The mechanical dredging option is estimated to cost $10,590,480, which would involve pumping the water out of the lake, removing sediment with heavy equipment and conducting post-dredging applications to attempt to neutralize future phosphorus elements from settling in the lake bottom.

A hydraulic option - at a cost of $13,359,900 - would be similar to using a Shop-Vac, Fyra’s Mike Sotek said, and would create a slurry-like material with the sediment to be hauled out and recycled to bring clean water back to the lake.

Either way, it’s recommended that 1 million dry cubic yards - called “a conservative figure” on the high side by officials - of soft sediment is to be removed from the lake and taken to another site to try to address the issues. No action was taken Monday but most of the final findings and recommendations were known. The city’s new mayor Bob Everson and council will likely take on the issue next month.

Sotek said the research made it clear that dredging would be the most likely way to solve some of the lake’s issues.

“If the city were to apply alum, it would spend millions to have temporary relief and very limited success,” said Greg Kipp, of Rapid City-based Verax Environmental Consulting.

Sotek added that a whole lake application without any dredging to apply materials and let it settle would be astronomically expensive, in excess of $18 million. The same could be said for using alum-absorbing materials and shipping them in to cap the sediment, which was projected to cost more than $20 million.

Each of dredging option has pros and cons, Sotek said. The mechanical option is more effective and is cheaper, but there are risks with potentially destabilizing the shoreline, because the current water provides pressure on the shoreline to keep it in place. The hydraulic option can basically be done in any season and doesn’t impact the shoreline as much, but also might not be as effective and costs more.

The containment site for the dredged material is also part of the equation. Sotek said taking 1 million cubic yards and spreading it over 40 acres would equate to being about 15 1/2-feet tall, but the hydraulic project would require two to three times as much space because of the water and slurry involved.  

Kipp said the research group visited the site and took corings from the lake bottom in February and mapped the lake at the end of May. That mapping estimated there are about 1,920,000 cubic yards of sediment in the lake, with about 1,310,000 of that being unconsolidated, or loose, materials. When that sediment dries out, it loses about half its value.

“We learned a lot about this lake through this coring effort,” Kipp said.

The councilors’ questions primarily were based around the logistics of the dredging, including suitable sites for the material, trucking and understanding the costs. This would be the first dredging project in the state for Fyra, and Sotek said not many lakes in the state have taken on dredging projects. He said the dredging could be completed in six months’ time.

Sotek said the next steps would include the city assembling a funding package of local and outside funds that can be used for the load control project. Once a dredging project has been decided upon, the final design and permitting stage can begin to allow bidding. The city would also need to secure a location for dredging to be placed and additional sampling might take place in spring 2019 for future external loading project information.

Also proposed was a drawdown conduit, which could be used as a tool to bring the lake levels down in the future. That cost was estimated at $654,800, which would use a 42-inch pipe to manage water. An annual alum application was also among the possible recommendations, estimated to cost $425,000 each year, which Sotek noted could be important to developing a usable lake.

Public concerns Animal control and parking in residential areas were two areas that got considerable attention early in the meeting Monday.

Rosemary Menning told the council during a public input portion of the meeting that she’s been attacked twice in the last few months by dogs that were not on a leash. She said she’s frustrated both with the attacks and the lack of education for dog owners not using leashes.

“Once you become a victim, and bit by an 80-pound dog, you understand the kind of threat these dogs can be, especially for kids,” she said, adding she believes there are 12 unleashed dogs in her neighborhood.

Mitchell Department of Public Safety Chief Lyndon Overweg said the city is currently in the process of bringing a new animal control officer on board. He said the city has captured more than 300 animals in each of the last two years and fines owners $125 or more after multiple offenses. Overweg noted that a policy in which dog owners must remove their animals from the city after multiple attacks would have to be a council decision.

“We do take it serious,” he said. “And I know for those who have already been attacked it’s not enough. To go through it twice in a matter of weeks is really difficult … (The fines), that’s the most we can do.”

During the city’s traffic commission meeting, a motion for a no parking zone at 1529 Country Drive was tabled. Susan Galpin made the request due to a large truck blocking her mailboxes, preventing mail from being delivered. The truck’s owner, Casey Paul, said the issue would be rectified going forward, and commission officials said it would be re-evaluated next month to evaluate the progress.

Other business

• In the public health and safety meeting, the council approved a noise permit for Jeff and Cindy Krall on July 6 at 1 N. Harmon Dr. for an outdoor band.
• During the Traffic Commission meeting, approved the Mitchell Area Development Corp.’s request to reduce the reserved parking signage to three spaces and change the time limit from 30 minutes to an hour.  
• Approved the renewal of Eight West LLC’s malt beverage license, doing business as Super 8 Mitchell.
• Approved the following special event malt beverage licenses for the Palace City Lions Club at the Horseman’s Sports Arena on two separate occasions: July 19-22 for the Corn Palace Stampede Rodeo and the Mustang Seeds Xtreme Bulls event Aug. 22.
• Approved the application from the Corn Palace Shrine Club for an on-off sale malt beverage license at the Masonic Temple, 112 E. Fifth Ave.  
• Meeting as the Board of Adjustment, scheduled a hearing for July 2 regarding Laura Picek’s application for a conditional use permit to operate a family residential child care center at her residence at 1033 E. First Ave.
• Approved resolutions R2018-31 and R2018-32, which authorizes the application for financial assistance, allowing the city to apply for SRF loans for Sanborn Boulevard Phase II and Phase III projects. Resolution 2018-31 is for $6,842,000 to fund storm water and sanitary sewer improvements, while Resolution 2018-32 is for $821,000 in drinking water improvements.
• Discussed the city’s northwest bike paths at West 23rd Avenue and North Ohlman Street and snow removal. While no decisions were made, the council supported plans to draft an ordinance to continue clearing snow in areas where they have previously, even if there’s not a specific easement.  
• Recited Pledge of Allegiance, roll call of councilors, heard public health and safety and traffic committee reports.

Consent agenda Approved the following actions as part of the council’s consent agenda.

• Minutes for the June 4 meeting, the June 11 special meeting and work session.
• May monthly reports for sales tax collections, finance department, building permits, police/fire/EMS reports, transit ridership, airport reports and water report.
• A raffle permit for the Palace City Pedalers to hold a raffle on Aug. 18 valued at $400; and the Mitchell Friends of NRA to hold raffle in the future valued at $250.  
• An application for transportation grant funds as a subgrantee under the state’s Dept. of Transportation surface transportation funds.
• Declared the city’s department of public safety’s key card system as surplus, with the intent to sell via online auction.
• Approved taxicab license for Russell Edward Hanson doing business as Lyft driver.
• Approved gas and fuel quotes, pay estimates, bills, payroll, salary adjustments and new employee hires and authorize payment of recurring expenses.