Stormwater project open to bids
The construction contract for the Bigfork Stormwater Project on Grand Drive is officially open for bidding following the Flathead County commissioner's approval of the final design engineering .
The goals of this portion of the project involve improving the conveyance of water in that corridor and improving water quality, engineers from 48 North Civil Engineering Services told the Bigfork Stormwater Advisory Committee at a meeting last week. This includes sections of Grand from the Bigfork schools down to Electric Avenue.
The construction contract would be for 80 days — 40 in the fall and 40 in the spring — and would begin Oct. 4, if everything goes according to plan in the bid process. Fall work would conclude Nov. 12 for the winter. During that time, construction would primarily take place on the portion of the road from Saddlehorn north on Grand. Construction would begin again April 4 to be done by May 13. 48 North President Brett Walcheck said he felt that the time period had enough buffer days if weather did set it off to still have all work completed by the end of May, prior to Bigfork's annual Whitewater Festival.
"The challenge is Mother Nature," Walcheck said.
Another potential delay in the construction may arise if there are boulders found under the pavement, as have been discovered in prior construction projects in that portion of the Village.
"We don't know what's below the pavement," Walcheck said. "It makes the project that much more challenging."
In an effort to address local business owners' concerns, engineers have tried to work specific requirements into the contract and project language including not allowing total lane closures, providing traffic control and putting up signs that give notice that businesses are open.
"We have really included a lot of measures to adapt to the business not being rerouted," Walcheck said.
Walcheck assured the committee and the few community members present that there would be access to the street so that businesses can continue their operations and so that emergency vehicles can get through.
The new system will be built for the conveyance of a 100-year event, which is comparable to getting 3.14 inches of rain in a 24-hour period, said Jim Williamson of 48 North. In terms of water quality, the system is built for a 10-year storm event, which is 1.19 inches of rain in a 24-hour period. Approximately 85 percent of rain events in Bigfork are typically this amount or less, he said.
"It's not economically feasible to treat 100 percent of runoff," Williamson said.
Portions of Grand have no existing pipes or inlets and those will be installed. Areas that do have existing pipe will have it replaced with bigger pipes. All of the work will be done in the county right-of-way, Williamson said. The existing system runs stormwater through the old pipes without treatment directly into the Bay. The new stormwater pipes most often will run parallel five feet from the sewer line. It's required to be 10 feet from the water line.
The pipes will lead to the filtration devices, both a Stormceptor and Jellyfish device, which will be installed in the lowest spot in the road above the public dock. Between the two, sediments as well as those pollutants that attach to sediments like phosphorus, oils and greases, will be removed. Four Filterra units will be installed along the way down Grand to remove biological pollutants that don't attach to sediment like nitrogen. The placement of these is targeted at "hot spot" areas like across from the bus parking at the school.
Flathead County grant writer Debbie Pierson said funding agencies for the project, the Montana Department of Environmental Quality and the Treasure State Endowment Program, have "given their blessing" to proceed with advertising for the contract. The official contracts still need to be received and are under legal review. TSEP has opened up the environmental assessment on the project for public comment through Sept. 3.