Construction complete on Grand Drive

Construction on the Grand Drive portion of the Bigfork Stormwater Project was completed Thursday with the installation of four Filterra units along the roadway.

Once the entire Grand Drive treatment system is flushed out, it will be ready to go online and begin treating stormwater. According to Alan Wendt of 48 North Civil Engineering Services, the system will likely go online sometime this week.

Each Filterra unit contains some sort of vegetation planted in a concrete box filled with a specially designed filter media mixture. The mixture — which pretreats stormwater by removing pollutants such as phosphorus, nitrogen, heavy metals, grease and oil — is a blend of mulch, soil aggregate, coarse sand and peat moss.

Excess water flows into an underdrain system at the bottom of the container, where it is discharged into the conveyance lines and carried to the main treatment system.

Two of the Grand Drive units were outfitted with Red Osier Dogwood shrubs, and single-stem Japanese lilac trees were placed in the other two units.

“Both of those plants really like nitrogen and phosphorous, and they wanted something at both ends that wouldn’t block the sidewalk or the view for people pulling out of the parking areas,” said Sue Hanson, who is the chair of the Bigfork Stormwater Advisory Committee. “They really thought this through.”

The next phase of the project will be the construction of the River Street section of the stormwater system.

For funding reasons, the design on that portion of the project has changed slightly from the engineers’ original proposal.

The modified design eliminates the Filterra units that were to be installed on both sides of Electric Avenue. Instead, a catch basin will be installed at the north end of the building that houses Electric Avenue Gifts and Riecke’s Bayside Gallery.

With the new design, the water collected in the River Street Drainage Basin will not be pretreated before it is sent to the main treatment system on Grand Drive. According to Hanson, skipping the pretreatment cycle is not a major concern, as the water will still be treated at the main unit before being released into the bay.

“The way the engineers described it to me is that we’re moving from the Cadillac version to the Chevy version, which is OK with me because a Chevy is still a pretty good car,” Hanson said.

As an added benefit, the elimination of the Filterras will save the three parking spots that would have been lost following the installation of the units on Electric Avenue.

Hanson said the project’s main funding agencies — the Department of Environmental Quality and the Department of Natural Resources and Conservation — must approve a shift in funding allocations before money can be used for the construction of a modified design.

If approved, the change would reduce the amount of the Rural Special Improvement District funding the committee is currently working toward, which would decrease the funding burden on taxpayers.