Kellogg stormwater projects explained

KELLOGG — Half of a million dollars has been allocated to the city of Kellogg for a stormwater system improvement project thanks to a governor-led initiative.

Late last year, Idaho Gov. Brad Little announced $2 million would be available for projects under his Leading Idaho initiative (formerly known as Building Idaho’s Future) — due to record years of budget surplus, Leading Idaho is Little’s plan to give back the surplus to Idahoans in the form of tax cuts as well as using the available money for key investments in several different areas including transportation, public health, broadband, agriculture, election security and water.

Under the purview of the city, Kellogg’s project will see several stormwater system retrofits that will be designed with the goal of reducing harmful sediments and nutrient loads in the city’s stormwater throughout the city as it drains into the South Fork Coeur d’Alene River.

This project addresses a growing concern from the Idaho Department of Environmental Quality (DEQ), which is likely one of the main reasons for its funding.

Keeping stormwater as clean and sediment-free as possible is tantamount to keeping the river clean as it makes its way to Lake Coeur d’Alene.

According to DEQ limnologist Craig Cooper (the study of the biological, chemical, and physical features of lakes and other bodies of freshwater), the health and cleanliness of Kellogg’s stormwater has a direct effect on the health of the lake.

It’s a balance of maintaining the correct levels of oxygen, phosphorus and algae, and when any one of these things gets out of balance it can disrupt the entire lake ecosystem.

“The science of the lake shows that the phosphorus levels are rising,” Cooper told the News-Press. “This is cause for concern. Kellogg’s stormwater projects were selected because stormwater is one of the major sources of nutrients to the lake. $515,000 was awarded by the state to complete these projects in an effort to reduce that stormwater load to the Coeur d’Alene River and reduce the amount of phosphorus going into the river.”

DEQ estimates that approximately 180 tons of phosphorus enter the lake on average each year.

Outside from this one particular benefit, modernizing stormwater systems has other benefits as well.

“This will help with heavy metals runoffs into the river as well as oils from the streets,” Cooper said. “Most of it happens when you have a big rain on snow event and that water begins rushing down the streets into the gutters and picks up all of that stuff that’s in its path as it heads into the existing systems and then into the river. If we can clean up the stormwater, this can help clean up the river and in turn help clean up the lake.”

The three project areas are the Bunker Creek and Hill Street Outfalls, and the North Kellogg Outfall.

Kellogg city officials explained the vast nature of the projects in their project statement of work application.

“Stormwater treatment at the outfall to Bunker Creek improves the overall quality of stormwater that is discharged to Bunker Creek from the city of Kellogg by constructing a large bioswale between the city’s outfall and the creek. This area currently receives almost 30% of the city’s overall stormwater.”

Bioswales are storm water runoff conveyance systems that provide an alternative to storm sewers. They can absorb low flows or carry runoff from heavy rains to storm sewer inlets or directly to surface waters.

“This project has two parts. Part 1 is the bioswale for treatment. A forebay would be installed at the pipe outfall creating a sediment trap and maintenance access point. A portion of the existing pipeline may be removed to accommodate the forebay and improve the hydraulics of the system to maximize treatment. Part 2 rehabilitates 500 feet of the existing stormwater collection and conveyance pipe system. The purpose and need for Part 2 is to optimize the volume of stormwater that is treated by eliminating exfiltration from the antiquated pipeline and directing it to the new bioswale.”

The stormwater system on the south side of I-90 under Hill Street collects runoff from a large commercial area and then discharges directly to the South Fork Coeur d’Alene River untreated.

The plan includes installing and using a cutting edge separator from engineering firm Contech called a CDS.

The CDS hydrodynamic separator uses swirl concentration and continuous deflective separation to screen, separate and trap trash, debris, sediment and hydrocarbons from stormwater runoff.

It is also capable of capturing and retaining 100% of floatable and neutrally buoyant debris 4.7-millimeters or larger, effectively removing sediment.

“This in-line system will provide the city with a single point for Operations and Maintenance activity with direct water quality benefits. This project provides an opportunity to pilot test a well-known stormwater quality device in the Silver Valley.”

The North Kellogg Stormwater Outfall is responsible for almost 50% of the city’s total stormwater and includes runoff from the Italian Gulch watershed and the residential areas of north Kellogg mix and discharge at this point.

The CDS separator will also be used for this area of the project.

Both of these outfalls end at the Hill Street Bridge on opposite sides of the South Fork Coeur d’Alene River.

The city of Kellogg has already done much of the designing for this project with engineering firm Alta Science and Engineering and is now moving toward putting the project out for bid with the hopes of completing the project during the summer.