A crew takes measurements to see if this is the best spot to place a culvert for a trail crossing. Culverts come in many shapes and sizes depending on the water volume they are expected to handle. Photo courtesy of Cook County Soil and Water
With numerous creeks, streams, rivers, and lakes, and untold numbers of large and small ponds, Cook County has a lot of fresh water moving from one place to another, which also means the county has a lot of culverts and bridges. What is the state of the culverts and are they impacting water quality? This is the question the Cook County Soil and Water is working to discover. Using ArcGIS, conservation technician, Michaela Clingaman, is working to identify where rivers or streams intersect county owned roads. To date, she has a rough count that puts the number north of 950.
Clingaman has just begun her work and will sometime this summer, weather permitting, get out and start to inventory culverts throughout the county. The SWCD will be partnering with the Conservation Corps of Minnesota and Iowa to work with an intern “who wants to get some experience working in the field.”
An accelerated implementation grant totaling $130,000 was awarded to Cook SWCD to complete a culvert inventory in Cook County from the Minnesota Board of Water and Soil Resources (BWSR). For fiscal year 2019, BWSR approved $13.7 million in Clean Water Fund grants to improve water quality in streams, lakes, and groundwater across the state. The $13.7 million funds 52 separate grants.
Culverts
Culverts for this project will be all structures under roads that allow water to flow from one side to the other. Culverts come in all sizes and shapes including round, pipe arch, box, ellipse, or open bottom and they can be made from a variety of materials including metal, concrete, plastic or other material. If the span is greater than 10 feet, a culvert is termed a bridge. If designed and installed correctly they allow safe motorist crossings, quality fish passage, protect against erosion and help maintain water quality for aquatic organisms and plant life.
Why inventory culverts?
Knowing the location of culverts, their physical attributes, and condition is important for managing assets, planning, and identifying if crossings are negatively impacting water quality or fish passage. This project will create a geodatabase of culvert locations with associated attributes, said Clingaman, which will one day hold all the county’s culvert assets.
Data collected will be included in the Minnesota Department of Natural Resources’ Culvert Inventory Application Suite and be consistent with inventory work being done statewide. Anyone will be able to access the data, she said.
How hard is it to inventory culverts?
For that I asked Rick Anderson, a Schroeder township supervisor. Over the last couple of years the township has sought to improve its roads, the longest being the 4-mile Sugarloaf road. One of the first things that needed to be done was an inventory of the culverts on the Sugarloaf, which proved challenging.
“I can’t remember off the top of my head the exact number of culverts on the Sugarloaf Road but I think it was 11 or 12. Because the town did not have a record, we walked the entire length of the road looking for them. It was quite a task due to the time of year, the amount of foliage along the side of the road and how dry it was, so following the water was difficult.
“We did GPS each one and with the help of the county we used a topographical map of the road to record the culverts. We also made a record of the size, shape, length and general condition of each culvert.
“Actually, this is on my list this spring for our Township Road & Bridge committee to update this list, the condition of the culverts and start budgeting for the replacement of culverts as some of those culverts were in poor condition.
“One of the biggest surprises we found was how big some of these culverts actually are, ranging in size from 16 inches to 60 inches with most larger than 36 inches. When we drive on our roads you don’t always see the infrastructure that went into them!”
Inventory Benefits
Those who have stream fished in Cook County have come across a culvert that is perched, substandard or severely damaged. These culverts can become a barrier for fish, especially when water is too low for them to pass through. Improperly sized, improperly placed, or damaged culverts can have a multitude of negative environmental and structural impacts. For example, culverts can cause issues with erosion on the banks or streambed, impacting fish habitat and water quality. Inventory data will be used by the county Highway Department and the SWCD to identify and prioritize culverts in need of replacement.
Watersheds in northeast Minnesota are generally pristine. Properly installed, replaced or retrofitted culverts can help to minimize the increased threat to water quality from development pressure and climate change. A culvert, while low tech, can have a significant effect on aquatic life and the stability of a stream or river if it is sized or installed incorrectly. Clingaman aims to be part of the solution to addressing culvert issues that will best benefit water resources.
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