DRAINAGE DITCHES ARE A DIFFERENT KIND OF ROAD

An analogy could be made that a county ditch is just like a county road that carries a different form of traffic. Recently I spent a couple of hours with Brown/Nicollet/ Cottonwood Clean Water Partnership (BNCPWC) staff walking along County Ditch 13A in Oshawa township. Yes, ditches are similar to roads except in the area of ownership. County roads are owned by the county; county ditches are owned by the landowners along the ditch that benefit from the ditch being there. The roads in the county carry cars and trucks; the ditches carry mostly water. Ditches were built for the purpose of draining land so it would become more productive. They were built well and they do a good job of removing water from the landscape - but the water that moves through the ditches sometimes carries “unwanted passengers” in the form of sediment, phosphorus, and bacteria. These unwanted passengers have received a lot of attention since the passage of the Clean Water Act in 1972.
County Ditch 13a is located in the confines of the 7 Mile Creek Watershed. This watershed has received a lot of attention because the creek is located in the Nicollet County Park and it is a designated trout stream. The clean water partnership has received grant money to monitor water quality and put practices in place that will reduce the sediment entering the Minnesota River at the mouth of the creek. Tests have shown that 5,000 tons of sediment enters the Minnesota River each year from this watershed. One of the unique efforts happening in the watershed is an on the ground inspection of the ditches. Kevin Kuehner, Water Quality Specialist with BNCPWC explained the work they are doing.
Walking along the sides, a survey is taken of the ditch and the side tile outlets entering. Observations are entered into a hand held computer that records information about the ditch. As we walked along the ditch, each tile out letting into the ditch bank was given a number and was “pointed” or located using global positioning system (GPS). A photo is taken and a rating is given to the tile outlet. For example it could be clay or concrete or corrugated metal pipe. The outlet is measured for size and rated as to condition i.e. poor, medium, excellent (3-2-1). Other notes are taken to indicate if there has been undercutting near the outlet. Undercutting is when the soil has moved away from the outlet because of the connection becoming disconnected from the field tile or it could happen because there is just too much water surging through the outlet. The undercutting – if left unrepaired, could result in the ditch bank falling away and the possibility of a blow out occurring.Undercutting could lead to a large gulley being formed in the bank of the ditch. This leads to deposits of soil in the bottom of the ditch and means slowing down the flow of the water and eventually a need to clean the ditch.
The outlet is also given a rating for the potential to deliver sediment to the waterway. Kuehner looks for sediment in the bottom of the pipe and checks to see if sediment is built up in the ditch channel at the end of the pipe. At one site, a pile of dirt about four feet high was resting in the main channel and grass was growing there. (This is a strong indication that there is significant soil loss from the field being drained.) Other structures recorded are drop structures. These are devices put into low areas where the water collects and they slow down the water as it enters the tile or the ditch. Most of these have little or no buffer around them and are points where soil can enter the system. These are also given a sediment delivery rating. The data collected is then plotted onto maps and landowners as well as soil technicians have a tool to use to find the most likely spots to put some erosion control practices on the ground.
The drainage authority is charged under Mn. Statute 103E to incorporate a comprehensive assessment of the environmental aspects of any proposed project. Does this directive also cover repairs to drainage systems?The ditch assessment described above is a wonderful tool to help landowners make some changes that could mean decreased costs for repairs. All of these measures come into play because our society has placed a high value on clean water. But this value comes with a cost. Where does the responsibility lie? With the landowner? With the local, state, or federal government? Or with all of us? The assessments and the conservation practices needed are upfront costs. They could save money in the long run. Who should pay these costs? End.