Talking vegetative treatment system manages runoff
by Loretta Sorensen
It was clear that Brian Andreason’s 550-head capacity feedlot at Kennard, NE, located near a stream and above a perched aquifer, needed a vegetative treatment system (VTS) to help mitigate runoff risk. But University of Arkansas professor and Water Management Engineer Dr. Christopher Henry (formerly at the University of Nebraska/Lincoln) thought Andreason would greatly benefit from use of a “talking” VTS.
“By ‘talking’ I mean a VTS with a human machine interface (HMI) that gives the user some feedback about the status of the system using moisture sensors that indicate soil moisture levels in the VTS area whenever Brian needs that information, ”Henry says. “It also includes floats in sediment basins and the system can initiate text messages to Brian to let him know if the sediment basin is full and when soil moisture conditions are appropriate for distributing runoff water to the vegetative area. I believe it’s probably the first applications of precision animal ag technology to the animal industry production area.”
Andreason worked with Henry and the Nebraska Department of Environmental Quality to help make his feedlot environmentally sustainable. Henry notes that topography of Andreason’s feedlot involved a number of complicating factors that were resolved with this unique VTS design.
“A feedlot that’s close to ground-water can’t use a holding pond because of the risk of impacting that ground water,” Henry says. “With the moisture sensors placed in his 9-acre vegetative area, Brian can manage water distribution very accurately and avoid any contamination issues. The HMI also allows him to maintain a log that documents his compliance with managing effluent. It will clearly show that he didn’t over irrigate or experience leaching issues. This tool could be a very effective way for livestock and feedlot owners to manage their operation in an area with sensitive geologic characteristics.
”Andreason’s VTS comprises a clean water diversion capable of accommodating 169 cfs (cubic foot per second) routed to the west and the south of the production area. Minimum height on the diversion is 1.5 feet. Topsoil removed from the diversion was used to construct the system’s two sediment basins and raise the feedlot pad to increase pen slope and provide better pen drainage.
Runoff flows from two separate pen areas, each under 4 acres, into the sediment basins. The east basin has a 20 hp 320 gallons per minute variable frequency drive (VFD) pump station and below grade inlet strainer to pump runoff to the vegetated treatment area (VTA). The VFD is controlled with an industrial programmable logic controller (PLC), allowing for additional management options to be implemented in the future. The PLC also provides options for low pressure shutdown, variable pressure control and slow start up to minimize water hammer. An in-line filter minimizes sprinkler maintenance.
Both basins are designed with a 1-foot freeboard for safety and sized to control the 25-year 24-hour runoff volume plus annual solids accumulation.
The near 9 acre VTA can manage nitrogen from a 4 ton/acre fescue VTA and manage feedlot runoff using 50% of the Available Water Holding Capacity (AWC) in the soil,which is 4.55 inches within a four-foot rooting depth. Soil intake rate is 0.3 in/hr. Sprinkler impacts will apply water at a maximum rate of 0.17 in/hr. Four sets of 10-pod KLine pods were designed to minimize pressure variation. The pressure pipeline is placed so water can be stored in the pipeline between distributions. A minimum 8-foot separation exists for the VTA between the perched water and surface elevation. The VTA is hayed once each year.
“This is a pilot but the cost of the additional controls was about $5,000,” Henry says. “Brian’s overall cost is higher than typical because of additional pipe, stream crossing, excavation and topographical constraints not experienced in all circumstance. The pump could have been diesel but Brian preferred the more expensive electric. However, this system is unique and one-of-a-kind and is a pilot for other systems. It would be easy for vendors to apply this to another feedlot’s situation.”