• Winter conditions, conventional versus vegetative treatment system (VTS): Winter conditions can provide challenges for both traditional systems (holding pond and irrigation system onto cropland) as well as the vegetative treatment area (VTA). Large precipitation events or snow melts can result in holding pond levels requiring winter or early spring runoff applications to maintain the required capacity to hold a 25-year, 24-hour storm. A continuously vegetated VTA has many advantages over a corn or soybean field under these conditions. Erosion is less, infiltration is generally better, and grasses and alfalfa have a longer growing season for utilizing water and nutrients. So while winter or early spring precipitation events are problematic for VTAs, they can present an even greater risk for our traditional systems. • In the winter for Iowa-permitted CAFOs: In Iowa, there are earthen basins, concrete basins, and basins with concrete bottoms and earthen walls. For permitted CAFOs with a VTS, unlined basins can hold water for seven days. This is a variance above general CAFO permits which only allow unlined basins to hold water for three days. During chronic wet weather in Iowa, some sites have received intermittent rain for three to four days, creating saturation soil conditions in the VTAs during that period. Release from the basin during saturated conditions can lead to runoff of feedlot effluent. It is for this reason that we contain feedlot runoff in the basin until the end of a rainfall event. For CAFOs in Iowa, site operators are required to hold all liquid off of the VIB (vegetative infiltration basin) or VTA during the winter. This means any lot runoff during the winter should be held in the basin. Iowa permits state, “During frozen conditions, also called non-growing season (November 1 through March 31), the applicant is required NOT to release any manure, settled effluent, or runoff or process water into the VIB or VTA.” Aggressive snow removal from feedlots to keep clean snow out of the system is necessary for maintaining empty basin volume capable of handling spring melting. The seven-day limit for holding liquid in the basin is only in effect for non-frozen conditions considered to be April 1 through October 31. • In the winter for non-permitted CAFOs in Nebraska: In winter, when the ground is frozen, usually the runoff water is also frozen. Our experience suggests that air temperature and surface soil temperature rise to above freezing several times each winter. So even during winter, it is possible to use a VTA. The critical time for a VTS is just after snowmelt that has occurred after a long hard freeze. The ground is completely frozen, but the snow has melted. In this situation, the producer must hold the liquid in the sediment basin until the ground dries and thaws enough for distribution to the VTA. For the pump and sprinkler VTS, cold temperatures are especially problematic. Such systems must be capable of operating at near-freezing temperatures. The approach we have taken is to either bury the system below frost to protect the pump and motor or to provide very simple ways of draining the susceptible components. In all of the systems we have designed, we need to evacuate only about 20 to 50 gallons from the system to protect the pump and risers. Authors: Lara Moody, Iowa State University; Rick Koelsch and Chris Henry, University of Nebraska

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