Date of this Version
TRANSACTIONS of the ASAE Vol. 23, No.3, pp. 681, 682,683,684,687, (1980)
The vegetative filter approach uses overland flow or shallow channelized flow to treat feedlot runoff by infiltration, dilution and filtration. Based on extensive monitoring of four field systems in Illinois over a two year period, acceptable performance standards were selected. Design criteria to meet the standards were developed for both the overland flow vegetative filters and the channelized or serpentine terrace filters. A major design criterion for both types of vegetative filters is the time required for applied runoff to flow the length of the filter.
An alternative to using zero-discharge treatment systems to control feedlot runoff is to replace the holding pond and dewatering equipment with a vegetative filter treatment and infiltration area. This component has been called by various names but will be referred to here as a vegetative filter. A vegetated area such as a pasture, grass waterway, or terrace channel is used to treat feedlot runoff by providing an area in which settling, dilution, absorption of pollutants and infiltration can occur. Many existing small feedlots already have some form of a vegetative filter. At many others, such a component could be added with a minimum of expense and effort. While systems of this type would certainly not be advisable or practical for every situation, they could provide low-cost runoff control for many feedlots, especially small feedlots that are not close to streams or lakes.
Several types of overland flow systems for treating feedlot runoff have been tried with varying degrees of success. Some were designed to absorb most of the applied runoff by infiltration into the soil; others are intended to remove very little by infiltration but to provide treatment during the flow process.
A study was begun in Illinois in 1975 to evaluate vegetative filter systems and, if feasible, to develop design criteria for them. Four vegetative filter systems were installed, each consisting of a settling facility, a distribution component and the vegetative filter area, as illustrated in Fig. 1. No runoff storage unit was provided; the runoff from a storm event went directly to the filter area. Similar concrete settling basins were used at each location. Two of the systems were of the serpentine waterway configuration; similar to those reported by Swanson et al. (1975). These are termed channelized-flow systems in this paper. The remaining two systems comprised wide, mildly sloping areas which operated with a shallow overland flow. They are termed overland-flow systems.
The systems were closely monitored over a period of two years. As reported in an earlier paper (Dickey et al., 1977), the performance of both types of systems was considered satisfactory in controlling feedlot runoff. For the design concepts to be usable on a wide scale, however, design criteria which will result in predictable performance under varying conditions are necessary. Criteria for both channelized and overland flow systems have been developed and are presented here.