VEGETATIVE TREATMENT SYSTEMS FOR MANAGEMENT OF OPEN LOT RUNOFF: REVIEW OF LITERATURE

Abstract

Runoff from open lot livestock systems (beef and dairy) defined as Concentrated Animal Feeding Operations(CAFO) must be controlled by systems designed and managed to prevent the release of manure-contaminated runoff for stormsequal to or less than a 25-yr, 24-h design storm. This performance standard has been attained for open lot systems with somecombination of clean water diversion, settling basins, runoff collection ponds, and irrigation systems (baseline system).An alternative approach is to rely on overland flow and infiltration into cropland with perennial forage or grasses fortreatment of open lot runoff. Such vegetative systems have been researched since the late 1960s. This article reviews theresearch literature on vegetative treatment systems (VTS) for managing open lot runoff summarizing available science onsystem performance, design, and management.Based upon this review of the literature, the following conclusions are drawn about the application of VTS to manage runofffrom open lot livestock production systems:<br>(1) Substantial research (approximately 40 identified field trials and plot studies) provides a basis for understanding theperformance of VTS. These performance results suggest that a vegetative system consisting of a settling basin and VTA orVegetative Infiltration Basin (VIB) has the potential to achieve functional equivalency to conventional technologies.<br>(2) The existing research targeting VTS is confined to non-CAFO applications, likely due to past regulatory limits. Uniquechallenges exist in adapting these results and recommendations to CAFO applications.<br>(3) The pollutant reduction resulting from a VTS is based upon two primary mechanisms: 1) sedimentation, typicallyoccurring within the first few meters of a VTS, and 2) infiltration of runoff into the soil profile. Systems relying primarily onsedimentation only are unlikely to perform equal to or better than baseline technologies. System design based uponsedimentation and infiltration is necessary to achieve a required performance level for CAFO application.<br>(4) Critical design factors specific to attaining high levels of pollutant reduction within a VTS include pre-treatment, sheetflow, discharge control, siting, and sizing. Critical management factors include maintenance of a dense vegetation stand andsheet flow of runoff across VTA as well as minimization of nutrient accumulation.