It has been about fifteen years since soil bioengineering and bioengineering technology have been used in projects to protect slopes and river banks against erosion. Now many consulting firms as well as state and federal agencies promote and practice these techniques. Despite a widespread support of these techniques, many projects have failed. Therefore, it is deemed necessary to develop a set of design guidelines to ensure a higher rate of success. In order to develop design guidelines for soil bioengineering and bioengineering technology, a pilot study was conducted to determine the amount of work already done in these areas, and to define the existing research needs. This report comprises (a) a summary of literature review, (b) interviews with eleven practitioners in the field, (c) an evaluation of three projects done in Minnesota, (d) current research needs, (e) and a brief evaluation of three sites in the vicinity of the Twin Cities area as potential outdoor laboratories to conduct research in the needed areas. It also includes a summary of a site visit of the department of Soil Bioengineering and Landscape Construction at the University of Agricultural Sciences in Vienna, Austria. The study shows that a significant number of studies have been done on topics related to soil bioengineering techniques. However, these studies mainly address the problems at a micro scale, and hence, there is a gap between existing knowledge and practice. Therefore, there is an urgent need to not only study some of the fundamental processes and mechanisms involved in soil bioengineering techniques, but also to investigate these processes at a macro scale to evaluate their strengths and impacts when applied to streambanks and slopes.
Recent interest in detention ponds and constructed wetlands has extended to improving the quality of the runoff by reducing the concentrations of pollutants associated with stormwater runoff. Lead, zinc, copper, cadmium, phosphorus, and chloride are the contaminants of primary concern in the state of Minnesota. This study examined removal mechanisms in detention ponds. Three wetland graminoids, Glyceria grandis (reed manna grass), Scirpus validus (soft stem bulrush), and Spartina pectinata (prairie cordgrass) were studied for their phytoremediation capabilities for the six target contaminants. The uptake rates of the six target contaminants by the sediments of a detention pond were determined. These two removal processes were incorporated in an analytical model that can be used to determine critical parameters for the design of a detention pond that would produce effluent guidelines that meet requirements set by the Minnesota Pollution Control Agency. Removal rates for the three species were determined. Uptake rates were dependent on both the contaminant and species. The removal rates of the phytoremediation and the sorption sediment experiments were combined to develop a numerical model to simulate the removal mechanisms in detention ponds. This model can be used to develop design plots for a detention pond.
