No abstract

Erosion and sediment control practices are implemented during construction activities to mitigate downstream effects, but limited field-performance data exists. Field assessments were conducted to evaluate ditch check installations during highway construction in Tama County, Iowa. Data collection included daily rainfall, topographical surveys of sediment deposition, pre- and post-rain event images, and visual observations. Variations to the standard Iowa Department of Transportation silt fence ditch check installation evaluated as part of this study include: (a) upgrading non-reinforced geotextile to a multi-belted, reinforced geotextile (i.e., SF-M1); (b) installing V-shape, as opposed to linear, while incorporating wire reinforcement to support hydrostatic loads placed on the geotextile, inclusion of a weir to facilitate controlled flow discharge, and offsetting the geotextile entrenchment location to improve ground securement (i.e., SF-M2); and (c) installing the dich check as described for SF-M2 substituting slicing for trenching (i.e., SF-M3). The modified wattle installation (i.e., W-M) incorporated a teepee staking configuration to facilitate ground contact, and an excelsior underlay, secured by sod staples, to minimize wattle undercutting. Results from field experiments indicated that sediment retention rates significantly improved for installations of SF-M2 and SF-M3 when compared with the standard installation and SF-M1 at the 85% confidence level, and served as viable control measures in concentrated flow applications. The W-M installation exhibited a statistically significant improvement in sediment retention over the W-S installation at the 95% confidence level. These findings suggest that ditch check performance is a function of specified practice and of installation methods described within regulatory agency specifications and design guidelines.

Sediment remains one of the most commonly occurring pollutants affecting the U.S.’s water bodies, as identified by the United States Environmental Protection Agency (USEPA) ( 1). Construction activities largely accelerate soil erosion and subsequent sediment deposition. The National Pollutant Discharge Elimination System Construction General Permit requires construction operators to implement erosion and sediment control (E&SC) plans to minimize downstream implications from sediment-laden discharge. However, E&SC practices are often designed from “rules of thumb” and lack scientific, performance-based evidence in their design and implementation. The Auburn University Stormwater Research Facility (AU-SRF), previously the Auburn University Erosion and Sediment Control Testing Facility (AU-ESCTF), is an outdoor research center dedicated to evaluating E&SC practices and products commonly used on highway construction projects. Large-scale test apparatuses and methods at AU-SRF are designed to mimic construction site conditions, including rainfall, flow rates, topography, and soil characteristics, to evaluate existing and novel E&SC practices. Since its inception in 2008, AU-SRF has provided small-, medium-, and large-scale testing evaluations for numerous Departments of Transportation and product manufacturers. Findings from controlled testing have continued to inform the selection, design, implementation, and maintenance of E&SC practices used on construction sites and protect downstream waters and infrastructure. In the first decade, AU-SRF has directed 13 research projects and produced more than 30 peer-reviewed publications and 100 professional presentations. As AU-SRF grows into its second decade and efforts reach outside of the southeastern region, the mission to advance knowledge through E&SC research and development, product evaluation, and training remains constant. This review synthesizes the research produced from large-scale testing at AU-SRF to date and presents ongoing projects.

Construction-related ground-disturbing activities leave exposed land susceptible to soil loss and increase the risk of polluting adjacent waterbodies with sediment-laden discharge. State and federal regulations require stormwater pollution prevention plans to be implemented during construction to mitigate the impact of stormwater runoff. Areas prone to soil loss can be identified early in site planning using soil loss modeling. Identification of these critical areas could influence the design and placement of erosion and sediment control practices. The Revised Universal Soil Loss Equation (RUSLE) can be applied to estimate the soil loss on construction sites in tonnes per Ha per year (tons/acre/year) by considering factors of rainfall erosivity, soil erodibility, length of slope, erosion control, and sediment control. This study integrates geographic information system (GIS) with RUSLE to create soil loss models for residential, commercial, and highway construction scenarios in the contiguous U.S.A. These three construction types were modeled in various locations throughout the country to assess erosive risk. Soil loss outputs were categorized into five risk tiers ranging from very low to very high. Southeastern states had the highest estimated soil loss during residential, commercial, and highway construction, reaching rates of 1,464, 706, and 1,302 tonnes per Ha per year (653, 315, and 581 tons/acre/year), respectively. This study provides a customizable model for any site-specific slope-length factor outside of the three construction scenarios modeled. Integration of GIS provides a unique opportunity to apply RUSLE across a larger landscape. The presented macro-scale data can be used for the design of erosion and sediment control practices.