Erosion, Sediment and Turbidity Control and Monitoring Research to Meet Water Quality Goals

The US Environmental Protection Agency (US EPA), under court order, established new rules in 2009 covering construction site runoff. Some of the key provisions include a maximum allowable discharge turbidity (to be implemented by 2013), surface outlets for basins, maximum time allowable before ground cover needs to be established, and the sampling of all discharges. However, again under court order, they were forced to remove the turbidity limit from the new requirements due to questions about how they calculated the number (280 nephelometric turbidty units, or NTU). The Agency has not clarified what the future of the turbidity limit or guideline will be, but it is likely to implement a new number within a few years, or at least when the next Construction General Permit occurs in 2015. At the state level, extra precautions in erosion and sediment control measures are often implemented where endangered species, often mussels, or high quality waters are present. Along with larger and more robust measures, the use of polyacrylamide (PAM) for erosion and turbidity control is often included. The proposed project is a multifaceted approach to providing additional tools and information to North Carolina Department of Transportation (NCDOT) in order to meet stricter discharge water quality requirements on construction sites. This will include a number of areas that will build on previous research, such as on-site rainfall simulation to test mulches and tackifiers and development of alternative turbidity control measures. A range of sampling and turbidity measurement methods will be explored and compared for costs, ease of use, and accuracy. In addition, the potential effects of the use of PAM on mussels will be determined using standard test methods under laboratory conditions. This will provide much needed information for agencies concerned about the potential negative effects of PAM use on aquatic organisms. While the concentrations of concern for a number of aquatic species have been shown to be much higher than would be expected to occur with typical uses, the project team are not aware of any testing on freshwater mussels. They are particularly vulnerable to sediment and turbidity and are often the cause for concerns when construction sites are planned near where they are present.