Evaluating systems to reduce road improvement impacts on mountain streams.

692197666Final report; July 1, 2004-June 30, 2007.PDFTech ReportFHWA/NC/2006-44StreamsRiversEnvironmental impactsHighway designNorth CarolinaNorth Carolina. Dept. of Transportation. Research and Analysis GroupMcLaughlin, Richard A.Jennings, Gregory D.King, Scott E.North Carolina State University. Soil Science Dept.North Carolina State University. Dept. of Biological and Agricultural EngineeringNTL-ENERGY AND ENVIRONMENT-Environment ImpactsNTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATIONNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceUS Transportation CollectionSediment is the most common pollutant affecting North Carolina\ue2\u20ac\u2122s waterways, impacting a range of aquatic organisms, reducingreservoir capacity, and hurting their aesthetic value. Construction activities, including roadway projects, are a significantcontributor of state-wide sediment loading. The NC DOT program of widening and paving rural roads in the mountain regionprovided an opportunity to evaluate new types of roadside erosion control BMPs with the goal of protecting the particularlysensitive trout streams commonly found there.Two roadway paving projects were each divided into experimental sections installed with either 1) the standard DOT BMPsconsisting of narrow sediment traps and rock checks, 2) the new fiber wattle check dams (consisting of a mix of straw wattles andcoir logs) with 100 grams of granulated polyacrylamide (anionic PAM 705) added to each, or 3) the new wattle check dams alone(no PAM added).The results suggest a significant advantage to the use of the new BMPs. At the first site, from June 2006 to March 2007, theaverage turbidity values (in NTUs) for the stormwater runoff for were 4,198 for the Standard BMPs, 30 for the ExperimentalBMPs with PAM, and 187 for the Exp. BMPs alone. The second site showed similar results with average turbidity values of 64for the Exp. BMPs with PAM, as compared to 852 for the Standard BMPs. Sediment loading at both sites was similarly skewedwith dramatic decreases in sediment discharged off site from the new BMPs. At the first site, the Standard BMPs lost an averageof 944 lbs (428 kg) of sediment per storm event as compared to just 1.93 lbs (0.88 kg) for the BMPs with PAM and 6.53 lbs (2.96kg) for the Exp. BMPs alone. At the second site, the Standard BMPs lost an average of 8.84 lbs (3.63 kg) per storm eventcompared with 1.67 lbs (0.76 kg) for the Exp. BMPs with PAM