Improved Approaches to Environmental Compliance During Highway Construction

Road construction results in large areas of exposed soil which are susceptible to wind and water erosion. These areas are required to be kept under control and sediment should be retained on the project. An erosion and sediment control plan is required, and regular inspections are used to ensure that the plan is followed and practices in place are functioning properly. These inspections are required after >0.5” of rain or weekly, whichever occurs first, with special attention to outfalls to surface waters. On active areas with exposed soils, it can be difficult, dangerous and sometimes impossible to drive around a site to conduct the required inspections after a rain event due to the slippery conditions. However, relatively inexpensive unmanned aerial vehicles (UAVs) have provided new capabilities ideally suited to facilitate these inspections from a single point of easy access. These ‘flying cameras’ can be either be manually controlled or pre-programmed to fly to inspection points and collect either high-resolution images or video of the existing conditions, both of which provide a record and documentation of the inspection. Surface drainage and catchment areas of two sediment basins as captured by an inexpensive unmanned aerial vehicle (UAV) and post-processed using modern photogrammetry techniques. Sediment basins are currently designed based on 10- or 25-year recurrence rainfall events for the local area, and a number of assumptions surrounding drainage area, land cover, and runoff coefficients. Previous work has suggested that changes in surface topography that occur at different stages of construction (Brown 2011) often result in water that doesn’t drain to the basin as expected. While evaluations of sediment retention have been conducted (Brown et al., 2015; McCaleb and McLaughlin, 2008; Line and White, 2001), the hydrological performance of sediment basins with skimmer outlets has not been characterized relative to the watershed conditions. Furthermore, there is little available information on the appropriate factors to use for predicting runoff on construction sites. Using a UAV to collect aerial surveys around an instrumented basin a preliminary investigation into runoff and discharge at an active NCDOT project suggested that even with considerable rainfall, a relatively low fraction (17% of rainfall) reached the basin. Dust control is also required under dry conditions in order to comply with air quality regulations. This is normally achieved with frequent passes of a tanker truck spreading water, often several times per day, which requires a full-time operator, a source of large amounts of water, and which adds to the traffic on haul roads. There are a wide variety of dust control products available which could be more effective, more economical, and more environmentally friendly than running water trucks up and down the road. These are widely used in arid areas and the technology may be transferred readily to construction projects in North Carolina. Silt fence, used on most construction projects, is currently constructed using steel posts that are required to have 1.25 lb of steel per foot. There is no known testing standard or specification which has been conducted to allows a user to determine whether a post can appropriately if that is an appropriate resist the forces specification based on expected forces exerted by either water or soil backed up behind the silt fence. It is likely that if post designs are optimized, posts could be made from of less steel or from other materials. Optimized, economical posts could be sufficient to withstand the pressures typically exerted on silt fences at considerable cost savings. Wood posts, for example, are a sustainable resource with a much lower environmental footprint.

    Project

    • Status: Active
    • Funding: $195722
    • Contract Numbers:

      FHWA/NC/2019-05

    • Sponsor Organizations:

      North Carolina Department of Transportation

      Research and Development
      1549 Mail Service Center
      Raleigh, NC  United States  27699-1549
    • Managing Organizations:

      North Carolina Department of Transportation

      Research and Development
      1549 Mail Service Center
      Raleigh, NC  United States  27699-1549
    • Project Managers:

      Kirby, John

    • Performing Organizations:

      North Carolina State University, Raleigh

      College of Agriculture and Life Sciences
      Department of Soil Sciences, Campus Box 7619
      Raleigh, NC  United States  27695-7619
    • Principal Investigators:

      McLaughlin, Richard

    • Start Date: 20180801
    • Expected Completion Date: 20200731
    • Actual Completion Date: 0

    Subject/Index Terms

    Filing Info

    • Accession Number: 01677403
    • Record Type: Research project
    • Source Agency: North Carolina Department of Transportation
    • Contract Numbers: FHWA/NC/2019-05
    • Files: RiP, STATEDOT
    • Created Date: Aug 2 2018 2:52PM