Investigation of Tillage and Soil Amendments to Increase Infiltration in Vegetated Stormwater Controls

Vegetated stormwater control measures (SCMs) are a critical tool in North Carolina Department of Transportation's (NCDOT's) toolbox of practices for reducing the impacts of stormwater runoff. Infiltration is a key feature of these SCMs. Infiltration reduces runoff volume, and sediment and nutrient loss. Viable vegetation with proper rooting is essential to achieving infiltration. Establishment and maintenance of vegetated SCMs is often problematic due to poor soil conditions prior to seeding, associated with compaction and topsoil removal. These problems persist in time and limit both immediate and long-term effectiveness of vegetated SCMs. Recent research has demonstrated that applying tillage to ameliorate compaction on construction sites greatly enhances success in vegetation establishment, increases infiltration, and reduces runoff and erosion. The long-term (> 6-12 months) benefits of tillage as a construction site best management practices (BMP) have not, however, been determined and may be limited by soil reconsolidation over time with routine traffic and maintenance required in NCDOT right-of-ways. It may be necessary to periodically repeat tillage in vegetated SCMs in order to maintain their function. Unnecessary tillage and reseeding add costs, so it is important to determine to what extent, if any, tillage benefits are lost over time. Alternately, the addition of compost amendments during initial tillage application may limit soil reconsolidation and maintain SCM function. The proposed study is designed to determine the sustainability of vegetated SCMs following tillage pre-treatment, and to determine the need for, and necessary frequency of, tillage over time. We will simulate post-construction soil conditions on both cut and fill slopes and examine the effects of applying tillage BMPs with and without compost amendments on i) grass growth, ii) rooting depth, iii) infiltration rate, iv) soil bulk density and porosity, and v) soil penetration resistance over a period of three years. We will also evaluate the effectiveness of tillage BMPs on two active NCDOT roadside right-of-ways. Main projects steps will include: (1) site preparation to simulate construction activities including both cut and fill slopes; (2) main treatment establishment including tillage and tillage amended with compost; (3) sub-treatment establishment to examine effects of mower and maintenance traffic; (4) monitoring of vegetated SCM performance parameters over a period of three years; (5) establishing tillage treatments on two active NCDOT right-of-ways and monitoring for at least one year; (6) development of recommendations for implementation. Based on this study, we will assess the longevity of tillage BMPs. The project will develop recommendations for NCDOT as to whether compost incorporation improves and/or sustains BMP performance, and about the required frequency, if any, at which tillage must be re-applied. And the project will demonstrate tillage BMPs in roadside right-of-ways so that, if appropriate, they can be assessed for approval by the North Carolina Department of Environmental and Natural Resources (NCDENR).

Language

  • English

Project

  • Status: Active
  • Funding: $276456.00
  • Contract Numbers:

    FHWA/NC/2014-18

  • Sponsor 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

    Department of Biological and Agricultural Engineering
    Box 7625
    Raleigh, NC  United States  27695
  • Principal Investigators:

    McLaughlin, Richard

    Heitman, Josh

  • Start Date: 20130815
  • Expected Completion Date: 0
  • Actual Completion Date: 20170815
  • Source Data: RiP Project 35253

Subject/Index Terms

Filing Info

  • Accession Number: 01492620
  • Record Type: Research project
  • Source Agency: North Carolina Department of Transportation
  • Contract Numbers: FHWA/NC/2014-18
  • Files: RiP, STATEDOT
  • Created Date: Sep 11 2013 1:00AM