RES2016-17: Highway Construction Sediment Basins: Assessment of Water Quality Treatment Performance

Sediment basins with outlet orifice skimmers are one of forty erosion prevention and sediment control (EPSC) devices that the Tennessee Department of Transportation (TDOT) utilizes to meet regulatory runoff quality permitting requirements at their highway construction sites. Regulations set in place by the US Environmental Protection Agency (US EPA) and Tennessee Department of Environment and Conservation (TDEC) require performance standards that often affect TDOT’s existing design criteria for stormwater control measures (SCM). TDOT needed to update their manual’s engineering design criteria for sediment basins based on new regulations and modeling/monitoring datasets including field verification. The goal of this project was to initiate a performance analysis of the current TDOT design criteria for sediment basins, basing the basin sizes on Chapter X of TDOT’s Drainage Manual and the 2013 TDOT Report Engineering Design Guidance for Highway Construction Sediment Basins by Neff and Schwartz. In the 2013 TDOT Report basin sizes were a developed using hydrology and sediment models on three key criteria: drainage area size, slope, and soil type. Following the modeling effort, this study monitored the influent and effluent of two separate highway sites with varying catchment slopes, soil types, and drainage areas. The sites were located on US64 in Morgan County and I-640 in Knox County. The monitoring devices used at each site were chosen for the topographic constraints, and included ISCO samplers and/or Pinson weir buckets. Per each site, the following monitoring data were collected during rainfall events: inlet and outlet water samples, flume sediment deposits, weather data, and volumetric flow data. Six rainfall events were collected at the Morgan County site and five from the Knox County site. The site field data were analyzed to assess basin performance and characterize particle size variability. Results showed that the Morgan County and Knox County basins performed an average of 76.8% and 97.4% mass sediment reduction between the influent and effluent, respectively. There was a large difference in contributing sediment masses, Morgan County had an average event inlet mass of 1.93 x 10³ kg of soil, where Knox County had an average of 1.60 x 10⁻³ kg. RUSLE2 modeled sediment yield for Morgan County resulted in 19.0 ton per acre (t/ac) compared to a field value of 22.0 t/ac; Knox County resulted in 3.8 t/ac compared to field value of 0.13 t/ac. General design information from observations included that sediment basins need to be located where groundwater will not impact their performance. Drainage areas over 5 acres create basins so large that they are difficult to locate on a linear corridor highway project site. Location of the basin must not interfere with construction staging. Also, a forebay is a vital component of the sediment basin to trap larger sediment particle size material and not reduce the effective basin volume for the smaller particles to settle; however current design criteria by TDEC appears to be oversized and unnecessarily large. Basin performance was variable were the % sediment retained at the Morgan County site varied from 47.7% to 97.5%, and at the Knox County site it varied from 94.3% to 98.4%. The difference in sediment performance was based on the inlet mass loading and noted above the Knox County site the loadings were very small compared to that measured at the Morgan County site. Though basin performance is a function of multiple site conditions such as site slope and drainage area, soil source material was found to be particularly important. With only two basins monitored and wide differences in performance, it is highly recommended that additional data be obtained to better understand the site factors that affect sediment reductions in the basins.

Language

  • English

Project

  • Status: Completed
  • Funding: $96753
  • Contract Numbers:

    RES2016-17

  • Sponsor Organizations:

    Tennessee Department of Transportation

    James K. Polk Building
    Fifth and Deaderick Street
    Nashville, TN  United States  37243-0349
  • Managing Organizations:

    Tennessee Department of Transportation

    James K. Polk Building
    Fifth and Deaderick Street
    Nashville, TN  United States  37243-0349
  • Performing Organizations:

    University of Tennessee, Knoxville

    Center for Transportation Research
    Conference Center Building
    Knoxville, TN  United States  37996-4133
  • Principal Investigators:

    Schwartz, John

  • Start Date: 20151001
  • Expected Completion Date: 20190531
  • Actual Completion Date: 20190531
  • USDOT Program: Transportation, Planning, Research, and Development

Subject/Index Terms

Filing Info

  • Accession Number: 01763323
  • Record Type: Research project
  • Source Agency: Tennessee Department of Transportation
  • Contract Numbers: RES2016-17
  • Files: RiP, STATEDOT
  • Created Date: Feb 3 2021 3:20PM