Reduction of pH Levels from Underdrain Outlets

Effluent from some open graded underdrains has elevated pH and soluble minerals. Precipitate is found at under drain outlets. This sometimes enters the storm sewer system, which is considered an illicit discharge under Michigan Department of Transportation's (MDOT's) municipal separate storm sewer system (MS4) permit. MDOT has been monitoring water quality at about 10 locations throughout the state to confirm that this problem exists. The cause of the high pH and precipitate is believed, but not confirmed, to be from the fine dust contained in recycled crushed concrete used as a base material layer under the roadway. Perforated underdrain pipes are usually placed under the layer of crushed material to collect water and protecting the roadway from damaging saturation and freezing conditions. Better understanding the water chemistry that leads to elevated pH and precipitate and best practices to address the problem would help MDOT improve water quality from existing outlets and future construction.

  • Supplemental Notes:
    • SPR-1696


  • English


  • Status: Completed
  • Sponsor Organizations:

    Michigan Department of Transportation

    Van Wagoner Building
    425 W. Ottawa Street
    Lansing, MI  United States  48909
  • Performing Organizations:

    Lawrence Technological University

    21000 West Ten Mile Road
    Southfield, MI  United States  48075
  • Principal Investigators:

    Bandara, Nishantha

  • Start Date: 20180501
  • Expected Completion Date: 20201231
  • Actual Completion Date: 20201231

Subject/Index Terms

Filing Info

  • Accession Number: 01732720
  • Record Type: Research project
  • Source Agency: Michigan Department of Transportation
  • Files: RIP, STATEDOT
  • Created Date: Mar 4 2020 2:16PM