Minnesota Department of Transportation

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Research & Innovation

New and retrofitting of egress inlets, open conveyances, and culvert apron outfalls for trash and plastic collection from stormwater transport

Need Statement 704

Problem

State and county Highways with urban drainage systems are receiving and passing unprecedented amount of trash to receiving waters. Trash that also includes needles and various forms and types of wind and water transportable waste. The change in the amount of stormwater induced trash may be a function of changes in patterns and intensity of rainfall.

Objective

The industry is designing and developing trash capture technologies for (1) storm drain inlets, (2) in-line, within pipes or at the outlet of the stormwater systems and (3) open-water in the receiving water body. Various trash capture systems can be demonstrated by the manufactures to capture trash at particular size fragments, but the systems are the same. A recent EPA 2021 Snapshot of emerging issues listed several trash capture technologies for inlet and culverts for different situations and locations. It is not known how efficient the technologies perform under various debris fractions, how the device affects drainage flows and flood avoidance, retrofit potential, cost to keep functional, and maintenance frequency.

Previous research

Unsure, but unable to locate trash collection BMPs and potential hydraulic change in flow. Trash control is an emerging USEPA issue of concern, and EPA showcases several examples.

MnDOT Strategic priorities

How does the project align with MnDOT Research Strategic Priorities?

  • Innovation & Future Needs: Pollution to water bodies comes in many forms. Construction and post -construction design, implementation and ultimately maintenance of BMPs follow requirements listed in permits. Every 5 years the permit is updated to reflect improvement or changes to existing concerns that relate to the discharge of stormwater from construction activities from impervious surfaces. While emerging issues does not mean new or modified permanent NPDES stormwater permit requirements will occur, once an item is listed by the EPA, regulated parties should pay attention. Rather than let the EPA determine requirements, it is important that stakeholders of compliance agree that changes to permit requirements does not create new issues of concern (see Safety below) and example engineering solution exist prior to enforceable regulations. The innovation is to verify changes in hydraulic flow that enable flowing trash capture does not create undesirable results in multiple drainage configurations
  • Advancing Equity: Economically challenged areas commonly receive a disproportionate waste load from multiple sources. There are unpublished reports (personal communication with MnDOT Maintenance Staff) that show a defined distance from fast food restaurants (about the time it takes to eat) has measurable paper and plastic waste collections. Urban areas near stores and bars also show increased loading of various forms of trash. For example, the permanent storm water treatment systems (filtration and swirl chambers) along University Avenue collects considerable waste that remains visible, but potentially dangerous to safely collect and remove. Advancing Equity removes the urban and rural unfairness by collecting floatable trash from source to end point (receiving water). The more a plastic waste is damaged by vehicle tires, abraded on paved surfaces, the faster transition into microplastics exposure. This will aid in keeping roads and other amenities (e.g. public beaches) that receive stormwater runoff safer for everyone.
  • Asset Management: When trash and waste end up deposited along a transportation system, it becomes the property of the transportation authority. Even with annual spring cleanup (adopt a highway) by the public along transportation systems, not all dispersed waste can be, or is removed. In addition, there are locations along transportation assets where waste cannot be removed by public volunteers (e.g. high-risk areas along light rail and bus rapid transit) that have drainage that connect to waters. Site specific trash collection and concentration systems at the source from inlets, along conveyance pipes, or culvert outfalls will require maintenance education, time, equipment and money to successfully operate. It is unreasonable to believe that every trash collection system will have the same maintenance and disposal calculation, nor identical levels of service to keep the system functioning as intended. It is imperative that costs to install and maintain be understood. It is possible to privatize trash capture maintenance and disposal.
  • Safety: Collections of waste inside containment screens and filter textiles are not homogeneous. It may contain sharps and other shard/rough materials creating unsafe conditions to those managing the system. Depending on type of floating trash traps installed, the material may be difficult to access, handle, (bulky) and heavy. Safety measures must address appropriate PPE, necessary equipment to remove and reinstall collection device, and disposal transport.
  • Climate Change & Environment: Limit gross plastic release through egress inlets to the environment. Limit public exposure of hazardous fragments of trash to public waters, especially those outlets near beaches. Limit washup of waste materials on public and private property. Improve water quality for the state. Improve visual quality for the state. Add point source control of floating waste materials with easiest maintenance reach compared to all other potential waste distribution collection over dispersed waters of the state.

Expected outcomes

  • New or improved technical standard, plan, or specification
  • New or improved manual, handbook, guidelines, or training
  • New or improved business practices, procedure, or process
  • New or improved tool or equipment
  • Evaluation of a new commercial product(s)
  • New or improved technical standard, plan, or specification

Expected benefits

  • Construction Savings.   None. Trash management is already part of the contract.
  • Decrease Engineering/Administrative Costs. Not expected.  But source control pollutant prevention measures are more effective and least expensive rather than dispersion over an area. Improves visual and aesthetic quality of transportation systems.
  • Environmental Aspects. Reduction of floatable wastes to public waters. Improved public safety of water recreation locations. Reduction in microplastics.
  • MnDOT Policy. Partially fulfils a goal for the reduction in plastics during and post construction. Limits the release of a knowable pollutant to waters of the state. Leadership in water quality management.
  • Lifecycle. Unknown. But wastes end up somewhere. Source control provides the greatest return on investment.
  • Operations and Maintenance Savings. Unlikely as the system will require a definable time and effort to realize the reduction in plastic and other waste from leaving the transportation ROWs.
  • Reduce Risk. Could go either way. At this time there are drug needles showing up within the vegetated spaces, catch basin sumps, and stormwater basins in metro regions. If properly managed, the existing risk of exposure should be reduced.
  • Reduce Road User Cost. Unknown, but unlikely as this is new technology for implementation.
  • Safety At. this time there are drug needles showing up within the vegetated spaces, catch basin sumps, and stormwater basins in metro regions. If properly managed, the existing risk of exposure should be reduced to both maintenance and public along roadways and curb and gutter systems.
  • Technology. New and emerging technology for floatable waste source controls. Need design criteria, standards, specifications, and detail sheets to implement if warranted.

Technical advisory panel