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Last Updated: Wednesday, February 7, 2018 10:10 AM

Litter Research Program

litter thrown from vehicles into storm drain systemsLitter thrown from vehicles onto highways can be flushed into the storm drain system via drain inlets and pipe networks. Litter in waterways degrades our water quality, wildlife habitat, and the recreational enjoyment of rivers, bays, and beaches.

Caltrans is taking action with litter research to find safe and cost-effective solutions for reducing highway litter in stormwater.

Completed Studies:

  • Litter Management Pilot Study (LMPS) – a three-year study to identify sources and types of highway litter, and whether BMP devices were effective in reducing litter.
  • Solids Transport and Deposition Study (STDS) – showed the rates and patterns of how solid materials (including litter) deposit into storm drains inlets.
  • Litter Inlet Deflector Study (LIDS)Litter Inlet Deflector Study (LIDS) – testing an innovative drain inlet device designed by Caltrans to keep litter out of inlets while letting stormwater in.

Ongoing Studies

  • Drain Inlet Cleaning Efficacy Study (DICE) –- testing how effective cleaning drain inlets can be in managing litter and improving stormwater quality.
  • First-Flush Study – determining at what stage of the storm intensity the largest litter load occurs.
  • Public Education Study – looking at the effects of public education on reducing litter in storm drains.
  • Gross Solids Removal Device Study (GSRDS) – testing small BMP devices for Caltrans facilities (storm drain outfalls) where little space is available.

Future Directions

Future litter research will focus on: fitting stormwater control devices into the limited space around Caltrans facilities; increasing worker safety during roadway maintenance and decreasing maintenance time and frequency; increasing the cost-effectiveness of treating stormwater with control devices.

Public Outreach

Caltrans sponsors workshops and provides written materials and Internet websites on litter to discuss and share the latest developments in stormwater management.

How is Litter Research Done?

Gross solids, consisting of both litter and vegetative material, are collected from highway storm drains. Weight and volume measurements of the gross solids are taken in the field after collection. Research protocols define the monitoring procedures to provide sound scientific data (e.g., how and when litter should be collected). This innovative research will provide a sound basis for managing litter in stormwater.

litter removal device
Litter that passes through the storm drain is captured in a litter removal device.

a variety of devices are being tested as Best Management Practices (BMPs) for reducing highway litter in stormwater
A variety of devices are being tested as Best Management Practices (BMPs) for reducing highway litter in stormwater.

To view reports on this subject CLICK HERE


Division of Environmental Analysis, Stormwater Unit
California Department of Transportation
P.O. Box 942874, MS-27
Sacramento, CA 94274-0001
Email: Division of Environmental Analysis, Stormwater Unit