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


image of Caltrans employees monitoring stormwater in inlet drainCaltrans manages California's highways and related facilities in a state with a wide diversity of terrain, climate, and ecological conditions.

The challenge of reducing stormwater pollution with such a wide range of variables begins with stormwater monitoring. Water quality data from monitoring responds to the National Pollutant Discharge Elimination System (NPDES) permit requirements. Data from monitoring projects also guides the evolution of the Caltrans Stormwater Managment Plan (SWMP), which addresses stormwater needs for facilities throughout the state.

Monitoring stormwater is a Statewide Effort

Since 1997, Statewide Characterization Studies have been performed at Caltrans facilities in various settings — urban and rural, different ecological and hydrological regions, and all Caltrans districts. The Caltrans facilities monitored include:

  • Highways (urban and rural)
  • Maintenance yards
  • Park and ride lots, rest areas, weigh stations
  • Construction sites

Constituents Monitored

Constituents monitored for these facility-based studies could vary depending on the facility but generally include:

  • Conventional water quality parameters (pH, conductivity, suspended and dissolved solids, hardness, and total and dissolved carbon)
  • Nutrients (nitrogen and phosphorous compounds)
  • Total and dissolved metals (arsenic, cadmium,chromium, copper, lead, nickel, and zinc)

Monitoring in Special Settings

To learn about stormwater quality in specific settings, numerous Specialized Characterization Studies are also underway. These include:

  • Effects of highway congestion on stormwater runoff quality
  • Detection methods for low concentrations of metals
  • Effectiveness of drain inlet cleaning
  • Changes in pollutant concentrations throughout a rainstorm (first flush)
  • Residues from herbicide use along highways
  • Urban litter in stormwater
  • North Coast River pollutant loading
  • Methods for detecting pathogens
  • Highway impacts on small streams
  • Stormwater toxicity

Caltrans Monitoring Sites for 2002-2003

Monitoring: a Step-By-Step Process

In selecting a monitoring site, criteria must be met for the type of facility or hydrologic condition, personnel safety, site access, equipment security, flow measurement capability, and electrical and telephone access. The next steps in the monitoring process are to:

  • Prepare sampling and analysis plans
  • Install monitoring stations
  • Collect runoff samples
  • Analyze for constituents
  • Validate data and add to database
  • Use data to characterize runoff quality and compare constituents detected at different sites
  • Put findings in statewide characterization annual report (required by NPDES permit)
  • Use results to refine the Stormwater Management Plan (SWMP) – the guiding document for the Caltrans stormwater program

image of employee looking at computer monitorProtocols for Monitoring and Reporting

  • Monitoring Methods. At each monitoring site, samples are either taken by hand (grab samples) or by automated samplers.
  • Guidance Manual. The Caltrans Stormwater Monitoring Protocols: Guidance Manual is a how-to manual that gives a consistent framework for all monitoring available online.
  • Data Reporting and Analysis. All monitoring teams collecting data use reporting protocols to maintain data consistency for the Caltrans database. Data are analyzed with specialized software and tools.

Stormwater professionals can find more information on water quality, monitoring sites, stormwater data, and calculating stormwater volumes at:

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