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Last Updated: Wednesday, April 13, 2016 9:47 AM

North Coast Studies

map of regional location of the Navarro watershed along California's Norht CoastResearch in stormwater runoff along the North Coast will help Caltrans refine construction and maintenance practices to prevent stormwater pollution

These studies along the North Coast are providing Caltrans with important information about how aquatic life may be affected by stormwater runoff.

Information from these studies will be used to further refine the overall Stormwater Program.

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Does the application of
herbicides to control roadside vegetation affect water quality
and fish reproduction?

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Herbicide Effects on Surface Waters

Are the best management practices currently used by Caltrans adequately protecting nearby waterways from herbicides in highway runoff?

Researcher collects river sediment samples from the Navarro RiverHerbicides in highway runoff are being evaluated at two different sites over a two-year period. Factors that could affect runoff are different precipitation levels, vegetation cover, and slope conditions.

Some of the tasks in this study will serve to...

  • Establish field sites along two rivers near highways
  • Monitor stormwater runoff for the applied herbicides
  • Determine the risk of runoff to nearby surface waters

A model of herbicide runoff will be developed and used to conduct sensitivity analyses for the range of conditions that might create herbicide runoff problems. The model will be used to help Caltrans crews maintain safe spray practices.

Herbicide Effects on Fish Reproduction

fish imageWhat are the potential effects on fish reproduction from exposure to herbicides in highway runoff?

For this study, fish will be used as laboratory models to see how herbicides function in fish. Several chemicals contained in herbicides can have negative effects on fish reproduction by interrupting normal hormone function (endocrine disrupters). Some endocrine disrupters mimic female hormones while others block the activity of these female hormones. These are relatively recent discoveries.

Fish will be exposed to chemicals in the laboratory to see if effects are severe enough to potentially disrupt reproduction. If endocrine fish imagedisruption is suspected, internal organs of the fish will be examined under the microscope for abnormalities.

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How does stormwater runoff from bridges affect water quality, fish, and aquatic habitat in adjacent streams?

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North Coast River Loading Study

What is the contribution of Caltrans land uses on the total pollution load of a typical North Coast river?

water smaples are collected downstream of Caltrans bridgesThe focus of this study is the effect of a variety of land uses, including Caltrans highways and facilities, on water quality and salmonid populations in the Navarro River watershed. Sediment, nutrients, and temperature changes will be studied to determine how these pollutants may adversely affect coho salmon and steelhead trout. Information about water quality gathered from this watershed will be valuable for future TMDL (total maximum daily load) studies along the North Coast. It will also provide a basis for future cooperative efforts between Caltrans and watershed landowners working together to reduce stream pollutants. This study will focus on:

  • Regional partnering and public outreach
  • Geographic Information Systems (GIS) characterization of the Navarro watershed
  • Water quality analysis
  • Pollutant contribution determination
  • Benefit cost analysis

Road Crossings on Small Streams

fish imageHow does stormwater runoff from roads affect streams and aquatic life in the North Coast region?

Bridge crossings over streams can affect aquatic habitat in several ways. Sediment from eroded banks during and after construction and stormwater runoff from bridges can both affect water quality and organisms within the streams. This study conducted in the Navarro watershed will:

  • Identify the sources of pollution to the major streams in the watershed
  • Identify different types of aquatic life within the stream community
  • Determine the availability of habitat for salmon and steelhead
  • Compare the condition of the riparian area to the health of stream communities
  • Investigate the movement of sediment within the stream
  • Analyze stormwater runoff using standard toxicology tests to determine the effects on living organism

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