Calaveras River / Caprini Low Flow Road Crossing

The project is located on Mormon Slough, 13 miles upstream of the confluence of the Calaveras River with the San Joaquin River, in San Joaquin County. The original crossing was built in the 1920s and consisted of a perched concrete road structure that contained 3 undersized corrugated metal culverts.


Is this an Active Project or Completed Project? Completed

Watershed: Calaveras River

Why is the project needed? What are the project goals?

The crossing was identified in the Calaveras River Fish Migration Barriers Assessment Report as a temporal barrier to adult and juvenile Chinook salmon and steelhead. Hydraulic modeling determined that fish passage criteria for adult Chinook salmon and steelhead was not met until flows were 730 cubic feet per second (cfs), about 1 to 10 percent of the time during their migration. It was 1 of 4 high priority barriers identified by a collaborative interagency process, based on impacts to federally threatened California Central Valley steelhead and fall-run Chinook salmon.

Our engineers completed the design and hydraulic modeling for the project. The design uses 3 sets of 10-feet-high by 12-feet-wide box culverts to span the active channel, creating a much improved crossing which has a natural substrate and a more gradual gradient to allow fish to navigate through the site easily.

Benefits of the new structure include:

  • Improved capacity of the culverts
  • Lowered water surface elevations at high flows
  • Reduced turbulence and erosion
  • Improved fish passage


The project was completed in October 2013.


Our funding was provided by Proposition 50 and Proposition 84.


The project was a collaborative effort in partnership with the Caprini family, Stockton East Water District, the U.S. Fish and Wildlife Service, and the California Department of Fish and Wildlife.

The improved structure is used by the landowner as a road crossing and by San Joaquin County for flood maintenance activities.