Flood Control Zone 3B was formed in the early 1950s to provide funding for construction and maintenance of regional drainage infrastructure in the Walnut Creek watershed. It initially provided, from a portion of the ad valorem property tax, local matching funding for many joint District / Army Corps of Engineers projects extending from the mouth of the creek up to the upstream limits of the City of Walnut Creek.
Consisting of over 22 miles of flood protection improvements, the system consists of parts of:
Clayton Valley Drain
San Ramon Creek
Las Trampas Creek
San Ramon Bypass Channel
At nearly 150 square miles, Flood Control Zone 3B (the Walnut Creek watershed) is the largest in Contra Costa County, and is one of the largest in the Bay Area. The watershed handles drainage for more than 300,000 residents in Concord, Pleasant Hill, Walnut Creek, Alamo, Lafayette, and Danville.
In this watershed, the District has partnered with the Corps on two active projects: