FREMONT — It will still be a few years before steelhead trout and salmon once again can swim upstream and spawn in the Alameda Creek watershed, but one major barrier to their return has been removed.

Environmentalists and Alameda County Water District officials on Wednesday celebrated the removal of a dam on Alameda Creek in Fremont, and the installation of structures aimed at helping the fish get upstream.

"We see this as continued progress on the road to restoring steelhead trout in Alameda Creek," water district General Manager Walt Wadlow said. "We're not there yet, but we're committed to finishing the work."

Alameda Creek, the largest local watershed flowing into the Bay, once was prime habitat for steelhead trout and, to a lesser extent, salmon, both of which live in the ocean but swim up freshwater streams to spawn.

But a series of barriers installed to collect water for underground aquifers and to protect the streambed as Fremont was developed have blocked the fish from heading upstream.

Steelhead trout were placed on the federal threatened species list in 1997, making it illegal to catch them.

The water district has been working for nearly a decade to make the watershed once again hospitable to trout and salmon.

In 2008, the district installed four fish screens along Alameda Creek just south of Mission Boulevard that keep young steelhead trout from getting pulled into drinking water pools at nearby Quarry Lakes.

Last year, the water district removed a rubber dam that blocked trout farther downstream, adjacent to Quarry Lakes Regional Park. About the same time, the water district installed a fifth fish screen, across from the other four at Bunting Pond, just west of Mission Boulevard near the Niles district. The screens are made of wire mesh that allows water to flow into Quarry Lakes, but keeps out young trout.

There are two major remaining trout barriers in lower Alameda Creek. One is a 12-foot cement structure needed to prevent flooding and scouring of creek channels located adjacent to the Union Pacific Railroad overpass, and the other is a dam just west of Mission Boulevard.

Both structures are too important to the water supply to remove, but water officials hope to construct a series of ponds, known as fish ladders, rising in elevation around the obstacles by 2013.

At the same time, Pacific Gas &Electric is working to modify a cement barrier farther upstream in Sunol to help steelhead swim farther into the watershed, water officials said.

When those projects are completed, steelhead trout will be able to migrate upstream to spawning habitats in the Sunol Valley for the first time in a half-century.

"We're getting to the point where we can actually see that we're going to get some results soon, Alameda Creek Alliance Director Jeff Miller said at Wednesday's event. "All of the pieces are coming together."

Contact Matthew Artz at 510-353-7002. For more Fremont news, read his blog: www.ibabuzz.com/tricitybeat.