Giacomini Wetland Restoration

Point Reyes National Seashore, CA

Point Reyes National Seashore Association, Point Reyes National Seashore
2008

In 2008 Hanford ARC was awarded the second phase of the Giacomini Wetland Restoration Project.  10 years in planning, the completed Giacomini project restored 12% of California’s outer coastal wetlands and 50% of Tomales Bay wetlands.  The Giacomini Dairy leveed a tidal zone of lower Lagunitas Creek in the 1940’s to reclaim the land for cattle grazing.  The Dairy drained the land through a series of ditches and filled portions of Tomasini Creek, a tributary to Lagunitas Creek.  In 2000 the National Park Service acquired the Waldo Giacomini Ranch.

The first phase of the project was completed in 2007, and included demolition of the dairy infrastructure and red-legged frog mitigation wetlands.  The second phase, constructed by Hanford ARC consisted of removal of approximately 3 miles of levees, construction of new tidal channels including the 50’ wide lower Tomasini Creek, backfilling drainage ditches, removal of dairy infrastructure, and construction of marshplain and floodplain benches.  Although at the start of the project the work area was leveed, most of the 550 acre project area, spanning both sides of Lagunitas Creek (east and west pastures), was delineated jurisdictional wetland.

Construction presented major logistical challenges.  The total earth moved was approximately 125,000 CY.  Because of the soft substrate, and sensitive nature of the site, scrapers were not an option.  In addition, for at least ¼ of the project area, wheeled equipment was not an option.  This limited our choices of equipment to primarily tracked.  We did use off-road haul trucks on designated routes to move levee soil to the dairy ‘mesa’, both a disposal and transfer site.  We hauled approximately 22,000 CY to two quarries within the park which we closed with the soil.

Certain areas of the project were so soft that we used low ground pressure (LGP) tracked equipment to perform all work.  This included excavating and transporting approximately 3,000 CY of sediment from lower Tomasini Creek using an LGP excavator and LGP tracked trucks.  Other specialty equipment included a long-reach excavator and LGP bulldozer.  Where LGP equipment did not have the capacity to meet the required production, we built and maintained temporary roads over existing ranch roads to handle regular off-road truck trips.  As we completed zones of the project, we removed the temporary roads, as well as the ranch road underneath, and ripped the soil for decompaction.

Scheduling was very complicated.  The primary schedule drivers were permit conditions and tides.  Aside from jurisdictional wetland status, the ditches contained tidewater goby, a federally endangered species, the uplands were potential black rail nesting habitat, a state threatened species, and Lagunitas Creek contains coho salmon and steelhead, both federally endangered.  These species all require specific timeframes to minimize disruption to natural processes such as nesting, migrating and spawning.  Our work areas were divided by zones to accommodate the biological restrictions.

We worked closely with the National Park service to clear areas prior to construction activities within the areas.  This included carefully paced clearing in potential nesting areas, proceeded by a biological sweep, and careful dewatering of drainage ditches.  We assisted the park with setup of fyke nets to screen for tidewater goby, and adjusted dewatering operations as necessary to facility proper flows for screening.

Tidal influence was a substantial factor throughout the project, but especially near the end.  Because most of the project area would be diurnally flooded after the levees were removed, we could not completely remove the levees until the work on both pastures, including channel and marshplain grading was complete.

In order to manage the remaining levee soil without transport, we constructed temporary berms along Lagunitas Creek, with an inboard trench or low area with the capacity to receive the soil.  This proved effective.  We were able to perform the final breach of the levees in one day for each pasture.

The restoration design incorporated  habitat enhancement details such as high tide rail (waterfowl) refugia and water retention segments within tidal channels (goby habitat), and floodplain basins on upper Tomasini Creek (red-legged frog habitat).  The design also included specific hydrologic features such as a ‘high flow bypass’ and 16 acre marshplain enhancement area to encourage Lagunitas Creek to reconnect to its historic floodplain.

Beyond the primary project area, the NPS incorporated two additional project areas.  One, mentioned already, is located on two ranches between Sir Frances Drake Blvd and Pierce Point Road to the west of Inverness.  The park utilized fill generated from the Giacomini project to close and restore two quarries on these ranches. 

As part of our contract, we transported, placed and compacted the soil in the quarries, and provided erosion control.  The second work area was located at Olema Marsh, just south of the Giacomini project.  The work at this site included reconnection of an existing freshwater marsh to Olema Creek.  The work required LGP equipment.  The intent at this site is to restore a more natural hydrology to Olema Marsh.

The Giacomini Wetland Restoration project has since received notable attention, including newspaper articles in the Los Angeles Times, Marin Independent Journal and Press Democrat.