Coastal Watershed Restoration

Point Reyes National Seashore, CA

National Park Service, PORE
2007 - 2008

In 2007, through a proposal process, Hanford ARC was awarded the Coastal Watershed Restoration project at Point Reyes National Seashore.  This project is a two-year comprehensive watershed restoration, spanning multiple watersheds in the park.  Upon completion, the project will re-open approximately 20 miles of spawning habitat for salmon and steelhead.  The scope includes culvert removal, bridge construction, stream channel reconstruction, tidal wetland restoration, dam removal and public access improvements.   

Prior to the federal government’s acquisition of the park property in the 1960’s, development was attempted in numerous locations, including dam building, road grading, and infrastructure construction.  Unfortunately, and although never finished, the development heavily impacted the watersheds within the park, including impedance of fish passage.

Hanford ARC completed the first phase of this project in 2007, which included five distinct work sites: Mt. Vision Road bridge, Estero Road bridge, Home Ranch bridge, Glenbrook channel restoration, and Limantour Beach RLF ponds.  The 2008 phase will include three sites: Muddy Hollow dam removal, Limantour pedestrian bridge, and Upper Laguna fish ramp.  The latter sites will not be addressed in this description.

Both Estero Road and Mount Vision Road intersect with Sir Francis Drake Boulevard in the northern portion of the park, approximately ½ mile apart.  At each intersection, the roads cross Schooner Creek.  This is a perennial stream with spawning habitat.  Each crossing had been historically culverted, and the culverts impeded fish passage.  A similar remedy at each site involved culvert and road section removal, and replacement with a precast concrete arch culvert, essentially a bridge, which would allow a natural stream bed to form.  At each site we graded and stabilized the upstream and downstream segments of channel to create a passable series of riffles and pools.

Because of the sensitive nature of the work environment, Hanford ARC performed all site work in-house, including dewatering, concrete footing construction, channel grading, rock structures, and erosion control.  We hired Precision Crane Service to rig and set the bridges.  Both sites require a 24-hour pump bypass system.  We worked under full time supervision by a NPS biologist, and coordinated with the park to relocate a number of species found in the active work area.  Both sites were re-opened to natural channel flow in October of 2007, and were replanted by the park.

Glenbrook Channel Restoration

Part of the historic Estero Road crosses Glenbrook, between Home Ranch and Limantour Road.  This portion of the road is now in designated wilderness, and had become part of the trail system in the park.  Prior to the park establishment, the road had been widened and raised.  It eventually functioned as a dam, trapping sediment upstream, and scouring deeply downstream, which had created a 15-20 foot drop in the channel at the road crossing.  This condition completely eliminated fish passage upstream of the road crossing.

The scope of work at Glenbrook included excavation of the culvert and removal of the road and the crossing, raising the channel for approximately 800’ downstream to tie into the existing channel bed, and excavation of approximately 100’ of channel upstream.  The work also included seven large woody debris jams.  The intent of the design is to provide a start for the channel to return to its natural state, which would allow for natural erosion to lower the basin upstream of the crossing, which in-turn would recruit sediment for the downstream section of channel.

The work at Glenbrook presented several interesting challenges.  First, a minimum tool requirement applies in designated wilderness.  We carefully considered what equipment was imported to the site, and made every effort to minimize our footprint.  This included the use of primarily tracked equipment such as a tracked truck to transport soil throughout the site, and tracked loaders to move logs.

Second, after excavating the first culvert, we found a second, lower culvert underneath, which had been abandoned.  This required excavation, and exposed deep saturated soil in the crossing.  Still higher than the pre-crossing channel bed, we opted to continue to excavate the channel banks and follow the invert of the second culvert for the longitudinal section.

Lastly, several channels entered the project from the site, which potentially threatened the stability of the fill placed downstream of the crossing.  For these, we attempted to work with the channels as features, by creating small impoundments for RLF habitat and swales to return the water to the new primary channel.  Following the plans as a guide, Hanford worked with the NPS to field fit the design.

Dramatic changes occurred following several storms during the winter of 2007/2008.  These included substantial downcutting upstream of the crossing and deposition in the downstream reaches.  Although anticipated by the park, the rate of change is much quicker than expected.  This site will be very interesting to follow the next 2-3 years.

Home Ranch Culvert

Home Ranch is along the Estero Road between Glenbrook and the Estero Road crossing (both already discussed), and is one of the most historic areas of the park.   A stream runs immediately adjacent to the farm house, between the house and a barn.  A culvert had been installed, but was under-sized, and resulted in flooding in the house, barn and other outbuildings.  Our scope included removal of the old culvert, placement of a precast open-bottom concrete box culvert and sediment dredging.  We also added a berm between the house and channel to minimize flooding.

The precast structure is similar to the bridges at Mt. Vision/Estero Roads, with regards to footings, wing walls and installation.  The difference is a thicker, level bridge deck, allowing the deck to function as the road with no additional cover.  The primary challenges of this site were the extremely tight work area, adjacent to historic structures, and dewatering the footing subgrade. 

Limantour Beach Frog Ponds

The 2008 work under this contract will convert freshwater wetland to tidal marsh at Limantour Beach.  Although the restoration work will increase the valuable tidal marsh area as well as open Muddy Hollow Creek for spawning habitat, it will impact an existing red legged frog population by reducing freshwater wetland habitat.  In order to mitigate for this impact, the 2007 project phase included construction of three red legged frog ponds.

We transported the soil excavated from the ponds to a common disposal site that will be used for disposal of spoils from the Muddy Hollow Dam Removal and Limantour tidal barrier removal.  Throughout the construction process, Hanford ARC worked to minimize the construction footprint, as well as consider aesthetics to the public in a highly visited area.

All five work sites described here were completed in 2007.  Hanford ARC will re-mobilize for the three 2008 work areas.