Newark Slough
LaRiviere Marsh
The LaRiviere Marsh lies along the east side of the Refuge between Thornton Avenue and Marshlands Road. It was once a salt crystallization pond that was nearly devoid of life. In the 1980's, it was converted back into a tidal marsh. It is now a thriving habitat with marsh vegetation that provides a home for endangered species. It is crisscrossed with footpaths. The marsh is constantly changing. It changes daily with the rise and fall of tides, which fill and drain the marsh. It changes seasonally, with the marsh plants turning green in the summer and brown in the winter, while the upland grasses on its edges and levees do the opposite. It is a rich vibrant environment, and is a excellent place for observing nature, particularly birds.
South of the Refuge, snow-white hills rise above the Bay. These are not natural formations. They are salt piles at the Newark plant of the Cargill Salt Company. Commercial salt production on San Francisco Bay goes back to the 1850's. There were dozens of small companies making salt around the turn of the century, but salt production eventually consolidated into one company: The Leslie Salt Company. In 1978, the huge 130-year old Midwestern conglomerate, Cargill Inc., purchased the Leslie Salt Company, which gave them ownership of the salt ponds in the Bay Area and in Australia. Many of Cargill's salt ponds lie within the San Francisco Bay National Wildlife Refuge, but the company retains salt-harvesting rights. Cargill is willing to sell the salt ponds and salt-producing rights, so there's a chance the ponds could be converted back to tidal marshland. The LaRiviere Marsh could be a preview of what these salt ponds could look like in the future.
See here for more information on the Refuge.
The LaRiviere Marsh is easily-accessible. It can be seen from Thornton Avenue. Access points are along Marshlands Road. Parking is available at several points along Marshlands Road.
The Refuge visitor center is the southernmost natural area along the Bay Trail route that is accessible to the public in the Alameda Creek-Dumbarton Bridge area. (See here for the Bay Trail map of the area.) The areas to the south along the Bay are either private salt ponds or are parts of the refuge that have no public access. Some are sensitive areas that are closed to public access to protect the wildlife. South of the refuge visitor center, there is a huge gap in the Bay Trail, as far as running on dedicated off-road trails. The route follows city streets for miles through industrial and residential areas, but views of the Bay or sloughs are few and far between. (See the South Bay Bay Trail map.) The next off-road segment of the Bay Trail is more than 10 miles away. It is a short isolated stretch in Fremont along Coyote Creek Lagoon (see map), which is part of the Refuge. From there, it's several more miles to the salt pond levee trails at Alviso. These salt ponds are also part of the Refuge. At Alviso is the Environmental Education Center for the refuge. A new segment of the Bay Trail is under construction in Milpitas along Coyote Creek south of Dixon Landing Road.
The Newark Slough as a natural waterway dead-ends at Thornton Avenue. Across
Thornton is a tamed flood channel running behind the backyards of suburban
homes. A tide gate controls the flow of water from this channel into the
Newark Slough.
This is the Bay Trail route on Thornton Avenue south of the Refuge. Not
much to see scenery-wise from here.
This tour of the Newark Slough Trail will take the trail counter-clockwise
starting at the north bridge over the slough.
The mileage begins at the junction of the Tidelands Trail and the path
to the Newark Slough Learning Center. Take the path to the boardwalk and
bridge over the Newark Slough. The boardwalk, which begins at 0.02 miles,
first crosses over a pickleweed marsh. It parallels a channel leading back
to the pumphouse at the Learning Center.
At 0.06 miles is a dock on the channel near the Newark Slough. This dock
is not accessible to the public. The Newark Slough is a navigable waterway.
You can take a boat, kayak, or canoe on the slough to the Bay. The public
launching ramp is near the park entrance at Thornton Avenue.
The bridge crosses over the Newark Slough at 0.7 miles.
At 0.09 miles, a picnic shelter sits on a pier over the marsh at the edge
of the slough.
At 0.12 miles, you reach the Newark Slough Loop Trail, a wide levee trail
made of dried bay mud. Ahead is a salt pond. It's appearance will vary
depending on the season. (This is a view in March.) To the north, a small
dock extends into the salt pond.
Take the trail loop counter-clockwise to the north. It runs around the
corner of the salt pond. (This is a view looking back towards the slough
bridge in July.)
The Newark Slough runs along the right side of the trail. Broad pickleweed
marshes border the slough.
Pools and channels form in the marshes at high tide. Beyond the slough
is Marshlands Road, Hwy 84, and the Coyote Hills.
On the left side of the trail is the salt pond. This pond is near the end
of the line in the salt-producing process, so the salt concentration here
is very high. Plateaus of crystallized salt appear in the pond. You can
see the Dumbarton Bridge beyond the salt pond.
The pond waters are so salty that only salt-tolerant halophiliic bacteria
can survive in them. The bacteria
turn the waters red.
At 1.05 miles, the trail and the slough turn left away from Hwy 84 and run parallel to the Bay. On the other side of the Newark Slough is another salt pond whose levees are not publicly-accessible.
At 1.32 miles, there's a bench on the trail. Beyond this, the trail curves
to the left as it follows the slough.
This is a view across the salt pond, looking towards the east. The trail
and slough begin to curve to the right at 1.6 miles.
At 1.74 miles is an old pier and shelter on the salt pond.
Across from the shelter on the Newark Slough is a broken and unsafe catwalk
leading to the slough.
At 2.09 is a pipeline crossing. The pipeline runs under the Newark Slough and carries brine between the salt ponds.
The trail approaches the Hetch Hetchy Pipeline. The pipeline dives under
the Newark Slough.
The twin pipelines emerge on the other side of the slough and head across
another marsh towards the Bay.
At 2.28 miles, the trail turns left away from the Newark Slough before
it reaches the Hetch Hetchy pipeline. Behind the pipeline is the swinging
railroad bridge on the now-inactive railroad that used to cross the Bay
south of the Dumbarton Bridge. There is some talk of reactivating this
railroad line for commuter use.
The trail now parallels and runs as straight as the Hetch Hetchy pipeline.
A tidal marsh borders the trail. The pipeline is elevated above it. Pools
and channels fill the marsh.
At 3.0 miles, there's a salt pond levee, which is not accessible.
On the salt ponds, crystallized salt coats the shoreline, looking like
snow.
At 3.32 miles, there's a breached levee in the salt pond on the left. The
Refuge hill can be seen across the salt pond. The white crystallized salt
in the middle of the pond looks like ice floes on a frozen lake.
At the east end of the pond is an industrial area. At 3.63 miles, you pass by some storage tanks on the right. At 3.81 miles, you reach a gate at the corner of the salt pond. There's a pumping station here. A brine pipe crosses the marsh and goes under the Hetch Hetchy pipeline to the salt pond on the other side. Turn left and head down the dirt service road along the east shore of the salt pond.
This is a view looking back west from the southeast corner of the salt
pond.
The service road along the east shore of the salt pond runs ruler-straight.
On the right is a dry field that was once a salt pond. At 3.93 miles,
there's a levee in the dry marsh on the right.
At 4.23 miles, there are several small ponds and an abandoned pumphouse
in one of the ponds. Just ahead, the trail forks.
The trail to the right runs next to these ponds and follows the Newark
Slough, which is on the left of the trail, to its end at Thornton Avenue.
However, there's a locked Cargill gate blocking the trail just before Thornton.
The Newark Slough Trail goes left at the fork. At 4.28 miles, there's a refuge gate. The trail runs straight along the northeast edge of the salt pond.
To the right of the trail is the Newark Slough, which runs through broad
pickleweed marshes on both sides. Beyond the slough is the Refuge hill
and the Tidelands Trail.
At 4.69 miles, the trail turns right as the slough curves around the Refuge
hill. There's a breached levee in the salt pond.
At 4.8 miles, you pass by a fenced-off salt pond levee and a pump station.
At 4.83 miles, there's a small round pond at the end of the salt pond.
This pond is fed from the Newark Slough so the waters are low in salinity
compared to the salt ponds. This small pond is surrounded by salt marsh
vegetation.
At 5.01 miles, you pass the south bridge leading over Newark Slough to
the Tidelands Trail.
Just beyond it is a picnic table and an observation platform on the edge
of the salt pond. The platform has interpretive signs telling about the
history and process of salt pond production on the Bay.
Ahead, you can see the north bridge over the slough.
This is a view looking back along the trail towards the south bridge.
This is a view looking over the Newark Slough at the visitor center on
the hill.
At 5.35 miles, you come to the preserved hunter's cabin on the slough.
There are signs describing the history of hunting in this area.
On the salt pond side is an old hunter's duck blind.
Next to the hunter's cabin is the north bridge on the slough, leading back
to the Tidelands Trail. This is the end of the Newark Slough Loop.
Next to the entry gate to the Refuge is a gate leading to first levee trail
through the LaRiviere Marsh. This levee runs straight between two waterways.
It heads east towards Thornton Avenue. (Picture taken in February.)
These are shallow ponds in the marsh near the entrance to the Refuge. (Picture
taken in September.)
This is the gate to the main trail through the LaRiviere Marsh. No bikes
allowed.
Here is the main trail through the marsh. This is near the bridge over
the marsh's main slough channel.
This is a view down the main marsh trail. Bridges can be seen in the distance.
(Picture taken in February.)
Tide gates control the flow of water through the marsh.
Here is a view of the main slough channel from the Marshlands Road bridge.
This is a view of the marsh from Marshlands Road.
Here is a bridge over the channel feeding the marsh. This is near the southwest
end of the marsh.
Here is a bridge from the main trail through the marsh. Just beyond it
is an old pier that is currently closed.
This bridge is near the north end of the marsh, as seen from the main marsh
trail. It leads to a boardwalk that heads back towards the visitor center.
This is a view from Marshlands Road looking back towards the north bridge
and boardwalk.
Below is a panoramic view of the marsh from the hill above the visitor center. These were taken in September 2000:
This is the north end of the marsh, bordered by Hwy 84 on the north and
Thornton Avenue on the east. Notice the new industrial development on the
east side of Thornton.
This is a view of the center of the marsh. The main trail is along the
bottom. Thornton Avenue is along the top. There is another small marsh
on the east side of Thornton Avenue. This marsh is fed by water from the
Newark Slough. It is also part of the Refuge.
Marshlands Road runs along the edge of the marsh here. There are marshes
on both sides of the road.
This shows the marsh area south of Marshlands Road.
This view shows the marsh's slough flowing into the Newark Slough. The
Newark Slough leads off to the left. The salt pond along the Newark Slough
Trail is on the right and center. The former salt pond is above it below
the industrial buildings.
