Alviso: Mallard Slough & Environmental Education Center

Environmental Education Center across New Chicago Marsh
Mallard Slough Trail
Environmental Education Center and New Chicago Marsh


The Mallard Slough Trail Loop is the second of the two major trail loops in the Alviso Area. It lies to the east of the larger Alviso Slough Trail Loop, which is covered on a separate page. It follows Mallard Slough, also known as Artesian Slough, to its junction with the Coyote River, then follows the Coyote River west. Both trails run on either side of the Southern Pacific Railroad tracks, which lead south to Alviso. The trail leads east along New Chicago Marsh, then meets Mallard Slough again.

The Mallard Slough Trail is a public trail, but is not officially part of the Bay Trail. It is less used, and access is more restricted than the Alviso Slough Trail.  The northern part of the Mallard Slough Trail Loop is closed during the winter to normal trail users in order to allow waterfowl hunting. The area around Mallard Slough itself is closed from March 1 to August 31 to protect nesting herons. In 1999, the northern parts of the trail were unusable due to the rough trail surface.

The Mallard Slough Trail runs next to the San Francisco Bay National Wildlife Refuge Environmental Education Center (EEC), run by the US Fish and Wildlife Service.  The center is primarily used for school field trips during the week. During the weekends, it is open to the public from 10 am to 5 pm. The center has a large parking lot. The gate closes at 5, so be careful not to get locked in. The center is a large multi-story wooden building sitting at the edge of New Chicago Marsh. The marsh was named after a failed housing development scheme that was supposed to be built on the lands covered by the marsh. The EEC has classrooms, maps, educational displays, and an enclosed observation tower on the top floor. Rangers are there to answer questions. There are picnic tables, benches, and an observation deck outside. Next to the center is a butterfly garden. Below the center is a 1200-foot long boardwalk that runs through New Chicago Marsh. Just east of the center is reed-lined Mallard Slough.

Alviso may seem like a ghost town in some places, but nearby is a real ghost town, the former town of Drawbridge.  It is located on small Station Island in the South Bay, about 3 miles north of Alviso, between the Coyote River and Mud Slough. Starting in the late 1870's, people started coming here for fishing and hunting. They built houses here on stilts near the railroad tracks. It eventually developed into a community of 400. The community declined as sewage and pollution from the developing South Bay cities ruined the habitat. Eventually, the town was abandoned. Now it is a ghost town.  It is closed to the public except for docent-guided tours. For information on tours, contact the San Francisco Bay National Wildlife Refuge in Fremont at (510) 792-0222. The buildings of Drawbridge can be seen above the marshlands from the Alviso trails along the Coyote River. The northwest corner of the north Mallard Slough Trail provides the closest view.

Access Information

The Mallard Slough Trail Loop can be accessed from two points. One of them is at the railroad crossing on the Alviso Slough Loop Trail. The shortest way to reach the crossing is to take the east side Alviso Slough Trail Loop north from the Alviso Marina. The crossing is 1.7 miles north from the trailhead at the Marina. Going the long way, clockwise around the Alviso Slough Trail Loop, the railroad crossing is 7.1 miles from the trailhead.

The other way to access the trail, and the easiest for walkers, is from the EEC. See the directions for getting to the Alviso Slough Trail. The EEC is located at the end of Grand Blvd. in Alviso. From the west, get to Gold Street, then turn right on Taylor Street. Take Taylor to Grand, then turn left on Grand. Grand crosses Spreckels and Los Esteros. Straight ahead is a gate. If the gate is open, continue on the road to the EEC. Be sure to leave before closing hours to avoid getting locked inside. From the East Bay, the EEC can be reached by taking Hwy 237 to Zanker Road. Where Zanker Road meets Grand Blvd., make a sharp right turn into the EEC entrance road. See this map. The Mallard Slough Trail runs on the levee just north of the EEC.

Click on the following pictures to see a larger version Hold your cursor over the pictures to read the captions. Note that the mileage readings below were taken from a bicycle odometer. Your mileage may vary.

The Mallard Slough Trail:

The Mallard Slough Trail runs around a large salt pond, which is actually 2 ponds with a connecting channel in the middle. A narrow finger of marsh extends in from the west side and divides the pond in two, separating it into a northern and southern portion. The descriptions below describe the trail conditions in September of 1999, when the trail around the northern part of the pond was very rough and virtually impassable in the section along Mallard Slough. The Cargill Salt Company maintains the levee trails. Mud dredged from the Bay or salt ponds is heaped on top of the levees to maintain them. It takes several years for the mud to dry. As it dries, it becomes cracked and uneven. When it is dry enough, the surface needs to be graded and smoothed to allow for easy travel on it. By September 1999, this had not been done to the northern half of the trail. The southern section of the trail is smoother and more heavily traveled immediately adjacent to the Environmental Education Center. Before venturing out here, check with the EEC on the condition and accessibility of the trails.

South Mallard Slough Trail:

This trail begins across the railroad tracks from the Alviso Slough Trail Loop. The main reason to take this trail segment is to reach the Environmental Education Center from the Alviso Slough Trail. It also reaches Mallard Slough and the Alviso Heronry.

Mallard Slough Trail heading south, with train to west, pier on salt pond to east Turn right after the railroad tracks. The mileage readings start here. The trail is on the levee separating the salt pond to the east from the marsh and railroad tracks to the west. The trail surface is softer and bumpier than on the Alviso Slough Loop, but it is firm enough to be used even by road bikes. At 0.3 miles, a gate lets water flow in from the salt pond to the west. At 0.5 miles is a small wooden pier on the salt pond to the east.

Southwest section of Mallard Slough Trail, heading towards EEC At 1.0 miles, the trail makes a 90 degree turn to the left. The levee divides the salt pond from New Chicago Marsh.

Birds on island in salt pond Small islands in the salt pond, which were put there by the San Francisco Bay Bird Observatory, provide a safe haven for waterfowl. One such island is near the trail at 1.3 miles.

EEC from Mallard Slough Trail The Environmental Education Center soon comes into view. At 1.8 miles is the end of the boardwalk that leads over New Chicago Marsh.

At 1.9 miles is a gravel road that leads from the trail to the paved road leading to the EEC's parking lot. (This can be used as an exit from the trail. The paved road leads to Grand Blvd. Surface streets can be used to return to the Alviso Marina, a total distance of 4.3 miles.)

Continuing on the Mallard Slough Trail, the trail turns towards the north as it follows Mallard Slough. Mallard Slough is used for freshwater discharge from the huge San Jose/Santa Clara Water Pollution Control Plant. The freshwater has affected the environment, turning former salt marshes into brackish and freshwater marshes. This has benefited some species, but hurt others, like the endangered clapper rail and salt marsh harvest mouse. Water recycling efforts are taking place to reduce the amount of freshwater discharge. The pond across the slough is off-limits. The smell of chlorine wafts through the area from the water treatment process. The water treatment plant's facilities and drying ponds occupy a large area to the east of Alviso.

Dock on Mallard Slough At 1.0 miles is a boat dock on the slough.

Heron rookery in marsh by Mallard Slough, next to salt pond At 1.2 miles is a sign indicating that the area is closed from March 1 to August 31 to protect nesting herons and egrets. The marsh that begins here is known as the Alviso Heronry. The trail begins to curve away from Mallard Slough, and a bulrush-covered marsh begins to widen out. The trail takes a curving path around this marsh.

Channel joining salt ponds on east side of Mallard Slough Trail At 2.1 miles, the trail reaches the narrow channel joining the two salt ponds. The trail on the west side can be easily seen across the channel. In past years, the salt company had a wooden bridge over the channel. This was not there in 1999. The trail from this point north was rough and virtually impassable.

North Mallard Slough Trail:

This trail segment provides the closest views available, without being on a guided tour, of the ghost town of Drawbridge. This section is recommended for foot travel or mountain bikes only. The surface is too soft for road bikes. This segment of the trail begins at the railroad crossing from the Alviso Slough Loop Trail as above. Turn left after reaching the salt pond levee. A sign here indicates that the trail is closed from October to January to allow duck hunting. The mileage readings begin here.

Mallard Slough Trail start, northwest side The levee is wide, but the surface is somewhat soft. It heads southeast along the right side of a narrow finger of marsh.

Northwest shore of south salt pond on Mallard Slough Trail To the left of the marsh is the large southern salt pond. The trail runs straight along the edge of the pond.

Channel between salt ponds on Mallard Slough Trail At 0.5 miles, it reaches the end of the marsh. Here is a narrow channel that joins the two salt ponds. The east side of the Mallard Slough Loop Trail is across the channel.

Mallard Slough trail north of finger marsh The trail  and makes a U-turn around the edge of the narrow marsh and heads back in the opposite direction. The marsh is now on the left, and the northern salt pond is on the right. The trail here is much softer and lesser-used.

Boardwalk to railroad tracks from northwest Mallard Slough trail At 1.0 miles, the trail turns to the north, paralleling the railroad tracks, which are in the middle of a narrow marsh. A short wooden boardwalk leads out to the railroad tracks. The trail here is even softer and bumpier than before. Bicycling becomes more difficult.

Coyote Creek Bridge and ghost town of Drawbridge from Mallard Slough Trail Finally, after 1.4 miles, the trail reaches the banks of the Coyote River. The railroad crosses the creek on a bridge. On the other side of the Coyote River is Station Island. Unauthorized access to the island is prohibited and can result in a fine.

Drawbridge buildings across Coyote Creek Across the creek, several old, decaying wooden buildings can be seen, barely rising above the marsh. These are the remnants of the ghost town of Drawbridge.

Looking up Coyote Creek from Mallard Slough Trail From here, the trail turns right and heads up the Coyote River. It eventually reaches the mouth of Mallard Slough, where it drains into the Coyote River. It then heads south down along the banks of Mallard Slough to the channel joining the two salt ponds. However, the trail from here on becomes increasingly rough, eventually becoming unrideable by bicycle and hazardous for foot travel. Further travel along this route is not recommended until the trail conditions improve.

The Environmental Education Center and New Chicago Marsh:

Town of Alviso looking across New Chicago Marsh The road to the EEC passes by the side of New Chicago Marsh,. The town of Alviso can be seen along the west edge of the marsh.

Environmental Education Center building The striking wooden building housing the EEC can be seen at the northeast corner of the marsh. The EEC is located on an upland area above the marsh. Picnic tables and benches are provided around the outside of the center.

Displays in Environmental Education Center Inside the EEC are a number of displays. Here are some on the Chumash Indians, who used to live in the area, and the birds that can be found here.

Hummingbird garden at EEC Next to the EEC is an upland garden with native plants. Flowers in the garden attract hummingbirds.

New Chicago Marsh Boardwalk The view from the observation tower in the EEC provides panoramic views of the area. Here is a view of the boardwalk across New Chicago Marsh. The boardwalk starts at back of the EEC and runs over the marsh.

New Chicago Marsh, looking towards Mallard Slough from EEC tower The boardwalk crosses a slough on a bridge and ends at a salt pond levee, along which runs the Mallard Slough Loop Trail.

For more on the Alviso Area, see the "Alviso: Town and Slough" page.

Developed: 12/29/99 by Ronald Horii

Information and opinions here are the responsibility of the author