Tour of Tule Ponds at Tyson Lagoon  

STATION 1.  Oil and Solid Traps

Concentrations of sediments, chemicals, and garbage change during a storm event.  The early part of a storm transports the largest amount of larger particles whereas the later stages of storms have a higher percentage of dissolved hydrocarbons and dissolved metals.  The velocity of the water also slows as stormwater enters the Tule Pond system.  This allows heavy particles to drop out of the system first. 

Ponds B and C use logs to help retard the flow of objects that float, like oil and garbage.  You can notice that the constriction between the ponds help to narrow the flow preventing these lighter objects to continue.  The removal of garbage will insure that Tyson Lagoon will not have any objects that could harm the wildlife. 


STATION 2.  Siltation Pond

Pond A is designed to slow the flow of  water to allow suspended particles to drop out of the water column.  This helps increase the water quality of the water to become less of a potential hazard later in the San Francisco Bay.  The suspended particles range from heavy metals, such as copper (Cu), lead (Pb) and zinc (Zn), to simple particles  like sediment and soil.  Heavy metals in large quantities can cause fish deaths and algal blooms.  The particles increase turbidity and can prevent the penetration of sunlight to phytoplankton.  Increased nutrients from fertilizers can cause an increase of water plants which can reduce the necessary amounts of nutrients to fish and other water organisms.  Motor oil can coat fish gills , preventing the fish to used dissolved oxygen in the water and it can coat bird wings, making flight difficult.    Lead can come from paints, wood staining products , and emissions from diesel and gasoline  operated vehicles.  Zinc can come from automobile tires, paints, and wood staining products.  Copper is from plumbing, electroplating processing wasters, brake pads in automobiles, and algaecides.   In high dosages these substances can be hazardous to organisms that live or frequent the ponds.

STATON 3.  Stormwater Inflow

Residential and urban growth in a watershed increases water runoff.  When you construct a home, industry or road, water is prevented from percolating downwards into the ground.  If you look at the beginning of  Pond A you will see a large pipe.  This water comes from a series of storm drains connected by pipes underground. 

Water seeks sea level, so drainage in a watershed is determined by topography.  Drainage in the Tule Pond is restricted to a watershed that includes the surrounding area.  Runoff occurs when the zone of aeration (where plants take up  water) is saturated and when excess water cannot flow into the ground.  Runoff contains suspended particles such as silt as well as dissolved substances.  Some of the particles are natural, from erosion caused by weathering of the nearby hills.  However some substances are added by humans,  including heavy metals, garbage, and dissolved chemicals.

STATION 4.  Cattails and Tules

Water quality is frequently enhanced as water passes through wetland.  Plants help to slow the flow of surface run off and cause sediment to settle out.  Living plants like algae and large emergent plants like tules and cattails, add dissolved oxygen to water during photosynthesis.   Wetland plants support much of the life in open water, and plants like cattails and tules provide shelter for larger animals of the pond.

Wetlands have characteristic vegetation that can tolerate being submerged in water.   The type of plants a wetland can support do not require an elaborate way of capturing water like trees.  Certain plants in these vegetated waterways are effective in removing metals from storm water.  Metals accumulate near outflow and not transported very far downstream with the exception of zinc because zinc stays in dissolved form. 

STATION 5.  Butterfly Meadow

Even butterflies can go extinct and are part of the overall health of an ecosystem.  Loss of habitat is a major threat to butterflies as open meadows turn into residential areas. Butterflies are beautiful but they are important pollinators of many plants.  They also provide a food source for many birds, mammals, reptiles and even other insects. 

This butterfly meadow will not only help repopulate native butterflies but will be a home of many native plants that serve as a food source  for the caterpillars that will change into a  chrysalis before the butterfly emerges.


STATION 6.Organisms of Tyson Lagoon

Wetlands are among the most productive ecosystems in the world.  A fresh water marsh is as productive as a tropical rain forest.  Wetland plants are specialized because they can withstand water levels that most land plants cannot.  Bacteria, protozoa, and fungi are bountiful as decomposition of organic matter releases nutrients.  These microscopic critters are eaten by larger invertebrates like arthropods and mollusks, who are eaten by amphibians, reptiles and fish. 

The top of the food web includes birds and mammals.  Tyson Lagoon is resident to many birds who find this area as a haven.  Many build their nests and feast on the abundant food source throughout the year. 


The Tule Ponds at Tyson Lagoon is a unique opportunity to see how the needs of humans in an urban setting and other organisms can mutually co-exist.   Before humans arrived in what is now Fremont, many organisms like birds, insects, and fish inhabited the area.  As an area become urbanized (becomes populated with people and their buildings) the natural order of things start to change.

Prior to urbanization, water would soak into the ground and slowly percolate into the layers of the soil and bedrock.   If there were more rain than what the earth could handle, then the water would “run off” causing floods.  These flood waters brought nutrients from the nearby hills, and the plants especially benefited.   As people build homes and laid down asphalt and cement for cars to use, water flows more quickly.  They usually build homes in the flat area of what is referred to as a flood plain.  The rains now caused flooding and damage to many homes.  To prevent floods engineers developed ways to allow the water to flow quickly through man-made channels that would bring water to the San Francisco Bay edge.  It works, but it also causes valuable lost of habitat for the other creatures. 

The Tule Ponds at Tyson Lagoon acts as a flood area on its way out to the bay.  After it leaves the lagoon it goes through earth or concrete lined channels out to the bay.  This area acts to help prevent floods, but it also acts as a natural place for organisms to thrive.

These wetlands also help to remove substances that enter the system from residential, urban, and agricultural runoff.  Some of these substances are considered pollutants and may be toxic to different types of organisms. Residential and urban runoff  in this area would include garbage, pesticides, oil and grease, organic matter, and heavy metals.  Agricultural runoff from nearby small farms would include pesticides and nutrients.  The frequency of these substances is intermittent dependant on winter rains. 

As you walk through the trails you will learn how water is being cleaned before it enters the San Francisco Bay and how it is used to increase habitat for other organisms.  Stormwater enters through a large pipe into Pond A, and then flows into Ponds B and C.  Water then flows into Tyson Lagoon.  When the water reaches a certain level, it flows into the outlet toward Mowry Ave.

Each of the 6 stations highlights a function of the entire ecosystem.  After you go through the different stations you may want to return to the different stations to learn  more about this unique area.

WARNING:  Please remember to keep on the trails and don’t disturb the wildlife.   Throwing rocks is not permitted and chasing wildlife is prohibited.