The peninsula of Foster City is a planned community of nearly 30,000 that was built in the 1960's on the hayfields of former Brewer's Island. At the turn of the century, levees were built around mud flats here, which were dried and turned into farmland. Marina Lagoon, a now-tamed slough which used to empty into San Francisco Bay, borders Foster City to the west. The two lagoons are used for water recreation and stormwater runoff control.
Pumps control the levels of the lagoons and herbicides are used to control vegetation.
The Bay tides dramatically affect the level and appearance of the slough. The waters of San Francisco Bay itself wash the city's northeast to northern shores. Hwy 92 cuts diagonally through the city and leads to the San Mateo-Hayward Bridge. The outer edges of the city along Belmont Slough and San Francisco Bay are protected undeveloped marshland or bayfront, with public access. This is where the Bay Trail runs.