Editing Dumbarton Bridge (California) (section)

==Environmental factors==
When the current bridge was planned in the 1970s, [[Caltrans]] conducted extensive environmental research on the [[marine biology|aquatic]] and [[landform|terrestrial]] environment. Principal concerns of the public were [[air pollution]] and [[noise pollution]] impacts, particularly in some residential areas of Menlo Park and [[East Palo Alto]]. Studies were conducted to produce contour maps of projected [[Sound exposure level|sound level]]s and [[carbon monoxide]] concentrations throughout the western approaches, for each alternative connection scheme.<ref>C.M. Hogan, Leda Patmore, Harry Seidman et al., ''Air Quality and Acoustics Analysis for the Dumbarton Bridge Replacement Project'', ESL Inc., prepared for the Bay Area Division of Toll Crossings (1973)</ref>

The area around the bridge is an important ecological area, hosting many species of birds, fish and mammals. The [[endangered species]] [[California clapper rail]] is known to be present in the western bridge terminus area.

Near the bridge on the Peninsula are Menlo Park's Bayfront Park, East Palo Alto's Ravenswood Open Space Preserve, and the [[Palo Alto Baylands Nature Preserve]]. An accessible portion of the [[San Francisco Bay National Wildlife]] Refuge lies immediately north of the western bridge terminus, where the Ravenswood trail runs.<ref>''San Francisco Bay Shoreline Guide'', by California State Coastal Conservancy, University of California Press (1995) {{ISBN|0-520-08878-6}}</ref>

On both sides of the east end of the bridge are large salt ponds and [[levee]] trails belonging to the [[Don Edwards San Francisco Bay National Wildlife Refuge]]. The headquarters and visitor center for the refuge is on a hill south of the bridge approach. North of the east end of the bridge is [[Coyote Hills Regional Park]], with its network of trails running over tall hills. North of that is the [[Alameda Creek Regional Trail]] from the Bay to [[Niles Canyon]]. East of [[Coyote Hills (Alameda County)|Coyote Hills]] is [[Ardenwood Historic Farm]], a restored working farm that preserves and displays turn-of-the-century farming methods