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Park Street Bridge
Miller-Sweeny Bridge
Fruitvale Ave Bridge

High Street Bridge
Bay Farm Island Bridge
Bay Farm Island Bike Bridge

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Many draw bridges in the world are classified as Bascule.  A Bascule type draw bridge is balanced so that when one end is lowered the other end is raised.  For example, the leaf of a draw bridge is usually made of steel and concrete with considerable weight.  To counteract the bridge weight a counterweight is installed usually at the end of the leaf to give it balance.  It would take a tremendous amount of power to raise a bascule bridge without the counterweight.  A 75 hp is all that's required to raise the Park Street Bridge using full power.  The emergency drive motor is only 5hp and will also raise the bridge with no problems just slowly.

Bridge Height Restriction
Park and High Street Bridge have an overhead steel superstructure that limits vehicles with certain heights.  Many vehicles, mostly large trucks have hit the bridges causing damage to the bridge and their own vehicles.  It's advised to check with the bridge tender to make sure you can clear the bridge superstructure or see the height restriction data located on these pages.  Miller- Sweeney Bridge has no height restriction when in doubt.

Bureau of Electricity
The City of Alameda operates it's own power supply company.   It buys power from various sources and then distributes power to the businesses and residents of the city.

Mean Higher High Water: A tidal datum

Mean Lower Low Water: A tidal datum

Oakland Tidal Canal
The City of Alameda before 1903 was a peninsula extending out from East Oakland and into the San Francisco Bay.  The Oakland Estuary use to end around somewhere around the  current Park Street Bridge location.  During these times the estuary was fouled with sewage and debris.  There was also a silting problem which limited the usefulness of the harbor.  In 1903 the United States Army Corp Of Engineers completed the construction of the Oakland Tidal Canal. With the canal completed it not only made Alameda a island City the tidal action flushed the Oakland Estuary of its sewage, debris and stopped the silting-up of the estuary.  This also created a need for bridges there are currently 6 draw bridges of various designs that cross the water way.

The Oakland Estuary has been dredged many time over the years.  There is a current dredge project underway that will allow large container vessel's to utilize the Port of Oakland more effectively.  The Port of Oakland is one of the largest Containerized Ports in the Untied States and this project is vital to the economic vitality of the Bay Area.

Pacific Gas and Electric is a large power utility company that supplies gas and electric power to most of  Northern California.

It may imply other things but in drawbridge speak it's usually the main bearing that bridge pivots on.  The ones used on our drawbridges are made of brass and are very large.  See the virtual tours for pictures of the various trunions.

Vertical Lift Bridge
Another common type of draw bridge is the Vertical Lift Bridge.  While a Bascule Bridge is usually a counterbalanced leaf.  A Vertical Lift Bridge is usually a center draw span supported by two towers.  Each Tower has a massive counterweight to help lift the bridge.  While there are many different designs all Vertical Lift Bridges are based on the same engineering principle.