The Park Street Bridge is a four lane double leaf bascule bridge spanning 372 feet of the Oakland Estuary, similar to the bridge at High Street. The Oakland Estuary is a navigable water way with access to the San Francisco Bay.
A bascule bridge is a a draw bridge that is counter-weighted so that it may be raised or lowered easily. It is a conduit for approximately 40,000 vehicles each work day. When the bridge opens, the inside edges are over 17 stories above the surface of the water.
The original bridge was completed in 1893. This bridge, and the High Street and Fruitvale Avenue bridges, were built by the U.S. Government in exchange for permission and rights-of-way to dredge the channel between San Antonio Creek and San Leandro Bay. It had a wooden deck, a wrought iron thru truss swing span and wooden trestle approach spans. Riding the bridge as it opened to let water traffic through, as well as fishing off the bridge, were popular activities. It took a full ten years after the bridge was built to dredge the channel.
The present bridge was designed by the County of Alameda Surveyors Office and constructed under the Federal WPA Program. it was opened in 1935 with a Grand Opening celebration that included a public wedding of a man from Oakland and woman from Alameda to symbolize the unity of the two cities with the building of the bridge.
The Park Street Bridge shall open on signal; except that, from 8:00 a.m. to 9:00 a.m. and 4:30 p.m. to 6:30 p.m. Monday through Friday except federal holidays, the draws need not be open for the passage of vessels. However, the draws shall open for the above closed periods for vessels which must, for reasons of safety, move on a tide or slack water, if at least two hours notice is given. The draws shall open as soon as possible for commercial vessels engaged in rescue or emergency salvage operations.
The bridge is manned by an alternating four person crew. The bridge is equipped with a Marine Radio, the preferred working channel in the San Francisco Bay Area is Channel 9 and Channel 16 is used for hailing and distress. Vessels can also gain a bridge opening by using a horn. The signal is a long blast followed by a short blast. Signal flags and lights may also be used if Coast Guard approved methods are followed. For more information on drawbridge operations, see "California Drawbridge Regulations" by the Coast Guard. Although draw bridges are required to open for vessel traffic even if that means that vehicular traffic must wait, there are some exceptions to this rule.
Vessel and Vehicle Traffic
- 1,755 Opening per year
- 2,150 Total Vessels
- 601 Barges
- Northbound 21,400 vehicles per day
- Southbound 16,750 vehicles per day
- Total Vehicle Traffic per day 38,200
- Busiest Hour North Bound 7:30 to 8:30 am 2255 vehicles
- Busiest Hour South Bound 4:45 to 5:45 pm 1520 vehicles
- Slowest Hour North Bound 3 am to 4 am 52 vehicles
- Slowest Hour South Bound 4 am to 5 am 65 vehicles
WORKINGS OF THE BRIDGE
The Park Street Bridge is the main thoroughfare into downtown Alameda and averages almost 40,000 vehicles a day. Park Street is a double leaf bascule bridge in which each leaf can be operated independently. The bridge employees a steel superstructure that utilizes steel channels with cross lacing and rivets.
Each leaf of the Park Street Bridge has its own machinery room with 75 HP, 3 phase, 480 volt electric main drive motors and an auxiliary drive system which includes multiple gear reductions similar in design to a manual automobile transmission, only many times larger without housing.
Power to the bridge is supplied by the Bureau of Electricity (City of Alameda), backup power is supplied by PG&E. A 75 hp main motor and a 5 hp backup motor provide the muscle to raise the bridge. Park Street is stopped by two service brakes and two hydraulic brakes. The service brakes are used to stop the bridge in normal operating conditions. The hydraulic brakes are used for emergency stopping power.
Park Street is the only bridge operated by the County that has two complete operator towers. The Alameda Tower is the main operational tower and can operate both leafs under normal or emergency power. The Oakland Tower can only operate the Oakland leaf under normal or emergency drive. The dual tower system has been put to good use during the current renovation of the Park Street Bridge. The bridge had an electrical update in the 1960's which was an improvement over the early 1930's technology.
Each leaf of the bridge can open to a 78 degree position, this is considered a full opening. A normal opening is 70 degrees and can accommodate 95% of vessel traffic. With a full opening the bridge can accommodate almost any vessel. The main limiting factor would be vessel width and the depth of the channel. Each leaf of the bridge is 120 feet in length. Massive counterweights which are out of view helps balance the bridge leafs when opening.
1998 RENOVATION PROJECT
1998's renovations were part of an ongoing $5.6 million Public Works Agency project to renovate and paint the Park Street Bridge.
The project included a complete stripping of all paint and primer and repainting with more environmentally safe materials. The paint job was a very complex project as the paint and primer was lead based and had to be contained. During removal, the bridge was enclosed in a confinement tent that keeps the new paint from entering the water or elsewhere. The paint was then vacuumed and trucked away for disposal. The bridge was completely stripped down to the metal, then re-primered and painted in a dark green color which was chosen by the City of Alameda's citizens.
New submarine cables were installed which carry the power cables that power the bridge under the water. The new cables were beginning to leak and cause electrical problems. The new submarine cables are expected to last for almost 50 years. The new power cables were hooked up to brand new operator consoles which will provide for more efficient operation of the bridge and provide more data to the bridge operators to trouble shoot any problems.
The Renovation Project completed replacement of the Barriers, Tail Locks, and Center Lock System. The Barrier Systems consists of cables that travel down a steel structure. They were designed as an impediment for vehicles. The Tail Lock Systems lock the tail end of the bridge. Each leaf contained a tail lock. When the Tail Locks are engaged they keep the tail end of the bridge from moving when the bridge is in the down position. A hydraulic system replaced the electromechanical system in use now.
The Center Lock is a locking system that locks the two leafs together in the center. This keeps the bridge from bouncing in the middle while the bridge is in the down position. A new electrical mechanical system will replace the existing electromechanical system.
WALKWAY, LIGHTS, CAMERAS
The Pedestrian Walkways on the bridge were replaced. The metal decking was removed because of heavy rust and was replaced by new steel decks. The new walkways were almost impossible for people in wheelchairs to negotiate. The new walkways have a gradual slope and rest points making it much easier to use. The vehicle roadway deck was not replaced but there was welding and sealing done to help preserve the roadway deck.
New energy efficient roadway and approach way lights and closed circuit monitors and cameras are going to be installed to aid in the operation of the bridge. The cameras and monitors will help the operators ensure that pedestrians are in a safe area before opening the bridge. The security system keeps anyone from braking into the many bridge areas.
During the renovation the bridge was closed to all vehicle and pedestrian traffic but was able to open to vessel traffic using the Alameda Leaf of the bridge at times. We appreciate the public's patience while important work was undertaken.
Bridge Tender Ken Sequeira complied this renovation update.
- Vertical Clearance MLLW (Low Tide) 21 ' 1"
- Vertical Clearance MHHW (High Tide) 14 ' 8 "
- Clearance Between Fenders 240 Feet
- Maximum Vehicle Load Limit 44.5 Tons
- Bridge Height Restriction for Vehicles 15' 4 "
- Bridge Width 57 Feet
- Bridge Length 250 Feet
- Width of Roadway 44 feet
- Width of Traffic lanes 12 feet
- Pedestrian Sidewalk's 6 Feet