WestCon Tribune

January Review

 

Spanning the Carquinez Strait

Building the

Alfred Zampa Memorial Bridge

Presented By: Bart Ney,

Public Information Manager, Caltrans

Project Manager, Moore, Iacofano,Goltsman Inc.

 

The new year started out with an outstanding presentation by Bart Ney, Public Information Manager for Caltrans and a project manager for Moore, Iacofano, Goltsman. Assisted by a video which will be used in an upcoming documentary, Mr. Ney conveyed a visual overview of the building of the Alfred Zampa Memorial Bridge, more commonly known as the Carquinez Bridge.

In 1988 a mandate passed by voters increased bridge tolls from sixty cents to a dollar. The increase in tolls paid for all of the work done to build the bridge at a cost of $200 million.

The site already had two bridges on it, one built in 1927 and the second built in 1958. These two spans carried on average 109,000 drivers each day. Both of the current structures did not meet seismic design or traffic safety standards. The 1958 bridge was able to be retrofitted, but the 1927 span exhibited deterioration to the metal components and could not be kept in use during retrofitting, and therefore replacement was a better option.

One main reason for building a suspension bridge was that the load is being held by the main cables and only two towers. Not having to build a tower in the middle of the strait saved money, maintenance problems and safety issues involving workers.

The new  bridge is the first suspension in the country that has concrete towers and pile foundations. The steel casings are ten feet in diameter and 150 feet long. The piles go down into the ground at least 300 feet so they are as deep underwater as the old bridges are tall. There are six pilings for each tower leg.

The towers are about 400 feet tall and contain about 3000 metric tons of concrete each. The west tower shaft contains an elevator and the east side houses a stair case.

Cable spinners were used to put in the 13,000 miles of cables in place. Cable spinning is not a new technique, but  modern use of computers allowed tension to be calculated and consistent and eliminated the need for additional wire workers to control placement and tension. Each strand of wire is about 5 millimeters and strong enough to hold up a Hummer vehicle. There are 8,584 strands of wire in each cable and each cable is one continuous strand of wire. After cables were spun a compacting machine was used to compress the cables into a cylinder and cable bands were applied.

The cross structure that is driven on is hollow and is supported by 90 degree angles. There were 24 sections needed for the bridge, each weighing about 600 tons which is actually lighter than regular construction. The hollow plates allow for a crawl space that is used for utility lines, protecting them from the sea air and  assist in easier maintenance. To place these sections, a  new method was invented. The process actually allowed the panels to be lifted from a barge underneath and climb themselves into place by strand jacks where they were locked in permanently by workers. Due to obstruction, a few of the panels had to be placed on diagonal strand jacks and swung into place.

Learning from the 1989 earthquake and the problems with the Bay Bridge, this span has no regular expansion joints. All 24 segments were welded together to create one continuous piece. There are steel locker arms which allow movement. Four feet of movement is accommodated on either side of the bridge for earthquakes and normal heat expansion and contraction.

Alfred Zampa was an ironworker who lived in Crockett and worked on all of the bridges built in the Bay Area. He actually is one of the very few workers to survive a fall from the Golden Gate Bridge. After being released from the hospital, he returned to the top of the tower to continue his job. In 2000 when the project started on the bridge, Mr. Zampa assisted with the ground breaking ceremonies. He died shortly after the start of construction. Mr. Zampa is the first “blue collar worker” to have a bridge named after him.

Our thanks to Mr. Ney for an informative, educational and entertaining presentation.  If you missed this, you may want to keep an eye out for the documentary which will be shown soon on television.