>> BUILT IN 1937, IN THE MIDST OF THE GREAT DEPRESSION, THE GOLDEN GATE BRIDGE IS NOT ONLY ICONIC, BUT A SYMBOL OF AMERICAN INGENUITY AND RESOLVE. THE TWO TOWERS STAND NEARLY 750FT ABOVE WATER STRUNG WITH 80,000 MILES OF CABLE. A BAY AREA BEAUTY AND NECESSITY 8-80 CARRYING 37 MILLION VEHICLES EACH YEAR, MORE THAN 100,000 PER DAY, INCLUDING HALF A MILLION FREIGHT TRUCKS SERVING AS A KEY LINK FOR SUPPLY CHAINS. >> THERE IS ONLY ONE GOLDEN GATE BRIDGE AND WE ARE GOING TO PROTECT US, TRANSPORTATION SECRETARY PETE BUTTIGIEG TOLD US THIS LAST JANUARY. >> THE QUESTION IS HOW. >> WE ALWAYS SAY DIRT TO FLY. >> SPEAKER EMERITA NANCY PELOSI FOUGHT FOR YEARS TO STRENGTHEN THE GOLDEN GATE BRIDGE. MOST RECENTLY, SHE AND HER CONGRESSIONAL COLLEAGUES WERE CRITICAL IN SECURING $400 MILLION TO PROTECT THE BRIDGE FROM SEISMIC THREATS DUE IN PART TO THE HISTORIC BIPARTISAN INFRASTRUCTURE LAW PASSED IN 2021. >> AND THAT WAS A REAL BATTLE. AND WE WERE SUCCESSFUL IN GETTING THAT DONE. >> PELOSI SAYS ROUGHLY 43,000 BRIDGES ACROSS THE U.S. ARE CURRENTLY RATED IN POOR CONDITION AND THIS LAW WILL BENEFIT 15,000 OF THEM. YET SHE WAS ABLE TO SECURE THE MOST FOR THE GOLDEN GATE. CAN YOU WALK ME THROUGH THAT LONG TERME INVESTMENT AND HOW IT WILL PLAY OUT? >> THEY WILL RETROFIT SOME PIECES. THEY WILL RESTORE SOME AND THEY WILL HAVE NEW THINGS THAT THEY BRING IN LIKE THIS. >> DOZENS OF DEVICES THAT WILL PROTECT THE STRUCTURE OF THE BRIDGE IN THE EVENT OF A BIG QUAKE. THEY'RE CALLED ENERGY DISSIPATION DEVICES. WHAT WE FOUND IS THAT THESE DEVICES WORK AMAZINGLY WELL. DENNIS MULLIGAN IS THE GENERAL MANAGER OF THE GOLDEN GATE HIGHWAY AND TRANSPORTATION DISTRICT. >> NOW, WE DON'T YET HAVE AN ESTIMATE OF THE. >> WHILE PARTS OF THE BAY BRIDGE COLLAPSED DURING THE 1989 LOMA PRIETA EARTHQUAKE, THE GOLDEN GATE WITHSTOOD IT. MULLIGAN EXPECTS THE NEXT ONE WILL LIKELY BE WORSE, BUT IT'S IMPORTANT TO REALIZE THAT THAT EARTHQUAKE WAS 60 MILES AWAY. >> IT WAS A SANTA CRUZ EARTHQUAKE. AND WHILE THE MAGNITUDE NUMBER SOUNDS BIG, IT'S ACTUALLY A MODERATE EARTHQUAKE. AN 8.3 MAGNITUDE EARTHQUAKE WOULD BE, YOU KNOW, MORE THAN 100 TIMES MORE ENERGY SINCE THEN, THE DISTRICT HAS BEEN PREPARING. IT WAS A GOOD WAKE UP CALL, AND WE EVALUATED OUR STRUCTURE. >> THE FIRST THREE PHASES OF THE GOLDEN GATE BRIDGE SEISMIC RETROFIT WERE COMPLETED IN 2014. THIS INCLUDED RETROFITTING THE NORTH AND SOUTH ENDS OF THE BRIDGE WHERE THE CABLES ARE SECURED TO BEDROCK AREAS FOUND TO BE THE MOST VULNERABLE. IT ALSO INVOLVED WIND TUNNEL TESTING AND REPLACING THE STEEL SUPPORTS TO PUT A NEW FOUNDATION THAT'S TEN TIMES STRONGER, AND WE PUT SEISMIC ISOLATION BEARINGS ON TOP. >> SO WHEN THE GROUND STARTS TO SHAKE, THAT TOWER DOESN'T HAVE TO DRAG THE WHOLE WEIGHT OF THE BRIDGE WITH IT. IT DECOUPLES IT. SO THERE'S LESS FOR ON THE TOWER. BUT THERE'S STILL A LOT OF WORK TO BE DONE, INCLUDING RETROFITTING THE SUSPENSION BRIDGE, WHICH IS SET TO BEGIN THIS YEAR. >> THIS IS WHERE HUNDREDS OF FLOOR BEAMS WILL BE REPLACED WITH NEW BRACING, A PROCESS THAT WON'T BE COMPLETE UNTIL 2029. SO WHAT HAPPENS IF WE HAVE A BIG EARTHQUAKE BEFORE THEN? >> THE BRIDGE IS SAFE. IT WILL NOT COLLAPSE. NO ONE WILL DIE IN THE BRIDGE. HOWEVER THERE WILL BE DAMAGE. THERE WILL BE SIGNIFICANT DAMAGE THAT WILL NECESSITATE POTENTIALLY HAVING TO REPLACE THE BRIDGE. >> THE COST OF REPLACING SOMETHING LIKE THE GOLDEN GATE BRIDGE WOULD RANGE FROM. >> TO REPLACE A BRIDGE OF THIS SCALE WITH. THIS SPAN LENGTH IS PROBABLY NORTH OF $10 BILLION, SO A REALITY CHECK. >> WHAT ARE THE CHANCES OF THE NEXT BIG QUAKE? >> OVERALL, THE REGION FACES THIS 72% CHANCE OF A REALLY LARGE EARTHQUAKE, A MAGNITUDE 6.7 PLUS IN THE NEXT THREE DECADES. >> USGS EARTHQUAKE SCIENTIST AUSTIN ELLIOTT SAYS MOST OF THAT THREAT COMES FROM THE HAYWARD FAULT, WHICH HAS A 1 IN 3 CHANCE OF PRODUCING AN EARTHQUAKE WITHIN THAT WINDOW. BUT TO PUT THAT IN PERSPECTIVE, USGS SAYS THE MARGIN OF ERROR IS DECADES, MEANING IT COULD HAPPEN TOMORROW OR IT COULD HAPPEN 20 YEARS FROM NOW, ELLIOTT EXPLAINS. WHILE IT'S DIFFICULT TO PREDICT PRECISE NUMBERS, THE LATEST ESTIMATE FROM THE NATIONAL SCALE FORECAST SUGGESTS THE HAYWARD FAULT COULD SEE AT LEAST A MAGNITUDE 7.1 TO 7.3, UP TO A 7.5, WHILE THE SAN ANDREAS FAULT COULD PRODUCE UP TO A MAGNITUDE EIGHT AS FAR AS ANOTHER MAGNITUDE EIGHT FROM THE SAN ANDREAS FAULT. >> THAT'S PROBABLY FARTHER OFF IN OUR FUTURE, BUT IT IS INEVITABLE. BUT RECENT RESEARCH PEOPLE HAVE DONE SOME MORE SPECIFIC MODELING OF THE HAYWARD IN PARTICULAR, THAT SUGGESTS THAT THE MAGNITUDE COULD BE LARGER, ESPECIALLY IF IT LINKS WITH OTHER FAULTS. >> USGS RECENTLY IDENTIFIED A STRUCTURAL CONNECTION BETWEEN THE HAYWARD FAULT SOUTH OF SAN PABLO BAY AND THE RODGERS CREEK FAULT, NORTH OF SAN PABLO BAY. ESSENTIALLY ONE BIG CONTINUOUS STRUCTURE THAT MAY HOST A SINGLE LARGE EARTHQUAKE. >> THAT DOESN'T NECESSARILY MEAN THAT THE GROUND SHAKING AT ANY INDIVIDUAL SPOT WOULD BE STRONGER, BUT THE EARTHQUAKE WOULD LAST LONGER, AND THE AREA THAT'S AFFECTED WOULD BE MUCH LARGER. >> BUT AS ELLIOTT POINTED OUT, MAGNITUDE ALONE DOESN'T TELL THE WHOLE STORY. MODELING BY US GS SHOWS PART OF THE THREAT IS TIED TO WHERE ON THE FAULT THE QUAKE BEGINS, AS IT DEPENDS ON REALLY WHERE AN EARTHQUAKE STARTS AND THE NATURE OF THE FAULT SLIP ITSELF THAT CONTROLS HOW GROUND MOTION AND THE INTENSITY OF SHAKING WILL BE DISTRIBUTED AROUND THE REGION, BRINGING WITH IT SHOCK WAVES THREATENING INFRASTRUCTURE ACROSS THE BAY AREA, INCLUDING THE GOLDEN GATE. >> YOU KNOW, IF YOU'RE ON THE ROADWAY, IT'S SECURE. THE PARTS OF THE BRIDGE THAT WILL TWIST AND HAVE DAMAGE ARE BELOW THE ROADWAY. >> THE NEXT PHASE OF THIS RETROFIT IS EXPECTED TO BEGIN LATER THIS YEAR. AS FAR AS IMPACTS TO COMMUTERS, WE'RE TOLD TWO LANES WILL BE CLOSED DURING THE OVERNIGHT HOURS IN SAN
