BART riders, accustomed to delays, endured an unusually trying day Wednesday when a broken rail — discovered during the heart of the morning commute — curtailed San Francisco service and caused a systemwide slowdown that lasted for more than six hours.

As if that wasn’t enough, a PG&E power outage hit BART in the afternoon, prompting a three-station shutdown in the East Bay just as workers finished repairing the busted metal back in the city.

And there were two more morning delays spurred by debris and reports of a person on the tracks in Contra Costa County.

By 4 p.m., BART was restoring full service. Crowds of commuters flooded platforms at downtown San Francisco stations and packed onto some trains, though others had plenty of seats. Commuters who sought other ways home found longer-than-usual lines for ferries, and those summoning ride services Uber and Lyft faced surcharges that doubled the usual fares.

Wednesday’s spree of problems tested the patience of even the hardiest commuters who rely on the backbone transit system.

Dana Parso-Kilburg, a regional coordinator for Starbucks, stood frustrated on the platform at the 16th Street Mission Station just after the first train departed over the newly repaired tracks. She had gone to Embarcadero to try and make her way home to Hayward, but after all the trains were too full to board, she backtracked in hope of finding some room.

“I think BART is starting to show its age,” she said. “When I was a kid in the ’90s, it was fine, but now you have equipment problems all the time, the stations all smell like urine, and the seats are gross. It’s horrendous.”

Parso-Kilburg said it took her more than two hours to get into the city Wednesday morning. In the afternoon, she had to leave work early so she would have enough time to pick up her son from his babysitter.

PG&E said the power outage that shut down service to the Bay Fair, Hayward and Castro Valley stations affected about 1,200 customers. BART’s trains are powered independently of PG&E, but BART spokesman Taylor Huckaby said it forced BART to reboot its computers serving that part of the system.

The problems come as BART is struggling to rejuvenate and repair its aging infrastructure while carrying a record number of passengers — about 430,000 each weekday. Wednesday was an unusually bad day for BART, but the transit system has been plagued by an increasing number of delays.

A recent Chronicle analysis of data on delays from 2013 and 2014 found that interruptions lasting 15 minutes or longer have increased by 16 percent — 13 percent when you subtract the 8½ days of BART strikes during 2013. Since 2012, when The Chronicle did a similar study, longer delays have soared by more than 26 percent.

When it opened in 1972, BART was a shiny and promising example of the future of public transportation, with sleek silver trains controlled by computers shooting through a tube beneath San Francisco Bay. But 43 years later, the system is aging and BART officials are scrambling to catch up. New rail cars are on order, but the system also needs a new train control system and a modern train maintenance center. Repairs and maintenance, including several major rail replacement projects, are also needed to keep the system in good shape.

BART’s biggest trouble Wednesday was discovered about 9:20 a.m. when an East Bay-bound train operator reported an unusually bumpy ride between the 16th Street Mission and Civic Center stations, said BART spokeswoman Alicia Trost. BART immediately shut the track and dispatched an inspection team, which discovered a 10-inch gap in one of the rails. The transit agency e-mailed a photo that used a $1 bill to show the length of the gap in the broken track.

In San Francisco, trains had to share a single track while repair crews sliced out the damaged section of rail and installed a new piece as a temporary fix. What caused the gap in the rail is under investigation by BART and the state Public Utilities Commission, Trost said. She said the damaged stretch was not rail from when the system opened and may have been installed a year ago.

Gaps, cracks or other damage to the rails have been discovered before but are typically found during inspections, she said. Rails are inspected nightly by train, weekly on the ground and twice a year by more high-tech methods, including sonar. Outside consultants and the state PUC also conduct inspections.

With just a single track, BART halted service on the Richmond-Daly City line and curtailed service on others. Only the line to and from Pittsburg/Bay Point remained in full service. BART riders were urged to consider alternate forms of transportation.

Passengers heading from Dublin to Daly City had to transfer at the Montgomery Street Station in San Francisco. Those heading to Daly City from either Richmond or Fremont were advised to transfer at the MacArthur Station in Oakland. Shuttles were assisting riders from San Francisco International Airport.

Shirley Turnbo, a government worker, was affected by both of the day’s biggest messes. She was standing on the platform of the Montgomery Station around 2:30 p.m. when a voice came over the public-address system to announce that the power outage had afflicted the Bay Fair Station in San Leandro, where she was headed.

“I left work an hour and a half early just to avoid this mess,” she said. “I’m planning to retire because I can’t take too much more of this.”

Other riders where taking the setbacks in stride. George Castillo, a 52-year-old operations manager at Macy’s, was lucky in the morning, coming into San Francisco before the troubles began.

“Sometimes you have these big problems, which are a pain in the butt,” he said as he waited at the Powell Street Station in the afternoon for his train toward Bay Fair. “But I’ve been commuting for 12 years, and in a car it’s an hour and 15 minutes easy. On the train it’s a half hour and you can relax.”

One rider said in an e-mail to The Chronicle that a typical 35-minute ride from Walnut Creek to San Francisco took an hour and 25 minutes in the morning.

The rough day began, ominously enough, with separate delays on BART in the East Bay. Trost said two different issues resulted in delays along the Pittsburg/Bay Point line.

About 7:30 a.m., there was debris on the tracks between Lafayette and Walnut Creek, Trost said. The material was removed, but shortly thereafter BART police received reports that there was someone on the tracks near the Lafayette Station.

Officers searched the area but did not find anyone, Trost said.

Kale Williams, Michael Cabanatuan and Henry K. Lee are San Francisco Chronicle staff writers. E-mail: kwilliams@sfchronicle.com, mcabanatuan@sfchronicle.com, hlee@sfchronicle.com