It’s no walk in the park on Transbay Transit Center...

Less than a year after it opened, the pathway that runs through the troubled Transbay Transit Center’s rooftop park is being torn out and replaced at a cost upward of $1 million.

After months of repeatedly patching up the eco-friendly path, officials have determined it is beyond repair.

“Clearly, the path is not measuring up to ours or the public’s expectations, and we need to fix that,” Transbay Joint Powers Authority spokeswoman Christine Falvey said.

In its brief lifetime, the walkway gave thousands of visitors access to the park’s attractions and botanical displays, all framed by panoramic views of the surrounding streets and buildings.

Unfortunately, the decomposed granite used in the pathway, which winds the length of the three-block-long park, failed to hold up even under normal foot traffic.

In fact, the walkway began falling apart before the $2.2 billion transit center opened last August, with dozens of spots along the half-mile loop cratering like sidewalk potholes.

The walkway was only in full use for about six weeks before the entire center was closed in September when cracks were discovered in two of its key support beams.

But even without foot traffic, the path continued to deteriorate in the winter rains.

“We want to rebuild the path with a cost-effective, easy-to-maintain, durable material,” Falvey said.

She estimated demolishing and removing the pathway would cost about $500,000.

Replacing the 10-foot-wide walkway will mean pumping about 50 cement trucks’ worth of material 70 feet up to the center’s fourth-floor roof garden. Workers are already tearing out the walkway and hauling the debris out in giant bags.

Bids are still out for the replacement work, so it’s too early to say for certain what the final cost will be. Sources, however, said it would likely cost at least another $500,000 to replace the walkway with concrete, bringing the total to $1 million — likely more.

Who pays for the fix remains to be seen.

Falvey said the walkway is a warranty issue. The center’s main contractor, Webcor/Obayashi Joint Venture, disagrees.

Webcor/Obayashi “repeatedly cautioned the TJPA that the product was not right for the project,” said Amanda Gillespie, vice president of Webcor Builders. “The TJPA directed the product be installed as specified and then modified the standard manufacturer’s mix to attain the custom dark gray color. WOJV views this as an error in product specification, and the product has performed as WOJV and McGuire & Hester forewarned.”

The next stop will be a hearing before a dispute resolution board to determine who will pay.

Replacing the crumbling path is the latest repair needed on the massive transit center. The fix on the cracked beams is expected to be completed in June, but a reopening date has yet to be set pending an independent review of the entire center’s construction.

The hope is to have the walkway back in operation by reopening day as well.

“The goal is to have a majority of the work done on the walkway by our reopening day to minimize the impact to the public,” Falvey said.

“What’s the rush? You can’t get into the building anyway,” said Supervisor Aaron Peskin, who chairs the San Francisco County Transportation Authority.

“This is the city that knows how — to screw up every major project,” Peskin said.

Foodie fuel: From french fries to fire trucks — that’s the goal of Oakland Mayor Libby Schaaf’s plan to use diesel made from used cooking oil, grease and other waste from local restaurants.

The city has been running its fleet of vehicles on biodiesel since 2015.

Now Oakland is upping the program a notch by partnering with Finnish energy company Neste and Western States Oil.

Under the plan, trucks will pick up used cooking oil. It will then be shipped to Neste’s processing plant in Singapore, where it will be processed into biodiesel, then shipped back in what is being billed as a “circular fuel economy.”

Price: about $4 per gallon — about the same price as regular diesel.

So now, “when Oaklanders eat french fries at Luka’s or TrueBurger, they’re putting fuel into our fire trucks,” Schaaf said.

Pass the ketchup.

San Francisco Chronicle columnist Phillip Matier appears Sundays and Wednesdays. Matier can be seen on the KPIX-TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call 415-777-8815, or email pmatier@sfchronicle.com. Twitter: @philmatier