In another era, SEPTA's proposal to build a power plant in an industrial complex near its Wayne Junction station might have attracted little attention.

SEPTA says the project, which would power most of the transit agency's northern Regional Rail system, will keep its trains running in case of a Peco blackout. It also says the $26.8 million plant will save money, and require no outlay for the cash-strapped agency.

But SEPTA's proposed power plant would be fueled by natural gas, which despite its clean-burning attributes has become a lightning rod for anti-fossil-fuel activists. Members of the climate-change campaign 350 Philadelphia have alerted the surrounding Nicetown-Tioga and Germantown neighborhoods, and SEPTA's project is in their crosshairs.

"If we give a good shouting, maybe they won't put the plant there," said Michelle Johnson, 59, a Germantown resident who lives on Earlham Terrace, about a mile from the proposed site.

"I think it's sneaky they're trying to put it there," said Mary Morman, 77, Johnson's neighbor. She has chronic obstructive pulmonary disease, and worries about the power plant's health effects.

SEPTA says plans for the 8.8-megawatt plant, which was announced in October, are not final. But the agency's planners acknowledge they were caught off guard by the opposition.

"I didn't see it coming," said David T. Montvydas, SEPTA's chief engineer for engineering, maintenance, and construction. "This plan is relatively small when it comes to power plants."

SEPTA held a pre-application meeting with the city's Air Management Services, which "didn't see anything that was likely to be a problem," said Jeff Moran, the city Health Department spokesman.

Once SEPTA submits a proposal, the city air agency will review the project and publish its findings, Moran said. If it receives public comments, it would conduct a hearing before issuing a permit.

As a public agency, SEPTA's decision-makers are more exposed to outside pressure than private power developers. But SEPTA's challenges are likely to become standard fare for future power projects as climate-change activists step up campaigns to force a switch to renewable energy.

The cogeneration system SEPTA proposes to install has become popular with large energy customers as a way to reduce reliance on a vulnerable electric grid. Cogeneration, or combined heat and power, produces electricity and usable heat at the same time, improving energy efficiency and reducing costs.

Gas cogeneration systems are not uncommon. Philadelphia Gas Works, a Center City hotel, many hospitals, and the Philadelphia Water Department have installed them. Lincoln Financial Field's celebrated green-energy plan, with its visible solar and wind generators, includes a 7.6-megawatt gas cogen plant.

In October, SEPTA selected Noresco L.L.C. to design the plant, which calls for two piston-engine generators similar to a type manufactured in Austria by GE Jenbacher. The engines would be housed in a 40-by-105-foot corrugated-steel building erected between SEPTA's Roberts Avenue Rail Yard and the Midvale Bus Depot, which houses more than 300 buses.

The site, bracketed by Roosevelt Boulevard to the northwest and the CSX freight lines to the southeast, is 1,000 feet from the nearest residence, 1,500 feet from the baseball fields at Fern Hill Park, and 2,000 feet from the Salvation Army's Kroc Center of Philadelphia.

But that's too close for comfort for surrounding neighborhoods, which organized successfully in the past to oppose a proposed Trump casino and a plan to park Lower Merion Township's school buses.

"There's a history here of nuisancelike proposals being put forward, as if it was still an industrial area without any people living here," said Irv Ackeslberg, cochair of the Southwest Germantown Neighbors Association.

Organizers from 350 Philadelphia say SEPTA should install renewable solar panels instead of a gas plant, and point to efforts by other transit agencies to obtain their power from renewable sources.

SEPTA says intermittent renewable energy, along with a massive array of storage batteries, would not be able to provide competitively priced on-site power to run a railroad independent of the electric grid. They said the price also would not satisfy requirements of Pennsylvania's Guaranteed Energy Savings Act, which allows SEPTA to finance the project with the savings it would create over its current energy costs.

SEPTA points to a plan by NJ Transit, which was stung by power outages after Hurricane Sandy, to install its own gas-fired power system to harden itself against outages.

"We have to be prepared for a what a crazy weather future looks like, and this approach allows us to do that without having to lay out any of our capital," said Erik S. Johanson, SEPTA's director of business innovation.

The activists don't buy that argument.

"I don't think it has been demonstrated that the best way to improve reliability is to build a natural gas power plant that will run every day of the year just for the rare occasion when there is a power outage," said Mitch Chanin, a member of 350 Philadelphia's steering committee.

"For me," Chanin said, "it seems a little perverse to build more fossil-fuel infrastructure to compensate for the damage that climate change is causing to the electric grid."