The report possibly derails a project that many in Hayward assumed was a done deal because the state agency originally certified it in 2002.
The most significant concern, commission staff members said in their recommendation against the project, is not so much air pollution as it is the "thermal plumes, or columns of warm air," that could interfere with aircraft approaching Hayward Executive Airport.
"People have become more knowledgeable about how thermal plumes affect the approaches to airports, especially for light aircraft, which are the majority of those that use the Hayward airport," commission spokeswoman Susanne Garfield said.
San Jose-based power plant developer Calpine Corp. has been planning to build the massive natural gas-burning plant since the late 1990s but was forced to reapply after an economic downturn and other delays put the project on the back burner.
Calpine eventually lost control of the plot of industrial land for which the project was initially approved, and it faced internal financial troubles leading to a bankruptcy filing in late 2005.
But it found another plot of land about 1,300 feet away, adjacent to Hayward's wastewater treatment plant, and entered a partnership last year with General Electric that would help finance the plant's construction.
Pacific Gas & Electric also signed a 10-year power purchasing contract with Calpine last year, meaning the investor-owned utility would provide natural gas to the plant, and then procure the electricity generated by the plant to power tens of thousands of Bay Area homes and businesses.
Mike Argentine, director of project development for Calpine, said he remains optimistic that the plant will be approved by the commission and get built.
The commission staff's 494-page report released Monday is a preliminary assessment, not a final one. The project still has to go before the full board of appointed energy commissioners.
Argentine said the commission's concerns about thermal plumes stem from a difference in opinion on the effects those plumes might have on low-flying aircraft.
In March, a commission report said it was looking into the problems that hot, mostly invisible, high-velocity plumes had created at another power plant site in Southern California.
"Plumes are thermally buoyant during colder weather and more likely to maintain their vertical velocity at higher altitudes under calm, cool conditions," the report said.
There is also a difference in opinion on how to interpret Hayward's land-use plan for its busy general aviation airport off of Hesperian Boulevard.
"I think the city believes we are consistent with that plan and the (California Energy Commission staff) believes we are not, apparently," Argentine said. "We believe that we are consistent with the plan."
The Hayward City Council twice voted in support of the plant -- first at the original site and again last year after Calpine resumed its interest in pursuing the project. One of the perks of the plant's construction would be Calpine's promised contribution of $10 million to help build a new public library.
But a number of Hayward residents have opposed the plant based on environmental concerns. Opposition grew in the last year after another company, Texas-based Tierra Energy, proposed a second, 115-megawatt power plant in the same area, leaving neighbors wondering why Hayward was being targeted as a site for polluting energy projects.
Residents began fighting against the second plant proposal, and the Hayward City Council joined them and unanimously voted against it in March.
Teresa Frank, who lives and teaches at an elementary school near the proposed plants, said she is concerned about the pollutants both plants would emit and was happy to hear that the commission staff is recommending against the Russell City project.
"What really upset us is they thought we were not going to fight it," she said. "We're not irrational. We are not the hillbillies they thought we were."
Garfield said the thermal plumes are the most significant concern, but the commission staff also is recommending a laundry list of conditions on the project, which are different from those originally imposed in 2002.
Argentine, however, said that other than the dispute over aircraft dangers, Calpine is "pretty happy" with the parts of the report it has seen, including those dealing with air quality issues.
The plant would work on a combined-cycle system that circulates some of the exhaust produced during the combustion process back into a steam turbine.
On Monday afternoon, the commission posted its assessment of the Russell City plant on its Web site at http://energy.ca.gov/sitingcases/russellcity--amendment/documents/index.html.
A similar state assessment of the other proposed plant, Eastshore Energy Center, is due at the end of this month. Commission staff members said they are also examining aviation safety concerns surrounding that proposed plant.
Reach Matt O'Brien of the Oakland Tribune at 510-293-2473 or email@example.com.