SAN JOSE — San Jose is still struggling to find enough technicians to keep the city’s massive, aging wastewater treatment plant running despite efforts to hire outside contractors and retain staff.

In a report to be heard at the City Council’s Transportation and Environment Committee on Monday, city officials say a fourth of its technician positions at the plant are now vacant as a rash of resignations and retirements continues amid competition statewide for such technically trained workers.

“The steps we’ve taken to date have not been sufficient to attract and retain staff,” said Environmental Services director Kerrie Romanow. “We do have a very high vacancy rate, and that’s very challenging. We’re running a lot of overtime. Our staff is tired. We’re working hard to find creative solutions, but nothing so far has been effective.”

The Water Pollution Control Plant, known at City Hall as the WPCP or “Weepy Seepy, ” dates to 1956 and provides wastewater treatment for 1.4 million residents and 17,000 businesses in San Jose, Santa Clara, Milpitas, Campbell, Saratoga, Los Gatos and Monte Sereno. Last year, the San Jose City Council approved a $2.1 billion long-term plan to modernize the aging plant.

A city audit in August raised alarms over staffing shortages at the plant, where it noted that a major failure would “imperil public health and safety” with raw sewage flowing directly into the bay or backing up and overflowing through the sewer network into streets and streams.

A city department report at the time said the plant had lost 90 workers — 43 percent of its workforce — in the past three years. Adding to an expected wave of Baby Boomer retirements was an exodus of fed-up technicians as city leaders imposed pay and benefit cuts to deal with rising pension bills. Staffing vacancies had grown from 5 percent in four years ago to 20 percent, with overtime soaring for those remaining.

City officials in August approved several steps to deal with the problem, boosting pay for certain plant positions to retain staff and approving up to $3 million a year for a contract to hire outside temporary instrument control technicians and industrial electricians for the plant, at rates 15 to 30 percent higher than the city’s own workers.

But the exodus has continued, with vacancy rates rising to 25 percent, forcing city officials to scramble for new solutions.

“We’re in discussions with the city about ways to address the issue, and we’re still trying to figure out the best way,” said Bill Pope, business agent for the city’s operating engineers union. “I know it’s a major concern to the city. It’s a major concern to my members. They’re having to pick up all that extra work.”

City officials plan to suggest a “mutual aid” type of agreement for sharing staff, similar to the backup procedures that firefighters and police use to draw extra hands from neighboring jurisdictions when dealing with major incidents, with other public wastewater plant operators in nearby Sunnyvale and Palo Alto.

“It fits in the category of problems that are both foreseeable and intractable,” said Councilman Sam Liccardo, who chairs the Transportation and Environment Committee. “With or without pay cuts, we were going to lose a lot of quality staff through attrition. Obviously, the pay cuts accelerated the process. We’ve made many attempts to supplement incomes to retain as many qualified staff as possible. But we have to continue to be creative and that requires looking to outside companies and agencies. If you know any electricians, send them our way.”

Contact John Woolfolk at 408-975-9346. Follow him on Twitter at Twitter.com/johnwoolfolk1.