Years of failed efforts to fix severe financial defects in Fort Worth's city employee pension plan will come to a head at City Council meetings in the next two weeks.Put simply, the pension plan for more than two decades has been more generous to employees than the city's taxpayers can afford. Yet the council has not found an acceptable way to change that or the political will to make it happen. Now is the time.The city staff has recommended changes that will put the plan back on firm financial footing, unfortunately but unavoidably through reductions in projected benefits for employees.Nobody likes that. But one clear point has come out of the council's pension discussions in recent years: The current plan is unsustainable. Without change it will soak up larger and larger shares of the city budget, year after year.Both taxpayers and employees deserve a more stable plan.Key changes to pension benefits for future hires other than police and fire employees were put into effect last year. That was a laudable step, one that reflected a hard-won resolve to fix the problem. But more is necessary, and the council must maintain that resolve.The heart of the council's discussions in its next two meetings, on Tuesday and on Oct. 23, will be the staff's recommended changes in the way pensions will be calculated for past police service and less-generous calculations for all future service by police and general employees. Fire employees are covered separately by a collective bargaining contract.More than two-thirds of the city's police officers have voted to increase their contributions to the pension fund in hopes of retaining their current benefit formula. The council is expected to receive reports from actuaries hired separately by the city and the pension fund board detailing the impact of those increased contributions on the health of the fund.It's a long shot that the police proposal will fix the problem. But it will change the equation, leaving the council to decide whether that change should be met by any alterations in the staff-recommended steps. A vote on how to move forward is set for the Oct. 23 council meeting.Available numbers show how steep a hill the police officers are trying to climb. Before the police vote, studies of the problem were conducted by both the pension fund board and by local accountant William T. Leonard on behalf of the Fort Worth Chamber of Commerce.One key number is the size of the city's annual contribution to the retirement fund. Measured as a percentage of annual payroll expenditures, that contribution has more than doubled since 2007, Leonard's study shows.Yet the pension plan's unfunded liability, the amount of money it is obligated to pay out to current and future retirees but does not have and is not projected to get, grew from $161 million in 2007 to $918 million at the end of 2011, Leonard reported, citing figures from the city and the pension fund board.The council has drawn a line, saying the city's pension contributions should not be allowed to exceed 20 percent of payroll costs. It now stands at 19.98 percent, the pension fund board's actuarial report says, and without plan changes it will surpass 20 percent next year and for at least the next 10 years.Before the police contribution increase is considered, the only way to keep city contributions below 20 percent of payroll would be to apply all of the city staff's recommended changes to the benefit formula and assume a rate of investment return that is unrealistically high in today's financial markets, the pension board's actuarial report shows.This is one of the most difficult challenges the council will ever face, full of painful choices. But the council must not back down.