EL CAJON — El Cajon has started using just over $204 million in pension obligation bonds to pay down its unfunded liability — the gap between how much is needed to pay retiree benefits and the amount of assets a jurisdiction has — with the the state’s pension system. Each year, taxpayers pay tens of millions of dollars to the California Public Employees’ Retirement System to fund lifetime pensions for existing and retired city employees. El Cajon currently owes more than $200 million to CalPERS, which requires its clients, including El Cajon, to pay off debt over the next 25 years at a current interest rate of 7 percent.