The City Council unanimously approved a new contract with its biggest bargaining unit — SEIU Local 235 — which provides for pay increases of 7 percent staggered over three years. SEIU, which represents about 450 workers, agreed to take no wage increases throughout the recession and accepted work furloughs. In exchange, city administrators agreed to eliminate positions without laying off actual workers, though by attrition, the city’s work force shrunk by about 10 percent. The new contract will cost City Hall slightly more than $2 million in additional expenses. With increases in bed, sales, and property taxes all exceeding projections, city administrators say the additional costs can be absorbed.