Catholic Healthcare West and Service Employees International Union reached a tentative agreement on a new contract late Sunday, ending nine months of talks. CHW, which has 2,700 employees at its five Mercy hospitals in the Sacramento region, averted a possible strike with the deal. SEIU’s 16,000 represented employees – including many in the Bay Area – will vote later this week on the contract with an average 26 percent wage increase over four years, according to union officials. CHW and the union reached an agreement after 22 hours of negotiations that started Saturday after workers approved a possible strike 10 days ago.