Flooding problems around Union Square could cost as much at $10 million to fix, according to Somerville officials. The Board of Aldermen’s Flood Forum Special Committee is considering a proposal that calls for the Public Works Department to conduct a study of Dane Avenue’s flooding problems. Public Works Commissioner Stanley Koty previously told the committee the problems on that street can be attributed to Union Square’s outdated water and sewer infrastructure, and that the city planned to hire a consultant to review the area’s drainage system, which needs to have storm-water runoff separated from its drainage system. But Koty told alderman that it could cost $10 million to address the problem areas, according to city records. The Flood Forum Special Committee meets Nov. 26 at 6 p.m. at City Hall.