Early estimates to rebuild River Road, part of which collapsed into the Housatonic River late last month due to flooding, are between $10 million and $20 million, and possibly higher, town officials say. First Selectman Jeffrey A. Manville was forced to close the road indefinitely Oct. 5 after a 200-foot section of the southbound lane washed away, sliding down a steep cliff and into the river due to record rainfall. Engineers are now determining what steps are needed to fix the road and whether larger sections also need rebuilding. Manville said the town’s public works department has been addressing River Road for years, including drainage issues and paving.