The city planned to start this spring on a 2.2-mile stretch of the pathway, which will eventually be part of a 7.5-mile greenway that will run from the city’s border with Naugatuck through to the line with Thomaston. Now, Mayor Neil M. O’Leary said he expects to begin work in mid-June. On Nov. 19, the city opened bids from 20 companies vying to build the first phase of the greenway, which will begin at the Naugatuck line, along with a new riverside park along Platts Mills Road. Bids for the work ranged between $4.6 million and $8.6 million. The city’s Board of Aldermen agreed to borrow $9.5 million for Phase I of the Naugatuck River Greenway in 2017. At the time aldermen were told construction would begin in spring 2019.