Transforming an empty Waikiki retail building that was once anchored by a NikeTown store into a seven-story hotel is projected to begin in 2018 and be complete in mid-2020.

The developer of the project provided the timetable in a draft environmental assessment published by the state Saturday, and estimated that converting the four-story complex called King Kalakaua Plaza will cost $85 million.

Robertson Properties Group shared its conceptual plan in October for the 230-room extended-stay hotel on the block bordered by Kalakaua Avenue, Olohana Street, Kuhio Avenue and Kalaimoku Street.

King Kalakaua Plaza was built in 1998 for about $45 million and initially housed NikeTown, Banana Republic and The All Star Cafe restaurant and bar. The last tenant departed in 2009.

Planned changes to the property, which has roughly 200 basement parking stalls, include adding a fourth-floor pool deck and three new levels.

More details of the plan can be found in the draft environmental assessment at health.hawaii.gov/oeqc online. Public comments on the plan may be submitted until May 8 and be sent to city Department of Planning and Permitting planner Joette Yago at jyago@honolulu.gov with copies to the developer’s consultant Tom Schnell at tschnell@pbrhawaii.com.