ST. PETERSBURG — Construction of ONE St. Petersburg, a 41-story condo tower in the heart of downtown, will start sooner than expected because of strong sales. The Kolter Group said Monday that infrastructure and foundation work already have begun on the site at 100 1st Avenue N., which will become St. Petersburg's tallest building and one of the tallest on Florida's west coast. A formal groundbreaking on the 253-unit tower and adjacent Hyatt hotel is scheduled for early next year.The decision to speed up the timetable was prompted by more than $85 million in confirmed contracts."We are thrilled with the success of ONE St. Petersburg,'' Bob Vail, president of Kolter Urban, said in a release Monday. "By accelerating the construction start, we create certainty for the project in two key areas: the ability to lock in construction costs and most importantly, we create certainty in the delivery of the project for all of our current and future buyers."The release did not say how many units are under contract in the condo tower, where prices start in the $500,000 range and go to more than $3 million. Last spring, buyers were offered 10 percent off the total price and no condo association dues for a year if they converted to contracts by the end of May. The 174-room Hyatt is expected to be finished late next year while the condos should be ready for occupancy by late 2018.During construction, Kolter estimates, the project will employ between 350 and 500 workers and generate more than $90 million in wages and other economic benefits for Tampa Bay businesses. Once the tower and hotel are finished, they are expected to have 150 full-time employees and increase property tax revenues by more than $5.5 million annually.ONE St. Petersburg, which will include extensive retail space, will be the third sizable new condo project in downtown St. Petersburg. Construction has already begun on Bliss, a 29-unit, 17-story tower on Fourth Avenue NE just off of Beach Drive; and the Salvador, a 74-unit mid-rise at 199 Dali Blvd. S near the Salvador Dalí Museum. Smith & Associates is handling sales for all three projects. Kolter, based in Palm Beach County, developed the recently completed Water Club condos on Snell Isle and is developing a Westin hotel in Sarasota. Contact Susan Taylor Martin @[email protected] or (727) 893-8642. Follow @susanskate.