A concrete median will stop illegal left-turns from 12th Street onto northbound Tracy Boulevard as part of a $1.4 million boulevard renovation expected to begin in September.

Granite Construction project manager Frank Grande said traffic would be detoured as his company spends three months overhauling Tracy Boulevard between 12th Street and Grant Line Road, and a stretch north of Larch Road.

“There might be minor temporary detours, but overall it’ll just be traffic control and flaggers as required,” he said.

Tracy civil engineer Zabih Zaca said the work would improve wheelchair ramps and replace water valves, curbs, gutters and sidewalks damaged by growing tree roots.

Zaca said the city had planned the work for the last two or three years.

Mayor Dan Bilbrey said all of Tracy’s older main north-south streets except Bessie Avenue had been reconstructed or repaved during the past 10 years.

Granite Construction’s facelift of the corner of Central Avenue and 10th Street, which was finished earlier this year, cost the city $1.5 million more than the original $6.7 million agreement.