Top Guard Truncated Domes for FDOT T3398 in Fort Walton Beach (Okaloosa County) June 13, 2016 Posted by on June 13, 2016June 20, 2017 Fort Walton beach in Okaloosa County has Top Guard yellow detectable warnings installed. +/-160 sq.ft. along SR 189. FDOT contract T3398. Anderson Columbia as prime.