Tutor Perini Corp. announced Friday that its joint venture with Frontier-Kemper has won a contract to build tunnels for Los Angeles County Metropolitan Transportation Authority’s Purple Line Extension project. The contract is worth about $410 million. Called the Extension Section 3 Tunnels Project, it involves the design and construction of twin bored tunnels for subway service between Century City and the Veterans Administration hospital in Westwood, a distance of 2.6 miles. Tutor Perini, a Sylmar construction company, is currently working on the Purple Line Extension Section 2 Project, which includes tunneling and construction of new stations in Beverly Hills and Century City. The company expects Metro will formally award the contract in the next 30 to 60 days, with notice to begin construction soon thereafter. Completion of the project is planned for the summer of 2022. Shares of Tutor Perini (TPC) closed Friday down 35 cents, or 1.8 percent, to $18.90 on the New York Stock Exchange.