MARBLEHEAD – The replacement of the Marblehead Causeway seawall has begun. Drive accordingly.The project, which is expected to last until June 27, began on the mainland (West) side of the Causeway last week and will progress toward Marblehead Neck.Police are using temporary signaling to cordon off a 350-foot work area along the southern side of Ocean Avenue. The signals will operate 24 hours a day, seven days a week, and will follow the major construction area as it progresses along the roadway.Optical sensors on the signals will assure quick passage for emergency vehicles. Police details will be used as necessary.Selectmen awarded the contract for the project at their first September meeting to PIHL and RDA Limited Liability Corp., which filed a joint bid of $6.36 million. The bid was the second lowest the town received and PIHL and RDA were referred to as the lowest responsible bidders. Selectmen also approved a contract with Vine Associates of Hingham to manage the project, at a cost of $139,000.Town Administrator Tony Sasso estimated the total budget for the project at $7.5 million, which is $1.2 million less than originally estimated.Thirty-seven companies expressed interest in the project. Town Meeting and a special debt exclusion override election approved an $8.7 million bond issue to cover the cost of the project.