MARBLEHEAD – Selectmen unanimously awarded the contract for the Marblehead Causeway seawall repair project Monday evening 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 Aug. 31. 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 said the total budget for the project would probably be $7.5 million, which is still $1.2 million less than originally estimated.