Execution Of The Works Of The Replacement Project And Execution Of Enclosures In The Scope Of The Conventional Network. Northwest Subdirectorate. Line 752 Laviana To Gijón-Sanz Crespo Between Pp.Kk 46/290 And 48/616; Line 770 Santander To Oviedo Between Pp.Kk. 317/729 And 322/346.