No, you cannot put "was" there.
If you use "was", you have to put 'that' or 'which' before "was". The waterway, formerly a scenic attraction that was famous for its aquatic life, has been badly contaminated by industrial, agricultural and domestic wastes.
Say, 'Is a 'to be' verb needed........?. You have to say 'Is a verb...?' or 'Are verbs...?'.