Dear Hernan
only some minor add on: same question has been asked a lot on the same level of detail. I would assume that time line for project is more like 12 month than 6. This depends on factors as: is there a "legacy" system content to transfer? How to populate the SAP EHS system? by user? by upload etrc.
Document
SAP EHS Management for Beginners
list some similar threads.
C.B.