Managers at Mercy Hospital say plans to expand its Fore River facility are still on track, despite a downgrade on the bond rating of its parent company, Eastern Maine Healthcare Systems. Moody’s Investors Service lowered the system’s bond rating to  junk bond status Thursday, indicating it’s a risky investment for institutional investors. EMHS had a $34.3 million operating loss in 2016. The expansion is expected to start in 2021.