According to a CBS Sports report, Bush will accuse the city of "gross negligence given the potential danger of having such a slippery surface abut the playing field."
Bush suffered the knee injury when he slipped and fell on concrete near the field at the Edward Jones Dome.
Bush hired Shawn Holley and KWIKA law firm in the suit. The city of St. Louis owns and operates the Dome.
Bush will receive a $1.6 million base salary and $500,000 roster bonus, but won't be eligible to receive $18,750 in game bonuses while on injured reserve.
Reggie Bush injured after slipping and falling in St. Louis: pic.twitter.com/8yfBLROXB1— Deadspin (@Deadspin) November 1, 2015
The injury occurred when Bush was returning a punt Nov. 1 in a 27-6 loss against the Rams. On the play, Bush received the ball and sped toward the sideline, where he was pushed out of bounds, but did not slow down.
Bush, 30, had rushed for just 28 yards on eight carries and had four catches for 19 yards this season. Last week, the running back went under for surgery.
#49ers RB Reggie Bush is believed to have suffered a torn ACL, sources say. He'll have an MRI to confirm. Very rough.— Ian Rapoport (@RapSheet) November 1, 2015
The Rams have "informed the NFL and the city of St. Louis they want changes made to the concrete area behind the benches before their next home game," according to FOX Sports.