Md. Code, Local Government § 21–633

(a) Except as provided in subsection (b) of this section, the county where the

project is located shall maintain every stormwater management system and part of

every system that:

(1) was constructed by the Commission or the county or accepted for

maintenance by the Commission or the county; and

(2) is located in a street, an alley, a public way, or a public space.

(b) Unless the county agrees otherwise:

(1) a stormwater management system that is located on real property

owned by the Maryland–National Capital Park and Planning Commission shall be

maintained by the Maryland–National Capital Park and Planning Commission; and

(2) a stormwater management system or facility that is located in a

road maintained by the State Highway Administration shall be maintained by the

State.