Ill. Admin. Code tit. 35 § 370.730
All settling tanks shall be equipped to enhance safety for operators. Such features shall appropriately include machinery covers, life lines, stairways, walkways, handrails and slip-resistant surfaces. If sidewalls are extended more than three feet above the liquid level or four feet above ground level, convenient walkways must be provided to facilitate housekeeping and maintenance.
The design shall provide for convenient and safe access to routine maintenance items such as gear boxes, scum removal mechanisms, baffles, weirs, inlet stilling baffle area, and effluent channels.
Electrical fixtures and controls in enclosed settling basins shall meet the requirements of the National Electric Code for Class I, Group D, Division 1 locations. The fixtures and controls shall be located so as to provide convenient and safe access for operation and maintenance. Adequate area lighting shall be provided.
Ill. Admin. Code tit. 35, § 370.730