To enable the Agency to inspect and investigate under Section 4(d) of the Act, all effluent discharge sewers, pipes or outfalls must be designed or modified so that a sample of the effluent can be obtained at a point after the final treatment process and before discharge to or mixing with any waters of the State. All treatment works must include devices for taking samples and for measuring and recording effluent flow as the Agency may reasonably require.
Ill. Admin. Code tit. 35, § 305.103