Section 304.104  Averaging

a)         Except as otherwise specifically provided, proof of violation of the numerical standards of this Part shall be on the basis of one or more of the following averaging rules:

1)         No monthly average shall exceed the prescribed numerical standard.

2)         No daily composite shall exceed two times the prescribed numerical standard.

3)         No grab sample shall exceed five times the prescribed numerical standard.

b)         Terms used in subsection (a) shall have the following meanings:

1)         The monthly average shall be the numerical average of all daily composites taken during a calendar month.  A monthly average must be based on at least three daily composites.

2)         A daily composite shall be the numerical average of all grab samples, or the result of analysis of a single sample formed by combining all aliquots, taken during a calendar day.  A daily composite must be based on at least three grab samples or three aliquots taken at different times.

3)         A grab sample is a sample taken at a single time.  Aliquots of a daily composite are grab samples only if they are analyzed separately.

c)         Subsection (a) establishes a method of interpretation of the effluent standards of this Part.  The Agency shall consider the averaging rule in deciding whether an applicant has demonstrated that a facility complies with this Part for purposes of permit issuance and in writing the effluent standards into permit conditions.  Reporting and monitoring requirements are established by way of permit condition pursuant to 35 Ill. Adm. Code 305.102 and 309.146.

d)         Proof of violation of effluent limitations contained in permits shall be based on the language of the permit.

(Source:  Amended in R88-1 at 13 Ill. Reg. 5976, effective April 18, 1989)