Section R. 323.1219 - Whole effluent toxicityRule 1219.
(1) For the purpose of evaluating the need for whole effluent toxicity (WET) limits or conditions in point source discharges, the narrative WET standard specified in R 323.1057(6) shall be interpreted as follows:(a) An effluent shall not exceed 1.0 acute toxic unit (TUa), unless a higher level is acceptable consistent with R 323.1082(1).(b) An effluent shall not cause or contribute to an exceedance of 1.0 chronic toxic unit (TUc) in the surface waters of the state outside of any department-approved mixing zone.(2) If the department determines under subrule (4) of this rule that the WET of an effluent is or may be discharged at a level that will cause or contribute to an excursion above the narrative WET standard specified in R 323.1057(6), then the department shall implement all of the following provisions: (a) Establish a WET limitation or limitations consistent with subrule (5) of this rule, except as provided in subdivision (d) of this subrule, to assure both of the following: (i) Attainment of the acute WET provisions of subrule (1)(a) of this rule.(ii) Attainment of the chronic WET provisions of subrule (1)(b) of this rule.(b) Specify, in the national pollutant discharge elimination system (NPDES) permit for existing dischargers, on a case-by-case basis, a requirement to perform a toxicity reduction evaluation if representative toxicity data indicate persistent exceedance of the WET limitation.(c) Allow, with respect to any WET limitation established under subdivision (a) of this subrule, an appropriate schedule of compliance consistent with R 323.1217.(d) Decide, on a case-by-case basis, if a WET limitation is not necessary if the department determines that chemical-specific effluent limits are sufficient to ensure compliance with any of the conditions specified in subrule (1) of this rule.(3) If the department has insufficient information to determine, under subrule (4) of this rule, whether the WET of an effluent will be discharged at a level that will cause or contribute to an excursion above the narrative WET standard specified in R 323.1057(6), then both of the following may be included in the permit: (a) WET testing requirements to generate the data needed to adequately characterize the toxicity of the effluent to aquatic life and any toxicity reduction requirements needed to meet the requirement of subrule (1) of this rule.(b) A permit reopener clause to establish WET limits if any toxicity testing data required under subdivision (a) of this subrule indicate that the WET of an effluent is discharged at levels that will cause or contribute to an excursion above any of the conditions specified in subrule (1) of this rule.(4) The department shall take into account the factors described in the permit condition regulations set forth in 40 C.F.R. §122.44(d)(1)(ii), which are adopted by reference in R 323.1221, and use representative data to evaluate the WET of an effluent. All of the following provisions for evaluating the reasonable potential of an effluent to exceed the requirements of R 323.1057(6) shall be applied: (a) The toxicity of the effluent shall be characterized consistent with all of the following provisions: (i) The results of acute toxicity tests collected within the same day for each species shall be averaged to represent 1 daily value. The maximum of all representative daily values for the most sensitive species tested shall be used for acute reasonable potential determinations.(ii) The results of chronic toxicity tests collected within the same calendar month for each species shall be averaged to represent 1 monthly value. The maximum of all representative monthly values for the most sensitive species tested shall be used for chronic reasonable potential determinations.(iii) If data exist for either acute WET or chronic WET, but not for both endpoints, then toxicity values for missing endpoints may be estimated using a default acute-chronic ratio (ACR) of 10.(iv) For purposes of deriving the daily acute and monthly chronic values in paragraphs (i) and (ii) of this subdivision, toxicity tests that do not yield quantifiable results (e.g.[GREATER THAN EQUAL TO] 1.0 TUA or TUC) shall be assigned a value of zero.(b) The WET of an effluent is or may be discharged at a level that will cause or contribute to an excursion above the acute narrative standard specified in R 323.1057(6) when: (TUA effluent)(MF) > acute PEL
Where: "TUA effluent" is the maximum of the daily values determined pursuant to subdivision (a)(i) of this subrule.
"MF" is the multiplying factor determined using the acute toxicity test results for the most sensitive species as specified in subdivision (a)(i) of thissubrule. If none of the acute toxicity tests yield quantifiable results, then the MF shall be 1. Where there is at least 1 but fewer than 10 acute toxicity tests with quantifiable results, the multiplying factor taken from table 5 shall be based on a coefficient of variation (CV) of 0.6. Where there are 10 or more acute toxicity tests with quantifiable results, the multiplying factor taken from table 5 shall be based on a CV calculated as the standard deviation of the acute toxicity test results divided by the arithmetic mean of those test results. For the purpose of selecting a MF from table 5, "n" shall equal the total number of quantifiable and nonquantifiable acute toxicity test results. For the purpose of developing a calculated CV, acute toxicity tests that do not yield quantifiable results shall equal 1.0 TUa. If the calculated CV is [LESS THAN EQUAL TO]0.05, then the MF shall be 1.
"Acute PEL" is the preliminary acute wet limitation derived for the facility under subrule (5)(c) of this rule.
(c) The WET of an effluent is or may be discharged at a level that will cause or contribute to an excursion above the chronic narrative standard specified in R 323.1057(6) when: (TUC effluent)(MF) >
chronic PEL
Where:
"TUC effluent" is the maximum of the monthly values determined pursuant to subdivision (a)(ii) of this subrule.
"MF" is the multiplying factor determined using the chronic toxicity test results for the most sensitive species as specified in subdivision (a)(ii) of this subrule. If none of the chronic toxicity tests yield quantifiable results, then the MF shall be 1. Where there is at least 1 but fewer than 10 chronic toxicity tests with quantifiable results, the multiplying factor taken from table 5 shall be based on a coefficient of variation (CV) of 0.6. Where there are 10 or more chronic toxicity tests with quantifiable results, the multiplying factor taken from table 5 shall be based on a CV calculated as the standard deviation of the chronic toxicity test results divided by the arithmetic mean of those test results. For the purpose of selecting a MF from table 5, "n" shall equal the total number of quantifiable and nonquantifiable chronic toxicity test results. For the purpose of developing a calculated CV, chronic toxicity tests that do not yield quantifiable results shall equal 1.0 TUc. If the calculated CV is [LESS THAN EQUAL TO]0.05, then the MF shall be 1.
"Chronic PEL" is the preliminary chronic wet limitation derived for the facility under subrule (5)(a) or (b) of this rule.
(d) The WET of a new discharge shall be evaluated on a case-by-case basis considering all information available on the potential toxicity of the proposed discharge. (5) WET limitations shall be developed using all of the following provisions: (a) Chronic WET limitations for discharges to lotic waters shall be developed as follows: Click Here To View Image
Where:
W = the condition specified in subrule (1)(b) of this rule.
Qe = effluent design flow, which is the annual average design flow for municipalities and maximum authorized flow for other facilities, unless it can be demonstrated to the department that an alternate design flow is appropriate.
Qr = flow of the receiving water allocated for mixing under R 323.1082. If a discharger has an intake upstream of the point of discharge, then Qr shall reflect the reduction in design flow attributable to the intake.
(b) Chronic WET limitations for discharges to the Great Lakes and inland lakes shall be developed as follows:WET limit = (W)(Q + 1) Where:
W = the condition specified in subrule (1)(b) of this rule.
Q = the number of parts receiving water allowed for mixing under R 323.1082(5).
(c) Acute WET limitations shall not exceed the condition specified in subrule (1)(a) of this rule.(d) WET limitations for facilities with overlapping mixing zones shall be evaluated on a case-by-case basis.(e) For purposes of an NPDES permit, WET limitations shall be expressed as follows: (i) An acute WET limitation shall be applied as a daily maximum and expressed in TUa.(ii) A chronic WET limitation shall be applied as a monthly average and expressed in TUc. (6) Monitoring frequency to evaluate compliance with WET limitations shall be established by the department on a case-by-case basis. Concerns with the effects of temperature and pH on ammonia toxicity under laboratory conditions during cold weather months will be considered in establishing monitoring frequency. Click here to view image
Mich. Admin. Code R. 323.1219