250 R.I. Code R. 250-RICR-150-10-1.18

Current through December 26, 2024

Section 250-RICR-150-10-1.18 - Calculating RIPDES Permit Conditions

A. Outfalls and discharge points. All permit effluent limitations, standards, and prohibitions shall be established for each outfall or discharge point of the permitted facility, except as otherwise provided under § 1.16(G) of this Part (BMPs where limitations are infeasible) and § 1.18(K) of this Part (limitations on internal waste streams).

B. Production-Based Limitations

1. In the case of POTWs, permit effluent limitations, standards or prohibitions shall be calculated based on design flow.

2. Except in the case of POTWs, calculation of any permit limitations, standards, or prohibitions which are based on production (or other measure of operation) shall be based not upon the designed production capacity but rather upon a reasonable measure of actual production of the facility, such as the production during the high month of previous year, or the monthly average for the highest of the previous five years. For new sources or new discharges, actual production shall be estimated using projected production. The time period for calculating permit limitations, for example, monthly production, shall be used to calculate average monthly discharge limitations.

3. The Department may include a condition establishing alternate permit limitations, standards, or prohibitions based upon anticipated increased (not to exceed maximum production capability) or decreased production levels.

C. For the automotive manufacturing industry only, the Department may establish a condition under § 1.18(B)(3) of this Part if the applicant satisfactorily demonstrates to the Department at the time the application is submitted that its actual production, as indicated in § 1.18(B)(2) of this Part, is substantially below maximum production capability and that there is a reasonable potential for an increase above actual production during the duration of the permit.

1. If the Department establishes permit conditions under § 1.18(B)(3) of this Part:

a. The permit shall require the permittee to notify the Department at least two business days prior to a month in which the permittee expects to operate at a level higher than the lowest production level identified in the permit. The notice shall specify the anticipated level and the period during which the permittee expects to operate at the alternate level. If the notice covers more than one month, the notice shall specify the reasons for the anticipated production level increase. New notice of discharge at alternate levels is required to cover a period or production level not covered by prior notice or, if during two consecutive months otherwise covered by a notice, the production level at the permitted facility does not in fact meet the higher level designated in the notice.

b. The permittee shall comply with the limitations, standards, or prohibitions that correspond to the lowest level of production specified in the permit, unless the permittee has notified the Department under § 1.18(C)(1)(a) of this Part, in which case the permittee shall comply with the lower of the actual level of production during each month or the level specified in the notice.

c. The permittee shall submit with the DMR the level of production that actually occurred during each month and the limitations, standards, or prohibitions applicable to that level of production.

D. Metals. All permit effluent limitations, standards, or prohibitions for a metal shall be expressed in terms of the total metal (that is, the sum of the dissolved and suspended fractions of the metal) unless:

1. An applicable effluent standard or limitation has been promulgated under the Federal or State Acts and specifies the limitation for the metal in the dissolved or valent forms; or

2. In establishing permit limitations on a case-by-case basis under 40 C.F.R. § 125.3, incorporated above at § 1.3(B) of this Part, it is necessary to express the limitation on the metal in dissolved or valent form in order to carry out the provisions of the R.I. Water Pollution Act, R.I. Gen. Laws Chapter 46-12 and 33 U.S.C. 1251, et seq (the Clean Water Act).

3. All approved analytical methods for the metal inherently measure only its dissolved form (e.g., hexavalent chromium).

E. Continuous discharges. For continuous discharges all permit effluent limitations, standards, and prohibitions, including those necessary to achieve water quality standards, shall unless impracticable be stated as:

1. Maximum daily and average monthly discharge limitations for all dischargers other than publicly owned treatment works; and

2. Maximum daily, average weekly and average monthly discharge limitations for POTWs.

F. Non-continuous discharges. Discharges which are not continuous shall be particularly described and limited, considering the following factors, as appropriate:

1. Frequency (for example, a batch discharge shall not occur more than once every 3 weeks);

2. Total mass (for example, not to exceed 100 pounds of zinc and 200 pounds of chromium per batch discharge);

3. Maximum rate of discharge of pollutants during the discharge (for example, not to exceed 2 pounds of zinc per minute); and

4. Prohibition or limitation of specified pollutants by mass, concentration, or other appropriate measure (for example, shall not contain at any time more than 0.1 mg/l zinc or more than .25 pounds of zinc in any discharge).

G. Non-continuous discharges. Discharges which are not continuous shall be particularly described and limited, considering the following factors, as appropriate:

1. Frequency (for example, a batch discharge shall not occur more than once every 3 weeks);

2. Total mass (for example, not to exceed 100 pounds of zinc and 200 pounds of chromium per batch discharge);

3. Maximum rate of discharge of pollutants during the discharge (for example, not to exceed 2 pounds of zinc per minute); and

H. Mass Limitations

1. All pollutants limited in permits shall have limitations, standards, or prohibitions expressed in terms of mass except:

a. For pH, temperature, radiation, or other pollutants which cannot appropriately be expressed by mass;

b. When applicable standards and limitations are expressed in terms of other units of measurement; or

c. If in establishing permit limitations on a case-by-case basis under 40 C.F.R. § 125.3, incorporated above at § 1.3(B) of this Part, limitations expressed in terms of mass are infeasible because the mass of the pollutant discharged cannot be related to a measure of operations (for example, discharges of TSS from certain mining operations), and permit conditions ensure that dilution will not be used as a substitute for treatment.

2. Pollutants limited in terms of mass may additionally be limited in terms of other units of measurement, and the permit shall require the permittee to comply with both limitations.

I. Pollutants in Intake Water

1. Upon request of the discharger, technology-based effluent limitations or standards shall be adjusted to reflect credit for pollutants in the discharger's intake water if:

a. The applicable effluent limitations and standards contained in 40 C.F.R. Chapter I, Subchapter N, incorporated above at § 1.3(B) of this Part, specifically provide that they shall be applied on a net basis; or

b. The discharger demonstrates that the control system it proposes or uses to meet applicable technology-based limitations and standards would, if properly installed and operated, meet the limitations and standards in the absence of pollutants in the intake waters.

2. Credit for generic pollutants such as biochemical oxygen demand (BOD) or total suspended solids (TSS) should not be granted unless the permittee demonstrates that the constituents of the generic measure in the effluent are substantially similar to the constituents of the generic measure in the intake water or unless appropriate additional limits are placed on process water pollutants either at the outfall or elsewhere.

3. Credit shall be granted only to the extent necessary to meet the applicable limitation or standard, up to a maximum value equal to the influent value. Additional monitoring may be necessary to determine eligibility for credits and compliance with permit limits.

4. Credit shall be granted only if the discharger demonstrates that the intake water is drawn from the same body of water into which the discharge is made. The Department may waive this requirement if he finds that no environmental degradation will result.

5. This section does not apply to the discharge of raw water clarifier sludge generated from the treatment of intake water.

J. Net Limitations

1. Upon request of the discharger, effluent limitations or standards imposed in a permit shall be calculated on a "net" basis; that is, adjusted to reflect credit for pollutants in the discharger's intake water, if the discharger demonstrates that its intake water is drawn from the same body of water into which the discharge is made and if:

b. The discharger demonstrates that pollutants present in the intake water will not be entirely removed by the treatment systems operated by the discharger; and

2. The permit conditions requiring:

a. The permittee to conduct additional monitoring (for example, for flow and concentration of pollutants) as necessary to determine continued eligibility for and compliance with any such adjustments; and

b. The permittee to notify the Department if eligibility for an adjustment under this section has been altered or no longer exists. In that case, the permit may be modified.

3. Permit effluent limitations or standards adjusted under this paragraph shall be calculated on the basis of the amount of pollutants present after any treatment steps have been performed on the intake water by or for the discharger. Adjustments under this paragraph shall be given only to the extent that pollutants in the intake water which are limited in the permit are not removed by the treatment technology employed by the discharger.

4. In addition, effluent limitations or standards shall not be adjusted to the extent that the pollutants in the intake water vary physically, chemically, or biologically from the pollutants limited in the permit. Nor shall effluent limitations or standards be adjusted to the extent that the discharger or standards be adjusted to the extent that the discharger significantly increases concentrations of pollutants in the intake water, even though the total amount of pollutants might remain the same.

5. This subsection shall apply to dischargers to surface or ground water only if the discharger demonstrates to the satisfaction of the Department that the discharger is not responsible for the background pollutants present in the intake water.

K. Internal Waste Streams

A. When permit effluent limitations or standards imposed at the point of discharge are impractical or infeasible, effluent limitations or standards for discharges of pollutants may be imposed on internal waste streams before mixing with other waste streams or cooling water streams. In those instances, the monitoring required by § 1.14(K)(2) of this Part shall also be applied to the internal waste streams.

B. Limits on internal waste streams will be imposed only when the fact sheet under § 1.40 of this Part sets forth the exceptional circumstances which make such limitations necessary, such as when the final discharge point is inaccessible (for example, under 10 meters of water), the wastes at the point of discharge are so diluted as to make monitoring impracticable, or the interferences among pollutants at the point of discharge would make detection or analysis impracticable.

L. Disposal of pollutants into wells, into POTWs, or by land applications. Permit limitations and standards shall be calculated as provided in § 1.19 of this Part.

M. Water quality based effluent limitations applicable to discharge into the surface waters of the State shall be developed in accordance with Rhode Island "Water Quality Regulations" as amended.

N. The limitation assigned to the toxic substances shall be established such that the effluent standard for toxic discharges, as set forth in 40 C.F.R. § 125.3, incorporated above at § 1.3(B) of this Part, is not exceeded.

1. In-stream concentrations of discharged pollutants shall be determined by the following formulas, or other methods which may be found to be acceptable.

a. For effluent discharges into surface waters of the State with essentially one dimensional flow (stream discharge):

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where, CX = in-stream concentration of pollutants, downstream of the discharge

C_E = concentration of the pollutant in the effluent

Q_E = effluent discharge flow rate

C_U = concentration of the pollutant in the receiving stream, immediately upstream of the discharge

Q_U = the seven day, 10 year, low flow of the receiving stream immediately upstream of the discharge

2. For effluent discharges into surface waters of the State with essentially multi-dimensional flow:

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where, F = Froude number

vj = jet velocity (ft./sec.)

S = difference in specific gravity between the surrounding seawater.

S = Specific gravity of the waste

g = acceleration due to gravity (ft./sec.2)

D = discharge jet diameter (ft.)

The initial dilution, D1, is a function of the Froude number, F, the depth of the discharge port, Y, and the diameter of the discharge port, d. The dilution factor is determined using the curves shown in § 1.70 of this Part, Figure 1.

Secondary dispersion of the effluent will be determined using § 1.70 of this Part, Figure 2 where:

D2 = dilution due to dispersion after initial dilution

V = current velocity (ft./sec.)

3. Where a total maximum daily load has been developed for a pollutant in a given stream segment, effluent limitations for that pollutant shall be determined by calculating waste load allocations for individual dischargers within that stream segment, instead of by the methods outlined in this section.

250 R.I. Code R. 250-RICR-150-10-1.18