9 Va. Admin. Code § 25-31-230 - Calculating VPDES permit conditions

A. Permit effluent limitations, monitoring requirements, standards and prohibitions shall be established for each outfall or discharge point of the permitted facility, except as otherwise provided under 9VAC25-31-220 and subsection H of this section (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.

a. Except in the case of POTWs or as provided in subdivision 2 b of this subsection, 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. For new sources or new dischargers, actual production shall be estimated using projected production. The time period of the measure of production shall correspond to the time period of the calculated permit limitations; for example, monthly production shall be used to calculate average monthly discharge limitations.

b.

(1)

(a) 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.

(b) For the automotive manufacturing industry only, the department may establish a condition under subdivision 2 b (1) (a) of this subsection if the applicant satisfactorily demonstrates to the department at the time the application is submitted that its actual production, as indicated in subdivision 2 a of this subsection, 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.

(2) If the department establishes permit conditions under subdivision 2 b (1) of this subsection:

(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 subdivision 2 b (2) (a) of this subsection, 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; and

(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.

C. All permit effluent limitations, standards, or prohibitions for a metal shall be expressed in terms of total recoverable metal as defined in 40 CFR Part 136 unless:

1. An applicable effluent standard or limitation has been promulgated under the CWA and specifies the limitation for the metal in the dissolved or valent or total form; or

2. In establishing permit limitations on a case-by-case basis under 40 CFR 125.3, it is necessary to express the limitation on the metal in the dissolved or valent or total form to carry out the provisions of the CWA and the law; or

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

D. 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. Average weekly and average monthly discharge limitations for POTWs.

E. Discharges which are not continuous, as defined in 9VAC25-31-10, shall be particularly described and limited, considering the following factors, as appropriate:

1. Frequency;

2. Total mass;

3. Maximum rate of discharge of pollutants during the discharge; and

4. Prohibition or limitation of specified pollutants by mass, concentration, or other appropriate measure.

F. 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 technology-based permit limitations on a case-by-case basis, limitations expressed in terms of mass are infeasible because the mass of the pollutant discharged cannot be related to a measure of operation (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 additionally may be limited in terms of other units of measurement, and the permit shall require the permittee to comply with both limitations.

G. 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 to the extent necessary to meet the applicable technology-based limitation or standard, up to a maximum value equal to the influent value. Credit shall be granted only if:

a. The applicable effluent limitations and standards contained in the regulations incorporated by reference in 9VAC25-31-30 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, meets 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 for the level of pollutants in the intake water may be considered in setting water quality-based effluent limitations according to 9VAC25-31-220 D. Where a total maximum daily load has been established for the receiving waterbody and it is applicable to the discharge, it shall be considered when such effluent limitations are developed. The department may consider the presence of intake pollutants when determining either that water quality-based effluent limitations are not necessary under 9VAC25-31-220 D or that any water quality-based effluent limitations justified by 9VAC25-31-220 D will be established in a manner that does not hold the permittee responsible for removing pollutants originating in its intake water.

4. Additional monitoring may be necessary to determine eligibility for any credits and compliance with permit limits.

5. Credits 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 for technology-based effluent limitations, standards, and prohibitions if he finds that no environmental degradation will result.

a. An intake pollutant is considered to be from the same body of water as the discharge if the department finds that the intake pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee. This finding may be deemed established if:

(1) The background concentration of the pollutant in the receiving water (excluding any amount of the pollutant in the facility's discharge) is similar to that in the intake water;

(2) There is direct hydrological connection between the intake and discharge points; and

(3) Water quality characteristics (e.g., temperature, pH, hardness) are similar in the intake and receiving waters.

Other site-specific factors relevant to the transport and fate of the pollutant may be considered in making this finding.

b. An intake pollutant from groundwater may be considered to be from the same body of water if the department determines that the pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee, except that such a pollutant is not from the same body of water if the groundwater contains the pollutant partially or entirely due to human activity, such as industrial, commercial, or municipal operations, disposal actions or treatment processes.

c. For pollutants in intake water provided by a water supply system, where the raw water supply is removed from the same body of water as the discharge, the concentration of the intake pollutant shall be determined at the point where the water enters the water supplier's distribution system.

d. Where a facility discharges intake pollutants that originate in part from the same body of water and in part from a different body of water, the effluent limitation may provide for intake credits for the portion of the pollutants derived from the same body of water, provided that adequate monitoring to determine compliance can be established and is included in the permit.

6. Credits shall not be granted if the discharger contributes to the level of the pollutant in the intake water prior to the intake.

7. Credits for intake pollutants do not apply to technology-based limitations on the discharge of raw water clarifier sludge generated from the treatment of intake water.

H. Internal waste streams.

1. 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 9VAC25-31-220 I shall also be applied to the internal waste streams.

2. Limits on internal waste streams will be imposed only when the fact sheet sets forth the exceptional circumstances which make such limitations necessary, such as when the final discharge point is inaccessible, 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.

I. Disposal of pollutants into wells, POTWs or by land application.

1. When part of a discharger's process wastewater is not being discharged into surface waters or into the contiguous zone because it is disposed into a well, into a POTW, or by land application thereby reducing the flow or level of pollutants being discharged into surface waters, applicable effluent standards and limitations for the discharge in a VPDES permit shall be adjusted to reflect the reduced raw waste resulting from such disposal. Effluent limitations and standards in the permit shall be calculated by one of the following methods:

a. If none of the waste from a particular process is discharged into surface waters, and effluent limitations guidelines provide separate allocation for wastes from that process, all allocations for the process shall be eliminated from calculation of permit effluent limitations or standards.

b. In all cases other than those described in subdivision 1 a of this subsection, effluent limitations shall be adjusted by multiplying the effluent limitation derived by applying effluent limitation guidelines to the total waste stream by the amount of wastewater flow to be treated and discharged into surface waters, and dividing the result by the total wastewater flow. Effluent limitations and standards so calculated may be further adjusted to make them more or less stringent if discharges to wells, publicly owned treatment works, or by land application change the character or treatability of the pollutants being discharged to receiving waters. This method may be algebraically expressed as:

P =	E x N
	T

where P is the permit effluent limitation, E is the limitation derived by applying effluent guidelines to the total wastestream, N is the wastewater flow to be treated and discharged to surface waters, and T is the total wastewater flow.

2. Subdivision 1 of this subsection does not apply to the extent that promulgated effluent limitations guidelines:

a. Control concentrations of pollutants discharged but not mass; or

b. Specify a different specific technique for adjusting effluent limitations to account for well injection, land application, or disposal into POTWs.

3. Subdivision 1 of this subsection does not alter a discharger's obligation to meet any more stringent requirements established in the permit.

Notes

9 Va. Admin. Code § 25-31-230

Derived from Virginia Register Volume 12, Issue 20, eff. July 24, 1996; amended, Virginia Register Volume 16, Issue 25, eff. September 27, 2000; Volume 18, Issue 9, eff. February 15, 2002; Volume 28, Issue 10, eff. February 15, 2012; Amended, Virginia Register Volume 39, Issue 4, eff. 11/9/2022.

Statutory Authority: § 62.1-44.15 of the Code of Virginia; § 402 of the federal Clean Water Act; 40 CFR Parts 122, 123, 124, 403, and 503.