7 Del. Admin. Code § 7201-8.0

Current through Register Vol. 28, No. 7, January 1, 2025

Section 7201-8.0 - Water Quality Based Requirements

8.1 General. In the event that Delaware Surface Water Quality Standards are not achieved through application of the technology based requirements of § 7.0, additional effluent limitations and treatment requirements shall be imposed to assure compliance with the Surface Water Quality Standards. Such additional effluent limitations and treatment requirements must control all pollutants or pollutant parameters which the Department determines are or may be discharged at a level which will cause, have the reasonable potential to cause or to contribute to an excursion of any numerical or narrative water quality criterion contained within Delaware's Surface Water Quality Standards. The need for additional effluent limitations and treatment requirements shall be based upon the results of chemical and/or biological tests in conjunction with studies or analyses designed to assess the potential of the discharge to cause or contribute to in-stream excursions of Delaware's Surface Water Quality Standards. § 8.2 specifies the information and factors to be considered in determining the need for additional effluent limitations and treatment requirements for situations in which a single discharger, in and of itself, causes or has the reasonable potential to cause an excursion of Delaware's Surface Water Quality Standards. § 8.3 specifies the requirements for situations in which one or more point source discharges in combination with nonpoint sources of pollution contribute to the excursion of Delaware Surface Water Quality Standards. § 8.4 specifies special conditions and exceptions to effluent limitations and treatment requirements developed under §§ 8.2 and 8.3.

8.2 Water Quality Based Effluent Limitations for Isolated Discharges Based Upon Surface Water Quality Standards

8.2.1 In certain cases, a single discharge may be sufficiently isolated from other discharges and/or nonpoint sources of pollution such that there is no instream interaction of pollutants released from the single discharge and other point and/or nonpoint sources. In such cases, the Department shall consider the information and factors listed in 1 through 5 below in determining whether the discharge, in and of itself, causes or has the reasonable potential to cause an exceedance of numerical water quality criteria contained within Delaware's Surface Water Quality Standards. Furthermore, the development or modification of effluent limitations and treatment requirements based upon the numerical or narrative water quality criteria contained within Delaware's Surface Water Quality Standards shall appropriately reflect the information and factors listed below.

8.2.1.1 Physical, chemical, or biological data on the discharge and receiving water including, but not limited to, the ambient background concentration of pollutants or pollutant parameters in the receiving water and the documented condition of the natural species community in the receiving water;

8.2.1.2 The sensitivity of the test species to toxicity testing (when evaluating whole effluent toxicity data);

8.2.1.3 Instream dilution and dispersion of the discharged pollutant(s) or pollutant parameter(s) in the receiving water;

8.2.1.4 Variability of the pollutant(s) or pollutant parameter(s) in the discharge; and

8.2.1.5 Fate mechanisms of discharged pollutants or pollutant parameters within the receiving water as well as synergistic or antagonistic interactions and any additive impacts.

8.2.2 When it is determined, using the information and factors presented in §§ 8.2.1.1 through 8.2.1.5 that a single discharge causes or has the reasonable potential to cause an excursion of either a narrative or a numerical water quality criterion contained within Delaware's Surface Water Quality Standards, then the permit must contain effluent limitations and treatment requirements to control the pollutant or pollutant parameter. This includes effluent limitations on whole effluent toxicity where deemed appropriate.

8.2.3 Where the Department has not established a numerical water quality criterion within the State of Delaware Surface Water Quality Standards for a specific pollutant or pollutant parameter that is present in an effluent at levels which cause or have the reasonable potential to cause an excursion of a narrative water quality criterion within Delaware's Surface Water Quality Standards, the Department shall establish effluent limitations and treatment requirements on a case-by-case basis considering relevant ecological, human health effects and other pertinent data for the specific pollutant or pollutant parameter along with the information and factors listed in §§ 8.2.1.1. through 8.2.1.5.

8.2.4 When establishing any effluent limitations and treatment requirements under §§ 8.2.2 or 8.2.3, the Department shall demonstrate that such effluent limitations and treatment requirements will attain and maintain all applicable narrative and numerical water quality criteria and will fully protect the receiving waters' designated uses.

8.2.5 Any effluent limitations established by the Department under § 8.2.2 or § 8.2.3 shall be subject to the public notice and public hearing requirements of § 6.0, Part III, of these regulations and 7Del.C.Ch. 60.

8.3 Water Quality Based Effluent Limitations for One or More Discharges in Combination with Nonpoint Source Pollution

8.3.1 In areas where the State of Delaware Surface Water Quality Standards are not achieved as the result of one or more point source discharges in combination with nonpoint sources of pollution, the Department will determine the Total Maximum Daily Load (TMDL) of the pollutant or pollutant parameter which the receiving water can be expected to assimilate without violating the State of Delaware Surface Water Quality Standards. In determining the TMDL, the Department shall:

8.3.1.1 Specify the reach or zone of the waterbody and the pollutant(s) or pollutant parameter(s) for which the TMDL is being developed;

8.3.1.2 Specify the conditions under which the TMDL is being developed;

8.3.1.3 Consider the factors and information listed in §§ 8.2.1.1. through 8.2.1.5. for the individual point source(s) which discharge to the reach of interest;

8.3.1.4 Consider existing controls on the point and nonpoint sources that discharge to the reach of interest;

8.3.1.5 Specify what portion of the TMDL will be allocated to the point source discharge(s) and what portion of the TMDL will be allocated to nonpoint sources and natural background sources. The portion of the TMDL allocated to the point source discharge(s) shall be known as the Wasteload Allocation (WLA). The portion of the TMDL allocated to the nonpoint source(s) and natural background sources shall be known as the Load Allocation (LA). Wherever possible, a distinction will be made between natural and nonpoint source loads;

8.3.1.6 Consider the influence, if any, of seasonal variation on the relationship between effluent limitations and water quality; and

8.3.1.7 Provide a margin of safety for any lack of knowledge concerning the relationship between effluent limitations and water quality, including any uncertainty in mathematical models utilized to determine this relationship. In the absence of definitive information to the contrary, up to ten percent (10%) of the TMDL shall be reserved as a margin of safety.

8.3.2 When developing effluent limitations and treatment requirements for a discharge to a reach for which a TMDL has been established and approved by the EPA Regional Administrator in accordance with 40 CFR 130.7(d), the Department shall ensure that such limits or requirements are consistent with the TMDL and that portion of the Wasteload Allocation (WLA) assigned to the discharger.

8.3.3 In the case of multiple point source discharges, the wasteload allocation (i.e. that portion of the receiving water's loading capacity which is assigned to the point sources) shall be apportioned equitably among those point source discharges unless the Secretary determines that an alternative allocation scheme is a more efficient and effective means of achieving water quality objectives for the reach of interest. Alternative allocation schemes may include, but are not limited to, pollution trading agreements between one or more cooperating point source(s) and, if applicable, one or more nonpoint source(s). For such alternative allocation schemes to be considered by the Secretary, a petition and supporting documentation should be submitted to the Department which describes, at a minimum, the following items:

8.3.3.1 The identities of the point source(s) and, if applicable, nonpoint source(s) proposing to cooperate in the alternative allocation scheme;

8.3.3.2 The reach of interest over which the alternative allocation scheme is proposed;

8.3.3.3 The pollutant(s) or pollutant parameter(s) for which the alternative allocation scheme is sought;

8.3.3.4 The point(s) of discharge from the sources identified in § 8.3.2.1. to the reach of interest;

8.3.3.5 A complete description of the alternative allocation scheme between the sources identified in § 8.3.2.1, including an accounting of current and proposed pollutant loading from all cooperating sources;

8.3.3.6 An assessment of potential water quality impacts and benefits associated with the alternative allocation scheme described in § 8.3.2.5, including a comparison of projected water quality conditions to applicable water quality standards;

8.3.3.7 A description of the discharge monitoring and reporting, or other mechanism proposed to assess the success of the alternative allocation scheme;

8.3.3.8 A description of the agreement that will be used between the cooperating point source(s) and, if applicable, nonpoint source(s) in implementing the proposed alternative allocation scheme. The description should include a discussion of the financial and institutional measures that the cooperating entities propose; and

8.3.3.9 A description of corrective actions that will be taken by the cooperating point source(s) and, if applicable, nonpoint source(s) in the event that the alternative allocation scheme fails to achieve the intended water quality objectives for the reach of interest.

8.3.4 The Secretary may request any present or potential discharger(s) of any pollutant for which a TMDL is being determined under this section to supply information concerning the factors specified in this section.

8.3.5 Any TMDL established by the Department under § 8.3.1 shall be subject to the public notice and public hearing requirements of 7Del.C.Ch. 60. If the Department determines that the TMDL established under § 8.3.1 could result in a change in effluent limitations, then the public hearing(s) for the modified effluent limitations and the TMDL may be held concurrently. In such cases, the Department shall provide separate public notices for the effluent limitation change and the TMDL.

8.4 Conditions Applicable in Specified Cases

8.4.1 Requests for Increased Discharge or Change In Discharge Location

8.4.1.1 Any person who shall apply for a permit to discharge to the waters of the State, and who seeks to either (i) increase the concentration and/or mass loading of pollutants discharged, or (ii) change the discharge location to another waterbody or to an area of less favorable mixing characteristics, must demonstrate that the discharge will not result in violation of Delaware's Surface Water Quality Standards. Such demonstration shall normally take the form of appropriate monitoring, field investigation, and mathematical modeling. A public hearing, pursuant to 7Del.C.Ch. 60 may be held to gather public comment on any such application.

8.4.2 Effluent Limitations Below Quantifiable Levels

8.4.2.1 Where information is available which shows that reliable quantification at concentrations less than any effluent limitation developed in connection with §§ 8.2 and 8.3 is not feasible using analytical methods required by permit, regulation, or otherwise approved by the Department, then Minimum Analytical Levels (MAL), as defined in § 2.0, will be used as a temporary measure by the Department to determine compliance with effluent limitations.

8.4.3 Consideration for Pollutants Corroded and Eroded from Water Distribution Piping and Appurtenances or Noncontact Cooling Water Condenser Tubes

8.4.3.1 For purposes of this section, normal corrosion and erosion shall be determined through site-specific calculations that are performed in accordance with a scientifically defensible methodology, approved by the Department, and that are based on annual average intake concentrations.

8.4.3.2 Variances from Water Quality Criteria

For the purpose of establishing effluent or discharge limitations, a facility may be granted a variance from water quality criteria for pollutants contributed by normal corrosion and erosion associated with the facility's piping and appurtenances or noncontact cooling water condenser tubes where this corrosion and erosion causes or would reasonably be expected to cause exceedances in the receiving water, as outlined in § 5.4 of the State of Delaware Surface Water Quality Standards, as amended, August 11, 1999.

The variance granted in such cases applies only to the discharger requesting the variance and only to the pollutant or pollutants specified in the variance. The discharger will be required to meet the applicable criteria for all other constituents.

8.4.3.2.1 Conditions for Granting a Variance. A variance may be granted if the discharger demonstrates, based upon sound rationale and supported by substantial scientific and technical evidence and analysis, all of the following:

8.4.3.2.1.1 In the absence of pollutants corroded and eroded from the facility's water distribution piping and appurtenances, there would be no violation of the surface water quality criteria in the receiving water; and

8.4.3.2.1.2 The normal corrosion and erosion associated with the intake water used by the facility is sufficient to cause the violation. For purposes of this determination, annual average intake water characteristics shall be used in assessing normal corrosion and erosion; and

8.4.3.2.1.3 No other activity, condition or method of operation, or materials used or produced at the facility, which results in the addition oferosion and corrosion based pollutants into the facility's discharge, significantly contributes to the violations of surface water quality criteria in the receiving waters. Such activities, conditions or methods of operation, or materials used or produced at the facility include entrainment of erosion and corrosion basedpollutants previously discharged or disposed by the facility; and

8.4.3.2.1.4 No practicable alternative water supply or treatment methodology or system which would yield statistically significant lower corrosivity or erosiveness is available to the facility; and

8.4.3.2.1.5 No practicable alternative piping or appurtenances are available to the facility; i.e., implementation of the controls needed to assure compliance with the applicable water quality criteria would result in substantial and widespread economic and social impact. The analysis of economic impacts must demonstrate that:

8.4.3.2.1.5.1 The discharge would face substantial financial impacts due to the costs of the necessary pollution controls or water treatment (substantial impacts of which would interfere with development), and

8.4.3.2.1.5.2 The affected community will bear significant adverse impacts if the entity is required to meet existing or proposed water quality standards (widespread impacts of important development).

8.4.3.2.2 Duration of Variance. A variance granted under this Section shall be effective for three years or the life of the NPDES permit, and at the expiration of either time period, the discharger must meet the criteria or make a new demonstration of unattainability and financial impact. Variances considered under this section shall be subject to all applicable public participation requirements and shall be subject to review and approval by the U.S. Environmental Protection Agency.

8.4.3.3 Compliance Schedules to Meet More Restrictive Water Quality-based Effluent or Discharge Limitations for Pollutants Corroded and Eroded from the Facility's Piping and Appurtenances

Any existing permit that is reissued or modified to include new or more restrictive water quality-based effluent or discharge limitations for pollutants corroded and eroded from the facility's piping and appurtenances or noncontact cooling water condenser tubes, may allow a reasonable period of time for the permittee to comply with that limit. In such cases, the Department shall establish a schedule in the permit for implementing the controls, measures or practices needed to assure compliance with such new or more restrictive limits, in accordance with Section 6.17. For example, the permit may outline a schedule for modifying, replacing or repairing sufficient noncontact cooling water condenser tubes or other piping and appurtenances, a schedule for locating or developing and tapping into an alternative water supply or a schedule for installing a treatment system or methodology that would yield a statistically significant lower corrosivity or erosiveness.

8.4.3.3.1 Conditions. The Department may establish a compliance schedule if the discharger demonstrates, based upon sound rationale and supported by substantial scientific and technical evidence and analysis, all of the following:

8.4.3.3.1.1 In the absence of pollutants corroded and eroded from the facility's water distribution piping and appurtenances, there would be no violation of the surface water quality criteria in the receiving water; and

8.4.3.3.1.2 The normal corrosion and erosion (as defined herein and after corrosion/erosion control has been employed) associated with the intake water used by the facility for noncontact cooling is sufficient to cause the violation; and

8.4.3.3.1.3 No other activity, condition or method of operation, or materials used or produced at the facility, which results in the addition of erosion and corrosion based pollutants into the facility's discharge, significantly contributes to the violations of surface water quality criteria in the receiving waters. Such activities, conditions or methods of operation, or materials used or produced at the facility include entrainment of erosion and corrosion based pollutants previously discharged or disposed by the facility.

8.4.4 Consideration for Pollutants in Intake Waters When Assessing Reasonable Potential

8.4.4.1 When evaluating whether a discharge causes or has the reasonable potential to cause or to contribute to an exceedance of either a narrative or numeric water quality criterion, within an applicable surface water quality standard, the Department may determine there is no reasonable potential for the discharge to cause or contribute to the exceedance of a criterion where the quality of a facility's intake water causes or would reasonably be expected to cause such exceedance in the receiving waters, provided the discharger demonstrates, based upon sound rationale and supported by substantial scientific and technical evidence and analysis, that the following § 8.4.4.1.1 through 8.4.4.1.5, and 8.4.4.1.6 if applicable exists:

8.4.4.1.1 In the absence of pollutants in the facility's intake water, there would be no violation of the surface water quality criteria in the receiving waters; and

8.4.4.1.2 No other activity, condition or method of operation, or material used or produced at the facility contributes to the discharge of intake pollutants; or

8.4.4.1.3 No other activity, condition or method of operation, or material used or produced at the facility introduces intake pollutants into the discharge in amounts that, by themselves, would reasonably be expected to cause or contribute to the violation of surface water quality criteria; and

8.4.4.1.4 Upon statistically rigorous analysis of intake water and outfall data representative of various operating conditions and influences over time, there is no discernible difference between the quality of theintake water and the quality of the discharge; and

8.4.4.1.5 Intake pollutants merely pass through the facility; intake pollutants are not altered chemically or physically as they travel through the facility or as intake water is employed for cooling or process-related purposes; and

8.4.4.1.6 No practicable alternative intake water of sufficient quality and quantity is available to the facility; and, if applicable,

8.4.4.1.7 Where a significant percentage of the discharged water is comprised of water purchased from a water utility, water pumped from wells, or water pumped from a stream basin different from that receiving the discharge, the facility must demonstrate that no adverse impact on designated uses may reasonably be expected to occur as a result of the discharge.

In doing so, the facility must demonstrate that existing criteria are more stringent than necessary and that alternative, less-stringent criteria will adequately protect the receiving waters' designated uses. The Department shall in turn, modify the otherwise applicable water quality criterion and adopt a site-specific criterion as outlined in § 5.2 of the State of Delaware Surface Water Quality Standards, as amended, August 11, 1999.

As an alternative, the discharger may seek, and be granted, a variance from the otherwise applicable surface water quality criterion, similar to that provided for pollutants corroded and eroded from water distribution piping and appurtenances, as outlined in § 8.4.3.2 herein and § 5.4 of the State of Delaware Surface Water Quality Standards, as amended, August 11, 1999. In such cases the discharger shall demonstrate that implementation of the controls needed to assure compliance with the applicable water quality criteria would result in substantial and widespread economic and social impact. The analysis of economic impacts must demonstrate that:

8.4.4.1.7.1 The discharger would face substantial financial impacts due to the costs of the necessary pollution controls or water treatment (substantial impacts of which would interfere with development), and

8.4.4.1.7.2 The affected community will bear significant adverse impacts if the entity is required to meet existing or proposed water quality standards (widespread impacts of important development).

A variance granted under this Subsection shall be effective for three years or the life of the NPDES permit, and at the expiration of either time period, the discharger must meet the criteria or make a new demonstration of unattainability and financial impact. Variances considered under this section shall be subject to all applicable public participation requirements and shall be subject to review and approval by the U.S. Environmental Protection Agency.

8.4.4.2 The determinations under § 8.4.4.1. shall be made on a pollutant-by-pollutant, outfall-by-outfall basis.

8.4.4.3 The Department shall not be obligated to establish water quality-based effluent limitations in cases where a determination is made under § 8.4.4.1. that a pollutant in the discharge does not cause, have the reasonable potential to cause, or contribute to an exceedance of an applicable water quality standard. However, the permit may include appropriate provisions for either or both the intake and discharge to ensure continued compliance with the conditions (ii), (iii) and (iv) in § 8.4.4.1. In addition, the permit shall contain a reopener clause that authorizes the modification or revocation and reissuance of the permit if the Department establishes a TMDL or if new information indicates changes in the conditions upon which the determination under Section 8.4.4.1 is made.

8.4.4.4 In cases where a facility meets the conditions in §§ 8.4.4.1.2, 8.4.4.1.3 and 8.4.4.1.4, the Department may opt to include "no net addition limitations", allowing the facility to discharge a mass and concentration of a pollutant identified in the facility's intake water. The permit shall specify how compliance with mass and concentration limitations shall be assessed.

7 Del. Admin. Code § 7201-8.0