340-041-0033 Toxic Substances (1) Toxic Substances Narrative. Toxic substances may not be introduced above natural background levels in waters of the state in amounts, concentrations, or combinations that may be harmful, may chemically change to harmful forms in the environment, or may accumulate in sediments or bioaccumulate in aquatic life or wildlife to levels that adversely affect public health, safety, or welfare or aquatic life, wildlife or other designated beneficial uses. (2) Aquatic Life Numeric Criteria. Levels of toxic substances in waters of the state may not exceed the applicable aquatic life criteria as defined in Table 30 under OAR 340-041-8033. (3) Human Health Numeric Criteria. The criteria for waters of the state listed in Table 40 under OAR 340-041-8033 are established to protect Oregonians from potential adverse health effects associated with long-term exposure to toxic substances associated with consumption of fish, shellfish and water. (4) To establish permit or other regulatory limits for toxic substances without criteria in Table 30 under OAR 340-041-8033 or Table 40 under 340-041-8033, DEQ may use public health advisories and published scientific literature. DEQ may also require or conduct bio-assessment studies to monitor the toxicity to aquatic life of complex effluents, other suspected discharges or chemical substances without numeric criteria. (5) Establishing Site-Specific Background Pollutant Criteria: This provision is a performance- based water quality standard that results in site-specific human health water quality criteria under the conditions and procedures specified in this rule section. It addresses existing permitted discharges of a pollutant removed from the same body of water. For waterbodies where a discharge does not increase the pollutant’s mass and does not increase the pollutant concentration by more than 3 percent, and where the water body meets a pollutant concentration associated with a risk level of 1 x 10-4, DEQ concludes that the pollutant concentration continues to protect human health. (a) Definitions: As used in this section: (A) “Background pollutant concentration” means the ambient water body concentration immediately upstream of the discharge, regardless of whether those pollutants are natural or result from upstream human activity. (B) An “intake pollutant” is the amount of a pollutant present in waters of the state (including groundwater) as provided in subsection (C), below, at the time it is withdrawn from such waters by the discharger or other facility supplying the discharger with intake water. (C) “Same body of water”: An intake pollutant is considered to be from the “same body of water” as the discharge if DEQ finds that the intake pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had the permittee not removed it. To make this finding, DEQ requires information showing that: (i) 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; and, (ii) There is a direct hydrological connection between the intake and discharge points. (I) DEQ may also consider other site-specific factors relevant to the transport and fate of the pollutant to make the finding in a particular case that a pollutant would or would not have reached the vicinity of the outfall point in the receiving water within a reasonable period had the permittee not removed it. (II) An intake pollutant from groundwater may be considered to be from the “same body of water” if DEQ determines that the pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had the permittee not removed it. A pollutant is not from the same body of water if the groundwater contains the pollutant partially or entirely due to past or present human activity, such as industrial, commercial, or municipal operations, disposal actions, or treatment processes. (iii) Water quality characteristics (e.g., temperature, pH, hardness) are similar in the intake and receiving waters. (b) Applicability (A) DEQ may establish site-specific criteria under this rule section only for carcinogenic pollutants. (B) Site-specific criteria established under this rule section apply in the vicinity of the discharge for purposes of establishing permit limits for the specified permittee. (C) The underlying waterbody criteria continue to apply for all other Clean Water Act programs. (D) The site-specific background pollutant criterion will be effective when DEQ issues the permit for the specified permittee. (E) DEQ will reevaluate any site-specific criteria developed under this procedure upon permit renewal. (c) DEQ may establish a site-specific background pollutant criterion when all of the following conditions are met: (A) The discharger has a currently effective NPDES permit; (B) The mass of the pollutant discharged to the receiving waterbody does not exceed the mass of the intake pollutant from the same body of water, as defined in section (5)(a)(C) above, and therefore does not increase the total mass load of the pollutant in the receiving water body; (C) DEQ has not assigned the discharger a TMDL wasteload allocation for the pollutant in question; (D) The permittee uses any feasible pollutant reduction measures available and known to minimize the pollutant concentration in their discharge; (E) The pollutant discharge has not been chemically or physically altered in a manner that causes adverse water quality impacts that would not occur if the intake pollutants were left in-stream; and, (F) The timing and location of the pollutant discharge would not cause adverse water quality impacts that would not occur if the intake pollutant were left in-stream. (d) The site-specific background pollutant criterion must be the most conservative of the following four values. Section (5)(e) of this rule describes the procedures for deriving these values. (A) The projected in-stream pollutant concentration resulting from the current discharge concentration and any feasible pollutant reduction measures under (c)(D) above, after mixing with the receiving stream. (B) The projected in-stream pollutant concentration resulting from the portion of the current discharge concentration associated with the intake pollutant mass after mixing with the receiving stream. This analysis ensures that there will be no increase in the mass of the intake pollutant in the receiving water body as required by condition (c)(B) above. (C) The projected in-stream pollutant concentration associated with a 3 percent increase above the background pollutant concentration as calculated: (i) For the main stem Willamette and Columbia Rivers, using 25 percent of the harmonic mean flow of the waterbody. (ii) For all other waters, using 100 percent of the harmonic mean flow or similar critical flow value of the waterbody. (D) A criterion concentration value representing a human health risk level of 1 x 10-4. DEQ calculates this value using EPA’s human health criteria derivation equation for carcinogens (EPA 2000), a risk level of 1 x 10-4, and the same values for the remaining calculation variables that were used to derive the underlying human health criterion. (e) Procedure to derive a site-specific human health water quality criterion to address a background pollutant: (A) DEQ will develop a flow-weighted characterization of the relevant flows and pollutant concentrations of the receiving waterbody, effluent and all facility intake pollutant sources to determine the fate and transport of the pollutant mass. (i) The pollutant mass in the effluent discharged to a receiving waterbody may not exceed the mass of the intake pollutant from the same body of water. (ii) Where a facility discharges intake pollutants from multiple sources that originate from the receiving waterbody and from other waterbodies, DEQ will calculate the flow-weighted amount of each source of the pollutant in the characterization. (iii) Where a municipal water supply system provides intake water for a facility and the supplier provides treatment of the raw water that removes an intake water pollutant, the concentration and mass of the intake water pollutant must be determined at the point where the water enters the water supplier’s distribution system. (B) Using the flow weighted characterization developed in section (5)(e)(A), DEQ will calculate the in-stream pollutant concentration following mixing of the discharge into the receiving water. DEQ will use the resultant concentration to determine the conditions in section (5)(d)(A) and (B). (C) Using the flow-weighted characterization, DEQ will calculate the in-stream pollutant concentration based on an increase of 3 percent above background pollutant concentration. DEQ will use the resultant concentration to determine the condition in Section (5)(d)(C). (i) For the main stem Willamette and Columbia Rivers, DEQ will use 25 percent of the harmonic mean flow of the waterbody. (ii) For all other waters, DEQ will use 100 percent of the harmonic mean flow or similar critical flow value of the waterbody. (D) DEQ will select the most conservative of the following values as the site-specific water quality criterion. (i) The projected in-stream pollutant concentration described in section (5)(e)(B); (ii) The in-stream pollutant concentration based on an increase of 3 percent above background described in section (5)(e)(C); or (iii) A water quality criterion based on a risk level of 1 x 10-4. (f) Calculation of water quality based effluent limits based on a site-specific background pollutant criterion: (A) For discharges to receiving waters with a site-specific background pollutant criterion, DEQ will use the site-specific criterion in the calculation of a numeric water quality based effluent limit. (B) DEQ will compare the calculated water quality based effluent limits to any applicable aquatic toxicity or technology based effluent limits and select the most conservative for inclusion in the permit conditions. (g) In addition to the water quality based effluent limits described in section (5)(f), DEQ will calculate a mass-based limit where necessary to ensure that the condition described in section (5)(c)(B) is met. Where mass-based limits are included, the permit will specify how DEQ will assess compliance with mass-based effluent limitations. (h) The permit shall include a provision requiring DEQ to consider the re-opening of the permit and re-evaluation of the site-specific background pollutant criterion if new information shows the discharger no longer meets the conditions described in subsections (5)(c) and (e). (i) Public Notification Requirements. (A) If DEQ proposes to grant a site-specific background pollutant criterion, it must provide public notice of the proposal and hold a public hearing. The public notice may be included in the public notification of a draft NPDES permit or other draft regulatory decision that would rely on the criterion and will also be published on DEQ’s water quality standards website; (B) DEQ will publish a list of all site-specific background pollutant criteria approved according to this rule. DEQ will add the criterion to this list within 30 days of its effective date. The list will identify the: (i) Permittee; (ii) Site-specific background pollutant criterion and the associated risk level; (iii) Waterbody to which the criterion applies; (iv) Allowable pollutant effluent limit; and, (v) How to obtain additional information about the criterion. (6) Arsenic Reduction Policy: The inorganic arsenic criterion for the protection of human health from the combined consumption of organisms and drinking water is 2.1 micrograms per liter. While this criterion is protective of human health and more stringent than the federal maximum contaminant level (MCL) for arsenic in drinking water, which is 10 micrograms per liter, it is based on a higher risk level than EQC used to establish other human health criteria. This higher risk level recognizes that much of the risk is due to naturally high levels of inorganic arsenic in Oregon’s waterbodies. In order to maintain the lowest human health risk from inorganic arsenic in drinking water, EQC determined that it is appropriate to adopt the following policy to limit the human contribution to that risk. (a) It is EQC policy to reduce the addition of inorganic arsenic from new or existing anthropogenic sources to waters of the state within a surface water drinking water protection area to the maximum amount feasible. The requirements of this rule section (OAR 340-041-0033(6)) apply to sources that discharge to surface waters of the state with an ambient inorganic arsenic concentration equal to or lower than the applicable numeric inorganic arsenic criteria for the protection of human health. (b) Definitions. As used in this section: (A) “Add inorganic arsenic” means to discharge a net mass of inorganic arsenic from a point source (the mass of inorganic arsenic discharged minus the mass of inorganic arsenic taken into the facility from a surface water source). (B) A “surface water drinking water protection area,” means an area delineated as such by DEQ under the source water assessment program of the federal Safe Drinking Water Act, 42 U.S.C. § 300j 13. DEQ delineates these areas to protect public or community drinking water supplies that use surface water sources. These delineations are on DEQ’s drinking water program Web page. (C) “Potential to significantly increase inorganic arsenic concentrations in the public drinking water supply source water” means: (i) A discharge will increase the concentration of inorganic arsenic in the receiving water by 10 percent or more after mixing with the harmonic mean flow of the receiving water; or (ii) As an alternative, if sufficient data are available, the discharge will increase the concentration of inorganic arsenic in the surface water intake water of a public water system by 0.021 micrograms per liter or more based on a mass balance calculation. (c) Following the effective date of this rule, applications for an individual NPDES permit or permit renewal received from industrial dischargers located in a surface water drinking water protection area and identified by DEQ as likely to add inorganic arsenic to the receiving water must include sufficient data to enable DEQ to determine whether: (A) The discharge adds inorganic arsenic; and, (B) The discharge has the potential to significantly increase inorganic arsenic concentrations in the public drinking water supply source water. (d) Where DEQ determines that both conditions in subsection (c) of this section (6) are true, the industrial discharger must develop an inorganic arsenic reduction plan and propose all feasible measures to reduce its inorganic arsenic loading to the receiving water. The proposed plan, including proposed measures, monitoring and reporting requirements, and a schedule for those actions, will be described in the fact sheet and incorporated into the source’s NPDES permit after public comment and DEQ review and approval. In developing the plan, the source must: (A) Identify how much it can minimize its inorganic arsenic discharge through pollution prevention measures, process changes, wastewater treatment, alternative water supply for groundwater users, or other possible pollution prevention and control measures; (B) Evaluate the costs, feasibility and environmental impacts of the potential inorganic arsenic reduction and control measures; (C) Estimate the predicted reduction in inorganic arsenic and the reduced human health risk expected to result from the control measures; (D) Propose specific inorganic arsenic reduction or control measures, if feasible, and an implementation schedule; and, (E) Propose monitoring and reporting requirements to document progress in plan implementation and the inorganic arsenic load reductions. (e) In order to implement this section, DEQ will develop the following information and guidance within 120 days of the effective date of this rule and periodically update it as warranted by new information: (A) A list of industrial sources or source categories, including industrial stormwater and sources covered by general permits likely to add inorganic arsenic to surface waters of the state. For industrial sources or source categories permitted under a general permit that have been identified by DEQ as likely sources of inorganic arsenic, DEQ will evaluate options for reducing inorganic arsenic during permit renewal or evaluation of Stormwater Pollution Control Plans. (B) Quantitation limits for monitoring inorganic arsenic concentrations. (C) Information and guidance to assist sources in estimating, according to subsection (d)(C) of this section, the reduced human health risk expected to result from inorganic arsenic control measures based on the most current EPA risk assessment. (f) It is the policy of EQC that landowners engaged in agricultural or development practices on land where pesticides, fertilizers, or soil amendments containing arsenic are currently being or have previously been applied, implement conservation practices to minimize the erosion and runoff of inorganic arsenic to waters of the state or to a location where such material could readily migrate into waters of the state. [NOTE: Tables 30 and 40 are found under OAR 340-041-8033.] Statutory/Other Authority: ORS 468.020, 468B.030, 468B.035 & 468B.048 Statutes/Other Implemented: ORS 468B.030, 468B.035 & 468B.048 History: DEQ 16-2024, amend filed 10/03/2024, effective 10/03/2024 DEQ 11-2016, f. & cert. ef. 11-2-16 DEQ 1-2015, f. & cert. ef. 1-7-15 DEQ 17-2013, f. 12-23-13, cert. ef. 4-18-14 DEQ 10-2011, f. & cert. ef. 7-13-11 DEQ 8-2011, f. & cert. ef. 6-30-11 DEQ 17-2010, f. & cert. ef. 12-21-10 DEQ 3-2004, f. & cert. ef. 5-28-04 DEQ 17-2003, f. & cert. ef. 12-9-03