General. The Department shall adopt toxic substance criteria for any substance that the Department determines could reasonably be expected to interfere with designated uses. If a discharge of a toxic substance not identified in COMAR 26.08.02 occurs, the Department may: Adopt a water quality criterion for the toxic substance in accordance with the emergency regulation procedure under State Government Article, Annotated Code of Maryland; Ban the discharge of the toxic substance under the general authorities in Environment Article, Title 9, Annotated Code of Maryland; Modify any existing discharge permit to include a limitation for the toxic substance, or deny any new discharge permit until the Department determines the effect of the discharge; Require biomonitoring and chemical testing by any discharger to demonstrate the impact of a toxic substance in the surface water; or Take any other action permitted by applicable law. Compliance with permit limits based on toxic substance criteria shall be determined through application of a standard method accepted by the Department for the measurement of the toxic substance. Effluent Limitation Modification for Toxic Substances. The Department may, upon written application from the applicant for a discharge permit, grant a temporary modification from one or more effluent limitations based on water quality criteria for toxic substances. A temporary modification may be granted for a period up to 3 years. In order to receive any temporary modification of a water quality based effluent limit, an applicant shall identify and employ all reasonable alternatives to reduce or eliminate toxicity in the discharge, including process changes, materials substitution, improved operation and maintenance, recycling, and pollution prevention activities. At the time of application for a temporary modification, the applicant shall provide to the Department all the necessary supporting data and information. If the Department needs additional information, the applicant shall bear the burden of generating that information. An application for a temporary modification shall identify the specific effluent limitation in the NPDES permit for which a temporary modification is sought, and shall demonstrate that at least one of the following factors is met: Naturally occurring pollutant concentrations prevent the attainment of the use; Natural, ephemeral, intermittent, or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State water conservation requirements to enable uses to be met; Human-caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied, or would cause more environmental damage to correct than to leave in place; Dams, diversions, or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate these modifications in a way that would result in the attainment of the use; Physical conditions related to the natural features of the water body, such as the lack of proper substrate, cover, flow, depth, pools, riffles, and similar conditions unrelated to water quality, preclude attainment of aquatic life protection uses; or Controls more stringent than those required by §§301(b) and 306 of the Federal Act would result in substantial and widespread economic and social impact. A temporary modification may be renewed for one or more periods up to 3 years each, upon written application and demonstration that the applicant meets the requirements for a temporary modification at the time of renewal. Opportunity for public participation shall be provided in accordance with the NPDES permitting process as described in COMAR 26.08.04. Criteria for Toxic Substances. The criteria for toxic substances in ambient water are found in COMAR 26.08.02.03—.03-3. Applicability to Dischargers. Dischargers Required to Conduct Monitoring for Toxic Substances. The Department shall require any permittee who has a discharge that falls into one of the following categories to perform biological or chemical monitoring for toxic substances: A POTW with a pretreatment program established in accordance with COMAR 26.08.08; An industrial discharger or POTW treatment plant with a wastewater flow greater than or equal to 1,000,000 gallons per day; A discharger whose discharge has demonstrated actual or potential toxicity; or A discharger whose discharge the Department has reason to believe may cause toxicity as determined by an evaluation of manufacturing processes, indirect discharges, treatment processes, effluent or receiving water data, or other relevant information. NPDES Permit Monitoring Requirements. A discharger identified in §D(1) of this regulation shall have requirements for toxic substance monitoring included in its permit at the time of permit issuance or reissuance. Modifications to these requirements may be allowed on a case-by-case basis if the: Specific conditions of the discharge suggest that a full scale toxics monitoring program is not necessary; or Characteristics of the receiving water indicate that a full scale toxics monitoring program is not needed. Data submitted under any previous toxic substance monitoring program may be used to satisfy these requirements if the data is indicative of the current process and treatment conditions. Any toxic substance monitoring, including test protocols, shall be approved by the Department before initiation of the testing. All data generated shall be within the quality assurance and quality control specifications of the test protocol. Measurements below the minimum level may be reported as BML (below minimum level). If the Department determines through the monitoring described in §D(1) of this regulation, that a discharge causes or has the potential to cause the discharge of toxic substances or an impact on surface waters, the Department may modify the discharge permit to require the discharger to collect data to verify or rule out the existence of an impact from a toxic substance. Technology-Based Whole Effluent Toxicity Testing Requirements. Purpose. Acute and chronic biotoxicity testing of effluents is used by the Department to assess the potential for acute and chronic toxicity in wastewater discharges. Permittee Responsibility. A finding of no toxicity in the effluent does not relieve the permittee from the obligation to provide best available treatment technology or to comply with water quality standards for conventional and toxic substances. Testing Required. The Department shall require biotoxicity testing in all new or renewed discharge permits for permittees identified in §D of this regulation. Acute Whole Effluent Toxicity. For the purpose of this subsection, an effluent is acutely toxic when the LC50 value resulting from the first 48 hours of a valid acute or chronic toxicity test is less than or equal to 100 percent effluent. LC50 means the effluent concentration at which 50 percent of the organisms die or are immobilized during the test. Each test shall be conducted using at least two species, one vertebrate and one invertebrate, as specified by the Department. Each test shall be conducted in accordance with the procedures specified by the Department. Unless otherwise specified in an existing permit, if the results for the first 48 hours of any two consecutive valid acute or chronic toxicity tests conducted within any 12-month period show acute toxicity under §E(4)(a) of this regulation, the permittee shall repeat the test within 30 days to confirm the finding of acute toxicity. One toxicity test shall be differentiated from another by the date on which the effluent was sampled, not by the number of species tested. If acute toxicity is confirmed, the permittee shall: Eliminate the source of toxicity through operational changes; or Perform a toxicity reduction evaluation as specified within a defined compliance schedule. If the permittee repeats toxicity testing under §E(4)(c) of this regulation and the results for the first 48 hours of the repeat test do not show acute toxicity, the Department will require the permittee to repeat toxicity testing as specified in the permit. De Minimus Discharges. For categories, other than those identified in §D(1) of this regulation, of similar discharges that individually or cumulatively will have a de minimus impact on water quality, the Department may permit testing of representative discharges instead of requiring each permittee to test its effluent for whole effluent toxicity. In these circumstances, the Department shall impose conditions on the permittees relieved of the burden of whole effluent toxicity testing, to ensure that their effluents remain similar to those of the tested permittees.