Chemical, Biological or Thermal Characteristics of the Discharge. Significant A score between 0 and 4 is assigned based on a determination of the risk and threat of the discharged material. The violation poses either a negligible, minor, moderate, above-moderate or significant risk or threat to potential receptors. A factor of 4 was assigned to this discharge because of Significant risk or threat to potential receptors. The Enforcement Policy defines a factor of 4 as the “[d]ischarged material poses a significant risk or threat to potential receptors (i.e., the chemical and/or physical characteristics of the discharged material far exceed risk factors or receptor harm is considered imminent).” Crude oil spills pose a significant risk or threat to potential ecosystem health because crude oil consists of harmful pollutants such as total petroleum hydrocarbons and often contain substances such as benzene, chromium, iron, mercury, nickel, nitrogen, oxygen, sulfur, toluene, and xylene which are toxic to fish and wildlife through ingestion and inhalation. Fish and wildlife may experience various toxicological effects that include immune and reproduction system issues as well as disrupted organ function. Furthermore, benzene, toluene, and xylene found in crude oil are carcinogenic compounds that can dissolve or deform cell membranes. Cell membranes contain enzymes and transport proteins to cells. Once damaged active membranes may not have the ability to transport proteins leading to cell death. Benzene in particular has the ability to damage cells, cause cellular mutations and cancer by uncontrolled cell growth leading to wildlife and human deaths.
Chemical, Biological or Thermal Characteristics of the Discharge. A score between 0 and 4 is assigned based on the characteristics of the discharge itself. In this case, the partially treated, super-chlorinated discharge was disinfected but had not been dechlorinated. The wastewater contained chlorine concentrations which exceeded the 1-hour and 4-day residual chlorine effluent limitations in the WDRs. The Discharger is permitted by the WDRs to discharge tertiary treated wastewater to Old Alamo Creek, but is required to ensure that the discharge not be toxic to aquatic life. Toxicity is the degree to which a substance can damage a living or non-living organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ. Chlorine is a known toxicant to freshwater aquatic life; short-term acute exposure may result in biological harm or death while chronic exposure over an extended period of time may lead to irreversible side effects. The low effluent limits in the WDRs reflect the high toxicity of chlorine to aquatic organisms. The discharge was 143 times higher than the 1-hour average effluent limit and 2.5 times higher than the 4-day average limit. Because the discharged material “exceeded known risk factors and/or there is substantial concern regarding receptor protection,” a score of 3 was assigned for this factor.
