Degree of Toxicity above moderate The capacity-related SSOs pose an above moderate risk or threat to potential receptors because, though diluted by I&I, the SSOs are not treated and would contain bacteria at levels exceeding human health standards and potentially toxic to aquatic organisms. Degree of Toxicity: above moderate The blockage-related SSOs pose an above moderate risk or threat to potential receptors because these SSOs consist of untreated sewage. Susceptibility to Cleanup or Abatement 1 0 Susceptibility to Cleanup: no For capacity-related SSOs, less than 50% of these SSOs was amenable to cleanup or containment because the collection system, storm drains, and creeks were also flowing full at the time. Susceptibility to Cleanup: yes For blockage-related SSOs, greater than 50% of each was susceptible to cleanup as the Discharger response time was adequate (average of about 1 hour). However, we note that the actual average SSO recovery was about 27 percent. Final Potential for Harm Score 5 5 This is the value for capacity-related SSOs. This is the value for blockage-related SSOs
Degree of Toxicity moderate The discharge of insufficiently treated contaminated groundwater posed a moderate risk or threat to potential receptors based on its chemical and physical characteristics. Prior to discharge, the groundwater was pumped to a settling tank, then through sand media filtration, then through bag and cartridge filtration, and finally through granulated activated carbon. Nevertheless, there was some level of toxicity, posing a moderate level of threat to potential receptors. According to the Discharger’s Self-Monitoring Report for the period of January 1, 2021, through June 30, 2021, the discharge exceeded the Permit’s effluent limits for selenium and nickel. These effluent limitations were derived from water quality standards to protect water quality. The selenium concentration was 460 micrograms per liter (µg/l), which exceeded the average monthly effluent limit of 4.1 µg/l and the daily maximum effluent limit of 8.2 µg/l. The nickel concentration was 61 µg/l, which exceeded the average monthly effluent limit of 22 µg/l and the daily maximum effluent limit of 44 µg/l. Other parameters, including cadmium, copper, zinc, and cyanide, may also have been present above effluent limits, but the results were J-flagged (i.e., reported as estimates). Actual Harm or Potential Harm to Beneficial Uses 1 Potential for Harm: minor The Basin Plan assigns Ravenswood Slough the following beneficial uses: estuarine habitat (EST); preservation of rare and endangered species (RARE), wildlife habitat (WILD), water contact recreation (REC-1), and noncontact water recreation (REC-2). The discharge likely posed minor harm or potential harm to the aquatic life beneficial uses because, based on the discharge characteristics (see “Degree of Toxicity of Discharge” above) and applicable beneficial uses, there may have been a short-term impact to beneficial uses but likely no appreciable harm.
Degree of Toxicity. Moderate A score of 2, moderate, is selected because levels of nitrogen discharged to groundwater pose a moderate risk to human health. Nitrogen discharged from the facility (over 200 mg/L) may elevate nitrate concentrations in groundwater to levels that exceed the U.S. EPA Maximum Contaminant Level (MCL) for drinking water (45 mg/L). Nitrate exceeding the MCL can cause methemoglobinemia.2
Degree of Toxicity above moderate For the April 2, 2017, SSO, an “above moderate” degree of toxicity is selected because the sewage discharged was not treated, was potentially toxic to aquatic organisms, and contained bacteria at levels exceeding human health standards. Therefore, the discharge posed an above moderate risk to potential receptors. Susceptibility to Cleanup or Abatement 0 Susceptibility to Cleanup: yes The April 2, 2017, SSO occurred during dry weather; therefore, greater than 50 percent of the SSO was susceptible to cleanup. However, the Settling Respondent did not recover any of this SSO. Final Potential for Harm Score 6 A value of 6 (3+3+0) applies to the April 2, 2017, SSO.
Degree of Toxicity. Above Moderate Milk and propylene glycol pose an above moderate risk to aquatic species. While the apparent toxicity is low, the BOD of milk and propylene glycol is significant and has the propensity to deplete oxygen in receiving waters. The BOD of milk is on the order of 100,000 mg/L, and the BOD of propylene glycol is higher. The discharge effluent limit for BOD is typically around 30 mg/L. The concentration of BOD in very high quality to moderately polluted waters is between 1 and 8 mg/L. Susceptibility to Cleanup or Abatement 0 Susceptibility to Cleanup: yes 50 percent or more of the alleged discharge was susceptible to cleanup or abatement. SSI flushed Facility storm drains and removed up to 5,800 gallons of water, milk and propylene glycol from Xxxxxxx Canyon Creek to the satisfaction of the California Department of Fish and Wildlife representative onsite.
Degree of Toxicity. Acute toxicity testing is a direct measurement of the toxicity of the discharge on juvenile fish. In this case, the Discharger continuously subjects rainbow trout, which is an indicator for thousands of other species that reside in San Francisco Bay, to its effluent for 96 hours. Therefore, the Regional Water Board alleges that the degree of toxicity of the discharge from these violations is high.
Degree of Toxicity moderate The discharge posed a moderate risk or threat to potential receptors based on its chemical and physical characteristics. The discharge was partially-treated and undisinfected municipal wastewater. The wastewater had passed through mechanical barrel grinders and been treated in preaeration tanks, primary sedimentation basins, and oxidation ponds, but it had not yet been disinfected. According to the Discharger’s Five-Day Written Report, the discharge contained ammonia, total suspended solids (TSS), and biochemical oxygen demand (BOD) at or above the Permit’s effluent limits: the ammonia, TSS, and BOD discharge concentrations were 6.4 milligrams per liter (mg/L), 60 mg/L, and 20 mg/L, compared to the Permit’s maximum daily effluent limits of 5 mg/L, 30 mg/L, and 20 mg/L. The pH of the discharge was 8.9 and exceeded the Permit’s instantaneous effluent limit of 8.5. The discharge contained enterococcus at more than 2,420 most probable number per 100 milliliters (MPN/100 mL). The bacteria water quality objective for all waters where the salinity is greater than one part per thousand more than five percent of the time during the calendar year is a six-week geometric mean effluent limit of 30 colony forming units per 100 milliliters (CFU/100 mL), calculated weekly, and a statistical threshold value of 110 CFU/100 mL.1 For the purposes of this comparison, 1 MPU/100 mL is equivalent to 1 CFU/100 mL. The discharge was a single event, so the six-week geometric mean is not applicable. The discharge contained at least 2,420 MPU/100mL, 22 times the statistical threshold value for enterococcus, exceeding the water quality objective for bacteria in saline water. Bacteria, such as enterococcus, can cause a variety of diseases or illnesses through physical contact or ingestion, and the pH in the discharge was at a level indicative of water not suitable for a healthy aquatic ecosystem. Actual Harm or Potential Harm to Beneficial Uses 2 Harm or Potential for Harm: below moderate The discharge posed below-moderate harm or potential harm to beneficial uses because, although impacts could be reasonably expected based on the discharge characteristics (see “Degree of Toxicity of Discharge” above) and applicable beneficial uses, the harm was likely short-term and not appreciable. The Basin Plan states that the beneficial uses of a specified water body generally apply to its tributaries. The Basin Plan assigns Xxxxxxxxx Xxxxxx – and by the tributary rule, Fish and Wildlife ...
Degree of Toxicity. The evaluation of this factor considers the physical, chemical, biological, and/or thermal characteristics of the discharge and the risk of damage the discharge could cause to the receptors or beneficial uses. Potential receptors are human, environmental, and ecosystem exposure pathways. In this case, the sanitary sewer overflow was raw sewage, and is known to contain highly elevated concentrations of coliform organisms, biochemical oxygen demand, and ammonia. Discharges of sewage to surface water must typically be treated to a high standard to prevent adverse impacts 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. In this case, the discharge consisted of raw sewage, which contains pathogens, nitrogen, ammonia, and biological oxygen demand. Fish are highly sensitive to even small concentrations of ammonia. Elevated levels of these constituents can lead to low dissolved oxygen in the receiving water, impacts to aquatic life, and impacts to human health. Because the discharged material possesses “an above-moderate risk or a direct threat to potential receptors,” a score of 3 was assigned for this factor.
Degree of Toxicity moderate The 1.6-MG discharge posed a moderate risk because the discharge fits the Enforcement Policy definition that “… the characteristics of the discharged material have some level of toxicity or pose a moderate level of concern regarding receptor protection ….” The wastewater is chlorinated to as high as 3.4 mg/L. The U.S. EPA Water Quality Criterion for chlorine to prevent acute (lethal) effects to aquatic life is 0.019 mg/L.
Degree of Toxicity moderate The 2.2-MG discharge posed a moderate risk because the bacteria and viruses in undisinfected wastewater fit the Enforcement Policy definition of “… pose a moderate level of concern regarding receptor protection.”
