Pacific Southwest, Region 9
Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations
Evoqua Water Technologies
(formerly Siemens Carbon Regeneration Facility)
Summary of Risk Assessment for Evoqua Water Technologies
On July 30, 2007, Evoqua submitted its Human Health and Ecological Risk Assessment Report to EPA. The risk assessment uses the results from the Final March 2006 air emissions test, conducted at the facility in accordance with EPA regulations for this type of facility.
- EPA's fact sheet regarding the air emissions test and risk assessment (PDF) (2pp, 688K)
- HHERA "Risk Assessment" Report (PDF)
- Performance Demonstration Test Plan (PDF) (394 pp, 1.2M)
- Performance Demonstration Test Report (PDF) (120 pp, 1.8M)
The risk assessment demonstrates that even using conservative assumptions:
- The potential risks associated with air emissions from both the Facility’s carbon reactivation furnace and from spent carbon unloading are below regulatory and other target risk levels, for both human health and ecological receptors;
- The incremental contribution of effluent from the Facility’s wastewater treatment plant and the Main Drain does not pose unacceptable risks to either aquatic life or human health; and,
- Both concentrations of fugitive emissions from carbon unloading at the facility and measured worker breathing zone concentrations are below occupational exposure limits.
In conclusion, this risk assessment demonstrates that even with conservative assumptions, the potential risks associated with Facility operations are below regulatory and target levels.
Risk Assessment Technical Information
Potential risks from stack air emissions were evaluated for over 170 compounds. These were selected for detailed assessment based on a comprehensive performance demonstration test (PDT). This test was approved in advance by USEPA and conducted at the facility by an independent testing firm. The PDT involved several days of stack gas sampling and sophisticated chemical analysis.
The list of chemicals selected for evaluation included both compounds that were detected in stack emissions, as well as over 80 other compounds not detected, but included in the calculations just to be safe. Stack emission rates for all the selected compounds were calculated based on either PDT results, proposed permit limits, or for a few chemicals, long-term average chemical feed rates. A conservative value was also used for the furnace’s destruction and removal efficiency in the calculations.
Potential risks from fugitive air emissions (rather than stack emissions) were evaluated for 21 compounds. These were selected for evaluation based on their spent carbon concentrations, number and amount of deliveries to the facility, chemical toxicity, and volatility. Air dispersion and deposition modeling was conducted using a model developed and approved by USEPA. This model calculated chemical concentrations in the air and ground deposition rates within a 154 square mile study area surrounding the facility. The mathematical equations used to calculate the fate and transport of each chemical in the environment, environmental concentrations for each chemical, human exposures and risks, were based on current EPA guidance and solved using the Industrial Risk Assessment Program software.
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