11-3 Ammonia

Will Invenergy be conducting an impact zone analysis for the proposed 40,000 gallons of 19% aqueous ammonia storage at CREC?

RESPONSE 11-3:

 

The United States Environmental Protection Agency (“EPA”) requires facilities with large quantities of hazardous chemicals to prepare and implement a Risk Management Program to prevent the accidental release of those chemicals and mitigate the consequences of any releases that do occur.  The EPA only requires a Risk Management Plan for the storage of aqueous ammonia when the concentration is 20% or greater, because it does not consider aqueous ammonia stored at a concentration less than 20% to pose a public health risk upon release. 

 

Acute Exposure Level Guidelines (“AEGLs”) are used by emergency planners and responders as guidance in dealing with accidental releases of chemicals into the air.  AEGLs are expressed as concentrations of airborne chemicals at which health effects may occur and are designed to protect the elderly and children, as well as other individuals who may be susceptible. 

 

AEGL levels are dictated by the severity of the toxic effects caused by the exposure, as follows:

 

  • AEGL-1 (Level 1): Notable discomfort, irritation, or certain asymptomatic non-sensory effects. Any effects are not disabling and are transient and reversible upon cessation of exposure.

 

  • AEGL-2 (Level 2): Irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.

 

  • AEGL-3 (Level 3): Life-threatening health effects or death. 

 

Airborne concentrations below the AEGL-1 are exposure levels which could produce mild, transient, odor, taste and sensory irritation. These effects are non-disabling, allowing for safe evacuation from any impacted areas.

 

For ammonia, the 1-hour AEGL concentrations have been defined as follows:

 

  • AEGL-1: 30 parts per million (“ppm”)
  • AEGL-2: 160 ppm
  • AEGL-3: 1,100 ppm

 

The 19% aqueous ammonia will be stored in a single-walled steel above-ground storage tank.  The ammonia storage tank and its associated transfer pumps, valves and piping will be contained within a concrete containment area designed to contain up to 110% of the storage tank capacity.  Ammonia sensors within the containment area will alert plant operators of any system leaks.  To minimize the evaporation rate of ammonia into the ambient air, the containment area will be filled with passive evaporative controls to reduce the exposed surface area of any aqueous ammonia within the containment area by 90 percent.

 

Although the CREC is not subject the Risk Management Program, a worst-case accidental release scenario has been evaluated to assess the potential consequences in the extremely unlikely event of a release of the full 40,000 gallons of 19% aqueous ammonia into the containment area.  This assessment was performed using the Area Locations of Hazardous Atmospheres (“ALOHA”) Model developed by the EPA and the National Oceanic and Atmospheric Administration and included as a prescribed technique under the Risk Management Program.  It was completed in accordance with the procedures contained in the EPA’s “Risk Management Program Guidance for Offsite Consequence Analysis.”

 

The results of the worst-case accidental release scenario assessment completed for the CREC aqueous ammonia storage tank are shown in both tabular and graphical form in Exhibit 1.  Based on the ALOHA modeling results, the furthest downwind distances from the ammonia storage tank at which the in-air ammonia concentrations would exceed each of the ammonia AEGL levels during a worst-case accidental release are as follows:

 

  • AEGL-1: 121 yards
  • AEGL-2: 53 yards
  • AEGL-3: 20 yards

 

As shown on the figure in Exhibit 1, all of the areas in which the in-air ammonia concentration would exceed the AEGL-1 level are within the facility fenceline.  Emergency procedures will be established to evacuate facility personnel from these areas in the event of a release and to require emergency personnel to utilize the proper personal protective equipment before entering these areas until the released ammonia has been properly recovered.

 

The in-air ammonia concentrations in all other areas of the facility and in all areas beyond the facility property line during a worst-case accidental release would be below the AEGL-1 level, thus resulting in no adverse health effects upon exposure.  Although there would be no public health risk, Invenergy will work with local emergency responders to establish emergency procedures in the unlikely event there is an accidental release of ammonia from the facility.              

 

RESPONDENT:

 

Michael Feinblatt, ESS Group

 

DATE:

June 13, 2016