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3. Determining the Need for WQBELs <br /> Assessing whether a pollutant has Reasonable Potential is the fundamental step in <br /> detei7nining whether or not a WQBEL is required. <br /> a. Reasonable Potential Methodology <br /> For priority pollutants and most other toxic pollutants, the RPA identifies the observed <br /> maximum effluent concentration(MEC) for each pollutant based on effluent <br /> concentration data. There are three triggers in determining Reasonable Potential <br /> according to SIP Section 1.3. <br /> (1) The first trigger(Trigger 1) is activated if the MEC is greater than or equal to the <br /> lowest applicable WQO (MEC >_ WQO), which has been adjusted, if appropriate, for <br /> pH,hardness, and translator data. If the MEC is greater than or equal to the adjusted <br /> WQO,then that pollutant has Reasonable Potential, and a WQBEL is required. <br /> (2) The second trigger(Trigger 2) is activated if the observed maximum ambient <br /> background concentration(B) is greater than the adjusted WQO (B >WQO), and the <br /> pollutant is detected in any of the effluent samples (MEC>ND). <br /> (3) The third trigger(Trigger 3) is activated if a review of other information determines <br /> that a WQBEL is required to protect beneficial uses, even though both MEC and B <br /> are less than the WQO/WQC. <br /> b. Effluent Data <br /> Each Discharger currently covered under the Fuel General Permit was required to <br /> conduct effluent monitoring pursuant to the Self-Monitoring Program for Order No. R2- <br /> 2006-0075. The Regional Water Board analyzed the Dischargers' priority pollutant data <br /> and the nature of the discharges to determine if discharges have Reasonable Potential. <br /> Effluent data used to conduct this RPA consisted of data submitted as part of each Fuel <br /> General Permit facility's NOI which was combined with data submitted by facilities as <br /> part of the NOI application for coverage under the VOC General Permit. The Regional <br /> Water Board analyzed effluent quality data collected fiom 2004 to 2011 for a total of 55 <br /> facilities (43 from the VOC General Permit and 12 from the Fue1 General Permit) in the <br /> San Francisco Bay Region. Effluent monitoring data from three NOIs received after the <br /> July 15, 2011, due date were not included in this RPA. <br /> From this analysis, it was concluded that the data for metals would be excluded for use in <br /> RPA pursuant to SIP 1.2. The reason is that the metals were detected only occasionally <br /> and at low levels likely from natural background in the groundwater. <br /> c. Ambient Background Data <br /> The SIP states that, for calculating WQBELs, ambient background concentrations are <br /> either the observed maximum ambient water column concentrations or, for objectives <br /> Attachment F—Fact Sheet F-19 <br /> For VOC and Fuel General NPDES Permit No.CAG912002 <br />