Calculating Numerical Local Limits

1. Calculating NumericalLocal Limits Texas Commission on Environmental Quality Texas Pollutant Discharge Elimination System Pretreatment Program

2. Overview of Methodology for Developing Local Limits Step 1: Develop a Sampling Plan Step 2: Collect Data for Technically Based Local Limits (TBLLs) Development Step 3: Develop Maximum Allowable Headworks Loadings (MAHLs) Step 4: Determine Maximum Allowable Industrial Loading (MAIL) Step 5: Account for Required Best Management Practices (BMP) Reductions Step 6: Allocate Allowable Industrial Loading

3. The Sampling Plan contains: The initial influent pollutant scan with Quality Assurance/Quality Control (QA/QC) Sample chain-of-custodies (COCs) with the description of the sampling location(s) Documentation of approved 40 CFR Part 136 analytical methods A schematic showing the layout for each wastewater treatment plant (WWTP) Sampling for influent and effluent, will the POTW consider the lag time for treating wastewater (plant retention time The sampling locations for the seven (7) day sampling events for influent, effluent, and sludge clearly marked on the schematic A detailed explanation of the location(s), frequency, and number of samples of the Domestic/Commercial background sampling (with no significant industrial user contributions in that part of the WWTP service area) A definition for identifying a "pollutant of concern" (POC) as any pollutant found at or above 0.1 milligrams per liter (mg/L) and any other pollutant the publicly owned treatment works (POTW) and/or State may designate to be of concern List the POCs for which seven (7) day sampling events will be conducted and local limits will be developed (including the 15 national POCs) Step 1: Sampling Plan

4. The Sampling Plan contains: List of pollutants to be sampled and flows to be measured for those pollutants to be reduced from IUs with the required BMPs Statement that if hauled waste is accepted, a discussion of the handling procedures and quantities and qualities of hauled waste will be provided with the TBLL submittal Identification of personnel or positions responsible for technical review, monitoring, laboratory analysis, and administration Description of sampling equipment or other provisions to conduct necessary sampling Description of adequate analytical capabilities to perform analyses A statement that the POTW has all chain-of-custody information on-file and that the records will be maintained on-site as long as the current local limits are in effect Authorized a representative, i.e. the POTW permit signatory or a consulting firm, to sign and certify the Sampling Plan Step 1: Sampling Plan

5. Step 2: Collecting Data forLocal Limits Development Identify Pollutants of Concern Detemine Applicable Environmental Criteria Collect Site Specific Data from: - Publicly Owned Treatment Works (POTW) - Industrial Users (IUs) - Domestic/Background Sources - Nonsignificant IU with required BMPs Conduct Headworks Analysis

6. U. S. Environmental Protection Agency (EPA) and State Requirements 15 National Pollutants of Concern: Cd, Cr, Cu, Pb, Ni, Zn, As, CN, Ag, Hg, Selenium, Molybdenum, BOD5, TSS, Ammonia [for plants with sources] Texas Pollutant Discharge Elimination System (TPDES) Permit Limits Applicable Water Quality Standards Historical Problems (i.e. process inhibition) Sludge Disposal Considerations Worker Health and Safety Considerations Collection System Considerations Other (RCRA, Clean Air Act, CERCLA, Drinking Water Standards) Determining Pollutants of Concern • Criteria

7. Determining Pollutants of Concern • Data Sources • $TPDES Permit • $Water Quality Standards/Criteria • $Sludge Standards • $Industrial Waste Survey Review • $Industrial User Compliance Monitoring • $Local Limits Monitoring Program • IUs • POTW • Domestic/ Commercial Background • Nonsignificant IUs or significant industrial users (SIUs) with required BMPs to reallocate the TBLLs • Receiving stream (STORET, State, USGS) • Literature/Default Data

8. Monitor Domestic Pollutant Loadings Monitor Trunk Lines Receiving Only Domestic/Commercial Wastewaters If site-specific data cannot be obtained, literature values are available Domestic/Commercial Loading

9. Removal Efficiencies: Mean Influent/Effluent Loadings R.E.= Removal Efficiency, as a decimal ¦ = Mean Influent Loading, lb/day  = Mean Effluent Loading, lb/day

10. Step 3: Develop Maximum Allowable Headworks Loadings (MAHLs) Conceptually, in order to protect water quality standards, calculating MAHLs is an exercise in back calculation to meet National Pollutant Discharge Elimination System (NPDES) permit requirements My NPDES permit allows me to discharge x pounds of copper into the stream. I know from sampling that my treatment plant removes, on average, 70% of the copper that comes in. How much copper can I allow to enter my plant without violating my NPDES permit?

11. Development of Maximum Allowable Headworks Loadings • <MAHLs are typically based on the most stringent of: • $NPDES Pollutant Discharge Limitations and Permit Requirements • $Water Quality Standards or Criteria • $Treatment Plant Process Inhibition Levels/ Operational Problems • $Sludge Disposal Standards

12. Subtract Domestic/Commercial Background Contributions Subtract Safety/Growth Factors - 5 to 20% Step 4: Determine Maximum Allowable Industrial Loading

13. Determine Maximum Allowable Industrial Loading (MAIL) MAIL = Maximum allowable industrial loading, lb/day MAHL = Maximum allowable headworks loading, lb/day SF = Safety Factor, as a decimal CDOM = Domestic/Commercial background concentration (mg/L) QDOM = Domestic/Commercial flow (MGD) 8.34 = Unit conversion factor Possible Outcomes: - positive MAIL (good) - negative MAIL (bad)

14. At this point in the TBLLs calculations, the POTW will need to decide if they would like to account for BMP loading reductions, from either SIUs or non-significant IUs, according to the October 14, 2005 Pretreatment Streamlining Rule. The BMPs should be designed to reduce concentrations to specified concentrations, domestic/commercial background levels, or below the MALs. Step 5: Account for Required BMP Reductions

15. BMP Reductions LBMP= Loading attributed to contributing domestic/commercial and nonsignificant IUs with required BMPs, lb/day CBMP= Estimated or measured average pollutant concentrations of the pollutants being reduced to “Zero” by the BMP from contributing domestic/commercial and nonsignificant IU discharges, mg/L QBMP = Flow from the contributing domestic/commercial and nonsignificant IUs with required BMPs, MGD 8.34 = Conversion Factor

16. BMP Reductions LBMP = The loading that may be added to the MAIL due to the contributing commercial and nonsignificant IUs incorporating required BMPs, lb/day CBMP = The reduction in the average concentration from the contributingcommercial and nonsignificant IUs incorporating required BMPs down to a specific concentration QBMP = Flow from the commercial and nonsignificant IUs that will implement the required BMPs, MGD 8.34 = Conversion Factor

17. If using the TBLL uniform allocation method, calculate the MAILBMP, accounting for BMP loading reduction, by subtracting the BMP reduction from the Domestic and Dommercial loading to determine the remaining Domestic and Commercial loading (LRDC). If the contributing commercial and nonsignificant IUs with required BMPs are reducing their concentrations to below the MAL or “Zero”, you may subtract the entire BMP loading reduction. Account for Required BMP Reductions

18. BMP Reductions LRDC= The remaining domestic/commercial loading, lb/day LDC = Domestic/Commercial Loading, lb/day LBMP= Loading attributed to contributing commercial and nonsignificant IUs with required BMPs discharges, lb/day

19. BMP Reductions MAILBMP = Maximum Allowable Industrial Loading accounting for BMP loading reduction, lb/day MAHL = Maximum Allowable Headworks Loading, lb/day LSF= Loading attributed to safety factor, lb/day LRDC = Remaining Loading attributed to domestic/commercial Loading, lb/day

20. BMP Reductions CTBLLBMP = Uniform Concentration TBLL, accounting for domestic/commercial BMP reductions, mg/L MAILBMP = Maximum Allowable Industrial Loading, accounting for domestic/commercial BMP reductions, lb/day QSIU = Industrial Flow, MGD 8.34 = Conversion Factor

21. SIU BMP Reductions QSIU = Flow from SIU facilities [noncategorical SIUs and categorical industrial users (CIUs)] that are subject to numeric TBLLs, MGD QRSIU = Flow from remaining SIU facilities that will have adjusted numeric TBLLs because of the SIU BMP reductions, MGD QSIUBMP = Flow from SIU facilities that will implement required BMPs, MGD

22. SIU BMP Reductions LBMP = (8.34)(QSIUBMP)( CBMP) LBMP = The loading that may be added to the MAIL due to the contributing commercial and nonsignificant IUs incorporating required BMPs, lb/day CBMP = The reduction in concentration from the initial allowable TBLL concentrations of “X” mg/L down to the concentration of “Y” mg/L which is the BMP numeric limit QSIUBMP = Flow from the SIUs that will implement the required BMPs, MGD 8.34 = Conversion Factor

23. SIU BMP Reductions MAILRSIU = Maximum Allowable Industrial Loading for the remaining SIUs that will have adjusted numeric TBLLs because of the SIU BMP reductions CTBLL = Initial allowable TBLL concentration of “X” mg/L QRSIU = Flow from remaining SIU facilities that will have adjusted numeric TBLLs because of the SIU BMP reductions, MGD LBMP = The lb/day loading that may be added to the MAIL due to the SIUs incorporating required BMPs

24. SIU BMP Reductions CRSIUTBLL = Uniform Concentration TBLLs for the remaining SIUs that are not incorporating SIU BMPs and will be subject to the adjusted TBLLs for each specific BMP pollutant, mg/L MAILRSIU = Maximum Allowable Industrial Loading, accounting for SIU BMP reductions, lb/day QRSIU = Industrial Flow from the remaining SIUs that are not incorporating SIU BMPs and will be subject to the adjusted TBLLs for each specific BMP pollutant, MGD 8.34 = Conversion Factor

25. The U.S. Environmental Protection Agency (EPA) has indicated that management plans required for categorical pretreatment standards are now classified as BMPs However, the BMPs described during the TBLL process are designed to reduce the loading to affect the TBLL allocation, not to fulfill categorical BMP requirements Required BMPsTBLL Reallocation vs Categorical Pretreatment Standards

26. Step 6: Allocate Allowable Industrial Loading to Industrial Users • <Four Allocation Methods: • $Uniform Concentration Method • $Industrial Contributory Flow Method • $Mass Proportion Method • $Selected Industrial Reduction Method

27. Applies only to IUs discharging the pollutant above Domestic/Commercial background levels IUs discharging less than Domestic/Commercial background levels are considered Domestic/background sources and held to Domestic/Commercial background levels Industrial contributory flow uses the total flow from the IUs discharging pollutants above Domestic/Commercial background levels Single concentration limit for IUs contributing in excess of Domestic/Commercial background levels Industrial Contributory Flow Method

28. Allocation in proportion to IU loading Different mass limit for each IU Mass Proportion Method IU Specific Method

29. Allocation method is usually remedial in nature Selected IUs are required to reduce loading on a Case-by-Case basis Usually based on wastewater treatability potential Selected Industrial Reduction Method

30. After developing and allocating TBLLs, the POTW needs to determine whether they make sense Do they pass a “common sense test”? Do the Local Limits Make Sense?

31. Be reasonable Be at or above sampling detection levels If below detection levels, the POTW must adopt calculated value, but measure compliance at the MAL Not be so lenient as to provide IUs the opportunity to discharged excessive pollutant loadings or encourage hazardous waste to be discharged Local Limits Should...

32. A timeline must be established for the implementation of the BMPs Initial estimates of loading reductions are verified through: Sampling of selected Users that have implemented BMPs or Evaluating influent loadings for pollutants being addressed by BMPs BMPs - Timelines

33. Loading adjustments may be needed for: Allowable headworks loadings, The numeric limits, or The BMPs for any affected sectors BMPs and Loading Adjustments