Point Source Loads and Decision Criteria for Toxics Modeling

1. Point Source Loads and Decision Criteria for Toxics Modeling Baltimore Harbor TMDL Stakeholder Advisory Group September 10, 2002

2. Overview • Data Sources • Model Constraints • Decision Criteria • Calculations and Evaluations • Conclusions

3. Data Source Evaluation • MDE reviewed several sources of data • Permit Compliance System (PCS) • EPA NPDES compliance database • Toxic Release Inventory (TRI) • Right to Know database of sources and quantities • Toxic Loadings Release Inventory (TLRI) • CBP developed database

4. Data Source Evaluation • PCS Data – • Data is generated by NPDES permit holders by submitting Discharge Monitoring Reports on a monthly or quarterly basis • Data collected by MDE and entered into EPA maintained database • Measured Values

5. Data Source Evaluation • Toxics Release Inventory • Data generated by industry to comply with Right to Know Act • Data collected by MDE and entered into EPA database • Data not available for all sources in Harbor watershed – variable reporting thresholds • Data not measured in many cases – engineering calculations or mass balance estimates

6. Data Source Evaluation • Toxics Loading Release Inventory (1999) • Database generated by Chesapeake Bay Program • Data is for Major (>0.5MGD) discharges • Source of Data is PCS

7. Model Constraints • CH3D Hydrodynamics Model • Point sources are entered into a model grid • Individual sources create new sets of interaction equations – these consume significant computer memory and lead to increased model run times • Sensitivity of the model to flow • Low flows do not significantly influence hydrodynamics • Data requirements – (i.e., complete data sets)

8. Decision Criteria • Point Sources and load estimations • MDE calculated PS loads using two techniques estimated load = (maximum concentration * average flow) estimated load = (average concentration * average flow) In cases with detection limits reported - the DL was assumed as the maximum concentration • Comprehensive goals were established • Capture 95% of the PS load and • Capture sources that constitute >1% of total daily PS load

9. Source Criteria for Small Flows • The Harbor was separated into its five major regions – Inner Harbor, Middle Branch, Curtis Creek, Bear Creek, and the Middle/Outer Harbor • Within these regions, flows were ranked based on the % of total average daily point source flow • Sources that contributed <5% of total flow for a given region were excluded from the model • However, sources that constituted >5% of total point source flow for a given region and were <0.5 MGD were excluded from the model

10. Source Criteria for TSS • The Harbor was separated into its five major regions – Inner Harbor, Middle Branch, Curtis Creek, Bear Creek, and the Middle/Outer Harbor. • Within these regions, TSS loads were ranked based on the % of total average daily PS load • Sources that contributed <5% of total TSS load for each region were excluded from the model. • However, sources that constituted <5% of total point source load for each region and were >500 lbs/day (1% of the total average daily PS load to the entire Harbor) were included in the model.

11. Criteria for Zn, Pb, and Cr • The Harbor was separated into its five major regions – Inner Harbor, Middle Branch, Curtis Creek, Bear Creek, and the Middle/Outer Harbor. • Within these regions individual metals ranked based on the % of total average daily point source load • Each region was dominated by a single source • For Cr, Zn, and Pb sources baselines were established at 1% of the total average daily load • Sources that constituted 100% of the load in regions and were under the baseline were excluded from the model.

12. Load Calculation Overview • PCS Data queried and sorted • Average monthly flow rates selected • For industries with quarterly sampling the flow value collected was used for the entire quarter • Monthly conc. values defined (max and ave.) • For industries with quarterly sampling the conc. value collected was used for the entire quarter • Daily load values calculated • Average daily loads calculated and evaluated with decision criteria

13. Example Calculation Load (lb/day) = Concentration max (mg/l) * Flow avg (MGD) * 8.345 Where 8.345 is the conversion factor from mg/L and MGD to lb/day

14. Example Evaluation Table

15. Conclusions • Load data along with the evaluation criteria was sent to point source dischargers during the last week of August • We have received comments and expect to receive more – further discussions will follow to finalize load values

16. Nutrients Point Source Loads

17. Overview • Data • Sources • Conclusions

18. Data for Modeling • MDE nutrient database prepared for the Chesapeake Bay Program eutrophication model. – PCS data plus monthly operating reports and permit application data

19. Modeling Point Sources • Based on established MDE nutrient TMDL protocols • ALL point sources will be included in the model and • ALL point sources will receive allocations • However, ONLY major (>0.5 MGD) sources will be subject nutrient reductions

20. PS Calculation • PCS Data queried, sorted, and downloaded to MDE database • Average monthly flow rates selected • Average monthly conc. values selected • Daily load values calculated

22. Conclusions • PS Load data – external review expected within next few weeks • Fewer PS locations allow for inclusion of all into model framework