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

Overview Data Sources Model Constraints Decision Criteria Calculations and Evaluations Conclusions

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

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

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

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

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)

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

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

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 500 lbs/day (  1% of the total average daily PS load to the entire Harbor) were included in the model.

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.

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

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

Example Evaluation Table

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

Nutrients Point Source Loads

Overview Data Sources Conclusions

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

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

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

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