Appendix 1 for 2480 - Modeling to determine the maximum allowable leach rate for copper-based antifouling products in California marinas - Xuyang Zhang and Nan Singhasemanon

DPR is required by law to determine a copper leach rate for antifouling paint pesticides for the protection of aquatic environments. Five scenarios representing various levels of copper loading were defined. For each scenario, a leach rate was calculated by the MAM-PEC model that limits dissolved copper concentrations in the marina to below the California saltwater chronic water quality standard of 3.1μg/L. Copper leach rates were calculated for 5 different marina scenarios based on hull cleaning techniques and frequency of cleaning events. The maximum allowable leach rate ranged from 0.46 to 24.6 μg/cm/day depending on the scenario, cleaning frequency, and cleaning methods. About 5–100% of current registered products have leach rates that are higher than the derived leach rates. Leach rates calculated for the BMP and non-BMP decreased from those determined for no cleaning. When the cleaning frequency was decreased to monthly, leach rates were increased by 25% for BMP scenarios and 9% for the non-BMP scenarios. Converting to non-copper alternatives can also reduce copper loading and consequently affect the selection of maximum allowable leach rates. This analysis will serve as a basis for decision making on scenario selection and final leach rate determination.