American Coatings Association

ACA Attends Public Hearing on Copper in Newport Bay


On Oct. 28, ACA attended a public hearing hosted by California’s Santa Anna Regional Water Quality Control Board (Water Board) to discuss the board’s proposed Basin Plan Amendments to Incorporate Total Maximum Daily Loads (TMDLs) for Copper and Non-TMDL Action Plans for Zinc, Mercury, Arsenic and Chromium in Newport Bay.

In order to meet the dissolved copper saltwater criteria specified in the 2000 California Toxics Rule (CTR), the Water Board’s draft Basin Plan Amendments called for an 83% reduction of copper antifouling coatings over the next 15 years.  The plan also called for boat owners to switch to alternatives antifouling coatings and well as follow best management practices for hull cleaning.

Copper-based antifouling coatings are intended to prevent the encroachment and/or growth of marine organisms (such as barnacles, tubeworms, mollusks, and algae) on the hull or surfaces of structures or vessels immersed and operating in seawater. Fouling increases surface resistance to vessel movement, thereby reducing the speed of the vessel and increasing fuel consumption to maintain speed. In some instances, fouling will also interfere with the operation of equipment or cause the weight design limitations of a structure to be exceeded. Fouling occurs most rapidly on static and slow-moving vessels. The fouling environment is also most intense where nutrients are concentrated, such as coastal areas due to run-off from land; environmental conditions, such as temperature, salinity, pH, etc., also play a role. Hence, the most effective antifouling agents or compositions are broad spectrum (i.e., those that kill or inhibit the settlement of as many organisms as possible).

During the workshop the City of Newport stated that it believes the Water Board has used outdated science, and that its conclusion to restrict the use of copper containing antifouling coatings is inappropriate. The City further challenged the Water Board’s opinion that alternative antifouling coatings would be as effective and would not result in an unintended environmental impacts.

The Water Board has said there will be at least one more public workshop before the Basin Plan Amendments are returned for consideration.


Historically, organotin compounds such as tri-butyl tin (TBT) were used in most high performance antifouling coatings until they were banned more than two decades ago. Since then, copper-based substitutes (typically cuprous oxide) have become the most widely used alternative. However, a concern regarding dissolved copper from these coatings systems has been identified in certain poorly flushed basins and in crowded marinas where these metals may accumulate and exceed the Clean Water Act standard for copper, which is 3.1 μg/L in marine waters.

California and the U.S. EPA are conducting TMDL studies to measure amounts and sources of pollution affecting a particular body of water, and then propose regulations designed to reduce discharges to bring pollutant levels below harmful levels.

Contact ACA’s Stephen Wieroniey or Allen Irish for more information.