Most boat bottoms are coated with anti-fouling paints to prevent biological growth that can reduce boat speed and fuel economy. This bottom paint typically contains high concentrations of copper as its active ingredient. Copper is a very effective deterrent to bottom fouling, however, it is harmful to marine organisms.
Even with a coat of bottom paint, most vessels need to have their hulls cleaned once a year to remove biological growth. The most popular and efficient method is to power- or pressure-wash the hull once the boat is hauled from the water by using a high-pressure stream of water over the boat bottom while the boat is situated over a travel-lift well or on a boat ramp. The resulting washwater contains fouling organisms and paint chips, and if not properly managed, may contaminate surface water and groundwater.
The state of Maine conducted a study in 2002 to determine what contaminants are in the bottom paint, washwater, and bottom sediments surrounding the wash area. The study was performed at boatyards and marinas with marine railways that typically perform pressure washing in the intertidal zone where washwater flows directly and into the water. The Maine study revealed that in addition to the expected high copper levels, lead levels were unexpectedly high. Here are the state's data:
|Contaminant*||Paint sanding dust||Washwater||Bottom sediment after washing||Bottom Sediment 5 months later|
|Copper||228-330,000 ppm (33%)||20-170 ppm||35,000 ppm (3.5%)||750 ppm|
|Lead||269-9,900 ppm||0.2-3.7 ppm||640 ppm||88 ppm|
|Zinc||~2,100 ppm||5.4-15 ppm||8,400 ppm||390 ppm|
|Background Levels: Copper - 0.028 ppm, Lead - 0.007 ppm, Zinc - 0.019 ppm|
* For reference, standards for drinking water are: 1.3 parts per million (ppm) for Copper, 0.015 ppm for Lead, and 5 ppm for Zinc
These data and other studies on contaminants in pressure washwater demonstrate that treatment of this wastewater is necessary to meet state and federal discharge limits before discharging to coastal waters, sanitary sewers, or into the ground (groundwater).
Most marinas or boatyards performing boat maintenance outdoors are required to have permit coverage under the National Pollutant Discharge Elimination System (NPDES) Stormwater Multi-Sector General Permit for Industrial Activities. To date, Massachusetts has not been delegated to administer this program. Therefore marinas in Massachusetts must follow the federal permit rules. The NPDES stormwater permit specifically prohibits the inclusion of pressure washwater in stormwater discharges. As a result, facilities need an individual NPDES permit, if the pressure washwater is discharged directly to coastal waters. If discharging onto a permeable surface, such as gravel, facilities need a groundwater discharge permit. A permit is also required for discharge to a sanitary sewer. Discharge to a septic system is prohibited. Regardless of the discharge option, these permits require significant pretreatment of the wastewater prior to discharge. All pretreatment systems (for discharge) likely need to be run by a state certified operator. In addition to the wastewater, some solids are generated, which need to be analyzed and disposed of properly.
As part of a comprehensive effort to assist marinas in tackling this difficult issue, the Massachusetts Office of Coastal Zone Management (CZM) awarded $12,500 each to Cape Ann Marina in Gloucester and Arey's Pond Boatyard in Orleans for the installation of treatment systems to remove pollutants from pressure washwater. In December 2004, each of these facilities hosted a demonstration event that allowed the general public, marina operators, and state officials to view the funded systems. Progress has been made since then and a number of facilities have installed washpads and wastewater treatment systems and many more have begun planning for systems.
In addition to these demonstration projects, and recognizing that the pressure washing information in the Massachusetts Clean Marina Guide was incomplete, CZM has developed a pressure-washing addendum to the guide. A Guide to Selecting Pressure Washing Management Practices and Technologies: Supplement to the Massachusetts Clean Marina Guide file size 1MB provides guidance to marinas and boatyards about the proper handling and disposal of wastewater and solids generated when boat hulls are cleaned, including a review of relevant regulations, pressure washwater disposal options, and equipment that can be used to minimize impacts from pressure washing practices.
Please contact Robin Lacey, CZM's Marina Technical Assistance Specialist, if you have any questions about the demonstration projects, pressure washing, or general environmental management questions related to clean marinas.