United States Environmental Protection Agency
           Office of Wastewater Management
           Washington, DC 20460
Underwater Ship Husbandry
                                  EPA 800-R-11-004
                                  November 2011

Underwater Ship Husbandry Discharges                                        Table of Contents

                                Table of Contents


      1.1   What is Underwater Ship Husbandry?	1
      1.2   Environmental Impacts of Hull Husbandry	2
      1.3   Survey of Regulations and Guidelines for Hull Husbandry	2

      2.1   Immobile Periods	7
      2.2   Vessel Speed	8
      2.3   Voyage Duration	8
      2.4   Vessel Movement Patterns	9
      2.5   Environmental Factors (Salinity, Temperature and Nutrients)	10

      3.1   AFCs Containing Biocides	11
      3.2   Non-Biocidal AFCs	12
      3.3   Best Management Practices for AFC Leachate	13


      5.1   U. S. Navy Advanced Hull Cleaning System (AHCS) and Automated Hull
            Maintenance Vehicle (AHMV)	16
      5.2   Scat Harding (Norway) CleanHull AS	17



Underwater Ship Husbandry Discharges                                             List of Tables

                                  LIST OF TABLES


Table 1.  Summary of Current International and U.S. Management Strategies for
       Underwater Ship Husbandry	4

Table 2.  Hull Husbandry Best Management Practices (BMPs) for International
       Organizations, the U.S., States and Classification Societies	15
Table 3.  Estimated Costs of One-Time Out-of-Water and Underwater Hull Husbandry	19
The EPA technical contacts for this document are Ryan Albert (202) 564-0763 and Robin Danesi

Underwater Ship Husbandry Discharges                                        Section 1 - Introduction

                                                                        SECTION 1


       The 2008 Vessel General Permit (VGP) regulates discharges incidental to the normal
operation of vessels operating as a means of transportation. The VGP, like other general permits,
is issued by the permitting authority (in this case, EPA) and covers multiple facilities within a
specific category for a specific period of time (not to exceed 5 years).  The 2008 VGP includes
the following limits or requirements: general effluent limits applicable to all discharges; effluent
limits applicable to 26 specific discharge streams; narrative water-quality based effluent limits;
inspection, monitoring, recordkeeping, and reporting requirements; and additional requirements
applicable to certain vessel types (USEPA, 2008a).

       Because EPA plans to reissue the VGP, the Agency continues to gather information on
vessel wastewater sources while examining technologies that can be used to remove pollutants
before discharge into waters of the United States.1 This document contains updated information
on recent developments in best management practices (BMPs) for reducing pollutant discharges
during underwater ship husbandry.


       Underwater  ship husbandry is the maintenance of the underwater portions of a vessel.
Underwater ship husbandry, commonly referred to as hull husbandry,  is usually initiated in
response to marine biofouling of the underwater hull and hull appendages of boats and ships
including propellers, rudders, through-hull fittings, and corrosion control equipment. While
certain hull husbandry activities such as inspection, cleaning and application of antifouling
coatings (AFCs) take place out of the water (in dry dock, slipway or haul-out facilities) others
such as hull cleaning and propeller polishing are carried out while the vessel is afloat.

       Hull husbandry is practiced by the shipping industry primarily for economic reasons.
Biofouling on a ship's hull increases the hydrodynamic drag of the vessel, leading to increased
fuel consumption (Chambers et al., 2006). For example, annual  cleaning has been estimated to
reduce fuel consumption for a 175 m long container ship by 9,000 tons over a 5-year dry docking
period (Schat Harding,  2009). Depending on  the type of vessel,  fuel may make up about 50
percent of the operational costs of a ship, and it has been estimated that fouling increases the
annual fuel consumption of the world's commercial shipping fleet by 40 percent,  or 120 million
tons of fuel at a cost of about $ 7.5 billion per year (2000 dollars) (GISP, 2008).

       Hull husbandry controls biofouling and microbial induced corrosion of the ships'
propulsion and  seawater cooling systems which can lead to poor maneuverability and engine
damage (Chambers  et al., 2006).
 "Waters of the United States" as defined in 40 CFR 122.2.

Underwater Ship Husbandry Discharges                                        Section 1 - Introduction

       Hull husbandry practices can have environmental consequences. Two important issues
for aquatic ecosystem health that are directly related to hull husbandry include (1) the discharge
of toxic chemicals used as biocides in AFCs and (2) biofouling as a vector for aquatic nuisance
species (ANS) transport. Underwater hull cleaning using currently available methods can release
both toxic chemicals and ANS into receiving waters.

       Virtually all vessels that are  kept in saltwater use AFCs (Minchin and Gollasch, 2003) to
control biofouling of the hull and other underwater equipment. The AFCs that contain biocides
prevent the attachment of aquatic organisms to the hull by continuously leaching substances into
the surrounding water that are toxic to aquatic life. While a variety of different ingredients may
be used in these coatings,  the most commonly used biocide is copper. Copper can inhibit
photosynthesis in plants and interfere with enzyme function in both plants and animals in
concentrations as low as 4 jig/1 (Takata et al., 2006). The release of biocides such as copper from
hull coatings could lead to water quality impairments, particularly in crowded boat basins. For
this reason, copper containing-AFCs are under regulatory scrutiny in a number of locations in the
U.S., especially the southern California coastal areas.

       Vessel biofouling has been identified as an important pathway for the transport and
introduction of ANS (Johnson et al., 2007).  While ballast water receives the most attention
regarding the movement of ANS, hull fouling is also a significant vector. For example, 90
percent of the 343 marine aquatic invasive species in Hawaii are thought to have arrived through
hull fouling (Carlton, 2001), while 36 percent of the nonnative coastal marine species established
in continental North America could be attributed to hull fouling (Bax et al., 2003). In
comparison, ballast water, by itself, may account for 20 percent of documented invasions
(Carlton, 2001). Over the  last decade,  the possible transfer of species by hull fouling  has received
growing attention and is now recognized as one of the most important pathways of ANS
translocation (Candries, 2009).


       Internationally, the 2001  International Convention on the Control of Harmful  Anti-
fouling Systems on Ships, which entered into force in September of 2008, prohibits the use of
harmful organotins such as tributyltin (TBT) in AFCs used on international vessels and
establishes a mechanism to prevent the potential future use of other harmful substances in anti-
fouling systems.  The International Marine Organization's (IMO) Marine Environmental
Protection Committee (MEPC) adopted Guidelines for the Control and Management of Ships'
Biofouling to Minimize the Transfer of Invasive Aquatic Species at MEPC 62 in July  2011 (IMO,
2011). The management measures outlined within these voluntary guidelines are intended to
complement current maintenance practices carried out within the industry. Specifically, the
Guidelines address:

             Choosing the anti-fouling system: Different anti-fouling systems are designed
              for different ship operating profiles.

Underwater Ship Husbandry Discharges                                         Section 1 - Introduction

             Installing, re-installing, or repairing the anti-fouling system: Whether
              installing, re-installing or repairing the anti-fouling system, care should be taken
              in surface preparation to ensure all biofouling residues, flaking paint, or other
              surface contamination is completely removed, particularly in niche areas, to
              facilitate good adhesion and durability of the anti-fouling system.

             Procedures for ship maintenance and recycling facilities:  Ship maintenance
              and recycling facilities should adopt measures (consistent with applicable national
              and local laws and regulations) to ensure that viable biofouling organisms or
              chemical and physical pollutants are not released into the local aquatic

       Despite the use of effective anti-fouling systems and operational practices, the MEPC
Biofouling Guidelines acknowledge that undesirable amounts of biofouling  may still accumulate
during the intended lifetime of the anti-fouling system.  To maintain a ship as free of biofouling
as practical, it may be advisable for the ship to undertake in-water inspection, cleaning and

       In the U.S., the Vessel General Permit (USEPA, 2008) limits discharges originating from
AFCs, underwater ship husbandry, and seawater piping fouling. AFCs and chemicals used for
fouling prevention subject to registration under FIFRA (see 40 CFR  152.15) must be
registered,  sold or distributed, applied, maintained, and removed in a manner consistent with
applicable requirements on the coatings' FIFRA label. For biocides not subject to FIFRA
registration (i.e., not produced for sale and distribution in the United States), hull  coatings must
not contain any biocides or toxic materials banned for use in the United States (including those
on EPA's List of Banned or Severely Restricted Pesticides). This requirement applies to all
vessels, including those registered and painted outside the United States. The use of TBT AFCs
is explicitly prohibited under the VGP, and vessels must remove such coatings or paint over
them to prevent toxic leaching2.  Under the VGP, underwater ship husbandry must be conducted
in a manner that minimizes the discharge of fouling organisms and AFCs, and the cleaning of
copper-based AFCs must not produce a visible plume of paint.

       The U.S. Coast Guard currently addresses hull fouling and hull husbandry related to
nonindigenous species through regulations included in 33 CFR 151.2035 that require rinsing of
anchors and anchor chains to remove organisms and sediment, and removal  of fouling organisms
from the hull, piping and tanks on a regular basis. Additionally, although crude oil  tankers
engaged in coastwise trade are exempt from the requirements of 33 CFR 151.2035 by statute,
many tank ship companies conduct voluntary hull maintenance operations, generally in
conjunction with regular dry dock inspections mandated by Merchant Class  Societies such as the
International Association of Classification Societies, Ltd (IACS), and the U.S. Coast Guard.
2 The VGP's zero discharge standard for TBT is consistent with the 1998 Organotin Anti-Foulant Paint Control Act,
33 U.S.C. 2403(a) which generally prohibits application of AFCs containing TBT.  The zero discharge standard is
also consistent with the Convention on the Control of Harmful Anti-Fouling Systems on Ships. The treaty, adopted
by the IMO in October 2001, prohibits the use of organotins in antifouling paints. The treaty entered into force on
September 17, 2008.

Underwater Ship Husbandry Discharges
Section 1 - Introduction
These two entities typically require at least one dry dock inspection of a ship's hull every five
years (Takata et al., 2006; USCG, 2000).

       Three states have also added requirements related to hull cleaning and maintenance as
part of their Clean Water Act (CWA) 401 certifications to the VGP. With the exception of
propeller polishing, California prohibits underwater cleaning on all vessels except those using
biocide-free AFCs. Biocide-free AFCs have been designated as a "best available technology",
and vessels utilizing such coatings may conduct underwater cleaning in California waters
(USEPA, 2008).  Maine and Massachusetts both prohibit underwater cleaning and fouling

       Table 1 provides a summary of the international, United  States, and individual State
regulations regarding hull husbandry.

     Table 1. Summary of Current International and U.S. Management Strategies for
                              Underwater Ship Husbandry
Country or State
New Zealand
Management Strategy
Regulation (Vessels less than
Import Health Standard
Develop a biofouling management plan
Maintain a biofouling recordbook that details all
inspections and biofouling management activities
Install and maintain an antifouling systems
Conduct in-water inspections, cleaning and
Design and construct vessels to minimize
States and territories prohibit underwater cleaning.
Many require containment and disposal of fouling
debris removed during out-of-water cleaning.
Keep ancillary gear and internal seawater systems
clean of marine pests and growths, and
Before departing your last port for Australia:
Clean hull within one month before arrival
Apply antifouling paint within one year
before arrival OR
Book vessel for slipping and cleaning
within one week of arrival (cleaning
should be in a shipway where material
removed can be collected and disposed of
away from the sea)
Vessels arriving from foreign countries would be
required to have a 'clean' hull, meaning no visible
aquatic organisms, other than a slime layer.

Underwater Ship Husbandry Discharges
                                                       Section 1 - Introduction
      Table 1.  Summary of Current International and U.S. Management Strategies for
                                   Underwater Ship Husbandry
     Country or State
   Management Strategy
                          (On Ballast Water
                          Declaration Form)
                             1. When and where was the vessel last dry-docked
                             and cleaned?
                             2. Has the vessel been laid-up for 3 months or more
                             since it was last dry-docked and cleaned?
                             3. Do you intend to clean the hull of the vessel in
                             New Zealand?
                          Voluntary Code of Practice
                          (Fishing Industry)
                            Chartered foreign owned or sourced fishing vessels
                            must be substantially free from plant or animal
                            growth prior to entering New Zealand's EEZ.
                            If no assurance, vessel must be inspected and
                            cleaned before departure.
                            If otherwise inspected in NZ and if necessary,
                            fouling must be removed so no foreign organisms
                            enter the marine environment.
     Australia and New
   Zealand Environmental
    Conservation Council
Codes of Practice
Underwater hull cleaning prohibited, except under
extraordinary circumstances.
Sea-chests, sea suction grids, other hull apertures
may be allowed under permit, if debris not allowed
to pass to water column or sea bed.
Polishing propellers may be allowed under permit.
      United States
                            Underwater ship husbandry must be conducted in a
                            manner that minimizes the discharge of fouling
                            organisms and antifouling hull coatings, and the
                            cleaning of copper-based AFCs must not produce a
                            visible plume of paint.
                            Rinse anchor chains and anchors at place of origin.
                            Remove fouling from hull, piping and tanks on a
                            regular basis. Dispose wastes in accordance with
                            local, state, and federal law.
                          State VGP 401 certification
                             Propeller cleaning is allowed until January 1, 2012.
                            All other underwater hull cleaning is prohibited
                            without special permission from the State Lands
                            Commission (SLC) and State Water Board.
                            Submit annual Hull Husbandry Reporting Form.
                            Rinse anchor chains and anchors at place of origin
                            Remove fouling from hull, piping and tanks on a
                            regular basis. Dispose wastes in accordance with
                            local, state, and federal law.

Underwater Ship Husbandry Discharges
Section 1 - Introduction
     Table 1. Summary of Current International and U.S. Management Strategies for
                               Underwater Ship Husbandry
Country or State
Classification Societies
Management Strategy
Information Framework
Targeting High Risk Vessels
State VGP 401 certification
State VGP 401 certification
(Applies to majority of
merchant fleet)
Pro-active measures: Education/outreach, vessel
arrival monitoring, evaluation for high-risk arrivals
Re-active measures: Rapid response/investigation of
high risk event
Post-event measures: Long term regulations for
high-risk events
Limit time in port
Vessel quarantine
Out of water cleaning
No vessel may conduct underwater hull cleaning
except as part of emergency repairs
Hull husbandry discharges are prohibited within 3
miles of shore.
Dry dock requirements vary somewhat depending
on classification society.
Cleaning and painting is usually conducted, but is at
the discretion of the company.
Interim underwater cleanings are done periodicity at
the discretion of the company, typically dependent
on results of fuel consumption tests.
Source: Takata, 2006.
IMO: International Maritime Organization

Underwater Ship Husbandry Discharges                            Section 2 - Factors Effecting Biofouling

                                                                        SECTION 2


       Biofouling organisms attach to submerged hard surfaces of both naturally occurring and
man-made structures (Railkin, 2004). Species that foul vessel hulls are typical of natural, marine
intertidal and subtidal fouling communities. Marine fouling communities can include arthropods
(barnacles, amphipods, and crabs), mollusks (mussels, clams, and sea slugs), sponges,
bryozoans, coelenterates (hydroids and anemones), protozoans, annelids (marine worms), and
chordates (sea squirts and fish), as well as macroalgae (seaweed). If these fouling communities
become highly developed they can also provide micro-habitats for mobile organisms such as

       Typically, there is a progression of attachment of marine organisms to a vessel's hull
(Floerl et al., 2010). Primary biofouling begins as soon as the surface of a vessel is submerged in
seawater, with the formation of a slime layer consisting of bacteria and microscopic algae. As
the vessel remains submerged in seawater, secondary biofouling occurs as organisms settle on
top of the primary biofouling layer. Secondary biofouling usually includes hard encrusting
animals such as acorn barnacles, bryozoans and serpulid worms, but may also include soft algal
tufts and mobile amphipods. If the hull is coated with an AFC containing a biocide, the toxicant
will act to deter the attachment of higher forms such as barnacles and tubeworms, but will
usually allow primary biofouling within days or weeks of launching with fresh AFC.

       Although biofouling progresses in a predictable manner, it is not a uniform process. For
example, biofouling is not evenly distributed on submerged portions of vessels because a vessel's
hull is not a uniform surface. Certain movement patterns and environmental factors have been
observed to affect the diversity (variety of species) and the  quantity of biofouling observed on
commercial vessels. The factors likely to affect the rate of biofouling include:

             Immobile periods;
             Vessel speed;
             Voyage duration;
             Voyage movement patterns; and
             Environmental factors (salinity, temperature and nutrients).

These factors influence the ability of free swimming or floating organisms to attach to a vessel
and remain affixed, or affect the ability of the organism to survive voyages. Each of these
factors is discussed in the following sections.


       The level of fouling is related to the amount of time a vessel spends in port (Cordell et al.,
2009). In general, the longer a ship stays pierside, the more likely it is to accumulate fouling.
Many floating or free swimming organisms are better able to attach or "settle" on surfaces while
vessels are immobile, and vessels that spend long stationary periods have been observed to have
heavier fouling communities (Coutts, 1999). Because larval settlement may be prevented by
speeds as slow as 2 knots (Davidson et al., 2006), accumulation predominantly occurs while a
vessel is docked, and increases over time. This is especially true in protected ports with restricted

Underwater Ship Husbandry Discharges                            Section 2 - Factors Effecting Biofouling
flow and poor flushing where propagules (the small, dispersing larval phase of marine
invertebrate life cycles) may be retained in the water column for long periods of time (Takata et
al., 2006).

       Assuming suitable environmental conditions, biofouling is likely to increase with the
residence time of a vessel (Floerl et al., 2005), by providing attached organisms sufficient time to
become reproductively viable. However, it is worth noting that some vessels may also visit a port
or region where suboptimal environmental conditions prevail (e.g. low salinity, high turbidity),
and in such cases, ANS release risks may be mitigated through die-off of the fouling organisms.

       Typically, most commercial ships operate the majority of the time, while naval vessels
may spend long periods of time pierside. For example, commercial ships may be at sea 85
percent or more as they only generate revenue when delivering cargoes (Bohlander,  2009), the
exception being commercial vessel inactivity due to economic downturn. In contrast, the general
operating cycle for the U.S. Navy vessels is between 40-60 percent pierside with the rest at sea
(US Navy and USEPA, 2003). With the decline in fish catches in many parts of the world, many
commercial fishing vessels are underutilized and poorly maintained, with vessels being laid up
and/or sold off for other purposes. These vessels may represent a considerable risk in terms of
hull fouling due to the time they are pierside (Candries, 2009).


       Vessel speed influences the quantity and diversity of fouling species observed on vessels.
At high speeds, many organisms are unable to remain attached to vessel hulls because they
cannot endure the forceful  water moving past the surface. Less robust organisms may be
dislodged or may be unable to survive. In contrast, slow speeds are less stressful, allowing many
fouling organisms to remain attached or continue settling on the vessel surface (Takata et al.,
2011). Thus, slower moving vessels have been observed to accumulate thicker fouling than faster
vessels that travel over 18-20 knots  (Michin and Gollasch, 2003).

       Vessel speed can also affect the survival of invasive species. Long-distance travel is
becoming easier and faster. This enables more invasive species to survive long enough to reach a
new environment (Ruiz et al., 2000). For example, Cordylophora caspia, a hydroid that lives in
both freshwater and brackish water, may have been transported successfully because of an
increase in ship speeds (Johnson et al., 2007)

       Boats that travel at slower speeds are also susceptible to invasions because more species
can attach firmly to their hulls (Michin and Gollasch, 2003). Furthermore, some nontoxic AFCs
may only be effective if the vessel travels regularly at 15 knots to 20 knots (Swain et al., 2001).
Such coatings would be ineffective in preventing attachment of invasive species on hulls of
vessels that seldom or never reach or exceed those speeds (Johnson  et al., 2007).


       Shorter voyages have been observed to be more advantageous for the survival of coastal
fouling organisms and communities than longer voyages. The  prolonged exposure to harsh
physical conditions of the open ocean during a long voyage may be  detrimental to fouling
organisms, or they may be deprived of food for an untenable length  of time (Coutts,  1999). Ships

Underwater Ship Husbandry Discharges                            Section 2 - Factors Effecting Biofouling
with effective AFCs tend to lack fouling if the vessel has traveled for 9.75 days or more in open
waters (Johnson et al., 2007).


       The expansion of global trade has lead to significantly more ballast water, fouled hulls,
and associated organisms moving around the world (Minchin and Gollasch, 2003). Each year
there are approximately 1.7 million visits by vessels to the world's 4,700 ports (Etkin, 2010). In
the U.S., there are about 110,000 annual vessel visits to ports and other places (Miller et al.,

       Large estuaries with international shipping serve as sources for species that become
invasive in other geographic regions. In other words, larger ships likely accomplish most of the
long-distance transport (primary introduction) while commercial fishing and recreational boats
likely contribute to the transport of invasive species along the coast (secondary introduction)
(Johnson et al., 2007).

       Traveling to a wide range of locations may also be an ANS risk factor because it
increases the likelihood that an organism with a broad range  of tolerances will attach to a vessel
hull. Furthermore, a number of ANS have been introduced far outside their places of origin, and
are becoming pandemic. In these cases, the rate of new introductions is accelerating,  possibly
due to increasing sources for secondary introductions, and the spread of physiologically tolerant
ANS (Cohen and Carlton, 1998).

       For example,  secondary introduction poses a risk to Alaska from domestic and coastwise
ports.  Introduced species have  already demonstrated an ability to successfully colonize these
Alaskan waters. A combination  of factors  such as fewer temperature and salinity changes and
shorter voyages may  mean that there is a higher risk of secondary ANS contamination of
Alaskan waters from  vessels traveling on coastal voyages (e.g., from Puget Sound or San
Francisco Bay) than of primary contamination from vessels traveling from more distant

       Cordell et al.  (2009) analyzed shipping patterns in Prince William Sound, Alaska. They
identified two categories of vessels: those  that have set routes and make numerous brief return
trips to the same port, and those that return to port infrequently but stay in port for long periods
of time. The first type presents a risk of repeat inoculations of ANS (potential high propagule
frequency), and the second represents ANS risk based on less frequent inoculations with longer
"incubation" time for ANS to release propagules (potential high propagule volume). Tank ships
and passenger vessels represent the high frequency risk category, while freight and fishing
vessels represent the  high volume risk category. Commercial fishing and commercial passenger
fishing boats share some features of commercial shipping: they travel often and some go to
distant fishing grounds. They  also  share some features of recreational boats: they may spend
much time within a region and many are small craft, whose underwater structures are more like
those of pleasure craft than commercial cargo ships, tugs and barges (Johnson et al., 2007).

       Movements of military vessels also create pathways for ANS introduction. Invasive
species have been documented on the hulls of military vessels in Hawaii. Analyses of benthic
organisms and fishes of Pearl  Harbor sampled in 1996 suggests two periods of relatively high
introduction rates corresponding to wartime  periods. Most of the introduced species with known

Underwater Ship Husbandry Discharges                            Section 2 - Factors Effecting Biofouling
geographic origins have distributions extending to the Indo-West Pacific. However several
species are known from the Red Sea and the Caribbean Sea (Coles et al., 1999).


       The accretion of marine fouling can be highly variable, depending on geographical
location, time of year, and seasonal variations in weather. In general, fouling flourishes during
warmer months and diminishes in cooler months. Due to reproductive periodicity of fouling
organisms, propagule amounts can vary by season, with summer and spring typically having
higher propagule numbers than winter and fall (Davidson et al., 2006). Fouling organisms may
also release viable propagules in response to new environmental cues (e.g., altered salinity or
temperature) in a recipient region and inoculate surrounding habitats including artificial
structures  (Minchin and Gollasch, 2003).

       Vessels that operate in waters with rapid and drastic changes in salinity and temperature,
such as those that pass through both marine and fresh water or conduct transequatorial voyages,
may experience reduced survivorship of fouling organisms by subjecting them to a range of
conditions outside their physiological limits (Davidson et al., 2006; Takata et al., 2006). On the
other hand, Coutts and Taylor (2004) found that vessels that travel through similar latitudes may
experience increased survivorship of fouling organisms by retaining relatively consistent
temperature and salinity levels.

       Ocean warming due to climate change will stimulate the growth of barnacles and other
biofouling organisms, potentially adding billions in operational costs of worldwide shipping
(Williams, 2011). In laboratory tests for which seawater was warmed 3.5C above current
averages (a scenario that represents ocean water temperatures expected in the year 2100),
organisms in a typical biofouling community grew twice as fast as they do under current
conditions, and formed a thicker layer of fouling. In addition, increased fouling from ocean
warming may increase risk of ANS transport.  Ocean warming also compounds the problem of
ANS by opening new routes for invasions, such as the Northwest Passage which has been ice-
free since  2007, and by favoring the colonization, survival, and growth of some invasive species
over native species.

Underwater Ship Husbandry Discharges                    Section 2 - Factors Effecting Biofouling Coatings

       AFCs are the primary mechanism for reducing biofouling of the underwater portions of
vessels. AFCs can be categorized into: a) those that control hull biofouling by releasing biocides
and b) non-biocidal coatings, which (most commonly) provide surface characteristics that inhibit
the attachment and adhesion of biofouling organisms. Each of these types of AFCs are discussed
in the sections below along with best management practices to minimize their release during hull
husbandry activities.


       Virtually all vessels that are permanently kept in saltwater use AFCs, and the majority of
AFCs presently in use contain biocidal chemicals to inhibit the colonization of the vessel's hull
(Minchin et al., 2003).  These chemicals, which are toxic to fouling organisms, are slowly
released from the coated surface into the surrounding waters. The primary constituent used in
most biocidal AFCs is copper, although zinc may also be used as an ingredient.

       While the rate at which the metals leach from coatings is relatively slow (4-17
|ig/cm2/day), these coatings can account for significant accumulations of metals in receiving
waters of ports where numerous vessels are present (USEPA, 2010). Copper-based coatings have
the potential to cause environmental harm. For example, high copper concentrations at
California's Shelter Island Yacht Basis (SIYB) of San Diego Bay threaten sediment quality and
may potentially adversely impact benthic life. The State Water Resources Control Board will
require a 76 percent reduction of copper discharges from antifouling paints in SIYB by 2022
(California Regional Water Quality Control Board, San Diego Region. 2006). Ninety-three
percent of the copper in the  SIYB was attributed to the passive leaching of copper-based AFP
pesticides that have been applied to boat hulls. Copper released from underwater hull cleaning
contributed 5 percent (Singhasemanon, 2010). Other parts of San Diego Bay have been listed on
the California SWRCB  303(d) list of impaired water bodies for dissolved copper and actions  in
other southern California boat basins suggest copper-containing AFCs may soon be restricted
elsewhere in the region (California Regional Water Quality Control Board, Los Angeles Region,
2005; USEPA, 2002).

       Increased biocide release rates may also occur during hull husbandry activities,
particularly if hulls are  cleaned within the first 90 days following AFC application (Schiff et al.,

       The predominant AFCs on the commercial market are briefly discussed below.

Insoluble Matrix / Contact Leaching /Hard Coatings

       Conventional insoluble matrix or  'contact leaching' systems are based on hard, porous
resins that are insoluble and do not erode in seawater (Floerl et al., 2010). Examples of these
compounds include acrylic,  vinyl, epoxy  and chlorinated rubber polymers (AMOG, 2002).
Modern hard-type formulations (which are usually based on modified epoxy matrices) provide
improved control over biocide release rates, particularly for copper-based coatings, with
effective life expectancies of between 24 and 36 months (Floerl et al., 2010).   Of the AFCs
commonly used today, hard-type coatings provide the best resistance to damage by abrasion,


Underwater Ship Husbandry Discharges                    Section 2 - Factors Effecting Biofouling Coatings
affording successful protection for vessels, or areas of vessels, that are subject to elevated levels
of wear. An advantage of this coating type is that the hard, insoluble matrix is resilient to damage
by oxidation, providing a longer coating life Almeida et al., 2007).

Controlled Depletion Polymer /Ablative Coatings

       Controlled depletion polymer (CPD) systems are also known as ablative coatings.
Ablative coatings are designed to slough off layers of matrix and biocides as water moves over
the hull surface, providing a self-polishing mechanism to maintain hull smoothness. This process
also promotes self-cleaning by presenting an unstable, biocidal surface for biofouling organisms.
CPD coatings provide effective biofouling protection and, since thicker layers of CDP coatings
can be applied in comparison to conventional soluble matrix systems, the effective life is
increased to up to 36 months in suitable conditions. However, traditional hull-cleaning
techniques, such as scrubbing, can damage and remove the coating and shorten the life span.
CDP coatings provide the lowest cost per meter squared of AFC and are suitable for use in low
biofouling conditions or by vessels with short drydock intervals (Floerl et al., 2010). They are
widely used by recreational vessels and small ships (Almeida et al., 2007).

Self-polishing Copolymer Coatings

       The ban on the use of TBT as a biocide has prompted the development of alternative
TBT-free self-polishing copolymer coatings (SPCs). This "new technology" of TBT-free SPCs
uses copper acrylate, zinc acrylate and  silyl polymers in-place of TBT (Floerl et al., 2010). TBT-
free SPCs are claimed to provide self-polishing performance, controlled biocide release rates and
long-term performance comparable to TBT-SPCs. New products are marketed with effective
working lives similar to TBT-SPCs (up to 60 months). Almeida et al.  (2007) indicate that the
maximum service life of this type of coating is usually three years, but effective life spans of up
to five years have been reported.

3.2    NON-BiociDAL AFCs

       It has long been a goal of paint  companies to produce an antifouling paint that does not
contain toxic ingredients (Bohlander, 2009). There are several benefits to such a coating,
including less stringent environmental regulation for use and disposal, no or low impact on the
local marine environment from the leaching of toxic ingredients into the water column, reduced
hazards to the shipyard workers applying and removing the paints, and reduced generation of
hazardous materials during application and removal. Recent research and development efforts
have therefore focused on alternative antifouling mechanisms and non-biocidal active
compounds that can provide  'environmentally safe' options (AMOG, 2002).

       Several biocide-free systems  are in development, but currently the systems that have been
developed and successfully marketed are based on "non-stick" silicone based fouling-release
technology. These coating systems provide surface characteristics that aim to prevent the
adhesion of biofouling organisms or  allow biofouling to accumulate, but prevent adhesion as
organisms grow or are subjected to water movement (Floel et al., 2010). Fouling-release coatings
provide an expected effective life of  five years or longer (AMOG, 2002), but are more difficult
and expensive to apply than other AFCs.

Underwater Ship Husbandry Discharges                     Section 2 - Factors Effecting Biofouling Coatings
       Antifouling success of fouling-release coatings currently relies on vessel speed and
movement to dislodge any organisms that do attach. Self-cleaning of hulls has been
demonstrated for vessels that frequently maintain speeds between  15 and 30 knots, depending on
the biofouling community (AMOG, 2002; Chambers et al. 2006; Floerl et al., 2010). Coating
manufacturers claim propulsive fuel efficiencies of 3-11 percent, which can be realized if the
ships using these products cruise at speeds ranging from 10-18 knots, and spend relatively little
time pierside (Floerl et al., 2010). Therefore, this technology is currently  best suited to fast-
moving vessels with rapid port turn-around periods and sufficient activity levels. The fouling-
release AFCs are establishing a market in commercial shipping fleets, primarily with cruise ships
and fast container ships, as these vessels have operational profiles  that are suitable for use of foul
release paints.

       There are several manufacturers of fouling release paints, with a variety of products on
the market. All share the characteristic of generally allowing marine fouling to attach to the
coating while the ship is pierside, then claiming the biofouling will detach with ship movement.
However, it is also possible that ships using fouling release coatings could transfer ANS from
one location to another if the coating does not completely self-clean. There is also likely to be
variability in performance for these products, and while they are in regular  commercial use, it
will take additional time to get a clear indication of the benefits and operating  characteristics of
these materials as well as their potential for ANS transmission. Fouling-release coatings may still
require hull  cleaning. There is a possibility that the cleaning process may damage these coatings,
allowing increased fouling growth. The underwater cleaning of fouling-release or other non-
biocidal AFCs can still pose an environmental  risk via the uncontrolled release of ANS during
the cleaning operation.


       In the 2008 VGP, in addition to prohibiting the discharge of TBT, EPA identified two
main BMPs for control of AFC leachate. The first type of BMP regards applying coatings
according to the instructions on the coating's FIFRA label when applicable. The second type of
BMP addresses the need for particular coatings and selection of the type of coating to apply.
EPA noted that the vessel  owner/operator must consider the fouling rate of the hull and other
underwater areas of the vessel, the vessel's operating speed, the dry docking frequency, and the
waters in which the vessel will be traveling when selecting the appropriate  antifouling system for
a particular vessel.

       A third potential BMP regards matching the coating's abilities or  strength to dry dock
cycles. Larger vessels, particularly those used in trade and cargo transport,  must adhere to
requirements for safety inspections and maintenance activities that dictate how frequently they
must be drydocked. The major manufacturers of hull coatings for this industry guarantee the
effectiveness of their products for a certain period of time based on ship and operational
characteristics; vessel owner/operators could match the hull coating choice  to the appropriate
drydocking interval. By factoring this schedule into the hull coating selection,  vessel operators
could select coatings that would sufficiently protect the vessel for the period of time needed
while reducing unnecessary leachate or wastes.

Underwater Ship Husbandry Discharges                Section 4- Hull Husbandry Best Management Practices

                                                                       SECTION 4


       Regulatory agencies have begun developing BMPs for hull husbandry practices to
prevent and/or control the transport and introduction of ANS by commercial shipping and to
reduce the loss of AFCs to surface waters during hull husbandry activities.  Table 2 summarizes
vessel husbandry BMPs for various international organizations, states and classification

       In general, BMPs for hull husbandry require that rigorous hull-cleaning activities take
place while the vessel is in drydock, or another land-based facility where the removal of fouling
organisms or spent antifouling paint can be contained and treated.  In the 2008 VGP, EPA
required that vessel owner/operators who must perform hull husbandry while the vessel is in the
water should use methods that minimize the discharge of fouling organisms and AFCs. These
methods include (USEPA, 2008):

             Selection of appropriate soft cleaning brush or sponge rigidity to minimize the
              release of paints and hull materials including AFCs  into the water column;

             Limiting use of hard brushes and surfaces to the removal  of hard growth; and

             Use of vacuum cleaning technologies (when available) in conjunction with
              mechanical scrubbing, to minimize the release or dispersion of AFCs and fouling
              organisms into the water column.

       EPA also requires  vessel owner/operators to minimize the release of copper based
antifoulant paint into the water column when they clean the vessel. Cleaning of copper based
antifoulant paints  should not result in any visible cloud or plume of paint in the water, and if
one develops, then the person doing the cleaning should  change to  a softer brush or less
abrasive cleaning technique (USEPA, 2008).

Underwater Ship Husbandry Discharges
Section 4 - Hull Husbandry Best Management Practices
      Table 2.  Hull Husbandry Best Management Practices (BMPs) for International Organizations, the U.S., States and
                                                   Classification Societies

Hull Husbandry


Underwater Hull

Underwater Cleaning
of Sea Chests and
Niche Areas
Propeller Polishing

Rinse Anchors and
Anchor Chains


Follow applicable
requirements for underwater
cleaning. Use cleaning
techniques that minimize
release of biocides for hulls
coated in biocidal AFCs.
Remove macro-fouling
growth in accordance with
regulations. Minimize
release of AFC debris and
viable macrofouling
organisms by soft cleaning
Outlines management
measures for niche areas.

Recommends regular
polishing of uncoated


Whenever possible,
rigorous hull-cleaning
activities should take
place out of water,
where fouling
organisms and AFCs
can be contained. Use
facilities which treat
wash water from high-
pressure washing prior
to discharge.
Use cleaning techniques
(e.g., select appropriate
brush, contain debris
with vacuum system)
that minimize discharge
of fouling organisms
and AFCs. Cleaning
copper-based AFC must
not produce visible
plume of paint.

Rinse to remove
organisms/sediments at
their place of origin.


Remove fouling by physical
cleaning (e.g., hull and niche
cleaning during the vessels
scheduled 5 year out-of-
water dry-docking).

All underwater hull cleaning
is prohibited unless
conducted using the best
available technologies
economically feasible (e.g.,
allowed for biocide-free
AFCs, not allowed for
copper-based AFCs in
impaired waters).

Propeller cleaning is
allowed until January 2012.
After that date, propeller
cleaning will be allowed
only as specified in
regulations adopted by SLC.


Prohibited except as
part of emergency
hull repairs
necessary to secure
the vessel.


All hull cleaning
shall occur while a
vessel is in drydock
or at another
landside facility so
that wash water and
hull cleaning
residuals can be
collected and
disposed of
associated with
under-water ship
(specifically the
removal of fouling
organisms) are
prohibited in waters
within 3 nm.


Generally require
vessels to be dry
docked at least once
every five years.
None of the
societies requires
the hull to be
cleaned while dry
docked, but most
companies do.

Although not
required, most
companies also
conduct interim
cleanings according
to fuel performance
tests, in order to
maintain cost
effective fuel


Underwater Ship Husbandry Discharges             Section 5 - Vessel Husbandry Debris Containment Options

                                                                     SECTION 5


       Underwater hull cleaning can be quite effective at removing marine fouling; however, the
effluent stream from cleaning is difficult to control. Standard underwater hull cleaning tools,
including multi-brush and single brush tools, typically have no inherent capability to contain the
discharge of coatings and biofouling organisms removed during hull cleaning. Instead, these
particulate materials are commonly released into the water column.

       The potential for water quality impairment and ANS release resulting from the
uncontained discharge of underwater cleaning effluent is widely recognized. For example,
underwater hull cleaning has been banned according to the ANZECC Code of Practice
(ANZECC, 1997).

       Due to this scrutiny, a number of underwater cleaning technologies have been developed
to retain the abraded paint, rust, and biofouling  organisms.  At present, several of these systems
are becoming commercially available. Bohlander (2009) conducted a review of underwater hull
cleaning practices, and found four systems that  were designed to contain and capture cleaning
effluent and transfer this wastewater stream to the surface for treatment. These systems include:
1) the U.S. Navy Advanced Hull Cleaning System (AHCS) and Automated Hull Maintenance
Vehicle (AHMV), 2) the modified  SCAMP from Seaward Marine Services,  3) the HISMAR
system based in the United Kingdom,  and 4) the Norwegian CleanROV system.

       Two of these systems are currently being used for hull cleaning: the AHCS and the
CleanROV. Only one of these systems, the AHCS, includes a wastewater treatment system along
with the capability to process larger calcareous  fouling. The AHCS fulfilled most of the need for
contained hull cleaning, although it was developed specifically for the Naval Sea Systems
Command (NAVSEA) and is not available to commercial vessels  at this time.  The AHCS and
the CleanROV systems are discussed in the following sections.


       The U.S. Navy developed a prototype multi-brush hull cleaning system that captures the
debris generated from hull cleaning and transports it to the pier for processing in a mobile
treatment trailer. The AHCS was developed primarily to reduce the amount of copper discharged
during hull cleaning of U.S. Navy ships. It was  not specifically developed to process marine
biofouling, although biofouling is also contained and processed by the system.

       Floerl et al. (2010) also reported on the development of an Automated Hull Maintenance
Vehicle (AHMV), a specialized remotely operated vehicle  (ROV) technology developed for
automated underwater hull maintenance and inspection of U.S. Naval ships. The unit addresses
the expense and environmental  implications of traditional diver-operated cleaning equipment that
discharge potentially toxic effluent into the marine environment, along with biofouling debris
and potential ANS (Floerl et al., 2010). Biofouling is cleaned from the hull using rotating
brushes incorporated into the unit, and the debris is collected by a vacuum-sealed mantle that

Underwater Ship Husbandry Discharges              Section 5 - Vessel Husbandry Debris Containment Options
surrounds the AHMV. Particulate matter is transported to the surface for treatment (filtration to
remove particles > 20 microns (|im)  via filtration) and disposal.

       The AHCS and AHMV have the potential of saving the U.S. Navy 10 percent on fuel-
costs, and may result in lower environmental impact from the routine cleaning of navy vessels.
Floerl et al. (2010) were unable to obtain detailed information on test results of these units,
particularly on the AHMV's effectiveness at removing biofouling from targeted areas and at
collecting and containing biofouling and paint waste. Since no additional information could be
found, it is difficult to assess the availability of these technologies for hull husbandry of
commercial vessels.


       The Norwegian company Scat Harding developed the CleanHull AS, a ROV for
underwater hull cleaning with integrated water filtration and waste recovery. The CleanHull AS
is designed to clean large, flat surfaces with minimum curvature and biofouling assemblages at
early stages of development (e.g., algal growth and small barnacles). Preliminary (and
unpublished) test results indicate an effectiveness of close to 100 percent in removing biofouling
from such areas (Floerl et al., 2010). CleanHull AS cannot clean niche areas such as propellers,
rudders, thrusters or similar irregular structures. Biofouling is removed from hull surfaces using
an underwater high-pressure water blast. The power of the water-blast varies depending on the
type of AFC on the hull (e.g., silicone-based paints require gentler treatment).

       The removed biofouling material is captured via a particulate containment system that
includes a vacuum that pumps the recovered material into a filter unit. The company estimates
that approximately 98 percent of the biofouling material removed during  cleaning is captured
and contained during this process. However, supporting documentation was not supplied and no
information is available on the particle sizes that can be captured by the system (Floerl et al.,
2010). Apparently, extensive testing in collaboration with several major AFC manufacturers has
been undertaken. Results (which were also not available to Floerl et al.) indicate that the water-
blasting action of CleanROV has no negative effect on the performance of the AFCs, including
biocide-free silicon-based products. This is seen as its principal advantage over more abrasive
techniques such as rotating brushes.

       Scat Harding offers fleet service agreements involving multiple treatments per year. The
ROV is not intended for use on heavily fouled ships, as the principal objective of the system is to
preserve or reinstate the performance of a ship's AFC. The CleanHull AS services are currently
offered at ports in Norway; in the Skagerak Strait; Vlissingen and Rotterdam in the Netherlands;
Algeciras, Spain; Southampton, UK; United Arab Emirates; and Singapore (Scat Harding, 2009).

Underwater Ship Husbandry Discharges                                 Section 6 - Hull Husbandry Costs

                                                                        SECTION 6


       Although hull husbandry can facilitate the release of ANS and pollutants such as copper,
cleaning biofouling from the hulls and niches of commercial vessels reduces hydrodynamic drag
and the associated increase in fuel consumption. Floerl et al. (2010) developed cost estimates for
hull and niche cleaning of commercial vessels with lengths ranging from 25 to 200 meters. Costs
were estimated for both out-of-water (slipway and drydock) and underwater cleaning by
available technologies, based on quotes obtained from facilities and professional cleaning crews
in Australia and New Zealand. These cost estimates are presented in Table 3.

       The cost estimates in Table 3 have been converted from Australian to U.S. dollars and, as
noted by Floerl et al. (2010), are subject to large variations in rates charged by providers of these
services. The costs of services such as drydocking,  slipway hire, professional cleaning crews for
water-blasting and painting, charges for water usage, waste removal and treatment and other
associated activities vary greatly between facilities  and countries.  Furthermore, the cost estimates
do not include the lost revenue incurred while vessels are traveling to and from cleaning facilities
and the time out of service while waiting to be cleaned.

       As indicated by Table 3, the cost for removing a medium-sized ship (25-60 m in length)
from the water in a slipway and cleaning via water-blast is approximately $2,800-$12,000,
excluding lost operating revenue. The application of AFC following cleaning is estimated to cost
an additional $6,500-$24,500.

       The costs for dry docking and cleaning a 25-60 m vessel using high-pressure water-blast
(8,000 psi) at a New Zealand drydock ranges from $8,800-$28,800 depending on vessel size.
The application of additional AFC will add $34,900-$87,900 depending on vessel size.

       Cost estimates for advanced underwater hull cleaning technologies using rotating brushes
and water blast combined with a particulate containment system are also provided in Table 3.
The estimated cost of underwater removal of biofouling from all hull and  niche areas of a 50 m
long ship range from $10,300 to $26,300, plus one to two days of lost revenue. For vessels
ranging in size from 100 to 200 meters in length, these costs increase to as much as $96,000 plus
three to five days of lost revenue while the vessel is being cleaned.

Underwater Ship Husbandry Discharges
Section 6 - Hull Husbandry Costs
                    Table 3. Estimated Costs of One-Time Out-of-Water and Underwater Hull Husbandry
Slipway (out of water)
Drydock (New Zealand)
Drydock (Australia)
Hull Cleaning via
Water Blasting
Apply new AFC*
Hull Cleaning via
Water Blasting
Apply new AFC*
Hull Cleaning via
Water Blasting
Apply new AFC*
Hull Cleaning via
Rotating Brush and
Hull Cleaning via
ROV Water Blast
and Paniculate
Vessel Length (meters)






Source: Adapted from Floerl et al., 2010.
Note: * AFC application is a cost in addition to hull cleaning.

Underwater Ship Husbandry Discharges                                 Section 6 - Hull Husbandry Costs
       The cost of underwater cleaning of hull and niche areas using technologies that remove
biofouling organisms from a vessel hull (i.e. brushes and water-blast) is generally lower than the
cost for removing a vessel from the water for cleaning only. However, because of variation in the
rates different operators charge for the same service, the relative difference in cost between
underwater and shore-based water cleaning is also variable. Nevertheless, for commercial vessels
of 50-200 m in length, a comprehensive underwater hull cleaning is 35-65% less expensive than
biofouling removal at a slipway or drydock. This difference in cost may further increase when
indirect costs such as losses in revenue are incorporated. However, several factors offset the cost
savings of underwater cleaning relative to out-of-water cleaning. The effectiveness of underwater
cleaning operations is likely to be lower than that of cleaning activities out of the water.
Furthermore, all commercially-available underwater cleaning technologies are either unable to
treat niche areas (e.g., underwater jet systems) or are unable to capture and retain all of the
biofouling material removed during the treatment process (e.g. rotating brush systems).

Underwater Ship Husbandry Discharges                                        Section 7 - References

                                                                       SECTION 7


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