SECTION 2: Sources of Pollution

2-1

SECTION 2: SOURCES OF WATER POLLUTION FROM MARINAS

AND RECREATIONAL BOATING

Marinas are not reported by states, territories, or

tribes to be a major source of nonpoint pollutants

that contribute to poor water quality, as are

sources such as agriculture and urban areas,

though the location of marinas at the water’s edge

can lead to their being affected by other pollutant

sources. Pollutants from upstream point and

nonpoint sources in a watershed might flow to a

marina’s waters, adding to any nonpoint pollutants

released at the marina itself. Water quality in a

marina, therefore, is often a reflection of not only

nonpoint source pollutants generated at the marina

but also a cumulative load of pollutants from

several watershed sources. Awareness of the

potential for the generation of nonpoint source

pollution at a marina and of how to use

management measures and site-specific BMPs to

reduce nonpoint source pollution is important to

ensuring the best possible water quality in a

marina basin. This section of the guidance

describes the pollutants that can be generated at a

marina and their potential effects on water quality

and aquatic life.

The construction of a marina can create a

condition of reduced water circulation. Installing

structures such as bulkheads and jetties, which

are necessary to ensure the safety of vessels,

docks, and shoreside structures, can cause water

circulation in the basin to be below what it was

before the marina’s construction. In an area

already protected from wave action, such as a

cove or inlet, marinas can potentially introduce

pollutants to an area with limited natural circulation or water exchange. Over time, reduced

circulation and increased pollutant generation can

increase pollutant concentrations in the water

column, sediments, and aquatic organisms.

The pollutants that might be generated at a marina

and enter a marina basin include nutrients and

pathogens (from pet waste and overboard sewage

discharge), sediments (from parking lot runoff and

Section 2 Contents

Pollutant Types and Impacts.............................................................................................. 2-2

Pollutants in the Water Column ......................................................................................... 2-3

Low Dissolved Oxygen.................................................................................................. 2-3

Metals ............................................................................................................................... 2-3

Petroleum Hydrocarbons .............................................................................................. 2-4

Solvents ........................................................................................................................... 2-4

Antifreeze ........................................................................................................................ 2-4

Acids ................................................................................................................................. 2-4

Surfactants ...................................................................................................................... 2-4

Pollutants in Aquatic Organisms ..................................................................................... 2-4

Pollutants in Sediments ..................................................................................................... 2-5

Metals ............................................................................................................................... 2-5

Petroleum Hydrocarbons .............................................................................................. 2-5

Pathogens ............................................................................................................................ 2-5

Debris and Litter ................................................................................................................. 2-6

Sediment and Habitat Alterations ..................................................................................... 2-6

Shoaling and Shoreline Alterations.................................................................................. 2-7
2-2

National Management Measures Guidance

shoreline erosion), fish waste (from dockside fish

cleaning), petroleum hydrocarbons (from fuel and

oil drippings and spills and from solvents), toxic

metals (from antifoulants and hull and boat

maintenance debris), and liquid and solid wastes

(from engine and hull maintenance and general

marina activities). The effects of these pollutants

on waterways and aquatic plants and animals are

discussed in this section. Marina construction and

reconstruction, in-water modifications at marinas,

and propeller wash and boat wakes can also

disturb aquatic habitats, plants, and animals.

Although nonpoint source pollution is a serious

problem nationally, more is always being learned

about effective ways to prevent and reduce it.

The purpose of this section is to describe the

general causes of nonpoint source pollution,

the specific pollutants and problems of concern,

and the general approaches to reducing the

impact of pollutants and other problems on aquatic

resources as these relate to marinas and recreational boating. Figure 2-1 illustrates the general

types of problems that various pollutants can

cause in aquatic systems.

Pollutant Types and Impacts

Marina construction can alter habitats at a site.

Shoreline vegetation may be reduced at some

locations. Bottom sediments may be stirred up

more frequently with boating activity and dredging

to maintain channel and basin depth. These kinds

of alterations can have both negative and positive

effects. For example, installation of marina pilings

and bulkheads introduces a hard-surfaced habitat

into a marina that previously might have been

dominated by a soft-bottomed habitat of mud and

silt. Organisms that prefer rocks and other hard

surfaces (fouling organisms) will colonize this new

habitat and in turn may attract other invertebrates

and juvenile fish to the area.

The fact that a marina is present does not mean

that water quality is poor. Many marinas have

good to excellent water quality. Despite this, their

aquatic habitats might not be healthy enough to

support a natural diversity of aquatic organisms,

and they might still have sediments contaminated

by pollutants from storm water runoff or by antifoulants that have leached from ship hulls or piers.

Figure 2-1. Effects of pollutants in aquatic systems.
SECTION 2: Sources of Pollution

2-3

Pollutants in the Water Column

Pollutants from marinas can cause pollution

problems in the water column. These problems

usually take the form of decreased levels of

dissolved oxygen and increased levels of metals

and petroleum hydrocarbons. Pollutants that

cause these problems get into the water through

storm water runoff, discharges from boats, and

spills of fuel or bilge water.

Low Dissolved Oxygen

The organic matter in materials such as sewage

discharged from recreational boats, trash tossed

into surface waters or on the ground, pet waste

carried to waterbodies in storm water runoff, and

fish waste disposed of into surface waters

consumes dissolved oxygen as it decomposes.

The amount of dissolved oxygen required to

decompose sewage and other organic matter is

measured as the “biological oxygen demand”

(BOD) of a waterbody. Consumption of oxygen

by decomposing organic matter leaves less

oxygen for fish, crabs, clams, and other aquatic

organisms. Very low levels of dissolved oxygen

can result when water temperatures are high

(because hotter water holds less oxygen), which

is often the case during the peak summer boating

season. Decreases in dissolved oxygen in several

northwestern marinas have been noted in the late

summer and early fall, the peak times of marina

use. An intensive study in several North Carolina

marinas showed large differences in dissolved

oxygen concentrations in the marinas compared to

the concentrations in the adjacent waterbodies,

with concentrations in the marinas being much

lower.1 These low concentrations of dissolved

oxygen were thought to be due to high biological

oxygen demand in the marina basins (due to

unknown causes) and poor flushing.

Metals

Metals and metal-containing compounds have

many functions in boat operation, maintenance,

and repair. Arsenic is used in paint pigments,

pesticides, and wood preservatives. Zinc anodes

are used to deter corrosion of metal hulls and

engine parts, and zinc is often a constituent of

motor oil and tires. Copper is used as a biocide in

antifoulant paints. Chromated copper arsenate

(CCA) is used in wood as a preservative. Mercury is contained in many float switches for bilge

pumps and shower water storage tank pumps and

in air conditioning/heating thermostats. These

switches can contain as much mercury as 100

fluorescent lamps. Nickel is a component of brake

linings and pavement material, and cadmium is

present in batteries and brake linings. These and

other metals (aluminum, iron, and chromium) are

used in various components used at marinas or by

recreational boaters and can wash from parking

lots, service roads, and launch ramps into surface

waters with rainfall. High levels of zinc, chromium, and lead have been detected in the waters

of some marinas.

Many of the antifoulants used for barnacle control

in marine waters are used in fresh waters as well.

Copper is the most common metal found at toxic

concentrations in marina waters.2 Dissolved

copper has been detected at toxic concentrations

at several marinas within the Chesapeake Bay. 3

Copper is leached to surface waters and sediments from bottom paints and scrapings. Tin in

the form of butyltin, an extremely potent and nonspecific biocide, has been detected at toxic levels

in marina waters nationwide.4 The use of butyltins

in bottom paint is now restricted to paints with

release rates of 4.0 micrograms per square

centimeter or less and on vessels larger than 25

meters (82 feet) in length and on aluminum-hulled

vessels regardless of size. Although butyltins are

no longer used on most boats, the years of their

use in antifoulants has left areas of low to high

concentrations of these compounds in sediments.

Disturbance of the sediments can reintroduce the

toxic compounds into the water column, where

they can be ingested by fish or other aquatic

organisms and in turn by people.

1 NCDEM, 1990. 2 NCDEM, 1990, 1991; METRO, 1992.

3 Hall et al., 1987.

4 Grovhoug et al., 1986; Maguire, 1986; Stephenson et

al., 1986; Stallard et al., 1987.
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National Management Measures Guidance

Petroleum Hydrocarbons

Sources of hydrocarbons at a marina include

fueling stations; operation, maintenance, and

repair of boat engines; and storm water runoff

from the marina property and off-site upland

areas. Petroleum hydrocarbons are contained in

fuel, oil, grease, lubricants, finishes, and cleansers.

Petroleum can be spilled directly into surface

waters when fuel drips from fueling nozzles or a

fuel tank is overfilled at a dock. Older 2-stroke

marine engines discharge unburnt fuel and oil

directly to the atmosphere and surface waters

while they are operating. Oil, fuel, paint, antifreeze, or other liquids dripped from engines or

paint brushes or spilled while draining oil or fuel

from engines enter surface waters indirectly with

storm water runoff or in flows of ground water

after the substances have seeped into the ground.

Rainwater washes anything dripped, spilled,

deposited, or disposed of from building roofs,

parking areas, boat ramps, and maintenance areas

on the marina property and nearby properties to

the nearest downstream surface water, which is

often the marina basin.

Solvents

Solvents like methylene chloride, tetrachloroethane, trichloroethene, and trichlorethylene are

contained in degreasing agents, varnishes, paint

removers, and lacquers. They are used at marinas

for engine maintenance and repair activities and

vessel painting and cleaning. If not properly

contained, solvents can potentially enter marina

waters through surface water runoff or through

ground water transport from hull maintenance

areas. Solvents are stable compounds that are

insoluble in water, which makes them very mobile

in ground water. They are usually heavy, longchain organic compounds, so they sink to an

impermeable bottom layer in the ground (like

bedrock) and accumulate. Many solvents are

known cancer-causing compounds (carcinogens).

Antifreeze

Antifreeze is used at marinas in dry storage of

boats and engine maintenance. It contains either

ethylene glycol or propylene glycol. Propylene

glycol antifreeze is reported to be much less toxic

to aquatic organisms than ethylene glycol and is

therefore preferred for use in boats. Both types of

antifreeze, however, are considered toxic and

should be poured, stored, and drained carefully to

avoid spillage. Used antifreeze should be taken to

a hazardous waste collection center and recycled

if possible.

Acids

Batteries contain battery acid, which is very

corrosive and toxic and often contains high levels

of toxic metals like lead. Cleaning compounds and

detergents often contain strong acids or lye.

These materials can be washed into the marina

basin with the next rain along with the petroleum

hydrocarbons, solvents, paint chips, and other

material spilled on the ground. Many hazardous

waste collection stations accept used batteries.

Surfactants

Surfactants are compounds used in detergents

and other cleaning agents to reduce surface

tension. Some are known to be very deadly to

aquatic organisms. Surfactants can also accumulate at the water surface and create a barrier

against the transfer of dissolved oxygen across

the air-water interface, resulting in lowered

dissolved oxygen concentrations in the water. For

these reasons, surfactants are best not used on

boats that are in the water or on upland areas

where runoff washes into surface waters.

Pollutants in Aquatic Organisms

Many aquatic organisms feed by sifting through

sediments or eating organisms that filter food

particles out of the water. The aquatic organisms

thus ingest any pollutants attached to or mixed in

with the sediments or suspended particles. The

pollutants they ingest accumulate in their tissues

rather than being excreted. When many smaller

organisms, each of which has accumulated some

pollutants in its tissues, are eaten by an organism

higher in the food chain (for instance, a fish), that

organism then accumulates in its tissues all of the

pollutants accumulated by the lower organisms.

This process, called bioaccumulation, is the reason

that very small quantities of pollutants in the water

column can result in dangerous concentrations of

pollutants in fish, oysters, and other aquatic
SECTION 2: Sources of Pollution

2-5

organisms. Numerous studies conducted from the

late 1970s through early 1990s have demonstrated

this effect and, in particular, the effect on marinas

when proper pollution prevention is not practiced.5 Copper and zinc have been found at higher

concentrations in oysters from marinas than in

oysters from sites outside marinas; higher-thannormal concentrations of copper, cadmium,

chromium, lead, tin, zinc, and PCBs have been

found in mussels from marina waters; after 3

months, concentrations of lead, zinc, and copper

were two to three times higher in oysters transplanted to marinas than in oysters left outside

marinas; and concentrations of copper in green

algae and fouling organisms (barnacles, etc.)

were much higher in a marina area than in

adjacent areas.

Pollutants in Sediments

Many contaminants generated from boat maintenance and general marina use (e.g., oil and grease

drippings from cars) do not dissolve well in water

and accumulate to higher concentrations in

sediments than in the overlying water. Contaminated sediments may, in turn, act as a source from

which these contaminants can be released into

overlying waters. Benthic organisms—those

organisms that live on the bottom or in the

sediment—are exposed to pollutants that accumulate in sediments. Pollutants ingested by these

organisms become increasingly concentrated in

animal tissue as the pollutants are passed up the

food chain, and thus can reach levels dangerous

for human consumption. Many fish advisories are

issued for this reason.

Metals

Copper is the major contaminant of concern in

sediments because many common antifouling

paint preparations contain cuprous oxide as the

active biocide component.6 In most cases metals

tend to sink and accumulate in sediments and not

stay in the water column, though they do attach to

small suspended particles and can be distributed in

the water column with these particles. When

attached to suspended particles, metals are often

associated with small particles, so they settle out

of the water column slowly and are mixed upward

easily. In marinas, higher levels of some metals

(such as copper and lead) have been found near

maintenance area drains and fuel docks than at

other locations, suggesting that maintenance areas

and fueling stations are sources of metals to the

water and good targets for pollution prevention

practices.7

Petroleum Hydrocarbons

Petroleum hydrocarbons, particularly polynuclear

aromatic hydrocarbons (PAHs), tend to attach to

suspended particles and sediments. Because

they can stay in sediments for years, they can be

ingested by mussels, oysters, or other bottomdwelling organisms long after they are spilled or

washed into the water. Studies have found high

concentrations of petroleum hydrocarbons in

marinas, though the studies have also found that

concentrations of these compounds are much

lower in the sediments of well-flushed marinas.8

Such findings support the supposition that

sufficient flushing in a marina basin is important

to prevent a buildup of pollutants in marina

sediments.

Pathogens

Studies that have attempted to determine whether

there is a correlation between boating density and

pathogen (fecal coliform) concentrations in lakes

and reservoirs are divided in their conclusions.

Pathogens are added to surface waters by

wildlife, dogs and cats, seeping septic tanks, and

combined sewer outfall overflows, and these

sources could have a larger impact than boaters

on pathogen concentrations. Some violations of

health standards for fecal coliform bacteria (the

bacteria found in human and animal wastes) have

been related to periods of high-intensity recreational use, such as holiday weekends. These

violations could be due to either boater discharges

5 CARWQCB, 1989; Marcus and Stokes, 1985;

McMahon, 1989; NCDEM, 1991; Nixon et al., 1973;

SCDHEC, 1987; Wendt et al., 1973; SCDHEC, 1987;

Wendt et al., 1990; Young et al., 1979.

6 METRO, 1992.

7 McMahon, 1989; NCDEM, 1991; Soule et al., 1991.

8 Marcus et al., 1988; McMahon, 1989; NCDEM, 1990;

Voudrias and Smith, 1986.
2-6

National Management Measures Guidance

or sediments where pathogens are concentrated

being stirred up, or both.

Studies conducted in Puget Sound, Long Island

Sound, Narragansett Bay, North Carolina, and

Chesapeake Bay have shown that boats can be a

source of fecal coliform bacteria in areas with

high boat densities and poor flushing.9 Human

health problems can result, especially if nearby

waters are used for swimming, surfing, wind

surfing, water skiing, or other recreational activities that involve significant water contact.

Bacterial and viral contamination of waters can

result from improper use of marine sanitation

devices (MSDs). If a vessel has an installed toilet,

the law requires that it be equipped with an MSD.

Incorrect configuration of the toilet and MSD can

lead to direct discharge of waste to surface

waters. Discharge of the contents of portable

toilets to surface waters also results in contamination. Boats with portable toilets are not required to

have MSDs, and their contents should be disposed

of at a sanitation facility.

Currently a number of states have designated all

or nearly all of their surface waters as no discharge zones (NDZs). These states include

Michigan, Missouri, New Hampshire, New

Mexico, Rhode Island, and Wisconsin. Boats on

fresh waters in New Hampshire, Missouri, and

New Mexico must be configured such that

wastes cannot be discharged directly into the

water (i.e., Y-valves must be disabled), and boats

may be inspected to see that this requirement is

met. In addition, other states have segments of

their surface waters designated as NDZs. These

states include California, Florida, Georgia, Massachusetts, Minnesota, New Jersey, Nevada, New

York, South Carolina, Texas, and Vermont. NDZs

are approximately evenly divided (in number of

areas designated) between fresh waters and

marine or estuarine waters. A no-discharge policy

is also in effect on all Army Corps of Engineers

reservoirs.

Debris and Litter

The numerous activities that occur at marinas—

vessel and engine repair and maintenance,

recreation on and off boats, fueling, dock maintenance, and building and grounds maintenance—

are sources of a variety of debris and litter. Paper

towels and cups, plastic bags, plastic and glass

bottles, fish netting, fishing line, discarded oil

filters and engine parts, discarded rags, debris

from sanding or pressure washing, pet droppings,

aluminum cans, and other forms of trash all find

their way into surface waters if not disposed of

properly. Coastal cleanups result in the collection

of millions of pounds of trash and debris from

U.S. coasts annually. The most common items

found along the nation’s coasts are cigarette butts,

plastic pieces, foamed plastic pieces, plastic food

bags/wrappers, plastic caps/lids, paper pieces,

glass pieces, plastic straws, metal beverage cans,

glass beverage bottles, plastic beverage bottles,

and foamed plastic cups. These wastes are

dangers to marine animals, which can die from

becoming entangled in items like fishing nets and

lines and from ingesting small pieces of debris that

are mistaken for food. The trash and debris are

dangerous to people visiting the coasts, who might

accidentally step on discarded items, injure

themselves, and risk infection. They are also

unnatural, unsightly additions to the coastal

landscape.

Sediment and Habitat Alterations

Dredging can disturb aquatic habitats; resuspend

bottom sediments (and recirculate toxic metals,

hydrocarbons, pathogens, and nutrients that are

found in sediments into the water column); and

increase turbidity, which reduces sunlight available

to algae and aquatic vegetation. Increased

turbidity lowers the rate of photosynthesis and

decreases the rate at which dissolved oxygen is

added to the water. Because dredging usually

occurs over a short time period and then ceases,

impacts that result from it, such as turbidity and

dissolved oxygen reductions, are usually temporary and do not have long-term negative effects.

Other consequences of dredging, such as habitat

disruption and deterioration, can have lasting

impacts.

9 Fisher et al., 1987; Gaines and Solow, 1990; Milliken

and Lee, 1990; NCDEM, 1990; Sawyer and Golding,

1990; Seabloom et al., 1989.
SECTION 2: Sources of Pollution

2-7

Boat operation can cause these same problems in

the water column and for aquatic organisms by

disrupting shallow habitats and communities and

mixing nearshore sediments into the water

column.10 Propeller-driven boats operated too fast

near the shoreline can cause bank erosion.11

Shallow waterways can be affected by propellers

cutting off or uprooting aquatic plants from the

bottom and propwash mixing sediments into the

water.12 The latter not only reduces photosynthesis, but also can interfere with fish and other

sight-feeding animals, clog fish gills, and smother

plants and animals.

The effect that boat traffic and motor operation

can have on water quality and biological communities in lakes, reservoirs, rivers, and estuaries

varies and depends on the characteristics of the

waterbody and the type of watercraft being

operated on it.13 The effects are most acute in

soft-bottomed lakes and reservoirs, quiet side

channels of rivers and streams where fine

sediment accumulates because of the lack of

strong currents, and waterbodies that have

sediments rich in nitrogen and phosphorus.

The impact of boats on rooted plants depends on

the depth of the plants below the surface. Where

submerged aquatic vegetation (SAV) occurs in

shallow areas, boats passing through the area can

create troughs where the vegetation is eliminated

or severely reduced. Most direct effects of

motorboats on submerged aquatic vegetation take

place in water less than 5 feet deep, and motorboats can effectively remove all rooted vegetation

in water less than 3 feet deep, especially in areas

with sandy sediments. Recovery of submerged

aquatic vegetation beds can take years, and loss

of vegetation can lead to increased erosion and

invasion by other species. Submerged aquatic

vegetation protects shorelines from erosion and is

an important resource for many aquatic organisms

because it provides food and shelter.

Larval and juvenile fish can be killed directly by

boat propellers and propeller wash. Spawning or

nesting fish can be disturbed, and propeller wash

can be powerful enough to destroy fish eggs. Fish

populations can be lowered if survival of youngof-the-year fish is diminished and reproductive

success is lowered. Manatees and other aquatic

animals that swim near the water surface also

suffer from propeller strikes. Many manatees in

Florida bear the scars of propeller cuts.

Shoaling and Shoreline Alterations

Shoaling and shoreline erosion result from the

physical transport of sediment caused by waves

and currents. These waves and currents can be

natural (wind-induced, rainfall runoff, etc.) or

human-induced by boat wakes or in-water

structures that change currents or reflect waves.

When waves caused by passing vessels or

reflected from breakwaters reach the shallow

margins of a waterway, they can erode banks and

nearby bottom sediments. This effect tends to

wash away plants loosely rooted in sediments

near the shore and the associated animal life. A

substantial volume of the sediment that causes

shoaling is eroded from banks, and removing this

material by dredging is a costly recurrent

expense. Frequent dredging can be necessary

where boat traffic causes extensive bank erosion.

No wake zones and travel lanes located away

from shorelines can reduce and help prevent bank

erosion and shoaling. There is a direct relationship

between factors such as the distance of a boat

from shore, boat speed, slopes of the sides of a

bank, type of sediment, and depth of the waterway and the amount of erosion and subsequent

shoaling that results. The location of travel lanes

should be determined for each specific case with

these factors in mind.

The amount of shoreline erosion caused by boat

wakes in lakes and reservoirs depends on the

same factors as in coastal environments—design

features of the boat (size, hull shape, and draft),

distance of the boat from the shoreline, water

depth, channel width (if the boat is passing

through a channel), shoreline soil condition, slope

of the shoreline bank, and amount of shoreline

vegetative cover. In contrast to coastal environments, in lakes and reservoirs vegetation often

grows up to the shoreline, currents are minimal,

and there are no tides. Therefore, although boat

10 Chmura and Ross, 1978.

11 British Waterways Board, 1983.

12 USEPA, 1974.

13 USFWS, 1982.
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National Management Measures Guidance

wakes may be a primary source of erosive energy

in lakes with a large amount of boating activity,

vegetated shorelines reduce the potential for

erosion in lakes. Boat wakes are most likely to

cause lake shoreline erosion where the shoreline

has been altered and not stabilized and is therefore already susceptible to erosion.