SUCTION DREDGING IN THE NATIONAL FORESTS
Submitted by Marcie Foley
Published in Gold and Treasure Hunter Magazine Sept.1997
Note from webmaster: The following is the text from a new brochure published by the USDA Forest Service,
was designed to help dredgers dredge responsibly. Please check to see if this is available from your local Forest
Service office. It is called "Program Aid 1600, dated September, 1997." These should be distributed throughout
local clubs. In the event that it is not available to you, you can print and copy this news release, and distribute
copies to see that the word is passed to as many dredgers as possible. Thank you.
SUCTION DREDGING IN THE NATIONAL FORESTS - Dredging Responsibly to Protect River
Ecosystems by United States Department of Agriculture - Forest Service in cooperation with:
Eastern Oregon Mining Association, Inc. (Baker City, Oregon), Eastern Oregon Miners and
Prospectors, Inc. (Baker City, Oregon), Idaho Gold Prospectors Association (Boise, Idaho), Miners
Alliance (Seiad Valley, California), Modern Gold Miners & Treasure Hunters Association (Happy
Camp, California), The New 49’ers Prospecting Organization (Happy Camp, California), Northwest
Mining Association (Spokane, Washington), Oregon Independent Miners (Veneta, Oregon), Public
Lands for the People, Inc. (Azusa, California), Public Lands Action Committee (Azusa, California),
Shasta Miners and Prospectors Association (Redding, California), Washington Prospectors Mining
Association (Seattle, Washington), Western Mining Council (Redding, California)
Welcome to Your National Forests!
For millennia the allure of gold has kindled the adventurous spirit of miners, and many have sought their
fortunes in its pursuit. In California alone, thousands of 49’ers arrived from all corners of the world after
James Marshall found gold in a Sierra stream. Few people know that the California gold rush infused
hundreds of millions of dollars in the national economy and fueled the eastern economic engines that settled
the West. Over the past two centuries, miners have extracted gold from mountains and streams throughout
the United States, changing the course of the Nation’s future.
Today there is a new-found interest in gold mining. For individuals or small groups of miners, only a few
methods of gold mining are economically feasible. One of these methods, a type of placer mining called
suction dredging, removes gold from where it has lodged in the beds of running creeks and streams. This
method is increasing in popularity in the national forests. This brochure is intended to increase readers’
understanding of suction dredging; it is not intended to replace existing laws and regulations.
Mining today differs from that of yesteryear: which sharing many of the traditions of their forebears,
today’s miners must be aware of how their activities affect the streams and surrounding ecosystems, and
of the need to understand and operate according to laws and regulations. These laws and regulations
ensure continued use of national forests and protect resources such as clean water and fish populations.
Indeed, all users of national forests must share in the stewardship as well as reap their benefits.
Please work with the US Department of Agriculture (USDA) Forest Service to make sure that suction
dredging is done in a manner consistent with current law and good natural resource management, in order
to maintain our forest resources for future generations. Enjoy using your national forests—and good luck in
your search for gold!
Though not as numerous as in the past, today’s independent prospectors and miners are still walking our
national forests, searching for the mother lode. They continue to be the on-the-ground eyes and ears of the
mining industry. Their exploration plays a large role in the development of the mineral industry.
National Forest System lands are experiencing an ever-increasing demand from a growing and increasingly
diverse population. There is demand for products, recreation, water, wildlife, and fish, and for an almost
endless list of intangible, but desirable, goals.
It is the policy of the Federal Government to foster and encourage the orderly exploration and development
of minerals to help assure our Nation’s industrial, economic, and environmental needs. At the same time,
the multiple-use doctrine recognizes the need to maintain our national forests for current and long-term
benefits to people, while a host of other laws and regulations require that these multiple uses do not disrupt
the natural ecosystem. It is every citizen’s responsibility to help forge a way for these values and
objectives to co-exist.
The challenge for today’s gold dredger is to demonstrate a model of compatibility with other forest users,
and sensitivity to the environment we all share. Like all users of the national forests, gold dredgers must
practice responsibility and stewardship for our lands and streams.
Suction dredgers must recognize that the laws and regulations governing their activity vary from place to
place. Please refer to the back pocket of this brochure for local information.
Most gold originates in hard rock deposits, often within quartz veins. Through weathering, such as cycles of
freezing and thawing, and erosion, such as that caused by flowing water, gold is separated from the rock.
The gold flakes and nuggets released are transported downslope by gravity and running water, and are
eventually deposited in streams.
Since gold is denser than the other streambed sediments, it tends to move downward to the contact
between the gravels and the underlying bedrock, collecting at the bedrock surface and in the overlying few
feet of gravels. During floods, when rushing waters transport gravels rapidly downstream, the gold moves
more slowly, often lodging in cracks, crevices, and small holes in the bedrock surface.
Gold settles out where flowing water decreases in velocity—for example, at places where the stream
gradient decreases, downstream of large boulders, or where the bed deepens into pools.
Suction dredges are used within streams and rivers to remove the gravels overlying bedrock and to access
gold. The gravels are deposited into a sluice box, a long container divided into sections by a series of slats
called riffles. As water runs through the sluice box, heavy particles, including gold, are concentrated behind
the riffles, and “cleaned” gravels exit from the final compartment to form tailings.
Dredges use high-pressure water pumps driven by gasoline-powered engines. The pump creates suction in
a flexible intake pipe 2 to 12 inches in diameter. Suction dredges vacuum the streambed (which is
composed of rock, gravel, and finer sediment) with water through the hose into the sluice box. Both the
pump and the sluice box are usually mounted on a floating platform. Dredges are often positioned over the
work area by securing the dredge to trees or rocks with ropes or cables.
Suction dredgers often use hookah (air supply) gear in order to dredge well below the surface of the water.
The portion of stream bottom dredged ranges from a few small excavations to the entire wetted area in a
section of the stream. Larger suction dredges have the capacity to excavate as much as several cubic
yards of gravel from the river bottom, depending on the type of streambed material and the skill of the
SUCTION DREDGING AND FISH
The health of fisheries is significant for several reasons. First, fisheries are a major source of food and
income, contributing hundreds of millions of dollars to coastal economies, and constituting an essential
source of income for many communities. For many Pacific Coast Native American tribes, salmon are an
integral part of their culture. Recovery and protection of fisheries is an important goal for ecosystem
managers on both the Atlantic and Pacific coasts.
Second, each fish species, and in many cases each population or stock of a species, has been honed by
nature for survival within a specific environment. Genetic differentiation among fish species may allow us
to produce unique compounds that could prove useful in the future, for example, in industry or medicine.
Of special concern to forestry managers are endangered and threatened species, and fish caught either
commercially or for recreation. Many species of salmonid fishes fall into both of these categories.
Salmonid fishes, for example, salmon, trout, and char, are considered one of nature’s most intriguing
mysteries. Many of them, including most species of salmon, and some populations or stocks of steelhead,
migrate form the stream where they hatched—their natal stream—to the ocean, where they spend as
much as 80 percent of their life. Then, after years spent swimming in the ocean, these salmonids are able
to find their way back to their natal waters to spawn. How they navigate their return to these exact
locations is still incompletely understood.
The term used to describe this type of migration is “anadromous” (uh na’ druh mus), derived from the
Greek for “up running.” On the Pacific Coast, anadromous salmonids occur from southern California north
to Alaska and the Arctic Ocean; on the Atlantic Coast, from Connecticut to northern Newfoundland.
Most salmonids begin migrating upstream between April and October. Since spawning may not occur until
fall, fish arriving in spring and summer stay in the river, staying cool in deep holes in the river bed, and
often taking cover under large woody debris and overhanging rocks.
Spawning usually occurs where sediment-free, coarse gravels are within a few feet of the water surface,
often on shallow gravel bars. Female salmon deposit eggs in a nest called a “redd,” which is an area in the
gravel she loosens up. The velocity of the water running over a redd must be high enough to oxygenate the
Redd size varies with the species of salmonid, but can be as large as 28 inches deep and 6 feet across for
During spawning season, it is often visible as a lighter round or oval depression in the gravels. However,
later on, while the eggs are still developing, or the youngest stages of the fish are present in the redd, the
topmost gravels in the redd may wash away. This can make it difficult, if not impossible to distinguish the
redd from its surroundings.
The rate at which the eggs develop depends on the water temperature, but, generally, fry hatch from the
eggs after 50-70 days. Each tiny fish is attached to the yolk sac from its egg. Over the net 35-45 days, the
fry move through the gravel toward the surface, absorbing the yolk in route. Disturbance of a redd can kill
developing eggs and fry.
When the fry reach the surface, they are free-swimming, and are termed “alevins.” The length of time
smolt remain in their natal river before entering the ocean depends on the species, and even the particular
population. Populations that spend a longer period of time in streams and rivers are more sensitive to
changes in the river. As anadromous salmonids swim downstream, they feed and grow on their way to the
ocean They will live in the ocean for a number of months or years, the time period depending on the
species, population, and environmental conditions, before returning to their natal river or stream to spawn.
Until recently, raising fish in hatcheries and barging them around barriers such as dams was the major
strategy for reversing fisheries depletion. However, continued decline has focused fisheries management
on a new approach, that of ecosystem and habitat restoration and protection. Managers are opting to
minimize and repair disturbance of natural systems wherever possible.
For suction dredgers, this means that many streams and rivers are closed to dredging during the period that
salmonids spawn, the eggs mature and hatch, and the fry move up through the gravels. Because of the
wide variation between streams and between fish stocks (a population that reproduces independently from
other populations), closures are determined on a local basis. Respecting these closures is the first step
suction dredgers can take to help protect the fish.
SUCTION DREDGING CHECKLIST
The following Suction Dredging Checklist outlines precautions dredgers should take to help maintain
healthy salmonid populations when streams are open for mining. One of the most important precautions is
depositing loosened gravels in a manner so that salmonids will not use them for spawning, as these gravels
may wash out before the fry are fully developed.
Following laws and regulations related to suction dredging helps to protect river ecosystems. These statutes
have been designed to preserve rivers and protect fish populations—for example, to prohibit dredging
during the time that eggs and fry are present in the gravels. Since there is so much variation between
rivers, many of the regulations, such as closures, must be determined on an individuals basis. Rivers
containing endangered species of fish or other aquatic animals may be closed year-round.
This section gives pointers for reducing the impacts of suction dredging on rivers and the plants and
animals they contain. The checklist begins the same way suctions dredging does: obtaining needed permits
and transporting dredges and other equipment. Also covered are various activities associated with dredging
including camping, securing dredges, and using gasoline engines, as well as dredging itself. The checklist
was developed with the assistance of miners, scientists, and forest managers. It does not replace existing
laws and regulations.
Follow the law and create good will through mutual respect.
Identify where and when mining is allowed or prohibited.
Obtain needed permits.
Checks with the local USDA Forest Service District Ranger for guidance on which laws
and regulations apply to the specific lands. Recognize that different laws apply to different
lands. Recognize that different laws apply to different lands. For example, depending on
the land status, the Acquired Lands Leasing Acts or the 1872 Mining Law may apply.
Review USDA Forest Service Surface Use Regulations for locatable minerals.
Review other rules and regulations that may cover, but are not limited to, the following:
annual and seasonal stream closures, nozzle and hose diameters, engine horsepower and
noise levels, winch use, operations in spawning areas, hydraulicking and bank mining,
stream flow disturbance, damming, volume of material, restoration, woody debris, spill,
and sanitary waste.
If applicable, file a notice of intention (NOI) to operate with the District Ranger.
If required, submit a proposed plan of operation to the District Ranger.
Obtain permits and file notices and plans of operation with other Federal and State
agencies as required.
Camping Near Rivers and Streams - Treading Lightly
The land bordering rivers and streams, known as the riparian area, is vitally important to many species of
wildlife. If possible, camp outside of the riparian area.
Minimize camping impacts, such as trails and clearings.
Avoid trampling vegetation.
Do not use soaps or detergents in or near river or riparian areas.
Dispose of garbage and human waste in a sanitary, self-contained way and remove it to an
approved disposal site.
Keep the campsite clean to avoid pollution and maintain a natural experience for other
Transporting And Storing Equipment - Heavy-Duty Protection
Overhanging banks keep the edges of streams cool and are used for cover by fish. when portions of the
streambank are damaged, erosion occurs and soil washes into the stream, silting in gravel beds and causing
increased turbidity in the stream. The ribbon of land adjacent to streams, often a border of thick,
multilayered vegetation, hosts numerous wildlife habitat.
Minimize impacts of bringing in and storing equipment.
Avoid Streambank damage.
Avoid driving off-road through riparian areas.
Securing Dredges With Lines - Line Up For Safety
Lines securing dredges can be a safety hazard for rafters and boaters if the lines block passage. Another
concern is injury to trees where equipment has been tied.
Make sure cables and ropes don’t block passage for boats and rafts; lines spanning the
river should be at least 6 feet above the water surface.
Flag lines to make them easy to see. When anchoring a cable to a tree, protect the tree by
wrapping it with an old inner tube, or by covering the cable with a piece of old hose.
Make sure trees along the cable are not damaged.
Remove all cables, ropes, and inner tubes when dredging is completed.
Using Gasoline Engines - Fuel For Concern
Other stream users often express concerns about the gasoline engines on dredges, complaining, for
example, about noise and fumes. An additional problem can be leakage of petroleum products from engines
or storage containers.
Install a muffler on engine to minimize noise.
Prevent fuel and oil leaks into water or riparian areas, from the engine as well as from
Outfit the suction dredge with an oil pan.
To prevent gasoline from entering the water, place a polypropylene pad around the has
tank when refueling. The pad absorbs petroleum products but repels water.
In case of a leak, do not disperse oil or fuel with detergent. This makes spills harder to
clean up and increases the damage to aquatic wildlife.
Leaving Boulders and Large Woody Debris - Best Left Alone
Large boulders and woody debris are important elements in the creation of fish habitat because large pools
form adjacent to them. During periods of hot weather, the cooler deep sections of the pools are essential
for fish survival. Fish use large woody debris for cover.
Do not remove large boulders and large woody debris from the stream.
Preserving Overhanging Banks - Watch Out Above
Destabilization of overhanging banks by undercutting often causes banks to collapse into
the streams. This increases sediment in the water and decreases habitat for fish, which
often seek cover under banks.
Do not undermine overhanging banks with the suction dredge.
Do not remove protruding boulders or woody debris from banks.
Make sure gravel piles do not deflect high water against banks.
Placing Cobble and Tailing Piles Effectively Helps Protect and Preserve Salmon Spawning
Grounds - Tell “Tail” Signs - Redd Means STOP
When salmonids spawn, eggs hatch, and the fry move up through the gravels, streams and river are
generally closed to suction dredging. This protects eggs and fry from being sucked through dredges or
suffocated by tailings or sediment.
While seasonal closures protect eggs and fry from direct impacts, they may not alleviate a potential
problem that occurs if salmonids spawn in gravels left by dredgers. If these gravels are loose, and wash
downriver during high waters, any redds contained within these gravels may be destroyed.
Cobble and tailing piles can obstruct passage for boaters and rafters. Another problem can be cobbles and
tailings left on or near the bank. During dry periods, when the water level drops, the piles become exposed.
Unlikely to be flushed away by high waters, these piles can remain for many years, particularly during
periods of drought.
Don’t stack cobbles or deposit tailings on or near the bank.
Distribute cobbles as broadly as possible in the channel.
Periodically stop operations and pivot the back of the dredge to help spread tailings.
Deposit tailings further from the dredge by extending the end of the sluice.
Follow regulations concerning where and when suction dredging is permitted.
Piles can be flattened using hydraulic force.
Controlling Silt discharge Into Water - Get a Clear Idea
Depending upon site-specific conditions, silt can settle on and suffocate redds when
dredging coincides with spawning or movement of fry through the gravels. This is one of
the reasons dredging is seldom allowed during that time period. Large amounts of silt and
fine sand can have a big impact, especially in small streams, which have less capacity for
Look behind you. Evaluate your impacts and consider reasonable ways to minimize them.
Do not dredge streambanks.
Toxic Materials And Rubbish in Streams - Take-Out Menu
Suction dredgers can help restore streams by removing natural and introduced lead and mercury from the
streambeds. Within a streambed, lead weights and shot are ground by the constantly moving sand, which
removes small flakes of lead. The flakes oxidize easily, which releases the lead into the environment.
Lead recovered by suction dredging can be recycled. In many cases, local mining
organizations can act as central collection points.
Sometimes mercury is encountered on stream bottoms. Even in modest amounts,
mercury can be quite toxic. Contact your local Forest Service office and appropriate State
agency for information about proper disposal of materials you find in streams.
Dispose of removed material safely and according to the law.
Be careful when dredging in areas where sediments are likely to contain toxic substances,
such as near discharge areas from towns and industrial sites.
Discard refuse in an approved disposal area.
Marcie Foley is the former managing editor of
Gold and Treasure Hunter Magazine
as well as the co-owner and general manager
of Pro Mack Mining Supplies.