Most suction dredges are motorized mining equipment, so they need more permission than a gold pan or a hand sluice. In California it is banned: the state Department of Fish and Wildlife (CDFW) says suction dredging “is currently prohibited and unlawful throughout California.” Elsewhere, small dredges are allowed in some waters under a state permit, a size limit and a fish season, plus whatever the land manager requires.

This guide is desk research from federal regulations and from BLM, Forest Service and state agency pages and permits, checked October 9, 2026. Nobody at Backyard Prospectors has run a dredge. Dredging rules change often and differ stream by stream, so treat this as a map of what to ask, and confirm the rules for your exact water with each agency before you buy anything.

What a suction dredge is

The 2018 BLM and Forest Service panning booklet for Alaska’s Kenai Peninsula defines a suction dredge as a machine that “uses a water jet and venturi effect to suck gravel off the stream bed and run it over a set of riffles.” A 2022 Forest Service handout from the Medicine Bow-Routt National Forests describes a recreational setup as a water pump driven by a small gasoline engine and a riffle box, floated on inner tubes or fiberglass floats, with the operator often in a wet or dry suit.

Oregon’s general permit separates three kinds:

  • Motorized suction dredges, where suction comes from an electric motor or engine.
  • Gravity or siphon suction dredges, which, Oregon says, do not have “an auxiliary power source.”
  • Hand suction tools, which Oregon counts as non-motorized equipment, along with hand sluices and mini rockers.

Agencies set size limits by the diameter of the suction hose, intake or nozzle, and makers name dredges the same way. As one example, Keene Engineering’s 2" Backpack Dredge with Power Jet (model 2004PJF) uses a Honda GX50 four-cycle engine. Keene lists 100 gallons per minute, 15 feet of suction hose, a capacity of 1.5 yards per hour and a net weight of 65 pounds. Search Amazon for Keene 2-inch backpack dredge 2004PJF

The federal baseline

Federal land rules are the starting point, not the last word.

  • BLM land. Under 43 CFR 3809.5, casual use “generally includes” hand panning and non-motorized sluicing, and “may include use of small portable suction dredges.” Some BLM offices are stricter. BLM Nevada’s undated collecting brochure says “sluicing, dredging and commercial mining require permits,” and BLM Alaska says suction dredges “are not allowed without a permit.” Ask the local field office before you bring one.
  • National forests. Under 36 CFR 228.4, a notice of intent to operate “is required from any person proposing to conduct operations which might cause significant disturbance of surface resources.” Gold panning and non-motorized hand sluicing are on the exempt list; dredges are not. The Medicine Bow-Routt handout says recreational dredging “is considered prospecting” under 36 CFR 228, and it asks every dredger to file its notice form.
  • Mining claims. BLM’s 2026 claims packet for Montana and the Dakotas says that to prospect on an existing unpatented claim, “you must have permission from the current claimant.” That includes dredging on someone else’s claim.

Dredging rules by state

These are the agencies’ own words, summarized. Each one links from the Sources section. Rows marked with a year come from a dated document rather than a current web page, so confirm them with that agency.

Where Dredging status (agency) Size limits the agency names
California Prohibited statewide; CDFW cannot issue permits (CDFW) None; no dredging allowed
Oregon Motorized dredges need 700-PM registration (DEQ) Up to 30 hp and a 4-inch hose, outside Essential Salmon Habitat
Oregon, salmon habitat No motorized dredges; gravity or siphon only (DEQ) Gravity or siphon hose up to 4 inches
Washington Gold and Fish pamphlet does not cover dredges; written HPA needed (WDFW) Set in the individual HPA
Idaho IDWR Letter Permit, open streams only, plus DEQ discharge coverage Nozzle 5 inches or less; motor 15 hp or less
Alaska, state land No DMLW permit, except Nome (DNR fact sheet, 2021) Intake 6 inches or less; motor 18 hp or less
Alaska, Chugach NF panning areas Active channel; ADF&G and ADEC permits on salmon streams (2018 booklet) 4-inch diameter or less
Medicine Bow-Routt NFs (WY, CO) Notice of intent; July 1 to September 10 only (Forest Service handout, 2022) Intake 3 inches or less; 10 hp or less

California

The ban comes from Fish and Game Code section 5653.1. CDFW says dredging in the state’s rivers, streams and lakes “is subject to enforcement and prosecution as a criminal misdemeanor.” SB 637, in effect since January 1, 2016, set up a framework to lift the ban, starting with a water-quality permit. The State Water Resources Control Board says it issued a draft statewide permit in 2020 but “is not proceeding with further development” of it at this time.

The same law says the definition of suction dredging does not restrict “nonmotorized recreational mining activities, including panning for gold.” CDFW adds that other laws still apply to those activities, including notifying the department before substantially changing a streambed. One trap: the Eldorado National Forest’s 2024 handout still tells dredgers to get a CDFW permit. CDFW’s own page says no such permits can be issued.

Oregon

Oregon DEQ’s 700-PM general permit, renewed effective May 23, 2025, covers small motorized dredges outside Essential Salmon Habitat, gravity or siphon dredges, and non-motorized equipment. Motorized and gravity dredges must register through DEQ’s online system, and DEQ asks for applications at least 30 days before you start. The permit “does not authorize discharges from motorized in-stream placer mining, including motorized suction dredges in Essential Salmon Habitat,” and it excludes Oregon State Scenic Waterways. DEQ also limits dredging to daylight hours and to the Oregon Department of Fish and Wildlife’s in-water work period. Hand panning is exempt, and non-motorized equipment needs no registration as long as you carry a copy of the permit.

Washington

The Washington Department of Fish and Wildlife’s Gold and Fish pamphlet serves as the permit for the activities it describes. WDFW says the current edition “does NOT authorize the use of any suction dredges, dryland dredges, gravity siphons, or motorized methods,” so you must apply for a separate, written Hydraulic Project Approval (HPA). WDFW also points dredgers to the Department of Ecology’s mineral prospecting website to check whether an area is allowed.

Idaho

The Idaho Department of Water Resources (IDWR) requires a Small Scale Mining Authorization, called a Letter Permit, for mechanized mining below the ordinary high-water mark. It covers suction dredges with a nozzle of 5 inches or less and motors rated at 15 horsepower or less, on streams IDWR lists as open. Each operator needs their own permit, “regardless of age.” IDWR also says anyone running a small suction dredge “must contact the DEQ to obtain IPDES suction dredge general permit coverage.” The South Fork Clearwater River and the McCoy Creek drainage have separate application processes.

Alaska

On state land, the Alaska Department of Natural Resources’ September 2021 fact sheet classifies a dredge with an intake of 6 inches or less, a motor of 18 horsepower or less, pumping no more than 30,000 gallons of water a day and used without mechanized support equipment as recreational. That needs no permit from its Division of Mining, Land and Water, except in the Nome Recreational Area. Dredging is not permitted in state parks. Fish rules are separate: anyone dredging in fish-bearing waters needs prior authorization from the Alaska Department of Fish and Game. DNR says dredging in salmon spawning and rearing areas is generally limited to May 15 through July 15.

On BLM land in Alaska, DNR says to contact the local BLM field office before using a dredge “of any intake size.” Along the Dalton Highway, BLM’s 2013 brochure says recreational suction dredging is prohibited on most lands in the Inner Corridor. Confirm current rules with DNR, ADF&G and the BLM field office before you dredge in Alaska.

What permits usually require

Conditions differ, but the same themes show up across the agencies:

  • A season. Fish spawning sets the dates: May 15 to July 15 in Alaska salmon areas, July 1 to September 10 in the Medicine Bow-Routt’s 2022 handout, and the state’s in-water work period in Oregon.
  • Stay in the channel. The Medicine Bow-Routt prohibits excavating into the streambank, and the Eldorado National Forest says to keep mining within the wetted perimeter.
  • Control muddy water. Oregon’s permit bars visible turbidity more than 300 feet downstream. The Medicine Bow-Routt may require operations to stay 300 feet apart in low water.
  • Keep fuel out of the stream. Eldorado requires refueling outside the stream, and Oregon requires secondary containment for fuel stored on a dredge.
  • Clean your gear. The Medicine Bow-Routt and Oregon both require checking dredges for invasive species before moving between waters.

Old mercury in dredge country

Historic gold districts can hold mercury. The U.S. Geological Survey says mercury was used widely in gold dredging until the early 1960s, and that “today, mercury is recovered as a by-product from small-scale gold-dredging operations.” Among the human-health risks it lists are improper handling of contaminated sediments and inhalation of mercury vapors. This guide does not cover handling mercury. If you find liquid mercury or amalgam in your concentrates, ask your state environmental agency what to do with it.

Before you buy a dredge

  1. Check the state first. If you live in California, a dredge is not a legal option today.
  2. Find the smallest limit that applies. If the land manager allows 3 inches and the state allows 5, the 3-inch limit is the one that counts.
  3. Line up every permit. That can mean a state water-quality permit, a fish-agency approval, and a notice of intent or BLM authorization.
  4. Check for claims. Look up existing claims in BLM records before you work a stream, and get the claimant’s permission to work one. See how mining claims work .
  5. Learn on simpler gear. A pan and a hand sluice need far less permission in most places. Start with the gold panning kits and pans or a sluice box , and use where to find gold in the US to pick a district. If you are still deciding between a detector and a dredge, read metal detecting vs gold dredging .

FAQ

It depends on the state and the land manager. California’s Department of Fish and Wildlife says suction dredging “is currently prohibited and unlawful throughout California.” Oregon, Idaho and Alaska allow small dredges under permits or size limits, and Washington requires a separate written Hydraulic Project Approval.

Do I need a permit to dredge on my own mining claim?

Usually yes. Idaho’s Department of Water Resources says owning a mineral claim does not exclude you from needing its Letter Permit and other authorizations. A claim gives you mineral rights, not a water-quality or fish-habitat permit.

What size dredge counts as recreational?

There is no single number. Examples from the agencies are a 3-inch intake and 10 horsepower in a 2022 Medicine Bow-Routt National Forests handout, 4 inches in Chugach National Forest panning areas in a 2018 booklet, a 5-inch nozzle and 15 horsepower in Idaho, and 6 inches and 18 horsepower on Alaska state land in a 2021 state fact sheet. Confirm the current limit with the agency.

Sources