Conservation | Science | steelhead

The science is clear on suction dredge mining

Two bills will move through the Washington legislature this session with the goal of updating the state’s laws protecting its fish and waterways from impacts of suction dredge mining. Though you may see comments from a select few upholding the activity, the science is incredibly clear on negative impacts it causes to our already-stressed fish populations. We’ll say it again:

The science is clear: Suction dredge mining degrades water quality and harms fish.  

More specifically, it causes erosion and sedimentation. It mobilizes mercury and other heavy metals. It impacts fish and the aquatic food web by destroying aquatic habitat, physically “processing” fish and aquatic life, creating fish stranding risks in dredging pools (where fish are restricted to poor habitat as a consequence of physical separation from a main body of water), and destroys riparian vegetation

But don’t take our word for it.

  1. See the LONG list of cited articles at the bottom of this post!
  2. In filing a brief with the federal 9th Circuit in support of Oregon and California laws regulating motorized mining, Washington State’s Attorney General Bob Ferguson wrote the following:

“In fact, Oregon’s statute reflects a scientific consensus about the serious environmental risks posed by suction dredge mining and need for adequate regulation . . .  Suction dredge mining can harm fish, including endangered salmonids, by disrupting spawning, creating unstable tailings, and killing eggs and larvae . . .”

Scientific studies of the effects of suction dredge mining on aquatic environments have been completed ad nauseum by the States of California and Oregon. The results of these studies consistently confirm negative impacts of suction dredge mining on water quality and fish species. In response, both states have created regulatory and legal reforms to protect their waterways. (Again, see below.)

Washington State has conducted numerous studies and scientific reviews of suction dredge mining, which have clearly demonstrated the likelihood of “incidental take” of Endangered Species Act (ESA)-listed species and critical habitat. Incidental take refers to accidental illegal activity (harming the habitat of endangered species) while a legal activity is underway.

This spring, a bill almost passed through the legislature to address these issues, but ran out of time. The bill, SB 5322, would have instituted a ban on suction dredge mining ONLY in habitat that is known to provide critical habitat for Endangered Species Act-listed salmon, steelhead, and bull trout. This is already required under the Clean Water Act, but Washington lags behind in enforcement. The Washington State Attorney General’s Office, Washington State Department of Ecology, Washington Department of Natural Resources, and Washington Department of Fish and Wildlife ALL supported this legislation. The bills will be re-introduced this winter – we urge you to support them!

Federal courts have recently ruled that discharges from motorized mining must comply with the federal Clean Water Act. Oregon, California, and Idaho have all enacted programs to comply and protect fish listed under the endangered species act, but Washington State has not.

Washington is the only state with populations of Endangered Species Act-listed Pacific salmon and steelhead that still allows suction dredge mining and other forms of motorized mineral prospecting in critical habitat for these listed endangered fish and without requiring Clean Water Act compliance. Consequently, Washington State has become a target for out-of-state miners, creating much greater pressure on our streams and a dangerous situation for our water quality and native fish.

This session, we have a chance to fix this problem. Please join us in supporting House Bill 1261/Senate Bill 5322.

Scientific studies on negative impacts of suction dredge mining:

Below is a condensed summary of information contained in pertinent scientific literature on the resource impacts associated with suction dredge mining and other forms of motorized mineral prospecting.

Scientific studies have shown suction dredge mining causes:

  • Erosion and sedimentation in streams, which can smother incubating fish eggs and invertebrates (Bash et al. 2001, Campbell 1979, Cooley 1995, Griffiths and Andrews 1981, Harvey 1986, Harvey and Lisle 1998 and 1999, Hassler et al. 1986, Jones and Stokes 2006, Madej 2004, Nightengale and Simenstad 2001, Stern 1988).
  • Water contamination by mobilizing mercury and other toxic heavy metals buried in stream sediments, which allows these contaminants to enter the food chain (Cooley 1995, Harvey and Lisle 1998, 1999, Jones and Stokes 2006, Marvin-DiPasquale et al. 2011, Moyle 2011, Washington Dept. of Ecology 2004, 2005, OAFS 2011).
  • Physical impacts to eggs, juvenile fish, invertebrates, and other aquatic organisms that are “processed” by the suction dredge or other equipment (Campbell 1979, Griffith and Andrews 1981, Harvey 1986, 1999, Hassler et al. 1986, OAFS 2013, Prussian et al. 1999, Somer and Hassler 1992, Wagener and LaPerrier 1985, Watters 1999).
  • Disturbance of natural stream processes and habitat by physically altering channel conditions and geomorphology through redistribution of stream sediment and removal of large woody debris and other habitat features (Bolton and Shellbertg 2001, Brooks 1988, Jones & Stokes 2006, Harvey and Lisle 1998, Harvey et al. 1982, Leopold et al. 1964, Miller et al. 2001, Montgomery and Buffington 1993 and 1997, USFS OWNF 1998, Cooley 1995, Moyle 2011, Thomas 1985).
  • Negative impacts to fish redds, either by physical disturbance or destabilizing gravel beds, increasing the susceptibility of redds to washing-out during high flow events (Jones and Stokes 2006, Harvey and Lisle 1998, Harvey and Lisle 1999, Moyle 2011, Stern 1988).
  • Destruction of riparian vegetation at equipment access points and streamside campsites due to long-term use (Cooley 1995, NAWA 2002, OCAFS 2015).
  • Introduction of invasive species into streams and rivers, which can have significant economic and environmental impacts (Cusak 2009, Northwest Environmental Defense Center 2013, Upper Missouri Waterkeepter 2015).
  • Cumulative impacts from suction dredging are cited by biologists as likely the largest long-term negative effects of this activity, particularly on small streams. (Bayley 2003, Moyle 2011, OAFS 2013).

Literature Cited

Bash, J., C. Berman, S. Bolton, and E. Molash. 2001. Effects of turbidity and suspended solids on salmonids. Final Research Report T1803, Task 42, Effects of turbidity on salmon. Report prepared for Washington State Transportation Commission, Department of Transportation in cooperation with U.S. Department of Transportation, Federal Highway Administration. November.

Bayley, P. 2003. Response of fish to cumulative effects of suction dredge and hydraulic mining in the Illinois subbasin, Siskiyou National Forest, Oregon.

Birtwell, I. K. 1999. The effects of sediment on fish and their habitat. Canadian Stock Assessment, Secretariat Research Document 99/139.

Bolton, Susan and Jeff Shellberg. 2001. Ecological issues in floodplains and riparian corridors. Submitted to Washington Department of Fish and Wildlife Washington Department of Ecology Washington Department of Transportation. Available at:

Box, J.B., D. Wolf, J. Howard, C. O’Brien, D. Nez, and D. Close. 2003. The distribution and status of freshwater mussels in the Umalilla River system. Prepared for Bonneville Power Administration. Project No. 2002-037-00. Portland, OR. 74 pp.

Brookes, A. 1988. Channelized Rivers: Perspectives for Environmental Management. John Wiley and Sons. Chichester, U.K. (cited in Bolton and Shellberg 2001).

Campbell, H.J. 1979. The effect of siltation from gold dredging on the survival of rainbow trout and eyed eggs in Powder River, Oregon.

Cooley, M.F. 1995. A comparison of stream materials moved by mining suction dredge operations to the natural sediment rates. USDA Siskiyou National Forest. October 16, 1995.

Cusak, C. 2009 The Economics of Invasive Species. Oregon State University: Prepared for the Oregon State Invasive Species Council

Everest, F.H., R.L. Beschta, J.C. Schrivener, K.V. Koski, J.R. Sedell, and C.J. Cederholm. 1987. Chapter 4. Fine sediment and salmonid production: A paradox. In: Salo, E.O., T.W. Cundy, editors. Streamside Management. Forestry and Fishery Interactions. University of Washington, Institute of Forest Resources. Contribution No. 57. P. 98-142.

Griffith, J.S., and D.A. Andrews. 1981. Effects of a small suction dredge on fishes and aquatic invertebrates in Idaho streams. North American Journal of Fisheries Management. 1:21-28.

Harvey, B. 1986. Effects of suction gold dredging on fish and invertebrates in two California streams. North American Journal of Fisheries Management. 6:401-409.

Harvey, B.H. and T.E. Lisle 1998. Effects of Suction Dredging on Streams; A Review and an Evaluation Strategy. Fisheries 23 (8) 8-17. Available at

Harvey B.H. and T.E. Lisle 1999. Scour of Chinook Salmon Redds on Suction Dredge Tailings. North American Journal of Fisheries Management 19:613-617. Available at

Harvey, B., K. McCleneghan, J. Linn, and C. Langley. 1982. Some physical and biological effects of suction dredge mining. California Department of Fish and Game Environmental Services Branch Fish and Wildlife Water Pollution Control Laboratory. Laboratory Report No. 82-3. Rancho Cordova, California.

Hassler, T.J., W.L. Somer, and G.R. Stern. 1986. Impacts of suction dredge mining on anadromous fish, invertebrates and habitat in Canyon Creek, California. California Cooperative Fishery Research Unit, U.S. Fish and Wildlife Service, Humboldt State.

Horizon Water and Environment [HWE]. 2009. Suction Dredge Permitting Program. Literature review on the impacts of suction dredge mining in California. Available at

Horizon Water and Environment [HWE]. 2011. Suction Dredge Permitting Program-Draft Subsequent Environmental Impact Report. (HWE 09.005) Oakland, CA. Available at

Jones & Stokes Associates, Anchor Environmental LLC, and R2 Resource Consultants. 2006. Water Crossings White Paper. Prepared for Washington Department of Fish and Wildlife. December 2006.

Leopold, L.B., M.G. Wolman, and J.P. Miller, 1964. Fluvial Processes in Geomorphology. San Francisco: W. H. Freeman and Company, pp. 156-160.

Madej, M. 2004. How suspended organic sediment affects turbidity and fish feeding. USGS Coastal Science and Research News.

Marking, R. H. and T. D. Bills. Acute effects of silt and sand sedimentation on freshwater mussels. pp. 204-2 11. In: Proceedings of the Symposium on Upper Mississippi River Bivalve Mollusks.

(Rasmussen J. L., Ed.). Rock Island, Il: Upper Mississippi River Conservation Committee (1980). In Henley et al. 2000.

Marvin-DiPasquale, M., J. Agee, E. Kakouros, L.H. Kieu, J.A. Fleck, and C.N. Alpers. 2011. The Effects of Sediment and Mercury Mobilization in the South Yuba River and Humbug Creek Confluence Area, Nevada County, California: Concentrations, Speciation and Environmental Fate. Part 2: Laboratory Experiments. U.S. Geological Survey Open File Report 2010-1325B.

Miller, D.E., P.B. Skidmore, and D.J. White. 2001. Channel design. Submitted to Washington Department of Fish and Wildlife, Washington Department of Ecology, and the Washington Department of Transportation.

Montgomery, David R. and John M. Buffington. 1993. Channel Classification, Prediction of Channel Response, and Assessment of Channel Condition. Timber, Fish & Wildlife TFW-SH10-93-002. FW_SH10_93_002.pdf.

Montgomery, David R. and John M. Buffington. 1997. Channel-reach morphology in mountain drainage basins. GSA Bulletin 109(5):596–611.

Moyle, Peter 2011, Suction Dredging is Bad for Fish, California Water Blog.

Nawa, R.K. 2002. Observations of Mining Activities in Siskiyou National Forest Riparian Reserves and Probable Impacts to Aquatic Organisms. Siskiyou Project, 213 SE “H” Street, Grants Pass, OR 97526.

Newcombe, C.P. and D.D. MacDonald. 1991. Effects of suspended sediments on aquatic ecosystems. N. Am. J. Fish. Management, 11: 72-82.

Nightingale, B. and C. Simenstad. 2001. Dredging Activities: Marine Issues. University of Washington. Prepared for the Washington Department of Fish and Wildlife, Washington Department of Ecology, and Washington Department of Transportation.

Northwest Environmental Defense Center 2013 Correspondence to David Ades, Oregon Department of Environmental Quality.

Oregon Chapter American Fisheries Society [OAFS]. 2011. White paper on heavy metals in the aquatic environment. Available at

Oregon Chapter American Fisheries Society [OAFS]. 2013. Testimony to the Oregon State Legislature. April 2013.

Prussian, A., T. Royer, and W. Minshall. 1999. Impact of suction dredging on water quality, benthic habitat, and biota in the Fortymile River, Resurrection Creek, and Chatanika River, Alaska. Prepared for the U.S. Environmental Protection Agency.

Somer, W. L., and T. J. Hassler. 1992. Effects of suction-dredge gold mining on benthic invertebrates in a Northern California stream. North American Journal of Fisheries Management. 12:244-252.

Stern, G. 1988. Effects of suction dredge mining on anadromous salmonid habitat in Canyon Creek, Trinity County, California. A thesis presented to the faculty of Humboldt State University in partial fulfillment of the requirements for the Degree of Master of Science.

Thomas, V. 1985. Experimentally determined impacts of a small, suction gold dredge on a Montana stream. North American Journal of Fisheries Management. 5:480-488.

Upper Missouri Waterkeeper 2015 Correspondence to Montana DEQ Permitting and Compliance Division on Proposed Suction Dredge General Permit MTG37000.

USFS. 1998. Fisheries Biological Assessment for On-Going Activities; Peshastin Creek Watershed. Okanogan and Wenatchee National Forest, Leavenworth Ranger District. Wenatchee, WA. 22 pp.

Wagener, S. and J. LaPerriere. 1985. Effects of placer mining on the invertebrate communities of interior Alaska streams. Freshwater Invertebrate Biology 4(4):208-214.

Washington State Department of Ecology (Ecology). 2004. Quality Assurance Project Plan; Effects of small-scale gold dredging on arsenic, copper, lead, and zinc concentrations in the Similkameen River. Publication No. 04-03-108. Olympia, Washington.

Washington State Department of Ecology (Ecology). 2005. Effects of small-scale gold dredging on arsenic, copper, lead, and zinc concentrations in the Similkameen River. Publication No. 05-03-007. Olympia, Washington.

Watters, G.T. 1999. Freshwater mussels and water quality: A review of the effects of hydrologic and instream habitat alterations. Proceedings of the First Freshwater Mollusk Conservation Symposium. Pgs. 261-274.