Comments on Montana’s General Permit for Suction Dredging

On March 30th, 2015 we submitted these technical comments to the Montana Dept. of Environmental Quality concerning its proposed renewal of a General Permit for Suction Dredge operations.


Montana administers a federally-delegated permit program that regulates how, where, and when anyone discharges pollutants into our rivers and creeks. This program is called the Montana Pollution Discharge Elimination System, or MPDES permit program for short.  One of many activities that must obtain MPDES permits are suction dredge operations.

What are Suction Dredges?

Suction dredge mining takes place directly in river and stream channels using a floating, gas-powered vacuum attached to a sluice box.  The miner vacuums up the river bottom and runs the sediment through a mechanized sluice to separate out gold flakes.  The sediment is then spit back into the river in long, murky plumes.

The size and powder of a dredge can vary, with motors typically ranging from 2 to 50 horsepower and the vacuum nozzle ranging from 2 to 10 inches. Because it significantly disturbs the bottom of rivers and creeks, and often occurs in low-flow conditions, suction dredging represents an unnatural disturbance that can harm fisheries, aquatic habitat, and degrade local water quality.

Montana’s General Permit for Small Suction Dredges

Montana’s general permit for suction dredging is for smaller operations with a nozzle of 4 inches or smaller. Larger operations must apply for an individualized discharge permit that contain more specialized, site-specific mitigation protections. However, even small suction dredge operations can create significant local impacts.

This is why we submitted our comment letter, pinpointing several key opportunities for improvement in the general permit.  For example, we urged DEQ to amend the permit to include, among other things:

  • Closure of waters to suction dredging that are water quality impaired for sediment, turbidity, toxics or metals
  • Closure of waters part of or contained within the any designation of the National Wild and Scenic River system, state scenic waterways, state, county, national or other park systems, national monuments and designated botanical areas or areas of critical environmental concern.
  • Closure of waters with a bank to bank width of less than 10’ to prevent undercutting, erosion of stream banks and damage to riparian vegetation.

SW & WestCentral Montana’s water quality experts…

Submitting technical comments that help improve Montana’s management of water resources is part of Upper Missouri Waterkeeper’s unique value.  No other organization in SW or West-Central Montana performs this unique service: watch-dogging the actions of our decisionmakers, state agencies, and operations – and improving our rules and permits – all to ensure meaningful terms and conditions are in place that protect local water quality, fisheries, and communities.