Formosa Mine, Riddle, Oregon


February 10, 2005: DEQ and BLM have finalized a Feasibility Study report for planning the final cleanup of the mine site and its severely impacted watershed. This report is available for public review as a download from the DEQ web site, or in hard copy at the Riddle Branch Library and Multnomah County Library. An electronic copy of the report on CD can also be mailed upon request (to the DEQ).

DEQ and BLM are planning to schedule a public meeting in April to discuss the cleanup actions recommended in the final Feasibility Study, and to report on several initiatives underway to secure funding for final cleanup of the Formosa mine site.  Meeting details will be announced in March.  


Fall 2003: Center for Environmental Equity (CEE) inspection found a failed diversion system;untreated acid mine drainage and heavy metals again flowed directly into the watershed. DEQ inspectors had been absent for 100 days.

Winter 2004: DEQ issued baseline analysis and increased cleanup cost estimate to $10 million.

Summer 2004: DEQ issued draft Feasibility Study listing cleanup options; preferred alternatives suggest cleanup  costs will be more than$15 million. Local BLM committee declined to fund a DEQ request for additional site study costs.

Fall 2004: DEQ admits that staff and financial resources for Formosa will be curtailed at year-end 2004 without an agreement with BLM to share cleanup costs.


September 2003 Update: This summer, the DEQ has been preparing a draft of a baseline human health and ecological risk assessment which will be available for public review at the Riddle Community Library in October 2003.

Due to the complexity of this project, the DEQ is amending its project timeline and budgets. This mine site may also be potential Spotted Owl habitat.

According to the DEQ's Formosa Mine page, "The Formosa Abandoned Mine site near Riddle is a high priority for environmental investigation and cleanup." However, it also states that the City of Riddle's drinking water is safe from Formosa Mine waste.

The Formosa Mine site has been declared a State Orphan Site which allows use of state funds for short term clean up and follow-up investigation since 2000. However, the DEQ is still investigating former mine owners for possible recovery of the State's clean up costs. It is also looking into other funding sources for clean-up assistance.

In 2007 the Environmental Protection Agency took responsibility for the Formosa Mine. For more information contact Denise Baker-Kircher, Remedial Project Manager, Office of environmental Cleanup:


Silver Butte Mine

Formosa Mine (formerly Silver Butte Mine) discharges metals and acid mine drainage into Middle Creek, a tributary of the Umpqua River. Mining ceased in 1993 after the flushing of 20 tons of sulfide-bearing materials into the drainage. (State and federal agencies failed to inspect the mine from the time the permit was issued in 1989 until the 1993 incident.) A 1995 reclamation attempt failed; acid and metals continue to flow into the watershed at increasing volumes from mine workings located on BLM and private land. Although new emergency clean-up began in 2000, Oregon DEQ's clean-up was limited to redirecting the acids and metals discharge.

17 miles of cutthroat, coho salmon, and steelhead bearing stream are contaminated and poisoned by metals and acid mine drainage, including the near destruction of all invertebrates. The drainage, which feeds the City of Riddle water supply, is a priority Northwest Forest Plan Tier 1 Key Watershed (high-priority restoration watershed). 

Neither BLM nor the Oregon DEQ are planning additional clean-up this year. CEE, working with Umpqua Watersheds, will continue to insist on a comprehensive clean-up plan and comprehensive public involvement. 

Welcome to Silver Butte Formosa Mine


The rest of the story ...

Japanese and Canadian mine owners walk away from pollution that threaten Riddle's drinking water (or anybody's drinking who draws from Middle or Cow creeks).

Acid Mine Drainage is flowing out of the Silver Butte Mine and into Middle Creek, a tributary of Cow Creek, and the location of the Riddle city water intake valve. Tests have found high levels of zinc and copper acids, toxic to aquatic life and dangerous to humans, where Middle Creek empties into Cow Creek (Cow Creek feeds into the South Umpqua between Riddle and Canyonville). The pollution has only about 20 more miles to go before it reaches the town's drinking water supply.1 How long it will take to get there is unknown. The pollution travels faster during the rainy season and can retreat some during the dry season. It is also unknown how many rural residents draw their drinking water from Cow Creek, upstream from Riddle.

Even though the Oregon DEQ is alarmed that the acids are much farther downstream than expected, they have only been able to budget $300,000 for a treatment system.2 When DEQ originally discovered the pollution in 1993, they fined the owners $4,000. The owners paid the fine and spent one million dollars in an attempt to clean up the site. Then they declared bankruptcy and disappeared. In 1997 BLM reported that "the creek is effectively dead with no signs of life."3

DEQ and BLM will hold periodic public meetings in Riddle to discuss the cleanup and how the public can participate.4


  • 1927: Mining operations begin at Silver Butte mine and end in 1936.

  • 1988: A survey indicated the presence of fish, including coho salmon and steelhead, in Middle Creek. There was an abundance of macro-invertebrate (insect) populations.5

  • 1990: Formosa Resources Corporation (aka Formosa Exploration Inc.) began mining operations at Silver Butte Mine. Formosa is a Canadian company with primary investors from Japan.6

  • 1990 to 1993: Formosa likely made most of their profits during this time. They extracted 350 to 400 tons a day of copper and zinc,7 and to a lesser extent, gold and silver. They did this by digging tunnels under the forest. In addition to the tunnels, Formosa created a large pond for sediments. 76 acres of the active mine site was on private land and 2 acres was on BLM land.

  • 1993: The state mining agency (DOGAMI) discovered Formosa was breaking the law. Formosa was illegally storing mining waste and had at one point dumped 260 tons of waste rock down a hillside. Formosa was also illegally storing 10,000 tons of pyrite, which combines with water to form sulfide acids.8

  • 1993: Formosa spilled diesel9 and an estimated 20 tons of pyrite and other metal-bearing sulfide minerals into Middle Creek.10 The state fined Formosa $4,000, ordered the mine to close and for Formosa to spend $1 million to clean up the site. A stream survey found Middle Creek was dead, no fish or insects were alive.

  • 1994: Formosa removed the sulfides from Middle Creek by removing all organic material from the stream bed.11 20,000 cubic yards of low-grade ore was placed in the lined pond and covered. Formosa capped mine entrances (audits) with concrete.12 A pipe was placed at the capped audits to drain the acid onto a rock slope (perhaps onto the tailings dumped over the mountain side), in hopes of preventing a direct impact to Middle Creek.

  • 1994, March: Two miles of stream were surveyed below the spill. No fish or aquatic insects were detected.

  • 1994, June: One salamander was reported in Middle Creek, but there were still no macro-invertebrates (insects).13

  • 1995: Middle Creek was declared a "Key Watershed" by President Clinton's Northwest Forest Plan. This is an area that "is crucial for maintaining and recovering habitat for at-risk stocks of anadromous salmonids and resident fish species." A Key Watershed with low water quality, such as Middle Creek, is expected to have "a high potential for restoration".14

  • 1995/96: Formosa's clean-up efforts failed. The mine entrances ooze 10 to 50 gallons of acidic water per minute.15 Acid Mine Drainage (ADM) was discovered oozing from the capped audits and from the acidic waste rock dumped over the sides of the mountain.16 The drainage pipes installed earlier had failed and acidic water flowed into Middle Creek.17

  • 1996: Formosa declared bankruptcy and abandoned the property. Vancouver attorney David Cowan, who previously represented Formosa, said the company's board of directors and its primary investor in Japan simply walked away.18

  • 2000, January: Water quality tests on Middle Creek convinced the DEQ to put the site at top priority for clean up.

Currently: Acid Mine Drainage from the Formosa operations flows into Middle Creek and South Fork Middle Creek. Middle Creek is a tributary to Cow Creek. Both watercourses are considered habitat for threatened or endangered cutthroat trout, coho salmon, and steelhead candidate species. Salmon and steelhead are no longer present in Middle Creek.19

One of the two closed audits is on BLM land. Some of the mine site (former pond, tailings, etc.) is on adjoining private land. Another open audit is on BLM land, but not considered a problem even though it oozes about 2 gallons a minute of AMD into South Fork of Middle Creek.

Recent monitoring of S. Fork Middle Creek, Middle Creek, and Cow Creek indicate that 18 stream miles have been impacted from metals contamination associated with Acid Mine Drainage (primarily cadmium, copper, lead, and zinc) from the Formosa Corporations mine at Silver Butte. The City of Riddle has a drinking water intake on Cow Creek. Based on the impacts to the creeks and the fact that this watersheds feeds the City of Riddle's drinking water source, DEQ and BLM have determined that this project is a high priority.20

If the leaking mine can't be plugged, "it's going to be ongoing for hundreds of years," said Karl Morgenstern, cleanup project manager for the Oregon DEQ. Morgenstern estimated the costs to be as much as $1 million to install either a more sophisticated piping system or to build a full-blown treatment plant.21

Larry Tuttle, director of Center for Environmental Equity, says that a treatment system will not stop the problem. "You build a pond, and it fills with rain and drainage, then it overflows and you are back where you started."

To stop the leakage altogether would probably require digging out all the remaining waste from the underground site and plugging any holes with clean rock and dirt. Morgenstern says the cost would "easily run into the millions." Neither the BLM, DEQ, or Douglas County have the budget to finance that level of clean-up.

BLM and DEQ will seek public comment on the preferred treatment option before starting the projects. Public meetings will be held in Riddle to discuss BLMís investigation work and cleanup options. A draft proposal will be available in early July with a 30-day comment period. If you would like to be sent regular 'community updates', or have concerns, questions, or comments, contact Karl Morgenstern, DEQ, 1-800-844-8467, or E. Lynn Burkett, BLM, 541-440-4930 ext. 245.

The above information was compiled by Francis Eatherington, Umpqua Watersheds, Inc. Photographs were taken on April 23, 2000.

Above: Acid Mine Discharge flows out of the
leaky seal on the mine opening. Below: The
pollution flows down the mountain into Middle Creek.

Above: Catch basins had been installed to intercept
the flow. Below: After time, they leak or overflow.

Above: The pipes that were installed to drain
the acid mine discharge, discharge the pollution
down the hill. Below: The Acid Mine
Discharge is colorful, and deadly.

Above: This old mine on BLM land was not sealed.
Acid Mine Drainage is flowing freely into the South
Fork Middle Creek watershed. Even though metal
signs surrounding this entrance say "Formosa",
BLM says this audit is not considered part of
the problem. Below: Looking inside.

1. The Wall Street Journal/Northwest. April 19, 2000. Rob Eure.
2. The Wall Street Journal/Northwest. April 19, 2000. Rob Eure.
3. Cow Creek Watershed Analysis. Roseburg District BLM. 9/5/97. page 14.
4. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
5. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
6. The News-Review. 10/4/98. Erik Robinson.
7. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
8. The Wall Street Journal/Northwest. April 19, 2000. Rob Eure.
9. The News-Review. 10/4/98. Erik Robinson.
10. Cow Creek Watershed Analysis. Roseburg District BLM. 9/5/97. page 14.
11. Cow Creek Watershed Analysis. Roseburg District BLM. 9/5/97. page 14.
12. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
13. Cow Creek Watershed Analysis. Roseburg District BLM. 9/5/97. page 14.
14. Northwest Forest Plan. 1995. B-18
15. The News-Review. 10/4/98. Erik Robinson.
16. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
17. Cow Creek Watershed Analysis. Roseburg District BLM. 9/5/97. page 14.
18. The News-Review. 10/4/98. Erik Robinson.
19. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
20. Community Update #1. Formosa Abandoned Mine Site. April, 2000. DEQ and BLM.
21. The News-Review. 10/4/98. Erik Robinson.
22. The Wall Street Journal/Northwest. April 19, 2000. Rob Eure.
23. The Wall Street Journal/Northwest. April 19, 2000. Rob Eure.