Thursday, January 4, 2007

The Milltown Dam

Now is the time to go to Bonner to see the Milltown Dam and Reservoir before it is gone. The reservoir is already effectively gone and with construction on the Clark Fork by-pass channels already underway, it won't be long (probably a couple years) before the whole area looks completely different.

Following is a story I wrote that appeared first in The Butte Weekly paying historical respect to the Milltown structure, as well as some forward speculation of what might happen during its removal. Let's be clear: once the dam is gone, the confluence of two of Montana's greatest rivers - The Clark Fork and the Blackfoot -- will be restored and the future of its fisheries will be bright as its been in over 100 years.

Coincidentally, CFWEP in partnership with Missoula's Watershed Education Network (WEN) has just completed the Milltown Education Project. The Milltown project, which was run on the ground by WEN and administered by CFWEP, took schools from Missoula, Bonner and Anaconda on field trips to the dam and reservoir and provided over 100 students with an educational experience at Milltown during its important transformation.
CFWEP is continuing trips to the site, with a date scheduled later this month for 45 Butte High students and a tentative trip for Powell County High students being planned for February.

Read the story and if you still want to learn more, the Missoula County Environmental Health Department (, the Clark Fork River Technical Assistance Committee ( and the Clark Fork Coalition ( websites all have more information. EPA project manager Russ Forba and the Natural Resource Damage Program's Doug Martin are also great contacts and can be reached at their respective offices in Helena.

The Milltown Dam and the 1908 Flood

If the EPA, State of Montana and construction contractor Envirocon get their ways – with a little cooperation from Mother Nature – the century-old Milltown Dam will be removed from the Clark Fork River sometime in 2008.

The Milltown, as Norman McLean would say, is located “at the junction of great trout rivers” (the Blackfoot and Clark Fork) just 7 miles upstream of Missoula near the burg of Bonner. The structure stands as the downstream extent of the nation’s largest contiguous complex of federal Superfund sites, beginning over 100 miles upstream in Butte.

Since the dam was completed in December 1907, it has been the holding stop for all of the contaminated sediments flowing from the Anaconda Company’s mega-mining operations in Butte and Anaconda. This amounts to nearly 7 million cubic yards of contaminated sediments (note: 1 cubic yard = 1 pick-up truck load). Roughly a third of this total – over 2 million yards of the most contaminated sediments – will be removed and sent on a train back upstream to the historic waste impoundment known as the Opportunity Ponds.

Also to be dumped at the Opportunity site will be over 4 million cubic yards of tailings scraped from the floodplain of Silver Bow Creek and anything else nasty that’s removed from the 800-plus acres designated for remediation in the stretch of the upper Clark Fork River between Warm Springs and Garrison.

That’s a lot of contamination. But it’s nothing to the Opportunity Ponds.
The Ponds served as the waste disposal unit during the majority of life of the 585-foot Washoe Smelter in Anaconda. In fact, they aren’t “ponds” anymore, but more accurately a 10-square mile area of blighted desert. To be clear, the volume of wastes being dumped in Opportunity from the various Superfund cleanups can be compared to adding an additional tablespoon of waste to a 5-gallon bucket full. It’s just not that big of a deal – not until it comes time to clean up the Opportunity Ponds.

So let’s switch our focus back downstream to Bonner. In 2003 with then-governor Judy Martz’s stamp of approval, it was decided in the EPA’s Record of Decision to remove the Milltown Dam and a bunch of its contaminated sediments.


The reasons are many and they’re good ones:

· The dam and its sediments create a groundwater contamination plume of arsenic in the town of Bonner;
· The dam is old and unstable and it blocks the passage of native fish to spawning tributaries in both the Blackfoot and Upper Clark Fork river drainages;
· Fixing the dam properly would cost nearly as much as tearing it out and contaminated sediments wouldn’t be removed to the full extent needed.
· The dam, even in optimum condition, doesn’t generate a significant amount of electricity to justify its existence.

However, this wasn’t always the case. Let it be known that when the Milltown Dam is removed, so will be one of the last standing significant remnants of Butte’s mining history in the basin.

Q. Who do you suppose was responsible for building the Milltown Dam?

A. William A. Clark.

Q. And why do you think he built it?

A. To keep the copper coming out of the ground in Butte.

This was indirectly done by supplying electricity to his lumber mills in Bonner and Missoula (one, good producing underground mine in Butte went through a trainload of timber every week), which also indirectly electrified and helped grow The Garden City in its early days. The Milltown Dam – one of the first major river dams constructed in the Columbia drainage – also marked the birth of the Montana Power Company. Furthermore, Marcus Daly built the first dam in the Upper Clark Fork basin on the Blackfoot just upstream from Bonner about 20 years before Milltown. Coincidentally, Daly’s dam, built to slow down floating logs so they could be retrieved by his own lumber mill, was torn out last fall in preparation for the Milltown’s removal; Bob Gannon removed the Montana Power Company in 2001 in preparation for his own mysterious disappearance.

Built using the standard “timber crib” technology of the day, the Milltown was an engineering stalwart, garnering lofty boasts from its chief financier, Mr. Clark just after its completion. Clark was quoted in the Daily Missoulian to the effect that the Milltown Dam was solid as a rock and would stand through thick and thin, forever more.

Damned if Mother Nature wasn’t listening and just so happened to be in the mood for a fight.

Just a few months after the construction of Milltown Dam was completed, the Clark Fork witnessed the largest flood its pale-faced inhabitants had ever seen. That spring of 1908 the river gorged to 46,000 cubic feet per second (cfs), carrying away near everything in its widened path (Note: the USGS stream gauge below the dam currently reads ~1,700 cfs or roughly four percent of the 1908 flood). Trees, bridges, fences, animals, pert near anything in the flood’s way that wasn’t nailed down and nailed down good. And there were also tailings. Lots and lots of tailings, the result of decades of dumping from mines, smelters and concentrators of The Richest Hill on Earth. It’s fair (and accurate) to say that the majority of contaminants now requiring cleanup in the Silver Bow Creek and upper Clark Fork’s floodplains were deposited in this one storm event.
One big flood + the improperly disposed wastes of the World’s largest mining camp = 120 miles of intense river damage.

As for Mr. Clark’s timber-crib dam, sturdy as it may have seemed to men, it didn’t stand a chance against a taunted and scorned Mother Nature (see photo). The massive flows topped the dam and the river began filling the powerhouse at an alarming rate. With standing water inside the dam control house reaching four feet, something had to be done quickly. Being a mining magnate has its benefits in dire times such as these.

Clark summoned a team of Butte’s underground miners – contracted as explosive experts in this case – to hurry downstream to the rescue. In order to relieve the dooming pressure on the dam and save Clark’s flooding powerhouse and the sole generation source of the infant Montana Power Company, the miners carefully and strategically blasted the south side of the dam to smithereens.

The river temporarily and partially ran free, saving the Milltown structures. Crews and horses spent the rest of the year and into 1909 reconstructing the dismantled dam; less intensive repair efforts were required standard from flood damages until MPC finally applied a concrete veneer over the timber frame in the early 1980s.

Shortly after the dam was veneered, arsenic was detected in the domestic wells of several Bonner/Milltown residents. Ever since science has been slowly but surely been leading policy makers toward the ultimate decision in 2004 to take out the state’s largest toxic sediment trap, thereby saving one town’s drinking water and paving the way to restore the confluence of two of Montana’s greatest rivers.

The estimated clean-up price tag: $111.6 million, which is the projected cost to remove the dam and powerhouse and 2.2 million cubic yards of the nastiest sediments to be sent to Opportunity; and the rebuilding/restoration efforts of putting the Clark Fork and the Blackfoot back into their new, man-made “natural” stream beds. This cost was estimated using several assumptions, the largest one being that Mother Nature will cooperate.

The devastation that followed the wake of the 1908 flood has not been witnessed since on the Clark Fork or any other river in southwest Montana for that matter. To most of us we call that type of storm “the big one.” Hydrologists have a slightly more scientific term: the 100-year flood.

By a non-hydrology definition, the 100-year flood is a flood which on the average will be equaled or exceeded once every 100 years. More accurately, it should be defined as the “1% flood,” because it has a 1% chance of occurring in any given year.

It doesn’t take a mathematician to figure out that right about the time the dam is being removed it will be statistically right about time for us to expect the upper Clark Fork to get its next big flood. What would happen if Mother Nature decided to strike her wrath twice in the same place?

In regards to stream restoration and general land reclamation projects, if She decides it’s time for a 100-year flood in 2008, the estimated cost of completing the Milltown dam removal and restoration can reasonably double. And that’s not counting the additional costs of damage to the downstream Clark Fork and any equipment that might get swept away.

Reclamation/restoration projects need time to stabilize before they can be expected to handle a storm – any storm. Vegetation needs to mature and kinks need to be worked out. If one were to ask an expert how long he/she would reasonably guess this time would be to achieve stability in order for the project to survive the impacts of a 100-year flood the answers would range no less than five years to upwards of 20.

In short, we need to go ahead with the work as planned and hope for the best in terms of Mother Nature’s cooperation. Though in hindsight, we shouldn’t taunt her with any promises of invincibility. After all, the Clark Fork belongs to her and it’s up to her what fate she has in store. At least this century around we’re trying to expedite her work rather than impede it.


cjohnson said...

Good article, but one clarification: Clark's building of the Milltown Dam had nothing to do with the birth of the Montana Power Company. MPC was created in 1912-13 by Anaconda Co. president John D. Ryan and associates by consolidating the Butte, Madison River, Billings, Hauser (Canyon Ferry), Great Falls and Thompson Falls power operations. Clark kept Milltown out of this combine. It was not acquired by MPC until 1929, after Clark's death.

Matt Vincent said...

Thanks for the correction! The information I used for the article actually came from some archival materials and from an employee of Northwestern Energy, so I'd assumed it was correct. I always like to know a little more...where can I obtain the information you referenced?

Lee said...

The only thing is, they removed a hydroelectric power plant. Score one for big coal, zero for green energy. Supposedly it was a "small power plant." How many wind generators will it take to equal the loss of that valuable resource. Coal? Other Fossil fuels? Short sightedness by well meaning but ignorant people.

Justin Ringsak said...

Lee brings up some interesting points- thanks for the comment. At peak generation, the Milltown Dam was capable of supplying 3400 kilowatts of power. Small modern hydroelectric plants typically produce about 10 megawatts (1 megawatt = 1000 kilowatts). In terms of today's energy landscape, the Milltown Dam was not much of a factor. It did block the primary fish migration route in western Montana and sequestered mine waste. Weighing the environmental costs of the Milltown Dam, most involved in the restoration of the site would agree that the Dam was doing more environmental harm than good.