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Clark Fork cruise, continued…

July 30, 2010

My put-in for the Mill-Willow Bypass, at Interstate 90.

Thursday, July 29—Today I took the canoe out for Part II of my segmented 120-mile paddle from the Clark Fork River’s headwaters to Missoula.

Part II isn’t technically the Clark Fork at all, but the river itself washes out into the fragmentary slackwater of the Warm Springs Ponds complex just downstream from where I ended Part I of my float a few weeks back.

I launched this time a few hundred yards downstream from there, where two feeder creeks join to form something called the Mill-Willow Bypass.

It’s a confused and confusing waterway, so maybe a bit of background will help. Here’s a map. You’ll want to zoom in to really see the bypass channel, but it’s just to the right of Interstate 90 here:

Originally, before industrialists decided the river would better suit their purposes mangled (and in fairness, once you accept the baseline degradation of tailings waste as necessary, the ponds were considered a relatively progressive abatement for their time), there were no “ponds” here, just Silver Bow Creek becoming the Clark Fork River, into which flowed numerous small feeder creeks, including, in this upper stretch, Mill Creek, Willow Creek, and, a little farther downstream, Warm Springs Creek.

Typical stretch of the 6.2 mile Mill-Willow Bypass.

In 1911, the Anaconda Mining Company built an earthen dam on Silver Bow Creek to create a settling pond, or a “slum pond.” The pond was designed to slow the river and allow mine tailings to drop out onto the pond floor, thereby more or less arresting their movement downstream. Over the years, the one pond was expanded to a series of three ponds that have collectively trapped an estimated 19 million cubic yards of copper mining tailings, i.e. waste rock sediments containing toxic levels of heavy metals and arsenic. In 1960, active water treatment began at the ponds. In 1964, the Anaconda Company reached an agreement with Montana’s Department of Fish, Wildlife & Parks to manage the ponds as a wildlife area. Today, during the winter months, lime is added to the water to reduce its acidity. At the tail end of the 600 surface-acre complex, the treated water is released into a channel that continues, with more or less integrity, as the reconstituted Clark Fork River.

Note the earthen berm impounding Warm Springs Ponds at the horizon.

Rather than allow the more or less clean Mill Creek and Willow Creek to pour into the Clark Fork upstream of the ponds, where it would add unnecessarily to the treatment burden, those creeks were shunted, at a date I haven’t found yet, into the engineered Mill-Willow Bypass, which rejoins the Clark Fork downstream of the various pond impoundments.

In 1989, rapid snowmelt and heavy rains caused the ponds to overflow into the bypass, flushing the ponds’ toxins into the stream and causing a massive fish kill for miles downstream. By that point, the Anaconda Company had merged (in 1977) with oil giant Atlantic Richfield Company, which shuttered its Montana mining operations in 1980.

Beaver dam on Mill-Willow Bypass.

In response to the overflow and fish kill, ARCO and the state upgraded the pond system dramatically to meet flood and earthquake requirements, and incidentally to improve wildlife habitat. (The Warm Springs Ponds complex is currently a wildlife management area, overseen by the unlikely partnership of FW&P and ARCO, and promoted and reasonably heavily used as a site for birding, fishing, boating and hiking.

Is this a beaver cut?

In the process, the Mill-Willow Bypass was completely reconstructed, from the ground up, as it were. Spillover sedimentswere excavated and removed to the nearby Opportunity Ponds, and a meandering channel was built to mimic natural stream migration patterns (though the channel is sandwiched so tightly between the dykes containing the ponds on one side and Interstate 90 on the other that there’s not really much room for it to move). The streambanks were stabilized with stone and crushed concrete and vegetated with willows. Manmade “oxbow” lakes were placed along its course, where they spill in trickles through artificial wetlands and back into the bypass. A few access points were constructed, and have become overcrowded shore-fishing spots.

Water spilling into the Mill-Willow Bypass from one of many manmade oxbow lakes along its course.

So that’s the Mill-Willow Bypass, and that’s what I paddled today, most of its 6.2 miles, from a little overpass on the I-90 feeder road down to the official access site at Warm Springs.

And though it wasn’t designed for canoeing—too shallow, too twisty, half-assed boat access—it was reasonably pretty, and kind of impressive, especially considering that the original reconstruction plan called for a straight concrete-banked channel.

In fact unless you’re seeing the almost too-“natural” aerial view or know what you’re looking for, you might not know the whole thing is man-made. A 2001 documentary (by BP/ARCO; the former having bought out the latter) claims the Mill-Willow Bypass “has now achieved 100% biointegrity,” and become one of the top trout-spawning tributaries of the entire upper Clark Fork, which is good, of course, but isn’t actually saying much.

My take-out at the wildlife management area access near Warm Springs.

Unlike the section above it, the banks here are crowded with mature willows and grasses. Fish dart through the shallow riffles and diving ducks feed beneath the surface. Birds are common in the head-high vegetation lining the river, and the water is crystal clear, even given the heavy algae bloom standard to late summer. I saw four beavers plying the waters, and had to portage two beaver dams, though I’m not certain that even those were entirely natural constructions. The preponderance of dam timber had sharp single-angled ends, as if cut by a saw or axe, and not the conical chew patterns I’m used to associating with beavers.

Regardless, there was no mistaking Mill-Willow for a wilderness stream: It was rare that the obviously manmade earthen berms holding back the ponds to the north were out of sight, and the sound of traffic on I-90 to the west—which you can often enough see from the canoe—never once fades beyond the immediate.

Spillway from the Warm Springs Ponds into Mill-Willow Bypass near Warm Springs.

Still, it’s an instructive example of how a much-fucked-with waterway can be restored to something that more approximates a stream than a sluice for poisons or a mere diversion ditch.

When I took out, where the main braid of stream joined the outflow of a small spillway emptying one of the ponds, there was a fly fisherman wading the slippery stone bed. I’m still not sure I’d want to eat whatever he might catch, but at least there’s catching to be done.

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