The runnable season of this section changed permanently because of a hydro project that came online in November 2009. The season is now limited to the difficult-to-predict times when water spills over the dam. There are no recreational releases that provide a flow appropriate for this section.
Similar to other sections of the Ashlu, the Bottom Mile river bed was significantly altered by a major flood in November 2017. Many of the rapids are essentially unrecognizable from their previous version.
The Ashlu is truly a classic river. With section after section of diverse class IV-V whitewater, a long season and a tributary that represents one of the best day trips you'll find in the whole province, it really has no peer. The very last section of whitewater on the Ashlu is a furiously steep pile of boulders - it's not the best kayaking on the river, but it's well worth doing to run some fun rapids and to soak in the great scenery.
The Bottom Mile is good when the Ashlu is at low water. It used to be a reliable early/late season run, but now that the river is dewatered there is no seasonal window. It runs when a small amount of water spills over the dam; usually a flow of 6 to 10 cms on the online gauge is good to go. It is possible to have a great flow when the gauge reads nothing (nominal fish flow of 2-5 cms) after a rain in the winter that only fills the low elevation tributaries below the dam and gauge. You can get down the river at higher flow too (for example, when the Box is running), but most people find it's just a series of difficult ferries back and forth between portages.
The closest town to the Ashlu is Squamish. From Squamish drive up the Squamish Valley, crossing over the Cheakamus River. Heading up the Squamish you'll eventually come to a big bridge on your left (the first one) over the river - this road gives access to the Ashlu Valley. The first thing you come to are twin bridges over the river - this can be your take out, or you can take out at the powerhouse just around the corner. To reach the put in, drive approximately 1.5 km up the steep hill and start at the first place the road comes close to the river. There is good parking near the flood warning siren. Remember, the river will look very low.
After starting out and running some rocky rapids in a wide riverbed you'll pass the footing of an old bridge. This is the indicator you're getting to the first big rapid (the great 8 foot boof here changed to a rock jumble in the 2017 flood). Once you drop over you're deposited in the canyon and the big boulder action begins. When you get out to scout after this first rapid you'll be able to see the take out far below - the river is as straight as an arrow. From here down are many good boulder rapids and bedrock drops, some quite challenging. Expect a lot of scouting and relatively easy portaging. Most people will portage something. Finally, after the rapids end check the astounding view upriver - it's a good one, and a fitting end to a river that is nothing less than classic.