ApproachThis is a 3600’+/- ascent day. I have climbed this mountain twice. The first trip was a dry ascent in October via the Headwall Lakes approach, which is longer, but more interesting by far. On this trip, we descended via the other route, Chester Lake making a circuit for the day. The second trip was in early June and we had actually set out for another objective (Galatea), but the avalanche conditions were horrendous and we backed into this objective via the Chester Lake approach and dealt with considerable snow en route.
Park at the Chester Lake parking lot at 6200'. Go up the south side of the parking area on a ski trail that is marked blue, but turns to yellow, and takes you across Headwall Creek. Continue on the trail gaining some elevation and in about five minutes from the creek you will notice a marked single track trail on the left. This trail takes you all the way around the south side of Chester and to the upper Headwall Lake. The far end of the lake makes an excellent soft spot to have lunch and stare back across at the Haig Glacier peaks including Mount Sir Douglas.
Route DescriptionContinue up to the col between Mount Chester and The Fortress on your left. There can be a significant cornice on this col. Ascend the large talus to the right hand side of the col. This steep grind will leave you at about 8800'. Turn right (north) and finish your last 1000' on a faint trail through scree and talus to the summit of The Fortress. At the very top, you have one hands on step around to the west side, with several options to make it more interesting if you so desire. The views are surprisingly great from this summit. You seem to be perfectly located between Mt. Joffre and Mt. Assiniboine, starring right at Mt. Birdwood and the many peaks of the Haig Glacier region (“Heights of the Lower Rockies”). Of course Mount Chester is a stone's throw away as well. The east side of The Fortress is steep with tremendous exposure.
Return to the col and descend west via the Chester Lake area. After you descend from the col, just stay low and to the middle of the moraine area until you actually reach a trail that takes you to Chester Lake.