The Pierce Lake Trail passes by the larger of the two lakes and then becomes an unofficial trail leading to the smaller upper lake, a gain of over 1200 meters. From there another boot path splits off over toward the south ridge of Mount Pierce, which is another 150 meters above the lake. Along the south ridge there are a few short scramble sections, class 2 and 3.
Upper Pierce Lake is nestled in an amphitheater shaped bowl. On the other side of the bowl sits Mount Macfarlane. Those with extra vigor may wish to ascend both Pierce and Macfarlane for a full day trip. But many average parties may prefer to take two days. From the trailhead to the summit requires 1650 meters of vertical gain (5413 feet) and 21 kilometers round-trip (13 miles).
Follow the trail until it comes to a log bridge across Pierce Creek. On the far side of Pierce Creek continue along the trail to Pierce Lake. From Pierce Lake continue on the trail as it crosses an open slope east of the lake and then ascends the upper basin though an avalanche debris zone. The trail is less well defined here and might be soggy in the spring or early summer. There are a few steep sections which bypass headwalls.
Below the first headwall, cross the creek to the left side, where the trail goes up through the trees. Eventually you will come to the base of the second headwall. The second headwall has an obvious ledge which traverses through the middle of it. Do not be tempted to use the ledge. It is down-sloping and hazardous when wet. Instead, follow the faint trail across the talus which ends at the right side of the headwall. Here you will see where the trail ascends steep dirt along the right.
Above the second headwall the trail ascends left of the creek on open slopes until it reaches the base of some bare rock slabs. Scramble up the slabs and you will come to Upper Pierce Lake. From the upper lake, turn left and follow the boot path over to the south ridge of Mount Pierce. First pass over a bump on the ridge with a scramble step at the far side. Then follow the ridge north to the summit. There is one unavoidable class 3 section which is 7 meters high and has some loose rock. Excercise caution there.
When To Climb / Camping
To the best of my knowledge, camping is permitted. Leave no trace and use extra care in alpine zones with respect to sensitive plant life.