UN13,100B can be done as a day hike from the Eagle Lake Trailhead for a moderately long day which is how we present it here. It could also be combined with Ribbed Peak as an even longer day hike bearing in mind the exposed-to-weather ridge traverse may take 2 - 3 hours. A third option would be to do this summit on a separate day with Ribbed Peak on another day with a backpack trip up to Fairview Lake. Also, the unranked Eagle Peak which lies a short distance north along the ridge, some may want to tag on this climb. See that summit for more information. We also mention that sometimes in ascending a peak, you find what would have been a better route up, by coming down a different way. Such is the case here. We will describe our ascent route which takes you closer to Fool's Peak, then traverses east along a ridge to the summit. But the route we took back down would make an overall easier way up and down.
From the trailhead parking, a well-marked and used trail heads out NE across open meadows before entering aspen forest. In later June, the wildflowers in this meadow and throughout the lower elevation forest are amazing. The trail exists to skirt the private property around Wood's Lake, so it gradually gains nearly 400 feet in elevation for the first mile before losing much of that elevation to drop back down to and reconnect with the road that exits the property at its east end and continues to an old building and a sturdy foot-bridge across Lime Creek. There's a great campsite shortly before that crossing.
Once across the bridge, there's a Wilderness Registration where you can obtain your permit for overnight camping. Immediately after, the trail climbs up steeply and then quickly levels to wind its way east back to Eagle Lake. It gains elevation in pitches with intervening level areas. There's a waterfall on Lime Creek along the way.
When you arrive at Eagle Lake, (about 1:45 from the TH) you must cross the western outlet on a log jam mass to resume the trail along the north shore of the lake. Not long after crossing are some "designated" campsites. Midway along the north shore is another good camping area near where a promontory juts into the lake. Beyond the lake, the trail heads into forest, crosses into an open area which is the bottom of an avalanche chute that you use to access UN13,100B, then re-enters forest. There is an area of downed timber that makes following the trail difficult. Beyond Eagle Lake, we don't think the trail receives maintenance anyhow. What now follows is our edited account of this climb:
It was at the peninsula on the north side of Eagle Lake, and the campsites there that we examined the USGS map and decided to begin our climb towards UN13,100. The map showed two large open swaths of terrain with a dividing area of trees that would lead into a basin that empties down from Eagle Peak to the SW, back to Eagle Lake. Our plan was to follow the western most swath and gain that upper basin that would place us SW of the Eagle Peak summit. Well, plans and terrain have a way of changing. We began the ascent to the NE expecting to cut through a few trees and then find open slopes. That never happened. What we found was a forest of low, young aspens and cliffbands that tended us more to the north than intended, hence too far to the west. We never made it into the intended basin. Instead, we found ourselves bushwhacking through steep and difficult terrain and almost every effort to head more to the east was rebutted. Eventually, we found ourselves on the edge of a drainage that comes down from the south side of Fool’s Peak. So for several hundred feet of gain, we worked our way through forest that began to open up and at the last trees around 11,500 feet, we began to swing NE. We took a break here around some boulders we could sit on.
We examined the map and determined that we were below an unnamed and unranked double summit that falls on the connecting ridge between Eagle Peak and Fool’s Peak. So we continued hiking over tundra and increasing rock toward the eastern end of that unnamed summit, and could overlook the basin we had intended to be in. Abrupt cliffs kept us from dropping into that basin at any point and forced us up to the ridge above. We joined the connecting, east-west ridge, just east of the unnamed summit.
We hiked along the ridge to the east and toward the Eagle Peak summit. Much of this connecting ridge was comprised of rock, some embedded in tundra. Along the way, there were two smaller high points and resulting drops or notches in between. The first was of no consequence to navigate, but the second notch was covered by a hardened snowbank with a dangerous drop to either side. We could have been across in just a few steps but even with ice axes, we did not feel secure enough to do it, so we were forced to drop on the south side of the ridge and into a steep, loose rock couloir that we then had to climb back up out of. The downclimb was tricky and 3rd class. We had to exercise some care to not fall and/or put a rock down on each other. This cost us at least 100 feet in elevation loss. For a short stretch, we regained the ridgeline as we continued east to Eagle Peak, but then decided that since the Eagle summit doesn’t actually count and since the ranked unnamed summit is south of Eagle Peak, we would just contour over to the connecting ridge. This took us across loose rock, boulders, and rubble of various sorts until we gained the ridge. From where we intersected the Eagle Peak - UN13,100B ridge, it was 15 minutes of scrambling north over boulders to Eagle Peak. We tagged the summit and then had to walk south along the summit ridge that was mostly comprised of block boulders resulting in some slower scrambling. All along the east ridge and now the south ridge of Eagle Peak, there were dramatic drops and rugged cliffs on the north and east side. We finished the walk to the top over yet more boulders, rubble, etc. This took us about 5 hours from the TH.
We soon departed our rocky summit where we enjoyed views of the very rugged peaks surrounding this location. This area is part of what we would call the core of the Holy Cross Wilderness. The mountains are the most rugged here and show the most obvious signs of prior glaciation. There are rugged cirques carved out of the rock, great rock glaciers, high, hanging valleys and tumbling streams and waterfalls. Most of the peaks surrounding Lime Creek are very rugged and steep.
As we headed on down, we had yet another 1,000 feet of descending on large boulder talus to add to the days frustrations. We made an almost westward descent in the direction of the basin below the connecting ridge of Eagle Peak and UN13,100B. After a while, the rock began to give way to tundra and we found ourselves negotiating steep, flower-laden tundra down into the basin below us. Along the way, we saw abundant evidence of mountain goats, but never actually spotted any. We arrived more than an hour later back in the basin we had hoped to be in that morning. There was a pleasant bench area at about 11,200 feet where some open forest begins to appear, but mosquitoes here were fierce. We also began to spot a few cairns and so began our descent to the valley bottom using those indicators as a guide. The cairns led us down the west side of the main drainage. Once again, the map indicated it should have been open terrain, but we found more of that low-growing aspen forest with some conifers mixed in. There was a lot of brush to deal with as we descended. At times, we would pick up a faint trail or see another cairn only to lose the way, if there really was one. Toward the bottom of the drainage, the slope angle began to relent and we could walk down in taller grass now with hidden avalanche debris of logs and boulders. We joined the main valley trail about 2/5ths of a mile east of Eagle Lake, where the stream makes a loop to the north just a little and on the edge of another forested section. This is the bottom of an avalanche chute. Relieved to be back on an easy trail, we headed back to Eagle Lake. It took us about 10 minutes of walking to arrive at the east end of the lake. If deciding to go up our descent route, these are the coordinates for where to begin the ascent up the avalanche chute: N 39° 25' 57.75" W 106° 35' 35.89".
Links to other information, routes & trip reports for this peak that may be helpful.