Among the best.
Boundary is a sweet canyon tucked between "The Big Ones" up on Kolob Terrace, and is one of the best canyons in Zion. It makes a nice daytrip exiting out the MIA, or a great way to access Kolob Creek for a high-class, technical backpack trip. The technical part of the canyon starts right AT the Park Boundary, thus the name.
In the spring the canyon runs with snowmelt and can be too burly. By the time the West Rim Trailhead opens, it may or may not be down to a reasonable level. In recent years, after big winters, it has run strong all summer, and full wetsuits have definitely been required. In dry years, it may dry out in summer - hard to say when. When wet, Boundary is as cold as Imlay or Kolob - bring plenty of warmth or suffer mightily.
The walk from the intersection with Kolob Canyon to the MIA exit is IN Kolob Creek, so be sure to check the release level of the Kolob Dam by calling the Washington County Water Conservancy District (435-673-3617) AND check the flow where the Kolob Terrace Road crosses Kolob Creek, 1.2 miles north of the Lava Point Road. Hiking in Kolob Canyon with more than 10 cfs, even just to the MIA exit, can be challenging and slow; but there are no technical obstacles so it is certainly possible.
Boundary Canyon is a Class C canyon when wet and Class C techniques should be used. Carry an extra rope in case you get one stuck. Perhaps two.
6 to 10 hours (as a day trip) or can overnight and exit via the Narrows
Only if camping in Kolob Canyon and exiting via the Narrows
Summer or fall
100 feet (30 m)
Boundary is commonly done two ways. For a day trip out the MIA Trail, park at the West Rim Trailhead near Lava Point. The MIA Trail returns to this point. For a two-day trip enjoying the full glory of Kolob Canyon and the Narrows, start from the West Rim Trailhead (car spot, shuttle service) and exit at the Temple of Sinawava.
Though not INSIDE the Park, any rescue in Kolob or Boundary would involve the NPS SAR team.
Zion Wilderness Desk: (435) 772-0170
Zion EMERGENCY: (435) 772-3322
Helmets, rappeling gear, webbing and rapid links
COLD WATER PROTECTION
Full wetsuits or drysuits when it is wet.
Once in the canyon, clear water is usually available to filter. Water is available at the Pipe Spring on the MIA exit.
FLASH FLOOD RISK
Moderate: small, wooded collection zone, but the canyon itself offers prolonged narrows with no escape areas.
Class C canyon techniques recommended. Be careful with the pulls, and carry an extra rope in case you stick one. Long exposure to cold water.
A mix of bolted and natural anchors. Bring webbing and rapid links.
In winter and spring, the area is likely blanketed in snow. In early summer, the flow may be too heavy for safe passage.
Note: this is a revision to the approach in the Zion: Canyoneering guidebook.
The approach to Boundary starts the same as that for Kolob Canyon. Park at the West Rim Trailhead. Walk back along the road a few minutes to the big turn. Continue straight north across the meadow to a gap in the trees, a post and the start of a road. Follow the road down a few feet, then follow it left and traverse steeply downhill 15 minutes to the bottom of a hill and a meadow, that holds the spring at the head of Boundary Canyon. If the spring is running, it likely means that Boundary is running too. Follow a logging road right and down along the side of the stream and through lush woods.
Follow the grown-over logging road east, mostly along the right side of the drainage, to the Park Boundary (wire fence) and the head of the canyon. Allow one hour walking time to the head of the canyon.
Note: The MIA road is not always locked, but could be locked at any time. Please DO NOT drive the MIA road without permission; doing so is not only illegal, but it estranges the relationship between the canyoneering community and the (thus far) friendly land owners.
Note: this is a revision to the description in the Zion: Canyoneering guidebook.
R1: Find a tree to sling at the head of the watercourse. Rappel 100 feet (30 m) past several waterfall steps to a round pothole with a log in it and a tree on the side, with a bolt at its base.
R2: 100 feet (30 m) past several ledges to a large pothole ledge. Make sure the rope does not cross any remnant cairn anchors where it could get stuck.
R3: 50 feet (15 m) off a tied-off log to a ledge. Lots of wood debris is in this area, and might be unstable.
R4: 50 feet (15 m) off a tied-off log down a short flute to a ledge. Use the log back one step and pass the sling over a fin, so the rope does not get jammed in the chockstone at the lip of the drop.
R5: 80 feet (24 m) off bolts down nice flute. Wonderful!!
R6: 100 feet (30 m) off bolts down a great flute. An interesting arch!
R7: 30 feet (10 m) off natural anchors.
R8: 30 feet (10 m) off natural anchors.
R9: Off bolts, 70 feet (21 m) down a steep wall to the bottom of the canyon.
The rappel sequence leads to the floor of a beautiful canyon, lush with vegetation, with huge sweeping walls. Descent of the lush, rugged canyon to the intersection with Kolob Creek takes about 1 hour.
March down Kolob Creek to the MIA Exit, and back up to the West Rim Trailhead, OR hike down Kolob Creek to The Narrows, likely camping in there somewhere, and out to the Temple of Sinawava.
THE MIA EXIT:
While the MIA Exit is not hard to find, many a canyoneer has walked past it due to inattention. Noting the intersection of Boundary Canyon with Kolob Canyon is the key to finding the MIA Route. The MIA should not be attempted in the dark. The first time, most parties will require at least 2 hours for the MIA, plus another hour to hike back to the trailhead.
The Boundary Intersection is marked by Boundary Canyon coming into Kolob Canyon on canyon right as a 50' wide, vegetated and not-steep canyon, and a steep, small, vegetated slot coming in across the way. There is a large flat rock right at the intersection that makes a great place to remove wetsuits and harnesses, and prepare for the ordeal ahead. Between Boundary and the MIA there are no rappels, and usually two places where wading deeper than waist deep is required.
From Boundary, Kolob creek is rocky and wide for about 20 minutes, then enters a short (5 minute), tall, narrows section. Next, the canyon opens out again and proceeds as a rocky streambed for perhaps 20 minutes, then again enters a tall narrows section, which is considerably longer (15 minutes). Approximately 10 minutes after the second narrows section, MIA canyon comes in on canyon right, as a large, indisputable, lushly vegetated and steep (but climbable) sandy slope. There may be two big ol' logs in the streambed and cairns often mark the intersection. This is the only possible-looking exit since Boundary, due to tall, unbroken canyon walls.
The MIA Exit - more details
The MIA Exit
To the right of Anna and Yuhua.
Climb the steep, wooded slope above Kolob Canyon, starting behind several large rocks in the streambed, up, then work left at the toe of a rock buttress. Traverse left, then down to the top of a short pourover. You are now in the main MIA canyon watercourse. Scramble upcanyon. A short wall is surmounted either directly, or by climbing a ramp on the right and stepping back left. At the next obstacle, climb a steep slope on the left to gain an exposed traverse ledge - or, climb a steep slope on the right, then traverse easily back into the main watercourse. The main watercourse soon ends at a 40-foot (12 m) dryfall with a wider-than-fists crack in the back. Stop 30 feet (10 m) back from the dryfall and ascend the noticeably smaller drainage on the right.
Follow the drainage upward, to the base of a wall. Climb left along the base of the wall, then up again. Traverse left through brush to a wide pass that overlooks the upper basin of MIA Canyon (30 minutes to this point).
From this viewpoint, carefully examine the complex terrain ahead. The upper basin is bounded on the left by cliffs and then a slinky little slot canyon (MIA Slot) dropping steeply into the basin (this is just above the "4WD" annotation on the map). To the right of this, is a complex, steep and tree-covered face that slides over into a deep slot canyon on the right. Take careful note of three snags (dead trees) at the canyon rim above the middle-left of the complex face – the three snags are where you are trying to go.
Descend to the bottom of the upper basin, and head for the bottom of the MIA slot on the left. The slot is well worth a few minutes of exploration. Follow the main watercourse past automotive debris washed down from above. Follow this canyon five minutes along the basin floor, until it turns right and heads for the right-hand wall and slot. At this point, climb steep dirt directly up the fall line, following a shallow watercourse on a fairly good social trail.
To this point, the dreaded MIA Trail is not so bad. It gets worse.
Follow the trail steeply upward. It is important to "Follow The Trail". In the brush, the trail is easy to find, but there are several sections where the trail crosses open ground and several options all look pretty much the same. At one point, stay right and scramble steeply up rocks. At other points, walking a few feet to check out the options will reveal the correct trail.
In general, when hunting for the trail, follow the watercourse. Explore, figure out which is the correct path, and follow it. Even the best trail is steep and difficult - persevere. Keep the three snags in sight.
Near the top, the trail is less well-defined and climbs a few sections of steep, loose rock. Be careful of partner-generated rockfall. Ascend to the road.
Back to the West Rim Trailhead
From the top of the MIA Route, once on the logging road, turn left (south) and hike about 1000 feet (300 m) to a picnic area with water coming from a pipe. This is the Pipe Spring. Hike the road heading uphill behind the spring 365 feet, then turn 90 degrees right and charge up the hillside, following a somewhat overgrown two-track. Follow this up, then right to the actual source of the spring. Then follow the roads (generally north and west, but always up) to the West Rim Trailhead. Allow an hour for the MIA Route and an hour for the roadwalk back to the Trailhead. First time MIA'ers are likely to take longer.
I first did Boundary in the fall of 2002, I think, in dry conditions with Kurt and Melody Bellock, Alicia Scotter and Allen Sanderson. I have repeated it about once a year since, though it is more fun in recent years as the flows have been higher.