If you have not read the Special Introduction to Imlay and Heaps , you really should.
Imlay Canyon from Potato Hollow
Full Imlay is usually done from Potato Hollow, though other entrances into the complex drainage can be made.
From Lava Point, hike the West Rim Trail 5.1 miles (8 km) to Potato Hollow. A trail leads left to a small pond and a designated camping site. Follow the outlet of the pond to the head of the canyon. There is often a trickle of water in the stream. (Note: one can also hike up from the floor of the Main Zion Canyon ).
Traverse the left rim 1/8 mile (200m) to a small bowl with two pine trees. Downclimb through a break in the cliffband to the lowest pine.
R1: Rap 140 feet (40m) to a large pine tree. R2: Rap 120 feet (35m) to the creek bottom. R3: Rap 120 feet (35m) off of logs in the streambed through multiple pools past an old piton. The pools are usually waist deep.
Climb down the canyon. One section may be easier to rappel. At a steep pouroff, climb left up dirt and brush, then down to a small tree.
R4: Rap 120 feet (35m) past a large tree to a ledge with bolts at the rollover. R5: Rap 165 feet (50m) down a steep wall to a big ledge atop a ridge.
Downclimb to the end of the ridge, then off the right side down steep dirt into the wash. Several hours of interesting canyon with numerous short rappels lead to The Crossroads. The pools get deeper as the canyon progresses - suit up after encountering the first waist-deep pool.
The Crossroads is a complex area where numerous canyons come in from both sides. The Sneak Route comes in on the right. After The Crossroads, the canyon provides about an hour of rap n swim pool problems. Near the start of this section is a large overhang sheltering a sandy beach with easy access to higher ground - a good place to bivy.
Shortly after, the first section of extreme narrows begins. Work your way through this section, enjoying the beauty of these deep, dark and heavily sculpted narrows. Strenuous climbing, pack tosses, ingenuity and, as a last resort, drilling and hooking may be required to pass the numerous obstacles. After a few hours, the canyon relents and opens up briefly. A safe bivy can be found by climbing slabs out of the canyon bottom to the left.
Note: it is possible to exit the canyon right at the start of the first section of extreme narrows, and proceed overland to bypass them.
The second extreme narrows section (the Terminal Narrows ) is somewhat shorter, but still takes several hours to traverse. It culminates in a long rappel (80 feet, 25m) to a long pool. At the end of the pool, the canyon jogs left to a large ledge overlooking the North Fork Narrows . Rappel 140 feet (43m) to the river. Hike out to the Temple of Sinawava (about 2 hours).
Imlay Canyon Sneak Route
Imlay is commonly done in a day using the Sneak Route . Starting from the Main Canyon , the sneak route cuts between the West Rim and Pt 6630 (no elevation marked on the Zion Park Map) and enters Imlay at The Crossroads. The extreme narrows start about an hour downcanyon. By sneaking into Imlay, the very best parts can be experienced in a long but reasonable day.
The Sneak also makes a nice, casual overnight trip. A bivy can be found out of the watercourse before swimming, thus with all gear dry.
From the Grotto Picnic Area, ascend the West Rim Trail to Scout Lookout. Follow the trail left along the ridge, then down the end to a small bridge crossing a branch of Telephone canyon. Continue along the trail 15 minutes until a clear route can be seen down into Telephone canyon and up rock on the other side. Cross the canyon and proceed north, staying on the slickrock left of the canyon bottom until forced into the canyon. Thrash up the canyon to a pass.
Descend the other side. A steep section is bypassed by steep dirt on the left, and the sidecanyon soon leads into the main Imlay canyon. Head downcanyon (right), suiting up at the first pool. Follow the description from The Crossroads down.