To reach the Mortendad canyon trailhead:
Drive south on Trinity drive and park in a parking lot on the left, just before Trinity meets Pajarito road at a T-intersection. Look for a singletrack that heads east starting from the south end of the parking lot.

Cerro Grande Fire Damage Assessment:
The Mortendad/Eniweetok trail system was badly damaged by the fire, and travel on the trail is not recommended at this time. At least a dozen large trees are down on various sections of the trail, and serious ash/sand deposits from the dry season and fire make the surface off of the trail proper extremely soft - my tires sunk almost a foot when I swerved off in one spot. There is also some significant damage from backburning and bulldozers. The trail is not signed, and is thus probably still legal, but riding it is strongly discouraged until further notice (posted 5/24).

Trail Log:
0.1 The singletrack meets a dirt road. Turn right.
0.4 Look for an unmarked singletrack on the left, and take the furthest lefthand trail.
0.5 Stay right on the singletrack.
1.4 Stay left on the singletrack, and turn right when you come to a dirt road. Follow the dirt road south across a dry creekbed.
1.5 Turn left onto another dirt road, which will slowly turn into singletrack.Stay left at all junctions while on this section of the trail.
2.6 Turn right on a dirt road that follows some powerlines to the west.
2.9 Turn left onto a dirt road that crosses to the other side of the canyon.
3.0 Turn left onto another dirt road and head east again. This road will also turn into singletrack after about 1/3 of a mile.
4.3 Singletrack ends at a dirt road. Either turn right and ride on roads back to LANL, or go back the way you came.