The trail stays well west of Copper Creek in this area. There are two side streams from the east face of Mt Hutchings which drain into Copper Creek, and the box is where the higher (northern) side stream crosses the trail. An altimeter is the best way to find this box, since a good GPS signal is hard to obtain in the narrow canyon with tall trees and there are seasonal streams in addition to the two streams shown on the 7.5' quad.
(lat,lon) = (36.8298300, -118.5803800) in decimal degrees, NAD83. (zone,east,north) = (11S, 359146.0, 4076962.0) in decimal meters, NAD27.
Map exported from TOPO! software, used with permission.