The Tustin Branch trail runs along the former route of a Southern Pacific line that moved oranges from the Tustin Packing House to market. The right-of-way was finally abandoned in 1969 when the crossing at Santiago Creek washed out. In the late 90s and then in the late 00s the Tustin Branch/Esplanade Trail was developed, providing a landscaped walking/cycling path where the rails used to be.
The cache is a medium sized plastic lock & lock (originally a round tin), just a few steps off the trail. Trail hours from March-October are 7am-9pm; hours from November-February are 7am-6pm.
5/16/20 update: container is a bit smaller now, tucked further under the bush and under a smaller rock. See the image gallery for a spoiler picture.