To find the coordinates for this cache, you must complete the Waterfalls of the ELGT Adventure Lab. The journal entries will provide pieces of the bonus cache's coordinates.
Manor Township's section of the Enola Low Grade Trail has some streams/runs that tumble into the Susquehanna River. These aren't mighty waterfalls. Most of them flow into troughs that channel them over the train tracks before the water drops into the river. But they are water features along the trail that change with the seasons. Three of these water features have names (the maps can fight over the spelling and punctuation): Mann's Run, Fisherman Run, and Frey's Run. One is a wonderful wet wide runoff that reminds me of a hanging garden. And one is a water feature where I have seen frogs in the spring.
This Adventure Lab is probably best done by bike as it stretches between about the 1.5 and 4 mile markers on the trail. The bonus cache is near Mann's Run (north end of the locations), so if you are only biking one way, do it from the south. If I were walking it, I'd probably come down from Chestnut Grove and go south and then north. Long walk but there's an AL at Chestnut Grove plus Star Rock.
Congratulations to NoBlueCircles and the little circles on their biking to the fiirst-to-find on this toasty morning.