To determine the cache location, solve the following:
Go down 88.67 feet with group N. Length limit = QR'. Rest for minimum ST' to meet group H.
Then go down 72.75 feet. Residual time is a two-digit number, add each digit to get U. Add new length limit to first to get VW.
Tomorrow, go down with Group H for 19', the maximum distance is XY. The minimum rest to meet Group G is Z'.
Cache is located at N40-QR.STU, W74-VW.XYZ. Check your solutions at: Geocheck.org.
The cache container is an ammo can hidden in a typical fashion off a branch of the D&R Canal State Park System.
Congratulations to jeffa62 for being the FTF. Thanks to ymaike and non-cachers for proofing the puzzle, and thanks to mblatch for noticing the puzzle solution wasn't passing Geocheck (a puzzle typo was mine, now corrected). An encrypted clue is offered below and more help is available via e-mail.