NOTE 1/8/2024: The stone at published coordinates has become almost unreadable due to weathering and vines. I have provided information in the description so that you are able to find the information needed for diameter and area. You will still need to visit Stage 1 (published coordinates) to obtain the required info about the fence company. Long Fence is not the answer.
The dam you see at GZ was built in 1881. It is constructed of 20376 large rectangular stones, each stone averaging one perch.. The stones came from Beaver Dam Quarry, not too far north of the reservior area. The reservoir water area created by the original dam was 252 acres. The original tunnel that brought water from the reservoir to Lake Montebello and Lake Clifton (in Baltimore City) was 7 miles long and 12 feet in diameter .
More information about the stone at published coordinates here.
The larger dam upstream was built between 1912 and 1914, and upgraded 2002 to 2005.
To obtain the final coordinates for this cache, you must find your way to the posted coordinates and find the following information:
AA = Diameter of tunnel (number)
BBB = Water area in acres (number)
CCC = Name of the fence company that constructed the black fence around the stone (3 words, no spaces) You can try to get this from your couch, but it is doubtful you will be successful. The answer is NOT Long Fence, which is only two words anyway. Even at published coordinates, you will need a keen eye to spot the answer. No need to do anything the least bit risky to get the answer.
Put this information in Certitude thusly: AA*BBB*CCC
You will receive the final coordinates and some helpful information about the hide.
There may be broken glass, thorns, and/or poison ivy in the area around final GZ. Please be careful when searching.
Congrats to Team Gilligan for being the First To Find!
Certitude added 10/02/2021.
You can validate your puzzle solution with certitude.