BDD,you mentioned that this property was once a farm.Before digging,did you do a property records search,ie,tax records,to determine past ownership,what type of farm,and if there was a house,barn,or other outbuildings located at this site? It would provide insight into the purpose of the pipe system you uncovered.Also researching past ownership would be a way to determine if any of the past owners had the assets to bury a cache of diamonds,gold,and silver and THEN,leave it buried and forgotten.
For example:There is a written record of C Wickiliffe Yulee,15 yo son of David Levy Yulee and CSA Lt John S Purviance burying part of the gold from the CSA treasury that CSA President Davis had shipped to Yulee's Cottonwood Plantation in Archer,Florida.
The account mentions it was in a truck,and buried in a certain outbuilding.
Mavy holes have been dug at Cottonwood,but that trunk was never found,since that outbuilding has been long gone.
Was it recovered by Yulee's son or Purviance,or is it still there?