Thermal Hydrological Mechanical Modeling of Stockton University Reservoir Cooling System

Abstract

Shallow aquifer water (30+ m depth) has been used for seasonal cooling of buildings at Stockton University, New Jersey, in an open loop system. High dissolved oxygen levels in a (semi-)confined aquifer led to iron hydroxide precipitation in wells after several years of operation resulting in the eventual failure and shutdown of the open loop system. Thermal-hydrological-mechanical modeling of the system indicates some shear failure in unconsolidated sands in the aquifer in normal operation, but no failure of presumed clay layer seals of the aquifer. THM modeling of an over capacity operation of the system, results in some non-linear shearing of the clay layer seal adjacent to well bore sand pack, but no significant increase in seal layer permeability. It is not clear whether pumping at very high rates during the initial system installation phase caused breach of the clay layer seal or if seals were missing due to variation of local geologic bedding. Dissolved oxygen measured before system construction at approximately 2/3 of the atmospheric equilibrium value suggest the possibility of incomplete clay layer seals, with mixing of oxidized water from the overlying unconfined aquifer.