Third-day road log, from Living Desert State Park turnoff at US 285, north to Brantley Dam and Lake McMillan, through Artesia, Lake Arthur, Hagerman, Dexter and ending at Bottomless Lakes State Park
— Lewis Land and David Love

The third day of the conference focuses on engineering hazards and hydrologic issues associated with gypsum karst processes in the Seven Rivers Formation. The trip begins with an excursion through Happy Valley west of Carlsbad, to the intersection with US 285 (see supplemental log for directions), and proceeds north to the dam site of old Lake McMillan. This reservoir, the predecessor to Brantley Lake, was constructed in 1893, and was plagued with leakage problems caused by sinkhole formation in the lake bed almost from its inception, since it was built on the evaporite facies of the Seven Rivers Formation. Stop 1 provides a view of the old reservoir and dam, which was breached in 1991 and the water allowed to flow into the new Brantley Reservoir. A visit to stop 2 requires the use of high-clearance vehicles, which will ascend the back side of the McMillan Escarpment for an overview of the reservoir and impressive exposures of mass wasting and gypsum fissures along the steep eastern margin of the Lake. From here, the trip proceeds back to US 285 and north across the Roswell Artesian Basin, the primary source of irrigation and drinking water for farming communities in the lower Pecos Valley. The Seven Rivers gypsum serves as a leaky confining unit for the karstic San Andres limestone, the principal source of groundwater in the Artesian Aquifer. The final three stops of the Field Conference will examine spectacular examples of gypsum cenotes at Bottomless Lakes State Park, east of Roswell, where they occupy the discharge end of the regional hydrologic system in the Artesian Basin.