As the prime consultant, CobbFendley provided professional engineering services for this CIP project for the GBRA outside of New Braunfels, Texas in Guadalupe County. The project included the design and installation of 28,600 linear feet of 18-, 21-, 24-, 27-, and 30-inch gravity mains, 15,500 linear feet of dual 18-inch force mains, a phased lift station with near-term capacity of 6.54 MGD and future 11.91 MGD, and easement acquisition for 38 parcels. CobbFendley coordinated with over 65 property owners for easements to design and construct the wastewater improvements.
CobbFendley provided preliminary engineering to calculate the size of the gravity collection system, lift station, and force main. The project area is under development and flows range significantly between the low-flow startup period and the ultimate build-out. CobbFendley considered the size and slope of the gravity main to provide a design that will accommodate the range of flows. The lift station is sized to provide pumps in the initial phase with variable frequency drives (VFDs) to accommodate a range of flows, and to allow for upsizing of the pumps as the flows increase. Additionally, the force mains were designed as a single 18-inch force main to provide minimum velocities during the initial low-flow condition and acquired additional easements for future 24-inch force mains to accommodate the higher flows anticipated at build-out. The design of the gravity interceptor also considers potential future interceptors that could serve potential future development to provide a main interceptor deep enough to provide gravity service. Several design considerations added to the complexity of this project including an owner preference for a maximum 20-foot depth of line and coordination with the crossing of the deep 60-inch diameter Vista Ridge Raw Water line in several locations. Additionally, our team designed the cast-in-place (caisson) 16-foot diameter wet well, 45 feet deep with an adjacent valve assembly slab. A crane foundation was needed for the jib crane to lift the equipment into and out of the well. CobbFendley designed generator pads, transformer pads, and the concrete masonry building which was supported on piers to house the mechanical equipment.