THE NORTHWEST WASTE WATER TREATMENT PLANT was constructed to serve the growing northwest portion of the city and to relieve the Haskell Street Wastewater Treatment Plant in central El Paso. The plant was constructed on a site, which is near Interstate 10 and required substantial site preparation for the construction of the plant. The natural soils were not considered adequate to support the loads from the plant components and the varying soil conditions included rock strata. It was determined that the rock formations were sufficient to create active hydraulic pressures after heavy rainfall events. In order to prevent hydrostatic forces and uplift, the concrete containment tanks had to be designed with self activated valves, in order prevent uplift pressures on the bottom of the tank slabs and hydrostatic pressures on the tank walls. The plant complex included several tank components, a maintenance facility an administration building and required the design of a drainage flume adjacent to the property for diverting a large, high velocity amount of water around the property.