Lathrop, CA

The SPA 2 WRF and SPA 2 Effluent Storage, Reuse and Recharge System were design/build projects where PACE was the Engineer-of-Record.  The projects include the design of a 1.2 MGD WRF that produces high quality effluent meeting Arizona Title 18 Class A+ Reclaimed Water Standards and the effluent disposal system that incorporates storage, reuse and recharge.  Effluent is to be reused within the Asante Development.

As part of the design, PACE developed an effluent management plan with a water balance analysis that helped to size the 1.3 million gallon effluent storage basin, the 5,600 gpm peak capacity effluent pump station, and the vadose zone recharge wells. The effluent distribution system is phased to allow for expansion as the development grows and to reduce upfront capital and O&M costs. Due to site constraints for future WRF expansion and no authorization to discharge to neighboring waterways, PACE recommended the use of vadose zone wells as an alternative to dispose of effluent and recharge the underlying groundwater aquifer.  In addition to the vadose zone wells, a small percolation basin was also designed to recharge effluent from the ground surface and provide a backup to the vadose zone wells.

Before entering the vadose zone wells, the effluent is further filtered through a 5-micron filtration system and chlorinated.  This lowers the solids loading to the wells and inhibits any microbial formation on the well screening, maximizing the life of the wells.

This system design was accepted by the City; however, due to the recession, the construction of the effluent storage, reuse, and recharge system has not been completed.