Like many municipalities in the U.S., the City of Austin, Texas has for the past few decades been challenged with continuing to provide cost-effective and appropriate infrastructure and services to increasingly spread out suburban and semi-rural areas around the City. Austin is particularly challenged with this because the western half of the City is characterized by very rocky hills, with large portions of the City's service areas overlying the Edwards Aquifer. Sensitive watersheds are scattered throughout the area, with the Lower Colorado River running through the middle of downtown Austin. The City has implemented a variety of land use protection measures and purchased conservation lands or development rights to help prevent adverse impacts to water quality of the Edwards Aquifer and surface waters in the area. The use of conventional gravity wastewater collection systems to the west of the City usually necessitates cutting through massive limestone rock and/or using multiple lift stations to convey sewage to one of the City's municipal wastewater treatment facilities. Further, it was recognized by city planners and politicians that providing conventional wastewater service tends to lead to intense development in areas where there has been an interest in preserving water quality and the natural hill country setting.

In 1994, the City of Austin contracted with CES to assist the City's Water & Wastewater Utility with the identification and evaluation of wastewater options that would be appropriate for use where traditional options were less feasible. The project work was carried out in several phases, due to its comprehensive nature and the need to coordinate the work with other on-going City planning efforts.

As a part of that work, research was conducted on the performance of existing "basic"/standard types of system operating in the rocky hill country conditions. Those systems consisted of only septic tank pretreatment followed by either gravity or low pressure subsurface dispersal.

Following that work, and based on those findings, several demonstration projects were designed, constructed and monitored to study and verify the performance of alternative systems that were thought to be most appropriate for addressing performance shortfalls observed for existing conventional systems in those rocky/hilly conditions. The four demonstration projects included a residential subsurface wetland using sand-lined low-pressure dosed trenches; a subsurface wetland in tandem with a Bioclere trickling filter unit, with recycle constructed at a City treatment facility; and two residential intermittent sand filters followed by low pressure dosing of the treated effluent.