CES was contacted by an Austin area developer to explore the cost-effectiveness of various wastewater service options to serve the first phase of a large development being planned east of Austin, and for which centralized wastewater service was not yet available.  The first phase of the planned project consisted of approximately 500 homes.  CES conducted soils evaluations in areas of the property identified as available for use as final effluent dispersal fields.  It was determined that there were sufficient depths of soils of suitable types in this area of the property to propose use of this area for subsurface dispersal fields.

The City of Austin’s Water & Wastewater Utility agreed to consider managing the wastewater system constructed for the development if the system was designed and constructed so as to conform to City standards.  Meetings were held by the developer and CES with state regulatory staff and with City of Austin Water & Wastewater Utility staff to (1) identify acceptable collection, treatment and dispersal options for the decentralized wastewater service approach; (2) to discuss design and construction methods, materials and associated costs for an effluent collection system with an effluent lift station that would pump the effluent to a City lift station; and (3) to discuss costs for the various wastewater service approaches, including the construction of a traditional raw wastewater gravity collection system for the development.  To help with these discussions, CES prepared standard details that could be used for the principal components of the effluent collection system, and decentralized treatment and dispersal option.

CES prepared preliminary cost estimates for a large-scale decentralized wastewater system, including long-term operation and maintenance costs.  This system consisted of primary treatment tanks at each residence, with an effluent collection system leading to the final subsurface dispersal area, where final treatment and dispersal of the effluent would be provided.  An alternate approach included the same type of gravity effluent collection system, but with an effluent lift station to pump the primary treated effluent to an existing City-owned wastewater lift station.  Additional tankage was included in this approach in order to avoid overloading the City lift station, and to dose effluent to the lift station throughout the day and reduce loads during high flow periods.  Of the three principle options considered, it was determined that an effluent collection system with a lift station to transfer effluent to the City for final treatment and discharge at a municipal treatment plant would be the least costly option.

CES works with builders and developers to reach win-win solutions for wastewater service approaches in cooperation with local utilities that may be in the best position to manage these systems.  Designing and constructing the least costly form of wastewater service means considering long-term costs and management issues as well as initial capital costs.  Most utilities are reluctant to agree to take over the management of systems if they have concerns about excessive operation, maintenance and replacement costs and problems over time.  CES assists builders and developers with identifying and evaluating technical and management options that can offer reliable long-term wastewater service for their projects.