Wastewater Rehabilitation in a NIMBY Environment: The Lake Arlington Wastewater Interceptor

This paper presents the case history of a wastewater main infrastructure rehabilitation project with a challenging set of location parameters to overcome. The challenge presented by this project is how to rehabilitate an existing 50-year old clay wastewater main located in a utility easement traversing established, residential backyards. The location of this main is adjacent and along the shore of the domestic water supply lake where access to all the manholes is restricted from vehicle access. The condition assessment for the approximately 14,600 linear feet of a 33-inch, 30-inch and 24-inch trunk wastewater main indicated serious infiltration ground water leakage into the manholes and clay pipe joints - including root intrusion in certain sections of the main. This infiltration increased in direct response to operating water levels of the domestic water supply lake. Thirty-six residential service laterals were also directly connected to the main which were leaking and also had severe root intrusion. The project contained a total of 40 manholes which were located in developed residential backyards with landscaped amenities including swimming pools, landscaped beds, tennis courts, fencing, boathouses and ramps adjacent to a domestic water supply reservoir with no vehicular access. The Trenchless Cured in Place Pipe ("CIPP") Technology process is performed from access provided by existing manholes along the sewer alignment. The location of the manholes range from actually submersed in the domestic water supply lake to the high bank making the location of the existing manholes problematic for the application of CIPP trenchless technology due to weight and size of the vehicle required to transport the rehabilitation material to the manhole access. The transportation weight of CIPP is in excess of a fully loaded 8 cubic yard cement mixer vehicle. There were many challenges faced during this rehabilitation project. In addition to the location and access issues, the City of Arlington Mayor lived across the street from the first insertion site on the project which added to the difficult location issues. Thirty-six residential laterals needed to be excavated and disconnected before beginning the rehabilitation; then reconnected after rehabilitation. The issues associated with the routing and operation of the wastewater by-pass pumps and pipelines in private backyards adjacent to high bank of the potable domestic water supply were also addressed in this project. The project also addressed the need for by-pass pumping of fifteen wastewater mains in utility easements that were connected to this existing wastewater main in need of rehabilitation. Rehabilitation of the wastewater main was required to reduce the infiltration and restore original flow capacity. This paper will present innovative design solutions on how these rehabilitation issues were solved, details on how the City of Arlington addressed the concerns of residents, and how this project was managed - including the use of innovative A+B bidding - resulting in the completion of this project ahead of schedule and within budget.