Canterbury-Mildred Emergency Utility Repair Preliminary Engineering

Canterbury and Mildred Streets in East Austin were experiencing severe pavement and subgrade subsidence and failure, resulting in water main ruptures, traffic restrictions on unfailed pavement, and closed pavement sections. The City of Austin selected Halff to design pavement and storm drain remediation and water and wastewater improvements and Jay Reese Contractors to construct the repairs under emergency conditions.

The water/wastewater improvement designs, drawings and specifications were approved by Austin Water’s senior staff under emergency approval authorization. The water system improvements included 1,500 feet of 6- and 8-inch ductile iron pipe (all restrained joints), 4 new fire hydrants, 11 new water service connections and 6 concrete thrust blocks connected to the existing aged water system. The wastewater system improvements included 400 feet of 6- and 8-inch PVC collector pipe, and 8 new manholes. The high silt content in the subgrade required Halff to design geogrids in the W/WW trench bottoms to stabilize the pipes from vertical movement, while wrapping the pipe bedding with geofabric to prevent silt migration into the bedding voids.

Halff design staff worked closely with Austin Water staff to fit the proposed W/WW improvements within the field constraints of existing aged systems within a residential neighborhood setting. Halff also worked closely with the Contractor to prepare constructable designs, because the Contractor was constructing the improvements as Halff was designing them under emergency conditions. Halff prepared design revisions to address construction constraints as they were encountered, including development of vibration monitoring and mitigation specifications.