Christchurch Collapsed Brick Barrel Stormwater Repair

The Antigua Burke Stormwater rebuild project, undertaken by Stronger Christchurch Infrastructure Rebuild Team (SCIRT) as part of EQ repair for Christchurch City Council, included a section of brick barrel pipe with several unusual features. These provided significant challenges for asset investigation and design, prompting a variety of uncommon techniques for investigation, repair and rebuild, and several changes of direction as the investigation and design proceeded.

The unusual features and challenges included: 

• Existing pipe is a brick barrel material, of unknown age and with no ’as built’ records 
• Pipe running diagonally on private property between and very near to, two residential houses 
• Pipe is curvilinear between manholes, the initial GIS recorded alignment was wrong, difficulty surveying the true alignment, and no line of sight for inspections 
• Pipe is 50 percent collapsed next to one of the houses with reasonably heavy internal debris 
• This collapse pre-existed the recent earthquakes and was practically unaffected by the earthquakes

As well as providing historic background from CCTV records this paper will outline the various cleaning and inspection techniques considered, those applied, and their results. 

This paper will also outline the twisted path of the design process, with assessments of costs, risks and differing hydraulic performance implications given to options (and sub options) as diverse as: 

• Large scale realignment away from private land 
• Dig and replace on private land from manhole to manhole 
• Lining though the pipe (supporting but not restoring the collapsed area) 
• Dig and replace with partial realignment to road reserve, some dig and replace on private land but including installation of a new connecting manhole breaking into the brick pipe (the selected option) 
• Pipe lining specialists and construction team input used to help assess the constructability and construction risks of each option and the landowner views and input will also be described. 

The project was constructed in May/August 2013. 

Construction team feedback on constructability of the final design is also included.