Chirstchurch: Pipelines. Earthquake Concerns on Underground Pipes Wave propagation Permanent ground deformation Liquefaction Can lead to pipe leakage.
Post on 05-Jan-2016
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Chirstchurch: Pipelines
Earthquake Concerns on Underground Pipes
• Wave propagation
• Permanent ground deformation
• Liquefaction
• Can lead to pipe leakage and/or pipe breakage
• Broken sewer pipes near Christchurch are pumping raw sewage into the water leading to the closure of many popular beaches.
• Several cases on gastrointestinal illness reported
• Susceptibility to pipe damage is mainly dependent on the material of the pipe and the earthquakes intensity.
• To a smaller extent factors include nature of surrounding sediments, pipe length and diameter, and amount and type of pipe joints.
Pipe Materials in Response to Earthquakes
• Steel and iron pipes carrying natural gas are prone to leakage or breakage especially at pipe joints and seams.
• Brittle concrete and PVC pipes that carry water or sewage are prone to fracture.
• Flexible high density polyethylene pipes respond best to ground acceleration due to earthquakes.
• Clay pipes make up over 300 km of the sewage and storm-water pipes under Christchurch. Almost all of the pipes inspected thus far were blocked or broken.
Damage
• There was heavy damage to water and sewer pipes. Fifty percent of wastewater system remains working, however significant damage was done to the water treatment plant.
• Sewer pipe leaks and silt blockages are causing raw sewage to flow into the Heathcote and Avon rivers and is expected to continue for months to come.
• The extent of damage to pipelines in Christchurch is still unknown but will continue to mount as infrastructure rebuilders get into the roads to carry out work.
• Even though there were gas leaks there were no major gas fires after the earthquake.
Ocean Outfall Project
• Opened March 24 2010
• Cost: $87.2 million
• 5 km of new pipeline, extending 3 km offshore
• Connects to 150,000 households in Christchurch
What is Ocean Outfall?• Includes new pump at Christchurch Wastewater Treatment Plant
oxidation ponds
• 2.3 km of concrete pipe onshore- dredge and lay
• 2.7 km polyethylene marine pipe into Pegasus Bay- mircotunneling
• Project to replace Avon-Heathcote Estuary due to concerns about marine environments and human heath.
• Discharges treated and disinfected wastewater out at sea
• After inspection the Ocean Outfall project seems to be intact.
• Prior to the earthquake three more ocean outfall projects were expected to take place to deal with wastewater treatment and disposal in Lytellton, Diamond Harbor and Governors Bay.
• Considerations must be made regarding wether or not ocean outfalls are the best strategy for wastewater management in earthquake prone zones.
•
• With increasing migration of peoples to the Christchurch area, large scale land based wastewater treatment plants may not be desirable.
• Ocean outfalls may continue to be the solution for the increasing human waste disposal for this region.
• Therefore planning, construction, and maintenance of new systems should be well discussed and thought out.
Future suggestions • Using pipes of ductile nature.
• Larger diameter pipes fair better.
• Compacting ground before pipe laying.
• Injection of cement to bind sands and gravels.
• Designing simple networks with minimal joints.
• Installing perimeter walls in ground.
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