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CHRISTCHURCH REBUILD: WASTEWATER WOES REDRESSED

Following the Christchurch earthquakes many essential services normally taken for granted were out of action. Christchurch’s wastewater system was particularly badly affected with a third of its network damaged and requiring repair.

Not only was the damage to the wastewater system a massive inconvenience for local residents, who were left without basic sanitary services, but it also posed serious environmental and public health risks.

To mitigate the health risks, in the immediate aftermath of the earthquake 35,000 chemical toilets were deployed throughout Christchurch, along with over 500 chemical disposal holding tanks. Some of the tanks remained in place for three years while repairs were carried out on the wastewater system. Intergroup was responsible for the routine cleaning and ultimate removal of the chemical holding tanks.

When the rebuild commenced, we were involved in the massive task of assessing and unblocking the wastewater and stormwater networks.

Christchurch Mayor Lianne Dalziel helps the InterGroup team remove the last of the chemical disposal tanks installed in Christchurch after the February 2011 earthquake. (Photograph from The Press, 29 January 2014.)

Christchurch Mayor Lianne Dalziel helps the InterGroup team remove the last of the chemical disposal tanks installed in Christchurch after the February 2011 earthquake. (Photograph from The Press, 29 January 2014.)

Extensive Damage to the Wastewater Network demanded prompt response

The Christchurch earthquakes damaged approximately 528 km of the sewer system, which amounts to 31% of the total network. As well as breakages in the lines, silt infiltration caused blockages that needed to be cleared. As a first response the Council deployed 35,000 chemical toilets and 587 chemical disposal holding tanks throughout Christchurch’s affected areas. Each tank holds 1,000 litres of waste.

Intergroup cleaned the tanks weekly using vacuum trucks. The protection of public health was of paramount concern because of the risks associated with handling raw sewage. As parts of the wastewater network were restored we were able to progressivley remove the tanks, with the last tank uplifted at the end of January 2014.

Intergroup’s CCTV units provide detailed information and are capable of inspecting pipelines from 50mm to 2m diameter.

Intergroup’s CCTV units provide detailed information and are capable of inspecting pipelines from 50mm to 2m diameter.

Rebuilding the Network

The Stronger Christchurch Infrastructure Rebuild Team (SCIRT) is tasked with rebuilding the roads, water, wastewater and stormwater networks in Christchurch that suffered significant earthquake damage. To understand the extent of the damage, SCIRT commissioned contractors to inspect Christchurch’s 1,700 km sewer system for damage and blockages, using CCTV cameras. To get the CCTV cameras through the network, any blockages encountered also needed to be cleared.

Intergroup was part of the team of contractors who undertook the CCTV inspection and blockage clearing work. The Christchurch wastewater and stormwater network assessment was the largest CCTV operation of its kind in New Zealand’s history. Intergroup inspected and cleared blockages from approximately 60 km of network of pipes ranging in size from 100mm to 2.0m.

Intergroup’s CCTV units provide detailed information and are capable of inspecting pipelines from 50mm to 2m diameter.

Intergroup’s CCTV units provide detailed information and are capable of inspecting pipelines from 50mm to 2m diameter.

Intergroup has more than 30 years’ specialist experience in CCTV pipeline inspection and condition assessment. Because of the urgent need to complete the network repair work, we used extra resources from around New Zealand to expedite the assessment work. We deployed five CCTV main line setups that worked over a 24/7 period.

Our operators worked to produce the CCTV footage and written reports required to enable the designers and engineers to plan and implement the network rebuild. We used experienced operators who were given additional training to deal with the specific challenges raised by the earthquake damage and SCIRT’s special requirements.

The wastewater and stormwater network is located primarily under roads so our work needed to be carefully managed to ensure traffic and pedestrian safety and minimum disruption to traffic flows. In the early part of the work, traffic management resources in Christchurch were under heavy pressure due to the number of damaged roads. We put our own traffic management set up in place for the network assessment work and were successful in keeping the travelling public safe with no traffic incidents or accidents.

Helping Rebuild Christchurch

Intergroup is proud of its work on the Christchurch rebuild. As part of the Christchurch community, Intergroup is on hand not only to assist with the rebuild projects but also to provide innovative and immediate solutions to the numerous challenges faced during the rebuild. Intergroup is well known in Christchurch for being able to react quickly to various situations. For example:

  • Intergroup was recently called upon to assist in helping break out concrete mistakenly poured around four steel beams on a bridge building project. We sent our ultra high-pressure hydro-demolition team to the rescue and, as a consequence, the bridge opening was not delayed.
  • Intergroup is recognised as the market leader in the area of liquefaction. Recognising residual liquefaction silt as a significant problem for Christchurch residents, Intergroup has applied a ‘Dry Process’ high velocity extraction solution. This innovative process avoids introducing excessive amounts of additional water, is not intrusive and consequently house occupants do not need to move out during the removal activities.

We pull out all stops for our clients by doing whatever we can to call on our resources and experience to meet our clients’ needs. If a client calls at 2am and needs a vacuum truck to help stop wastewater overflow, we will endeavor to have resource onsite within an hour. If a customer calls because their regular contractor has let them down, we will endeavor to re-organise our workload to fill that gap. Our Christchurch rebuild work is not always predictable and we strive to remain flexible and responsive to our clients’ requirements.