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They have a lot in common: road cone villages, signs, fencing, machinery and orange-clad people. But appearances can deceive: each SCIRT work site has its own challenges and differences.

Two parallel streets in St Albans are a good example: Rutland Street and Browns Road, both contracted by SCIRT to MacDow Fletcher, with subcontractors Rockhard Civil and Drainage on Rutland Street and Brian Perry on Browns Road.

• Both projects involve replacing the damaged wastewater pipeline in the middle of each street and laterals, or side-pipes, to each house.

• Both streets are closed to through traffic to varying degrees, for different periods.
• Rutland Street work, from Innes Road to Westminster Street, started at the end of April and will take about three months. Browns Road work began mid-May and will take four months.
• Ground material is similarly mixed in each street - puggy, clay soils as well as gravelly, river channel-type soils. But due to a stream at the southern end of Rutland Street, work at that end requires dewatering pumps to lower groundwater levels in the trench.
• Manholes need to be replaced on each street and geotextile cloth laid around pipes to keep out any future liquefaction. Backfill material around the pipes is also wrapped in the cloth to stop it moving in future.
• Both project teams have to work with the businesses, schools and people who live around their work sites. On Rutland Street this includes a physiotherapy clinic, St Albans Catholic School and businesses like the thriving Meshino café. Browns Road has to be staged to accommodate the requirements of a big retirement home and hospital with essential access and services.

So you might be wondering why the pipe-work on Browns Road is taking longer to lay than Rutland Street?

Mainly because Browns Road is getting not one but two pipes replaced at the same time – each separately backfilled to protect one from the other. As a result the trench on Browns Road is deeper - three metres compared to two metres or less on Rutland Street, involving significantly more works.

More importantly, whereas the Rutland Street pipe carries wastewater for the street it services, Browns Road’s two pipes service that street plus a much wider Papanui catchment to Innes and Papanui Roads.

Residents and ratepayers can be reassured that the new pipes in their streets, wherever they live, are being designed and built to keep working despite future underground movements. Keeping communication open is also important: SCIRT thanks residents who have made changes to minimise hassles while work crews are in their streets.

Click here for more details on Browns Road, McDougall Avenue, Innes Road work.

Click here for information on the Rutland Street work.  

Rutland Street, St Albans: de-watering tanks contain groundwater pumped from trenches where the wastewater pipe is being replaced.

 

Browns Road, St Albans: manholes waiting to be placed in the ground.

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It’s not every day an adult jumps in the river before the children, but for Downer Construction’s  Environmental Co-ordinator David Maucor, it’s all in a day’s work.

David is helping maintain the Avon River/Otakaro’s water quality while his Downer colleagues place a pipeline under the river bed. That means he regularly wears waders to work and thinks nothing of getting in the river to show a group of visiting school pupils what happens on the riverbed.

The old wastewater pipe or syphon under the river on Park Terrace,  bordering Hagley Park, sheared apart during the February 2011 earthquake. Downer, part of SCIRT, has the job of replacing the syphon with a new 180mm diameter PVC (plastic) pipe, protected inside a bigger steel pipe. But it has to do this without releasing mud or silt into the river. This would be disastrous for the trout which spawn near the loop around Christ’s College on a shingly area of riverbed.

Cathedral Grammar year eight pupils, who go to school nearby,  visited the site in early June  to find out how SCIRT and Downer is managing the project to protect the water quality and the fish life.

David explains that the Downer team are three weeks into the work with at least another three weeks to go.  Work involves installing sheet piles to create a trench to work within and dewatering the trench area by pumping out water.  The pumped water is allowed to settle in in a sediment tank before it is returned to the river.  The site is also double-fenced using geotextile fabric to contain any muddy water, and downstream there is a containment boom as a backstop.

David regularly samples the river water upstream and downstream of the syphon site in keeping with the resource consent from Environment Canterbury, which has been involved from the start. To date the downstream water samples have matched the upstream samples, good for fish life.

The students are particularly interested in the macro-invertebrates – tiny insects and snails - living under the river’s rocks. They quickly work out why a layer of silt would prevent any hatching trout find invertebrate food.

The new syphon will take all the wastewater generated by the Botanic Gardens, public toilets and from events in the Hagley Park dome, to the main pipe on Park Terrace for disposal at the Treatment Plant.

What is a syphon?
A syphon (also spelled siphon) is a tube which moves water from a reservoir to another place. Syphons  can raise water over a barrier, which is what makes them so useful. There is evidence that ancient cultures were familiar with the basic principle of the syphon. Typically, a syphon is a flexible tube, bent into a u-shape, although a rigid pipe can also be used. One end is inserted into a reservoir  or water-filled container, and the other end is inserted into a container to catch the liquid, or left hanging to drain away. Once the syphon has been started with a priming pump, it will pull liquid out of the reservoir until it is removed or the reservoir is drained.

Click here for more details about this project

David Maucor, Downer Construction’s Environmental Co-ordinator, shows students why the Avon riverbed contains important habitat for trout and other aquatic species.

 

The Hagley Park work site for the new syphon taking wastewater from the Botanic Gardens and events area to the main wastewater pipe on Park Terrace. Note geotextile sediment fencing in the foreground around the sheet piling area.

 

Stuart McCarron, Downer Site Engineer, demonstrates a model of a syphon to visiting school pupils to the Hagley Park work site.

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The rebuild of two smaller Huntsbury reservoirs, replacing one large one, on Huntsbury Avenue, is advancing.

The first part of the reservoir rebuild, a new pump station and 6,000 cubic metres of water storage, was completed and operational at the end of last year.  The next part will add a further 7,000 cubic metres of capacity, helping to protect the supply of fresh water for hill residents.

Fulton Hogan, working as part of the Stronger Christchurch Infrastructure Rebuild Team (SCIRT), is making good progress and expects this stage to be finished mid June.

Before the second reservoir is rebuilt, a section of the old reservoir needs to be demolished. This will become a grassed area in the final plan. In the interim this central space will allow machines access for the second reservoir rebuild.

The new reservoir will use the existing wall and ceiling, reducing the need for materials. Waste concrete and materials will be recycled and landscaping along Huntsbury Avenue will be reinstated.

For more information read our update newsletter about this project.

The demolition work, prior to the rebuild of the second reservoir, is expected to be completed by mid June.

The first cuts into the Huntsbury reservoir. Inside the reservoir Fulton Hogan has built stabilisation walls to allow deconstruction of the unused structure.

 
The roof and wall sections are taken out by using an excavator with a demolition jaw. All material from the Huntsbury demolition site will be recycled.