Active Authentic Christchurch Centre

I've been highly critical of the planning that led to the Christchurch we know was built before the earthquake. And I was also critical of some of the planning for the CBD post-earthquake.

In particular I could not believe the institutional silence around previous earthquakes that knocked the Cathedral spire down. However. Now that we are where we are, I now believe that New Zealand has a duty to protect as much as possible of the Cathedral from further demolition and from future earthquakes.

The rhetoric is compelling: the city is Christ Church, the centre of Christ Church is Cathedral Square, Christ Church is internationally known as the Cathedral City. There is massive value and history attached to this place and the icon that is the iconic church at the centre.

There are famous cathedrals and churches in Cologne, Coventry and Kobe - still standing, or rebuilt, iconic heritage, memories enshrined. Proudly. At a cost. A heritage cost. An investment.

Canterbury Cathedral has similar status for New Zealand now. Yes it is vulnerable and the Church of England can't pay the amount needed to protect it. But it is essential for the future of Christchurch that the church that remains - remain standing. It is precious for the economic future of Christchurch, as it is for the city's cultural future and its heritage. What better place to remember where the city came from, and to remember the earthquake itself. This has to be a Government responsibility and priority.

Which brings me to the 4 Avenues area of the old central business district. What to do, now that 800 or so buildings have been or are being demolished. I read the Listener magazine piece by Bob Jones, and agree with amalgamation of sites idea. Not sure about a lot of water spaces in there.

But it is clear that the market will not rush into building commercial buildings now in this part of Christchurch. A lot of money has already gone - to Auckland and other parts of New Zealand - and many businesses have relocated to other commercial hubs in other parts of Christchurch where there is some critical mass, and where there is infrastructure they can connect into.

I did entertain the idea of relocating Jade Stadium and QEII into the central business area. I was thinking, well, if both of these amenities are to be built, why not locate them in the centre - given all the available land. (I don't think it is appropriate to rebuild QEII at Burwood. This land is too compromised.)

But. Stadiums are very expensive things as we know, and we look at what's happening in Dunedin right now. The Super 15 games that have been playing in the Christchurch temporary rugby facility have had a great buzz about them. Recessions are not good times to rebuild the sort of stadium that Jade was - ie very big - very imposing, takes up a lot of space, and hardly gets used. Doesn't do a lot to activate an urban environment either.

But that's not the same with a multi-purpose athletic and swimming facility. It can integrate much better into an urban fabric, and be used as an anchor for a different sort of Christchurch centre....

I see Christchurch as the centre of a remarkable industry that is New Zealand's own. It's the outdoor pursuit, physical fitness, extreme sport capital of the world. It also offers the best place to chill, get organised, and equipped, for all those fantastic activitities that New Zealand is increasingly known for in Australia and further afield: Great Walks, cycling expeditions, mountaineering, ski-ing, tri-athlons, elite sport events, canoe-events, rafting...

The South Island has other centres, but they are constrained in their accommodation offerings, and do not offer the space that Christchurch now has to be the active life-style support city for the South Island.

Christchurch needs to be able live this lifestyle itself. Putting an upgraded QEII facility in the centre provides a new magnet, and new organising force for transport: cycling becomes much more dominant and rational. So does the related infrastructure. So does walking. And the sorts of businesses that would co-locate will be tourism, event and support services - event management, clothing, gear, and even manufacturers that specialise in elite sport equipment.

Well. That's what I think aanyway.

Banks Peninsula Rising II

This video clip animation (which is silent by the way) made by GeoNet NZ is a helpful illustration of the way the New Zealand land mass has been formed between the interaction or collision between the Pacific Plate and the Indian Australian Plate. It's all interesting but what is especially interesting for the South Island is that the Southern Alps were formed by the two plates rubbing together and forcing the edges to buckle and bend and form the huge upthrusts that are now the Southern Alps.

This graphic shows the situation today. What is of particular interest is the fact that the Pacific Plate is "subducting" under the Indian Australian Plate to the north of New Zealand. ie it is diving under it. The arrow heads show where that is happening. But along the Southern Alps the edge of the Pacific Plate is apparently sliding along the edge of the Indian Australian Plate.

This difference in interaction is further illustrated in this graphic. The transverse movement/fault known as a "strike slip region" it appears. Even though the Plates are sliding along each other in the South Island, along the Southern Alpine fault, it's not as if this movement is well oiled. Any movement is in huge and violent jerks. Enormous pressures will still be exerted in an East-West direction (because the plates still press together), the edges will bind, causing a shearing stress on the Pacific Plate that lies under the Canterbury Plains. As a result a number of smaller faults have developed from the top of the South Island, parallel to the Southern Alps fault, that run down into the Canterbury Plains.

Some of these smaller fault lines are shown in this recent graphic prepared by NIWA which is now mapping new faultlines. You can just make out other red fault lines under the earthquake dots on the land around in Christchurch. It is movement in these smaller faults that give rise to smaller earthquakes (compared to those released in and by the Southern Alp fault.). But these faultlines are close to the surface and close to a city. So they can be much more destructive than a big distant earthquake.

This is an East/West cross section of Banks Peninsula (looking North). It shows the volcanic rock that formed Banks Peninsula after volcanic activity a million or more years ago. These volcanoes are extinct. The underlying rock is known to be faulted. (You can see the faultlines in the graphic.) This base rock was once flat but has been pushed up out of shape, and it has been squeezed by East-West tectonic plate pressure, and must have been cracked allowing volcanic magma to push through. One scenario is that this underlying rock is folding up slowly now. It may be a weak point in the plate. New faults may be forming. But this is speculation.

Intensive monitoring is the duty of authorities now.

Banks Peninsula Rising

A long time ago I collected rocks. You can probably imagine that. Amateur geologist and all that. And growing up in Oamaru I learned how the East Coast of the South Island had had three distinct areas of volcanic activity in the past: Port Chalmers Dunedin, Cape Wanbrow Oamaru, and Banks Peninsula Christchurch. Interesting that these volcanic outcrops created good places for harbours (I should probably include Moeraki as well by the way). The earthquake sequence and location at Christchurch has got me thinking. Like a lot of people. I look at Banks Peninsula's geology - how different it is from the Canterbury Plains - and wonder if something more fundamental is happening than movement along a few relatively quiet (until recently) fault-lines. What got me thinking this way were these headlines: Port Hills half a metre taller after Christchurch earthquake Reported by Stuff - 2nd March 2011 Christchurch's Port Hills are nearly half a metre taller in places as a result of the colossal forces unleashed by last week's earthquake. Satellite analysis by GNS Science shows the top of the roughly east-west buried fault responsible for the February 22 magnitude-6.3 quake lies between one kilometre and 2km below the southern edge of the Avon-Heathcote Estuary. Land on either side of the fault has slipped horizontally as well as vertically, causing the Port Hills to rise by about 40 centimetres and land just south of the Avon-Heathcote Estuary to shift to the west by a few tens of centimetres. I formed an intuitive view that the volcanic mass of Banks Peninsula was in same way separating itself, or at least moving independently, from the rest of the Canterbury Plains which is the cradle for much of urban Christchurch. So I did a bit of research. First a bit of background from an Encyclopaedia of New Zealand 1996: Banks Peninsula is situated in about the middle of the east coast of the South Island on the margin of the Canterbury Plains. It is approximately 450 sq. miles in area and its highest point is Herbert Peak, 3,014 ft. It comprises two extinct volcanoes which were active less than half a million years ago. Their craters have subsequently been enlarged to many times their original size by stream erosion; they were then invaded by the sea during the postglacial world-wide rise in sea level beginning about 15,000 years ago. They now form the harbours of Lyttelton and Akaroa. Originally Banks Peninsula was an island, but it became tied to the Canterbury Plains at some late stage in geological history when the growing alluvial plain reached its base.... Throughout the European history of Christchurch there has been debate as to exactly when the volcanoes happened, and whether the harbours were formed by volcanic action, glacial action or weathering.

This map shows the geology of Banks Peninsula, and highlights the sequence of volcanoes that formed it over time. The Geology of Banks Peninsula, By R Speight, which was read in October 6 1942, at the Canterbury Branch of the Royal Society of NZ, cites investigative work done previously by WM Davis – a visiting geologist. His view was that the formation of the cliffs and landform of Banks Peninsula is by erosion, not by the formation of the volcanic cones. He asserted that the valleys were cut “when the land was much higher…” He notes that “in very many cases on the East Coast clffs descend into very deep water…” Davis researched wells dug in the area, and was particularly interested in a well dug in Heathcote Valley – in that case solid rock was reached at a depth of 708 feet. Speight writes, “This seems to indicate that the former Heathcote Valley was eroded to that depth, and that the land once stood over 700 feet higher…”

This diagram is a geologic cross section of Banks Peninsula and where it intersects with the Canterbury Plains. In Volcaniclastic Rocks of the Orton-Bradley Formation, Banks Peninsula, a thesis submitted in fulfilment of the requirements of the Degree of Master of Science in Geology in the University of Canterbury by Richard Sutton in 1993, we read: The composition of the Banks Peninsula volcanics correlates well with the hotspot or plume type of intraplate volcanism, usually when a plate moves over a fixed hotspot or plume within the mantle, a linear chain of progressively younger volcanoes forms, such as occurs at Hawaii. This does not appear to have occurred in this case, though here is some evidence of migration of volcanism from Lyttelton to Mt. Herbert to Akaroa.... Banks Peninsula consists of several large coalescing, composite volcanoes, composed predominantly of alkali rocks. Originally an island, the volcanoes were joined to the mainland by the progradation of the Canterbury Plains by deposition of loess and alluvium derived from the erosion of the Southern Alps. Banks Peninsula shows little evidence of deformation in the region. The volcanoes were formed on a pre-existing basement high, formed by the horst and graben structures in the Torlesse rocks, underlying the Canterbury Plains (Sewell et al. 1988).

So what does all that mean? Well what it basically says to me is that the volcanoes that form Banks Peninsula have formed on top of the layer of rock that underlies the Canterbury Plains. The volcanic action spewed up volcanic rock through cracks or fissures in that layer, and formed a pile of volcanic rock now known as Banks Peninsula. This underlying layer of hard rock is part of the crust of the earth that floats above the earth's mantle and molten magma that lies beneath, as depicted in this graphic. Putting all this together, the scenario is that after the volcanic activity that formed Banks Island, there was tremendous downward pressure exerted on the Torlesse rock layer below. Just simply the force of gravity on this new mass of rock - area 450 square miles, average height (now) around 300 metres. This force over time has forced the layer below, which is floating on molten magma, downward. Like a boat floats deeper when more people jump into it. (This accounts for the observations of geologist Davis - above). The underlying rock layer sank till some sort of steady state was reached over time. Or maybe it got jammed. And now we are experiencing a reverse ripple from below. Perhaps the downward movement was too far, too fast, got stuck, geologically speaking, maybe there are additional pressures at work, but what appeared to be in balance is now finding a new level. The underlying rock layer is lifting, floating up.

When you research something like this on Google, it is interesting what comes up. I end with this discovery. In the Journal of Environmental & Engineering Geoscience; November 1995; v. 1; no. 4; p. 427-488, we find a paper: Geology of Christchurch, New Zealand, by L. J. Brown, R. D. Beetham, B. R. Paterson, and J. H. Weeber, of the Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand. Note that this research was published in 1995, 16 years ago. In this we find the following statements:

Christchurch is situated on the east coast of the South Island of New Zealand in the south Pacific Ocean. The city is located at the coast of the Canterbury Plains adjacent to an extinct volcanic complex forming Banks Peninsula. The site of Christchurch was mainly swamp, behind beach dune sand, and estuaries and lagoons, which have now been drained.....

Geological constraints of concern to Christchurch include flooding, variable foundation conditions, slope instability on the Port Hills, and coastal erosion. The Waimakariri River with its catchment in the southern Alps, regularly flooded Christchurch prior to stopbank construction and river realignment, which began shortly after the city was established in 1850. Variable foundation conditions as a consequence of a high water table and lateral changes from river floodplain, swamp, and estuarine-lagoonal environments, impose constraints on building design and construction....

The geology, tectonic setting, and active seismicity of the Christchurch area indicate that future large earthquakes will occur which will have major impact on the city. Earthquakes are expected to produce liquefaction, landsliding, ground cracking, and tsunami. Planning and design to mitigate the consequences of these phenomena are an essential prerequisite for preparedness....

The identification and quantifying of geological hazards, and the implementation of regulation and planning designed to discourage irresponsible land use, should continue in the future as the geological knowledge and database is expanded....

Which is all news to me. Though it clearly wasn't to some people in 1996.

How Strong was the Christchurch Earthquake?

I had to go to Timaru over the weekend to spend time with my elderly mum. Stopped in at Christchurch on the way, and had time to jump on a bike and pedal around exploring... This is the Merivale Shopping Centre in Papanui Road. Looks quite normal from a distance... But shops on both sides of the road are fenced off. You can see in this Deli window: buns, rolls and other delicacies - laid out exactly as they were on the day of the earthquake. And it's a no-go shop. Behind wire fences. And if you look in the reflection of the window, you can see across the street... Across the street this whole frontage has gone. The bricks have been tidied away now. Cars drive past. So do pedestrians. And the sign insists "We Are Open..." The insides of the shops and office spaces are open to the elements exactly as they were on the day of the earthquake....

These are boxes of shoes all stacked on shelves - many of them - but the whole brick frontage has gone. And next door another office. Open to View. The force of the earthquake was huge. Walls and materials that were massive (dense and weighty), like brick and stone were literally tossed to one side - while the rest of the building (made of wood, lighter and more resilient material) shook back into place. More or less anyway.

I cycled along the avenues until I came more to the Eastern side of the city, by the Avon. The streets were dusty and deserted. Still a lot of dry sand piled in the streets, blowing. Nobody about. Many red-stickered homes. Few cars. Almost expected a tumble-weed to blow down the street. And yet the sun was out and it was a brilliant day. I came along the street because I saw workers up to their eyeballs in sewage repairs. I can't keep away from sewage systems. In the background is a heritage pumping station. The classic brick shithouse. The orange box is a powerful pump. It's taking all the wastewater from a manhole, and pumping it direct into the Avon flowing behind the trees. Residents may be able to flush their loos - and here I could see where it was actully going. The workers were fixing the manhole, and three broken sewer mains. Here's another view of the site. What is interesting is the angle that the pump station is on. It's actually leaning about 10 degrees toward the river....

Here it is close up. Heritage for sure. In one piece. But knocked right off its foundations. You can get an idea of how much the ground has moved and dipped from where the pump station building has ended up. Underneath it is a 20 foot deep sump into which wastewater used to flow, and then was pumped to other trunk sewers, and hence to Bromley wastewater treatment plant. Now, some sewers run uphill. Others are not existant. and others fractured. You really wonder about the wisdom of repairing a system which is at so much risk of liquifaction, and ground movement next time... The NZ Herald headline after the Japan earthquake shouted: "Japan's earthquake 8000 times more powerful than Christchurch". (That's what you get when compare a 6.3 magnitude earthquake with an 8.9 one. Richter scale.) But this simple sum ignores what happens on land. That calculation is energy/hectare. And that comes down to ground acceleration. At Fukushima, ground acceleration was .35 gravity. Christchurch CDB it was 1.1 gravity. In Heathcote Valley it got up to 2.1 gravity. In the CBD the Christchurch earthquake was 3 times more powerful and destructive than on land in Japan. This is because the Chch epicentre was 4km from the CBD and 5km deep, whereas in Japan the epicentre was 130km offshore and 32 km deep. No Tsunami in Chch of course.

Further along the road the scale of the ground movement is evident with this damage to the road and verge.

Concrete gutter sections and road seal tossed around and swallowed up in cracks as the ground heaved... cracks carved through the ground....

...and into this adjacent graveyard. A sad sight by the road. Likely to be one of the last parts of the garden city to be fixed. As one person said to me, "they're already dead...."

But it is poignant. This granite memorial has stood proudly here for the best part of a century. You can see the cast iron retaining post that was there to stop the column from moving. But the force of the earthquake - particularly the upward acceleration, followed by rapid downward and sideways acceleration would have literally thrown this column skywards, then pulled the base down, away from the column, which then toppled sideways, and broke into pieces. And then, adding insult to that injury, the ground shook further liquifying the sand beneath, which oozed up around the pieces....

And in this part of the cemetery, you can see the marble pages of a memorial, almost as if the winds of time have turned the whole place into a landscape like a beach. Full of memories. But memories which will be erased and covered by the passage of time. Leaving only sand, rippling in the wind....

Garden City’s Cheeky Opportunity

New Zealand’s Garden City has the opportunity to re-invent itself from the bottom up.

I’m talking sewage.

Consider the large amount of clean water that is used to carry even a small quantity of human excreta. With each flush, over 10 litres of clean water goes down the drain. This clean water which is flushed down the toilet goes into a traditional sewage system. We reticulate all sewage solids and wastewater in a big network of ceramic pipes for centralised treatment. The Romans had the idea for that first and it was perfected by the British almost 200 years ago. It’s ancient.

In the absence of government support or massive rates, traditional sewage solutions threaten to bankrupt communities. Especially if sewer networks need to be rebuilt.

Traditional sewage systems are atrociously expensive to build today primarily because of the labour intensive drainage network. Sewage treatment plants themselves are relatively cheap. It’s the thousands of kilometres of pipes that cost seriously big money. And where pipes are laid in ground that moves – forget shakes – cracks open up in the pipes letting rainwater in and causing overflows, and letting sewage out polluting more water — invariably rivers and ponds and beachwater.

For more than a decade – as a Councillor - I have immersed myself in Auckland’s sewage problems, projects and costs. I chaired North Shore City Council’s Works & Environment Committee’s recommendation ten years ago to impose a fixed charge per ratepayer of $500 annually to reduce leaks from the city’s fragile sewer network. We debated the issue at length. I suggested – half in jest – that we’d be better off with old style night-cart collection of excreta, central composting, and recycling back to land. At least we’d know it was being collected, and we’d also know it wouldn’t end up on the beaches.

North Shore City ratepayers have invested close to a billion dollars in its sewage system. And it still leaks. Much of Auckland is built on soft Waitemata clays and sandstone. It’s shifting slowly all the time, cracking the sewer network. The damage is slow but it’s relentless. And so are the repairs and the costs.

Much of Christchurch is built on alluvial gravels and sand. Its sewer networks lie in ditches dug into this substrate which liquefies in even a small earthquake. Given the choice of developing Christchurch today as a greenfield site – subject to earthquakes from time to time - engineers today would surely advise against a ceramic pipe based wastewater network.

Ten years ago the Auditor General concluded that “it is difficult for Thames Coromandel District Council to demonstrate that the sewage reticulation option is indeed the best use of ratepayer’s funds.” That report was part of a long running battle between the majority of Cooks Beach lot owners and a Council determined to fix septic tank problems by imposing a traditional reticulated sewage scheme. I know Christchurch City is not like Cooks Beach.

My interest in sewage alternatives has taken me round the world and times have changed, as Sydney Water found when it investigated developments in the United States and Europe, after facing estimates of between $16,000 and $70,000 per lot to connect houses to new centralised sewage systems.

They found that on site wastewater services are used in 50% of lots in Norway and 25% of all lots in the USA. On-site servicing is no longer seen as a temporary measure in the USA where 35% of new city housing developments are now on-site serviced. Beverley Hills in LA is all on-site, and Barbra Streisand was one who lobbied the council to keep it that way. The US Environmental Protection Agency has advised the US government that “decentralised systems, where properly managed, could protect water quality over the long term and do so at lower cost than conventional systems in many communities.”

The most modern systems used in US urban environments combine sophisticated on-site primary treatment tanks, which retain and biodigest solids and need emptying every ten years or so, and small-gauge leak-proof pipes which reticulate the liquid effluent only, to either a centralised treatment plant, or to small local treatment facilities. Some of these use vacuum systems or small pumps to send effluent through leak-proof plastic pipes which can bend and move with ground movement.

While modern centralised wastewater treatment plants in New Zealand are using cleaner technology, the fact is that traditional sewage reticulation pipe networks are dreadfully leaky, and environmental disasters in themselves. Even without an earthquake.

It is difficult to justify their construction and use in coastal environments if the goal is to protect and preserve water quality in the long term.

It is no longer flush it and forget it in Christchurch. Every day people are faced with the personal challenge of what to do with their own, and their children’s excrement. Call it human bio-solids. Right now a system of Portaloos and regular collection is being rolled out across Christchurch.

The collected bio-solids will contain toilet paper and some sterile urine. But will not be contaminated with heavy metal trade wastes that get tipped into the sewer. It will not be diluted with thousands of litres of water. It will be pure. Ripe for composting and re-use. It can be developed into a modern, resilient and responsible sanitation system.

Christchurch has the opportunity to re-invent itself from the bottom up.