20
SEPTEMBER-OCTOBER2014
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&
ri
SITE REPORT
The ‘clean’ concreteandbrick rubble is
going to theLytteltonHarbour reclamation
project andother sites, as it requiresonly
minorprocessing, leaving themixed
demolitionmaterial needingmajorprocessing
tobe separated intouseful components.
Consequently,marine reclamation into the
harbourbegan just amonthafter the2011
earthquake.
Hard fill from certified clean sites
hasbeenallowed tobedeposited
here, according to chief executive
PeterDavie, and todatemore
than twomillion tonnesof rubble
has allowedLPC to reclaimover
6.5hectaresof land. “Thishas
savedChristchurchand thewider
Canterbury regionoverNZ$100
million indumping costs,while
also expandingPort infrastructure
to support forecastedgrowth in
containerised cargo,” explainedPeter.With
resource consent for 10hectares, the land
reclamationactivity so farhasprovided
invaluablenew capacity for thePort. Stringent
monitoring controlshavebeen established
to ensure that only clean fill thatmeets strict
criteria isplaced into the reclamationarea.
Ultimately, thepotential for recyclable
demolitionand liquefactionwaste could reach
a total of 4.5million tonnes as adirect result
of the earthquakes, according toCanterbury
EarthquakeRecoveryMinisterGerryBrownlee
andEnvironmentMinisterNickSmith ina
statement issued last July. “NZ$2.5million
(US$2million) isbeingprovided from the
Government’sWasteMinimisationFund to
fund sortingmachinery thatwill separate the
waste into10different products for reuse.
This is the largest ever grant from the fund
reflecting the scaleof the earthquakes’waste
problem,”Nick said.
“There is thepotential to recoverup to1
million tonnesof aggregate, concrete, timber,
metal, plasterboardandplastics from this
initiative.Ourobjective is to recover asmuch
as ispracticalwithout excessivelyadding to the
costsof the earthquake recovery,”he continued.
“Itwill not bepossibleor economic to recycle
all of the earthquakewaste.Any contaminated
waste [isbeing]disposedof at theKateValley
landfill,”Nick said.
The statistics associatedwith the
Christchurchdemolitionprogramme
demonstrate the enormityof the challenge that
has facedCERA from thebeginning.Within
theFourAvenues (which roughlydefine the
CBD) therehavebeen968 full demolitions
and162partial demolitions,managedby
CERAor theCivilDefencebody. Therehave
been further insurer-orowner-managed
demolitions.
RESIDENTAIL CLEARANCE
Aside from theCBD, therehasbeen large
numberof demolitions in the residential red
zone– some5,227dwellingshavingbeen
clearedbyCERAand insurers fromCrown-
ownedproperties in the flat landResidential
RedZone, up to the endofAugust 2014.An
additional 517propertieshavebeen tendered,
awardedand/or scheduled fordemolition/
clearanceby contractorsonbehalf ofCERA.
Of these,CERA reports it has receivedoffers
from interested thirdparties to relocate334
houses, ofwhich221have signeda relocation
agreement, 453properties that havebeen
scheduled for clearance/demolitiononbehalf
of insurers, and insurershavealso receiveda
numberof offers from interested thirdparties
to relocatemorehouses. The total number
ofCrown-ownedpropertiesout to tender,
scheduled for clearanceandactually cleared
amounts to6,197.
There remain133propertieswith expired
Crownoffers topurchase thedomestic
dwellings in the flat land residential red
zone. Someownersprefer togo it aloneand
battle it outwith insurers.Ownersof eligible
ResidentialRedZoneproperties in thePort
Hills, to the east ofChristchurchCity, have
until 27Februarynext year to consider a
Crownoffer topurchase theirproperties and
nooffershaveyet beenmade toownersof
vacant, commercial anduninsuredproperties
in thePortHills, saysCERA.
Anumberof key landmarks in theCBD
await demolition, and reference to theCERA
website (
)
showshow extensive it is.Among them is
thePoliceStation, a13 storeymonolithbuilt
in1973whose fatewas sealed lastApril.A
contract for itsdemolitionwas awarded to
CeresNewZealand, byCERA. Thebuilding is
still undergoingappraisal.
Ceres also recently completed the
demolitionof another famousChristchurch
landmark, the formerMillersdepartment store
andCivicbuilding, toprepare the site for the
city’snewNZ$53million (US$43million) bus
interchange. “Thebuildingwas first stripped
out back toa concrete shell prior todemolition.
All the exterior leadpaintwas stripped from
thebuildingandasbestoswas removed from
all floors,” explainedDavidLeonard,Ceres’
director.
Christchurchhas seen somepioneering
solutions todemolition. Take, for example,
theClarendon tower, an18-storey reinforced
concrete framebuildingdesignedand
constructed in the late1980s. Itwasdeemed to
be sodangerous that it had tobe strengthened
before considered safe fordismantling. The
workwasdesignedbyDunningThornton
ofWellingtonandOpus International of
Christchurch.AlistairCattanach, director
of the former, explained: “During the
earthquakes, thebuilding suffered sufficient
damage for it tobedeemedahazardand
demolitionwas requiredbyCERA.Damage
included significant ductilitydemands in
the frames inbothdirections, dilation, loss
of vertical support and sliding shear failure
of the floordiaphragms, somegravitybeam
shear cracking, collapseof four setsof stairs
inside thebuilding, somede-seatingof the
surrounding carparking structure, anddamage
inboth theprecast and retained façades.”
“Insteadof demolition, aprogrammeof
temporary strengtheningwas embarkedupon
toallow recoveryof the tenant fitout, and
greater salvageof buildingmaterials. Through
thisdeconstructionphilosophy, over 95%of
thebuildingwas able tobe sortedand recycled.
Thebuildingwasmonitoredandperformed
satisfactorily throughaftershocksduring the
deconstructionprocess.”
The temporary strengthening involveda
top-down sequenceof retrofit of the floors,
someofwhichhad slippedup to30mmdown
the facesof thebeams. This retrofit provided
vertical and tying/diaphragm capacity to
allow crews tomovedown toworkon the
floorbelow. Thedeconstructionallowed close
examinationof thedamage, andprovides
useful lessons for thedetailingand retrofit of
reinforced concrete frame structures.
■
Demolitionwaste from
Christchurch has been
used to extend Lyttleton
Harbour by 6.5 hectares
The Clarendon Tower
was temporarily
strengthened before
demolition
