echo arena carpark

ECHO ARENA CARPARK

KEY STAKEHOLDERS

DESIGN TEAM

HISTORY OF THE STRUCTURETHE BUILDING

The car park was designed by Hill Cannon and built by SCC Design and Build in

2005, opening that same year. The structure consisted of precast reinforced

concrete with portalised beams and columns on a regular grid which in turn

supported the ribbed precast concrete slab units, these had a cast in-situ stitch

detail to anchor the slabs across the beams, saddling over to create a cohesive

structure. The vehicle circulation was via a long internal ramp giving access to

flat deck areas either side. The pedestrian access and means of escape was via

four precast concrete cores situated on the perimeter of the car park area.

The car park housed a ground floor administration office together with the

arena management suite, a substation and plant room with further plant

housed at roof level. To the north side a covered access road links to the

adjacent arena loading bay where at this point the adjacent building abuts the

car park and utilises the lower level structure of the car park for support. The

car park has on two sides a single aspect residential development with a

separation zone of around 7m to the East and 4m to the South elevations.

HISTORY OF THE STRUCTURE

• On New years Eve 2017, the Arena was hosting the annual

Liverpool International Horse Show which is a very popular event often

selling out with people travelling substantial distances to watch and

display in the show.

• At around 16:27hrs the first signs of fire are visible by internal

CCTV cameras on level 3 with smoke visible on the external CCTV

cameras approximately 8 minutes later, this was then followed by the

first of only 5 emergency calls being made at 16:42hrs along with alarm

being raised within the structure, the emergency services arriving on

scene within 3 minutes of the call proceeding to fight the fire.

• The emergency services initial concern was to evacuate all persons

from within the structure with many still in their vehicles attempting to

vacate on floors above unaware of the situation unfolding beneath

them on level 3.

• The fire crews reported a river of burning fuel flowing down the

drainage route on the designed falls and into the drainage system

allowing spread of the fire to other floors below, at 18:38hrs all

firefighters were evacuated from the structure due to the ferocity of the

ensuing fire and the speed at which it was spreading through the

structure and vehicles.

• At this point all efforts were directed at preventing damage to the

surrounding structures as the fire had progressed so rapidly, with all

vehicles at this point presumed to be consumed buy the fire.

INITIAL ASSESSMENT OF THE STRUCTURE

Following a call on the New Years Day from our client I was asked to attend site in the following days once the fire brigade had finished their works to review and discuss the immediate state of the structure and the possible emergency demolition methods we could employ to bring the structure to safety.

Upon my arrival on site I was greeted with little or no information on the structures current state and allowed to conduct my own visual assessment of the structure from the non damaged sections, attending site on the same occasion was Steve Vollar of Hill Cannon who was the original designer of the carpark to carry out a structural assessment along with various insurance loss assessor and stakeholders.

During my assessment I noted that there had been substantial explosive spawling to the rib deck planks with many in the central sections having the inner reinforcement bar visible and signs of deflection, the main span beam running West to East again showing signs of explosive spawling with distortion laterally and some twisting at their doweled connection point the stanchion, the stanchions themselves being relatively untouched with the exception of twisting on the corbelled seat upon which the beam sits.

Explosive Spawling

• As you can see from the image the rib decks show signs of complete loss in many areas of their structural rigidity, they are now no longer acting as a diaphragm between the beams and are in many places showing complete deflection.

• The decks themselves having only one layer of mesh within the 80mm of concrete cover and 2no. 20mm chords per rib, the chords within the rib acting as the tie to the adjacent plank via a stitched arrangement saddling over the beam by 30mm to each side.

Explosive Spawling

• You can see from this image the damage and spawling to the beams, and although not too clear given how close we could get to the stanchion, there is visible loss of concrete to both the corbel and beam connection at the point at which it is dowelled in to the stanchion.

• The beam itself in this particular location has twisted at the connection point to the stanchion.

Spawling of the

beam, reinforcement

visible

Delamination of the

corbel connection point

& twisting of the seat

Venting of Heat

• The ramp situated in the central section of each floor is connected by the parking areas, the ramps stacked above each other throughout the structure in the same gradient.

• The main source of the heat damage was most visible in these sections, the reason for this we presume is natural convection, the sides of the structures are open allowing free flowing air fueling the fire and the ramp being central and open allowing clear exhaustion with the ramp section effectively acting as chimney, this also allowed the fire to spread upwards to cars parked either side of the ramp at each level.

• The roof deck itself all though looking in good condition from above also had signs of severe deflection with water pooling central to each bay, the deflection seen was in excess of 30mm in places.

Visible Movement

• The car park had 4 external stair cores, the stair cores are pre cast concrete sections lifted in to position on site with each section tied via a fillet weld on angled plates at the abutment to each section.

• The landings are sat and held in situ by the section above with the actual stair planks sat on shelved lips top and bottom and not pinned in anyway.

• The stair cores themselves had visible signs of thermal movement, most visible on the wall adjacent to the carpark, with the stair sections showing signs of movement in excess of 15mm on the their shelf in the Northern core and complete separation of fillet welds in the Eastern core.

• Tell tales were added to each location to monitor further movement.

SITE CONSTRAINTSEcho Arena

Convention Centre


Convention Centre Staybridge Hotel



Apartment Block 1



Apartment Block 1

Apartment Block 2



Apartment Block 1

Apartment Block 2

Pullman Hotel



Apartment Block 1

Apartment Block 2

Pullman Hotel

23m

12m7m

4m

SITE CONSTRAINTS

Service Tunnel &

Arena Basement GF

to 2nd floor level

within the footprint

of the structure

Live Substation &

Genreator Room GF

to 1st Floor Level

Live Pump House

GF to 1st Floor Level

SITE CONSTRAINTS

Service Tunnel &

Arena Basement GF

to 2nd floor level


of the structure

Live Substation &

Generator Room GF

to 1st Floor Level

Live Pump House


Live HV Cables

slung from the

spandrel panels at

1st floor level

2 no. 10t McQuade AC Units

still full of coolant situated

on a damaged section of

roof slab

SITE CONSTRAINTS

Service Tunnel &

Arena Basement GF

to 2nd floor level


of the structure

Live Substation &

Generator Room GF

to 1st Floor Level

Live Pump House


Live HV Cables

slung from the

spandrel panels at

1st floor level

2 no. 10t McQuade AC Units

still full of coolant situated

on a damaged section of

roof slab

To remain

operational

throughout

To remain

operational

throughout

To remain

operational

throughout

KEY RISKS

• Structural disproportionate collapse

• Live services

• Reduced exclusion zone due to proximity of other structures

• Potential for further fires due to volume of vehicles within the structure holding fuels

• Potentially toxic dust owing to the fumes generated within the fire

• Run off to water courses given proximity to both docks and the river Mersey

• Public interface as the convention centre is to remain open

• Ground conditions to areas of site not suitable for heavy plant

• Limited working space to commence demolition works from

• Trespass given the value of vehicles housed on site and pubic interest

• Noise & vibration as the site was relatively concealed within the other structures

• Damage to structures that are to remain following demolition works completion

KEY RISKS -MITIGATION

• Structural disproportionate collapse – Remote demolition within a controlled exclusion zone to be adopted, risk of collapse over 5tons to be expected and as such not reportable under RIDDOR

• Live services – All external services to be removed from the structure and diverted underground

• Reduced exclusion zone due to proximity of other structures – Sacrificial designed scaffold to be erected on the apartment blocks c/w monoflex to protect glazing

• Potential for further fires due to volume of vehicles within the structure holding fuels – Car holding bay to be set up with specialist plant nappies for fuel spillage along with fire balls at key points

• Potentially toxic dust owing to the fumes generated within the fire – Utilisation of dust control at source machine mounted and dust cannons at ground level

• Run off to water courses given proximity to both docks and the river Mersey –Fuel water separator to be cleaned out pre works and capped

• Public interface as the convention centre is to remain open – Fully closed hoarding to be erected with media viewing point allowing coverage within a safe space

• Ground conditions to areas of site not suitable for heavy plant – Basement to be visually marked on site to ensure plant over 50tons does not track on the basement lid, ecki mat system to be constructed to protect the plaza paving during works

• Trespass given the value of vehicles housed on site and pubic interest – Full time guarding in place

• Noise, Dust & vibration as the site was relatively concealed within the other structures – Monitoring stations set up on public boundaries capturing live data with audible and visual alarms for set limits.

• Damage to structures that are to remain following demolition works completion –All areas that are to remain are to be fully air gapped prior to works commencing with designed protection measures in place above them

CONTROL, ELIMINATE, REDUCE

• Over the upcoming months dozens of loss assessor’s and engineers attended the structure, many of which were proposing a top down or deconstruction process, removing the planks and salvaging the frame

• The engineers enlisted by the insurers managed to assess many parts of the structures using drone technology giving a detailed report on approximately 80% of the structures integrity and managing to designate safe walking routes within very small sections

• At this point the project turned more in to a process of mitigating the insurance loss amount, with the safety of workers becoming almost second on the priority list in the insurers eyes, it was then that I enlisted the help of Stephen McCann to conduct anunbiased report on both the structure and the possible demolition methods that could be employed, Stephen also swiftly indicating that remote demolition being the only plausible option as the others did not take account of the risk hierarchy

• Myself and Stephen attended one particular meeting with a strong mindset of walking away from the scheme after being dismissed by a loss assessor and told we didn’t really know what we were talking about. At this point I proposed my client consult the HSE for their view on the works as all other options of demolition needed operatives to enter the structure putting them in harms way

• The HSE consultation meeting was a success and after tabling our proposed method of remote demolition using demolition adapted excavators they advised that this would be the only viable option as all other options would create unnecessary risk to life. They also advised they would be keeping a vested interest in the scheme as it progresses

PLANNING & MANAGING

EXPECTATIONS

• The scheme was now gathering momentum with many months passing from our initial assessment, emergency demolition was no longer the buzz word and the structure was now likely to stand till October 2018 before demolition works could commence, with emergency demolition only carried out if totally necessary

• This was mainly down to all parties signing off on the proposed methods and the surety of the service ramp, pump house and substation being safeguarded as far as reasonably practicable as retained sections upon completion

• Service diversions, propping and cutting of the structure affording divorce separation along the retained elevations

• Agreement, design and installation of all temporary works

• Managing environmental concerns, surveying the debris and installing monitoring equipment

• Dilapidation surveys of all surround assets

• Labour party conference heightened security & ring of steel for the party conference

• Agreement of working boundaries and acceptable timings

• Preservance of evidence, the source car being subject to a potential claim of £80m

• Dealing with insurers assets with circa 1,400 vehicles still in situ

TEMPORARY WORKS

Service Route Soffit

• As the service route was to remain operational although still under our control, we had scaffold erected across the soffit along with debris protection to catch any debris should there be movement.

• We had to ensure the soffit was visible to allow daily measurements to be carried out, this would allow movement to be highlighted early and the area closed off should a problem occur.

Service Route Lid

• We asked Mabey to design and install a crash deck system over the floor plate L1 above the service route, this was designed for a constant load of 5KN with a single point load of 22KN.

• The same was then installed along the ground floor in gridlines CD-CE/C12-C10 due to a change in the level of the service ramp at this point.

Substation, Pump & Generator Room• The same was also installed over the pump house, substation and generator housing

• The above system was designed to allow demolition material from the floor slab directly above to sit on the crash deck up until the point it could be unloaded safely

• The outer sections of roof were also protected for falling debris

Gridline CE & Vent Stacks

• Along gridline CE was a retaining wall supporting the Plaza, due to the change in levels across the site it was necessary to use super props as raking supports along this GL, the props were then covered in geo textile and 6F5 for protection form falling debris.

• There was also a need in this location to divert 2no. twin wall aluminum vent stacks from the structure moving them to the adjoining apartments should the generators which power the arena in the event of an emergency need to energise.

Scaffolding & Floor Protection

• Scaffolding was designed and erected as a protection measure to the Apartment blocks, this was only however a superficial protection measure for flying debris

• The plaza area was covered with geo textile and then overlaid with 150mm ecki mats laid to span the basement beams below, visual markers were in place to prevent any plant beyond 50t accessing this area

Scaffolding & Floor Protection

• Scaffolding was designed and erected as a protection measure to the Apartment blocks, this was only however a superficial protection measure for flying debris

• The plaza area was covered with geo textile and then overlaid with 150mm ecki mats laid to span the basement beams below, visual markers were in place to prevent any plant beyond 50t accessing this area

Reduced weight

limit

Fuel/Oil Spill Control

• As over 1,150 of the vehicles were simply burnt out chassis the insurers allowed these as a demolition asset and as such they were to be recycled as demolition waste

• The remining 250 vehicles were however intact, fuel removal was ruled out due to the fire risk it created and the vehicles could not be moved without risking altering of load paths with the possible outcome being a disproportionate collapse, due to this we had specialist plant nappies created along with inserts. The design of these containing activated charcoal which would allow water to seep through yet still retain oils and fuels

• The vehicles were taken away on specialist transport as the insurers assets and for personal effects to be recovered were possible, this process was CCTV monitored to avoid risk to of litigation

• Due to process involved the intact vehicles become salvage only due the damage caused by the demolition attachments during removal

DEMOLITION SEQUENCE

BAYS AT RISK OF COLLAPSE

SOURCE CAR REMOVAL

TIMELAPSE FOOTAGE

LEAD CONTAMINATION

• In the initial ash report it was highlighted that there was a presence of Lead amongst the ash along with other

contaminants, at this stage analysts could not classify how the resultant waste could be treated post demolition

• The ash could not be removed pre demolition due to the instability of the structure, the EA suggested washing it

through each floor plate, we opposed this due to the risk of slurry overloading sections of slab and the wash off being hard

to control

• Socotec began taking samples mid way through phase 1 attending weekly up until the full structure had been brought

to grade, the samples all contained Lead contaminant with many being above the threshold for hazardous landfill

• At this stage we began conducting lead monitoring at both point source and the boundary to ensure lead was not

becoming airborne, all results showed the dust controls to be effective

• We assessed that approximately 8 tons of car batteries had been vapourised within the structure and came to rest

within the debris

• The samples however showed a slight reduction weight by volume in the freshly processed demolition material

• We then carried out a small scale process by crushing a quarantine pile of approx. 500tons to 150mm down to reduce

fines creation, this was then screened removing 0-10mm, 11-75mm & 75mm-150mm with all resultant products sampled.

The results showed the 0-10mm having the highest concentrations of lead with this element needing lime stabilization or

similar to become fit for landfill, the 2 remaining sizes highly likely due to abrasion within the process were now clearly sat

in the non hazardous category with some samples almost inert

• The resultant waste was always the main clients risk and as such the screening process information was shared with

them, the resultant waste pile to date is still sat bunded on site awaiting a decision on how to progress.

LITHIUM BATTERY PACKS

echo arena carpark

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