AMAROO MAIN SEWER PROJECT – 260,000 turds per day!
I have been in Melbourne for almost 4 weeks now and have spent 3 of them finding my feet in the JHG head office and 1 of them trying to work out how to post on the blog. The project I find myself on has not yet hit site and will not do so for another few weeks. Not great considering time on site will be shortened, but it has given me the opportunity to interrogate my captive audience in the office for project information to put AER1 together.
The best way to describe my initial few weeks would be akin to being the new dog in a well established pack. We are most definitely still at the backside sniffing stage. Picture Daz in the middle of the room being circled by dingoes all having a whiff.
Week one was great; I dented my work vehicle reversing into a concrete column – first impressions and all that. Today I got a double combo traffic fine for following Mr Satnav onto a toll road, not paying and trying to play the tourist card (epic fail). The first incident report for the project belongs to yours truly. Explaining that to my project manager was interesting (he is a mountain of a man from Glasgow with hands like baseball mitts – not one you want to annoy).
Anyway, no-one died and the project must go on, or start at least.
I have done this a bit back-to-front in order to submit AER1 in time. So instead of a blog feeding an AER, my AER will write this blog…
My role is as Project Engineer for the Amaroo Main Sewer Project, located roughly 30km north of the Melbourne CBD (central business district). Yarra Valley Water (YVW) is the largest of Melbourne’s three water corporations and services the Northern growth corridor which includes the Amaroo Main Sewer Project. The Victoria State government’s Metropolitan Planning Authority predicts that this corridor will grow to accommodate a population of 260,000 people. There are currently no existing major sewers (or wag bags) in the regions where this growth is expected to occur and the delivery of the Amaroo Main Sewer will ensure sustainability for the development.
YVW intends to construct a new 7.8km long main sewer from North of Donnybrook Road to the existing Kalkallo Recycled Water Treatment Plant in Craigieburn. The main sewer is proposed to have an internal diameter of 1,575mm and be founded at depths ranging between 6m and 14m. YVW has requested that the John Holland Group Pty Ltd (JHG) tender for the Amaroo Main Sewer Project. In turn, JHG has requested that GHD Pty Ltd (GHD) provide a proposal for the temporary works design services for the project.
The Project comprises a trunk sewer, provision for 12 future sewers and 1 connection to an existing YVW branch sewer. This is to accommodate development of the land between Craigieburn and Donnybrook in the future. All sewers are required to have a 100 year life, a smooth internal surface and be installed as per the drawings to ensure gravity fed hydraulic performance requirements are met. The proximity of entry chambers will vary between 284m and 695m, with an average of 502m. They will have internal diameters ranging between 3.2m and 6.0m, with depths from 5.1m to 19.2m. All manholes are required to allow sufficient space to meet operational and maintenance access requirements for the sewer. The delivered article will have no staged access. To reduce the risk of incidents caused by human fatigue, maintenance personnel wearing sewer gear will be lowered into and lifted out of the manholes by means of a Davit Arm. Checking the sewers (up to 695m in length) will continue to be done conventionally.
The head contract is an AS4000-1997 Construction Contract (Modified) between The Client (Yarra Valley Water Corporation) and the Contractor (John Holland Pty Ltd). It is a traditional lump sum contract of $84,179,360.58 AUD – construct only. The lump sum was derived by JHG using a combination of first principles and experience. They benchmarked this project against their previous recent tunnelling project in Woolloongabba. With similar ground conditions and TBMs (tunnel boring machines); JHG used 8m per day tunnelling per TBM as their benchmark when creating their lump sum amount. In order to be able to provide a lump sum, JHG had to know what their pipe suppliers would price at. JHG conducted early negotiations with two prominent competitors – I-Plex and Hobas. After establishing the scope of works with zero (or as close to as possible) unknowns, JHG asked both suppliers for their BAFO (best and final offer). This single contract with I-Plex accounts for $60m of the head contract $85m. From this BAFO, JHG submitted their lump sum to YVW. Schedule of rates contracts under variations would include extra tunnelling e.g. if the client was to request JHG to tunnel further, this would be priced per meter tunnelled.
The client has employed a designer (JACOBS) and a Clients Representative (Aurecon). The client is utilising a third party representative to provide technical and commercial expertise i.e. the client is passing the risk to Aurecon. Jacobs have compiled a Geotechnical Data Report (GDR) which has been analysed to produce a Geotechnical Baseline Report (GBR). The purpose of the GBR is to clearly and succinctly communicate the risks associated with the ground (relevant to the project) to the client (a GDR as we know it).
The method of shaft excavation varies along the project corridor. The three southernmost shafts will be constructed conventionally by excavator and hydraulic hammer (without the use of explosives). The remainder will be either drill and blast or open trenching (depth dependant). Varying thicknesses of steel fibre-reinforced shotcrete (with a compressive strength of 40MPa) will be sprayed onto the shaft walls to mitigate the threat of block slip planes and fretting. JHG will employ a geotechnical engineer to map the rock shaft walls to identify possible slip planes. There is an option to use anchor bolts in resin anchors and steel mesh if the shaft walls are assessed to be unstable.
JHG is not following the usual sub-contracting route. Instead, they will use direct works which is unusual for a Main Contractor these days. JHG will carry out WUC using its specialist tunnelling sector. This demonstrates an appetite for risk; showing a willingness to accept the risk for financial gain. When considering their vast experience in tunnelling, it would appear they are suitably placed to make educated decisions on identifying opportunities in the risks.
A selection of sub-contractors are in the process of tendering for work on the project. In evaluating payment, JHG will receive claims for work done by engaged sub-contractors. These claims will be evaluated by comparing the actual work done against the specified task, and then payment made if JHG is satisfied that the sub-contractor has met its contractual obligations. We are not contractually due to start on site until August 2015, however the client is hoping to grant us access to site on 18 June 2015.
So what have I done? The first few days were spent reading the contract, the specification, the GDR and the GBR. Once my insomnia was cured I was responsible for the DBYD (Dial Before You Dig). This organisation operates 24/7 and acts as a single point of contact between us and service providers. I give a location and proposal of works to be carried out in the area, and receive information from all companies with water, electrical, gas or communications assets in the vicinity. It is streamlined process with a rapid turnaround (all companies provided their information within 2 hours). From this data, I have been compiling a risk assessment on the likelihood of damaging any of the abovementioned assets, putting all data on a one-pager for easy access.
Following on from that, I have been putting together tender packages to be sent out to potential sub-contractors. These include the scope of works, the sub-contract or purchase order, the specification and the drawings relevant to their package. I am specifying by outcome, not method, so as to pass the risk to the suppliers. We have accepted enough risk in the tunnelling.
Notably, I have been tasked with securing a package for the drugs and alcohol testing. It goes without saying that I am eyeing out a ‘buckshee’ breathaliser to see what reading (beer-not-drugs) I can score over one of my loose BBQs.
This week will see us wrapping up the tender packages and hopefully get the surveyors on site to start marking up.
Tomorrow morning I will be attending a CHMP meeting, affectionately referred to as a ‘chimp’. Led by the environmental officer, it is a meeting with the local Aboriginal tribe to discuss the proposed works and identify any artefacts of cultural importance. Identified items will be removed and then restored in place once the execution phase is complete. A huge amount of attention is given to environmental issues, and I am preparing myself for some gobsmacking stuff. On the plus side, Merri Creek (which we will be tunnelling through) is a renowned hotspot for Brown Snakes and Tiger Snakes – both of which are pretty much one way tickets to the crematorium. As John said – God picked up everything that could kill you by looking at you, and threw it in Australia. I am currently on the lookout for a fishtank off gumtree to start my collection of these non-friendly drunken beasts.
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Thanks Daz, Is this a foul only sewer? If so what is the SW plan? all Suds? Any idea what the design flow is and how it was derived?
Daz – sounds quality – a lot going on and a lot of key aspects you are involved with already!
How does the anchor bolt and resin combination work for the weaker wall locations – extend the depth of anchor to reach more solid material or drill at such an angle to cut through slip planes? Are there confined spaces issues to deal with regarding excavation to a certain depth – will this require specific training?
Who holds the risk on hitting a buried surface if not obvious on a drawing?
Richard, yes, this is a foul only sewer. A previous JHG project combined foul with SW which led to manhole covers ‘popping off’ and discharging the joy onto the surface when surface run-off was high.
All SW will be controlled through SUDS. Merri creek, which incises the project alignment, is generally low flow but rises substantially after rainfall (contribution includes baseflow). Baseflow to the creek maintains pools and low flow in the dry season when surface run-off is low.
The so what from this is that the surface run-off in the new development will be channelled into Merri Creek (and Malcolm creek further south). From here it will make its way south into the Yarra River before discharging into Hobson’s Bay (ocean). The feeling I get here is that flooding is not deemed to be as much of a risk as it is in the UK, therefore less attention is giving to its mitigation (Merri Creek flow dropped from 85.5ML after heavy rains on 01 Jun 15 to just 7.0ML on 08 Jun 15). The focus is on being able to sustain the regional development along the Northern corridor (sewerage).
That’s not to say it has been ‘chinned off’ – it just has no impact on my project. I am aware of the client conducting water modelling, sewer modelling and stormwater modelling. They are also in the process of making an assessment of the creeks and requirements for stormwater discharge. Their preferred option to manage the stormwater is to reduce frequency and volume discharged into the creeks by:
• Installing rainwater tanks in each property,
• Employing targeted stormwater management (in the form of sedimentation basins, wetlands and bioretention).
In a nutshell, the risk of SW mismanagement has not been directly taken into account for the Main Sewer Project, but it will affect the client after my project once urban development has gathered momentum.
Damo, the anchor bolts are 1800mm in length, 20mm diameter. The drilled hole (26mm diameter) is filled with a quick set resin (length of both drilled hole and quick set resin determined by temporary works designer). The remainder is filled with slow set resin grout.
This pins a 150x150x8mm domed plate and ball against the steel mesh which in turn is secured to the shaft wall (much the same as the bolt anchors we saw at the new housing development on Phase 1). The angle will be constant at 15 degrees downwards into the wall.
Worth noting is that for buildability purposes, all anchors will be 1800mm, even if less is required. All holes will be drilled by hand. Anchor capacity is between 40 and 60kN/m depending on the assessed stability of the rock. This equates to 72 to 108kN anchor capacity per bolt. This will undoubtably result in over-engineering, but the time (and therefore money) saved by uniformity supercedes this. The minimum diameter of a shaft is 4.8m. A tradesman with a 1.8m drill bit + drill (not B&Q special) + sweaty Aussie = not a heck of a lot of room to play.
So to answer your first question succinctly, the depth is specified to vary but will be uniform, as will the angle.
Confined spaces? Yes. All personnel entering a shaft will require both confined spaces and working at height.
JHG is utilising a third party to provide labour on site. The reason behind this is that JHG is not allowed to employ people for ‘just a project’. Therefore, once a project is complete, JHG sits with salaries to pay and no income. Drug and alcohol abuse is also an issue and JHG is required, by law, to rehabilitate staff with substance dependancies.
To eliminate the risk of wasting HR time (and money), JHG utilities a company called TAG which provides skilled labour. This gives JHG the power to release employees at short notice. The project superintendent (akin to an RE SSM) takes care of the hiring and firing.
Apart from mitigating against risks associated with employing people, another benefit of using TAG is that they are responsible for ensuring their employees are medically fit and qualified to carry out their work i.e. working at heights and confined spaces tickets. Another cost saving to JHG (although it is no doubt built into the labour rate).
Services – The contract is a construct only. JHG will be self-performing the specialist tunnelling works and utilising TAG for skilled labour. As mentioned in the blog, I have conducted the DBYDs which is the bare minimum required. My next step will be to employ a third party representative to survey the ground prior to excavation. Risky areas (the very few that there are) will require NDD (non-destructive digging).
An AMS (activity method statement) is produced by the project team. This assesses technical, commercial, safety, quality and environmental risks associated with the activity. A TRA (task risk assessment) is then put together by the project team together with the subcontractor to identify risks associated with physically carrying out the task. These two documents are produced along with a permit to excavate and a ‘start card’ before a shovel hits the ground. We are working in the middle of nowhere and the risk of hitting services is low, but should it happen, it lies with JHG.
I hope I’ve answered your questions. If not, you know where to find me.
Daz, thanks for the detailed reply. Interesting health and safety considerations with hand drilling 1800mm holes, not just hand arm vibration but dust also. We have got some diamond drilling going on and one they take ages and two need constant water suppression. The drill just runs when set-up so you might be able to do that and reduce the sweaty Aussie factor!
Interesting point Damo. I had not given any consideration to hand arm vibration. This team is very experienced in tunnelling, it is viewed as a specialist wing within JHG, and something that is difficult to leave once you are in. I would assume that it has not been brought up due to the labour being employed through TAG (3rd party). A simple labourer costs $750 AUD for a 10 hour day. The minimum wage is around $20 AUD per hour ($200AUD per day). The difference is the price JHG is paying to pass the risk (of HAV and the like) onto someone else.
On a lump sum contract, it appears the PM is willing to accept higher upfront costs in pursuit of fewer surprises down the line to enable greater certainty when forecasting. It’s not to say he is risk averse (we are self performing the tunnelling), but he chooses risks he is more able to manage through good project management and engineering.
He has PM’d two projects (1 was 5 years and the other was 2 years) for JHG who aim for an 8% margin when tendering. On both of those projects he achieved 20%. I would hedge my bets on him knowing what risks are worth taking and what are worth handballing (Aussie lingo for sloping shoulders).
Thanks Daz, very happy with that.