MARDI – MANGROVE LINK PROJECT
Prepared by Scott Allison (Crux Surveying Pty Ltd)
Mob: 0404850381 Email: [email protected]
NSW Excellence in Surveying & Spatial Information Awards 2011
Excellence, transparency and a commitment to go beyond the call of duty are the strong foundations on which Crux Surveying was built. Crux Surveying’s Statement of Excellence represents the heart and mind of what makes Crux Surveying a special place to work.
Going far beyond the call of duty. Doing more than others expect. This is what excellence is all about. It comes from striving, maintaining the highest standards, looking after the smallest detail and going that extra mile.
“Crux Surveying went beyond their scope of works to provide John Holland with a complete re-design of the Mardi – Mangrove Link Pipeline. Crux Surveying provided a very efficient and professional service to John Holland and as a result John Holland were able to construct the pipeline with the ability to solve unforeseen site issues and make changes within a very short period of time. They provided a seamless integration of the design through to set-out and construction.” – David O’Connor (Construction Manager)
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CONTENTS
OVERVIEW Pg 4
PROJECT BACKGROUND Pg 6
Route Selection Process Pg 6
Protecting the Yarramalong Valley Environment Pg 6
Landholder Liaison Pg 7
Easements for the Pipeline route Pg 7
Crossing Wyong river Pg 8
PROJECT PROCESS AND EXCELLENCE Pg 9
APPENDIX Pg 12
Sample Weld Restrain Sketch Pg 12
Sample Design Plans Pg 13
Site Photo’s Pg 17
John Holland Correspondence Pg 22
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OVERVIEW
The Mardi-Mangrove Link Project is a key element of WaterPlan 2050 which is the long term water supply strategy for the Central Coast. It will help to secure the region’s town water supply over the next four decades by linking Wyong River and Ourimbah Creek to Mangrove Creek Dam, via Mardi Dam.
The project is an initiative of Gosford City and Wyong Shire Councils with Australian Government funding of $80.3 million from the Water Smart Australia Program and an additional $40 million combined from the two Councils. The Mardi-Mangrove Link pipeline is the largest water infrastructure project undertaken on the Central Coast since the mid-1980s when Mangrove Creek Dam was built.
The project was awarded to John Holland Pty Ltd in 2009. John Holland initially engaged Crux Surveying’s in February 2010 to provide setout and work as executed plans for the DN1000 pipeline, valve pits, structures, pump station, electrical reticulation and fish weir. The Mardi – Mangrove Link had an original design which needed to be redesigned due to unforeseen circumstances. The redesign was to also take into account the approved construction corridor, which at times was only 10m wide, the steep terrain and availability of pipe and bends. Because of the strict timeframe a redesign was to be carried out in conjunction with the construction of the pipeline.
John Holland approached Crux Surveying based on its experience in designing roads and drainage. Designing a 21km DN1000 pipeline, consisting of pipe bridges, valve pits and a 300m Horizontal Directional Drilling creek crossing was a major challenge, but Crux Surveying rose to the challenge. With the knowledge of, and liaison with, John Holland’s engineers, Crux succeeded in providing the construction crews with 35 pages of design. Each page consisted of approximately 600m of pipe long section and plan. Crux Surveying was also involved in some minor structure and pipe redesign for the two pump stations and existing pipe tie-ins.
Locality Sketch [Gosford/Wyong Council’s Water Authority]
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The complete Mardi – Mangrove Link project involved building:
• a 2.1 kilometre buried water pipeline from Wyong River to Mardi Dam through Mardi • a 19 kilometre buried pipeline from Mardi Dam to the existing Bunning Creek Tunnel at Mangrove Creek Dam, running through Yarramalong Valley • a new pump station at Mardi Dam • a new pump station beside Wyong River • and associated works.
The Central Coast community will benefit from the Mardi-Mangrove Link as it will help to boost dam storage levels, speed up drought recovery and help protect the region against future extended periods of below average rainfall.
Overall Route Layout (GHD Pty Ltd – Original Plan)
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PROJECT BACKGROUND
A range of pre-construction activities had been achieved for the project. These included environmental and engineering studies and investigations, selection of the pipeline route, community and landholder liaison, statutory approvals, concept and detailed designs.
Route selection process
Selecting the pipeline route through Mardi and Yarramalong Valley was a major element of the Mardi-Mangrove Link pre-construction work. Where possible, the route selection process considered the following factors
• local topography to avoid extreme changes in elevation • protected ecological and heritage features • potentially difficult pipe laying conditions (eg rock, thick vegetation, etc) • construction needs (eg sufficient space for equipment operation, pipe storage, backfill materials, etc) • potential road closures and impact on local traffic flows • access to the pipeline for future operation and maintenance work
An expert panel then used a multi-criteria analysis to assess five key criteria including:
• Landowner impacts • Community impacts (including impacts on Yarramalong Road) • Environmental impacts (including heritage / cultural impacts) • Constructability • Comparative cost estimates
The proposed route was then subject to stringent reviews from an engineering, construction, design, environmental, geological and cost perspective.
The pipeline route crosses a mixture of public and private land, with about 20% within the road reserve.
This route selection was carried out prior to Crux Surveying’s redesign. However, some of the route was altered during the redesign stage to further minimise the abovementioned impacts.
Protecting the Yarramalong Valley environment
Extensive environmental planning and investigations were undertaken for the Mardi-Mangrove Link Project to ensure activities did not have a significant impact on the Yarramalong Valley environment.
The pipeline route was selected to avoid sensitive ecological areas and to avoid significant impact on threatened species and endangered ecological communities. Senior ecologists were also involved in the entire route marking process.
A number of safeguards and mitigation measures were also be implemented during construction of the pipeline and associated works. These include:
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• retention of large trees either side of the pipeline easements as close to the pipeline as possible to maintain a local resource of hollow-bearing trees used by local fauna • delineation of sensitive ecolological areas using temporary fencing or tape • on-site attendance of a fauna ecologist during vegetation clearing.
Detailed Project investigations also identified that the pipeline route corridor would not have a significant impact on local aquatic ecology or block fish passages.
When areas in the Valley had to be disturbed during the construction process, revegetation was undertaken as quickly as possible to minimise the overall impacts. This became a major issue for John Holland due to the changing climate conditions. This commitment was challenging for the contractor due to significant rainfall during the construction period.
An Indigenous heritage study was also undertaken to check if any important cultural items existed in pipeline route and an approach developed to ensure management in accordance with relevant State Government requirements and the local indigenous communities.
Landholder liaison
Extensive landholder liaison was undertaken by John Holland and the Project Team, particularly with those directly affected by construction.
Stakeholder input was a key part of the route selection process, community meetings, open house events, one-on-one discussions, telephone and email discussions, and written correspondence all forming part of the liaison process.
The project team provided affected landholders with comprehensive Landholder and Easement Packs which included a range of fact sheets and other information about the Project. The packs helped to explain land entry protocols, the easement acquisition process, insurance and liabilities, compensation payments, construction issues and other related matters.
Because of the changes that had to be made to the pipeline route, the project team, including crux surveying, continued to liaise with affected landholders as the project progressed. There were times during the project where decisions on pipeline route and redesign were being made as the pipe was being laid.
Gosford City and Wyong Shire Councils have a statutory right under the Water Management Act to access properties affected by the Project, however, their preference was to gain landholders' consent before accessing their land.
Easements for the pipeline route
A pipeline easement will be registered on each affected land title for Wyong Shire Council to construct, operate and maintain a buried water pipeline on that piece of land (except for where some above ground facilities might be required, such as valves and pipe-bridges).
Affected landholders received compensation for the pipeline easement in accordance with the NSW Land Acquisition (Just Terms Compensation) Act 1991.
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Easements will be subject to a number of usage restrictions once the pipeline is built and the land restored back to its original condition. These include landholders being unable to:
• erect any buildings or structures on the easement • plant trees or carry out deep ripping or deep excavations • take onto the easement any vehicles or equipment that weighs more than the maximum legal load for such vehicles or equipment on NSW Roads
Subject to obtaining prior consent from Council, landholders can still:
• construct a roadway, pavement, fence, billboard or cable • make other improvements on or under the easement • alter the existing grades and ground levels of the easement • plant orchards, small trees or shrubs, carry out other landscaping work
Landholders will continue to have access over the easement and can use the land for cultivation, cropping and grazing of livestock. They can also grow pasture, farm turf, control and eradicate weeds and top dress and pasture seed.
Crossing Wyong River
The pipeline route corridor for the project crosses Wyong River four times as it runs through the Yarramalong Valley.
Three of these river crossings are pipe-bridged (in Sector 3 and Sector 9 of the pipeline route) while one is under bored (in Sector 8) to avoid a state-recognised Property Vegetation Plan. Each river crossing has been individually assessed to ensure minimal impact on the surrounding environment during construction.
Pipe-bridges are not formal access bridges but the pipe itself will 'bridge' between supports on each side of the river. The pipe-bridges required foundation support piles which are set back from the edge of the watercourse.
In sector 8 the pipeline was under bored (under the river) to avoid an area of the property registered with the NSW Government under the Native Vegetation Conservation Act 1997. Horizontal Directional Drilling (HDD) was used to achieve this underbore together with DN1200 HDPE pipe. High-density
Polyethylene (HDPE) pipe is flexible and can bend to a minimum radius of 39.6m in perfect conditions. UEA was the contractor for the underbore. HDD has three stages:
1. a pilot hole is drilled along the prescribed path 2. the hole is then enlarged by a larger cutting tool known as the back reamer 3. the water pipe is then pulled back through the enlarged hole.
As part of the pipeline redesign, Crux Surveying liaised with UEA and John Holland to prepare the design of the underbore. The design criteria was quite involved as the HDPE pipe had a minimum radius of 39.6m and the drill profile needed to follow a path that avoided as much rock as possible. The profile at some points was up to 19m deep to achieve this.
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Any bank stabilisation or restoration work needed along the river bank was carried out within weeks of construction. Riparian zones will are restored or rehabilitated after construction.
All river crossings have been subject to extensive NSW Government liaison. The work was also conducted in accordance with conditions in the Review of Environmental Factors (REF) document.
PROJECT PROCESS & EXCELLENCE DEMONSTRATED BY CRUX SURVEYING
Designing and setting out a 21km pipeline for construction was no small feat. Crux Surveying setout the initial pipe construction corridor based on the original design by GHD. To do this, survey control had to be placed along the pipe route. This was done using RTK GPS and conventional TPS techniques due to a lot of the pipe route being heavily vegetated. It was then realised that the original pipe design was going to be hard to construct and very costly at times. This was when it was realised that the original design needed a makeover.
Construction of the pipeline was to start within a week of this realisation and John Holland needed the redesign to be started and at least 1km of the pipeline designed and approved for construction within the week. Crux Surveying used Civil 3D as the design software together with a new desktop computer to cater for the processing requirements of the file.
This started to become a challenge when more pipe laying crews started. All started at different chainages along the pipeline. There was then the challenge of redesigning the pipeline in sections and making sure each section being designed tied into the next. This was all being done alongside construction of the pipeline. There was no room for error and a lot of forward thinking had to be done during the design process.
Because the pipe route had a nominated 10m easement zone, the new design could not go outside this area unless agreed with by the property owner. This normally took time and was not an option in most cases making it even more difficult to calculate the alignment of the pipeline. There were sections of the pipeline where each pipe at a 1 degree deflection to keep it within the easement.
This had to be managed out in the field also to make sure that the setout and pipe contractors were following the design. Any small error or wrong deflection would cause the pipeline to encroach over the easement causing major issues with the property owner and further compensation having to be paid to them.
Then there were the changing climate conditions and a lot of rain. Access to some areas of the site was impossible and pipe laying crews had to relocate to higher and drier areas of the site where the redesign had not been completed. Due to these unforeseen circumstances the redesign of this new area had to be completed within 24 hours. At one point in the project there were 5 pipe laying crews and 1 designer working extended hours to keep ahead of the crews.
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Access Bridge (Gate J) under water due to localised flooding
One major challenge of the design was to consider lengths of pipe and pipe stock already ordered and delivered to site. There were sections of the pipeline which were welded with 13.4m Spherical Slip-in Joint (SSJ) pipes, other sections where Rubber Ring Joint (RRJ) pipes were 12.15m and 6m in certain road sections. SSJ pipes could have a maximum deflection of 2.5 degrees and RRJ pipes could have a maximum deflection of 1 degree due to the area being in mine subsidence zone. A number of 6 degree hockey stick bends were ordered for the job also. Any deflection over 6 degrees had to have a weld restraint or concrete thrust block with the length calculated from a formula provided by GHD which took into consideration: depth of pipe cover and soil conditions. Weld restraint & concrete thrust restraint sketches were drawn up by Crux Surveying as part of the design and given to the pipe laying contractors to minimise site cuts and pipe wastage.
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Concrete Thrust & Weld Restraint Sketch Samples (see appendix for larger image)
Every pipe that was placed in the ground had to be as built and at each day’s end checked and filed for the final work as executed plans. GPS and Robotic TPS were used to reduce the cost of staff and costs to the client as survey assistants were not required for the pipeline works.
John Holland appreciated the fact that it was a seamlessly integrated communication between the engineers, the redesign and Crux Surveying’s surveyors’ onsite. Crux Surveying’s involvement sped up the process and allowed construction to flow easily without any delays. Any redesign could be passed onto the surveyors and contractors in an instant.
Crux Surveying provided the construction and infrastructure industry with evidence that the surveyor’s role on infrastructure project goes way beyond the standard setout surveying and they will go beyond the call of duty to provide the client with a professional service to assist in the design and construction of a project.
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APPENDIX
Sample Weld Restraint Sketch –
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Sample Design Plans –
CRUX-1660607-W108 [REV 4]
CRUX-1660607-W118 [REV 2]
CRUX-1660607-W125 [REV 5]
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Site Photo’s
Work Package 01 – Setting out Inlet Pipes
Work Package 01 – Construction of Wyong River Inlet Structure
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Work Package 01 – Wyong River Inlet Structure
Work Package 02 – Construction of Wyong River Pump Station
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Work Package 06 – Transfer Main Connection
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Work Package 06 – Pump Station Structure
Work Package 07 - High Density Polyethylene pipe laid out for 300m Wyong Creek under-bore
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Work Package 07 – Bunning Creek Bridge & Pipe Bridge
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