Don Johnson
Thiess Contractors

The surface rehabilitation of the former nuclear test sites at Maralinga has created a world benchmark in the cleanup of radioactive materials. Extensive modification of vehicle cabins enabled a well controlled bulk earthworks operation utilising Caterpillar 631 Scrapers to complete the works. The recently completed project was an outstanding success when judged against all key criteria. This paper will deal with the contractor's approach to execution of the project.

The surface rehabilitation of former nuclear test sites at Maralinga was recently completed by Thiess Contractors Pty Limited under a contract with Works Australia (now GHD), the Project Manager appointed by the responsible Australian Government Agency, the Department of Primary Industries and Energy.

The project involved the collection and burial of over 400,000 cubic metres of contaminated soil from over 2,300,000 square metres of arid ground, together with extensive vacuuming and sweeping of rock surfaces, and exhumation of Category 3 burial pits.

This paper will focus on key elements of the Contractor's tendering strategy, and project execution plan.

The client stated in an Information to Tenderers document that "Two streams of management flow through the contract for this project. The first and most important is the management of the radiological risk to health on the site. The second, and subservient, is the management of the construction processes to achieve the Principal's aims with respect to the future safe use of the site".

How did Thiess respond to these stated objectives of the Client?

Firstly, we took a company decision to carry out the project as an internal joint venture between the geographical construction division and the environmental services group, which specialises amongst other things in site remediation. In this manner, we combined specialist remediation knowledge with the necessary skills in bulk earthworks, logistics, industrial relations and safety.

The next challenge was for Thiess to develop a strategy to best respond to the Principal's project requirements. As stated in his tender specification, we were aware that the management of the radiological risk to health on the site was of utmost importance - the key criteria for Contractor selection. However, we knew that other factors would be important considerations in the assessment of the successful tenderer. To this end, we focused on:

• development of methods that would collect soil in accordance with stated criteria, and not redeposit collected soil on clean ground.
• The developed method had to be economical. Despite the primary objective of no radiological risk, we were nevertheless in a competitive tender situation and price would undoubtedly have an impact on tender assessment.
• plant selection was an important matter in respect of achieving all client and tenderer/contractor criteria. During the tender period, and post award, we spent a great deal of time analysing various plant fleet options. In fact, we submitted two tenders to the client based upon different plant fleets as the tender prices were significantly different but we felt each responded in a different manner to the project criteria.
• nominating a project team which possessed the necessary blend of hard dollar construction experience and site remediation experience, and was prepared to spend up to 2 years in a hostile environment, living in a construction camp on a 3 week on/1 week off cycle.
• ensuring that an occupational health and safety focus remained on the project, despite the primary focus on radiological safety.

As Thiess was successful with its tender, and the project delivery met or bettered all parameters, we can only assume our perception of client selection criteria and key issues on the project was somewhat accurate.

The Contractor was required to select a plant fleet for the project which efficiently collected contaminated soil and debris and met both performance and radiological safety requirements. The specification detailed the following parameters for soil collection plant and equipment

• dust suppression was to form part of all soil and site removal and transport methods such that all activities are carried out in a low dust environment.
• soil removal process was not to cause mixing of soil in the layer to be removed and the underlying soil.
• soil removal process was to minimise spillage of soil

In order to meet the rules in these parameters, the following limitations applied to equipment selection:

• no tracked equipment was to be used for soil removal operations
• elevating scrapers were not permitted to be used.
• no contaminated soil was permitted to fall from a height of greater than 0.5 metres.

Plant fleet options considered by Thiess included:

• auger scrapers - these were discarded due to potential for cables in the ground to fowl the augers.
• push pull scrapers - discarded due to concern at filling the bowls of scraper (only 100mm cut in sand)
• Excavator and bins utilising a Roll on/Roll off ((Ro/Ro) truck. This was a serious option and we in fact submitted an alternative tender on this basis. We felt it may have slightly better met client criteria, but was considerably more expensive, took a longer duration, and required a greater number of employees, thus increasing the client's long term radiological exposure.
• Caterpillar 631 open bowl scrapers pushed by a rubber tyred dozer. This method met all criteria as well as enabling a "bulk earthworks mentality" to prevail within the stringent radiological regime on site. Significant cost and program advantages existed over the excavator/truck option whilst minimising the number of employees on site.

Our tender was selected based upon the open bowl scraper option. Post tender, we carried out offsite trials to ensure the proposed method would work. At this point, we did change the procedure in that we had originally proposed a grader to windrow the soil (thus providing accuracy in depth control). The windrows were then to be collected via the scraper. We found the type of soil and the head of soil available did not permit reasonable bowl fill factors.

The procedure ultimately utilised on the project involved fitting the scrapers with ultrasound depth detectors and direct cutting the soil by scraper. By managing the haul route and pick up locations of scrapers, no soil recontamination occurred behind the scrapers.

Our total plant fleet included:

• 3 No Caterpillar 631 scrapers
• 1 No Komatsu WD600 rubber tyred dozer
• 1 No Caterpillar 16G Grader
• 1 No Volvo L90 Loader (to tow water tank and miscellaneous loading)
• 1 No Samsung 20T rubber tyred excavator (for vegetation clearing and pit works)
• 1 No Volvo RO/RO truck (used as water tank and haulage of RO/RO bins)
• 3 No Toyota Manhauls for carriage of personnel, and testing purposes

The Contractor had a responsibility to design and construct the necessary modifications to plant and equipment to ensure a safe environment existed for operators within a cabin surrounded by a potentially radiologically hazardous environment. The objective was for plant cabins to be radiologically safe, thus avoiding the need for operators to wear personal respiratory equipment.

The criteria that needed to be met for plant modifications included:

• modify soil transfer vehicles to reduce dust generation. This included corrugated iron canopies over the scraper bowls.
• modify cabins to provide absolute levels of dust exclusion
• provide central servicing points

Never in our company's history had we faced the challenge posed by the Maralinga project in relation to plant modification requirements.

To achieve these criteria the following processes were adopted. All modifications were designed by Thiess in conjunction with our specialist suppliers and incorporated into a design manual for each item of plant.

• Remove existing cabin
• Structurally reinforce or rebuild cabin to allow integrated shell capable of withstanding high positive internal pressure
• Build new doors to "submarine" standard and provide emergency exit facility
• Seal cabin to "submarine" standard
• Provide high strength glazing to avoid breakage in event of impact
• Provide cabin ventilation and pressurisation which achieved absolute standard particle filtration. The components of this system included new air intake, positive displacement blower, HEPA filters, integrated ducting and isolating valves.
• Specialised cabin instrumentation with warning alarms in the event of cabin pressure drop.
• Remodify the fuelling, oiling and greasing points on the equipment to allow easier servicing by field staff and thereby minimise the exposure of these personnel to radiological hazards.
• All modifications to be fully tested and witnessed by Client to ensure compliance with pressure requirements and mechanical requirements. All items of plant were certified by Client as having achieved modification standards. The average costs of modification of the cabin's doors and providing the specialised filtration exceeded $130,000 per item of plant.

After 14 months field operation, the results have demonstrated the suitability of the modifications with zero incidence of cabin pressure failure and no ingress of particles to the operators cabin. Minor problems were encountered early in the project, but these were easily overcome. The most notable of these was cracking of the stainless steel HEPA filter housing.

The project involved the radiological cleanup of three nuclear test sites - Taranaki, TM 100/101 and Wewak.

The scope of work items involved in the project included:

• excavation of three burial trenches with a total volume in excess of 600,000m³
• clearing of vegetation from over 230 ha.
• collection of nearly 400,000m³ of soil, covering 3,400,000m² of ground
• sweeping and vacuuming of over 200,000m² of rock surfaces
• backfill of burial trenches with some 300,000m³ of material
• excavation and burial of 19 category 3 debris pits, and 80 category 2 pits.

The following Table I details the breakdown of work at each of the nuclear test sites.

The total project value at completion was $18.3 million, which represents a cost of $45.70 per metre of contaminated soil collected and buried.

Radiological cleanup criteria, as detailed in the following Table II were achieved or bettered at all locations.

The project was executed with all key parameters overwhelmingly successful:

• no radiological incidents
• project free of lost time injuries (over 550 days worked)
• project was completed 14 months ahead of client's program
• project completed for less than awarded tender value
• clean up results better than anticipated by Maralinga Rehabilitation Technical Advisory Committee (MARTAC) were achieved
• enhanced relationship with local aboriginal groups

Instrumental to the success of the project was teamwork. We recognised that this project would not be successful by our efforts alone - it needed a committed team approach by Thiess; the Health Physics Provider CH2MHill; and the Client and Project Manager

Partnering was utilised on the project, and whilst I wouldn't like to attribute partnering as being solely successful for the project outcome, it was certainly influential in focusing the team in times of conflict.

The Health Physics regime was critical to the project's success, and to this end we need to single out the efforts of CH2MHill's team. They worked with our employees to provide them with certainty in terms of their safety, and carried out the necessary monitoring of employees such that minimal possible disruption to productive time resulted. Our assumptions at time of tender regarding allowable production time of approximately 6 1/2 hours in a 10 hour day were achieved.

The biggest issue that arose on the project was the interpretation of the water requirement for dust suppression. Achieving the optional position between minimal dust and no mud required trial and error in the harsh climate conditions, and tested the strength of the team's relationship.

The success of the project is no doubt due to the willingness of members of all organisations' staff to co-operate in a strong team environment.

The Maralinga Rehabilitation Project will be judged an extremely successful project and a world benchmark in large scale radioactive soil removal.

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