Overseas success for BAM Ritchies
Specialist blasting and geotechnical contractor involved in major contracts in Tanzania and Sri Lanka.

BAM Ritchies, specialist blasting and geotechnical contractors, have been involved throughout 2009 and into 2010 on two major overseas contracts managing drill, blast and crushing operations. These are the rehabilitation of the Tanzam Highway in Tanzania and the construction of a fisheries harbour at Dikkowita, Sri Lanka.

Rehabilitation of Tanzam Highway

The €75 million contract to rehabilitate and upgrade approximately 150km of the existing Tanzam Highway from Iyovi to the foot of Kitonga Gorge and from the top of Kitonga Gorge to Iringa is being undertaken by BAM International and Danish partner Per Aarsleff. The seven kilometre steep Kitonga Gorge section is not included in the project as it was reconstructed in recent years.

The Tanzam Highway is the main transport route from one of Africa’s largest ports, Dar Es Salaam, leading into Central Africa, mainly Zambia and the Congo. The start of the project road is approximately six hours drive west of Dar Es Salaam.

Works include pavement recycling, mechanical stabilization, strengthening, shoulder pavement construction and traffic safety improvements. The road section of this project was initially constructed in the 1970s with an asphalt concrete surface supported by either a cement stabilized or crushed stone base and natural material sub-base.

For the aggregates supply element, BAM Ritchies carried out pre-tender and post-award site investigations of potential quarry sites along the 150km length of the planned project section. It was the intention to develop two quarries to provide all aggregates for the project, one east and one west of Kitonga Gorge to negate the requirement to haul materials over the gorge. The consequential test results confirmed that the available rock was a granite-type material that is found throughout Africa.

Quantities and specifications of quarried rock required for the project were:

Base course:

• crushed rock class CRR with grading CML1.7 0-40mm – 750,000 tonnes

Aggregates for asphalt:

• 0-4mm grading – 125,000 tonnes
• 4-9mm grading – 121,000 tonnes
• 9-15mm grading – 22,000 tonnes

A total product of over 1,000,000 tonnes was required within a crushing programme of 24 months. The current crushing target is 50,000 tonnes of product per month.

BAM Ritchies investigated available plant suitable to specific contract needs and investment restraints. The following mobile equipment was sourced, purchased and shipped from the UK to Dar Es Salaam:

• Primary crusher x 2 - Pegson 100 x 800 single-toggle jaw
• Secondary crusher - Pegson 1300 cone Maxtrak
• Tertiary crusher - Pegson 1000 cone Maxtrak
• Triple-deck screen - Powerscreen Chieftain 2100
• Double-deck screen - Powerscreen Warrior 1400

An Ingersoll Rand ECM drill rig and compressor have also been transferred from a previous BAM International contract in Ghana, to supplement a similar drill rig and compressor supplied by BAM Ritchies, along with all drill rods, bits and consumables through their Glasgow office. Drilling is carried out using 2 3/8in reg. rods with down-the-hole hammer fitted with 115mm COP44 button bits.

BAM Ritchies are also carrying out all shot firing on the project with all explosives stored in a purpose-built licensed site magazine. In the first 11 months of the contract some 1,900 holes have been drilled: a total of 24,582m with an average depth of 13m, yielding 568,680 tonnes of blasted rock.

Initially, a quarry was opened up at Mazombe to service material requirements for the section of the works west of the gorge and development of the second quarry at Ilindi at the eastern side of the gorge is ongoing. Rock from Mazombe has been processed within the quarry whilst at Ilindi the rock will be primary crushed at the quarry and transported down to the new road where it will be stockpiled ready for the existing secondary plant at Mazombe, which will be moved down on completion of the western section of the road in spring 2010. Rock from Ilindi will be used primarily for base course.

All asphalt for the project will be manufactured at the Mazombe quarry and sufficient stockpiles of crushed rock will be left for the tertiary crusher to produce the required aggregates.

To date some 350,000 tonnes have been put through the primary crusher at Mazombe producing over 205,000 tonnes of base-course and 95,000 tonnes of asphalt and concrete aggregates.

The project is forging ahead with some 35km out of the 150km finished road completed to date. The planned completion of the project is early summer 2011.

Dikkowita fisheries harbour

BAM Ritchies are working with their Dutch sister company BAM International on a design and construct contract for the Dikkowita fishery harbour project in Sri Lanka. The new facility will be the main fisheries port on the west coast of Sri Lanka and is located some 10km north of Colombo.

The new harbour will replace the existing inadequate berthing facilities at various locations, allow for future fishing fleet expansion and provide proper facilities for both local consumption as well as export.

The project will provide:

◦two breakwaters forming the seaside part of the harbour
◦quay walls at the land side of the harbour
◦piers for off-loading ships
◦lay-by piers for ships
◦wave-energy dissipation beach
◦land reclamation with slipway within the harbour plot
◦landfill at the building area
◦processing and service buildings
◦infrastructure for the works
◦dredging of the harbour to the required depths
◦drill and blast operations to the harbour mouth
◦roads / pavement with storm-water drainage
◦an access road with bridge.

BAM Ritchies are involved in managing the procurement and delivery to site of suitable rock to form the breakwater and fill areas, and the drill and blast of the harbour entrance.

This involvement also includes supervision of a detailed offshore and onshore site investigation prior to the main works commencing.

An existing quarry was located and materials were tested in both Sri Lanka and the UK to confirm compliance with applicable standards. The quarry, which is situated 50km from the project, was in the course of development to provide aggregates for local contractors. Under BAM Ritchies supervision the quarry has been totally redeveloped to meet the project’s specification and programme demands.

The requirements for the harbour include a complete range of materials to be extracted, ranging from basic core material to heavy armour blocks. There is no requirement for any crushing of quarry materials since all concrete aggregates for the project are being provided by other local suppliers.

The contract requires the supply of the following quantities of rock:

• Core layer: 0.5-500kg - 136,836 tonnes
• Filter layer: 60-300kg - 46,200 tonnes
• Armour stone: 200-300kg - 2,640 tonnes
• Armour stone: 300-1,000kg - 17,460 tonnes
• Armour stone: 1,000-30,000kg - 31,500 tonnes
• Total rock supply - 234,636 tonnes

Until a suitable track drill could be purchased and delivered, the quarry continued to utilize hand drills producing an impressive average of 1,400 tonnes a day. BAM Ritchies supervized daily blasting and segregation of blasted materials. Examples of key stones and the use of measuring devices ensured that the specified grading was maintained. Separate stockpiles of graded rock are kept at the quarry and delivered to site daily. The quarry has recently taken delivery of a new air track drill and production has been increased to 2,000 tonnes a day.

The main difficulty experienced on the project is transport. Currently the quarry has over 100 trucks delivering rock to site on a daily basis. Although the journey to site is only 50km, it is arduous, utilizing a road system that wasn’t designed for such deliveries. One-way trips can take up to 2h to negotiate and the quarry always has a few trucks in reserve to cope with the expected breakdowns. Around 50% of the total rock requirement has already been supplied.

So far the core fingers of the breakwater have been constructed and work now involves the placing of site manufactured concrete x-blocks and armour stone.

BAM Ritchies are currently mobilizing supervisory staff to manage the drill and blast operation to widen and deepen the natural entrance to the harbour formed between the existing natural reefs. A rotation drill head with associated drill consumables have been sent to Sri Lanka from Scotland to be fitted onto a local drill rig, which will drill from a locally manufactured platform fitted to a BAM International barge, normally being used on the site dredging operation. All works are on target to be completed early in 2011.

Contracts manager Alex Tiernan, commented: ‘These two contracts demonstrate the complimentary skills of BAM International and BAM Ritchies, when working overseas together on schemes with aggregate and armour stone requirements. They extend the track record of joint project delivery in a variety of developing countries for different types of infrastructure schemes.’

Article courtesy of www.agg-net.com - April 2010