Quarry Operations In Tanzania And Sri Lanka

18 August, 2010

Case studies on rehabilitation of the TANZAM Highway in Tanzania and the construction of a fisheries harbour in Sri Lanka

by Alex Tiernan, contracts manager overseas operations, BAM Ritchies

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

Rehabilitation of TANZAM Highway, Tanzania

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 7km steep Kitonga Gorge section is not included in the project as it was previously 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 6h 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 planned 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:

Basecourse:

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.

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

BAM Ritchies investigated available crushing plant to suit the 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 Maxtrak cone

Tertiary crusher:

Pegson 1000 Maxtrak cone

Triple-deck screen:

Powerscreen Chieftain 2100

Double-deck screen:

Powerscreen Warrior 1400.

An Ingersoll Rand ECM drill rig and compressor was also 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 the company’s Glasgow office. Drilling is carried out using 23⁄8in reg. rods with a down-the-hole hammer fitted with 115mm COP44 button bits.

BAM Ritchies are also carrying out all shotfiring 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 were 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, followed by development of the second quarry at Ilindi at the eastern side of the gorge. The rock from Mazombe was processed within the quarry while at Ilindi the rock is being primary crushed at the quarry and transported to the new road alignment where it is stockpiled ready for the existing secondary plant from Mazombe, which was moved down on completion of the western section of the road in spring 2010. Rock from Ilindi will be used primarily for basecourse.

All asphalt for the project will be manufactured at 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 basecourse and 95,000 tonnes of asphalt and concrete aggregates.

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

Dikkowita Fisheries Harbour, Sri Lanka

BAM Ritchies is working with 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 situated some 10km north of Colombo.

The new harbour will replace inadequate existing 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
Access road with bridge.

BAM Ritchies are particularly 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.

Their involvement also included 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. This quarry is situated some 50km from the project and 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 call for 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

1,000–3,0000kg – 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 per 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 schedule daily.

The quarry has recently taken delivery of a new air track drill and production has been increased to 2,000 tonnes per 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 hardly designed or adequate 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 on to 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 operations. 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 together overseas on schemes with aggregate and armour stone requirements. They extend the notable track record of joint project delivery in a variety of developing countries for different types of infrastructure schemes.’