Scope of Services:

Provision and installation of sheet piles to protect an excavation at the intake structure of a waste water treatment plant. Sheet piles of profile GPU 17a- 600 hammered to full 11.8m length or to refusal in a rectangular wall. 

Location: Bugolobi, Kampala, Uganda 

Completion Date: September 2016 

Main contractor: Roko Construction Ltd. 

Client: National Water and Sewerage Corporation (NWSC) 

Part of the Nakivubo waste water treatment plant. The intake structure for the treatment plant featured a low lying sump pit. The bearing piles had already been installed by East African Piling from a temporary platform at a higher elevation. The base of the sump was some 5m below the platform and the site was too constrained for a battered excavation. The main contractor, Roko, elected to install a sheet pile wall to protect the excavation. 

EAP diverted previously ordered sheet piles to be delivered directly to the project in order to expedite the works. EAP mobilised a 50T telescopic boom crane and 2.5T hydraulic drop hammer complete with power pack in order to install the piles. EAP constructed a bespoke piling frame to align the piles prior to hammering. 

The ground conditions were soft for the first 2 or 3 metres only after which they became very stiff. Corner piles were prefabricated off site. Along two sides of the sheet pile wall the sheets met refusal before the full 12m length was installed. For the remaining 2 sides the contractor instructed EAP to predrill the ground into which the sheet piles were to be installed. EAP mobilised the lightweight Soilmec CM50 drilling rig to pre-bore along the line of the sheet pile wall. 

The remainder of the sheet piles were installed without difficulty. The contractor later mobilised a team to complete the walling of the coffer.