The scope of the works included the construction of 18 (eighteen) gabion structures (groynes) in the Elandskloof River over an approximate distance of 2000 metres. The works, as described, formed part of the Disaster Management Programme for the farm Elandskloof situated between Helderstroom and Genadendal within Theewaterskloof Municipality, Western Cape.
Work included in this contract involved the following construction:
1. Construction of a temporary channel and berm to temporarily accommodate river flows and protect the construction site.
2. Clearing of the river banks of alien vegetation.
3. Excavation for construction of gabion riverbank protection structures (i.e. groynes).
4. Construction of gabion riverbank protection structures using selected stone fill from the riverbed, including continued dewatering of excavations.
5. Backfilling of excavations.
6. Excavation and shaping to rehabilitate the river channel.
7. Construction of the terraces between groynes using material excavated from the river channel.
8. Trimming and finishing off river channel and fill slopes.
NATURE OF GROUND AND SUBSOIL CONDITIONS ON SITE
The construction of groynes in an environmentally sensitive riparian zone is specialized work that requires competent human resources that are adequately skilled in working with heavy and dangerous machinery/materials in aquatic and undulating conditions. The safety of all staff is of paramount importance in the implementation of the project.
This project entailed working within the Elandskloof River channel and the riverbed consisted of deep gravelly layers containing sand and silt with cobbles and boulders, interspersed with occasional layers of peat. Excavations were required with constant water ingress due to the permeability of the founding material and existence of a high water table. The side walls of the excavations slumped and collapsed due to the unstable nature of the saturated founding material, which required dewatering while constructing the lower layers.
Casidra, on behalf of Department of Agriculture
Started: 20 November 2018
CASIDRA SOC LIMITED