ROOIWAL PIPELINES AND 20Mℓ ANNLIN RESERVOIR
Due to the extensive current development as well as future planned developments of the Wonderboom A.H. and Annlin areas north of Zambesi Road, the current water supply to this area has become inadequate to accommodate the increased water demand, and it was required to install a new main delivery pipe to the area. As part of the augmentation program a new Annlin reservoir had to be constructed.
Due to restrictions on the site as well as environmental constraints the position of the reservoir had been fixed and as a result the reservoir is partially founded on a syenite dike. This dike, running north-south, dips at 70° to the west and is ± 60m wide.
The problem was solved by placing the reservoir on 48 piles of varying depths which supports the roof, wall and floor (through deep transfer beams ) to the piles.
The reservoir has a volume of 20 000m³, a diameter of 42m, a flat slab reinforced concrete roof and prestressed concrete cylindrical wall.
To provide for differential settlements, all articulated joints are sealed with polyurethane bandage sealants. An under floor pressure relief and under floor leak detection system is installed to ensure that any malfunction is picked up and located.
The contract also includes a 900mm diameter link feeder from the Wonderboom Reservoir close by as well as a 900mm supply pipe to the adjoining service area and in the process a portion of the Rooiwal Reservoir Feeder line is replaced.
The head differential between the two Reservoirs (± 60m) is utilized by installing a hydropower unit of ± 60kW capacity. This will be sufficient to supply power for on-site use as well as surplus to be fed into the 33kV Tshwane Grid.