The two ponds were filled with seawater over a period of six days. Difficulties were initially encountered with leaks in the pipeline due to shifts in the pipe and improper solvent welding at the joints. These problems were corrected by reinforcing the pipeline and replacing the faulty joints.
Each pond required approximately 15 h (9.3 l/sec) to be filled, which is within the design specifications of 18 h (7.6 l/sec). The diesel pump, however, may not be able to supply the eventual total requirement of 11 l/sec to the laboratories and ponds, especially when the suction line is lengthened and the seawell installed. For the permanent sea-water pumping system it is recommended that a larger pump or two pumps in parallel be used.
During the initial filling period the sand overliner appeared to be stable and remained compacted on the pond sides and bottoms. The anti -erosion skirts of plastic and pavement stones were successful in preventing sand from sliding down the pond slopes during the test period. Problems are anticipated, however, with the skirt materials in Pond A. Where the lengths of polythene plastic have been attached together they are coming apart due to the efect of the solar heat on the tape. Continuous lengths of polythene along each side of the ponds would have been preferable, however the supplier was able to provide only small pieces of polythene at the time of installation. The pavement stones are already shifting and a few have begun sliding down the pond slope. This problem can be remedied by extending the width of the pavement stone skirt to the bottom of the pond. Both of these systems are being tried as an alternative to the more expensive PVC and vinyl plastics. Alternative cost effective materials should be searched for from overseas suppliers if it becomes necessary to replace the polythene or pavement stones.
The water level in the ponds was regulated by internal standpipes. The standpipe was not cemented to the drainpipe but, provided all joints were sung, there was no leakage. With all the splashboards in place in the monk, the standpipe was removed from Pond A. The water flow was regulated by gradually removing each of the splashboards so that the water did not overflow the drainage area. Since the drainage channel had not been comppleted to the sea, the water was diverted to a low-lying area adjacent to the ponds. This area, however, overflowed midway through the drainage operation, which forced all activities to cease. It is calculated that a pond can be completely drained in 3 to 4 h. There is some leakage between and around the splashboards so that the water level in the ponds should be controlled by the internal standpipe. Where the water from the monk enters the drainage area, the concrete section should be increased in height to prevent overflow, There is a small flow of water along the outside of the monk wall. It is suspected that there is a leak in the monk itself, possibly where the PVC pipe enters the monk.
