The proposed sediment removal, which was approved last week is a part of the Mei Te Vai Ki Te Vai (MTVKTV) initiative launched in 2017.
The aim of MTVKTV is to improve the water quality of the lagoons in Rarotonga and Aitutaki. Large quantities of nutrients flowing into the sea are believed to be responsible for the unwanted presence of seaweed and algae in and around the Muri Lagoon.
The aim of the project is to increase water movement throughout the Muri Lagoon, by removing excess sediment that has built up near the mouth of the Vaiterenga Stream. It is hoped that this will help to flush away excess nutrients. The nutrients are contributing to increased seaweed growth in the lagoon. It is hoped that the removal of this material will further reduce the presence of excess nutrients and slow the growth of seaweed.
The removal of sediment has been determined by the MTVKTV environmental specialists as an “early measure” to improve water quality conditions within the Muri Lagoon. Priorities for early measures were determined through a series of workshops held in Muri throughout 2017.
Other possible early measures include the offsite disposal of wastewater, regulating onsite wastewater treatment, regulating chemical use, and reducing the amount of sediment and nutrients entering the lagoon.
In addition to the planned sediment removal, the beach by Nukupure Park will also be replenished with planting and rock stabilisation taking place. The amount of sand needed to replenish the beach will determine how much sand will be removed from the mouth of the Vaiterenga Stream. The Environmental Impact Assessment completed for the project estimates that it will take no longer than a month to complete the planned work. The permit granted is valid for 12 months.
The Cook Islands Port Authority also intends to undertake similar work, having had their Avarua maintenance dredging project approved last year. The proposed dredging aims to restore the harbour berthing area to a depth of up to 1.5m by removing around 1750 cubic metres of material with diggers.
The purpose of the project is to meet basic infrastructural needs, whilst increasing the safety of all water users. It is suggested that by having a more accessible wharf, Rarotonga will see an increase in tourism and water sports activities by providing easier access for boat moorings etc.
The coral sediment build-up in the harbour has hindered use of the wharf for over two years and it is believed the sediment build-up is due to the construction of Constitution Park.
The dredging will apparently help to restore the harbour back to its “original” state. The boat ramp and slipway will be reinstated and the loading dock will also be reinstated to ensure the ease of loading and unloading goods.
Manager for the Advisory and Compliance Division of the National Environment Service, Vavia Tangatataia says he is unsure why the work has not yet begun at Avarua. It is estimated that it will take just two or three days to complete the project.