Thursday, 31 October 2013

Coral communities threatened by development in Hoi Ha

Introduction

This is a comment on Draft Hoi Ha Outline Zoning (OZP) Plan No. S/NE-HH/1.

Objections

When the Draft Hoi Ha OZP was being drafted it failed to consider three key issues:

1. The presence of coral communities in Hoi Ha Wan;

2. The threat to these coral communities from pollution, because the underlying geology will not support the use of on-site septic tanks and soakaway (STS) systems; and

3. The threat to these coral communities from sedimentation resulting from clearing land for development.

Coral communities

The coral communities in Hoi Ha Wan are the dominant feature of conservation and ecological significance in the area, yet the Draft OZP doesn’t mention this. You cannot consider the ecology, conservation or development of Hoi Ha without discussing the coral communities. Moreover, when the Hoi Ha Wan Site of Special Scientific Interest (SSSI) and Marine Park were being established, only two threats significant enough to cause irreparable damage to the coral communities were identified. These are pollution and sediment runoff from future development in the area.

Hoi Ha Wan Site of Special Scientific Interest designation document


Comments made at the opening of Hoi Ha Wan Marine Park



Threat to coral communities from pollution

The underlying geology in Hoi Ha village will not support the use of on-site septic tanks and soakaway (STS) systems to disperse untreated wastewater into the surrounding soil. The underlying surface sediment in Hoi Ha village comprises a mixture of alluvium, beach deposits and debris flow deposits. Such deposits are porous and highly permeable, allowing for rapid drainage.

Because of this, pollution will not be filtered, which will result in nutrient rich wastewater flowing into Hoi Ha Wan, leading to irreparable damage being caused to the coral communities there. It is important to note, two of the worst nutrient threats to coral communities are excess nitrogen and phosphorous, whilst two of the main nutrient products of STS systems are nitrogen and phosphorous.

Threat to coral communities from sediment runoff

At the same time, excavations undertaken during development will expose soil and sediment to the elements, which will disrupt the geologic continuum in the area. Because Hong Kong is naturally subject to heavy downpours of rain and extreme weather events, such exposure could lead to a massive single discharge of sediment or prolonged discharges of sediment into Hoi Ha Wan, smothering the coral communities. Hoi Ha Wan has a documented history of this. In the 1980’s, the loss of a coral community was recorded on the eastern shore of Hoi Ha Wan because of soil and sand runoff when trees and rocks were removed from the surrounding hills for reclamation of land at the Ma On Shan new town.

Comment

Because none of these issues has been considered in the Draft Hoi Ha OZP, appropriate assessments have not been made and no development should be allowed in Hoi Ha village until these issues have been properly considered and evaluated.

Petition 

If you want to object to the proposed development in Hoi Ha, please sign the petition here:

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