The Guardians of Pautahanui Inlet (GOPI) are grateful for the opportunity to make a submission on this application. GOPI was established in 1991 with the primary objective to protect, foster and promote the values of the Inlet; especially its ecological values. Our interest in this application is in the potential effect of the proposed cleanfill on the water quality of the Pauatahanui Stream and the Inlet.
Any modification of land use from a vegetated state in the Inlet catchment has the potential to affect water quality entering the Inlet by
- increasing sediment runoff into streams from exposed soil;
- increasing erosion of stream banks from the increase in water flow and velocity due to decrease of the filter and friction functions of the plant cover;
- release of toxic contaminants.
These factors are all raised in the consultant's ecological assessment. Fortunately, the applicants appear to have responded positively to the recommendations and to the questions subsequently raised by GW. It would now seem that provided proper conditions are attached to the consents, and provided the Councils employ a rigorous monitoring regime for compliance with them, the potential dangers of this development will be reduced to an absolute minimum.
However, GOPI is concerned that this operation is scheduled for at least 10 years and that there will be significant changes to the site during that time. We request that the Councils pay particular attention to the following points.
- That the culvert/drain beneath the fill is designed to withstand the changes in pressure, etc, that will occur as the site fills.
- That the culvert/drain beneath the fill is designed to continue to be functional as a permanent drain beneath the fill site, bearing in mind the depth to which it will be buried may preclude easy maintenance and that the site is located in an area of constant small earth tremors. Blockage could cause a number of problems with water flow and ground stability that could lead to disastrous release of sediment into the Pauatahanui Stream and thus to the Inlet.
- That Councils are satisfied that the chronic presence of highly toxic ionic aluminium at the output and downstream over the 10 year time frame is unlikely to cause adverse affects on the fauna and flora of the stream and Inlet. We acknowledge that experiments confirm that it is unlikely that short term exposure to aluminium in these receiving environments is a problem; we are less confident that the risk of long term exposure has been established. The long term nature of this cleanfill site provides a significantly different situation to that of the relatively short period of the average subdivision development.
John Wells
Chairperson
