Long Bay murk sets off alarm bells again

Part of the Long Bay-Okura Marine Reserve on Sunday after the rain. Photo / Paul Shallard

Clay washed off a housing development's earthworks has for the second time in a month raised fears for the Long Bay-Okura Marine Reserve, 25km north of downtown Auckland.

After Sunday's storm, residents called the Herald to report a muddy stain over the waters of the reserve, adjacent to Long Bay Regional Park.

Paul Shallard took pictures of a "clay stain" from the mouth of a creek which runs into the reserve.

He estimated the discoloured water was 0.5km wide off the coast and stretched for 2.3km along the coast to opposite Waiake Beach-Torbay.

Long Bay-Okura Great Park Society convener Chris Bettany saw the plume of sediment coming from the Awaruku Stream as well as run-off from the cliffs.

"It was a choppy sea and a high tide, so it was not as dramatic as after the heavy downpour on December 19 when the stain was very yellow."

Clay washed into the stream then after part of the system to prevent soil run-off from the 226ha residential development failed. The rain was so heavy that two diversion bunds (walls) failed and sediment pond over flowed.

Auckland Council resource consents manager Heather Harris said the pond fully complied with the resource consent for the first stage of Todd Property Group's development.

Company spokesman Sifa Taumoepau said there was no breach to sediment containment devices despite last weekend's rain. "We have taken a belt and braces approach to meeting these stringent conditions."

Hibiscus Coast and Bays Local Board chairwoman Julia Parfitt said she called out council inspectors on Sunday and Monday to check the development site.

"I was assured that none of the conditions of the resource consent was breached and ponds were built to high technical standards.

"There is a high level of concern, especially because this has been a highly controversial project, but I have never had the same level of interaction with a development company as this one. Todd is working closely with the council and keeping the local board informed."

The consent conditions for the first stage were approved by the Environment Court.

Resident Robert White said environmental groups thought the conditions were inadequate and had predicted the sediment control system would overflow in heavy rain.

"It's very serious because it puts sediment into a marine reserve and it's happened twice in a short time since earthworks began early October."

He said that after the December 19 failure, the developer responded quickly to fill the breach and then to raise the height of the wall.

"But this is a sticking plaster approach rather than a scientific one. It should have been done before.

"The sediment ponds, if working properly, should look clear on the top, instead of looking muddy and murky."

The Department of Conservation controls the marine reserve, which was established in 1995. Its rock pools contain more types of shellfish than others of the inner Hauraki Gulf.

DoC biodiversity manager Phil Brown said the threat of sediment was part of the department's argument for not making the land behind a marine reserve an urban area.

"We have concerns and we are keeping an eye on it."