Subsidence Unsettling

Posted by Gold FM on 24/12/2012

subsidence

We received two telephone calls on Friday morning telling us that a Waihi Ward Councillor had 'door knocked' 5 houses in Gladstone Road telling the residents that Newmont Waihi Gold would be offering to buy their homes due to subsidence. We were also told that homeowners at one of the properties came home from a trip away to find movement in their house that could cause it to be unliveable.

See photos of damage that has occured on the walkway between Walmsley and Gladstone Roads below.

There are also rumours circulating that Newmont hit a 'void' while drilling on Walmsley Road earlier this year and that another void could have been hit when they drilled at the Waihi East School.

Six weeks ago some ground settlement issues became evident between 47 and 53 Gladstone Road. When the Council and Newmont Waihi Gold became aware of these movements a monitoring programme was put into place to assess the extent and speed of the settlement.

As part of the on-going monitoring some cracking on the east side of Walmsley Road adjacent to the houses became evident as did some cracking across Gladstone Road and around 48 Gladstone Road.

The ground settlement appears to be restricted to these areas and we've been told extended monitoring is showing no ground movement beyond those areas already identified.

The monitoring of the ground movement over an extended area will continue over the short and medium term.

While there is no record of any underground mine workings under the affected area the Council arranged for a geotechnical drill hole to be undertaken to assess if the cause of the event could have been a sinkhole into old underground workings. The drilling indicated that no voids existed below the area and that a sinkhole could largely be discounted.

The affected houses have been assessed by structural engineers and have been assessed as not being at any risk from structural damage. Further structural checks will be undertaken on a regular basis.

The specific cause of the ground settlement has not been identified and a staff working party consisting of representatives from the Hauraki District Council, the Waikato Regional Council and Newmont Waihi Gold will be formed to undertake the investigations into the probable causes of the settlement. This working party will commence work early in the New Year.

Gold FM spoke to Hauraki District Council Engineer Ken Thompson this morning who confirmed that there is something happening to five properties in Gladstone Road, in varying degrees. He confirmed alternative accommodation costs will be met by Newmont Waihi Gold who will also purchase the properties at market value. He said one of the houses in particular would possibly be 'uncomfortable' to live in but it is not unliveable. The doors and windows are sticking and some can't be opened.

Examinations showed that residents can decide when to move, unless anything changes, Ken Thompson said. The properties are being monitored and if it looks like further subsidence is occurring and escalating that could change. At this stage it's ok for the residents to stay in their homes through the Christmas period if they wish to as there is no urgent need to move at present, Mr Thompson said.

Mr Thompson says the Council is investigating the possibility of the damage being caused by the amount of fill used in an old tramline prior to the subdivision.

We asked Newmont Waihi Gold for a response last Friday but have not heard anything yet.

We received a Press Release the Hauraki District Council is sending out today that reads:

Press Release

From:

Langley Cavers, Chief Executive

Date for release: FOR IMMEDIATE RELEASE

Subject:

Local Residents affected by ground settlement – Gladstone Road

Residents in Gladstone Road, Waihi, can rest assured recent ground settlement, which has damaged five properties on the street over the last six weeks, is not caused by a sinkhole, similar to that which appeared on Barry Road in 2001, says Hauraki District Council Chief Executive Langley Cavers.

“No old workings have been identified and current monitoring of the ground movement does not show any ground movement in neighbouring properties (to those affected). The movement appears very localised at this stage” he said.

The Council has arranged for structural engineers to inspect the damaged properties, assess their structural integrity and make recommendations on whether there are any immediate structural safety issues requiring residents to be relocated.

The safety of residents is paramount and the Council is very supportive of Newmont Waihi Gold’s (NWG) offer to pay for the relocation of the residents from the five affected properties and meet all costs for this. The Council also supports the offer made by the Company to purchase any or all of the five affected properties at the pre-event market value and to meet the meet the costs of these sales.

The Council and NWG are currently investigating the causes of the ground movement.

District Engineer Ken Thompson says monitoring has shown the area of ground settlement appears to be restricted to the five houses but ongoing monitoring over an extended area will continue to ensure that any further ground movement is identified

“The investigations into the ground settlement would focus on the likely reasons for its localised nature and for it to be appearing at the present time in an area that has been an established residential area since the 1980’s,” he said.

Mr Cavers says the Council understands residents will be concerned about the immediate impacts of the ground movement, the possible need to relocate, and the longer term effects on their properties.

“I can reassure residents the Council and the Company are moving quickly to give them as much certainty as possible”.

Affected residents will be kept informed of developments.

END

For further information please contact Ken Thompson, District Engineer, Phone number 07-862-8609 (or 0800-734-834 from Waihi); Email address kent@hauraki-dc.govt.nz

Damage occuring to the walkway between Walmsley / Gladstone Roads