By ERWIN CHLANDA
“Stormwater is no longer the enemy.”
That, in a nutshell, lies behind the deal between the Town Council and the NT Government over stormwater management in Kilgariff.
So says a spokesman for the Department of Lands, Planning and the Environment in Alice Springs, reflecting the government’s iron determination to press ahead with the project in a bid to end the debilitating residential land shortage.
Prices of developed blocks will have a mandatory ceiling averaging between $160,000 and $180,000, bringing homes to within the scope of the $550,000 Build Start scheme, says the spokesman.
The department also gave the Alice Springs News Online access to a 100 page report completed this year by AEC Environmental Pty Ltd commissioned by the government, following rumours that the land is contaminated by chemicals including Agent Orange.
The report says: “All laboratory test results were reported at below the adopted assessment criteria and/or laboratory limits of reporting.
“There is no indication from the data we have collected to indicate Agent Orange was used and/or is present at the site.”
The report relied in part on the analysis of soil samples taken from 15 locations along fence lines and tracks where it is acknowledged that pesticides and herbicides had been used.
Kilgariff seems now set to act in tandem with softening prices of existing houses to bring home ownership in Alice Springs again within reach of many more people.
Stormwater to seep into soil
The spokesman says the issue at Kilgariff is about what to do with stormwater. The flat site is unsuitable for deep drains and buried pipes such as are required by Town Council planners. Instead, water will be moving across the surface, and encouraged to seep into the soil.
He says rather than taking water away from the site, and following the lead from other land developments around the nation, the department has found a way to put stormwater “to some extent” to good use around Kilgariff, and yet adequately drain the suburb.
“At low flows the design is expected catch water which will then infiltrate the ground over a period of one to two days,” says the spokesman.
There will be a shallow swale drain, some 20 to 30 metres wide, between the suburb and the Stuart Highway, turning east at the Colonel Rose Drive intersection and ending at a football oval at the south-eastern corner of the suburb. The swale drains will be wider further south as further stages are opened up.
All along that swale, and on its way to it, stormwater will pass through public open space as sheet flow, seeping into the ground.
In some places it will flow across internal streets and Col Rose Drive, but no deeper than is the case now, no more than a quarter of a meter in a Q100.
The swale drain will become open space for the public most of the time and be a buffer from the highway.
The spokesman says consultants Equatica developed the government’s drainage strategy and say “the plan is feasible” – and so do two other independent engineering firms.
The report is based in part on infiltration tests in dozens of locations throughout the development land, establishing a seepage rate of between 12mm and 37mm per hour, which means any surface water will be gone in a few hours.
Above or below the Q100 line?
All of the land of stage one, contrary to the council’s assertion, is above the one-in-a-100-year flood line (Q100). Much of it – if not all – meets the statutory requirement of being 300 mm above the Q100 line, and any blocks which do not comply can be made compliant with a few truckloads of soil, says the spokesman.
The 300mm height limit is set by the Building Code of Australia. In addition, after the 1988 floods in Alice Springs, it became a condition for the Territory Insurance Office to provide universal flood cover, although many older dwellings, in the CBD and the Old Eastside, for example, are below that line.
The spokesman says the Q100 map for the whole town is being re-drawn. The changes will be minimal, but the work, about 80% completed, is still pending peer reviews. The new data for Kilgariff are completed.
The agreement with the council for the government to accept responsibility for part of the Kilgariff project stems from the council’s apprehension about maintenance costs resulting from the storm water system novel to The Alice.
While the council is comfortable with the internal use of the system, it was unsure it would work when the flow gets to the swale drains at the periphery, especially during the construction phase when silt washing off bare land usually causes blockages.
To mitigate those fears the government has taken on the responsibility for the maintenance of the access road, and the entire network of swale drains for five years.
After this the council is expected to take on its usual responsibilities in the suburb, for roads and stormwater. (Electricity will be the responsibility of Power Water Corporation.)
“We know it’s going to work,” says the spokesman.
Developer bids are in
Meanwhile the commercial processes are under way for stage one which will have no less than 100 blocks.
The deadline for expressions of interest by developers has passed but the spokesman says the number of applicants will not be revealed before the bids are finalised. The selection of bidders to be invited is expected to occur this month.
The successful bidder will buy from the government the Crown lease of the land. Individual blocks will have freehold titles. At the average mandated sale price the developed land – including streets, water, sewage, power – will be worth around $17m.
The government will receive advice from the Australian Valuation Office about the value of the land, says the spokesman.
Development costs are estimated by independent sources at between $100,000 and $120,000 per block, which would leave the developer $6m minus what the government charges for his land. The government will pay $3.5m to the successful bidder for the access road, swale drain and sewage main to the pumping station.
The target for Kilgariff is 1000 blocks. Stage one is just 10% of that. Clearly, that gives the government great leverage to increase competition – at very short notice as the headworks are in place already. If speculators move in on stage one, stage two can be close on its heels.
IMAGES: Above: Kilgariff stage one clear of flood zone. Top: Swale drain at Araluen Park.
Footnote 1: The department has agreed to maintain access to the reports for the Alice Springs News Online and we will do our best to reply to readers’ queries.
Footnote 2: Reader Bob Taylor has suggested the report at this link is of interest.
Kilgariff $170K blocks, dept. on council stormwater deal
By ERWIN CHLANDA