North Otago Irrigation Company chief executive Robyn Wells said ‘‘a stabilised form of gelignite'' was found on July 2 last year, as contractors laid a new foundation on the company's Black Point Rd pumping station to ready it for the installation of the first of four new motors of up to 2.8MW and pumps required for the $57million expansion.
The find delayed only the pumps' installation and had not interfered with the work to continue laying the 114km of pipes for the scheme, she said.
Shareholders and affected people were told about the incident, which Oamaru police and the bomb squad attended, though there was no wider public notification.
‘‘There was no secret about this event. We sent out emails to all our shareholders on the day, anybody that really needed to be informed,'' Mrs Wells said.
‘‘Anybody that could potentially need to know about this, they were all informed and were kept informed about what was going on.''
Work was stopped for a month for experts to assess the situation.
‘‘That's the kind of situation we want to make absolutely sure ... before we start work again on the site, that we have assessed the risks and that we have put all the appropriate controls in place ... the most important thing was to keep all our employees safe,'' Mrs Wells said.
The explosives would have been used during the 2005 construction of the pumping station.
The pump house will house four pumps, which will get water from the Waitaki River to the highest points in the scheme.
The first pump was installed in November.
In order to put the 24-tonne pump and motor into place, 20 anchor rods were placed 4m to 5m deep in the new 123-tonne foundation.
The irrigation company's technical manager, Ben Stratford, said, according to Network Waitaki, the motor from one pump, when in use, would require the same amount of energy as 800 houses, an equivalent of one-third the load of the Pukeuri meat works. That pump was scheduled to be commissioned in mid- to late-February.
Mrs Wells said the irrigation company's demand for energy was already high.
In December, the company delivered 7.2million cubic metres of water to shareholders. The electricity bill for the month was more than $400,000.
Once fully operational the expanded scheme would use two 2.8MW pumps and six 2.3MW pumps.
When the first four 2.3MW pumps were installed in the original part of the scheme in 2006, they were some of the largest in the southern hemisphere.
The company's expansion down the Kakanui Valley will cover 10,000ha, bringing nearly 25,000ha of farmland into the whole irrigation scheme.
