Westport, Sept 7 NZPA - Solid Energy has signed an agreement with its new alliance partner Downer EDI, the miner announced today.

The Stockton Alliance officially takes effect on October 3.

Solid Energy also announced a further $75 million investment in Stockton Mine, bringing its total investment in the mine this year to about $200m.

The alliance agreement was signed by Solid Energy chief executive Don Elder and Downer EDI Mining chief executive David Overall.

Dr Elder said he was extremely pleased to confirm the deal had been struck.

The Stockton Alliance was a new, innovative approach to mining in New Zealand, he said.

The alliance would run for up to five years.

Solid Energy chief operating officer Barry Bragg said the alliance could now start making firm employment offers to prospective staff.

They expected to have up to 650 workers, employed directly or seconded from Solid Energy and Downer.

Mr Overall said the company was delighted to be part of the alliance.

"Solid Energy is a new client for us, and New Zealand is a new market for our mining business."

Solid Energy had placed orders for $75m of new heavy mining equipment, which would form the core of the new mining fleet.

Decisions about additional equipment would be taken next year when plans for mining the Millerton and Cypress areas of the mine were more advanced, Mr Overall said.

Meanwhile, the Engineering, Printers and Manufacturing Union, negotiating on behalf of Stockton mine workers, said it had reached a tentative agreement with the state-owned miner.

EPMU energy spokesman Ged O'Connell said significant progress was made in last week's mediation with Solid Energy.

Talks between the two had stalled, and mediation was entered last Monday, finishing on Saturday.

Mr O'Connell would not release details of what the two had agreed, saying members had to be told first, but a formal agreement was being drawn up.