(ANSA) - Rome, October 12 - The troubled ILVA steelworks in the southern port city of Taranto will have to reduce production by around 30% according to details of the draft blueprint for a much-needed environmental upgrade that emerged on Friday. The new environmental authorisation - details of which are being drawn up by a group of experts on the basis of recent inspections at the plant - would lower the production level to 8 million tonnes from the 11.3 million tonnes allowed under the old licence. Other measures reportedly contained in the blueprint include a ban on the use of petroleum coke, the start of procedures to shut down 6 of the 10 coke plants, covering conveyor belts and mineral deposits and renewing or carrying out maintanenace work on two of the blast furnaces. The steelworks are at the centre of a heated industrial dispute after a local preliminary-investigations judge ordered the partial closure of the plant due to long-running enviornmental and health concerns in July. Meanwhile on Friday one of three court-appointed custodians of the company made a visit to the steelworks to verify the state of progress in shutting down one of its blast furnaces in keeping with the court order. ILVA and the government have been trying to keep the plant in operation while the necessary upgrades are made.