Riverhead Town Supervisor Sean Walter has signed the letter of intent with Luminati Aerospace on the $40 million sale of the Enterprise Park at Calverton property.

Walter was out of town and unavailable for comment last week, but Riverhead Deputy Supervisor Jill Lewis confirmed Thursday that Walter signed the letter April 10.

“That means the clock is ticking,” Lewis said.

The Riverhead Town Board voted April 4 to authorize Walter to sign the letter of intent one week after town officials announced they struck a deal with Luminati, a Calverton-based startup, to sell the remaining 2,300 developable acres of the 2,900-acre EPCAL property, which was once a Grumman Corp. naval weapons facility.

According to the details of the letter, the company has 30 days to negotiate a contract now that the letter has been signed.

Luminati will also have a “due diligence” period of 90 days to perform all inspections and environmental and zoning studies on the property, as well as review all geotechnical, soils, wetlands and environmental reports, before deciding whether to proceed with the sale.

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Jeremy Freeman, Luminati’s director of public relations, said Thursday that the deal was progressing on schedule and that the company and the town are working to move toward the next stage of the deal.

Lewis added that town attorneys were “doing what they need to do” to prepare the sale for review under a qualified and eligible sponsor hearing during the 90-day period. That hearing, which will be open to the public, will determine whether the company is financially able to carry out its proposed plans.

If Luminati is found to be qualified and eligible, the town and the company will execute the sale within 10 days of that determination, according to the letter’s binding provisions section.

Luminati officials previously projected the deal, expected to close in August, would create up to 2,000 jobs — mostly technical and engineering positions — through expanding its operations.