SAN JUANA federal judge has ordered a Greek shipping company to pay the Commonwealth government over $6 million in environmental damages for a 1973 oil spill.

Government lawyers claim this is the first legal decision ever to award damages for environmental destruction. Companies have until now only been charged for cleanup costs.

Pedro Gelabert, director of Puerto Rico's Environmental Quality Board, claimed the decision should reduce the possibility of spills. Insurance companies will now be more reluctant to insure old and faulty vessels, he said.

The shipping and insurance companies are expected to appeal the ruling to the First Circuit Court of Appeals in Boston.

The spill occurred March 18th, 1973, when the 16,000 ton S.S. Zoe Colocotronis ran aground three miles south of Puerto Rico's south coast with a cargo of Venezuelan oil. To free the ship, the captain ordered the dumping of about 1.5 million gallons of oil.

The Colocotronis is owned by Colocotronis brothers of Greece and Great Britain and is insured by West of England Ship Owners Mutual Insurance Association.

U.S. District Court Judge Juan Torruella found that the grounding was caused by lack of proper charts, poor navigation, defective navigation equipment, failure to post a bow lookout, and an incompetent crew.

The oil slick drifted west into a half-moon shaped bay called Bahia Sucia and settled beaches and mangrove areas.

Bahia Sucia is Spanish for "dirty bay" because they bay catches debris from ocean currents.

Torruella devoted several pages of his 45-page opinion to a description of the bay's animals and environment. "At the time of the casualty, Bahia Sucia was a healthy, functioning estuarial ecosystem," he found.

The Coast Guard was alerted to the spill and began a cleanup operation March 19tH. Some 750,000 gallons of oil were pumped out in about 10 days, and manual cleanup continued for five months, but oil residue remain.

The worst environmental damage was caused to about 23 acres of mangrove, a breeding ground for marine animals, the judge found.

Torruella calculated damages based on the testimony of marine experts.

The spill killed an estimated 92 million animals, he found, whose prices in a biological supply laboratory vary from 6 cents to $4.50. Accepting the lowest replacement cost, the judge assessed damage at $5,526,583.20.

In addition, the most effective way to restore the area would be to replant 23 acres of mangrove, Torruella ruled, at a cost of about $487,500.

The shipping company has already paid the Coast Guard $677,660 for cleanup costs. Torruella also assessed $7,500 in fines, payment of 6 percent interest from the issuance of the 1974 cleanup bill until it was paid in April, 1978, and an additional $78,000 in cleanup costs to the Commonwealth government.