If there's one thing you can't fault the people at Consolidated Edison for, it's their optimism. The giant New York electric utility has been attempting for more than ten years to build a pumped storage power plant at the foot of picturesque Storm King Mountain on the Hudson River, and for more than ten years they've been delayed by environmentalists in and out of the courts.

They have yet to give up. This week, for the third time in nine months, Con Ed announced that it would begin construction on the Storm King plant within a month.

Con Ed's announcement came after the New York Public Service commission granted approval of a $200-million contract between the utility and three out-of-state construction companies, and it was this approval Con Ed stressed in its statements.

What the utility was not talking about was that three court cases remain pending against the Storm King project, and that Con Ed does not yet have all the land it needs--including 300 acres belonging to Harvard--to build the plant.

A December ruling by New York's Federal District Court requires that Con Ed obtain permits from the Army Corps of Engineers for dredging and filling at the riverfront, and that it hold hearings to allow public comment on the permits. The utility has filed for a permit, but at the same has appealed the court ruling.

Another suit, brought by Scenic Hudson Preservation Conference, a major opponent of the project, seeks to reopen the Federal Power Commission licensing procedures for the plant. The organization has argued that new evidence on potential damage to aquatic life in the Hudson resulting from the plant's operation, as well as economic and fuel factors, justify the motion.

And Harvard has stood by its decision, announced in October, not to sell any part of Black Rock Forest to the utility unless under "genuine threat" of successful legal action.

Asked whether these or other unresolved issues could present difficulties for Con Ed's predicted construction start, a spokesman for the utility said: "None that we can perceive."

But opponents have a different view. "Con Ed is always saying that it is going to begin the project," one New York environmentalist said this week. "Maybe if they keep it up long enough, someone will believe them."