Plans to initiate Caribbean cruises at a pier in Alexandria starting this fall were jeopardized last night when the City Council balked at voting as much as $240,000 to dredge the Potomac River.

The council did approve spending $35,000 to improve the deteriorating pier at the Torpedo Factory, an old waterfront building where the cruise ship Caribe would dock.

City Manager Douglas Harman told the council that the Caribe's owners have said that unless the river in front of the pier is dredged to a depth of 21 feet at city expense, the ship will not dock there next November as planned.

Harman put the cost of dredging and installing additional pilings at up to $240,000 and noted that the city would receive only an estimated $1,164 in direct tax revenues generated by the ship. He recommended against the expenditure.

The improvements to the pier will make it safer for the private pleasure boats and high school rowing teams that now use it.

Council member Nicholas A. Colasanto said following the council's refusal to approve the higher amount, "You've missed the boat. We must restore the riverfront to its former grandeur."

Council member Robert L. Calhoun replied, "we would be subsidizing one of the most heavily subsidized industries in the country, the maritime industry. It is a scandal." Calhoun was the only member to vote against spending the $35,000 to improve the pier.

Last year, the Caribe docked in Alexandria for the first time. The ship's captain later complained to city officials that the river's depth at the pier was too shallow for safe maneuvering.

The council accepted without comment a report from the city's Human Rights Commission stating that children in the school system's preprimary program for children aged 3 to 6 attend classes in a racially segregated atmosphere.

"No effort is being expended to prepare (preprimary) children for the integrated setting of the public school education and, similarly, no effort is being made . . . to encourage preprimary programs to provide that setting," the report said.

In other actions, the council voted to make permanent the residential parking permit program that has been in effect in the city's Old Town area since Jan. 1 and to endorse proposals to begin Sunday Metro subway service and to impose a 10 cent transfer charge between the subway and buses at all stations.