The on-again, off-again plan to resurface Canal Road is now on again, beginning in August, officials at the D.C. Department of Transportation said this week.

Last week, local transportation officials said the resurfacing of the busy commuter route was being postponed "indefinitely" and might not start before the summar of 1980, when construction and traffic jams on the parallel George Washington Memorial Parkway would be over. This week, D.C. officials said there had been a "snafu" in communications and that the work on Canal Road would begin in late August.

Five bridges on the George Washington Parkway will be resurfaced beginning May 1, which the National Park Service estimates will cause rush-hour traffic delays of up to an hour between Chain Bridge Road and Spout Run. About 60,000 cars now use the fourlane parkway each day, and many commuters are expected to cross over Chain Bridge to use Canal Road, which presently carries about 38,000 cars a day.

District officials insist the Canal Road project-expected to cost $1 million-will not add to the traffic jams created by the parkway construction. The Canal Road project extends from Foxhall Road at the edge of Georgetown to Chain Bridge.

A Park Service official said this week he foresees only a "minimal impact" from the Canal Road work, particularly since the worst parkway traffic tie-ups are expected during the first three months of construction and should have ended before the Canal Road work starts.

Canal Road will be kept open just as it is during rush hours, said the District's deputy transportation director, Bernard O'Donnell.This should mean the construction will have virtually no impact on commuters.

At other times, one lane of Canal Road will be kept open in each direction between Chain Bridge and Arizona Avenue, where the road is three lanes wide. Between Arizona Avenue and Georgetown, where the road is two lanes wide, one city-bound lane will be kept open at all times, O'Donnell said. However, the suburban-bound lane in that section of Canal Road may be closed frequently during construction.

The Canal Road project will take about one year to complete because the road's deteriorated curbs will be replaced and cold weather will delay construction during the winter, O'Donnell said.

In a related matter, the Fairfax County Board of Supervisors, upset by the traffic jams expected from the parkway work, sent a letter to the National Park Service this week urging that the parkway project be delayed until at least January when Metro is expected to open its Ballston subway station in Arlington. The supervisors said the subway station might ease the traffic load by offering commuters an alternate route into the city.

The Park Sevice, which has yet to receive the Fairfax request, has said the bridge repairs are desperately needed and noted that construction will done on double-shifts, allowing the work to be completed in 16 months rather than the more usual two years.