Arrests of drunk drivers in Alexandria declined to a monthly low of 26 in July, prompting concern that staffing problems in the police department's patrol ranks may be undermining city efforts to fight drunk driving.

But a police spokeswoman said the drop in the arrests in July is probably an exception, noting there were more arrests for drunk driving in the first six months of this year than during the same period in 1986.

Paul A. Fearson, director of the city's Alcohol Safety Action Program, called the 26 arrests in July an "all-time low." He said this followed 61 drunk-driving arrests in June, the lowest monthly figure since August 1986, when 55 drunk drivers were arrested. Such arrests averaged 82 a month from January to June of this year, he said.

Fearson said police officials had cited a lack of manpower and an increased emphasis on drug law enforcement as reasons for the decrease in arrests when he raised his concerns with them last month.

"They are not able to do the surveillance necessary" for spotting drunk drivers, he said.

"July seems to be atypical," said police spokeswoman Lucy Crockett. "With the exception of July, we've done better this year than last year," she said, noting that arrests for the first half of this year totaled 494, compared with the 350 arrests in 1986 for the same period.

In all of 1986 Alexandria police made 849 drunk-driving arrests, police figures show.

Crockett said drunk-driving arrests in August are not yet tallied. "If we are experiencing a downward trend, we'll have to take a closer look" at the reasons for it, she said. Staffing problems in police patrols did not change significantly during July, Crockett added.

The Alcohol Safety Action Program offers rehabilitation classes to people convicted of drunk driving. By enrolling in the program, offenders may retain restricted driving privileges while their licences are suspended. The program is financed by fees paid by enrollees as well as by federal and state grants.