The government's 23,095 truck drivers, laborers, skilled craft workers and other blue-collar employes here are due a catchup-with-industry pay raise that will go into effect Oct. 19.

Nobody knows what the amount will be. But an educated guess is that the blue-collar (wage board) hike will not exceed the 9.1 percent raise already set for 300,000 white-collar civil servants here.

Defense Department officials are completing a wage survey of 127 industrial and manufacturing firms here. They will use the salary data to determine catchup raises due local federal workers doing similar jobs. The exact amount of the raise will be announced on or about Sept. 15.

There is a good chance the blue-collar people will get less than the 9.1 percent, depending on local industry wage gains over the last year. But there is almost no chance the U.S. workers -- no matter what the survey shows -- will get more than 9.1 percent. Last year they got a two-step raise worth 6.8 percent in October, while their white-collar federal counterparts got a 7.1 percent raise.

Blue-collar federal workers are paid under an entirely different system than white-collar (General Schedule) employes. The white-collar people get a nationwide raise effective with the pay beginning on or after Oct. 1. The white-collar boost is based on a national survey of professional, technical and clerical pay in industry. It is subject to heavy political pressure and interpretation.

(This year, for example, data given President Carter showed that a raise of around 13.5 percent was necessary to bring federal white-collar pay up to industry levels. Carter submitted an alternative plan, however, calling for a 9.1 percent boost.)

Blue-collar federal pay is linked to hometown industry pay rates. There are between 130 and 140 wage survey areas in the U.S. One of them is the metro Washington region. Under the blue-collar system, the primary federal employer of wage board employes (that is the Defense Department here) makes a survey of selected local industries, and comes up with a pay recommendation. It goes into effect automatically the same time every year. By coincidence, the Washington area blue-collar raise comes due in October, when white-collar workers get their raises.

In recent years, political considerations have also gotten into the blue-collar pay surveys which cover nearly half a million employes. Either Congress, or the White House, has imposed caps on pay raises.

People who watch blue-collar pay developments expect the same thing will happen this year: That is that Congress or the president will slap a 9.1-percent maximum on the blue-collar raises. The official amount won't be known until mid-month. But don't count on anymore than 9.1 percent, and perhaps not even that much.