TALK TO THE Alexandria families of Cameron Valley, probably one of the most badly deteriorated public housing projects in the Washington area, and you will find some with surprisingly few complaints. After all, they figure they do have a roof over their heads, even if the house it sits on is sliding off the foundation. Some ask: Where else would we live? Theirs is not an uncommon problem.

There were a total of 264 units, built as World War II temporary housing in 1943. Eighty units have already been demolished, and 34 more have been condemned. City officials say the rest, as they are now, will probably not be habitable through the end of the decade. When the Alexandria Redevelopment and Housing Authority was faced with a similar problem in another part of town in 1981, there were enough federal funds available for new construction to build units for all of the 90 public housing families affected. This time, however, there are 150 units to be replaced in Cameron Valley, and the federal faucet is down to a drip -- only enough to replace 30 units. ARHA does not have the resources to do the rest.

It has rightly assumed the obligation to fill the federal vacuum in this case and has come up with a plan to get new units for some of the public housing residents on the site and more in other parts of the city. The initial reaction by prospective developers looks promising.

ARHA plans to sell the site, valued at $7 million last year and probably worth more now, to developers willing to make a contractual agreement to produce at least 60 low-income housing units on the site, along with whatever other development plans they have. Some 10 acres would be available for commercial use, and there would also be room for as many as 450 market-rate housing units. Proceeds on the sale would be used to help build or buy low-income units in other parts of the city for the other 90 Cameron Valley households. ARHA also got the federal Housing and Urban Development Department to agree to the idea. ARHA says it has already received 100 telephone calls from developers or their legal representatives who are interested in the plan.

This is a good idea, although it will be difficult to find sites for an additional 90 families in other parts of the city. ARHA officials say they are also looking into buying condominiums for 45 elderly Cameron Valley households, again using proceeds from the sale. It may be best to try to have more than 60 units on the Cameron Valley site. The test for the city will be to find ways to find new housing for all 150 families. That is the standard they must meet in this case.