Alice Thomas lives in a dilapidated, aluminium trailer along one of the few paved secondary roads in the rural Sandy Springs area of Montgomery County. Her trailer has no running water, so each day she carries water up a hill to her home from a muddy well about 30 yards away.

Her plumbing is a pipe that leads from her bathroom to a hole in the ground somewhere out in the woods beyond her trailer.

Thomas's trailer is illegal. She knows it. So does the county. But the county has left people like Thomas's alone rather than enforce its own building codes because a mobile homes are becoming virtually the only housing many of Montgomery's rural poor can afford.

There are about 250 illegals mobile homes in the county. Most are concentrated in the Sandy Springs area in the eastern half of the county and in the Jerusalem and Jonesville areas in the west end.

They range from rusty trailers to modern mobile units that resemble contemporary ramblers. But because they are illegal, they are not inspected by the county for safety and health hazards. They cannot be hooked into the public sewer or water system. Nor are they serviced by public utility poles.

To get electricity, the mobile-home owners usually have some electrician - an amateur in most cases - run an electric line from a neighboring house to their trailer. In most cases, the electrical connection is merely an ordinary extension cord run along the ground or strung across the trees.

Such conditons were described in a 1976 report on mobile homes by a private consulting firm and a citizen task-force study completed last June.

This December the County Council and county executive will decide whether or not to legalize and set standards for the homes, creating a significant new potential for housing for low-income people at a time when the average price of a single-family home in Montgomery is $70,000.

The medium income of the people living in the illegal mobile homes is $7,800 according to the taskforce study.

The situation of Montgomery's rural poor like Thomas, whose income is $246 a month from public assistance, is particularly precarious. Public and subsidized housing is nonexistent in the portions of the county where they live.

There are long waiting lists for what ever-low-and moderate-income housing is available.

Barbara Budd, who lives in a mobile home on Brooke Road in Sandy Spring, has been on a public housing waiting list since 1965. When her mobile home caught fire last April, she said , "I didn't even try to look for a house because I knew I just couldn't find anything I could afford. So I just bought another mobile home."

"The county has no other choice but to legalize mobile homes or else build some low-income places for people to live in," she said.

The problem of providing low-income housing for these rural residents is that they live on the outer fringe of Montgomery's sewer envelope - that area extending roughly from Rockville to the District of Columbia border in the Colesville area, where sewer allotments have been reserved for new housing.

Any new development in the county within the next 10 years will occur almost exclusively within that sewer envelope, which destroys any immediate hope for new housing for the county's rural people.

The situation is further complicated by the fact that families like Thomas and Budd's have lived in their communities for generations and their homes, for the most part, are on land acquired generation ago. They do not want to move.

"I don't want to be pushed down county to Rockville or Gaithersburg." said Joan Prather, who lives in a modern-five-room mobile home on Chandlee Mill Road in the Jonesville area.

Prather, who supports two children on an annual income of $13,000 said moving into a mobile home nine years ago meant getting away from the "roaches, hoodlums and noise" of the Rockville Gardens housing project, where she was paying $114 rent a month. The project was later torn down by the city of Rockville.

Nine years ago, she found most houses she looked at required a $2,000 down payment and monthly mortgage payments of $300. So she purchased a mobile home with an $800 down payment and finished paying for it recently with monthly payments of $95.83.