Fairfax County Executive J. Hamilton Lambert unveiled a $1.85 billion fiscal 1989 budget yesterday that would increase the tax burden on a typical county household by $247, primarily because of rising real estate assessments.

Calling the budget "accommodative," Lambert said $151 million is set aside for transportation projects, at least $131 million is to fund programs for the poor and $724.4 million is for public schools.

The budget, which proposes an 8.9 percent increase in general fund spending while keeping the tax rate steady, includes money to open 10 child care centers at county schools and expand 13 others, and to add 52 positions in the police department, including 30 patrol officers. The first year of a five-year program to replace 15 Basic Life Support ambulances in the fire department with advanced life support units that offer more sophisticated medical treatment also would be funded, and $6 million would be devoted to alcohol and drug abuse programs.

Under Lambert's proposal, households would pay more for refuse collection by the county, with fees increasing from $135 to $180 per unit per year. About 36,645 of the county's 277,600 households have county garbage collection. Costs for dumping at county landfills for private trash haulers, the District of Columbia and others would increase from $17.75 per ton to $24 per ton.

No increase is proposed in leaf collection or sewer rates.

Noting that the budget figures are up 50 percent for transportation and 16.9 percent for schools over fiscal 1988, Lambert said his budget strives for a "prudent balancing of resources . . . at the same time being sensitive to the needs of all other programs in the county."

He warned, however, that "if the school transfer continues at the rate it is, I cannot absorb it without making severe adjustments" in other areas.

By law, Lambert is not allowed to change the school budget, which was approved by the School Board two weeks ago. Instead, he transmits it to the Board of Supervisors along with the county budget, and the board amends and approves each separately. The board, after a series of public hearings, is expected to act on both budgets and set the real estate tax rate on April 25.

Some supervisors, citing pressures to increase spending on schools, roads and human services, have said it is unlikely the board will be able to approve a significant reduction in the tax rate. The board has lessened the impact of rising assessments by approving a tax cut every year since 1984. Some supervisors also have said the board may cut the school budget for the first time since 1982.

The county's residential real estate tax rate would remain at $1.32 per $100 of assessed value under the proposed budget. But the mean assessed value of a single-family house is expected to rise 14 percent, from $120,734 to $137,637, meaning that taxes on the average home would increase $223 -- from $1,594 to $1,817.

A typical household in fiscal 1989 also would pay $349 in personal property taxes, $236 in sales taxes and $94 in consumer utility taxes, up a total of $24 from the current year based on historical trends and expected inflation, according to county officials. Including real estate taxes, the total tax burden would be about $2,496, up $247 from the current year.

The proposed fiscal 1989 general fund -- government services paid for with local taxes -- is $449.9 million, an increase of $36.9 million over the current fiscal year. When the school budget, Metro funding and other programs are included, the combined general fund is $1.106 billion, up $120.7 million from fiscal 1988.

The overall 1989 budget of $1.85 billion -- the combined general fund plus capital projects, sewer system funds, debt service payments and other programs -- is down $165.9 million (8.2 percent) from estimated spending in the current fiscal year, which ends June 30.

About $32 million in revenue will come from the federal government, and $224 million is expected from the state -- $189 million of which would go to schools.

Lambert said rising assessments are not a "Fairfax phenomena," noting that Arlington assessments are expected to rise 13 percent while assessment increases in Prince William and Loudoun counties, Alexandria and Falls Church are expected to equal and possibly exceed Fairfax's.

The increase can be attributed to interest rates and real estate trends, Lambert said. "Low interest rates have resulted in increased demand, {and} coupled with the high cost of land, {have} produced higher home values."

Lambert said that a combination of elements governs the budget increase: inflation, which was 4.5 percent last year; the school budget, which asks that county funding be increased $74.5 million over fiscal 1988; decreases in state and federal aid, which, since 1983, have dropped from 6.4 percent to 3.8 percent of combined general fund receipts; transportation improvements; and growth. The county's population increased from 596,901 in 1980 to 704,757 in 1988 and is expected to grow by an additional 33,000 in fiscal 1989.

To accommodate that growth and plan for the future, the budget includes:

373 new positions -- 217 of which are proposed for public safety and health and welfare programs -- at a net cost of $9.7 million.

$151 million for transportation projects, up from $100 million in the current year, including $56.2 million for public transportation, $73.5 million for the Springfield Bypass, $4.1 million for Telegraph Road improvements and $1.9 million for South Van Dorn Street improvements. A proposed $150 million spring transportation bond referendum was not included in fiscal 1989 budget calculations because it has not been voted on, Lambert said. $32 million for the second year of the merit pay plan for teachers.

$478,280 to add 10 care centers at county schools for school-age children and expand 13 others to increase the number of child care slots available from 2,325 to about 3,150. Lambert said that though the county provides or subsidizes day care for about 6,175 children, more than 3,000 spaces are needed.

$10.8 million for 4 percent cost-of-living increases for county employees.

$131 million ($68 million of which is county funds) to finance health, housing, day care, employment and other programs for low- and moderate-income persons. According to county statistics, about 25,000 persons live at or below the "near poor" level, which is an annual income of $14,999 for a family of four.

A $378.4 million capital improvement plan to finance, among other things, the opening of six schools and two fire stations, design and/or construction of 24 child care centers at public schools, library renovation and expansion and other projects.