Arlington County Manager Anton S. Gardner yesterday proposed a $342.6 million budget for fiscal 1989, a 5.9 percent increase over the current year. The budget presented to the Arlington County Board is essentially a standstill one, with inflation and the financing of a revamped employee pay plan accounting for most of the increase, according to county finance officials.

The county is proposing an operating budget of $283.6 million as part of the proposed $342.6 million budget for the fiscal year that begins July 1. General fund revenue is estimated at $286.4 million.

The new spending plan proposes to maintain most county services at current levels and assumes an additional $2 million contribution to a year-old affordable-housing fund.

It also includes funding for 16 additional county positions, with most of them in the library system, the police department and the human services department.

The new positions would help meet current demands for services, not start new programs, Gardner said. "In recent years we have begun to do many new things and it is time to be sure that the things we do, we do right," he said.

The budget assumes no increase in the real estate or personal property tax rates, but it projects as much as a 13 percent increase in real estate assessments, an indication that the tax bill for the average homeowner will likely rise.

County Board Chairman John G. Milliken said it was too early to tell whether the board will cut the real estate tax rate -- currently 92 cents per $100 of assessed valuation, one of the lowest rates in the metropolitan area -- to offset an increase in assessments.

State and federal aid this coming year will be static, according to the budget. New revenue is projected to increase by $20.5 million, almost all from local tax sources, Gardner said. County budget Director Mark B. Jinks noted that the rate of growth in local revenue sources is slowing.

A rise in the water-sewer tax rate and some fee increases are proposed in the budget.

The increase in the water-sewer tax would cost the average homeowner about $24 a year. The funds would be used to pay the interest on a bond issue to finance improvements in the county's sewer treatment plant, Gardner said.

The board has also been asked to consider three options that would raise garbage collection and disposal fees by $14, $35 or $61 a year. Revenue would correspondingly increase by $430,000, $1.07 million or $1.85 million a year.

Also proposed are increases in parking meter rates and a restaurant inspection fee. Business license taxes would be cut $1.1 million as part of a state-mandated rollback.

The budget includes about $3.4 million for a new employee pay plan. The county has 2,438 full-time workers.

An additional $8.8 million is included for cost-of-living increases for school and county emloyees. The exact percentage increase will be set in April.

Gardner said he has proposed scaling back spending on capital improvement projects by about $1 million, because some projects are proceeding at a slower rate than anticipated, and to give the County Board more flexibility in determining spending.

A $9.9 million general fund for capital improvements is proposed for projects including impovements to Glebe Road, design work for a new jail and improved athletic fields.

The proposed budget leaves unallocated $2.8 million above the $342.6 million base spending plan.Gardner gave the board a list of 45 unfunded initiatives that could be financed with the $2.8 million. These range from creating a police substation with five officers on foot patrol in Crystal City to setting up an AIDS bureau to provide education, referrals and direct care for AIDS patients.

Also on the wish list are proposals to set up better radar enforcement, establish an employment center for county residents, fund an outreach program for adolescent girls and open a new group home for the mentally retarded.

The board will hold a public hearing on the budget at 7 p.m. March 15 at the Kenmore Intermediate School. It is scheduled to adopt its new budget April 30.