The county budget may contain a provision for an equipment replacement reserve within a fund. The amount in this reserve shall be identified with the class of fixed assets, and may accumulate from year to year, but at no time shall it exceed the estimated replacement cost of the items of fixed assets for which it has been accumulated. The particular amounts in the reserve shall be made available for expenditure in the year that the items are replaced or removed from service without replacement. The estimated replacement cost of the fixed assets shall be adjusted each year.