an employee in a position requiring him regularly to remain at, or within the confines of, his station during longer than ordinary periods of duty, a substantial part of which consists of remaining in a standby status rather than performing work, shall receive premium pay for this duty on an annual basis instead of premium pay provided by other provisions of this subchapter, except for irregular, unscheduled overtime duty in excess of his regularly scheduled weekly tour. Premium pay under this paragraph is determined as an appropriate percentage, not in excess of 25 percent, of such part of the rate of basic pay for the position as does not exceed the minimum rate of basic pay for GS–10 (including any applicable locality-based comparability payment under section 5304 or similar provision of law and any applicable special rate of pay under section 5305 or similar provision of law) (or, for a position described in
section 5542(a)(3) of this title, of the basic pay of the position), by taking into consideration the number of hours of actual work required in the position, the number of hours required in a standby status at or within the confines of the station, the extent to which the duties of the position are made more onerous by night, Sunday, or holiday work, or by being extended over periods of more than 40 hours a week, and other relevant factors; or