FAA 7460-1 › Montana ›
Building or using a crane near Ruby Valley Fld (RVF)?
Ruby Valley Fld in Twin Bridges, Montana is a public-use airport. Under 14 CFR 77.9, anything within 20,000 feet of its runways that rises above a 100:1 slope needs FAA Form 7460-1 at least 45 days before construction. Check your exact site free.
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How tall can you build near RVF without filing?
The notice surface rises 1 foot for every 100 feet of horizontal distance from the nearest point of the nearest runway, starting at the runway's elevation. Using the lowest runway-end elevation, 4,705 ft above sea level:
| Distance from nearest runway | Notice required above (height over 4,705 ft) | …which is this elevation (AMSL) |
|---|---|---|
| 250 ft | 2 ft | 4,708 ft |
| 500 ft | 5 ft | 4,710 ft |
| 1,000 ft | 10 ft | 4,715 ft |
| 2,000 ft | 20 ft | 4,725 ft |
| 3,000 ft | 30 ft | 4,735 ft |
| 5,000 ft | 50 ft | 4,755 ft |
| 7,500 ft | 75 ft | 4,780 ft |
| 10,000 ft | 100 ft | 4,805 ft |
| 15,000 ft | 150 ft | 4,855 ft |
| 20,000 ft | 200 ft | 4,905 ft |
| Beyond 20,000 ft | Only the 200-ft-above-ground rule applies (77.9(a)) | |
If your ground is lower than 4,705 ft you can build taller by the difference; if it's higher, less. Cranes count at their maximum height. The free check above uses USGS ground elevation for your exact spot.
Runways and notice boundary
Dashed line: the 20,000-ft area where the 100:1 notice slope applies; inner line: 5,000 ft.
| Runway | Length | End elevations (ft AMSL) |
|---|---|---|
| 07/25 | 2,866 ft | 4705.1 / 4763.6 |
| 17/35 | 6,000 ft | 4788.9 / 4760.3 |
Filing Form 7460-1 near RVF
- File online through the FAA's OE/AAA system at least 45 days before construction or before applying for a building permit, whichever is first. Filing is free.
- You need NAD 83 coordinates, site ground elevation, structure height above ground and above sea level.
- Construction on airport property always needs notice, whatever the height.
More: Do I need to file Form 7460-1? · Cranes and Form 7460-1
Other public-use airports nearby
- DLN — Dillon (20 nm)
- BTM — Bert Mooney (26 nm)
- EKS — Ennis Big Sky (32 nm)
- 02T — Wise River (32 nm)
- 9S5 — Three Forks (37 nm)
- 3U9 — Boulder (41 nm)
Source: FAA airport, runway and runway-end data (NASR cycle effective 2026/10/01). Screening only — the FAA issues determinations.