Development is permitted within certain zones of the FIRM maps provided that a Floodplain Permit has been issued for the development.
Zone AE - Floodway
The Butte-Silver Bow Floodplain Ordinance does not permit the construction of new residential, commercial or industrial buildings within a depicted floodway. Alterations to buildings within the floodway that are valued at more than 50% of the buildings value are also not permitted.
Zone AE- Floodway Fringe
The floodway fringe does allow the construction of new residential, commercial and industrial buildings and alterations to the buildings. However, new construction is required to meet the following regulations:
Residential – the top of the lowest living floor must be elevated a minimum of two (2’) feet above the BFE for that particular location of a mapped stream or river. The residence can be elevated utilizing infill (soil pad), piers or stem walls. The soil infill (pad) must extend outward for a minimum of fifteen feet in every direction from the foundation of the residence. The fill soil must meet floodplain standards regarding soil materials and be compacted to floodplain regulations.
To ensure that the top of the lowest floor is elevated a minimum of two feet above the BFE a Floodplain Development Permit Application must be submitted to the Butte-Silver Bow Planning Department for review and approval prior to any construction taking place. It is important to know, an approved residence located on fill within the floodway fringe is still considered within the 100-year floodplain and therefore may be result in the landowner having to purchase flood insurance.
Zone A also permits the construction of new residential, commercial and industrial buildings. However, since BFEs have not been determined by FEMA an engineering firm must be utilized to determine the BFE for the location. The residence must be constructed a minimum of two feet above the determined BFE. A Floodplain Development Permit is also required for new construction within this zone.