Lewis & Clark County Flood Information

Floodplain Development Permit Application:

Tenmile Creek Water Treatment Plant (15-day Comment Period Ending March 19, 2018 at 5:00 p.m.)

Flood News

No news available.

Lewis and Clark County Flood Plain Ordinance

Flood Insurance Rate Maps



For more information, please contact Community Development and Planning at 1(406) 447-8374 or via email at planning@lccountymt.gov.

Health and Safety Fact Sheets

  • After the Flood: Water and Mold Clean-Up (PDF)
  • Managing Your Septic System During, After a Flood (PDF)
  • Your Well: What to Do After the Flood (PDF)
  • During and After Flooding: What's Safe to Eat (PDF)

Water Quality

Wastewater & Septic Systems

  • Managing Your Septic System During, After a Flood (PDF)
  • Reduce water usage as much as possible to prevent further ground saturation.
  • Do not discharge sump pumps into septic systems, which were not designed to handle such large quantities of water.

Other Information:

  • Your Well: What to Do After the Flood (PDF)
  • Assume all flood water is contaminated with bacteria and other germs.
  • If you have a private well, and if flood waters have reached your wellhead, assume that your well water is contaminated.
  • If you have any questions or concerns about the quality of your drinking water, get it tested at one of these three local facilities: Alpine Analytical, 449-6282; Energy Laboratories, 442-0711; or State of Montana Public Health Laboratory, 444-2642.
  • Don't use contaminated water or questionable water for any domestic purpose, such as cooking, drinking, bathing, brushing your teeth, or making baby formula.
  • Use bottled water or disinfect water that may be contaminated. You can disinfect water in one of two ways: bring it to a boil and boil for 5 minutes, or mix it with household bleach at a ratio of 5 drops of bleach to 1 quart of water.
  • Avoid exposure to flood water if you have an open wound.
  • Don't allow children to play in flood waters.
  • Wash hands after coming into contact with flood waters.


  • Residents with concerns about electrical infrastructure should contact NorthWestern Energy's Operations Call Center, 1-888-467-2669.
  • Do not dig trenches or holes to divert water without first calling a locator service to make sure utilities will not be compromised. Locator services are available by calling 8-1-1.
  • Flooding may create electrical hazards. If you suspect damage to your electrical system (for example, if wiring has been under water, wires are visibly frayed, or you see sparks), turn off the electrical system in the building. Do not turn it back on until electrical equipment has been inspected by a qualified electrician.