NorthWestern Energy Delivering a Bright Future Wanting to dig? Call 811 first! Whether you're simply planting a tree, building a fence or digging an entire foundation, NorthWestern Energy reminds you to call 811 two business days before any and every project. Digging even a few inches deep can cause costly damage to underground utility lines. Once the lines are properly located, use extreme caution when digging within 18 inches of the marks. Calling 811 is free, easy and the law. 406-755-8344 811 Know what's below. Call before you dig. NorthWesternEnergy.com