Demo saw. They're used to cut both cast iron and ductile iron pipe. They run like a chainsaw but have a 14 inch abrasive wheel. Check your local rental center. Safety Glasses With Side Shields are a must when using these. Don't cut without them on your head. One inch thick will take some blades.
Note, All cutting wheels aren't equal. Welding suppliers & construction suppliers usually sell good ones. You want a commercial grade that says Cast Iron & Ductile Iron and is marked for the RPM rating marked on the saw. Usually the ones sold at Lowes and hardware supply outlets sell the ones for electric chop boxes and these aren't what you want