What happens to the old line you don’t replace? How much of it will you leave behind? Is that safe?

The old line will be purged, and all hydrocarbons will be removed in accordance with disposal regulations. The line will then be filled with nitrogen (essentially air without oxygen, so completely harmless) to prevent oxidation and corrosion of the old steel pipe. This is a standard practice for the industry and prevents us from needing to further disturb communities to remove the old pipeline.