People occasionally ask if the Dragonpipe (Mariner East pipeline system) can be built “safely”. It certainly is possible, but the question is whether there is a practical way to do it. In this blog post I will lay out two possibilities, one which has been mentioned many times over the past several years, and one which has recently come to my attention, based on a pipeline project in Michigan.
Option 1: Buying up the blast zone. Until recently, I would have said that the only relatively “safe” way of building the Dragonpipe would involve these three steps:
- Sunoco would buy up all the property within the blast zone, at full market rates
- Sunoco would arrange for new locations for schools, businesses, churches, retirement facilities, and other public gathering sites
- Sunoco would then clear all the land (or perhaps sell back the homes, at a discount, to those willing to take the risk of living in the blast zone).
A quick back-of-the-envelope calculation makes it clear that the investment and disruption involved would make this plan a complete non-starter for Sunoco. The cost would be many times higher than the cost of the pipeline itself (which underscores the point that Sunoco would not be doing this project at all if it accepted responsibility for its real cost, and that’s certainly an important point to make). But I believe this approach to a “safe” pipeline will never happen. So is there any other possibility?
Option 2: A really big, really deep tunnel. Maybe we should consider an idea from Michigan, where there is a somewhat analogous pipeline controversy concerning the Enbridge “Line 5” pipeline. This pipeline provides an interesting comparison to the Dragonpipe. It was built in 1953 and carries primarily crude oil, although “natural gas liquids” (NGLs—the same materials that the Dragonpipe carries) are also carried at times. It originates in western Canada and cuts across Wisconsin and Michigan on its way to a refinery in Ontario.
The big concern with Line 5 is its crossing between Michigan’s upper and lower peninsulas. This crossing is at the Straits of Mackinac, where Lake Michigan and Lake Superior connect. A serious leak there could foul sources of drinking water, pollute hundreds of miles of shoreline, and devastate wildlife and lake-based recreation in the area. The pipe is old and has been out of compliance with various regulations. It is showing signs of corrosion. For most of the length of the crossing, it is sitting on the lake bottom, unprotected. It was recently damaged by a boat anchor (although it did not leak). A lot of people, including the newly-elected governor of Michigan, want it shut down.
The Line 5 tunnel plan. Last summer, Enbridge reached an agreement with the state of Michigan for a different approach: a big, open tunnel that will contain the pipeline (along with other utilities), allowing for pipeline inspections, and containing any spill that might occur.
You can read the details of the plan (and the alternatives that were considered) here. Enbridge proposes to set up a large boring machine, the kind that is used for train and automobile tunnels, and drill a tunnel about 100 feet below the straits. The length would be 4 miles. The inner diameter would be at least 10 feet, and it would contain the 30-inch pipeline that would replace Line 5. It would be inside a continuous concrete casing. The cost would be between $350,000 and $500,000 (paid for by Enbridge).
Although it is clear to all parties that having Line 5 in an open tunnel like this would represent a big improvement over the present arrangement, there is still considerable opposition to this plan. Some of it is due to concern about leakage of the existing pipeline while the tunnel is being built (it will take up to 10 years). Some is outright opposition to a big fossil-fuels infrastructure project, especially given that the pipeline carries petroleum products from one part of Canada to another, with little or no benefit to Michigan.
Could a tunnel work here? Reading about Line 5 caused me to consider whether a tunnel might be a relatively safe solution for the Dragonpipe. Suppose Sunoco drilled an open tunnel with a concrete casing and a diameter of 10 or 15 feet, at a depth of 100 feet or more, under the full length of Chester and Delaware Counties (about 24 miles). It would have to be big enough to contain pipes for the entire Mariner East system, plus room for inspectors to work and spills to be contained.
The idea would seem to have some merit. Using estimates based on the reported costs of the Mont Blanc tunnel (under the Alps) and Enbridge’s estimate for the Line 5 tunnel, I calculate that tunneling would add perhaps 50% to the overall cost of the Dragonpipe, which might still make it a viable business proposition from Sunoco’s point of view.
For me to endorse this concept, I would need good answers to a series of questions, such as:
- Where would the access points to the tunnel be, and what risks would there be for the surrounding area?
- How would damage to aquifers and wells be prevented?
- How would the tunnel be protected from damage due to karst subsidence?
- Would the construction of the tunnel itself create the potential for damage to structures on the surface?
No doubt there will be other questions as well, but I would be a whole lot happier with an easily-inspected pipeline running inside an open, spill-containing tunnel than I am with the shallow, leaky, and hard-to-inspect pipeline we are currently facing.
What do readers think?
Sunoco, what do you say? How about considering an investment in an option that might actually be safe?
I don’t what karst subsidence is, but could drilling for Plan 2 cause earthquakes like when they’re doing frack sanding?
I don’t think earthquakes are a possibility (those are thousands of feet deeper), but there might be a lot of local vibration. That would be worth looking into. I’m sure there are plenty of subway tunnel projects where the drilling vibration (or absence of it) would have been documented.