On July 25th 2016, the US Army Corps of Engineers found that the Dakota Access Pipeline running under lake Oahe / the Missoury River will have "No Significant Impact" following an environmental impact survey. How is that possible that this was the finding, considering the frequency and occasional severity of oil spills from pipelines (for frequency - see those by the intended operator of DAPL although somehow the spill amount figures there are smaller than the actual numbers; for severity, see the recent 14,000 barrel spill in a pipeline co-owned by a co-owner of DAPL) or the much larger spill)and the expected detrimental effects of an oil spill below a river basin (especially with the river providing drinking water to a large population)? The report summary mentions monitoring systems, valves etc. - but other pipelines also have those (I would think), and still leak and cause significant damage.

Also, if these findings were actually sound (content-wise and procedure-wise), how could the USACE be executive-ordered to conduct another impact study? Why would it find anything else?

  • 5
    You say "considering the frequency of oil spills", but as far as I know oil spills from pipelines are really rather rare considering the number of pipelines out there. Do you have any citations to say otherwise? I'm sure the USCE knows that if it leaks into the river it would be bad, but I would guess they are saying the chances of this happening is exceedingly low. Feb 17 '17 at 14:15
  • 1
    @DavidGrinberg: See added link.
    – einpoklum
    Feb 17 '17 at 14:34
  • 1
    They have 203 reported leaks over 6 years. How many leaks per mile of pipe line is that? Feb 17 '17 at 14:41
  • 2
    So based on that article they had ~200 leaks in the past 6 years totaling ~3400 barrels. Thats around 17 barrels per leak. I'm not an expert, but that sounds like (1) its still pretty unlikely to have a leak, (2) 17 barrels, while still bad, is not that bad, (3) 71% of the spills were in the operator facilities, so wouldn't hit the water, and (4) according to the article they are the highest but still pretty close to the rest of the field. Feb 17 '17 at 14:42
  • 3
    Short version: their definition of "significant" is different from yours; and is likely based on the overall risk assessment, which includes probabilities and estimated impact size; and not merely "any spills are awful, period"
    – user4012
    Feb 17 '17 at 16:25

The environmental impact report is 1200 pages long and I don't have a plan on reading it, so please take this answer with a grain of salt. That being said, I do want to show that, at least to a layman, when you run the numbers there does not immediately appear to be a huge risk.

First lets look at how bad Sunco is comparatively. From your article:

Sunoco Logistics ... spills crude more often than any of its competitors with [203] leaks since 2010

From the top it looks like Sunco is the worst, and that appears to be true, but the next important line is

... ahead of at least 190 recorded by Enterprise Products Partners and 167 by Plains All American Pipeline

So even though they are ahead, they aren't ahead by much. They seem to be within a reasonable deviation (again, remember, layman).

Second, lets see how bad those leaks actually were

Sunoco and its units leaked a total of 3,406 net barrels of crude in all the leaks over the last six years

So 3400 barrels over 200 spills is about 17 barrels per spill. Plus take into account that

In 2015, 71 percent of pipeline incidents were contained within the operator's facility

Assuming that stays reasonably consistent across the 6 years, that means that only ~1000 barrels were spilled in the wild over ~60 spills

From this informational about Sunco we learn that

Sunoco Logistics has approximately 8,000 miles of pipelines throughout the United States.

That means around 1/8th of a barrel of oil per mile.

Now I'm not sure how long the protested section of pipeline is, but I doubt its more than a few dozen miles, lets say 50 (please let me know if I'm off). A 50 mile stretch has a ~.0075% chance of having a leak (based on the historical data presented) and would leak an average of 17 barrels of oil. Again, I'm not an expert, but I don't think a 17 barrel oil leak is going to permanently ruin a water supply (obviously still a big problem though if it does happen). Based on these very rudimentary calculations I think its reasonable to classify this as "No significant impact".

All that being said, I really want to reiterate here that I am not an expert, all of this is not sound statistics or data science, and it should all be taken with a giant grain of salt. On top of that, my numbers are all about averages. But outliers exist. The pipeline is an existential gun to the water supply. If it leaks it will probably leak 17ish barrels of oil, but it can leak much much more. It is, to a certain extent, a Pascal's wager.

As for your last question, an environmental impact assessment is big and complicated (over 1200 pages this time!). Its also unique to each environment. That means there are a lot of details that can't be accounted for in a single run. Adding an additional review can help investigate these. Additional reviews can also help verify previous findings (because the core of science is reproducability, especially through peer review). Bottom line even if the first assessment was done with high quality, the chances of a second high quality report being the exact same are low.

  • 1
    I'm curious if you can address in this answer the fact that the pipeline avoided nearby Bismarck on the premise that it was an unacceptable risk to that town's water supply. Feb 17 '17 at 17:55
  • 1
    @Pyrotechnical I can't, I'm not even going to try. I think the answer I wrote is speculative enough, I'm not going to add any more. Also I just don't know. Feb 17 '17 at 17:56
  • 2
    @Pyrotechnical That is not the entire premise for why the route was changed. bismarcktribune.com/news/state-and-regional/… Feb 17 '17 at 18:11
  • "The state regulators also said they held a 13-month review process but didn’t hear these concerns from the tribe." I'd be very curious as to why not. If their public notification process was poor, then I might find that argument pretty thin. Feb 17 '17 at 19:21
  • @Pyrotechnical Legal opinion regarding their participation in the review process: sayanythingblog.com/entry/… Feb 17 '17 at 20:14

I went ahead and opened up the environmental impact statement to see what they had to say. The things I noticed are summarized below. I'll repeat David Grinberg's disclaimer though: I am no kind of expert in environmental engineering or policy.

All page numbers are pages of the PDF, not the printed page numbers.

Alternative Plans

In some cases, the DAPL was found to have no significant environmental impact because without the pipeline, the alternative plans would have equal or greater impact. The point of comparison isn't "having a pipeline or doing nothing", it's more like "do we build a pipeline or do we transport all this stuff by train or truck?" In many cases, the pipeline is expected to have less impact (or the same impact) as the alternative plans.

For more information, see the ALTERNATIVES section on page 16. You could also look at the specific risk areas (3.1 is on page 23, 3.2 is on page 46, etc.).

Risk Areas

Much of the discussion around the oil pipelines focuses on the possibility of oil spills. The environmental impact statement focuses a lot on risks of construction and maintenance. For example, the economic conditions section (page 3.8) describes the positive impact to the economy for building the pipeline.


Their risk management steps are in section 3.11 (page 100). Basically, they are going to construct and test the pipeline in according with industry best practices and federal law. Additionally, they have a mitigation and containment strategy in place in case there is an oil spill.

The list out the pieces of the risk mitigation plan on page 120:

 BMPs designed to minimize the effects of construction on environmental resources;

 Temporary and permanent erosion and sediment control measures;

 Soil handling procedures designed to preserve the integrity of the soil (e.g., topsoil segregation, decompaction, etc.);

 Wetland and waterbody crossing and stabilization procedures

 Wildlife and livestock mitigation measures

 Restoration and revegetation procedures

 Refueling and waste management procedures

 Weed management procedures

 Winter construction practices

 Stormwater management procedures

Past Development

The DAPL is being built along an already existing natural gas pipeline and an overhead electricity transmission line. These projects have already created some environmental impacts, reducing the marginal impact of the DAPL.


There are apparently geographic reasons that the environmental engineering staff thought were important. For example, in the aquatic resources section (page 80) they describe how the physical geography of the area limits possible harm to bodies of water and aquatic life. Some reasons include: the distance between the pipeline and waterways, the existence of sedimentary deposits which can buffer problematic chemicals, and an erosion control plan which will help keep the sediment in place.

When the pipeline does come near water, it is to be built deep enough and with thick enough pipes that the risk of spillage is reduced.

Business Growth

Finally, the report discusses the possibility that a pipeline could allow for growth in the oil/gas industry, which could create future risks to the environment (page 109). According to the state of North Dakota, the pipeline won't have this effect because it isn't a lack of pipelines slowing development.

  • (1) Ah, so it's just "impact versus the alternatives we're willing to consider", not "absolute impact". Still, that doesn't address the frequency and severity of spills, which AFAIK (and I don't really) is much worse than even transporting with trucks (2) Distance from the pipeline to the waterways? It runs under the river doesn't it? (that's not directed against you of course).
    – einpoklum
    Feb 23 '17 at 17:26
  • On #2, the report says that the pipeline goes under a lake (or maybe it was a river), but that it was far enough underground and the pipe was thick enough that the risks were relatively low. Not being an engineer, I can't really appraise whether that is true or not. Feb 23 '17 at 17:49
  • 1
    On #1 - Evaluating the pipeline against alternatives is at least reasonable. If the pipeline wasn't built, they would find another way to ship oil (like trucks). I sure don't know whether trucks are safer than pipelines, but the report seems to imply that pipelines are safer. Feb 23 '17 at 17:50
  • Evaluating against the convenient alternatives is the problem; and the assumption is the problem. The assumption is that the oil needs to be transported. Take away that assumption and things look very different. Or add other assumptions - such as "no significant risk allowed to drinking water sources" - and again options look different. As for pipelines vs trucks - we know of massive, frequent, oil spills from pipelines; I don't know that this happens from trucks. Trucks to pollute the air more, though.
    – einpoklum
    Feb 23 '17 at 18:16
  • 1
    @einpoklum - All I can really do is pass on what the report says. If you have concerns about the contents of the report, maybe EarthScience.SE can help? Feb 23 '17 at 19:49

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .