How is it that the USACE found there will be no significant environmental impact of DAPL?

Question

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?

Answer 1

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.

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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.

Answer 2

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.

Safety

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.

Geography

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.