Deadly Hydrogen Sulfide Accident Puts Deer Park in Headlines Again

 

A friend once summarized much of engineering ethics to me in two words:  "No headlines."  If that's a good guideline for engineering ethics, the city of Deer Park has seen two major violations of it in less than a month. 

 

Following a giant pipeline fire that burned for four days in September, on last Thursday, Oct. 10, some contract employees at the PEMEX refinery in Deer Park were working on a pipe flange, and something went wrong, releasing the pipe's contents into the air.  They may or may not have known that the pipe was carrying hydrogen sulfide (H₂S), which is a byproduct of oil refining.  It is probably familiar to most readers as the "rotten egg" odor that comes from aged chicken products and sewer gas.  The human nose can detect it at concentrations as low as one part per billion.  Unfortunately, one of its toxic effects is to deaden the olfactory nerves, causing the perceived smell to go away and leading to a false sense of security as concentrations increase.  It is highly toxic, and concentrations as low as 100 parts per million are classified as "immediately dangerous to life and health."

 

Two contract workers died in the accident, which occurred around 4:40 in the afternoon, and 35 others were exposed to the gas to the extent of needing treatment.  The bodies were not recovered until 3:30 AM the next day after the area had been cleared of toxic gas.

 

The city of Deer Park sent out shelter-in-place orders to its residents around 6:30 PM, but due to technical difficulties with the alert system, some people were not alerted until they read about the incident on social media.  A supplemental siren system in the city is due for an upgrade soon.

 

The accident is under investigation by both local authorities and the U. S. Chemical Safety and Hazard Investigation Board, but no cause has yet been determined. 

 

As we noted two weeks ago when writing about the pipeline fire, residents of Deer Park and surrounding communities in Houston are no strangers to refinery-related emergencies.  Release of toxic chemicals in oil refineries has been happening ever since there were refineries, and the industry has adapted to steadily increasing standards for air and water pollution control and safety measures over the decades.  The PEMEX refinery where this accident occurred dates back to 1929, when it was built by Shell Oil.  In 1993, Shell sold half the facility to the Mexican national petroleum company PEMEX and operated it as a joint venture until 2022, at which point Shell sold its share and PEMEX became the sole owner and operator.  This change of ownership may or may not have anything to do with the accident, but management cultures can change with ownership changes, and the upcoming investigation may answer that question as well as many others.

 

Considering the extremes of temperature and pressure under which highly flammable and toxic chemicals are processed in refineries, it's a wonder that we don't have a refinery explosion every day.  But it's the job of engineers to make sure that every possible thing that can go wrong in a refinery is anticipated and forestalled, and far more than 99.9% of the time, this foresight prevents mishaps. 

 

As with airline accidents, by far the most frequent cause of chemical-plant accidents is human error rather than a simple failure of machinery, although the two can be mixed.  The accident in question could have happened because the workers involved misidentified a flange to be worked on.  An oil refinery is one of the most complicated pieces of plumbing on earth, with thousands of valves, flanges, pipes, processing units, and interconnections.  Refinery workers have to know exactly what they are dealing with before taking any action that could conceivably release a product, and it might have been a case of simply opening the wrong flange.  Or an operator may have believed that the pipe in question had been purged of H₂S when in fact it hadn't been.  You can't tell the contents of a steel pipe just by looking, so there must be elaborate protocols in place to verify what is where, especially when maintenance operations are in progress. 

 

It is incidents like this one which make refineries and petrochemical plants high on the NIMBY list—"not in my back yard."  Given that a country wants to have fossil-fuel products, and given that it has considerable expertise and resources to make them, we in the U. S. must have refineries somewhere.  According to a list of new refineries compiled by the U. S. Energy Information Agency, the U. S. refining industry has managed to add considerable refining capacity since 2014 by building new refineries, but they tend to be in or near existing ones—Houston, Corpus Christi, or various locations in Alaska.  It's a lot easier to upgrade an existing refinery or build a new one next to an existing one, than it is to install the infrastructure of pipelines and shipping facilities in a place without refineries at all.

 

For the foreseeable future, the global economy will rely on fossil fuels, and so we will have to put up with refineries and everything that goes with them.  But people who live near them and work in them have a right to expect that they will be operated as safely as human ingenuity can manage. 

 

That was obviously not the case at the PEMEX plant last week.  We will follow this accident in the future, and when the investigation concludes, perhaps we will learn what chain of events led to an accident that killed two people and endangered an entire community.  But until then, we can take some comfort in the fact that refineries rarely show up in headlines, despite all the dangerous stuff going on in them.

 

Sources:  I referred to articles on the H₂S accident by ABC News 13 in Houston at https://abc13.com/post/pemex-chemical-leak-crews-waiting-lower-levels-before-entering-unit-center-deadly-hydrogen-sulfide-deer-park/15416337/, an article in the Saturday Oct. 12 edition of the Austin American-Statesman, "2 dead, dozens of others injured in hydrogen sulfide leak near Houston," and the Wikipedia article on PEMEX Deer Park.  The Energy Information Agency data is from https://www.eia.gov/tools/faqs/faq.php.

Water: Not Enough or Too Much in Texas

 

When Hurricane Helene hit Florida on Sept. 26 and dumped up to 20 inches or more of rain in the Carolinas, the flooding that resulted contributed to the verified deaths of over 200 people, and large areas in several states are still struggling to recover.  Meantime, here in Texas a friend of mine who owns a house about ten miles out of town has had his water well go dry, for only I think the second time since they've lived there for about twenty years.  He's having to truck water in and is rigging up a gravity-feed tank to supply his showers and toilets.

 

This is the same friend who, when the possibility of a water shortage came up in conversation several years ago, said, "Hey, there's as much water as there ever was.  It's just in different places than it used to be."  That's certainly one way to look at it, but the way we collect and use water says a lot about our attitudes toward technology and nature in general.

 

In drier parts of the world, which includes most of central and west Texas, a good source of water is vital.  Here in San Marcos, we have a spring-fed lake that archeologists say has been the site of more or less continual occupation by humans for the last nine thousand years.  And the attraction of this particular spot was the continuous (or nearly continuous) supply of fresh water.

 

My friend has been talking to a man who drills water wells for a living, as his forebears have done for decades.  He told my friend that there have been about eight times as many wells drilled in this region since 2020 as there were in the previous thirty years before.  I can't verify that statistic right away, but it sounds right.  Housing developments have sprung up in remote places that used to be ranches that had maybe a well at the house and another well under the stock-tank windmill, for several hundred or thousand acres.  Now there are hundreds of houses on that same land, and each one needs several thousand gallons of water a year. 

 

Many entire towns and cities here in Central Texas get their water from wells.  The main source of well water in this region is the Edwards Aquifer, which Wikipedia calls "one of the most prolific artesian aquifers in the world."  It is an underground reservoir in the porous "karst" limestone of this region, and stretches from near Austin in the east to near Del Rio on the Mexican border to the west.  Water comes into the aquifer on land to the north and west, and exits through springs and wells along the southern edge.  San Antonio has historically obtained most of its water from wells in the Edwards Aquifer, and consequently has one of the lowest water rates in the country.   

 

Hydrology isn't exactly engineering, but there are clearly ethical issues in how much a particular natural resource is exploited.  As more wells were drilled in the late twentieth century, there was concern that even the apparently infinite resource of the Edwards Aquifer could become depleted, so the Edwards Aquifer Authority was created.  Like most such institutions, it has been criticized for being both too lax and too rigorous in protecting a natural resource upon which millions of people depend for life-giving water.  I have a rancher friend who could be counted on to give a fifteen-minute harangue when prompted by a single question about how his battle with the aquifer regulators was going.  And on the other side, there are Save Our Spring campaigns that try to stop new developments from drilling too many wells that will deplete the aquifer so much that the natural springs go dry, which has happened already on occasion.

 

The other side of the Texas water coin is flooding, and we have had plenty of that too.  The weather patterns in this part of the state dictate that we sometimes get as much as half of our total annual rainfall in only one or two months, and one of those months is May.  On Memorial Day 2015, a historic flood resulted when some thunderstorms decided to camp over the Hill Country centered around Wimberley, the town just west of San Marcos.  The Blanco River through Wimberley, which is usually a little trickle barely wet enough to keep the moss green, became a raging torrent that night that swept away campers and people in riverside houses, and even took out a vehicular bridge.  At least twelve people died in the flood and some bodies were never recovered.  My financial adviser, who lives in Wimberley, recalled to us a few months later how he waded out in waist-deep water to help in a rescue effort that night. 

 

While we can still have severe flooding, the efforts of engineers and planners over the decades have done a lot to tame the flash-flood potential of Texas streams and rivers.  Just west of San Marcos is an earthen dam that's maybe sixty feet high and almost a quarter-mile long.  Most of the time it looks just silly, because there's no water behind it.  But during the same 2015 Memorial Day rainfall, the flood-control system built in the 1980s with Federal money, of which the dry dam is one part, channeled floodwaters into a spillway that, while impressing people with its size and rapidity of flow, did relatively little damage except to a neighborhood near the San Marcos River.  A similar flood in 1970, before the flood-control system was built, managed to inundate a good part of San Marcos, including the Aquarena Springs amusement park, whose collection of alligators got loose and led to some interesting situations afterwards. 

 

My father had a saying about women that seems to apply also to water in Texas:  "You can't live with 'em, but you can't live without 'em."  When you're about to be flooded out of your home, you may just have recently had to be trucking water in because your well went dry.  Texas always has been a region of extremes, and our relationship to water bears that out.

 

Sources:  Besides the Wikipedia article "Edwards Aquifer," I referred to a Texas Monthly article on the Memorial Day 2015 floods at https://www.texasmonthly.com/the-daily-post/the-central-texas-memorial-day-flood-2015-is-one-for-the-history-books/, and a report written by Jack Ray D'Ottavio for the Texas State University Geography Department at https://digital.library.txst.edu/server/api/core/bitstreams/0365fd1a-94f3-4dd2-a825-c844ab27d456/content.  My blog describing some of the consequences of the 1970 flood can be read at https://engineeringethicsblog.blogspot.com/2012/08/the-day-submarine-theater-flipped-over.html.