Category Archives: Engineers

Politicians, Geologists, Engineers, and Water

Mosul Dam

Mosul Dam

This story relies on a report by Dexter Filkins in the New Yorker magazine.  Mr. Filkins,  a Pulitzer Prize winner, is one of the best writers covering the Middle East. 

The Fertile Crescent, where civilization developed, exists because the Tigris and Euphrates rivers flow from mountains in Lebanon and Turkey to the Red Sea.  The terrain along and between the rivers is relatively flat making agriculture feasible.  The rivers flood every spring, bringing water and new sediment to the region.  Those conditions support a significant population, but annual fluctuations have always created problems for the people living there.  During drought years, crops fail and famines ensue.  Wet years bring flooding which displaces people and affects farming.   

These conditions prevail in every arid region dependent on irrigation for farming.  The Nile, the Fertile Crescent, and the Colorado river are prime examples.  In all three regions, the political system has chosen to attempt to regulate the annual fluctuations in the river.  The solution?  Dam the river, store water for dry years and catch excessive runoff in wet years.   

Glen Canyon Dam and Hoover Dam on the Colorado,  Aswan High dam on the Nile, and the Mosul dam on the Tigris are the attempts at a solution.  So, they decide on a dam upstream of the people, hire geologists to recommend a good location, and hire engineers to design and build the thing. 

This worked, to a degree, on the Colorado and the Nile.  Not so well on the Tigris.  The geology above Mosul with its 2.5 million people is a jumble of sedimentary rocks formed in conditions similar to today.  That means flat coastal areas are intermittently flooded by the sea or nearby rivers.  The water evaporates, leaving the minerals dissolved in the water.  That means salt, gypsum, limestone, and a mixture of soluble minerals and mud called marl.   

The layers are deposited in flat layers, but Middle East geology is like Middle East politics, a big jumble with forces pushing from several directions.  Above Mosul, it is quite a jumble, but sinkholes have always formed as water dissolves the soluble minerals, leaving voids that collapse.  It is called Karst topography.  Florida is a prime example, a limestone peninsula in a wet climate surrounded by water.  It rains, the water sinks in,  dissolves the limestone, and goes to the sea.  Florida is dissolving, the rock resembling a sponge.   

The rock above Mosul has both limestone and gypsum.  Gypsum is a sulfate mineral that is called plaster if pretty dry, wallboard if more hydrated, goo if very wet, and then dissolves.  The geologists said “No, no dam, it will fail”.  The politicians then talked to the engineers who said “it isn’t good to build here, but we can make it work”. 

Now, engineers make their money by designing and building stuff, whether asphalt, steel, concrete, earth, or software.  They seldom say “no, we can’t do that”. They would be breaking their rice bowl.  So they proposed grouting the rock below and under the dam with concrete to keep reservoir water from dissolving all that gypsum, which is much more soluble than limestone.  They built a grout curtain under the Dam site, but it wasn’t perfect.  There were gaps. They built the dam, and the increased pressure from the water in the reservoir started dissolving the gypsum at a higher rate.   

Sinkholes developed below the dam before it was built.  They put a big long room made of concrete called a gallery at the base of earthfill dam.  Where their tests show a void is developing, they drill a hole in the floor of the gallery.  Water shoots out, confirming there is a big hole down there.  They then use big pumps to pump grout into the hole until it stops, hoping the void is filled.  They then move to the next place. 

This has been going on since the dam was built in the 1980’s.  All that concrete pumped below the dam has not stopped the leakage, it just moves the leaks to another weak spot.  They will never be able to pump enough grout.  An Italian firm is there now, and they are a bit hopeful they can control the leaks.  The confounding variable is the political situation.  ISIS controlled the dam for a while, and grouting mostly halted, but void creation did not.  The battle lines of the war today are within earshot of the dam.  The Iraqi government is unstable, despite support from shifting coalitions.  The grouting program is at risk.  Maybe that doesn’t matter.  The dam will fail, we just don’t know when.   

Sixty feet of water will inundate Mosul.  Refugee camps with 1.2 million people will be affected.  In two days parts of Baghdad would be under sixteen feet of water. Downstream, an even wider area would be flooded with at least six inches of water.  As geologists always say, “It’s not a matter of if, but when.”  Death toll estimates range from 500,000 to 1.5 million souls.  The Iraqi economy will be destroyed.  Moral, listen to the geologists.


Tacoma Narrows Bridge Collapse, 1940. The engineer commited suicide.

Tacoma Narrows Bridge Collapse, 1940. The engineer commited suicide.

Engineers design things.  It may be lines of code for a computer application or the Golden Gate Bridge.  They have been at it for a long time.  Stonehenge, the pyramids, Petra, Roman roads, bridges, and aqueducts; all started as an idea in someone’s mind.  He then added the details to make the thing work.   

The details.  You can conceive of a bridge over a stream, but it has to be assembled, stay in one piece, support the loads going over it, and hold back the flood.  It would be nice if it looks good.  In addition it should not cost more than is necessary.  That is asking a lot, and in most cases the product is good at its job.  Think of it, are the stream banks solid rock or mud?  How deep is it, how do you support the bridge as it is being built?  What material to use?  Stone, wood, steel, iron?  What about the approaches?  How do you get the rainwater or snow off?   

Roman Aqueduct

Roman Aqueduct

There are lots of questions to be asked, and the answers have to be backed up by the numbers.    Stress, load, vibration, weather, wind, soil characteristics, and myriad other details have to be calculated.  Calculations can be avoided only if the thing is so overbuilt that little harm can come to it.  It is hard to do stress analysis with Roman numerals, thus things were overbuilt enough that they are still in service today.   

Currently, overbuilding is not an option due to cost considerations.  The thing has to do its job, last for its design life, be easy to work with, and not cost too much.  I spent thirty years in the water treatment business, and everything in the business has engineering behind it.  Most of the time everything works fine.  But, engineers make mistakes.  Walls collapse, processes don’t work, the power to a pump shorts out, the concrete leaks.  When you turn the new thing on, the software may not work.  All the engineering is critical, because the water has to go down the pipe to the customer, safely. 

For thirty years, I treated water using the engineers products.  Sometimes the product was faulty, but we had to make it work anyway.  The net result of this is that after working with the mistakes for so long, I have a deep, strong, profound anti-engineer bias.  In addition, engineers tend to be serious nerds.  They often are weak in social skills, and have difficulty communicating with others.  Lots of them know they are right, and refuse to listen to input from others who are not engineers.  Mistakes get perpetuated.  I must concede, however, that their stuff mostly works. 

The problems can be minor, like not putting the drains in the low spot to forgetting to account for water hammer in a piping system and pipes separate, flooding things.  A big problem we had to deal with was leaking concrete.  Denver Water has been pouring concrete since about 1900.  A lot of experience is in the specifications provided to the contractor building a new plant.  The contractor failed to follow those specifications and water poured out of the filter walls.  Water also came up through the floor from the channel bringing water into the plant.  It was necessary to take the plant out of service, drain the tanks, clean the walls, and coat them with epoxy.  That epoxy will not last as long as the concrete. 

There was one major exception to my dislike for engineers.  The plant where I worked had elements dating back to the 1920s as well as new construction.  Part of the new project was automating the entire plant.  There are lots of valves, motors, pumps, blowers, and other equipment, all interdependent.   

The software developers worked for months writing the programs to run everything.  There were twelve foot diameter valves, 400 horsepower motors, sensors monitoring every process, and it all had to work.

Water Plant Control Room With My Doppleganger

Water Plant Control Room With My Doppleganger

When we turned the plant on for the first time, it worked.  Everything did what it was supposed to.  This in a three hundred million gallons per day water plant.  In contrast, I started up a 10 MGD plant that just barely worked.  The biggest design flaw was a tank that was supposed to even out the water flow coming from the watershed to the water demand of the plant, which tended to fluctuate.  There were valves at the intake up the mountain, at the tank outlet, and at the plant.  The tank was too small to handle the fluctuations.  The plant was either starved for water or the tank was spilling.  There was software to sense tank level and flows, but it could not keep up.  The tank should have been at least twice the size.   

Don’t get me wrong, the work was challenging, interesting, and sometimes even fun.  There was enough variety to keep boredom at bay, and those engineering mistakes added to the challenge.  What the engineers did right, we just took for granted.