Elaine Meinel Supkis
After writing about the looming disaster with the Wolf Creek Dam, I decided to look up the facts of many such mega-dams to see if any others were built on limestone and of course, this is the case with many huge dams such as the gigantic Three Gorges Dam in China, for example. And the 'repairs' on the Wolf Creek Dam turn out to be identical to a patch done in 1972.
Dyer, Duane ; Fanning, BillAbstract : Severe foundation seepage problems led to the necessity of a permanent solution at Wolf Creek Dam after an emergency grouting problem was completed in 1972. A board of consultants was convened whose adopted recommendations were to install pile type concrete walls through the embankment of the dam and the area between the switch yard and the tailrace. Because the general nature of the work was relatively unknown to District personnel, and the extent of the specific scope of work was extreme even for experienced slurry wall contractors, a two-step bidding procedure was established and eventually awarded to ICOS Corporation of America. The construction was split into two phases, with approximately half the embankment wall and all of the switch yard wall in Phase I and the remainder in Phase II. The walls are comprised of 26 in. steelcased, tremie concreted caissons on 4.5 foot centers connected by concrete elements tremied through open excavation. All excavation was conducted through a full head at bentonite slurry. The wall reached a maximum depth of 278 foot. Construction was accomplished from 1975-80 under the administration of the Nashville District, Corps of Engineers. Wolf Creek Dam is located in Southcentral Kentucky. Wolf creek dam; Slurry walls; Concrete diaphragm wall; Geology; Two step bidding; Tremie concrete; Instrumentation; ICOS. (eg)
Some time ago, readers of this blog raked me over the coals for suggesting mega-structures didn't take in effect the geology upon which they are raised and this hubristic approach to engineering buildings is leading to some real potential mega-disasters like we saw on 9/11 when the sheer weight of the solid concrete floors of the WTC caused those two towers to suddenly pancake at the speed of a steel ball in free-fall. Mass matters. No building on earth had the square footage per floor so high as the WTC buildings. The sheer mass and weight were in a class of its own.
So it is with the mega-dams. The sheer amount of water they pen behind their facades are many times that of lesser dams. Sometimes, a dam lasts for 75+ years without incident if they are built in the right places like Hoover Dam which is not on a bed of limestone or karst. The weight of the water, the speed of the rivers feeding into the system matters but above all, the anchoring of these dams is of highest importance.
All my life, I have explained patiently to people, 'The foundation is the alpha and omega of a building. A bad foundation means the building will be nothing but headaches and suffering and maybe even killing people.' Jesus said, 'Do not build your house upon sand..' and I agree. The geology of where one builds must be carefully examined and taken into account.
Alas, with rivers, this is skipped because most rivers flow in very bad places for dams! The Wolf Creek Dam, for example, is a toad's hop from the epicenter of the greatest earthquake in American history: the dreaded New Madrid Fault! The Mississippi river even makes a nearly circular route around this danger zone!
We know that a similar event which, by the way, is INEVITABLE, will destroy this dam. Completely.
But back when this dam was built, the memory of that epic earthquake which the early settlers left clear, concise records about, was gone. Everyone still remembered the infamous Johnstown Flood in Pennsylvania! But even that didn't deter the builders of this dam who thought it wouldn't reproduce the catastrophe of that collapse.
We can see from this article above, the foundations for this dam had to be sunk almost 300 feet. This is how deep I drilled my well on this mountain! We had to go through 175' of hard shale to reach a level that had groundwater in it! Above the shale was glacial till. Water flows right down through this till which is why my mountain has many springs in the middle of fields and fens. Every hollow has a spring.
&hearts The water table behind this dangerous dam is huge and deep.
Normal pool levels are 723 feet in the summer and 690 feet in the winter. Dam safety experts will continually monitor conditions at Wolf Creek and further reductions may be necessary depending on the effect that lower lake levels have on the dam. Lowering the lake level will reduce the risk of dam failure by decreasing water pressure on the dam and reducing foundation seepage.These changes are in concert with ongoing rehabilitation plans at Wolf Creek that address the problem of seepage through the foundation of the dam.
Because this is in the mountains, the dam could back up a huge amount of water that rolls out of the Appalachians. 700' is a lot of deep water! This means, if the dam fails, and the chances of this is better than 50% over the next several hundred years, an amazing wall of water will result. Running up the hillsides like the poor people in Johnstown did, won't avail much.
The other thing that amazed me, reading the stats on this dam, was the fact our government was trying the exact same 'fix' as in 1972: pumping in lots of grout. This 'repair' was coupled with re-enforcing the cement/earth dam's facade. But again, one can't fix a facade if the foundation is rotten. The more this dam is 'strengthened, ' the more the water will seek exit via the footings and water can and will and does dive very deep into the earth: this is how caves are carved in limestone that is hundreds of feet thick!
The water is constantly penetrating below, day in and day out. Any tiny hole or fissure is widened and drilled. Patiently, over time, the river's waters glide along the cold bottoms of the deep lake next to the dam and curls and pries away at the stones and dirt, always seeking a path downwards, down to the sea or deep into the earth.
&hearts Most of the dams I looked up are build on limestone!
The Three Gorges stretch upriver from the dam 118 miles towards Chongqing. Qutang Gorge is closest to Chongqing and at 5 miles is the shortest and most dramatic with 500 foot cliffs that have Mesozoic limestone peaks topping out at over 4,000 feet. The Wu Gorge is also noted for its sheer cliffs and 12 cloud-covered mountains. The third gorge and the one closest to the dam is the Xiling Gorge. It stretches over 41 miles and its cliffs looks much like an elegant Chinese painted scroll. Passengers on cruise ships usually leave their ships behind and board small sampans to tour the Lesser Three Gorges in one of the Yangtze's tributaries. The rising waters have made this area more accessible.Yangtze River cruise ships such as the Viking River Cruises' Century Star leaving Chongqing usually stop in Fuling to allow passengers to ride a hydrofoil up the Wu River to see the beautiful Lotus Cave limestone rock formations. The river cruise ships also stop at Shibaozhai (the Stone Treasure Stockade) on the northern bank of the Yangtze. This stone temple is a 12-story wooden structure built on a huge rock bluff.
This dam, if and when (it is only a matter of time) it collapses, will wipe the entire floodplain clear of any and all things built by humans. Nothing will be left, not even the foundations of buildings. Here is an article worrying about the dam causing potential earthquakes when the karst is put under great pressure from the ever-deepening waters behind the dam.
L. Chen, P. Talwani—A review of case histories of reservoir-induced seismicity (RIS) in China shows that it mainly occurs in granitic and karst terranes. Seismicity in granitic terranes is mainly associated with pore pressure diffusion whereas in karst terranes the chemical effect of water appears to play a major role in triggering RIS. In view of the characteristic features of RIS in China, we can expect moderate earthquakes to be induced by the construction of the Three Gorges Project on the Yangtze River.
A mild earthquake can open fissures under the new lake and this, over time can lead to water exploring the depths and finding interesting exits which hollow out the channels and creates caves. Karst landscapes are the home to many spectacular caves like the incredible Mammoth Cave that is many miles long! With towering ceilings hollowed out by flood waters over many centuries.
For when dams are built, they may stand for centuries during which the lands due to be flooded are built up by unsuspecting people. For example, one dam that stood for over a thousand years, collapsed suddenly:
Emperor Nero (AD 54-68) had a 40 m high, 13.5 m wide, and 80 m lonldam built for a pleasure lake near his villa at Subiaco, Italy. The dam was one of the earliest Roman dams and remained the highest the Romans ever built. Moreover, the Subiaco dam and two smaller dams nearby are the only Roman dams in Italy. Although the dam was to thin, it remained intact until it failed in 1305. Records blace the blame on two monks who took it upon themselves to remove stones from the dam, apparently in an attempt to lower the level of the lake which was flooding their fields.
I seriously doubt monks brought down that dam. The fact that it was flooding fields points to a flood problem and this probably caused the collapse as the water table rose too high for this old dam. It is astonishing to see one last so long. The Romans invented concrete which is probably why their dams lasted so long. They also were very particular about foundation work which is why so many of their constructions still stand today.
&hearts Here is the record of a dam built on limestone failing in Texas 100 years ago:
n the Friday morning of April 6, 1900, it began to rain at 4:30 A.M. It rained heavily for twenty-four hours. Shoal Creek overflowed its banks and washed away several homes. By dawn on April 7th the rain had subsided and people had gathered to watch water flow over the dam at a depth of eleven feet above the dams crest. At 11:20 A.M. the onlookers heard and felt an explosion. The flood broke through the dam and pushed two large sections about sixty feet downstream. The ensuing rush of water through the opening hit the adjacent powerhouse flooding the lower stories. Five workmen and three young boys were drowned. The flood swept downstream and inundated farms and houses in its path washing all away. Austin was left without water, power, or light. The private utility company that had competed with the dam was also shutdown by the flood. It took five weeks for water service to be resumed and five months for the electric streetcar service to be restored. The moon tower lights remained off until January of 1901. It was determined that the dam had collapsed due to "sliding". As water swept over the face it had eroded the limestone under the base of the dam on the downstream side. This continued until the water pressure behind the dam overcame the friction that bound the dam to its base.
Of course, the problem was, as nearly always, unusual rains coupled with the tendency of water to dissolve limestone. Rivers love limestone because it is easy to eat through. Given the choice of flowing through solid granite and limestone, rivers always vote to travel with the limestone. This is why it is so hard to avoid building dams on top of this limestone. The Grand Canyon is an exception, it being the result of a river running over landmass that slowly rises as the Pacific Plate is shoved under California. The river never changed course but continued to eat through the dense rock. A good place to anchor a dam...if the dam is very strong. Yet even that can be destroyed in an epic flood and we know that truly epic floods can and have hit Arizona and the states north of Arizona.
Recent experience with the construction of nearby dams indicates that earthquakes and complex subsurface geology greatly increase the cost and risks associated with building dams in the region. Unfortunately, publicly available discharge records for the Rio Usumacinta at Boca del Cerro end in 1983 (Fig. 5) and geotechnical studies done in the 1980’s have not been made publicly available. Nevertheless, since these initial studies were completed there have been significant changes within the headwaters of the basin that are known to alter the quality, quantity, and timing of stream flow. These changes include, the construction of hydroelectric dams and water diversions, deforestation and urbanization. The impact of these changes on the quantity and quality of stream flow at Boca del Cero must be assessed before any dam or large hydraulic structure can be adequately designed or evaluated. Likewise, similar analysis must be done for the entire, integrated project that is being proposed (Fig. 1).The site proposed for the Boca del Cerro dam is underlain by complex karsts topography of marl and limestone. The associated sinkholes and solution features are well known to affect the impounding capability of reservoirs and the structural integrity of the dam foundation. Recent experience with the Chixoy dam in Guatemala and the Zimapan and La Amistad dams of Mexico indicate the needs to conduct detailed geophysical investigations and subsurface preparations prior to dam construction. Similar studies need to be conducted and adequately reviewed before the recently proposed dam projects can be designed and evaluated.
All the 'safe' and many very 'unsafe' dams have been built. Now the last rivers must be dammed, Nature be damned. The rush to tap the energy and improve the landscape by creating lakes is very strong. We are like the legendary beaver in this regard. The economic pressure to overlook the dangers of building in places doomed to collapse overwhelms reason.
&hearts Here is another dam proposal with all the bad elements lined up, ready for action:
Vesuvius Dam sits in an area of unglaciated plateau in southern Ohio. The rugged topography of the dam site, with its limestone and sandstone cliffs, is primarily the result of stream erosion. The rock of the area is composed of sandstone and limestone with deposits of coal and low grade iron ore mixed in. The soils of the area are generally thin and cohesive. Core samples of the dam site taken in 1936 revealed about 15 feet of clay, sand, and slag that was waste material from the iron furnace.
Oh! Not only limestone but sandstone? Almost as weak! And mine till too? Oh boy.
I once owned a brownstone which is a muddy form of sandstone. The acid rain ate the front of my house which originally featured fancy carvings. They simply vanished. Marble is cooked limestone, heated immensely, and acid rain merrily eats it away, too! Every dam builder has to think ahead. All dams, once they are built, must be 'forever'. This is because failure means the death of everything and anything below. No walls, no animals, no cities or people can survive a mega-dam failure. The warning time 100 miles downstream is only minutes, not hours. No city on flatlands can be evacuated in one hour! It is physically impossible.
The two WTC buildings had huge floor spaces on each floor and were 100+ stories tall. I went in them a great number of times over the years! And with many staircases, it was still impossible to clear them of the poor workers there in time, and that was like a dam collapse: very sudden, little warning, difficulty in clearing out.
I suspect hydrologists and geologists are the last people who get heard when dam projects are instigated. And ecologists are completely suppressed. Not to mention representatives of all the families who will be displaced by dam builders. They all get swept aside as the grand plans progress.
I would, in the case of the Wolf Creek Dam, suggest they eliminate the dam entirely. If they wish to dam up this river, they should start from scratch and build where it is more sensible and frankly, over there, I don't see too many sensible places, off hand. Many smaller dams on the side streams would be the best solution but they won't generate mega-power and always, making money making energy is what this is really all about. Few dams are about flood control. Period.
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Colonel By, built a dam at Jones Falls, in the 1830s, it was the first semicircular dam in NA, it is still standing and in use! Take a trip up to eastern Ontario and see the Rideau canal.
Posted by: Big Al | January 30, 2007 at 09:21 AM
Yes, some fine dams were built long ago. Note the Roman dam lasted 1,000 years! I love to visit canals. Have walked along several in the Eastern USA, the famous Erie canal begins right here in the Albany area! Some of the locks are still in use today.
The whole planet has seen many vast dam projects. They are all over the place. And the dangers grow with each one since not all are built as sturdy as say, the one at Jones Falls. Sturdy vis a vis the volume of water penned behind or geological reality demands.
Posted by: Elaine Meinel Supkis | January 30, 2007 at 11:05 AM