Engineering Geology And Geotechnics - Lecture 12

you you you you you you you you you you I want to just go over briefly yeah hmm all right we are talking about recurrence frequency on floods this is my minor field advisor Berklee Luna Leopold is kind of the father of fluvial geomorphology he back in the 1950s Luna led the team at the USGS the Water Resources Division team that discovered that River depth and velocity in Crete increase as predictable rates as you go downstream so when Leopold was really good at was taking a lot of data and plotting it and doing it over a long enough period of time over and over enough different sized watersheds that you could actually start to see patterns in it and today he really disdained the modern academic model of publisher Parish because he said you have all these people going out and publishing things before they've studied them very long and what they end up doing is just basically following their PhD research in some narrow field and they just keep publishing publishing publishing publishing publishing publishing and and then later as they do more and more work they start contradicting the earlier publishing so your journals get clogged with a lot of useless stuff yeah and that's unfortunately the world we live in where quantity is more important than quality if you want to get promoted and so it's very hard for young people like you to look out there and say well what on the literature here is a value to me as a practicing engineer and what we're learning from practicing engineers is very little the practicing engineers basically don't even crack the journals open they don't even bother to look at them anymore because it becomes so clogged with a lot of minutia so it's hard to find what's in there that's really a value Leopold would study something for ten for 20 or 30 years before he published a word about it and that really unfortunately we didn't know our culture just doesn't allow for that anymore so one of the things that he recognized here look at this he's going across the board here you know looking at discharge in CFS from a thousand to ten thousand you know on up to a hundred thousand to a million CFS and what you see is the data is lining up remarkably well over many orders of magnitude this was a great great revelation when he first suggested it in the late 1950s now one of the things that this is still a very contentious subject is about levees and navigation on rivers so we've taken the modern flood plains and we've diked off 90% of them for agriculture because we got earth moving equipment that could do that starting around the time World War one ended in 1918 and that was a lot of that equipment came from the Panama Canal where they had been built and developed for the Panama Canal so what happens now is we actually see gauge height on the Mississippi River when we look at the previous data from 1861 until 1927 we see a curve like this relating stage height and discharge in Q then the cubic meters thousands of cubic meters per second and after we've channelized it and we've gone from a channel that maybe have been 5,000 feet wide to a confined channel that's 3,000 feet wide after the Corps of Engineers start took over responsibility for building these kind of things the 1928 Flood Control Act then you start getting curves like this that are much higher and this is very contentious there's still a lot of people out there saying no no no you know you got it all wrong as is not a problem but we really when we look at the showed you before when we just look at the number of breaks that we're getting and the height of the of the other floods we're seeing more and more damage more and more often we really got to be takin a critical look at this and thinking about you know maybe maybe we give back 20% 25% of the floodplain for flood storage if we want to keep our urban are densely populated urban areas out of danger so Leopold I recognize that several generations ago and it's it's gonna probably come to the fore here in the not-too-distant future I would imagine so part four see what I added there no on Nick points oh yeah the siltation studies Lake Mead I forgot to show you these Lake Mead was really really fascinating and Luna was around when this work was going on in the late 30s and early through the 1940s and you can see here the Colorado River coming out of the lower granite Gorge right at the Grand wash cliffs you get all this silty water coming into this nice pristine cool Lake and look at the subduction line right here just BAM in fact that was dangerous place to get your boat right in here because this denser fluid is coming in and being subducted under this cleaner lighter fluid and so if we go back and we look up in the Grand Canyon here we are 20 miles back up the Grand Canyon we have these fantastic silt beds that were deposited back in late 30s early 40s and then we had a big big another high water sequence didn't occur again till 1983 and that's when these beds were actually deposited and then after the 83 highest and what we see is this is pictures taken in 1984 it's the next year and you can see actually 85 taking two years later and these things are already starting to be eaten down and taken out and redeposited now this last decade at Lake Mead we've seen the lowest lake level since Hoover Dam was completed 75 years ago this actually shows how they were tracking the advancement of the deltaic front into the reservoir as the reservoir was coming up 1935 36 37 and then right up here 42 to 48 about where was maintained they actually brought it up to the maximum level for spillway tests between August and November 1941 and they brought it back down to this position here now the big surprise in all this were the density currents that subducted under the water up here and then flowed 116 torturous miles on a very low hydraulic gradient all dead near zero right to the dam face and the dam had about 175 feet of sediment put into it the first decade which shocked the heck out of everybody every scientist was shocked in fact I learned about this interviewing vetova Nonis at Caltech who was without any pure he was to channel hydraulics with Leopold was the fluvial geomorphology in the 20th century in Vernonia was a really really bright star lived to be in his 90s and the way they found this was the concrete started heating up down here they had put thermocouples all over this dam to measure the heat of hydration because without the cooling that they were doing on the dam it would have taken 150 years to bring it down to the temperature so they had all these cooling pipes they had run all this cold water through it before they could keep adding the concrete on and so they had all sorts of instrumentation on the dam was the first dam in the world built with a lot of instrumentation and they were getting 70 degrees down here where they shouldn't be getting anything you know over 50 degrees and so they did some soundings and then they took some tests and they pulled out this very very organic sediment which had a bacterial count about the same levels that you'd have on a municipal sewage treatment plant in a major American city shock the heck out of everybody they're going to wait a minute everybody just drinks out of the Colorado River well you shouldn't be in the summertime when you have warm water Colorado River runs way above 70 degrees the late summer in those days before they had dams and reservoirs on the river and they had a lot of people die down a rag town in August 1931 people actually developed they were pulling water out of the river and they were just letting the silt settle out of it and they forgot about the bacteria you have in there when things are hot things are warm and they had a number of people died will see women and female teenagers so they shut the whole thing down and they they ascribed it to two heat prostration but it was heat prostration and gut problems with you know drinking bacteria high bacteria levels in this water so sedimentation studies that occurred at Lake Mead and the turbidity currents that they discovered were incredible discoveries and in the mid part of the 20th century and this actually shows one of the papers that came out of Caltech without Nonis students at that time well you're way back here you have this advancing Delta upstream of the lake level remember this is occurring upstream of the lake level the lake has an impact upstream many miles upstream and you're having this heavy sediment gets abducted right here and then flowing as a gravity turbidity channel deposit all the way through all these torturous bedrock canyons and when it comes down to the dam look what it does hoosh comes up so they actually had a big pile of sediment against the dam and not nearly as much in Boulder Basin back here behind the dam and the sediment piled up and today it's about 200 feet deep behind the dam itself and so they actually did similar studies american geophysical union and the USGS and the bureau reclamation and TVA Tennessee Valley Authority started looking at Lake need at Elephant Butte dam on the Rio Grande River in New Mexico and at Norris dam on the Tennessee River and so those those were the three projects they monitored throughout the 30s and 40s to look at this phenomena of turbidity currents okay I think that's this is the reservoir area capacity curves for Hoover for Lake Mead as it's originally built originally built with nine and a half million acre feet of storage that's ten times the size lake of the ozarks that's just the annual flood storage they built this thing with this colossal and then what the stage curve looks like today they lost about three million acre feet that was bigger than that's the in 30 years that was larger than the largest reservoir in the world prior to the time Lake Mead was was filled in the late 1930s so that figure just drops to nothing after Glen Canyon Dam was completed 1964 and they started storing water in it in March 1963 and so today they don't maintain anything close to nine point five million in fact that even get over four million today on flood storage but they haven't had the reservoir full since 1984 and here's what the sediment looked like about every 30 years they go out and do side scan sonar on the reservoir floor and if you take a digital elevation model what you'll see is this is all deposition by turbidity current deposits it just fills in the lowest areas just like soft plaster you could land a 747 on this server it is so perfectly flat this is Las Vegas Bay Boulder Bay here's the dam lay around over here in Black Canyon just fills it up flat as a pancake so these were really incredible revelations when they were first being studied back in the 1950s so I wanted to give you those little tidbits that I had forgotten to tell you before let's see there's anything else I changed I don't think so that was it okay so we're going to go on to chapter 9 which is land subsidence and the homework problems are not going to be nearly as many to do I think there's only a couple we go to page 385 386 I think there's three three problems so I want you to do those three problems read the chapter and do those three problems they'll be due next week and I just want you to get a an idea when they talk about some of these concepts I just want you to have a general idea this this is really stuff that is very very important in the urbanized parts of the world and it's out of control in some places especially on the Asian continent and in semi-arid areas so we're going to talk about land subsidence and what that means and there's a lot of things that cause land subsidence this is Kilauea iki crater you know on the Big Island of Hawaii and this this subsidence is due to the expulsion of magma from lower chambers and so the the caldera up in the the crest of this volcano just you know is settling down so a lot of different things that cause settlement and groundwater withdrawal is the one we talk about the most probably in school and when we look at groundwater flow oops we have a capillary zone of aeration which is above the permanent groundwater table that's the zone of aeration so up here we have gas pockets we have air voids and down here we have complete saturation now when you get into fine-grained sediments like along the Mississippi River floodplain or the Nile River flip anything any of the world's largest rivers you have big long miles of silt floodplain you can actually get capillary rise and this is on 50 feet high so that's you got to be real careful in there the only reliable way I've ever found of really picking up the zone of saturation is with a cone penetrometer that actually has a temperature sensor and when you go across this boundary this 1 centimeter right here you'll see a 7 5 to 7 degree temperature change well when you're in something like the Mississippi or the Nile you try to put in instrumentation you're going to have to watch it for 6 or 12 weeks and spend a lot of money compared to using the temperature device on the cone penetrometer that's really the only reliable way when you have a high capillary fringe zone which is typical on larger rivers and streams ok well how does the water actually flow through the ground what flows on a very torturous path like you see here scribe in the red line and how do we approximate that in engineering calculations we use straight line approximation and assume linear flow just easier mathematically we can't handle this kind of non-linearity mathematically it'd be very very costly to to model this and so what we do is we go out and we put wells in the ground over here and over here and over there and then we use the fudge factors based on the observations in those wells to run our groundwater models so our groundwater models like our slope stability models are not accurate from a scientific point of view they're tweaked to work from an engineering point of view they get to the right answer for the wrong reasons because it's mathematically too rigorous to get there using the right reasons so you you know a lot of people and your generation I feel sorry for you're going to be using these you know 50,000 dollar computer programs and you're just going to believe them because you paid so damn much money for them and the sad part is they are going to fail you as often as they help you and that's where you need to have the old gray hair of experience looking at it and saying that number doesn't look right and the big problem we have is heterogeneity we have heterogeneity we have places where we're going to get different answers for different reasons which takes me back hang on a second there's a slide I wanted to show you in floovio processes which I didn't get to see hmm well let's let me down here I don't see it I just changed it today so it should say modified today I don't see when it says modified day than the two I showed you now doesn't it let me look ya partner and see now it's where we talk about point bar deposits huh that's mystifying I put that in there hang on a second I really want to show you this it's an important slide hmm sorry what well I mean by date well yeah but Excel and I'm not finding as today's date which it should be one man one of these that should have today's date on it I'm not seeing it so I just changed it in the last hour and added it in all right well shoot yeah this is where I put it in right here it's not there all right something went wrong hmm I don't know what that's where I inserted it right there right there actually between 10:00 and 11:00 all right Wow I don't know how that happened all right well we'll continue on with this I'm sorry all right so water table is the by definition as the upper limit of the zone of saturation and where you have variations in the water table you can have bad things happen and the shape of the water table is usually a subdued replica of the surface topography and so the better model you have a sort of topography a better idea you're going to have of the water table so one of the big things we get into our drought impacts when we have a large volcanic eruption like we saw this past week in Indonesia that causes changes in weather patterns and it creates wetter weather in some parts of the globe because of the the expulsion of sulfur dioxide into the atmosphere which collects as sulfur dioxide aerosol at the troposphere stratosphere boundary and it reflects the sun's energy and lowers sea surface temperatures so that can cause greater rainstorms on El Nino effect on the Western Hemisphere South America and North America and it can create in other parts of Africa and the Indian Ocean basin it can create periods of dryness of extended drought and so when you have precipitation deficiencies and you go into drought this is where you start having a chain reaction or a domino effect that really exacerbates ground settlement so as you already had people overdraft in groundwater and now you on dry weather and you exacerbate the problem so variations in groundwater are very hard to really appreciate because the examples we give you in school tend to be overly simplified you can actually have groundwater piling up in the ground with big changes over short distances if you have something of lower permeability in there so if you don't have it just a nice layer cake geology but you're not going to have in places that are tech tonically active and actively depositing that was the slides I wanted to show you you can actually have these groundwater mounds that locally influence things so if we look at the the basic types of gaining and losing streams we're in the something like this where we actually have a lot of water in a tropical area and it's coming down and it's basically coming up and feeding our stream we call that a gaining stream and if we're in an area where the water is a flowing down this river this would be like California we have a losing stream we actually have Bank losses in these areas this would be areas that get less than 20 inches of rainfall a year this would be areas that get more than 20 inches annual rainfall per year typically so you have your Cal Cal collide soils here you and you have your humid semi-humid conditions up here and then we have Missouri the Ozarks which is a karst system car system you have to throw out everything and it's much more complex because you have channels that only occasionally may have water in them that are then feeding down into a water table but that water table is very very stable you can come in here and pump and pump and pump and pump your pump till you know you have a libertarian president and you're still not going to change the groundwater level a whole lot okay so interaction between the groundwater and the streams is something then you have to understand when you're putting your model together you know do I have a gaining stream environment do I have a losing stream or do I have a combination of the first two well you can you actually get combinations it's one of the problems they have over in Tennessee they have a big well-developed karstic Network but they have these huge ancient river networks as well and they actually end up having a combination problem and of course computer programs aren't written for combinations that's too big of a PhD they're written for you know one of these type of thing and so sometimes you can get in where the situation changes and you go from a losing stream to a gaining stream because you had enough years of wet weather well here's the theoretical movement of groundwater and this has been proven out with isotope studies isotopes of water deuterium oxide is one of them and and you can actually go in here and take water samples a depth and get some idea of the age of this water this water and that water and what you find out is you got this water way back here it doesn't travel in a straight line down to here it actually takes the Great Circle Route goes way down here and then comes back up here so this takes a much longer travel path than the stuff right here so they're not moving linearly with groundwater the first thing you got to do is get linear out of your brain and realize that everything is curvilinear go by a French curve look at curvy figures get yourself out of the straight edge environment okay because ain't no straight edges in geology that's why males are attracted to it so much maybe I don't know storage and movement of groundwater well the percentage of the total volume of the rock or sediment that consists of pore spaces is the porosity now a hundred years ago there are a whole bunch of lofty papers written by a whole bunch of engineers with lots of college degrees called hydrologist the early hydrologist William Mulholland of Los Angeles is one of them prominent and he says you know we don't have to ever build a dam in Southern California we have so much groundwater stored out here in these porous gravels of the San Fernando Valley in the San Gabriel Valley all we got to do is drill a hole and put a straw in then suck the water out and we can support 15 million people well that's that was the theory because theoretically the water is there but it turned out when you put the straw in you couldn't suck hard enough to overcome capillary attraction that's down there so we have something called specific yield Pacific yield is the actual amount of water you can get out of the ground by just doing something like pumping under one or two three atmospheres something low so turned out it wasn't nearly as easy as everybody thought in fact LA can't support more than a quarter million people with the natural water resources they have they have 17 million there right now so the only way they do that is they go hundreds and hundreds of miles away and they bring down aqueducts one from the Feather River one from the Owens River and one from the Colorado River and that's how they're able to support so many people there Denver has the same problem they have to go the west side of the Continental Divide to get their water so some of the things we look at our permeability which is hydraulic conductivity with respect to water we're just talking about water we're not talking about oil here and then we look at aqua tardes and aquifers now permeability is the materia is the ability to transmit the fluid you know how many centimeters per second does this fluid move under a given head now that's a real dangerous number that gets misused because people forget that when you go to the laboratory and you're on the ASTM test and you're in your geotechnical laboratory you're only running the test for one to two PSI head difference you go out to Hoover Dam 500 psi you'll have one or two we have a whole lot more than that and you can actually force a lot of water through a very tight crack under 500 psi which you can't do in the lab under 1 or 2 psi aqua tardes are relatively impermeable layers that hinder or prevent water movement such as clay clay is going to come up over and over and over again if you're going to have a career as a geological or geotechnical engineer clay controls everything whether you have clay or don't have clay makes a whole lot of difference aquifers are permeable strata that everybody wants to have on their ranch because when you put a hole into an aquifer you can get all the water out you want or so you think so sands and gravels make great aquifers but they're generally laterally restricted what is laterally restricted being dr. Rogers that means if it's on your property it's probably not on that one over there that one over there that's what I mean it's laterally restricted so sometimes you can go into a gravel and get all kinds of water I had lots of them in California I started out at 2 or 3 150 gallons per minute in the week later I was getting 20 and 3 months later I was getting 6 because it's laterally restricted there's only so much water in there and so sometimes you know in California man you're lucky to find a well with free gallons per minute sustained that'd be laughable around here in the Ozarks and the Ozarks you put a bigger straw in as you want and gulp away cause you got karst around here that's why we got so many mosquitoes - all right so movement of groundwater one of the things we have to appreciate about it is it is exceedingly slow very very slow unless you're in karst around here we have karst we go fast and go a mile in a week around here no problem back we can go six miles and 13 days around here energy for the movement is provided by gravity so you have to have a higher zone flowing towards a lower zone and Darcy's law which has been around 200 years now Henry Darcy was an engineer civil engineer and lyon france trying to get their municipal water system working in the early 1800s and darcy you know q equals k IA he said the permeability remains uniform the groundwater velocity increases as the slope of the water table increases and so that's a pretty fundamental theorem to keep in the back of your mind all the time and it's a two-dimensional theorem but it really works well under controlled situations of course Darcy intended it for pipes it intended for you know looking at groundwater modeling although we use it for ground it's very useful for ground water modeling Darcy's law basically recognized a hydraulic gradient the hydraulic gradient is the water table slope s the water table the water table has a slope to it that provides energy head that pushes the water now when you get into clay you need a real steep hydraulic gradient because you're trying to push through something that's impermeable so when you put in dewatering wells on a clay site yikes that's really testy you know how far apart we put the wells 20 feet 10 feet five feet two and a half feet depends depends how much you want to settle the building's around you and this is one that dive out that's really a problematic you have to learn this in the place where you're working your cannon Shanghai or Taipei wherever it is you got to figure out that this is really dangerous if you get into a channel and start withdrawing a lot of water you can settle everybody's building who's built along that channel up gradient of your site so you really got to make yourself an underground map of all the channels and figure out what their relative permeability is is this stuff is really dicey because when you're talking groundwater flow things change in a short distance by orders of magnitude six orders of magnitude is not uncommon or impossible six orders of magnitude yeah clay - gravel six orders of magnitude can be nine even so this drives people nuts in places like dams where you start grouting and you find you have this you know nine orders of magnitude difference in permeability for your grout penetration yikes hydraulic head hydraulic heads the vertical difference between the recharge and the discharge points now that's the one that can get us into a lot of trouble as well if it changes if you put in Lake Mead put this big reservoir in there Lake Powell you're going to change the ground water regimen for that whole drainage around that reservoir because you got 500 feet of water you know running over huge 100 mile area you're going to change things so here's the basic premise we're just talking about we look in the ground here we say there's the groundwater table under the ridge the groundwater table tends to mimic the topography see that mimicking you see this thing pinching out down here and so here we're in a nice humid environment with more than 20 inches of rain a year we have a gaining stream and we're looking at here we're looking at a well located here and a well located there and we're saying there's the change in head between this location and that location and we're using a D that is what straight line approximation wrong wrong wrong wrong but that's what we're gonna use remember that your PhD or elles if you get hydrologist in there you might ask you that question okay we use that straight line D but that's not what it looks like what does it do from back here oh that's hot moves anyway this is how we approximate it that's never between a scientist and engineer the scientist wants to know what's actually going on and an engineer says I don't care what actually going on just give me the number and I'll give you the answer I solve problems I don't study things okay I'm bipolar I have both those in me sometimes I'm real curious I want to know it other days I said no I want to go home tonight I'll give you answer get the hell out of here okay so I hear that's an approximation but it works hydraulic gradient I is the change in head over the flow distance D and it's a straight line approximation so I realize you're going to be you're gonna guess wrong 99% of the time you got to be too high are you going to be too low I just want you to be aware of that so you don't bet too much money on this stuff and lose your shorts okay you want to keep your shorts on all right storage and movement of groundwater how do we actually trace this kind of stuff well a lot of things we can do with fluorescent dyes and we use fluorescent dyes all over Missouri and we get a lot of every time we use them we're going to get some surprises we put some fluorescein dye in here in the water instead of staying in the natural watershed which we see on the topographic map that water sometimes goes over here into the next County into a different watershed welcome to karst Kars you never know what you're going to get it's like going on a blind date with one of those computer dating services and the picture has been touched up and she's gained at 80 80 pounds it's a picture with egg and okay so that's a car so like karst is the big kahuna mama you got to watch out carbon-14 to date the waters last exposure to the atmosphere that's these isotopes I was talking about and we get into those kind of things when we get into testy situations like Superfund sites where we really want to know hey do we have to worry about this bad stuff these dense non-aqueous phase liquids dean apples going over here and polluting the groundwater I don't think so you know I got an a Quatar down there and it's a shale blah blah blah blah well the way we tell is we go out and we do isotope tests to see how old the water is that's protected by that aqua so Darcy's law developed for pipe flow Q quantity of water equals the coefficient of permeability times the cross-sectional area flow times the hydraulic gradient the hydraulic gradient I is changing head divided by the flow length and Darcy found this empirically and it works great for pipes that's why you have to have so many storage tanks around the town the farther away you get from the reservoir the more head loss you have with the increased flow in the pipe pipe friction and so you look around Rolla we have these big tanks around the town strategically on top of the tall hills you don't put the water tanks at the bottom of the valleys all right inner flow we've talked about inner flow before inner flow are the springs this is the wild card it's the wild card now in karst areas like the Ozarks the inner flow numbers are very very respectable they're huge and they're very very constant they're pretty reliable you get to other places like out west of 100th meridian and spring flow is anything but constant it's going to be different every damn day of the year every year that's what spring flows like when you go out to New Mexico Arizona Nevada of California you're never going to see much repeatability because you always have different antecedent flow conditions terms of precipitation so it's the natural outflow of groundwater that occurs and it can be caused by aqua tardes creating localized zones of saturation when you get out west most of the times spring flow or inner flow is controlled by fault zones fault zones have fault gouge fault gouges made out of clay clay under high cata clastic sheering can have a permeability 10 to the minus 9 centimeters per second so it's very very effective aquitard all right well here's an aqua tarde it's a simple one this is a shale bed an old lake bed or something that's buried in the geologic unit here so you have rain in water that percolates down hits the aquitard and gets perched on it most most shale units are aqua tardes and you have a semi confined aquifer condition here above it and so that can be great because you can get little springs along here on top of the shale and that's very very common where you have Springs because you have landslides later sooner or later down here beneath them and then you have a main water table that's down here at some depth that's not being influenced by the perched water table so that's actually pretty common in the Ozarks we have lots of aqua tardes here and some of them are dolomite some of them are quartzite some of them are shale yeah there's some Pennsylvanian shales that that make really nice aqua tardes over in the st. Louis metro area Springs and karst some of my favorite stories this is VAE sees Paradise River mile 31 and in Marble Canyon going down to the Grand Canyon this was named after John Wesley Powell named this in 1960 in 1869 after a botanist that he had worked with Vaizey on some of his previous trips and notice you actually have free free outlets you have the main outlet here you have an auxilary one here and then you have a high one here and the high one only runs when there's a flash flood condition underneath this and a young spelunker named peter Huntoon picture of him here in 1966 he did his PhD in hydrogeology one of the earliest PhDs in hydrogeology in the karst of the Grand Canyon he loved to go in the canyon and go climbing up into these caverns like vases paradise and he'd go back in these things for miles and mapped them and he produced those in his PhD thesis which came out University Arizona in 1969 and if you are a Grand Canyon bibliophile like me I started working there the generation after him so I started working this is 1978 my first trip down the river way we took his thesis drawings and then we would go in these caverns and go way back in them and of course the big question was trying to solve was where does all that water go that rains on the Kaibab plateau because it doesn't appear to come into the Colorado River if you look at all the Springs on the Colorado River they should have a lot more water coming off the north and so Huntoon set about trying to solve that dilemma by going inside these caverns at the major underground rivers and putting in Weir's and measuring them and trying to figure out what the lag time was between the precipitation events way up on the plateau a mile above him and where that water came out and he was actually in vey C's paradise in 1966 when they had a major event and it occurred exactly 48 hours after the storm above and he and his buddy in there came with an eyelash of getting killed they actually were they could hear the flash flood coming in the cavern because sound is ducted down there so they turned just like a Steven Spielberg horror movie and go oh my gosh we better get the heck out of here and they start running try and get out of there they got there they're a little light on their head and everything like you see right here and they run and they run and and the flood gets them they can't outrun the flood it gets them and they feel like we're toast too bad we didn't bring jelly with us today and put in our pockets because you know we're going to get cooked here and see someone's catching the jokes and and so they got caught up in this thing and they got spit out out of the hi hole and what happened to them when they fell here 60 feet well you know broke some limbs you know that's what happens here they're lucky to be alive and tell the story so broke several bones they got out of there and they got deposited down here on this fan and but they lived to tell the story about it so you want to read an exciting PhD thesis that's the only one I ever know that didn't put me to sleep I like I stayed up all night long reading it because it was just so good you guys are going whoa baby boom oh man I can't hardly believe it anyway it was it was better than any of the sites and some of you guys spend all your time on hot springs and geysers these don't get into our consciousness that much but they're a huge engineering problem because you have to look at the solubility coefficients and you have this all sorts of exotic salts especially potassium salts and phosphorus and iron and things that really create havoc with engineered structures in terms of causing deterioration rapid deterioration of things like reinforcing steel this is out it of course at Yellowstone National Park which is there's a colossal size national parks like its own state it's so big it takes you a long time to see it they have these hot springs all over the place because I'd say a place where we have three major suture zones in the North American crate on that intersect it's a hot spot that hot spot has been responsible for all of the Snake River plain volcanic s-- going back to the early Miocene so that is gone from Malheur County Oregon all the way across Idaho and turned up and is now in the northwest corner of Wyoming and they have major eruption sequences about every 50 thousand years off that zone and of course the last one was about 50,000 years ago so if you want to buy real estate in that area anyway we have meth labs around here so anywhere you go you're going to have your your hazards the geysers are intermittent hot springs which erupt and of course when these things erupt what it's testifying to are big changes in effective stress down here and the fact that you have a buildup of heat and that water expands and has to then itself out if this was something you had to deal with of course there's all kinds of things you could do to tap into this thing and to vent it out and run a geothermal plant with it that's come a long way here's how it works you get superheated water down here because of the hot crust maybe the crust is thinner in this area there's fracture systems and so this thing heats up and then it periodically vents out what they're doing now on some of these sites is they're actually injecting water over here on one side of it letting it go across the chamber get super heated up and withdrawing it over here maybe a mile away and that's become one of the preeminent ways of doing geothermal geothermal very very debatable and testy one of the things if you don't take this water that you take out and put it back in the ground you're going to cause settlement if you have unconsolidated settlement unconsolidated sediments and that's what happens in Baja California the Mexicans government has two geothermal plants near Sierra preto and the Colorado River Delta they just take the water out and let it evaporate in these large ponds they don't bother to read it so they are getting colossal levels of settlement three meters of settlement since the plant opened in 1973 that's over ten feet a vertical settlement and I run Toshiba turn turbines on it in the United States you can't do that if you do geothermal power here you have to react an equal amount of water the eeeek balances the amount you're taking out because of the ground settlement implications which we're going to be talking about all right if we look at the distribution of hot springs in the United States the big red spot that'd be Yellowstone right there is it a big red spot and then all these others are associated with faulting and late tertiary quaternary volcanic s-- so there's lots of hot spots to pick from we even have Hot Springs Arkansas which the Mafia loves down here and other people like it to churches Baptists everybody you can always tell if it's a mafia person they're drinking if it's a Baptist person they're reading the Bible but anyway they all go to the same places down here neat tourist destination you notice we don't have any tourist destinations in Missouri that's why it's good for you to go to school here you don't have the distractions you have other places gotten a few of them up here between on the border between Virginia and West Virginia as well which I'm really been tapped much chemical sedimentary rocks accumulate where you have geysers this is a again some of my work and the Grand Canyon way back when we have this travertine rich waters this is a little Colorado River this is Havasu Creek Havasu Creek actually has a drainage area four thousand square miles so small wonder they have some water coming down and this is actually the the bathtub rings at Lake Mead and those are in black Canyon right there's a picture I took in junior high school actually right from the dam on the Arizona abutment these are actually deposited just during that three-month period when the water was high in 1941 so it doesn't take long for carbonate to get deposited now water wells if you go out and look at water wells water wells go back as far as we go back we look at the earliest Roman engineering it's all about digging wells not about building bridges why would digging wells be so important to the Romans and so important to the Americans when we went into the Middle East in 1994 the Gulf Gulf War number one well how long are soldiers going to last without water not long yeah you can call Culligan man to come out and give you the water and so early roman officers were taught the rudiments of geology and engineering military engineering preceded civil engineering by several thousand years and the whole purpose was to learn how to excavate wells because wells in the middle east are what made land valuable just like they are in southern california price of land in california is directly related to whether you got water going out water same thing in Arizona New Mexico Nevada anywhere you go west of the hundredth Meridian value of the land depends on water so when you drive it along interstate 40 and you're out in your Grand Canyon you see these these these big roadside signs say you can buy a forty acre ranch for twenty thousand dollars now somebody's from LA go 40 acres could be land bill and yeah because Cal California you're lucky to buy a quarter acre the problem is no water you got to bring your own water you want to drill a hole in that part of the world South Rim of the Grand Canyon you got to drill about one mile deep they get any water a mile deep see what's nice about the Ozarks don't have to drill is deep around here lots of water alright but we have to be careful if we just go out here willy nilly and drill and we're not in a karst area we're outside Missouri we're over in Kansas maybe this is what can happen we can actually get a cone of depression off this well depending on several things how permeable this is and how much recharge and how much Q we're sucking out of this thing now if you get it down anything like this you're dead that's a dead whale I mean you always want this thing going about 33% deeper than the deepest point of your drawdown because you got sediment collecting in the base of this thing and you don't want to put your pump down in the base of your well casing anyway so this is Nick this is a cartoon case maybe you've got anything like this you're you're dead at this point you're calling the driller and saying drill me a new well and so here's you know this Wells gone dry this Wells gone dry because this guy over drilled the aquifer and these kinds of things actually did happen all over eastern Colorado and western Kansas and all across Nebraska back in the 20s 30s and 40s they over drafted the Ogallala sandstone aquifer artesian wells were really explored by the Italians Italian the Romans started building a very sophisticated system of water supply for Rome and when they did that off the Rubicon River and off the they had these aquifers they would tap into they found out pretty quickly that the highest they could get the the fountains to go would be 33 feet which is one atmosphere and so they figured out that you had this artesian condition and that the more you tapped into it the lower the fountain would go and so that was the first discovery just like with the their work on volcanism with down at pompeii and herculaneum they figured out that there were different types of artesian wells that were non flowing and flowing and that they're both valuable to both non flowing you're not going to get the the fountain going but this became a really big deal that everybody else emulated all across Europe so as Europe got populated towns tended to be founded around places where you had artesian wells and you had a public source of water that was reliable that everybody could get to and go down and fill up their water conveyance jars or whatever they had now in North America we usually show this particular picture and this is the you know the Rocky Mountain area uplift and then we have these confined aquifers like the Ogallala that come way out here and go out for hundreds of miles out in the prairies and when they started developing drilling technology in the late 18th century the 1890s and electrical pumps came on beginning around 1890 to 1893 now you can go out here and drill and the water would just come right up because it was artesian so that's how they were able to settle so much of western Kansas and eastern Nebraska now is they kept going and started over drafting it they had to start putting pumps in so in the 1930s the drilling technology got better but you had to put in you had to get electricity or make electricity with the wind male ISM and then put a pump in in order to get the water out now the wind male just using pure wind male energy that goes back much further that goes back in fact a Union Pacific had one well thousand feet deep and western and central Wyoming where they actually went down and used had the world's largest wind mail to try and get the power to pull it up that far but what happened here is they basically started over drafting it and so you saw them lose the hydraulic head hydraulic head eventually got diminished and they had to start managing all the water and the states got into the water management business and usually the state's contract with the USGS Water Resources Division to help them manage so that's really the USGS you know has two huge roles one mapping the country building making the maps and two is actually the management of the groundwater resources that's really where they've had this you know huge tentacles that go out all over the place that most of us don't think about it's not like they go out and find gold mines and stuff like that and and do that the hazard stuff that we see them in the news doing now the water stuff is you know 24/7 it has to be managed very carefully or people are going to go thirsty so here's the Ogallala sandstone goes from central Texas all the way up into southeastern Wyoming all the way across Nebraska I mean basically all of Nebraska has the Ogallala underneath it you can see here western Kansas the western panhandle of Oklahoma and the Panhandle area of even down to the Permian Basin and up here into northern Texas so they started drilling it from the mid 1890s on and by the 1930s the formation had lost its artesian head due to over drafting and that was a very dry period is called the Dust Bowl period in Oklahoma because they were doing dry farming and the only way you could have wet farming out here was to poke holes into the sandstone and pump the water out artificial systems are what we use like this is similar to the kind of system that that we actually saw developed in Lille and France and the early eighteen by Darcy well he put the tank up on the hillside on the mountainside we when route in someplace that's flat like Kansas we actually put the water up into a storage tank and the idea here is to get enough pressure head that we can drive that water through a pipe conveyance system out so far and typically we operated heads between 120 psi and 20 psi 60 is a pretty average number for a municipal system and he I had a house in California for 25 years where I was right on the distal margin the guys across the street had a different water company coming from Oakland my water company came from from Concord Martinez Pacheco and I had barely 22 psi head that was on the best day so it was very very low doesn't have much pressure on my hoses or anything now you get over to Hawaii I had clients over there because they had a lot more hills where they were having bursts than their water lines because they were operating around 126 to 140 that's really at the upper end of a municipal supply system 140 you're going to start breaking a lot of especially plastic valves and things because plastic valves are subject to creep what are some of the problems now where all this is going is now we finally got there I don't slide 25 or something you know what are the problems associated with groundwater withdrawal well there are many there's all kinds of them yeah you can't treat groundwater as a non-renewable resource if you just start withdrawing it withdrawing or drawing and not managing it you're going to pay a huge price for doing that and you have a subsidence problem because of change in effective stress when I put something under water especially a long way under water the water is incompressible it's got a Poisson ratio of 0.5 put 10 pounds of load on water 5 goes this way 5 goes that way it holds load it doesn't affect bearing capacity it helps bearing capacity so a high ground water table the only ways we avoid that with buildings is they don't want to get dry rot but we keep the groundwater down a meter we're going to be fine we're going to get dry rot usually so the problem here is when you pump the water from wells faster than it recharges you get a net drawdown of the water table that's going to increase the effective stress and now that clay that's down there is going to consolidate under the increased dead load that it feels because the water table is going down and you get some alarming levels of settlement we're going to talk about that so if you look at something like this this is a Santa Clara Valley Silicon Valley where San Jose Santa Clara are and the south end of the San Francisco Bay and if we look in that area we have these clay layers here these are old lake sediments because we have a very flat gradient and sea level basically used to be down here and as sea level came up over the last 11 thousand years you had all this basin filled in with sediment 500 feet deep filled in very very rapidly geologically speaking so now you have these clay lenses here which are really problematic because if you start drawing the water table down dramatically which they did from 1890 to 1933 these compressible units settle and they settle a lot a few inches to a few feet and so if we actually look at that we can see this when we fly around places like western Kansas western Missouri all over Kansas Eastern Colorado you see these well points where they're withdrawing out of some aquifer then that's running a circular sprinkler system off that point so that allows us to grow crops we otherwise wouldn't be able to do easily but we have to manage that groundwater resource if we overdraft on it then it's just going to get more and more expensive every year and also when you're in an alkali type soil you have to keep flushing your actually every time you have an agricultural crop and the the the water is getting transpired out by the crop the the salt that's in that water there's any kind of dissolved salt tea PDS total dissolved solids it's going to precipitate out and you're changing the soil chemistry every year you're there so one of the great you know one of the big lies I was always told in school was you know Los Angeles we're mean bastards because they went up to the the Owens Valley and they stole the farmers water Mike my kids at Berkeley would always tell me that you know they went up here and they stole the water and I said but yeah a lot of all people in LA I just use the water and I washed their cars they don't need all that water you know instead of going oh they needed to flush the toilets you know about that well I'll need as much to foster thoughts and on and on and on well anyway what would have happened if LA hadn't taken the water out of the ones Valley well the answer is you could have done agriculture in that valley for about 70 to 100 years so they'd be done by now why well because of alkaline build-up alkaline built if you're in a desert atmosphere and you're when you're planting crops in the desert you've got to use four-fifths of the water for flushing the salts out and one-fifth of the water for the crop so it's very inefficient you can run five crops a year sometimes in places like Mexicali or Holtville they run five crops of carrots a year and Holtville down near the Mexican border but it's not the most efficient use of water because of the assault issue overdrafting aquifers one of the problems we have is you get out in these big valleys that you tend to have in the Basin and Range welcome to Las Vegas is what it looks like around Las Vegas and you're going out wait a minute where all these clays come from from the dry Lakes back when you got in the coming out of the Ice Age coming into the Holocene it was raining a heck of a lot more in fact Salt Lake City was under 700 feet of water it's called Lake Bonneville and over in Reno Carson City they were under hundreds of feet of something called Lake Lahontan huge inland lakes and so you had the deposition of all these fine-grained sediments and then you have these mountains being lifted up very rapidly by tectonics and so you have all these coarse gravels around them and of course the coarse gravels are what everybody wants to drill into and put their straw into suck that groundwater out baby make that land valuable and so what happens is when you suck this water out you change the effective stress on this saturated clay and the saturated clay just collapses like crazy and this is your number one geotechnical problem in the Basin and Range in Arizona it is out of control they actually have an aqueduct the Palo Verde aqueduct built in the late 70s coming from the Colorado River at Lake Havasu and they have places that aqueduct every year gets broken and then it gets broken like this a couple you know cracks a couple inch high all of a sudden that water goes into those cracks and all of a sudden the aqueducts 30 feet down in the ground gone just gone and then all this water pouring into it and they got to shut everything down and go out there and rebuild all of it it's one of the number-one engineering problems in the country because where's everybody movin to where's the population center of the United States Edgar Springs for the 2000 census where was it in the 1990 census Steelville Missouri the population center is moving toward the southwest everybody wants to live in that direction that's for all the new development is even in the state of Missouri it's all down Branson say so everybody's moving down there but the geotechnical problems they have in these places are huge they really are why do you think I live here all right subsidence due to groundwater withdrawal I'm looking at Silicon Valley right here there San Jose downtown San Jose Santa Clara Sunnyvale Aliso there Stanford Palo Alto this area has had groundwater withdrawal for agriculture starting about 1915 and by 1935 it was completely out of control they had lowered the ground water table in San Jose 330 feet just from over drafting for truck crops down in these valleys and so they had to pass a referendum create the Santa Clara Valley Water Conservation District they built dams back down here and they had they came up here with a system of of trying to conserve water and not pumping so much water and when I was in college of course this was a great eco disaster and this water wasn't going to come back for thousands of years well came back up in 1983 and that surprised everybody that in just a basically a 45 year period they could get the groundwater back up but here's what happened you're actually showing you the groundwater levels they started pumping nineteen fifteen water's going down down down down here's where they had the referendum creating the district here's what downtown San Jose is doing it's settling and when you start having feet of settlement your sewers don't work anymore sewers are typically laid out on very low gradients half a percent to one percent so if you start settling here you start having problems getting the sewage to go where it's supposed to go which people start noticing that one they may not notice the groundwater table going down but they do notice the sewage not running out of their house somehow that catches their attention and you can see here they had a really good program during the war of the groundwater coming back up that's because they weren't producing as much and then they started drilling and withdrawing more and more water as the industrialization occurred after World War Two and you can see here it got down to an all-time low by 1963 and you can see what happened here they had a lot of damage here so they pass more laws and said okay can't withdraw any more water we got to get this thing get it to recover and it did recover completely by nineteen mid 1980s but you can see what happened to the ground service the ground service is permanently settled over here and the amount of settlement you had was on the order of ten feet that's a lot of settlement for a pipe conveyance system alright we'll stop there and have a little break for five minutes and then come back and pick this up I actually have a book about that you know a memoir on that if you want to read it that I did for the Grand Canyon River guides couple years ago because I was the only guy on the river in the 83 flood that ran it at 93 thousand CFS I didn't get any I didn't get as the only trip I ever won I didn't get any blisters all I got was an upset stomach 18 feet per second yeah on the on the rapids going back going about double that use its nine in the rapids I was going about 18 I have pictures of it on my websites big washout yeah all right well let's pick it back up here this actually shows you the subsidence in the San Joaquin Valley the San Joaquin Valley has a lot of debris flow fans because of the San Andreas Fault Bend right along here and that's lifted up this Coast Range very rapidly the Sierra Nevadas have lifted up fairly rapidly there's a big active East Sierra fault zone going down the back of that and so this Basin is filled up very very rapidly with a lot of material that is subject to hydro compression and to compression through the withdrawal of groundwater two different mechanisms so here is actually Joe pullin kind of the father of a groundwater geology in California he work for the USGS Water Resources Division his whole career he's actually standing next to a sign right here and he's showing you that between 1925 and 1975 the ground settled from here all the way down to there 1977 so 30 feet of settlement over that 50-year period that's a pretty dramatic rate of settlement that's what you have going on in other places like Kazakhstan it's even worse around the Caspian Sea due to withdrawal ground saltwater intrusion is a fairly perverse problem along coastal lowlands where you have overdrafting the fresh groundwater and that's because the salt water comes in underneath the groundwater because salt water is more dense so the fresh groundwater floats on the more dense salt water salt water has a density of 1.0 3 and the fresh groundwater density of 1 and of course this gets more brackish as you go in so you start out here at 1.031 Plateau to 1.01 that kind of a thing and so this happened in Downey California back in 1957 not far from where I grew up lost East Los Angeles County and they had a well here that was about a 12 or 16 inch diameter well and their course there they're pulling on it like 8,000 gallons a day or something higher than that there was a very very high yield well and all of a sudden people started getting brackish water coming in to their to their treatment plant and it started attacking the galvanized pipes as you can imagine fairly rapidly and so they had to come up with a system of coming in out here and putting in injection wells which are all along the the Santa Ana River plane and the San Gabriel River plane and the LA River plane three major rivers that come out and they have to inject ten thousand GPM ten thousand gallon per minute injection wells to try and keep this from going too far inland now downing I should tell you down he's like you know 13 14 miles inland it's not it's not quite by the coast by a stretch it's quite a ways inland so that was a big surprise to everybody this is the Oxnard plain down near Ventura and they had the similar problem here only here the groundwater withdrawal was all for agriculture on the lower Santa Clara River and so they had the same problem happened there the late 50s they started getting brackish water intrusion again many miles inland was seven and a half miles inland and so they had to start managing it responsibly Israel had the same problem this actually shows Israel's coastal aquifer shows that the coastal aquifer was above sea level and 1959 they overdrafted it and just you know 14 years later 1973 that had changed dramatically and they had a saltwater intrusion problem now the Israelis are very clever they love to use a lot of technology and they actually were the first to look at trying to actually build a this is looking along the coast here and these are transverse to that section they actually looked at building a cut-off wall a slurry trench cutoff wall along this whole coastline and of course it got into billions of dollars pretty quickly you can't do a slurry cutoff wall over miles and miles and miles like this you know hundreds of miles just doesn't doesn't work and of course plus the the depths would be very very considerable so they have to do different things there to actually control it and I see here I lost my hang on here let's do Oh what's going on here I lost my words polluted it's red yeah okay brackish water I'll use blue for that so the brackish water is what they're actually putting in to stem it and that's actually been working pretty well for them they were the first people first country ever do that and a lot of other countries have now followed suit and they're doing the same thing using brackish water because much cheaper to try and stem the the tide of the intrusion alright so what we're talking about there is they'll come in right you know they have a problem here with the salt water coming in they have a dispersion zone here you got to stay out of especially you've got steel casing so they're coming in here after the it advances on them this is what how they got into trouble so here's what they're withdrawing so they're coming in out here and injecting brackish water in that zone to try and move this thing back down so it stays away from their withdrawal points alright in the Ozarks we have a problem with sewage because we have extremely permeable aquifers they're like interstate highways like cars so you get water gets in their food travels 50 miles in just a couple days five days is untypical at all and sewage often becomes purified as it passes a few dozen meters of an aquifer composed a fine grain material but you get no purification that was just traveling along an underground river as knocking you're not going to get anything happening that's really good and so one of the problems we have is you know what kind of laws do you set up at Jeff City for dealing with septic tanks and how far septic tanks should be from your well and so we have a law and most states have a law that they have to be at least 75 feet apart well some lawyer who didn't have a geology degree came up with at 175 feet that has to do with the size of a lot that's what that has to do with having to do with anything with science so would you want to have your well 75 feet down gradient from your neighbor's septic tank I wouldn't want to do that I didn't like a good idea to me so septic tank and the contamination you have in this kind of an area this is going to be a problem that's very spotty and it just depends on the geology and on how well these things are managed things that get put in the ground tend to get forgotten and not managed very well that's been my experience they tend not to get managed at all and also you see you don't have a straight line flow but you know by the time you discover you got a problem here mitigating it is going to be very very problematic you're going to have to drill a new well you're going to have to seal off this whole zone and withdraw from way down here somewhere to get around that problem so we haven't really visited upon this one too much except at commercial sites down around Springfield and where we've had some problems with things leaking where they put in I spend enough money to try and figure out what's going on what the problem you have is this one right here this is more this is the kind of get in class homogeneous isotropic doesn't exist in the real world it's good for midterm exams here's what you actually have in the real world you got layered systems some of the layers are parallel to the ground surface some of the layers are controlled by structural geology sometimes you have faults in here anyway you can get down here on something like this and travel very very quickly and get down here to this point more quickly than you'd like to have happen well groundwater can also be contaminated by both fertilizers and pesticides this is a major major problem for st. Louis the water we withdraw for the treatment plan at Chain of Rocks comes out of the Mississippi River where's the water the Mississippi River come from from the farm fields of Nebraska and Iowa and Illinois and they are going to be putting all sorts of fertilizers into that those fields and how the concentrations of those fertilizers change every day every year pending on how much it's raining remember I told you there's no reproducibility to that well when you design chain of rock's treatment plant you design a water treatment plant like you design a crude oil cracking plant refinery you design it for a specific chemistry one of the things we're trying to take out one of the things we don't take out is gasoline so when somebody spills gasoline in the only thing you can do is flush it to the ocean yeah that's frightening yeah you can't treat it you can't take the gasoline out of it no nobody's figured out a way of doing that 1 ppm gasoline you're not going to want to have your kids drinking it in there with their meals you're going to flush it out to the ocean ouch and what about the guys in the ocean well they don't have attorneys so that's good sucks gets sent to them that's where it goes ok so this whole issue of can we come up with better fertilizers that have more natural components yeah that's going to be in our in our interest long term we have a big problem right now in st. Louis with the water treatment plant in fact they're looking at replacing it completely with the system of deep wells near the confluence Black & Veatch has been designing that and they're going to take that water out from 100 feet plus down to get away from the modern-day pollutant effects we also have things like landfills and landfills are always a wild card because they produce leachates and the leachates like a coffee it's gotten you know it doesn't look good it doesn't smell good and and you're not going to want to get it in your groundwater system and so we're spending a lot of money chasing that one and that's a big issue for people like Fred Weber who want to take the old limestone mines when they're done getting limestone out of it they want to turn it into a landfill and put trash in it make money on it well is that a good idea in a karst environment are our Geological Survey has not permitted a new landfill in the Ozarks in decades because we live on karst and they just can't they can't see how you can make cursed work to fight against pollution so every time I go up to Jefferson City and I have a glad-handing session with the politicians and as soon as I say the word geological engineer BAM they hit me with this you know why did you in order total geological survey people and tell them could Center all of our trash to Illinois and the Kansas well that's what we do right now we send our trash from st. Louis metro area to Illinois and Illinois gets you know millions of dollars a year of our money to take our trash same thing with Kansas for Kansas City and we can't you know so the political pressure you can see it rising right now the political pressures been put on the Geological Survey over here to start permitting landfills inside the state of Missouri so is trash a political football you bet and the Mafia is all over the trash industry they love it they started that in Italy very wisely because what are the two things you're going to produce sewage and trash you know you don't have to get people addicted to those like heroin another thing is a lot easier you know the producer that they're living they're breathing they're producing those things so the guy who treats that stuff and has a cartel on it you know I think Italy how many Italy how many Italy has a record number of strikes for a trash collection but every year that six strikes a year or something it's it's phenomenal yeah because they the the mafia owns it and they just want to keep upping the price on it and what's your what are you going to do they don't pick up the trash you leave it in bags and it accumulates you know it's big problem all right well withdrawals and so where do you want to put the well I mean obviously you don't want to have the well too close to where the septic system is going in or you could have a problem you'd like to be up gradient if you have a septic system down gradient and what we learn in school when I went to school we took you know is that in the early days of environmental engineering we called it sanitary engineering and those days didn't sound nearly as good sound like you know sanitary pads so nobody want to major in that so we changed the name to environmental engineering and everybody flocked to it and and you know what we were taught was the solution the pollution is dilution so the big thing is you know if you can dilute this enough it's not going to be a problem well that doesn't fly anymore the solution to pollution is to do some sort of engineering solution not just you know say you know dilute it and so these kind of things are really going to come home to roost on us where you have geologic situations where the gradients go in the wrong way for the high-yield well like you see right here this is the kind of situation you're going to hear about it this kind of situation you're never going to hear about it because not creating a problem yet this might be a problem if that keeps going for you know couple centuries who knows but you're also going to have a lot of filtering natural filtering that occurs over a few centuries all right geologic work of groundwater from up from a human life perspective we don't think about this stuff very much but ground water dissolves rock because groundwater is mildly acidic there's natural groundwater without you know all the Coal Fired plants burning its net mildly acidic it has weak carbonic acid that forms when the rain water dissolves carbon dioxide in the air and you have decaying plant matter which adds to that so that carbonic acid reacts with the calcite and the limestone to get calcium bicarbonate which is this stuff right here this little this is made out of calcium these straws are made out of calcium bicarbonate so that that's a big issue render the one great benefit we have in living in hillbilly land is we shouldn't get osteoporosis around here we have very of the nation's lowest incidence of that we have a lot of other things where the highest in you know but we do not have problems with the bones breaking as much around here it's probably from eating all the venison to weak carbonic acid is going to dissolve carbonate rocks so we have a million square miles of carbonate rocks under us in the Midwestern United States and so you have water going through this stuff it's going to go down here and you're going to have these cavernous zones that form in the zone of aeration now this would all be simple if the zone of aeration always remain constant but it doesn't because we don't have as much water today as we had 11,000 years ago so 90% of the time over the last 1.6 million years we had a lot more water running through the system we had a steeper gradient because sea level was 360 feet lower than it is today and so what we have right now is a very temporal system where we have lower gradient feeding out to the ocean the rising base level and we don't have as much water flushing through the system so keep that in mind for where we're going here so what are some of the things we find in these caverns we can actually date these things these speleothems now we call these speleothems that's the stalactites and stalagmites and the stalactites hang from the ceiling the stalagmites build up from the floor we can actually date those and they've actually done this in the Grand Canyon region to actually figure out how the Grand Canyon was formed it was formed from west to east as a headward eroding channel system that got through to Lake Biddy Ho Chi and and stole the Little Colorado system and then the San Juan system and so on and so forth they have a pretty good picture of it now here's the speleothems at Carlsbad Caverns southeastern New Mexico if you ever get a chance to go there stop and go it's really pretty effortless you walk all the way downhill it's nice and cool you can have a fried chicken dinner down at the bottom when you get there and you can take the elevator out in this one if you've got adult onset diabetes this is your vacation here's what it looks like inside Carlsbad Caverns some of the straws they don't let the public walk right now but this is taken from where the tour goes along on the concrete sidewalk and karst topography if we actually look around Missouri we actually see a lot of this in southern Missouri landscapes that have been shaped by dissolved power of groundwater have deranged drainages and all these little closed depressions filled with water and this stuff is slowly dissolving and you have a striking lack of surface drainage you don't have the dendritic drainage Network very well developed because everything's just going straight down so karst topography starts out something like this and then as you get deeper and deeper incised you see these bomb craters all over the place these are old these are sinkholes feeding down into pipes and then as it gets more and more well-developed like Southeast Asia you actually get tower karst in Canton province down in China which is spectacularly get these things are 300 meters high tower karst and you actually have systems here that are multiple systems where you have strata in here like shale lenses that create multiple systems and you can actually see the evidence of groundwater being higher before and lower now or vice versa and that's the key thing for us as engineers is to appreciate the geomorphic evolution the geologic history this is really really key you have to understand you know where am i and this whole thing it might put my tunnel down here or am i putting my tunnel up there makes a big difference down here you can pump till hell freezes over and never get all the water out of the dam tunnel okay so you better bring your scuba gear with you up here you can do all kinds of things completely different job just depending where you are now now there's tower cars by the way what it looks like spectacular the thing we're all afraid of especially we live down here near near Ozark down is this you know the sinkhole and a lot of sinkholes tend to be centered on some sort of development because sometimes these people are pumping water down into the ground they're leach field or septic system and they're artificially recharging and causing a concentration of point source of moisture which is exacerbating the formation of this sinkhole the sinkhole would not have occurred in modern time absent that unnatural concentration of water and this is a big problem along highways in Tennessee for years and years Tennessee d-o-t didn't want to pave their their shoulders because they would cost them you know forty five dollars lineal foot to put in pavement and they kept getting sinkholes along the river along the all the way along the highways finally they had to just bite the bullet and realize well if we don't pave it we're not going to have any control on where these things occur and they're going to start impacting our highways and costing us a lot of money now they did that originally saying well when we get these sinkholes then we get federal money it's seventy five percent matching money to fix the problem but the problem is you don't get any money for the interruption of traffic because it takes some time between here and when you get the problem fixed and in the meantime you're not running Kenworths and Peterbilts up and down the highway so that's a big economic impact and they've had more interstate highway closures with sinkholes and rock slides in Tennessee going over into North Carolina than California has ever had so you think of California's being the big place with the geo hazards now Tennessee's got the place as the highways getting closed by rock slides all the time i xl between Asheville and Knoxville gets closed all the time here's what one looks like this is the Exeter sink over in Barry County a couple years ago March 2005 Jim Van Dyke the state hydrogeologist took this picture you can see the people for scale this is just out in the middle of a pasture it's not along a present-day channel because these are paleo cars features these are developed off of things that were actually formed back in Mississippian time and so these are paleo cars and somehow this is collapsed and you have one heck of a big feature there you can even see the stratigraphy along here very well developed policies a horizon B horizon Wow this has been here this fill has been here a long time now you go around here and it's nothing but fill that just looks like artificial fill all the way around so that's that's been there a long long time here's an old sinkhole old sinkholes look like old shell holes looks like somebody came in here and dropped a huge bomb and basically it's just a closed depression and that would be a good spot to avoid you don't want to build your house on that unless it's your mother-in-law and you don't get along with her now what do they also use these for in the Ozarks they use them sinkhole dump because here you can dump the stuff over and it sinks away and everybody said you know they come in here from other places like California and say well how they leave all their trash out like this you know is this you know and the reason is they charge you with the dump by the pound so you take an old caterpillar Tractor something to the dump you're going to pay ten thousand dollars to get rid of it now in California they got laws on that kind of thing though they'll come get you put you in prison you know but back here you just find a sink hole like this and you drop it in there cover it up with some dirt and what the heck that's going to give an archaeologist something to find someday you're actually you know here's a societal benefit right yeah all right now there's all kind karst in the world of karst and caving there's all kinds of technical term just like medicine so you have all these different things underground this is kuala lumper and this is a you know all of Southeast Asia is karst heavily cars defied and so you have these big haystack cliffs and underground you know huh mcc's and we call this a cliff of course that's an overhang and then you have pinnacles floaters floaters are real common problem when you're drilling you think you're in bedrock you're not we call this cutters and pinnacles and you have cavities and all sorts of things this is a collapsed cavity which is not uncommon at all and then sinkhole finally like this and you tend to get a sinkhole above a pipe leading down to some place where there's water moving so we have here is finds our piping down here and then they're getting dispersed in here this is the conveyor belt so you're only going to get a sinkhole if you're over something where you have an interstate highway of water moving through it so this becomes your goal is to find these guys and be careful what to do in terms of blocking this seepage path because the fines are piping down here over here it's not not so much a problem well if we look at systems this is Mammoth Cave Kentucky which is probably the most studied car system in the United States and we're looking at here is yeah got a little I got some typos here hang on comparison between where's the delete key Wow there it is huh that's not working oh well hmm I'll have to fix it later I don't care for how to fix it on here never hit the Delete key and not have it do deletes before I see shift delete yeah there we go all right this is a comparison between the measured heads and the simulated heads and the homogeneous porous medium channel network and so if you looked at a groundwater homogeneous isotropic thing like you get from visual mod flow this is the kind of model you would have and this is the kind of model they actually have under there and what this shows you is you have an underground developed system because of all these pipes it's far below the theoretical groundwater surface so when you get into a large karst Network you have these interstate flow highways look at all these coming off right here this is a very steep face right here just slidin down here so you have these pipes that have very very high flows concentrate it's Underground flowing system that does not reflect itself in the surface topography and that's why karst is so dangerous you have to understand this you really you can't do this from Vienna a theoretical egghead who who plays with computer programs you need to be one of those muddy spelunker club type folk that get out and get in these things to realize how hideously three-dimensional and complicated they really are there's a channel network that's been developed over eons of time well here's where this comes in with the engineering plenitude noses this is a more work again in in Mammoth Cave area if you go back and look at Mammoth Cave and you say ok when sea level was 350 feet lower here's the drainage system that eventually is leading out to the Gulf of Mexico and so I have karst system developed above that line this is car stuff I'd up here this is not cars defied because this is never been unsaturated never been in the aerated zone but now sea levels come up 362 feet over the last 11 thousand years so I have channel fill I change the base level now I've heightened the water table across here and I've got flooded karst highways beneath the water table over here and that's fine as long as you don't get in there and try to do things like dig tunnels you go over here and do a dam project try to dig a tunnel through there and hit one of these underground interstate flow highways you're going to know about it in no time at all oh I've gone past my time so we're going to stop there today and pick this thing up I'm Way past my time I guess is that right ok they haven't changed the clock that's what it is sorry all right I wondered what happened there all right they did it change the clock all right so this this little thing I just showed you this is the critical thing we deal with like on Wolf Creek Dam over here on the Cumberland River the reason we're having the problems at Wolf Creek Dam is this issue right here we have incredible karst development at great depth below the water table and back when they built those projects they never considered the karst being extensive hundreds of feet below the modern water table that caught everybody by surprise and that was discovered on Kentucky dam in 1940 ok so here's what I'm talking about if I go in and I go to put a water supply tunnel up here and I'm above this valley fill and this new water table line I'll be ok but if I have to put it my tunnel down here and I happen to run into one of these there's no draining this thing you get these pipes that are just incredible there's no head loss water gets in here and just push you're going to drain the entire state so when you get in here you got to be real careful to seal off your tunnel from one of these highways or dig it way back over here well you're not going to run into as much of this stuff and that's that's what I would do I wouldn't put the tunnel over here I wouldn't even chance it I just move it back over here where I know I have a very little chance of poking through one of these things so doing tunnels in karst is a real dice rule all right sinkholes in Missouri do we have sinkholes in Missouri boy do we again down here is the Ozarks and the Ozarks are not glaciated so lots and lots of shallow karst north of the Missouri River right here you're glaciated so you don't see nearly as much there's a little bit of OB up in your Hannibal as you come down and the st. Louis limestone down here it's Jefferson County but mostly it's in the Ozarks where you have the problem now that's what a losing stream looks like next to us over here in Laclede County over near Fort wood it looks like a dirt road and it going that's a creek how about going to fish for trout and that Creek well you're not going to fish for trout in that crypt ain't no trout in there but it's great for driving your 4x4 in there at night see see right where you got to go it's a dry Channel it's a losing stream it loses its water and what you have is you have alluvium over a fractured bedrock and this is so porous down here it's got unlimited porosity so once this water this water will flow down here if you have a high event so it rains like crazy for an hour and a half or more you overwhelm the permit the permeability of the bed so water flows on it within a couple of days the water is gone it seeps through the alluvium and goes down into the fractures these old big open fractures those are the permeability highways so that's a gaining stream setting would be like that where you have water in here and you actually are feeding water into the channel we don't have that kind of scenario in the Ozarks we have a losing stream setting and we have countless voids down here in the bedrock for the water to seep into and the water tables down there at some greater depth now notice the water table moves around locally depending on these major fractures so it's going to be higher between them and lower when you're right within them because you don't need pressure head to push water through open fractures so here's typical losing streams here's one where you have a channel that gets flow fairly regularly but doesn't maintain flow probably ever more than seven days and then here where you don't get much flow the bed of the channel completely grows in with vegetation so here I can get away with doing an Arizona dip with my roadway here I actually have to have some sort of structure there because it has discharge in it more often although it doesn't sustain well here we are an i-44 near Springfield Missouri you'll see they pre split a line for a new highway alignment there this is the highway between I 44 and 65 heading down to Branson and they got these caverns that they ran into and have to deal with Nats actually come back in here and fill this with gabions or with rock or with something because otherwise you get a collapse potential in it this is actually some work by Professor Neil Anderson and Derek Appel and mining with engineering they went out for MoDOT and looked at these pinnacle and cutter system down there along u.s. 65 and what you see is it's very very regular and linear it's controlled by jointing so this is a joint cluster running right along here going this way and then you have orthogonal joining come in this direction and so you tend to get these boxes where all these stuff has been dissolved away and is gone so the pinnacles and the cutters are between the orthogonal joint system this is the kind of thing we get today using very very inexpensive soil resistivity arrays and then stitching them together on a computer and for you know for just a couple thousand dollars you get a three-dimensional view of a very complex sleet eroded surface which guess what the only view that counts here is the three-dimensional view if I cut two dimensional views anywhere here you would not come away with the same picture it would really light ooh you especially if I put it right through here or I ran a section right down here so where do you want to put the highway wave up at the highway right down there but the I hear something I don't know but you can see it's highly dissected and you'd like to know that when you're going to put any kind of high value structure in here like a bridge foundation of building foundation anything like that all right here's inside Fischer cave now one of the neat things about being a spelunker is the cave fills in Missouri we have cave fills in Missouri where this surface is soft and has tracks that are soft unfossilized look like they were put there yesterday that are a hundred thousand years old that's one of the only places in the world you're going to find that why because this is the most stable part of the Western Hemisphere kraton right here the Ozark nothing exciting ever happens here except you know Walmart parking lot on Saturday night this is very very stable and these sediments have not lithified and so it's amazing what you can find in here's courthouse cave on the current river and there's what it looks like as you go in side of it and as you get inside of it what you find is the mud ripples inside that it tests a much higher discharge in the recent geologic past so this thing had a lot of water coming through it this was an interstate highway of water coming through here flowing at the viewer up to about probably 7 to 11 thousand years ago here's jamup cave it's another one on Jax for if you don't think it's big that's a person for scale right there so this is a structurally controlled feature that's some cheering along a joint system there's people for scale but to speed lunker's and there's some websites you can learn more about caves if you haven't gone out with any of the speed lunker's get at least one field trip in go buy some clothes that you don't want to keep because it'll ruin your clothes but it's really worth going to get the experience of just seeing underground now what I'm going to go hit this next time and I'm going to start you on a different lecture which is about my work in New Orleans all right yeah I don't know if that means let's say I get it to open all right now this is a a party lecture I did for the Geological Society of America meeting a couple years ago this is one where they invite the media and all the students and stuff to it and it touches on what are some of the mechanisms that drive land subsidence and what we can do as a nation about it I start out with this whole thing and I call it I use the word survivability the politically correct word today is resilience resilience means if you're going to build something you should build it so that it's not going to have a catastrophic failure this is a levee right here and this levee is being over topped by a Katrina and after Katrina was done the levee was still there they did not fail catastrophic Lee it had some erosion but it did not fail catastrophic because it had some clay in it clay is very important for the survivability of a levee both from seepage induced erosion as well as runoff induced erosion and we learned a lot about runoff induced erosion and seepage and rosin in Katrina I even learned some things and we used to think that this was the critical place but turns out it's not the the erosion actually starts right about here starts about two-thirds of the way down the slope and when it breaks through the rooted zone you're gone if you don't have enough clay in the embankment here's the kind of embankments they had down there they're made out of oyster shells oyster shells do not have any cohesion they don't have any binder if you don't add the binder you need to add you're going to use moisture shells which are great for bearing capacity that's the only kind of gravel they have in Louisiana you don't have any rock gravel so they use oyster shells if you're using straw shells you're going to have to stitch them together with cement you have to add some cement to the mix or it's just going to be gone when you run high velocity water over it so when you flew over these levees made out of silt and made out of oyster shells the levee were just gone because these were organic rich materials and they just disappeared when they were over topped by the high water of the hurricane and other areas they put in steel sheet pile cutoff walls along these and it still just took all the erode Abul material that comprised the levee and just washed it away that's because that material is silt and organic silts and oozes now you also you can cover these materials that are wrote a bowl you can cover them with less eroding clay Ecover but you got to watch the transition zones where you do that because when you again I mean you get when you bite through the rooted zone and through the clay layer then you get into the stuff that's much more irritable the low cohesion fill in this particular area the clay cost $30 or $80 a cubic yard to bring it in from Mississippi and use a bottom dump barge to get it in there well if we look at the Gulf at that time of a Katrina that the Gulf was losing an average of 35 square miles of land a year this is what it actually looks like when you look on a kid's geography map or National Geographic it shows all this as being solid color all this little dispersed white stuff is all the lam that's been lost since 1935 and it's an average of about 35 square miles of land a year that dips under the ocean and in the Delta and it's 44 square miles a year of wetlands that are being lost out here and the wetlands help to mollify the energy effects of the storm surges oh I guess I can't I have to have that thing going huh technical help just going to keep just going to work okay all right so in flying over the Delta after the storm we noticed there were huge tracts of land that were now water that used to be land and when you go out here and investigate it turned out this was not land as you and I would think of terra firma it's floating Marsh but the marsh mat is so thick five feet thick you could drive a drilling rig out there a hundred thousand pound drilling rig and drill a hole through it but it's a floating Marsh so a lot of this got whipped up in like a Mixmaster into the atmosphere and as an engineer I got to ask myself the question can i construct sustainable levees on these kinds of materials the answer's no I can put levees here right next to the river where I have some soil type material but once I get back here into the slack water and I got floating Marsh I'm not going to build much on the floating Marsh except houseboats I can float aircraft carriers in it okay during Hurricane Katrina this is going toward the Gulf this is going towards Lake Borgne New Orleans is right up here out of the picture above my finger in that one six hour period the light blue area here is the land loss it's a hundred and fifteen square miles of land lost in that one day now the average rate was 35 per year so in one day they lost a hundred and fifteen square miles so if you factor that in now the new average is probably up around forty something per year so it was a big event here's the big problem Central Louisiana is subsiding at an average rate of about seven millimeters per year right now and sea level is coming up at about three millimeters a year if we look back at the last hundred years and the N and beyond so over the next hundred years we can expect a net differential of about one meter now if that happens a hundred years from now here's what the coastline is going to be way up here and where's New Orleans well there's New Orleans the orange is going to be out here on the distal end of the Mississippi River that's not underneath water the modern-day Delta and Plaquemines Parish is all going to be underwater and see Houma is going to be sitting out there like an offshore oil derrick farm it's got dikes around it and it's going to have this little lifeline coming back and here's Baton Rouge way back here and Baton Rouge right now is 170 miles from the ocean so 1 meter 39 point 4 inches makes that much difference yeah go down there look around everything be flat down there you could see Dolly Parton from 20 miles away down there it's so flat that's politically incorrect I know anyway very flat alright so what are the mechanisms driving the ground settlement it's not simple and what I found out when I went down there and interviewed people I got pretty frustrated because everybody wanted to blame somebody and they all want to blame the Corps of Engineers and they wanted to blame shale oil companies all the oil companies fault because well companies got or wealthy they got deep pockets and in reality it's no one mechanism that's driving all of it's a whole bunch of mechanisms a dozen different mechanisms and that's why I wanted to expose you to it in this lecture so there's many different causes and I'm going to briefly summarize those in these slides there is where the geologist always starts if I'm going to communicate geology to an engineering audience the way I do it is with block diagrams and usually I color them I haven't got around to coloring this one yet but there is the diagram very similar to the one karl terzaghi used when he was down here doing the early pioneering work on subaqueous submarine landslides there's 10 times as many subaqueous landslides each day on the earth as there are in the continents under the water that's where most of the big landslides occur big landslides how bigger these landslides Dave are they're 15 miles long they're big really big and these landslides interdict oil company pipelines all the time out here every year oil companies are losing their trunk lines to their offshore platforms out here by underwater landslides especially when you get out here on the continental slope where things are much steeper and you have died appearing masses rising salt domes you have all sorts of normal faulting going on here's more of the rising salt domes so this lands lifting up this land is moving out and dropping down underneath the water this is sea level here so all this action is going on beneath sea level that affects the coastal zone up here where CNN and Fox can film things they can't film stuff out here they don't go underwater yet and so you got a lot of stuff going on and it's very very exceedingly complicated geologically in three-dimensions all right so you have fluid extraction of oil gas and water one guy with the USGS has blamed oil and gas extraction for everything and I think that's way overly simplified because you see a lot of these same features in areas where they're not extracting oil and gas so that's not the only thing going on it's just very obvious to a lot of people like you you can't explain the Baton Rouge fault zone with oil and gas extraction if we go to the oil industry and we look at their geologic cross-sections through the Delta it looks like this and it's wild tectonic Li what are all these things these are huge false they're huge gravity falls well how big are they Dave well this is the Cretaceous down here at 30,000 feet 30,000 feet six miles down that's the Cretaceous 63 million years ago this is all then deposited six miles of sediment that's been deposited in the last 60 million years and it's just splintered by active faults well why don't we hear about earthquakes down there we only hear about California you don't hear about earthquakes down here because this stuff is so soft it just deforms plastically you don't get earthquakes out of it it's not brittle enough to give you a big shaken earthquake it's just like fat man you know slobbering on the couch on Saturday night after drinking too much beer it just kind of just kind of moves you'll get earthquakes they'll get stick-slip you get slob moving like the blob that's what you get so these are list trick normal faults and they cut everything and they're very important to the oil industry because this is where you get your structural traps so they've mapped these things all over the place how many faults do they have more than you can kill that's how many a lot a lot of faults if we look at an ant Astral on bail this is actually report for the Corps of Engineers by Professor woody gagliano back in the night in the mountain 1994 you have belts of these fault zones as you go inland here's New Orleans up here here's the Baton Rouge fault zone very active zone way back here behind where the oil and gas extraction is occurring along coast area so this is active even absent oil and gas withdrawals back here very active and you can really see these on the aerial photographs and what you see is the back of these blocks are dropping so you get lakes along these scarps and the water gets deeper every decade along that's how they map these things because the material is so soft you don't get a fault scarp what you get is deep water and the water gets deeper every year and that's how gag me on O mapped all these scarps running across the Delta now this is Roger Sasuke's structural geologic map of the region he's with the Corps of Engineers in Eric and the engineering and design Research Center at Vicksburg and these dots are salt domes major mapable salt domes that have been documented by the oil industry and then these little straight things are the active faults these growth faults that perturb the entire Mississippi chaff Alaia Delta system and then these are folds up and and again salt basins and folds and features so there's a lot of stuff going on down there it's a very active tectonic Lee you also have drainage of lowlands and back swamps for agriculture so you start out with an area here that's just you know maybe a meter to above mean sea level you have a lot of PD organic soils in these former marsh and swamp areas you come in here and drain these and pump water out and then you farm it you're now below sea level most of Midtown and lower and New Orleans is underneath a below sea level like this and it collapses and sinks because of the oxidation of the piece if you bring the water table down three feet that three feet will compress to about three inches that's how compressible it is 90% compression because it's just organic material so when you map the compressible PD soils this was done back in 1962 by Gould and Morgan you can actually see channels like Bayou been the new channel right here and when you put levees across that your levees going to settle a lot right here as compared to over here or over here because you have a big wedge or channel of Pete's along this old drainage and here now when you go out in New Orleans and you just look around you don't have to be a rocket scientist you don't have to be a student of Phelps County Community College you can go along here and see here's a street and there's a manhole and the manholes sticking up about a foot higher than the rest of the street huh what's going on there and then you go over here to the house right behind and as you look along the house the house is on wood piles and it's sitting up about 1618 inches above the rest of the yard now what you find out is this area has settled 10 to 16 inches since it was developed in 1956 and these are on 31 foot deep wood piles and they took the water table down maybe a meter not much but they've got plenty of settlement and that upper meter to more pictures looking underneath the residents everywhere you look you can see the ground has settled down significantly and then here's these wood piles just the houses are sitting on and you keep coming back in here trying to fill this rathole in with sand and plant things in here so they have tremendous settlement just due to oxidation of the piece and groundwater withdrawal well when you start looking at groundwater levels and you look at subsidence what you see going back to 1920 is a very clear and continuous system of subsidence tracking with groundwater withdrawal because they develop it this is in town of Kenner out near the airport Jefferson Parish and again you can see in here settlement having to do with periods of tremendous groundwater withdrawal this is right in here is when they put in a new series of pumps right here after the war and then again more and so they've had tremendous amounts of settlement 70 80 inches of settlement which is a over 8 feet approaching 10 feet in some areas so that's groundwater withdrawal for industrial use and urban development let's can't sue the oil companies on that one if you look at a highly exaggerated cross-section of New Orleans this is what it looks like Lake Pontchartrain is sea level down here and brackish water and the Mississippi River is about 5 feet above sea level at its low flow line it can actually get up to all the way up to 29 24 feet above sea level before you would crest over the levee and you can see you have this sombrero shape in the middle this is the Metairie Gentilly Ridge this is an old distributary of the Mississippi River from about 2,000 years ago that goes through the middle Midtown area and it actually comes up to about six and a half feet above sea level so if you're on Metairie Ridge you don't get flooded out if you're in Midtown you do get flooded out and if you're down here you're below mean sea level and so when you have a catastrophic failure of a levee down in this zone you have a large portion of the town that then is underwater now in Hurricane Katrina this is where the breaks occurred down here right in this zone not far from this protective levee in the drainage canals so the water came in at the lowest possible elevation right here and leaked in very very slowly now if you were living down here you would have had to walk about this fast to get out of there and not drown you wouldn't had to walk very fast got a done very very slow just like a Missouri boy goes after eating too much fried food you could have gotten out of there if you could walk what you don't want to have happen is a catastrophic break up here if this levee were ever break it hasn't broken since 1859 before the civil war that breaks up here it's going to come down here and kill everybody because these guys got no way of getting out because of the head differential it's Darcy's law that water is going to get there really really fast so the best place that could break the sweetest place to get a break is right with broke in nineteen in 2005 down here at the lowest possible elevation but if it was ever to break up here it'd be much more catastrophic in terms of loss of property in life because of the energy head now if we go back and we look at this place they started digging drainage canals in the 1790s and they were trying to do is to get drainage away from the high ground the highest ground is right along the river so they started they started digging these drainage canals and these were all finished by the mid 1870s and this topographic map was made by the City Engineer LW brown in 1895 so if we take this map and compare it to today we can actually get a picture like this and show that the net subsidence in across New Orleans was something between two and ten feet over a hundred years and these areas down here that are below sea level are the areas that have sunk the most the interesting aberration is the brown area which hasn't sunk the brown area is a fill put in by the city between 1928 1934 and it was put on a non peat foundation out in Lake Pontchartrain that used to be the shoreline of Lake Pontchartrain which was coming inland there a little bit every year they put this huge hydraulic fill out here sand fill on a silt basement on the pond the lakes very very shallow and this hasn't settled because they don't have peeps under it this is where all the Pete's are and that's the area that's settled eight to ten feet and that's where the drainage canals had the brakes because they had settled so much now you also have structural surcharging if you come in here and you put heavy structures on like the the Superdome the 1983 Superdome was completed that was the deepest pile supported structure in the United States had a hundred and forty foot deep piles going down precast concrete piles going down into the Pleistocene gravels the good stuff really good stuff and they design it for a category-5 wind storm 150 mile an hour winds so how did it get all the big holes in it well I got all the big holes in it because of all the Cypress and gum trees blowing in the 150 mile an hour wind they forgot about those if you're going to design for 100-year flood or a hundred year storm the one thing you got to remember is you don't just design for the water or the air you design for what's in it that's what's going to get you and this thing looked like it had been hit by a bunch of Marine Corps f-18s with mark 72 slick bombs just huge holes blasted in it that's what the trees hit it and knock the holes in it so one of the mechanisms of ground settlement in coastal Louisiana you have the elastic deformation of the Delta from just load load deformation which we that's where they came up with a thing isostasy that's where it came from they discovered that the 1930s tectonic compaction caused by the formation of pressure ridges and folding that's also causing subsidence you have some science on the seaward side of the list Rick growth faults all those faults I showed you you have the drainage of the old swamp and marsh deposits which increases the effective stress on the underlying clays and you have the biochemical oxidation of the PD soils from drawing the water table down to different mechanisms you have the consolidation of compressible soils that are surcharge with fill and structures you have the surcharge with structural improvements like interstate highways and the building's you have reduced groundwater recharge because of all the impermeable surfaces all over the city so you have less water going into the ground and more runoff every year they were there and that's borne out by just the statistics of the drainage district the sewer and water district you have extraction of the oil gas and water causes pressure depletion which drives settlement because it increases the effective stress and you have the solution of salt domes and the seaward migration of low-density materials like salt and shale so you got all these things going on at the same time the only one you can sue is really the people pumping the water out or the oil or the gas we also have a problem with sea level rise sea level has been coming up over the last century and we didn't start seeing large amounts of fossil fuels being burned to the mid-1920s right here and it's hard to see that in the curve unless you realize that that curve may not be quite as steep without it it may come out somewhere like this but definitely in the last hundred years we've had a foot of sea level rise now I fought and fought and fought with a corps of engineers about this because they were doing they were designing all the new structures for 75 year life and they were ignoring sea level rise and I kept raising my hand saying you got a design for sea level rise and they gave me the lawyer answer I'm sure it came from the lawyer didn't come from their scientists because they're scientists aren't they are pretty sharp they're not that that dumb but they would give me the lawyer answer which was well you know the environmentalists you know some say one foot some say 2 foot some say 3 feet which there are some that say 3 feet I don't know what that's based on all is based on science but there's some that say 3 feet so you guys don't know so we're just going to ignore it I said no now the basements 1 foot because that's what we had the last hundred years and if you even believe 1% in global warming we're going to have at least 12 inches in the next hundred years and anyway I kept losing that battle until there was an article in The Washington Post and then everything changed and that was what the article was about saying hey you know why isn't corps of engineers looking at this this seems pretty rational this point that Rogers and other engineers are bringing up so sometimes you just want to stick to your guns and realize you want to go on record as saying what you know is right but don't get inflammatory about it just state it as though it's a matter of fact okay I guess I'm done we'll stop there you

Channel: S&T CAFE

Views: 14,133

Rating: 4.8723402 out of 5

Keywords: engineering, engineer, geology, geotechnics, geologic, factors, site, selection, design, engineered, structures, missouri, sandt, s&t, university, science, technology, educational

Id: dHakIrJSz-4

Length: 152min 21sec (9141 seconds)

Published: Thu Feb 17 2011