THE BARNACLE THAT ESCAPED FROM STARKVILLE MISSISSIPPI

My historic single cretaceous barnacle from the Starkville area is Arcoscalpellum withersi Collins which was collected in 1970 with Dr. E.E. Russell’s fledgling undergraduate Historical Geology class. That class also included Michael Bograd and David Dockery that went on to much greater service for the Bureau of Geology with the State of Mississippi and later with the Department of Environmental Quality. Dr. Russell gave us these instructions” What we are looking for looks like a little dugout canoe. You’re not going to find them by just walking around you have to get low to the ground maybe on your knees.” He was right. Not only are these small but the same color as the chalky outcrop. I found several but he let me keep this specimen. I didn’t know why until years later I decided to identify it. I then realized I got to keep it because the pointed tip was broken off on one end. At the same time

I discovered that this fossil was a new species when I found it. It was not named for 3 more years until Collins and Mississippi’s Fredric Mellen published their classic 1973 paper: CIRRIPEDES FROM THE UPPER CRETACEOUS  OF ALABAMA AND MISSISSIPPI, EASTERN GULF REGION, U.S.A. This paper includes the following acknowledgment: 

The writers are greatly obligated to many people for assistance in the collecting, preservation, and study of the cirripedes covered in the present work: to Professors Troy J. Laswell, Ernest E. Russell, and Donald M. Keady of the Department of Geology and Geography at Mississippi State University for assistance in collecting and encouragement of student participation, and for affording a repository for barnacle collections and literature in the Dunn-Seiler Geology Museum.

I could have lived next door to the gully where we went to fossil hunt in 1970 and never noticed these odd-looking little fossils less than 1 inch long. But we learned on that day that all fossils have a story to tell (big or small), some more than others. When this barnacle lived about 70 million years ago there were giant sea turtles and even bigger mosasaurs that swam past this little bottom-dwelling guy every day and also never noticed him. But because he somehow got broken maybe by a wandering cow, he wound up with an amazing history and his own blog page.

DRAINAGE FOR YAZOO CLAY

This blog is about residential structures built with slab foundations in central Mississippi but it could also be used for residences with crawl spaces in this area. In this area lies one of the most active expansive clays in the world. It is called Yazoo clay. When this clay surface is above a depth of 10-11 feet of the surface, you should have adequate fall away from the house (positive drainage) on all sides. We often refer to this elevated surface around a residence as a berm. Typically you would need a fall of 8 or 9 inches in a 6 to 10-foot perimeter from the house with a Yazoo clay depth of 8 feet. In addition, the surface water that runs off of this berm must also be properly drained away without ponding. This is so important that it should be part of a local building code. This well-known construction fact is still violated by some home builders. Often the violation occurs on terraced lots where the lot is too small for the house. When this happens it is impossible to construct proper drainage away from the house without expensive retaining walls. These houses are often abandoned by their owners 10 to 15 years down the road when the owners are confronted with the cost of releveling plus a retaining wall and drainage that should have been part of the original construction. 

With less active clays like we find near Dallas and Austin Texas, these same rules would apply except that these less active clays must be closer to the surface than the Yazoo to create this need for good surface drainage. Surface drainage problems often go unnoticed in planting areas next to the residence that are covered with mulch. Typically depressions from erosion occur around the edge of residences that do not have gutters. Sometimes the depressions are inadvertently created when the planting is installed. To discover these areas the mulch must be removed and replaced.

There are 3 ways to improve drainage other than constructing retaining walls. There are two ways to improve surface drainage plus subsurface drainage. Retaining walls can be added to surface drainage to lower the grade and improve slope away from the residence. Surface drainage should be improved when water stands in puddles and maybe when the ground is mushy after rains in the same areas. Surface drainage might be improved by constructing drainage swales through a poorly graded yard. Otherwise, catch basins are installed with drain pipes. There is a significant improvement in quality when smooth pipe and concrete boxes are used. Higher quality systems are required when the ground is flat or there is potential for leaf or pine straw to clog the pipe.

Generally, subsurface drainage in central Mississippi should be designed by a qualified engineer. Subsurface drainage is only installed to remove groundwater. In central Mississippi, this is almost always a perched water table that is created above an impermeable layer like Yazoo clay that should be at least 6 feet deep. If your drain is not as deep as the impermeable layer the groundwater can just pass underneath the drain. Poor subsurface drainage is hard to detect without soil borings. Be very cautious if someone recommends subsurface drainage without the aid of soil borings. If water is not initially detected in the boring then they should be left open for at least 24 hours. You might detect groundwater with hand-dug holes if it has not rained in a week or so. But typically hand-dug holes will not be deep enough. Note that water standing in a hand-dug hole a day or two after a hard rain might just be surface water that has saturated the upper layer of soil and may not be a condition that justifies a subsurface drain. Also if you suspect a leaking water line, you can test the water in a boring for chlorine and sewer bacteria.

I typically recommend drainage repairs when foundation movements are moderate or severe. I also correlate drainage issues with the floor elevations. This kind of evaluation is described in explained in a blog with the title:   Investigating Slab Foundation Failures in Central Mississippi.

How to Find your Family Tree with Ancestry DNA

This blog is about the Ancestry process using DNA that you can use to expand your family tree when you have hit a brick wall or a dead end from genealogical records. It was updated on 8-12-19 on 9-29-2019  and again on 12-4-2019. If you follow this process you could discover an error in your tree or expand it past all known records and then maybe you can become the Einstein of your family genealogy. Now I am assuming you were not adopted, so you know your parents and grandparents. If you were adopted the process is different. In this case, you start with your match list under the DNA tab at the top of the main Ancestry page. This is a list of your closest cousins. This list also shows the size of their family tree. So if you were adopted you begin by looking at the trees of your closest relatives. I will discuss this process in more detail at the end of this blog otherwise, please read on.

After working on my family tree since 2016, I still had two 2nd great-parents without any known parents. Breaking out of this deadlock to me was a huge and exciting advance in the genealogy of my family. In my case, there was a popular family picked by my other Ancestry cousins as the next or the 3rd generation. But no DNA evidence or records surfaced that supported this theoretical expansion of our family. I did not realize that Ancestry was telling us in a very indirect way that our theoretical next generation as we thought was almost certainly wrong. If you have expanded your family tree in error then Ancestry DNA has a way of telling you of your error. You simply have no DNA matches with the part of your tree that is in error.

In the last few months Ancestry has made some improvements that helped, but breaking through came only with a better understanding of how Ancestry was processing my family tree. What I realized was that if I could correctly guess either one of my 3rd great grandparents then there is a very good chance that Ancestry DNA would in-time verify my guess by showing new DNA matches with other cousins related to my new theoretical great grandparents. But the trick is, that if you guess wrong you must abandon that guess if you get no DNA matches with your new theoretical great grandparents. When you guess wrong it is like removing the DNA engine from your car; in-effect Ancestry can no longer help you. This is because Ancestry is trusting your research and attempting to verify it with DNA matches. How long does this process take? I don't really know, but for me, it took about a month for DNA matches to appear once I made a correct guess. An important point is that if you get just a handful or less of DNA matches eventually more will probably appear. This may happen because of improvements in processing or by the addition of new DNA Ancestry members. This is an area where you can help Ancestry by verifying the DNA matches that are flagged "evaluate," These are DNA matches that might be wrong. There is no single tree that makes the connection or used trees have conflicts or possible errors. So here your job is to work your way down as far as you can to your cousin in your tree. This process could help Ancestry find additional DNA matches. Once you do this the "evaluate" flag will eventually go away.

Ok, let's back up a bit. First, before you go this route you need to be sure you have exhausted all your genealogical resources. This means that you have looked in detail at the last known family. This includes all the children as well as the parents. You have no duplicate people and you have a family history up to your dead-end that makes sense.

A lot of times you find one or more children who were born out of the area that the parents were known to have lived. These should be deleted. Be sure all the children were born within the childbearing age of the parents. Once you have done all these it's time to move to the process below.

Ancestry requires 3 things to do what I am talking about. You must make a family tree up to your dead-ends, then you must correctly guess your next generation of grandparents then you must also take an Ancestry DNA test and allow time for Ancestry to process your data. This process should work in most cases out to about 5 or 6 generations or maybe a bit farther. Now we must understand that there may be smaller families of our ancestors who have descendants that have not taken DNA tests. So in these cases, this process might fail. But in order for this to happen, you may need to have 2 or more back-to-back generations with only 1 or 2 children that also had children. Now one last point: how do you guess the names of your missing ancestors?

I start by using the last name only of the last known father. Then I assume he was 20 years old when he had your grandparent. Then I begin searching, changing and adding possible information. As I progress I add to the age in 4 or 5-year increments. Next, I start guessing the state where your ancestor died. Next, I start guessing the state where my ancestor was born. As I progress I make a list of possible ancestors. Start with the state where your known ancestor lived and then progress to adjacent states. When you pick a possible parent, be sure that his age is realistic.

Finally, I  think you know for sure you have discovered your true lost ancestor when you get multiple DNA matches with your new ancestor. The best way to see these is through Ancestry's new ThruLines tool. You have to enable this from the Extras tab in Ancestry (select Ancestry Lab). This tool works out to your 5th great-grandparents. I access ThruLines from the horizontal family tree. Basically, this is a list of DNA descendants of your ancestors. This tool will patch together several people's family trees to show you how you might be related. To be sure this is a DNA match you need to add this person to your tree by working down from the common ancestor. Now if you only have 1 or 2 matches with a theoretical new ancestor you still might be wrong, because it may be that you are really related to these DNA cousins through some other unknown route. Also, note that you may have dead ends in your tree and not realize it. If you built any part of your tree by borrowing other member's trees, you need to use ThruLines to verify your whole tree out to the 5th generation.

Before I conclude there are some good rules to follow when you use Ancestry. You can borrow or import families from other people's trees. But when you do this be selective. I pick the 2 best looking family trees. These are trees with a lot of records but also trees without obvious mistakes like double people. If you import double people by mistake (and you will - do this) you simply merge the 2 people together. Once you import a family, try to verify it with a census, birth, and death records available in Ancestry. Finally, it's easy to forget that you have made a guess about your tree at some point. To help you Ancestry has added TAGs that you attach to a person that indicates to you that this person is a hypothesis. Also, add a comment to the person to tell other cousins what you are doing.

IF YOU WERE ADOPTED

If you were adopted your family history is inverted. From your DNA match list, you know the name of some distant or maybe a close ancestor. So instead of having a family tree, you have some ancestor that you are related to. So you must work from this person down to you discovering all the children of these known ancestors. You are a descendant of this person and if a thorough list of descendants is made you and your parents will appear in this list. You need to carefully watch the TV show "Long Lost Family." This show is sponsored by Ancestry.com. The hosts of this show were adopted themselves and they do the detective work using DNA to help people reunite with their DNA parents. In this show, they emphasize that you need to work with all the information that you know about your parents and your adoption process. On occasion, the breakthrough comes from a long list of possible family aunts or uncles that are contacted one-by-one on the phone. But if you are lucky, one of your parents or grandparents have taken an Ancestry DNA test. So, in this case, your closest DNA match could be one of your parents. I highly recommend that you in your Ancestry profile explain that you were adopted and tell the community your closest known DNA cousins. If you would like to have assistance please contact me.


Note if you see an error in this Blog please do not hesitate to contact me.

The Natchez Revolt in the Mississippi Territory in 1781-The Last Year of the Revolutionary War

INTRODUCTION: The Mississippi Territory was under Spanish control at the time and not part of the 13 colonies. However, the Spanish joined in on the side of the colonist in 1779. Interestingly two years later a pro-American faction joined with British loyalist against the Spanish government in the Natchez District of the Mississippi Territory. The territory was controlled by Fort Rosalie that was first built by the French in 1716. Mississippi would not become a state for over 100 years, it was only 17 years away from becoming a US territory. This fort was first destroyed in a conflict with the Natchez Indians and it was rebuilt in the early 1730s and again about 1778 when it was occupied by the British. The following is a look at the Natchez Revolt of 1781 as it took place right before the final battle of the American Revolutionary War at Yorktown. For me, this revolt also created a genealogical record of my 4th great grandfather showing that he and maybe his future wife had a front-row seat of this event. At the time there were only a few hundred settlers in the Natchez District of the Mississippi Territory. The primary reference for this post is “The Natchez District and the American Revolution” by Robert V. Haynes.  This blog is my 2nd most popular was updated on 8-27-2019 and again on 11-22-2019.

THE HISTORY: On May 8, 1779, the American War of Independence (1775-1783) was given a boost when a formal declaration of war against Britain was made by King Charles III of Spain. Another declaration was made on July 8. This “authorized Spanish colonial leaders to engage in aggressive action against the British forces. Directly following this decree, Governor of Spanish Louisiana, Bernardo de Gálvez, began planning offensive actions against the British.” On September 12 they began a siege against the new British fort at Baton Rouge. The battle ended with a Spanish victory on September 21, 1779.  The conditions of British Lieutenant Colonel Alexander Dickson’s surrender included surrounding the infantry soldiers at the Fort Panmure, at Natchez, Mississippi. Fort Panmure was originally named Fort Rosalie by the French, but it was renamed when the British took control in 1763.

The Spanish occupation of Fort Panmure and the Natchez District of the Mississippi Territory was briefly interrupted by the British inspired Revolt of 1781. General Campbell at the British fort at Pensacola played a significant role in this revolt but locally there were two instigators named Philip Alston and John Turner. With a joint effort, they convinced John Blommart, a reluctant loyalist, to join in and lead the revolt. The insurgents were advised that British troops and supplies would be sent to support them and that they should recapture Fort Panmure.

With this promise of support, the British loyalist attacked Fort Panmure on April 22, 1781, with 200 men and only one cannon in their arsenal. This attack failed. However, they managed to trick the Spanish to abandon the Fort. They did this by intersecting message from a “Spanish sympathizer.” They replaced him with an imposter complete with forged papers and replaced the message so that it now read that the fort would be destroyed by an explosion of gunpowder unless the Spanish withdrew.” The rebels took control of the fort and the Natchez District on May 4, 1781. However, there was immediate descent among the victors. There was a pro-American faction that wanted to handle things differently from Captain Blommart. At stake was what to do with the Spanish prisoners and the supplies and ammunition from the fort. However, the victors soon realized that there would be no British support because Pensacola fell to the Spanish a week later on May 10. The pro-American faction wanted to divide the spoils equally and flee to the countryside and hold out until reinforcements arrived from the United States. Blommart disagreed and appointed a commissary to dispense the supplies only as needed.

Natchez was re-occupied by a combined force of French, Indian, and Spanish troops on June 22, 1781, only 2 months after the revolt started. “This Spanish force was under the command of Captain Esteban Roberto de la Morandiere and consisted of sixty-six militiamen, forty-three native warriors, and forty French-Canadians.” This force landed at Natchez unopposed and began to reoccupy Fort Panmure, the town of Natchez, and the Natchez District. The next day a detachment of 20 militia and some 80 inhabitants began rounding up all the known rebels still in the district. However, most of the rebels had fled the area and were planning to take refuge with the Indians. The largest colony of these refugees wound up around Chickasaw Bluffs (now Memphis). A month later Colonel Don Carlos de Grande Prè became the commandant of Fort Panmure. He took measures to punish the insurgents and imprisoned seven and charged them with promoting a general rebellion against the government.

The Natchez Court Records adds a tidbit of information about this rebellion not mentioned in other historical accounts I found. This record states that “the revolt took place at Natchez and the widow Truly having built a fort or block-house on her land or the land of Benet Truly and the rebels who took refuge there, fearing they should want water if attacked by the power against them, dug a well.” We would not know this fact, except that, prior to this rebellion Benet Truly had engaged a Thomas Rule to dig a well on this same property. So a year later on April 11, 1782, the court demanded that ”Thomas Rule shall dig the well which he contracted for on the plantation of Benet Truly. The said Rule having been paid for it and the well shall be dug in the season customary in this district. Sig: Grand-Pre.”

Before I continue I have to add that this Thomas Rule is my 4th great grandfather. I knew almost nothing about him until I found court and land records from the Natchez District. I will return to his story but let’s get back to the rebellion. With a bit of speculation, we can mesh the story of the well at the plantation of Benet Truly with the bigger story outlined above. This is what probably happened: When the insurgents at Fort Panmure got word that they were not going to be helped by the British they realized that they had no chance against the approaching Spanish force. Some disbanded and others remained at Fort Panmure. Only a small contingent of the insurgents remained in the Natchez District and they decided to hold up at the Benet Truly plantation where they dug a well. This group fits within the non-local pro-American faction without ties to the Natchez District. In the American colonies, a bigger engagement with the British was about to happen that would result in the end of the Revolutionary War.
 
On September 28th of the same year - George Washington commanding a force of 17,000 French and Continental troops, began the siege known as the Battle of Yorktown. This battle against General Lord Cornwallis was the most important battle of the Revolutionary War because “after three weeks of bombardment... Cornwallis surrendered on October 15, 1781, effectively ending the War for Independence. Prior to this battle, George Washington cut off the escape of Cornwallis by land and sea with brilliant coordinated effort using the French fleet from the West Indies lead by Comte de Grasse.

We see from the shortlived Natchez Revolt that the Natchez District was politically a world apart from colonial America at the end of the Revolutionary War. It appears that the time that a significant portion of the population must have been British Loyalist that opposed the Spanish government. This is an interesting change from a settlement that was first started by the French. This concludes my historical account of the Natchez Revolt of 1781 and the close of the Revolutionary War.

THE MYSTERY OF THOMAS RULE SR AND HIS WIFE ELIZABETH: I am hoping this historical background will help to solve the mystery of my 4th great grandfather Thomas Rule. Who was he? Who did he marry and where did he come from? This is what I know. Thomas was in the Santa Catalina area of the Spanish Natchez District Census of 1792 and from the court records mentioned above he had to have been in the Natchez District as early as 1781. He was eventually married to someone named Elizabeth and they bought property in the District. He died sometime early in 1804 in the Natchez District. They apparently had two sons, Thomas Rule (1786-1850) and Nathan Rule (1792-1869), but there is no record found so far that connects this family together. The younger Thomas married Anna Christeana Jacoby (James) (1786-1853). They are both buried in the Rule Cemetery in Ebenezer Mississippi and they are my 3rd great grandparents. From a memoir written by Christeana’s younger brother (Peter), we know that she and her family arrived at Natchez on June 1, 1800, with her parents, 2 sisters, and Peter. Her parents were Bartholomew Jacoby (1747-1833) and Maria Catherine Mayer (1749-1820). They had traveled from Pine Grove in Berks Pennsylvania. The wife of Thomas Rule through DNA only seems to have been Elizabeth Holloway (1765-1812?) who came to the Natchez District with her parents and her brother Robert. Her youngest brother, James, was born in the Natchez District in 1779. Her father, John, was killed by Indians in Natchez 24 Oct 1781 when James was only 2 years old. To date the only connection I have found between Elizabeth Holloway and Thomas Rule other than DNA comes from the following court record:

P. 69  (about Feb 1783) Elizabeth Holloway vs Thos. Rule. She represents that Thomas Rule owes her $4 and 4 rials for carpenter's tools lent to him, namely one hand-saw and one chisel; asks for payment.

Thomas’s first son would be born about 3 years after this record, so this Elizabeth is hard to understand as the future wife of Thomas senior because she was married to a Cady Raby in 1781. There was another Thomas Rule (1761-1846) from Pennsylvania that lived about the same time as the younger Thomas in this story. This other Thomas died in Mercer County Kentucky and never lived in Mississippi. Just the same, he has been confused with both Thomas Rules (from Mississippi) in this post. He was having children in Kentucky up to 1811 and was buried in Kentucky so he does not fit in with records of these two Mississippi Thomas Rules.

Massive Martian Landslide found in Shalbatana Vallis using Google Earth "Mars"

Shalbatana Vallis Landslide (looking south). Image from Google Earth "Mars" 

This blog was updated on 8-22-2019 and again on 9-12-2022. The Shalbatana Vallis canyon is nearly 800 feet deeper than the Grand Canyon. In this canyon, there are several mudflows but the largest is a huge section involving seven and a half miles (11.5 km) of the eastern flank of this canyon that failed in a massive landslide that involves a total of 66 square miles (171 square km). What is most impressive is that the toe of the landslide liquefied and flowed several miles across the canyon floor and then 1/4 of the way up the west canyon wall. The Shalbatana Vallis is very roughly a 300 mile (480 km) long canyon that opens up into a wider valley on the south end before reaching the Orson Welles crater. It has a delta on its northern end (Chryse Colles) and that delta connects to the larger Chryse Planitia (Golden Plain). A different mudflow at the south end of Shalbatana Vallis was recently identified by Berman D. C. et al (2017).

The upper part of this landslide is similar to slump failures on Earth that form in cohesive soils with a high clay content that progressively fails over an extended timeframe. At the top of the slide there are a few tension surface cracks (see GE image below). In an active slide, these cracks will widen and form a new scarp with a new rotating slump block. The blocks are separated by minor scarps. This slide has 3 or 4 larger slump blocks with smaller ones between. Using Google Earth, a profile section was cut through the slide to determine elevations. The section location can be seen in the GE photo above (Fig. 1).  In the landslides I have studied in Mississippi the toe is a small percentage of the whole feature. But here the base or toe of the slide is longer than the slump. Clearly, the toe is acting more like a mud or debris flow in this slide. The toe of the landslide ran about 4 miles ( km) across the floor of the canyon and then 1200 feet (665 m) vertically up the west canyon wall. This flow indicates that this whole slide happened during a single (non-progressive) event.

Google Earth image of the Shalbatana Vallis Landslide from above
 (top of photo is south)

Using Google Earth coordinates, the south end of the scarp is located at lat 4.300975̊, lon -43.988396̊  and the north end at lat 4.497535̊, lon -43.991300̊. This landslide is not something that happened recently because several small meteor craters can be seen on the landslide surface. There are other smaller landslides in the Shalbatana Vallas and many hints of older landslides that appear to have lost most of their identity from erosion. But it is clear that no water has flowed down this canyon since this landslide occurred. There are numerous small craters in the floor of the canyon and a few larger craters that intersect the top edge of the canyon. These craters help date these features. When this slide occurred there was a significant influx of water to fuel the slide. It could be that a meteor impact created enough ground quake to cause the soil to liquefy thus causing the slide. But it is most likely that there was a rapid influx of water from water trapped in a cryosphere. There are large areas of the surface of Mars where the surface appears to have subsided and created canyons different from outflow channels providing evidence of this cryosphere. 

On Earth similar landslides happen after there is a large influx of groundwater from heavy rain. The influx of groundwater raises the pore pressures in the soil and reduces its shear strength. The factor of safety against sliding drops to unity and the side precipitates. A soil that has shear strength and then suddenly turns into a mudflow, indicates a soil that may have obtained its strength due to some cementitious agent. The key point is that the soil in the toe had to be saturated when this event occurred to produce this mudflow across the valley floor and up the other side of the valley. We know this from similar events on Earth. 

The location of this landslide was submitted as an observation candidate in Oct 2008 and the Mars Reconnaissance Orbiter HiRISE camera photographed a strip of the slump area of this slide (See http://hirise.lpl.arizona.edu/PSP_010461_1845). However, the mudflow at the base of the side was not included. The nearby smaller landslide mentioned above was identified as a landslide and was nicely imaged by HiRISE 04 November 2007. See “Landslide in Shalbatana Vallas” http://hirise.lpl.arizona.edu/PSP_005965_1855 and again on 10 Jan 2009 (see http://hirise.lpl.arizona.edu/ESP_011529_1855).


References:
Berman, D. C., Weitz, C. M, Rodriguez, J. A. P., Crown, D. A, “Geologic Map of the Source Region of Shalbatana Vallis, Mars.” 3rd Planetary Data Workshop 2017.

Google earth images: NASA/USGS
ESA/DLR/Fu Berlin (G.Neukum)

Christmas Parade 1948 or 49 Jackson Ms

A Christmas Parade in downtown Jackson Mississippi in either 1948 or 1949. The location is the corner of North State Street and Capitol Street. Buildings in the footage include Hemphill Drugs, Gandys Steaks, The War Memorial Building and the Old State Capitol Building. Footage was shot by my father, Clyde Maxwell. Many years later my mother and father re-shot the footage on an 8 mm camcorder and added the narration. The background noise is daddy's 16 mm film projector.

Investigating Slab Foundation Failures in Central Mississippi

This post was updated on Oct 28, 2017,  Dec. 21, 2018, and again on June 3, 2020. In this post, I provide a simple method for determining the seriousness of a foundation problem. At the lower end of this scale, you might consider only repairing the cracks. At the higher end of the scale, you would want to relevel and repair drainage problems. However, there is also an issue as to the kind of movement that has occurred. Most foundation failures we have investigated have a mixture of distortion and tilting. If it's mostly tilting then there is little or no damage to the slab. But if it is mainly distortion then the movements have damaged the slab through bending. These aspects are rarely considered by foundation investigators but they should be. The only way to make this determination is to draw elevation contours of the floor using a comprehensive elevation survey as I describe below.

A minimum foundation check should involve a complete floor elevation survey that should at least accurately describe the locations of the highest and lowest floor elevations. The survey plot should have enough detail so that anybody can locate those two points. The evaluation should include a calculation of apparent maximum differential movement which is the difference between the highest elevation and the lowest elevation corrected for any differences in floor thickness between those two points. A much more meaningful survey is one that has either the low point or the high point equal to zero. All of our surveys are done this way. The best way to accomplish this is to spend a few minutes scanning the floor elevations with a Zip level to find the low point. Once this has been found, zero the Zip level to the lowest point. When this is done it becomes much easier to draw floor elevation contours. But note that floor elevation contours only have meaning if you plot the elevations on a scaled floor plan. I should note that these things are not typically done by foundation contractors. Most elevation surveys made by contractors do not have a datum at the low point or the high point and are not drawn to scale. Some elevations are negative and some are positive. This kind of survey appears to be cryptic to a novice and just hard to evaluate even by experienced engineers. If this kind of survey is your only guide, there is a good chance that you will miss subtle drainage problems that are connected with the movement. So when I get this kind of survey the first thing I do is to shift the elevations so they are all positive. You can do this yourself. If the lowest elevation is -2 inches, just add 2 inches to every survey point. It's the same data but now it's easier to interpret and to contour.

The literature on slab foundations constructed on expansive soils recognizes two failure modes: one is edge-lift and the other is center-lift. All the failures we have seen in central Mississippi where expansive soils are present, fit into these two categories. It is important to recognize that edge-lift failures are often related to poor drainage near the higher floor elevations. Center-lift failures may be related to a perched water table or poor drainage several places around the house. Before investing thousands of dollars in a foundation repair, homeowners should have a better quality floor elevation survey made that more clearly shows the movement, identifies the failure mode, and shows how that movement changes across the foundation.

The average annual movement can be computed when the age of the structure is known. Experience has shown that the average annual movement rate tends to continue unless repairs are made that specifically address the cause of the movement. A cookie-cutter foundation repair that just involves releveling will not reduce the movement rate if the movement is heaving (upward) from expansive soils. Many of the foundation releveling procedures will help to retard settlements.  But many foundations in Mississippi have a mixture of settlement and heave. Some in central Mississippi are all heave (uplift). My view is that when the movement rate is over 1/4 inch per year you have a potentially serious foundation problem that probably includes significant heave. The worst-case scenario is when the movement rate is 3/4 inch per year or maybe a bit higher. The 1/4 inch per year limit is strictly an arbitrary number. I assume that no one wants to have foundation repairs done any more often than once every 12 to 15 years. So over this time frame, you can accumulate 3 to nearly 4 inches of differential movement with the 1/4 inch per year arbitrary limit. Total movements in this range is a limit that is often used in the real estate industry.

Experience has also shown that if a structure has an average movement rate of about 1/4 inch per year that damage will begin to show when it is about 3 to 5 years old and that damage may first look like minor cosmetic issues. By the 5th or 6th year, the damage begins to look more like it is related to foundation movements. So if you buy a house that is less than six years old it could have a fairly significant foundation issue that might only show up through a floor elevation survey. So for a rule of thumb in central Mississippi, I recommend that if you are buying a house that is newer than say 6 or 7 years and does not show any evidence of foundation damage, the floor elevations should be checked and the average annual movement rate computed. A residence that may not need a foundation check would be at least 8 years old and show no damage that might be attributed to foundation movement.

I recommend a detailed foundation evaluation for any residence with a 1/4 inch or more annual movement rate. The detailed check should include the minimum check requirements and floor elevations and contours plotted on a scaled floor plan with a zero elevation datum. If the owner does not provide a scaled floor plan then the house has to be measured and a floor plan produced with those measurements. With a detailed check, I usually show the lowest elevation equal to zero. Elevations are adjusted for different floor thicknesses. I show on the plan the base elevation survey measurement and the adjusted elevations, I then draw floor elevation contours at ½  to 1-inch intervals. Using this plot as a guide I then look for contributing drainage issues. This may mean a second trip to the property. In addition to recommending the kind of foundation repair, I may recommend checking the plumbing lines for leaks or soil borings. Generally, I like to see these things done before I make recommendations for repair, but a soil boring can be made later as a check against your conclusions made with just the survey. If I suspect heaving from expansive soils, then I may request a 10-foot deep boring nearest the highest elevation to see the depth of the clay (CH soil) and possible contributions of a water table.

The benefit of the detailed foundation study is that it maps out the details of the movement. It shows the areas of distortion (bending in the slab) and what parts of the house have more slope than others and sometimes directs you to a serious problem like a broken plumbing line or an area with poor drainage. If an area of poor drainage is resulting in heave, the slope of the slab may continue to increase as you get closer to the source of the water. When you see this a classic edge lift condition has been identified that is well documented in the literature. It is also important to look at how nearby larger trees are related to the movements.

Following this procedure, it is possible that a newer house with minimum damage could be flagged because the movement rate is excessive. This does not mean that it has a foundation problem, but that it is at higher risk for future foundation problems. With a detailed study of the structure, maybe a related drainage problem can be found and corrected. Also, there are exceptions - not every structure with a high movement rate will continue to move at that rate and there is another issue in that not all structures with differential movement will result in wall cracks. It is rare but a structure can move so that it has an even slope across the whole structure (pure tilt). In this case, the only damage is floor slope. Whereas there are no cracks, it does make the structure less usable if the slope becomes excessive.