Archive for February, 2010

Special Requirements at Vance AFB


Red Rock Consulting and DSO recently completed a project at Vance Air Force Base in Enid, Oklahoma, that had special requirements.  US Army Corps of Engineers required the geotechnical team to core bedrock materials.  The Corps also requested that environmental precautions be taken because the project site was located within the base’s trichloroethylene (TCE) plume.

Rock coring is not a standard procedure in many parts of Oklahoma.  It requires that the rock be drilled using wet rotary methods. 

Wet Rotary Drilling

Wet Rotary Drilling

A five foot long three inch diameter core barrel was used to recover bedrock materials which consisted of siltstone with shale layers.  
Core Barrel

Core Barrel


Core Sample

Core Sample









In addition to coring bedrock, the auger and wet rotary soil cuttings had to be contained in a drum.  Soil samples were then sent to an environmental laboratory to be tested for contamination.  The lab results will determine how the drum of soil will be disposed of.

Placing Suspected Contaminated Soil into Drum

Placing Suspected Contaminated Soil into Drum

Sulfates in Soil, Part IV


Known Sulfate Counties

The Oklahoma Department of Transportation (ODOT) and the Texas Department of Transportation (TexDOT) keep a record of known sulfate counties in their respective states. 

These are counties where sulfates have been verified through laboratory testing and/or sulfate heave has been a problem in the past.  These maps of known sulfate occurrences are helpful for the government agencies and consultants who may have projects in the areas.  If sulfates have been found in or near their project area, sulfate testing and/or preventative measures in design can be taken.

The sulfates counties for Oklahoma and Texas are shown below, courtesy of ODOT and TexDOT (Harris, Sebesta, Scullion, 2004).


 Sulfate Counties in Oklahoma

Oklahoma Sulfate Counties



Sulfate Counties in Texas

Texas Sulfate Counties

Advantages of On-Site Engineering


Commercial and residential projects in Oklahoma do not require on-site geotechnical engineering.  Most geotechnical firms do not provide on-site engineering in their normal scopes of work and fee proposals.  Because of this, many geotechnical engineers never see the site of the project they are providing recommendations for.  Red Rock Consulting always recommends on-site engineering and provides it on each project unless a special exception has been agreed upon with the client for a specific project.     

Geotechnical engineering recommendations are site specific for every project.  Physically observing the site, the surroundings and the subsurface materials as they come out of the ground is crucial to providing the best recommendations for the project.

Marking Boring Locations

Marking Boring Locations


Geotechnical borings should be located on-site by the engineer.  The geotechnical engineer is the only person who has been in contact with the client and with direct knowledge of the project objectives, constraints and concerns.  In addition, the geotechnical engineer is the only person who has communicated with the utility locators. 

Many sites have obstructions or other reasons why the borings cannot be located at the preferred locations.  With a geotechnical engineer on site the decision is made with the proposed project in mind by an engineer familiar with the project and needs of the client.

Field Logs

Field Logs


A geotechnical engineer on-site should always log the borings as the drilling is taking place.  In this case, the drill crew is allowed to focus on the equipment and the “feel” of the subsurface conditions as the borings are advanced.  The geotechnical engineer should communicate with the drill crew regarding drilling, field testing and subsurface conditions and observe and log the soil samples as they are produced.

When a geotechnical engineer logs the borings, site specific questions can be addressed more quickly.  Changes in boring depth and sampling of special soil conditions, which are both discussed below, are two examples of on-site issues that may arise on a project.


Occasionally borings need to be advanced to a different depth than planned due to encountering unanticipated subsurface materials, such as deep or shallow bedrock or very soft materials, for example.  With a geotechnical engineer on site, the decision to extend or terminate the boring can be made without having to return to the site, which would result in additional mobilization and soil drilling charges.


    Communicating with Drillers

    Communicating with Drillers

Oklahoma has a number of soil conditions which can be identified on site by a trained geotechnical engineer.  Two examples of such soils are expansive soils and sulfate rich soils, both of which can be detrimental to construction projects if left unidentified.  A geotechnical engineer, who is on the project site and observing the soil, can identify these problematic soils immediately and have them tested in order to provide proper recommendations to combat such soils. 


The best geotechnical engineering reports are those written by engineers who know the project objectives and who have seen the project site first hand.  The report is written specifically for the site that was observed and the soil conditions encountered.   In addition, if any questions arise during design and/or construction, the geotechnical engineer can provide informed solutions as a result of the onsite experience during the geotechnical investigation.

Wondertorium Children’s Museum

In December 2009, Red Rock Consulting, along with DSO, braved the elements to complete a geotechnical investigation for the Wondertorium Children’s Musuem in Stillwater, Oklahoma.

The museum will be the premiere children’s museum in Oklahoma.  It will be located at 10th and Duck in Stillwater and plans to open in 2010.   The museum is still in the design phase, but here is a conceptual of the building and color scheme.  Rees – Wondertorium

The Wondertorium project team also includes Rees Associates, Cobb Engineering and Trumble Dean.

Wondertorium Children's Museum in Stillwater, OK (December 2009)

Wondertorium Children's Museum in Stillwater, OK (December 2009)


ATV Rigs Get the Job Done!

This past week I was confronted with this…

How do you get a drilling rig through that?

Canadian River in Newcastle, Oklahoma (February 2010)

It doesn’t look all that bad until I tell you there was approximately 1 mile of similar conditions just to get down to the project site.  It would be impossible to use a traditional truck-mounted rig in this situation.  Thankfully, Mohawk Drilling has an ATV rig.

With the ATV rig, we were able to access the site with no problem.  It reminds me of that comedy routine where the guy says DODGE stands for ‘Dem ‘Ole Dudes Go Everywhere! 

Mohawk's ATV Rig goes everywhere

Mohawk's ATV rig goes everywhere

While an ATV rig was neccessary for this project, they are not ideal for every situation.  There is a considerable additional cost for using an ATV rig.  However, when it is needed, the cost is well worth it!  If it doesn’t stop snowing/sleeting/raining soon, we may be seeing a lot more of these guys.


Happy New Year, everyone!  And a special thanks to all my wonderful clients who have kept me too busy to post my new year’s greetings until today.  🙂  Now if we could just get a few dry days, I could get back to work!
Bailey NYE 2009

Sulfates in Soil, Part III

In Part II I talked about the soil stabilization chemicals which react with sulfate-rich soils.  This section covers what happens when the sulfate soil, chemicals and water react.


Effects on Soil

There is more than one potential heave mechanism by which sulfate-induced heave may occur.  The two most discussed mechanisms are through the oxidation of sulfide minerals to form gypsum and the formation of the mineral ettringite (Harris, Sebesta, Scullion, 2004), and possibly of the mineral thaumasite.

The first mechanism is the oxidation of sulfide minerals to form gypsum.  Sulfides such as pyrite and marcasite are created in oxygen deficient environments.  When these sulfides are exposed to oxygen, such as when the soil they are in is excavated, they become unstable.  When these sulfides are exposed, the oxygen acts as an oxidizing agent and surface water oxidizes them.  This reaction causes the soil to become very acidic, which helps to dissolve any limestone that may be nearby.  The dissolution of limestone supplies calcium which can combine with sulfates and water to form gypsum.  The oxidation of sulfides and formation of gypsum can produce significant amounts of distress, but when the gypsum rich soils are treated with calcium based stabilizers, as discussed next, the amount of heave is greatly multiplied (Harris, Sebesta, Scullion, 2004).   

The formation of ettringite is a bit more complex, in that more precise conditions have to be in place for the mineral to form.  In the formation of ettringite, sulfate ions combine with calcium from lime or cement stabilizers, aluminum from stabilizers and/or the clay minerals in the soil and water to generate sulfate heave.  Ettringite precipitates in environments with high pH and high sulfate activity.  This is a common scenario when a calcium-based stabilizer is added to sulfate rich soils.  For example, at standard temperature, the pH has to be above 10 and a water source has to be present.   When sulfate rich clay soils are treated with lime or cement based stabilizers, the pH rises to above 12 and water is supplied during the stabilization process (Harris, Sebesta, Scullion, 2004).  When all of the ingredients are present, they form highly expansive sulfate minerals such as ettringite and thaumasite. 

Ettringite is also known as hydrated calcium aluminum sulfate hydroxide and is known to swell up to 250 percent of its original size when water is present.  Four out of every five atoms in both ettringite and thaumasite minerals are either a part of a water molecule or a hydroxide, which is what gives them the ability to swell to such a large extent (, 2007).   Ettringite damages the soil structure by expanding as it precipitates, resulting in expansion of the soil (Little, Herbert, Kungalli, 2005).  The amount of sulfates present in the soil determines the amount of ettringite that can be formed.  The more sulfates that are present, the more ettringite that can be formed (Ferris, Eades, Graves, McClellan, 1991).

Thaumasite is a mineral that forms in addition to ettringite and is also known as hydrated calcium silicon carbonate sulfate hydroxide.  Thaumasite has an extremely high swelling potential as well, but only forms at low temperatures.  If soluble silica and carbonate are present during the isostructural transformation of ettringite at temperatures below approximately 59° F (15° C), thaumasite can form.  While ettringite formation results in expansion of the soil, thaumasite formation results in a loss of strength of the soil (Little, Herbert, Kunagalli, 2005).

In addition to the amount of sulfates in a soil, the amount and type of clay in a soil also contributes to the extent of sulfate mineral formation and associated heave (Ferris, Eades, Graves, McClellan, 1991).  The addition of lime to sulfate rich soils provides the calcium that reacts with aluminum from stabilizers and/or the clay minerals in the soil and water to form ettringite and to generate sulfate heave.  If more calcium from stabilization chemicals is available to the sulfate rich soil for reaction, then more ettringite can be formed.  Therefore, soils with a high clay content, or higher plasticity clays, which require a higher percentage of lime, cement, flyash or CKD for stabilization, can result in greater amounts of heave (Ferris, Eades, Graves, McLellan, 1991).

The type of clay is believed to play a role in the amount of heave in sulfate rich soils.  Smectites are very expansive clays consisting of three layers.  Clays containing high levels of smectite will require increased amounts of stabilization chemical to become stabilized (Ferris, Eades, Graves, McLellan, 1991), much as described above with high plasticity clays.    Kaolinite is another type of clay mineral.  Kaolinite has only two layers, but the lesser amount of layers may help it to provide more aluminum from its structure to help form ettringite and produce greater amounts of sulfate induced heave (Ferris, Eades, Graves, McLellan, 1991).