Category Archives: Consulting

Six Geologic Hazards to Avoid in Austin

Consulting, Geologic Hazards, Geotechnical Engineering
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Austin is blessed from the geotechnical engineer’s perspective with an extraordinary variety of geologic hazards and  geotechnical challenges that include caves,  expansive clays, running sands, faults and fault gouge, random groundwater levels and man-placed fill  such as found at old quarries filled with who knows what.

If you are new to Austin, (Welcome!), and you are  an architect, structural or civil engineer ,    (or you employ architects, structural or civil engineers – thank you! ) it is only natural to bring  your own  template  of design solutions or expectations from wherever you practiced your profession.

“A savvy geotech report is your first defense against a nasty surprise.”

Everything you know from the ground up will likely transfer very easily.  However, for foundations and pavements you are  best served by a qualified  local geotechnical firm ( i.e. a firm with a long history in Austin)  to help navigate the Austin’s  hidden underground world of geologic hazards and geotechnical challenges.

Here is a list of some, not all, of the  geologic and geotechnical  hazards commonly found in the Austin / Central Texas area:

  1. Caves and karst features – principally encountered in the Edwards formation, rarely in the Austin formation.
  2. Expansive soils -you will find these almost everywhere, but the most troublesome are  the  clays of the Eagle Ford,  Del Rio and Taylor formations.
  3. Running sands – these are found in deep alluvium – particularly downtown near Lady BirdLake.
  4. Faults, and fault gouge – These are found in abundance along the 5- mile wide belt of faults known as the Balcones fault zone.
  5. Man-placed fill – can be found anywhere.
  6. Random Groundwater levels -Just what it says.

Tried and true geotechnical solutions are available  to effectively mitigate these challenges for your project’s foundations and pavements. These solutions include specialized approaches to foundation design and construction.  Each of these will be discussed in a  series of subsequent post to this site.

For your project, a savvy geotechnical study is your first defense against a nasty surprise.

 

Take the Guesswork out of Geotech!

Consulting

Posted by Johnny Flores, P.E (TX). I recently received a proposal request from an out of state organization.  The proposal request contained a site layout plan, a description of the scope of work, suggested boring locations, and suggested boring depths of 50 feet.  It was put together very well – even had a cover letter.  I was impressed.   However, the number and suggested depth of the borings really had no relation to the site geology or physiography or the likely structural loads, since this was a single story building.  A quick check of geologic maps and nearby geotechnical reports confirmed my suspicion.  The project site was located in an area with expansive clay underlain by limestone.  I contacted the organization and explained the above points, suggested they confer with their structural engineer and if the loads were indeed relatively light, they should increase the number of borings and decrease the boring depth.

I am telling this true story,  because it illustrates the importance of using available information, such as geologic maps, nearby geotechnical reports, combined with information about the proposed structural loads and site physiography to develop a savvy field investigation plan.   Geologic maps and their accompanying booklets are written by geologists for geologists.  However, good geotechnical engineers use these regularly in planning investigations and identifying formations.  Excellent geotechnical engineers obsess over them.  With regard to loads, I already knew that similar single story structures in the area had been designed with drilled shafts bottomed in the limestone at depths of about 15 to 20 feet, so more likely than not, a 30 ft deep boring would suffice.

In addition, a quick check from Google Earth Pro indicated the site was flat and level with no trees.  But, it had been previously improved with buildings and parking which were destined to be razed for the new project.   It was obvious from Google Earth Pro images the existing parking lots were showing signs of distress (consistent with expansive soils).  These observations presented additional uncertainty for the site subsurface soil regime and underscored the need for additional borings and perhaps test pits.

The above checks were completed in a matter of minutes at no upfront cost to the client and really helped eliminate the guesswork for the field investigation.

 

5 things you need before you launch your next building project

Consulting

By Johnny F Flores P.E. (TX).  Developers and Owners  from across all  sectors engage geotechnical engineers on a regular basis.  For a successful project, there are 5 things that developers and owners  need to provide the geotechnical consultant to deliver a responsive proposal and report.  Without these 5 items, the geotechnical consultant is forced to make assumptions which may cost money and time.

1)A Site Layout Plan.  This sounds simple enough, but for some fast track projects, a site plan could be an ever changing thing.  The site plan should clearly show  property lines and the limits of the proposed improvement to scale.  And, at such a scale that can be easily read and used by the reader.

2) A Grading Plan.  The grading plan shows vertical relationship of the  existing ground surface to the proposed finished lines and grades.  This plan should include all planned improvements, including finish floor elevations for the structures, and also cross sections for planned civil structures such as ponds, berms, embankments.

 3) Structural Loads.  In the early stages of project development, the structural loads may not be clearly known.  Often times the structural engineer for the project may not have been retained.   At the very least, for a preliminary study, order of magnitude structural loads should be provided.  Subsequently, before final design, structural loads should  be provided to the geotechnical engineer prior to the finalization of the geotechnical report.

4) Schedule. A realistic schedule for the design and construction phase of the project is necessary.  Geotechnical consulting most often includes field investigation by drilling, which, similar to construction, may be limited by site constraints and the weather.  Working around the site constraints may take days or weeks.  Most long delays are due to a refusal of some property owners to grant right of entry, right to clear trees, or right to operate during normal business hours.

5) Budget.  People have been taught in an negotiation, not to be the first to reveal the price they are willing to pay.   Negotiation theory aside,  establishing a realistic  budget will assist the geotechnical consultant in scoping the services to fit.  Here is one big caution.  A geotechnical budget established  for a high rise   project  in Atlanta, may not work in Austin because of differing site conditions.

Johnny F Flores, P.E (TX) is a practicing geotechnical engineer in Austin, Texas.

 

 

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