“For well over a decade, I have called Phil [Sirles] to ask crazy or unusual questions about the application of geophysics to unique or difficult geologic or geotechnical problems. Often, we end the conversation with Phil telling me ‘…no Aaron, geophysics won’t work there [to solve the objective], you are better using the physical approach of test pits, CPT, drilling or hand sampling…’. I appreciate that Phil’s dedication is to the appropriate use of the technology, not the next project to be awarded. It is refreshing compared to others I have worked with in the industry”.  

Aaron Burns, P.E., P.G.
MWH Global


 “We have been calling Dennis [Sack] at Olson for years whenever we have any questions about nondestructive testing and evaluation, because we know he will help us determine the best path forward for our clients – even if it does not involve services they provide!   When we do need their services, for evaluating tunnel linings or bridge foundations, the work is done quickly and effectively.”

Margaret A. (Peggy) Ganse, P.E., P.G.
Shannon and Wilson, Inc.


 “Ferrovial Agroman has a long history of collaboration with Olson Engineering. I still remember our first work together in 2000, in one of our P3 projects in Toronto. The privatization of the 407 ETR toll highway in Toronto carried with it the obligation to extend the existing facility an additional 25 miles (40 km). Olson helped us with some NDT testing to evaluate concrete quality and strength in some very large spread footing foundations for a 200 ft (60 m) span bridge.

We renewed our collaboration with Olson in 2007 when Cintra, the infrastructure investment arm of the Ferrovial Group, took charge of the Indiana Toll Road (ITR). The public Owner had established a mandatory capital expansion program. As part of this, several very important bridges along the existing facility, built in the fifties, had to be widened, brought to present standards and substantially improved. These included some bridges over one mile in length. The project involved some very complex structural work including modification to the steel structure, jacking and tilting the decks up to 4 ft to provide standard crossfall, etc. In what may have been one of the most extensive condition evaluations carried out by the private sector in North America, Ferrovial Agroman turned to Olson to provide both NDT and destructive testing for an exhaustive evaluation of the condition of the bridges.

Since then, Ferrovial Agroman has worked with Olson for most of its needs related to NDT and condition evaluation of bridges in North America. Ferrovial Agroman has been and is involved as contractor in many toll road projects in the USA and Canada. Many of these are expansions of existing facilities with improvement of existing non-tolled lanes and addition of additional toll lanes, such as the three projects in the DFW area: NTE, LBJ and NTE 35W, with a combined construction cost in excess of $4.5 billion. Because these projects are built over and as expansion of an existing facility, there has always been some need to, besides load-rating, evaluate in-depth the structural and durability condition of existing structures which were widened instead of replaced. In all of these projects Ferrovial Agroman has collaborated with Olson, as one of the foremost players in the field. “

Fidel Sáenz de Ormijana
Chief Technical Officer
Ferrovial Agroman


“Olson consistently has been able to meet all of our urgent geophysical investigation project scheduling needs, often in a matter of days.  Further, their deliverables demonstrate a strong technical quality in a concise format that helps the reader understand complicated geophysical analysis by integrating those data with our geotechnical information”.

Mark Vessely, P.E.
Vice President
Shannon & Wilson


“CTL|Thompson and I have engaged Mr. Sirles for almost 20 years to provide engineering geophysical services and assist us with dozens of geotechnical and geologic hazards investigations for major civil projects in Colorado and nearby states. We’ve been impressed and completely satisfied with timeliness, capabilities, performance and particularly his explanations of complex physics concepts in the investigations he has managed for us. Phil always helps us find the right geophysical technique to help us evaluate subsurface conditions. We look forward to working together in the future.”

David A. Glater, P.E., C.P.G.
Principal Geological Engineer
CTL|Thompson