Your misgivings about "technician" for "técnico" are well-founded. The word "technician" is technically (pardon the pun) correct, in that a technician is "a person skilled in mechanical or industrial techniques or in a particular technical field" (Collins), but in practice it's the wrong term here. A technician is essentially a hands-on person with technical knowledge and competence, but is a person of lower status and responsibility than a project manager. It is often someone who operates machinery or apparatus of some kind, like a laboratory technician. In the engineering field, a construction technician is like a kind of foreman, working under the orders of a supervisor.
das.hre.iowa.gov/html_documents/job_descriptions/JobSpecs/ConstructionTechnician-04320.htm

It is really better to name the specific technical profession, which in this case is engineering. This person is almost certainly either a civil engineer or a construction engineer (they are not quite the same thing), and probably the latter, but we can't be sure which, so I think "engineer" alone would be best.
http://en.wikipedia.org/wiki/Civil_engineering
http://en.wikipedia.org/wiki/Construction_engineering

As for "titulado", it doesn't mean "certified", it means "qualified". It means that the person possesses a "título", which usually, and certainly in this case, means a university degree. In Spain there are two grades of "técnico titulado", the "técnico titulado superior", who has to have a degree (in this case an engineering degree) equivalent to master's level (licenciatura or grado + máster), and "técnico titulado medio", who has to have a diplomatura or grado.
http://asturias.fspugt.info/Sectores/Autonomica/Convenio/Aut...

So we could call this person a "degree-qualified engineer", and that would be the safe option, since we cannot be completely sure of the status. It's a perfectly standard term in English:
https://www.google.es/search?q="degree qualified engineer"&n...

However, I think we can we virtually certain that a project manager qualified to certify something as important as a power plant is a técnico titulado superior, and is equivalent to what is called a chartered engineer in the UK, which is broadly equivalent to a professional engineer in the US: someone who holds a degree, usually of master's level, and is professionally registered:
http://en.wikipedia.org/wiki/Chartered_Engineer_(UK)
http://en.wikipedia.org/wiki/Professional_Engineer#United_St...

So if the translation is for the UK, I would be inclined to use the term "chartered engineer" here.


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Note added at 1 day3 hrs (2012-10-21 18:45:25 GMT) Post-grading
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A pleasure, Mar!