(NBC News) The near disaster at California’s Oroville Dam is just one recent examples of the nation’s crumbling infrastructure that the Society of Civil Engineers says is only getting worse.

The Society’s once-every-four-year report card is out, and hasn’t changed since the last one. It gives the nation’s infrastructure an overall grade of “D+”.

Bridges earn a “C+” because almost 40 percent are over 50 years old, and 59,000 are structurally deficient.

Roads get a “D” because one out of every five miles is in poor condition.

“Unfortunately we have a tendency to wait for disaster and be reactive and we want to be proactive and not reactive,” says engineer Tom Smith.

Being proactive comes with a price tag, which happens to be a lot higher than the $1 trillion President Trump is proposing on infrastructure improvements.

The engineers say $4.5 trillion is needed.

One reason infrastructure has suffered is because the federal gas tax hasn’t been raised since 1993.

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