The solution is reducing acquisition and delivery costs. The example is set by Mr Christos Tsaligopoulos of the company S.A.E.E. in Greece. The problem to solve: flood control. Riverbank protection was an urgent need after a river overflowed its banks twice in a short amount of time.
The job needed to be: FAST, STRONG, COST-EFFECTIVE.
The choice was to use gabion retaining walls as they are heavy and therefore able to resist the river during a flood. Material and labour costs are a huge influence on the final price of the containment wall.
And adding the cost of outsourcing from a quarry with the cost of delivery to this arduous are would swell the budget.