Monday, February 25, 2008

Cobblestones: a permeable pavement

Native cobblestones and setts, mostly granodiorite and gneiss were profusely used through the last part of the XIX century to pave the access alleyways to many hilly neighbourhoods of Valparaiso. Examples of these "subidas" these days are being repaired and are found in most of the hills from Lecheros to Playa Ancha.
Originally all the cobblestones were bedded within a maicillo sandy ground, allowing it to be permeable to diminish runoff water. Later improvements have added mortar and more recently even including water piping drainage underneath that haven't been calculated for the episodic rainstorm volume falling in the area every southern Winter. This should be taking into account for any foreseeable restoration work.
On the other hand, heavy use of mortar and volcanic lithologic material from Colina (Santiago) should be restrained. If restoration work is done it should use the same kind of material and original contruction techniques as much as possible.