Beneath our pattern of survey monuments is a sub-pattern of sandblasting. Intended to mark lines in the concrete and define the edge of our sediment pattern, sandblasting the Delta Garden has been a challenging and satisfying process.

Our pattern is complicated, combining many compound curves to create the illusion of flowing water through the space. A stencil could not be created for the entire space (it’s simply too big) so we reduced the curves to 10 radiuses and hand-drew the curves onto the concrete with chalk – over 200 pieces of it.

We then devised a method of using 20 plywood forms (the positive and negative shapes of those 10 radiuses) to mark our pattern. The same plywood forms were used again to protect the concrete during sandblasting.

(Ironically, in order to accurately apply our pattern, the Delta Garden needed to be surveyed. These marks delineated the edges of the future planters – ie. the ‘islands‘ in the ‘delta’ – so we don’t waste time sandblasting areas that will be covered).

The process of sandblasting spanned many weeks (with some breaks in between), taking us from sunshiny Autumn days, into the frosty months of Winter. We still have part of the Delta Garden to go, but we must wait until Spring when the final concrete is poured.

We are lucky to be working with a skilled sandblaster who’s excited by our complicated plans and patient with the aesthetic necessities of creating public art. This is not an easy project from a technical standpoint, so it’s essential to work with skilled craftspeople.

The next steps are more complicated still – marking and installing 12,000 survey monuments into 1600 square metres (17,200 square feet) of concrete. How do you eat an elephant? One bite at a time.