Introduction

If you stroll through the central districts of Berlin, you are bound to encounter, sooner or later, a hand-operated street water pump. Many of these boast an ornate design and clearly date back to the nineteenth century. You would be forgiven for assuming that these street pumps are quaint anachronisms, retained by some curious accident and cultivated today as musealized symbols of a bygone era. But you would be wrong. Berlin's street water pumps did not lose their functionality with the spread of piped water supply in the late nineteenth century. They just began to serve other purposes. Initially, they covered for those households unable to afford water in their own homes and helped put out fires and water draught animals. Then, they proved a life-saving back-up during crises of wartime destruction and political blockade. In the post-war era, they were used to wash cars parked along the street. They have always been a delight for children, playfully designing their own water infrastructures in miniature. Today, Berliners are being called upon to use street pumps to water nearby trees suffering from climate-induced drought. Independent of both the water mains and the electricity grid, these water pumps are kept operational primarily as a valued emergency infrastructure. So, this apparently redundant piece of urban technology has proven remarkably adaptable to changing circumstances (Figures 3.1– 3.3 illustrate the diverse uses of Berlin's street water pumps over time). Although itself physically and spatially fixed, its socio-material entanglements have shifted repeatedly over time. Berliners can be glad that these pumps were not removed when their original purpose was fulfilled.

The repurposing of existing infrastructure is just one instance of making the past usable. The multiple kinds of usable pasts and the various means of making pasts usable for ‘progressive infrastructure futures’ (Addie, Glass, Nelles, and Marino, this volume) are the subject of this chapter. The purpose of the piece is threefold (1) to define and conceptualize what usable pasts are, based on a wide-ranging literature review; (2) to identify and categorize diverse types of usable infrastructure pasts, illustrated with examples from Berlin's rich history of urban technology; and (3) to explore and suggest ways of mobilizing usable pasts to generative effect today, drawing on the author's own interactions with various publics.