The 400 foot long Aime-Despatie reinforced concrete dam was built in 1972 to replace a series of historic structures which powered the old flour and saw mills of Mill Island in Terrebonne, Quebec since the early 18th century. Named after a prominent resident who lobbied successfully to maintain the island shores free of construction and accessible to the public, this functional dam plays a symbolic role, linking the town to its island suburbs with a pedestrian footbridge.

In celebration of the town’s 350th anniversary, this interactive landscape lighting project was designed to provide a dynamic focal point for the town, allowing for a continuously renewing lightshow to be programmed and enjoyed for years to come.

The dam was originally lit with a series of oversized 16 feet lampposts with no optical control. In the new installation, overall glare is reduced by diminishing light levels and precisely focusing flux on the pedestrian walkway. Freed from veiling lamp image, pedestrians are able to experience the river from both banks and while crossing from one island to the other. The view to the South features a multilayered spillway, composed of:

1. A continuous flowing chute, with smooth, dark water arching over concrete spillways,
2. An animated boil of rushing whitewater
3. A gradual transition to the tranquil waters of the river beyond

Each of these three layers is highlighted with a distinct layer of light, creating a programmable low-resolution matrix. Where the chute is enlivened by the mirror-like specular reflection of the piers, the white water is illuminated by a series of rectilinear beams (typically used for façade lighting), and the further reaches rendered by a wider flood projector, allowing for a gradual fade to darkness.

Evolving over the seasons and punctuated by special one day events, the dam was programmed with a total of 15 colour changing scenes. Precisely aimed colour washes are overlayed with punctual rippling textures to highlight the perpetually renewing, random, motion of the water. In addition, pedestrians crossing the dam trigger a number of motion sensors, releasing various courses of white light across the width of the crossing, from east and west sides of the embankment. The light show is activated at sunset and turned off at midnight, with the functional lighting dimmed by half from midnight to 6 am or when no presence is detected for 5 minutes.

On a tight timeline for the town celebrations, this project presented numerous design and installation challenges. Following approval by three levels of government, the project construction kicked off in late fall, requiring the installation to be done in near freezing conditions, while suspended over rushing water. No mechanized equipment was permitted on the dam given the low loading tolerances of the structure, forcing teams to use ropes and customized rigging. IP67 fixtures were sourced locally to ensure resistance to the elements and regular continued maintenance.

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