The flowing chute of water was one of five key elements that required illumination.
Photo: City of Terrebonne
Approximately four years ago, Québec firm CS Design (which merged in March 2025 with HLB Lighting Design under the HLB brand) was tasked with a park project involving an island connected to Terrebonne, a suburb of Montreal. The ambitious goal consisted of an overhaul of the park, a new theater, and a building for a skating rink. CS Design completed a master plan for the entire park, and it identified key opportunities for illumination including a dam, which also served as a pedestrian bridge that led from the island to a satellite neighborhood. Then COVID-19 hit.
In the post-COVID world, the civic government changed and axed the larger project, but the administration was still excited about one aspect of it—the dam. Illumination of the dam and pedestrian bridge was anything but straightforward since the dam falls under the purview of various government agencies.
“Originally out of scope, we prepared an esquisse [sketch] for the dam to convince the officials of the high potential of the structure,” explained Conor Sampson, lighting designer and principal of the Canadian office of HLB. “Following the municipal election and the arrival of a new mayor, we succeeded in convincing the administration to move forward, and in 2023, the project was finally in design development. Construction was achieved eight months later, a pretty quick timeline for this kind of infrastructure project. During that time, the plans had to be reviewed and approved by three layers of governmental institutions, as the dam belongs to the environmental protection office [and] the island to the Culture and Heritage Ministry, but the project was financed and orchestrated by the city.”
Five key illumination elements were employed in the project including a flowing chute, with smooth water arching over concrete spillways; a boil of rushing whitewater; transitioning to the tranquil waters beyond; a series of concrete piles; and a horizontal deck that was functionally lit from lamp posts. The lighting approach was broken down into three zones: the highlighting of the structural piers, illumination of the white water rapids, and the tapered washing of the fast-moving and smooth dark water farther out in the river.
“Water is a unique medium for lighting: it is either transparent or acting as a mirror, and therefore almost impossible to light when immobile,” Sampson said. “But as water moves and falls, swirls and bubbles create constantly renewing textures that catch light. It was an amazing opportunity, as we had the chance to have these different layers of water texture complementing each other. The main light focus is on the water waves, but the texture of the backwash beyond reveals exceptional and lively patterns as well. We forced ourselves to use a very colorful light palette instead of our favorite white tints, as the river is not clear and is a dominantly brown hue.”
The completed installation, viewed from the mainland to the island.
Photo: Etienne Demassy
CS Design called upon a various range of small to larger fixtures, both projector and linear luminaires, to create the different layers of lights, with vibrant colors and contrasting intensities. A series of linear, Lumenpulse Lumenfacade RGBA luminaires with a narrow spread were used to highlight the white water closest to the dam, with Lumenpulse Lumenbeam RGBA projectors employed to reach further out into the river. All fixtures used DMX protocol and connected into a Pharos controller.
“One of the main challenges was to have fixtures below the deck,” noted Florent Couedou, a lighting designer and project manager who completed the project while working for HLB. “We looked at different ways of installing the fixtures, like a bucket and a crane but the issue was that the rating of the bridge was not made known to us.” As a result, the designers turned to “spidermen” who rappelled off the side of the bridge to install the fixtures among difficult conditions including freezing waters and slippery decks and handrails.
Colors can change with the seasons including this winter color palette.
In addition to the lighting of the water, the chute, and the structural pillars, CS Design was also involved with the replacement of the functional fixtures aimed at the deck. The original bridge possessed a series of lamp posts that were too tall, spewed light, and were blindingly bright, so the designers took the mountings, installed shorter poles, and used optics that were tailored to the deck of the dam. Lumenpulse Lumenquad fixtures replaced the existing post-top fixtures, with photometry targeting at 10 lux with 1:4 uniformity at 3000K CCT.
“We had to add power and use the bases of the existing lamp posts to install new lamp posts that were shielded and directional,” Sampson noted. “This included adding a lot of electrical infrastructure on the bridge. In addition to poor visual comfort, previous lamp posts were spreading light in the river, resulting in light pollution that affected wildlife and plants. From a light pollution perspective, the light is now concentrated on the area that we want illuminated. We have a section lighting the piers on both sides, one set of lights illuminating the whitewater, and one that aimed at the spillway.”
Precise narrow optics (Type II) with back shield accessories were employed to frame the deck on the bridge and improve the contrast of colors on the water. The system is controlled by an advanced DMX/RDM interface with custom schedules and behavior for each layer of light: the dynamic illumination shuts down at midnight, while the functional fixtures remain on for security purposes, but a temporization allows the light to dim to 50% when no presence is detected.
The most innovative part of the project, according to Sampson, is the interactive component provided by four occupancy sensors linked into a DMX control system. There is a resting state that is disrupted by anyone walking across the bridge; as pedestrians cross from one side to another, it triggers sensors that allow the program to detect their direction of travel, launching various ripple effects that follow pedestrians along their path, before bouncing on shore. The scenography evolves throughout the year, with special events featuring various effects and colors. One example was a Halloween scene that appeared when multiple pedestrians activated the sensors in sequence, triggering a scary strobing effect across the dam, as if the bridge was a haunted house.
The pedestrian bridge serves as an essential link for the neighborhood, as it is the only way for people to reach the center of the town. Once the project was complete, local politicians and residents turned out to celebrate the structure’s transformation.
“We think that the project provides a lot of enthusiasm among residents, and kids’ reaction to the interactive effects are always joyful,” Sampson said. “Once they understand they can trigger the light effects, it often arouses their curiosity and becomes a game.”
the Designers | Conor Sampson, Member IES, is a lighting designer and the principal of the Canadian office of HLB Lighting Design.
Florent Couedou, Member IES, is a lighting designer and project manager. He completed the project while working for HLB Lighting Design.Marc Laliberté is an engineer and project director at Tetra Tech.
Emmanuel Scott is an engineer at Tetra Tech
