simplicity does not always imply a lack of complexity. such is the case with the recently completed illumination of the Bazacle Causeway on the Garonne River in the city of Toulouse, France.

This particular scheme-a luminous line of light submerged in the river-was conceived by lighting designer Roger Narboni and his firm Concepto, based just outside of Paris. One of approximately five commissions that will be completed by the end of 2006 as part of a larger lighting master plan for Toulouse, Concepto is no stranger to landscape lighting scenarios or master plans. In 2002 Narboni and a team of engineers and communication specialists were selected through a competition to create a set of lighting guidelines for the city, in which their winning proposal focused on the illumination of the Garonne. The city's goal in implementing the master plan is to create a nocturnal image by highlighting its rich architectural heritage in an efficient and ecologically sensitive way. Officials have allocated close to 1.3 million euros per year (from 2004 to 2006) just for lighting. Distinguishing itself from other illuminated building and streetscape projects, the causeway lighting design is the only one to directly address the Garonne.

Prior to the master plan, the city had no real lighting scheme to celebrate important monuments and spaces, or to create a nighttime experience. 'Especially the Garonne,' Narboni says, 'it was completely out of mind, and it wasn't a place where people would go at night because it was so dull.' The causeway location is thought by historians to be the original river crossing point. Once a jagged series of rocks that marked a natural elevation change, they have given way to a man-made fortified concrete causeway with a set height difference of 15 feet. Narboni's idea was to symbolize this spot. 'When you look at the map of Toulouse,' he says, 'it was obvious that this was the important thing to do.' Rather than illuminating the riverbanks and neighboring buildings, Narboni realized the luminaire fittings could be recessed within the 886-foot-long causeway, the width of which was extended slightly to accommodate a trench to house the 265 new fixtures that are connected end-to-end. This meant that the illumination would come from the river, an exciting and redefining proposition.

When the team started to research available fittings that would provide an extremely luminous light, and be visible from 980 feet away, they found nothing. Additionally, because the causeway is an active walkway/work area for technicians from the nearby hydro-electrical plant during the summer months, a low-voltage source was necessary. As a result, Narboni considered LEDs. 'When you are working in low-voltage, the cables become big very quickly. If we had used a normal fitting that consumed 30 or 40 watts, the wire would have been five feet in diameter.' A fitting that would only consume two watts was needed. The designers met with eight companies before partnering with Targetti-Extérieur Vert.

The principal difference with these custom-designed luminaires is that they emit light horizontally, rather than vertically, toward the horizon line. Internally, each of the fixtures is fitted with a translucent luminescent lateral emitting bar and aluminum reflector, lit at each end by one high-intensity blue 1W LED. The approximately 8-inch-wide, 32-inch-long polycarbonate cylinder is treated with a transparent resin for waterproofing and strength. The cylindrical shape and a mirror on the underside increase the reflectivity and ensure an even spread of light. The fixture is wet-listed with an IP68 rating and can be fully submerged in water. Low-voltage power cables run underneath the luminaires in the concrete, with the transformers located 650 feet away on either side of the river. 'The idea was to use the cylinder like an optical fiber, but we did not know if it was good enough in terms of the luminance, so we made a prototype,' says Narboni. 'This two-watt consumption gave such an amount of light, it was incredible. We could not have thought that the lighting would be so intense.' Because the light emission is at an angle of five degrees horizontally, the luminous line can be seen from the riverbanks and neighboring bridges, without causing glare. 'It's quite revolutionary for this kind of product,' states Narboni, and in fact, the company will debut a family of products around this original design at Light + Building 2006.

This seemingly simple gesture of a luminous line redefines the role of illumination in a landscape setting. 'It was a fantastic project, a human adventure,' says Narboni. 'Because we started without knowing the end-did we have the best idea?' And the answer is yes, for unlike other riverfront landscape lighting approaches, which often light buildings, bridges, and monuments surrounding the water, in this instance the very place itself, the Garonne River, becomes the star. elizabeth donoff