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03-17-21 | Feature

Elevating Bridges with Design and Function

Centennial Lakes Park
by Todd Halunen, PLA, ASLA, Kimley-Horn, Twin Cities

Nearly 30 years after completion, the bridges at Centennial Lakes Park in Edina, Minnesota were deteriorating and in need of repair. Realizing the need for all new structures, the city reached out to landscape architecture firm Kimley-Horn for consultation on the project. The new ADA compliant designs feature stone veneer facing and corrugated steel arches. The ornamental steel coping with LED puck lights is reminiscent of the old bridges.
A signature feature of the park, the old steel bridges were rusting and narrow with steep stairs making them inaccessible for strollers and mobility devices.
The 24-acre park features a putting course and walking paths around a 10-acre pond. The water is groomed for ice skating in the winter and open for paddleboats during summer, so it was important the bridges be high enough to accommodate visitors and maintenance vehicles to pass below. Boulder retaining walls were placed by the water's edges and salvaged, saw cut granite slabs act as steps between the lawn and new concrete walkways.
Colored to match existing walkways using a concrete stain, new 8' wide paths were designed above a 4" aggregate base with 2' square by 8" thick sawcut diamond centered accents.
Formerly the site of an old quarry, ponds were built into the gravel pits and serve as stormwater management and flood control. The amphitheater at the south bridge is now accessible with ramps leading to the existing Hughes Pavilion.
Decorative single pole bell lights were installed at bridge abutments and ornamental, curved metal railings span each crossing set into stone pilasters at each end. The new bridge designs were carefully thought out to appear built at the same time as the existing park features and provide a wider deck for passing visitors. Mature pines, cattails, and other important plantings were not disturbed during construction and continue to thrive.

Centennial Lakes Park is a 24-acre city park in southeast Edina, Minnesota at the site of an abandoned sand and gravel quarry. Built over a ten-year period with the first phase completed in 1992, the park features more than 1.5 miles of paved pathways meandering around a 10-acre pond and adjoining grounds. Besides being the primary amenity of the park, the central pond serves as a stormwater quality pond for the cities of Edina and Richfield and provides flood flow mitigation for the Nine Mile Creek watershed.
Background
The original park construction included two pedestrian bridge crossings over narrow channels of the central pond to provide convenient connections between activity centers and park spaces without requiring users to circumnavigate the pond. The original bridges were designed to allow for summertime paddleboat access and wintertime ice skating and ice maintenance equipment passage. To provide clearance for these functions, the height of the bridges had to be artificially raised. However, they were not ADA compliant and the steep rise of the steps made them inaccessible for the disabled, people with strollers, and maintenance vehicles. Architecturally, the bridges' iconic features including steel lattice arches and accent lighting made them one of the most recognizable and distinctive features of the park. The bridges have frequently been used as backdrops for weddings, proms, and other special event photos.

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Planning
Maintaining the steel bridges had become expensive and time-consuming as they approached 30 years of service. In 2017, instead of continuing to expend the funds necessary to repair and rehabilitate the bridges, the City of Edina decided to replace them with new structures that would meet current ADA design criteria and facilitate wheeled mobility devices and maintenance vehicles. The Kimley-Horn team of Landscape Architects and civil and structural engineers collaborated with the city to identify the primary goals for the redesign of the bridges. The goals included providing adequate clearance for paddleboats in the summer and ice machines in the winter, minimizing the elevation of the structure deck to limit disturbance of landscaping on the bridge approaches, and capturing the recognized and iconic form and shape of the existing bridges. It was also important to deliver an economically minded design to fit within the park budget, minimize damage to the existing park infrastructure by constructing the bridges with small equipment, and mitigate floodplain fill resulting from approach embankment construction.

Design
The Kimley-Horn team evaluated a range of structure types for the project with city staff and council input-ultimately selecting a design that evokes the traditional design vocabulary common throughout the park and includes details that recall the original iconic bridges including the arch form, ornamental railings, accent lighting, and metal trim. The new bridges provide a wider deck to accommodate park patrons as well as maintenance vehicles, while providing the necessary clearance underneath for summer and winter activities. The arch was delivered and erected on site with small equipment, resulting in minimal impact to existing mature trees adjacent to the structure. ADA compliant crossings of the pond were also available which had not existed since the park's inception. Convenient access for park maintenance equipment and the provision of increased flood storage of the pond are additional benefits created by this project. Beyond the functional benefits the bridges provide, their design complements the park aesthetic and they seem to grow organically out of the landscape, appearing to be original elements of the park. In addition to natural stone headwalls and other decorative elements, the design also includes 500' of meandering access trails-the length necessary to achieve ADA grades and an alignment for park user experience.

Services
As the lead consultant in this bridge replacement project, the Kimley-Horn team led all phases of the project from schematic design through construction administration. Their contributions to the project and to the City of Edina included serving as an invaluable resource to the project, having led the design and oversight of construction of the original park in the early 1990s. By facilitating a process to determine the appropriate design of the form, materials, and integration of a new element within the park, they were able to translate the recognized and iconic form of the existing bridges into the new design and improve the park's function and appearance.

As seen in LASN magazine, March 2020.

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