Maple Garden, a Recreational Park with Function of Flood Detention in the City Center, Taichung, Taiwan

The Maple Garden project is the first and only recreational park below ground level in Taiwan. It is a local landmark on the busy Taiwan Boulevard in Taichung City. With a land area of 30,000 square meters, it was the proposed site for the Taichung International Expo Center; however, for some reasons the project was ceased and cancelled after excavation. As a result, a huge and dangerous boomerang-shaped ground opening, with a depth of about 20 meters, was left on site.

The opening was seriously affecting the city’s appearance, threatening citizen’s safety, and limiting the usage of the land, landform-wise and budget-wise. The local government was under the pressure of the general public. Something had to be done in a short time and within the budget.

A creative, exciting, and feasible idea was proposed to solve all concerns with given constraints and conditions. The idea was to make use of such landform to build a multifunctional park below ground level; serving the functions of flood detention, exhibition, recreation, park, and regulation of air quality of the city. Environmentally-friendliness and concrete reduction were the main foci of the landscape engineering concept for the project. This idea was adopted by the government, and hence the land was re-planned accordingly.

Considering the overall project requirements in cost-efficiency, construction convenience, environmental friendliness, and landscape beautification, the applications of geosynthetic products and relevant engineering methods were the most suitable and feasible approach to carry out the work. The project largely adopted the various geosynthetic products such as woven geogrid (ACEGrid^®), woven and nonwoven geotextile (ACETex^®), soil bag, vegetation mat (ACEMat^®), etc. in reinforcing and enhancing the landscape. The Rather than building traditional RC retaining wall, the surrounding wall and slope of the opening were built with wrap-around reinforcing method with ACEGrid^® GG geogrid, soil bags, and drainage boards and pipes forming mechanically stabilized earth wall (MSEW) and reinforce soil slope (RSS), to support the loading coming from the road and sidewalk above and around the Maple Garden, and to provide rooms for vegetation on the wall and slope surface. This method took advantage of in-situ soil to cut down the construction time and cost, and greatly reduced the use of concrete.

Moreover, a detention pond of 200,000 cubic meters was to be constructed and connected to the city drainage for regulation of flood. In order to merge with the landscape naturally, geotextile, soil bag, erosion control mat, gabion, gravel were used to construct an ecological detention pond to fulfill this demand. The bottom of the detention area was made of compacted gravels and covered by ACETex^® PP woven geotextile as the filter layer. Then the ACEMat^® YS erosion control mat and gabion were installed on the geotextiles to serve as a medium for vegetation and erosion control and shape the outline of the landscape. Various trees and shrubs were planted to further beautify and enrich the appearance of the park. A restaurant with a circular design front was built at the inner corner, merging with the reinforced wall and facing the pond; an artistic exhibition center was built at the entrance of the park beside the Taiwan Boulevard; these building structures not only enhanced the function of the park, but also added some elements of civilization and culture to the atmosphere. Walkways were constructed with different methods at different sections in the park. Crushed aggregate, timber, and wood chips were used in permeable pavements beside the pond. The perimeter sidewalk built around the pond was about 388 meters. All these artificial, but natural, settings built up the beauty and spirit of the Maple Garden.

Geosynthetic product applications play a major role in building the park, and significantly contribute to the concrete reduction and environmental friendliness demand of the Maple Garden project; and the use of in-situ materials and geosynthetic products brings convenience to the construction and brings down the cost at the same time. Reshaping by the ecological engineering methods, the project has successfully converted a problematic ground opening to an attractive and environmentally-friendly scenic site. It not only provides a recreational place for the general public, but also serves as an urban drainage regulator in case of flood. Moreover, the vegetation planted throughout the garden has increased the city’s green coverage by 28,000 square meters, and contributed to lowering the urban heat island effect. This creative thought and construction of turning a problem into an achievement has gained many awards and recognitions from the construction and geosynthetic industries in Taiwan. And it further wins the 2013 FIABCI Prix d’Excellence Award in the Public Infrastructures/Amenities Category at the 65th FIABCI World Congress (2014), Luxemburg. Started as a remedy and ends up with glory, the Maple Garden project is beyond construction, it is in fact a meaningful and remarkable art.