An employee from China Railway No 4 Engineering Group works on the topping-out of the main structures of Fenghe Ecological Sports Park, the largest public ecological park in Shandong province. [Photo provided to chinadaily.com.cn]

The largest public ecological park in East China's Shandong province, which features a sewage treatment plant in its underground level and a sports park on its upper level, ushered in the topping-out of its main structures on Feb 2.

The Fenghe Ecological Sports Park — covering 19.5 hectares in the West Coast New Area of Qingdao — is located some 600 meters from the Yellow Sea to the east and merely 60 meters from the Fenghe River (Wind River) to the south. The smart eco-park has garnered special attention due to its proximity to these water bodies.

Lei Peng, an engineer with State-owned China Railway No 4 Engineering Group Co Ltd which is building the park, said the park — which combines sewage treatment, wetland protection and daily leisure — requires advanced skills to construct.

He said the project, involving Beijing Enterprises Water Group — a Hong Kong-listed firm specializing in water resource recycling and water ecological environment protection, carries an investment of some 1.8 billion yuan ($253 million), with the construction period set to last 1,096 days, starting May 27, 2023.

Lei said they adopted a composite model of "pollution control underground and landscaping above the ground". Moreover, building such a complex project by the seaside poses challenges such as complex geological conditions and high risks due to coastal operations.

He noted several innovative techniques employed during construction, including a "basin style + island style" excavation method to ensure layered and segmented construction; developing "acrylic acid salt + water absorbent resin" composite grouting materials to counter collapses in the highly permeable sand layers near the coast; optimizing the concrete mix ratio to enhance structural anti-seepage and crack resistance; and fine-tuning the pouring process to control cracks in the large-span bottom plates.

"Once operational in 2026, the park will address sewage treatment needs of the surrounding areas of 112 square kilometers," said Jiang Yijun, Party secretary for the CREC4's project department.