Rehabilitating Unstable Sewer Systems in a Region with Soft Soil Conditions

Project:​ Wastewater Pipeline Network in Quanzhou City
Challenge:​ A coastal city plagued by soft, unstable ground that led to significant settlement. Existing concrete sewer pipes suffered from widespread joint displacement and leakage, contaminating groundwater and failing functionally .
HDPE Solution:​ The city chose HDPE Structured Wall Wrapped Pipes​ for approximately 25 km of new sewer lines, with diameters ranging from DN 300 to DN 1400. The inherent flexibility​ of HDPE was the decisive factor. Unlike rigid concrete pipes that crack under stress, the HDPE pipes could adapt to ground settlement without breaking. The pipes were joined using electrofusion welding, which creates a monolithic, homogenous system that is as strong as the pipe itself, achieving a true zero-leakage​ seal—a critical advantage for protecting groundwater quality .
Results:​ The project was completed quickly and has operated successfully. The seamless HDPE system eliminated the infiltration and exfiltration problems of the old network. This case demonstrates HDPE’s superior performance in areas prone to earthquakes or with weak, settling soils, providing a durable and environmentally safe solution .