Sewer Main Rehabilitation with HDPE Lined Solution

A sewer main rehabilitation is featured in this case study, which showcases the value of a concrete protective liner (CPL) to help prevent concrete degradation from corrosives.

Context

The Water Pollution Control Facility (WPCF) in Cedar Rapids, Iowa, treats an average of 45 million gallons daily (MGD) of water from residential and industrial sources. It serves approximately 180,000 residents in Cedar Rapids, Marion, Robbins, Palo, and portions of Linn County and an additional 20 MGD of industrial users. The facility was constructed in the late 1970s and has undergone multiple upgrades.

On an early morning in January 2024, staff reported steam rising from the ground and soil subsidence directly over a vital 84-inch reinforced concrete pipe (RCP). After installing barricades, the pipeline was video-inspected, and overlying soils were removed to prevent further collapse. The video of the pipeline suggested microbial-induced corrosion (MIC)—related damage was the cause of the pipeline failure. MIC is a naturally occurring process typically caused by the chemical interaction between sewer pipes and the substances that flow through them (1). Over time, this process can significantly weaken the integrity of the pipes, reducing their overall lifespan and effectiveness (2).

Due to the extent of the MIC damages throughout the pipeline, several options were evaluated before deciding on removal and replacement.

Opportunities

Concrete is one of the most ubiquitous construction materials today. It is strong, durable, and cost-effective for most structures. However, it does have one weakness: corrosion. Corrosion is not a typical obstacle, but it is always a potential threat in wastewater applications. The city needed to replace about 900 feet of 84-inch concrete pipe, so it had an opportunity to implement technologies that would maximize the service life of the rehabilitated infrastructure.

Solution

Since the MIC attacked and collapsed the top of the concrete pipe, flows were maintained through the facility by utilizing the intact portion of the pipe located beneath the normal water line. Over the next few weeks, the contractor installed sheeting to protect existing infrastructure and installed bypass pumps. Excavation and pipe replacement began in early March 2024. The contractor replaced the damaged pipe with 84-inch concrete pipe segments lined using AGRU HDPE concrete protective liner (CPL). This 2 mm high-density polyethylene (HDPE) liner protects concrete structures against corrosion, creating infrastructure that combines concrete’s strength and durability with HDPE’s chemical resistance to create a long-lasting solution.

Additionally, approximately 3,000 square feet of 5 mm HDPE Ultra Grip CPL sheeting was cast in place within existing concrete structures that had degradation due to MIC. AGRU Ultra Grip CPL significantly extends the design life of concrete structures, maximizing a municipality’s investment in construction applications.

Outcome

The pipe and concrete structure emergency rehabilitation project was completed in late March 2024. The fast turnaround and prompt response were crucial for ensuring proper treatment of the city’s wastewater and returning the plant to normal operations within 17 days.

References:

1. A. Schweitzer. “Corrosion-resistant linings and coatings.” CRC press. (2001).
2. Ghafari. “Investigation of water transmissivity of water-resistant concrete with acrylic polymer modifier used for improvement of tunnel temporary support.” (2011).