Biogas pipe replacement

Project background

The process to clean wastewater requires lots of energy, but it also produces energy. At West Point, renewable energy is produced from the wastewater treatment process and has helped power the facility since it opened in 1966.

During the wastewater treatment process, organic solids are pumped into large tanks called digesters that are heated at 98 degrees (Fahrenheit). In the digesters, bugs (anaerobic bacteria) break down organic material and kill pathogens. This activity creates digester gas, or biogas, that fuels two internal combustion engines much like how gasoline fuels an automobile engine. These engines in the internal combustion cogeneration system power generators that produce electricity for West Point. The exhaust heat from the engines provides heat for boilers, digesters and occupied spaces. The biogas contains about 60% methane but also contains sulfuric acid (a byproduct of the hydrogen sulfide in biogas) that wears down the pipes that carry the renewable energy.

Project description

The purpose of this project is to replace parts of biogas piping connected to the digesters at West Point that have leaks or corrosion. Plans for this project include:

• Replacing the biogas piping system for the north and south digester pods
• Replacing piping of various sizes in the treatment plant’s underground tunnel
• Building a new pipe over the primary sedimentation tanks to provide redundancy for an existing buried pipe. The existing pipe would be rehabilitated with a method known as "cured-in-place-pipe"
• Replacing horizontal beams that support biogas piping in the tunnel

The goal of this project is to bring the corroded biogas piping system into safe and reliable condition by rehabilitating the existing network and thereby extending the life of the overall system.

This project will be implemented in 2 phases. Construction will take place entirely within the treatment plant area. Phase 1 construction of the project was completed in October 2020, with phase 2 construction currently underway. Construction of the entire project is expected to be completed by 2027.

What to expect

Construction may require temporary partial shutdowns of digesters for inspection, repair and replacement work. Shutdowns are expected to be less than 24 hours for each occurrence. If shutdowns are planned to last longer, neighbors around West Point and Discovery Park will be notified in advance of any temporary closures or planned biogas releases.

Community outreach

We will provide ongoing updates here as the project progresses.

Aerial view of the north and south digester pods at West Point.