Project Description:

The purpose of the B Basin Sewer Rehabilitation project was to upgrade and rehabilitate aging pipes and maintenance hole covers. Cracked sewer pipes and laterals allow outside rainwater and groundwater to flow into the sewer system. Faulty maintenance hole covers also allow outside water into the system. Improvements are needed to ensure proper operation, repair leaks to meet regulatory requirements, and prevent high flows that can result in sewer overflows.

A condition assessment was the first step toward finding cost-effective and technically-feasible fixes to minimize inflow and infiltration (I/I). Closed-Circuit Television (CCTV) studies were conducted using a remote-controlled camera. The information was analyzed to identify problem areas in the collection system and to design spot repairs without the expensive guesswork associated with digging blind.

The two types of repairs this project were:

• Gravity Sewer System – Spot and Segment repairs
• Maintenance Holes – Repairs and replacements

Gravity Sewer Spot Repairs and Replacement

Gravity mains offer reliable movement of sewage and surface runoff through a sewer system. However, over time the ground can shift, roots can penetrate, and traffic can impact sewers causing them to settle and crack. During this project, contractors spot repaired damaged or displaced existing 6-inch, 8-inch, 10-inch and 12-inch gravity sanitary sewer pipe with new polyvinyl chloride (PVC) sewer pipe throughout B Basin.

Maintenance Hole Repair and Replacement

Maintenance holes need to be easily accessible for sewer maintenance and related emergencies. Over time, maintenance holes can become covered with grass or can sink below the grade level of lawns, roads, or sidewalks. Common rehabilitation methods used for projects such as this include:

1. Replacing the frame and cover;
2. Applying cement mortar as a binding agent to the inside; and
3. Applying epoxy liner to the inside for resurfacing.