B Basin (West Basin) Sewer Rehabilitation
Construction estimated to begin in Fall 2023 and is estimated to complete in Fall 2024.
B Basin covers areas of San Mateo west of Highway 101, north of Highway 92 and south of 1st Avenue, including the Hayward Park, Sunnybrae, Baywood, Baywood Knolls, Aragon, and Foothill Terrace neighborhoods (see map).
The purpose of the B Basin Sewer Rehabilitation project is to upgrade and rehabilitate aging pipes and manhole covers. Cracked sewer pipes and laterals allow outside rainwater and groundwater to flow into the sewer system. Faulty manhole 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 will address are:
- Gravity Sewer System – Spot and Segment repairs
- Manholes – 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, our contractors will spot repair 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.
Manhole Repair and Replacement
Manholes need to be easily accessible for sewer maintenance and related emergencies. Over time, manholes can become covered with grass or can sink below the grade level of lawns, roads, or sidewalks. There are several methods of rehabilitating manholes, and the method selected for a job depends on the condition of the manhole. Common rehabilitation methods used for projects such as this include:
- Replacing the frame and cover;
- Applying cement mortar as a binding agent to the inside; and
- Applying epoxy liner to the inside for resurfacing.