Construction Management Services for Main West Tank

The City of Paso Robles needed to update the 21st Street Reservoir—an unconventionally-shaped, earthen reservoir lined with gunite and HDPE. The reservoir was covered with a wood roof and truss system supported by a concrete stem wall at the perimeter of the tank and interior columns. Constructed in 1925, it had reached the end of its useful service life.

The City decided to replace the reservoir with a new, 4.0 MG, partially buried, pre-stressed, AWWA D110 Type I concrete tank. The new reservoir was named the Main West Tank to accurately portray its function as the main facility providing storage for the City’s Main West pressure zone (one of the City’s two main pressure zones).

The City selected Cannon to provide construction management services and assist in the implementation of the project. Services under this contract included construction management; construction observation; and materials engineering, sampling, and testing.

The new Main West Tank was constructed at the existing reservoir site and maintained the existing hydraulic grade line for the Main West pressure. The construction work consisted of demolition; construction of the partially buried, 4 MG concrete tank; and appurtenances such as ladders, hatches, railing, air vent, safety equipment and various SCADA and electrical equipment.

Pipeline installation work included the following:

• 18-inch cement-mortar lined and coated welded steel pressurized potable pipe;
• 18-inch and 12-inch stainless steel inlet manifold piping;
• 18-inch ductile iron (DIP) pressurized potable pipe;
• 24-inch polypropylene drainpipe;
• 4-inch, 6-inch, 8-inch, 10-inch, and 12-inch DIP pressure pipe; and
• 4-inch, 6-inch, and 8-inch polyvinyl chloride drainpipe beneath the tank.

As a result, the Main West Tank serves as a complete and functioning potable water storage