Chain Wall Installation at Wastewater Treatment Plant
CommTank’s service team performed a new type of fuel storage tank installation for the Town of Hull, Massachusetts. People in the waste water treatment plant leadership were concerned about protecting the backup generator system from rising sea levels and coastal flooding. This prompted them to replace an underground storage tank that was 40 years old with an aboveground storage tank mounted on a chain wall. A chain wall is an elevated foundation that helps to keep structures above flood level. The chain wall is also known as a stem-wall foundation and was purchased as a pre-cast concrete form. In 2013, the plant property had seen an abnormally high amount of water enter the basement which ultimately resulted in taking the treatment plant off-line. One of the planned system upgrades was the town hiring CommTank to install the new flood resistant system. The scope of the project included temporary tank provision, fuel filtering, excavation, UST cleaning and removal, installation of chainwall and AST, upgraded piping between the AST and day tank, upgrades to day tank and addition of overflow tank.
This video shows the installation of the chainwall and tank.
Chain Wall Installation Project Details
The CommTank team started the project by installing a temporary 3,000-gallon aboveground storage tank (AST). The temp tank was installed to provide fuel while the underground storage tank (UST) was being replaced with a permanent above ground tank. More piping was installed and insulated. Fuel was filtered and transferred from the UST to the AST. When the fuel transfer was complete, the UST was entered and cleaned. CommTank crews excavated and exposed the UST. The UST, ground water monitoring well, vent, fill port and the pad at grade were removed and properly disposed of.
The project required the soil compaction of the excavation and testing by a geotechnical technician. When soil compaction levels were confirmed, CommTank crews placed 2” of crushed stone on top of the fill. The compaction of the backfill material was very important. This area was the planned site of the permanent aboveground fuel storage tank and its associated slab. Crane use helped to install the double-wall Fireguard aboveground tank on to the chain wall and crews secured it with steel straps to concrete anchors.
CommTank crews installed supply piping from the new Fireguard tank to the existing 100-gallon day tank. We also installed a new overflow tank that included a pump. The overflow tank was needed because the day tank did not have a return pump. It was required because the level of the underground tank was below the day tank. Since the new Fireguard tank sits higher than the day tank, an overflow tank will now pump any fuel not used by the generator to the Fireguard tank. All external piping was primed, painted and covered with fiberglass insulation. The 100-gallon day tank was cleaned, inspected and tested before being placed back in service. Fuel from temporary tank was transferred into the 3,000-gallon AST and the generator maintenance vendor tested the system at startup.