Overview
Ballard mobilized personnel and specialty equipment within the protected area of the Hanford Nuclear Power Plant to perform sediment removal operations at two spray ponds within the plant. Ballard performed the scope of work involved in this project twice to date. First in 2013, then again five years later in 2018, both times with the same intention to reduce the amount of sediment within the spray ponds. In 2020, the team was called out to resolve emergent work on the main cooling pump.

Scope of Work
In 2013, a five-man dive/dredge crew performed a work scope that included: training, badging, site set up, installation of diving systems, installation of twin six-inch dredging systems, daily production tracking, Quality Assurance/Quality Control (QA/QC) reporting, pre/post-dredge surveys, and demobilization. These same tasks were performed in 2018 as well, however, they were done with a seven-person dive crew and supplemented with dredge pit construction. During the 2018 completion of the project, approximately 2,037 cubic yards of material were removed from the spray pond.

In 2020, Ballard was called for emergent work to support the inspection of the main cooling pump. Upon completing the yearly maintenance on the cooling pump, Ballard was dispatched to help with a FME removal (forging material exclusion) or (the item being dropped) and outer pump casing inspection. Including, but not limited to, checking the clearance on the impellor blade to pump shroud, vibration monitoring equipment, all bolting connections, 90” expansion joint, and control rods.

Innovative Solutions
One major component of the work scope for both projects was the setup of the dredge spoils area, which included the installation of three sixty-foot by one hundred-foot geo-tubes to capture the sediment. In addition, the laying and installation of a waterproof membrane lining (geo-bags) for the entirety of the 300-foot by 300-foot dredge pit. The geo-tubes then drained into a sump where Ballard installed multiple six-inch dewatering pumps to recover water and move it to the cooling tower wet wells.

Limited visibility and concrete pylons holding the spray ring in position posed challenges for the Ballard team. Good umbilical management, constant two-way voice communication, and careful payout of the dredge hose were critical to our team’s success in mitigating these project issues.

Inside the ponds, the temperatures of the water could potentially harm the divers if they were submersed for a long period of time, so cooling the suits were required to maintain the diver’s comfortability.

Results
The work performed was integral in the maintenance of the intakes for the sprayers within the pond. If too much sediment was to make its way in front of the intake grates, the sprayers would lose functionality. All work performed both under the water, as well as on land, was done on time and safely—zero accidents or lost time events.