Routine water column monitoring is typically performed between April and October, and consists of the collection of water samples from the Main Street Bridge in Massena and several locations in the lower Grasse River (see map below). Water samples collected at each location are submitted to a laboratory for measurement of PCBs and total suspended solids. In addition, water quality information such as water temperature, specific conductivity, pH, dissolved oxygen content and turbidity is recorded. This information is used to understand variations in PCB levels and water quality that are associated with location, season, flow, temperature and other environmental factors. These data also allow for the assessment of longer-term changes in water quality over time (see Environmental Monitoring Results). Over 2,300 water column samples have been collected as part of this monitoring program to support the design, remediation, and long-term monitoring of the project. Routine water column monitoring was discontinued in 2016 due to the start of construction in 2017.