Imperial Dam maintenance crews reported finding quagga mussels on an individual basis -- one or two in the settling basins and in other locations -- in late June. Less than three weeks later, adult quagga mussels began appearing on the trash racks at Imperial Dam and at Senator Wash pump/generating plant. So far, the number of quaggas is minimal, but Reclamation and Imperial Irrigation District staff are moving forward with plans to address the issue.

A Reclamation in-house task force in Yuma is reviewing and inspecting systems from Imperial Dam downstream to Yuma and into Mexico, as well as Wellton Mohawk facilities to identify the facilities' potential exposure to quaggas and impacts the mussels may have on operations. System components that have been identified as high risk include:

• water measurement devices (example: bubblers used to measure water surface elevations),
• Senator Wash pump/generator cooling system, and
• Imperial Dam/Senator Wash trash racks.

In late July, Reclamation drilled two groundwater wells -- a primary and a back-up -- adjacent to the Senator Wash pump/generator building that will be used to supply quagga-free cooling water to the units. We are also collaborating with IID maintenance personnel to develop a dive schedule to video quagga mussel activity on the trash racks and measuring devices.

Reclamation's Yuma Area Office is planning a workshop where member water districts of the Imperial Dam Advisory Board and other interested entities can exchange collective quagga mussel information/experience, and join in analyzing Yuma area water systems in terms of exposure and impact.