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Bureau of Reclamation
Quagga Mussel Remotely Operated Vehicle Inspection
Video Transcript

Between January 23 and February 13, 2007, Reclamation divers used an underwater camera on a remotely operated vehicle or "ROV" to inspect selected facilities at Hoover, Davis, Parker, and Headgate Rock Dams for quagga mussels. 

This brief video gives you an overview of what these inspections found at these facilities. 

The mussels are small; we estimate most of them to be about the size of a fingernail, so we’ve pointed them out in the video.  You’ll also see substantial algae on these underwater structures.  You will also note in the lower left-hand corner of the visual, information is shown about the water depth and water temperature at each site. 

Hoover Dam – Nevada Intake Tower ROV Inspection, January 23, 2007

This tower was inspected to a depth of eighty feet.  Mussels were sighted sporadically on trash rack bars between thirty and eighty feet. Because there was water flow at most of the sites, there was some movement of the ROV camera as it was buffeted by moving water. 

At Hoover Dam, the Arizona intake tower – east tower or lakeside tower – was inspected for mussels.  Two trash racks were inspected on the tower – one directly under the walkway, and the second directly opposite the walkway facing the lake. 

Intake Tower ROV Inspection – Arizona Intake Structure Trash Rack,
Northernmost portion opposite the walkway – February 13, 2007

The greatest density of mussels was found on the lakeside trash rack between thirty and seventy feet, with approximately five mussels in every twenty-four inches of trash rack.  We estimate that there are a couple thousand mussels on the rack.  The first mussel appeared at a depth of approximately twenty feet.  The deepest mussel was found on the lakeside trash rack at a depth of one hundred and fifty feet. 

Intake Tower ROV Inspection – Arizona Intake Structure Trash Rack,
Under the walkway – February 13, 2007

On the riverside trash rack, the greatest density of mussels was at approximately fifty feet – about one mussel per bar.  The deepest mussel was observed at one hundred and fifty-two feet on the concrete wall. 

Fewer mussels on this rack were observed. 

Davis Dam ROV Inspection – Fresh Water Intake – February 7, 2007

Units number one and three trash rack bars, and the fresh water intake upstream of unit one were inspected for mussels. Mussels were only found near the fresh water intake up-stream of unit one at seventy-six feet.  Two mussels were located in this area – one to the lower right of the intake screen and the other off to the left. 

No mussels were found attached to the intake gate. 

Parker Dam ROV Inspection – Stoney Gates #1 and #2 – February 8, 2007

Spillway regulation gates – Stoney Gates 1 and 2 – were inspected at Parker Dam. An attempt was made to inspect the trash rack bar but was called off due to high flows.  Mussels were found on both Gates 1 and 2 between thirty-three and ninety-one feet.  Mussels were observed wedged into cracks on concrete below Gate 2 at fifty-nine feet. A total of eight mussels were observed on both gates. 

Headgate Rock Dam ROV Inspection – Spillway Gates #6 and #7 – February 9, 2007

At Headgate Rock Dam, Spillway Gates 6 and 7 on the upstream side were inspected to a maximum depth of twenty-seven feet.  On the downstream side, Spillway Gates 5 and 6 were inspected in the maximum depth was fifty-three feet.  No mussels were found.

-- Transcript ends --

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Updated: March 2009