By Scott Bryan, CAP Senior Biologist
Quagga mussels were initially found in the Colorado River in 2008 and soon thereafter, they had invaded the CAP. The immediate reaction was one of anxiety and uncertainty.
How bad would the problem get?
Would the mussels take over the system and cause extensive damage?
Would we have to change the way we operated the canal?
Almost immediately, we conducted extensive risk assessments and began an intensive monitoring program. Now, nearly 10 years later – what have we learned and what is happening with the quagga mussels?
In general, quagga mussels have not proven to be the catastrophic invaders in the CAP system that were originally feared; however, they are still having substantial impacts. We typically don’t see adult quagga attached to the concrete liner where there is a constant high flow, rather we find quagga attached to hard surfaces wherever we have irregular or slower water flow, such as check gates, turnouts and pipelines.
But these aren’t the mussels that are causing the problems.
As the initial risk assessments correctly predicted, the biggest issues occur within the critical systems of the pumping plants. Although we see relatively minor issues in many of the plants with mussels and shell debris in strainers, filtomats and fire systems, our main focus is on the cooling water system at the Mark Wilmer Pumping Plant.
CAP began experiencing severe problems in the surface air coolers at Mark Wilmer in 2014. A combination of organisms including quagga mussels, colonial hydroids, bryozoans and algae had clogged parts of one of the six, 66,000 horse-power pump units, causing it to overheat and go into forced outage (known as biofouling). The coolers were torn down, power washed and painted with a special coating that was meant to make the cleaning process easier. In 2015, three more units all experienced the same biofouling and went into forced outage, at a considerable expense to CAP.
Because of these forced outages, CAP began to look at potential solutions that would prevent settlement of these organisms and subsequent biofouling. Throughout this year, a pilot study was completed that tested the effectiveness of a chemical injection system. For this study, low dosages of copper sulfate were injected into the cooling water. During the 12 months of evaluation, there were no quagga or other organisms attached or growing in the header boxes of the treated Unit (Unit 6). At the same time, there was significant biofouling of the untreated cooling water system in Unit 5. The success of this pilot study shows promise for expanded use of the injection system in the future.
Unfortunately, quagga mussels and other invaders like colonial hydroids, are here to stay. The good news is that the quagga have not had the catastrophic impacts that were originally feared and we are finding ways to even further lessen those impacts. CAP will continue to explore various treatment options to stay on top of quagga and whatever invader comes next.