The fish pass was flowing tonight at just below the designed capacity of 0.5 cubic metres per second. The extension was completed and apart from a bit of rock armour required at the top side, I think it looks sound and should hold up to the force of the spates that will hit it. I am concerned about the long shallow raceway into the pass (or out of it when fish are moving upstream) but with water levels so low, it is difficult to judge how this will perform in higher flows. Ideally it should be passible at all flows so perhaps a small modification or two may help. There remains a problem just upstream of the bypass intake but will discuss this again with CCT to see if they have a solution yet? I feel a small concrete cross wall may solve this without impacting on fish movements but we will need to look at all the options. This would add depth to the upper extension and that should help. We still have concerns about the security issues that we have raised repeatedly, both from a poaching and a risk perspective.
The contractors poured another slab of mortar the other day and plan another on Friday if it stays dry. I suspect tomorrows predicted rain may prevent this but we will have to see. Although I’m desperate to see the river in spate to allow fish to move again, I slightly torn as I’d also like to see the works completed and the contractors off site. Time will tell and there’s nothing we can do about it.
I live in Dublin, Ireland and have a keen interest in our local river. I have a background in forestry and recently the local council have said they have plans to install fish pass on 7 weirs along the river Dodder in South Dublin. I was wondering are these structures very expensive are there companies that specialize in building them.
I can confirm that constructing new fish passes can be extremely expensive. There are plenty of specialist out there that can do this work but the key element is design. Unless the design is correct, there can be an awful lot of money wasted. If you need more information, please give me a call or send an email. Thanks