LETTERS: Heath Dams – Questions!

Published: 6 February 2014

• DR Andy Hughes (January 30) declares there is no conflict of interest.

He says: “The Institute of Civil Engineers has a professional ethics committee and I could be disbarred if they found otherwise”.

That may well be so but as, one by one, the institutions of power are seen to be failing the test of public scrutiny, who is the public to trust to protect the wider interest in a matter such as this?

Dr Hughes says “Every dam owner employs a panel engineer. Once you write a report for them, your role is finished”.

The problem is that his role is not finished, as you point out.

Dr. Hughes says he “can be challenged at any time on my results” and that “The owner can go to any company to do the work, or to another engineer to act as a referee to check your findings.”

Then why does the City’s public consultation state: “We will not be able to act on comments that challenge the need for the work to be done.”?

Dr Hughes asserts that the calculations of the risk of flooding on the Heath were based on estimates that measure the consequences of a dam bursting against its likelihood.

That is exactly what has not been done, except in a deeply-flawed Quantitative Risk Assessment drawn up after the proposals were prepared.

They have refused to answer any questions on it. It is just one of many concerning elements of the Atkins proposals.

The City did commission peer reviews from other highly respected dam engineering firms. AECOM Technology Corporation challenged many aspects of Atkins’s proposals but, like the questions raised by local “stakeholder” groups whose members include engineers, they have gone unanswered.

For example, the bird sanctuary and mixed pond dams are claimed by Atkins to be the second and third most vulnerable to collapse from overtopping; but AECOM concluded the exact opposite: that these are the two dams most resistant to overtopping failure.

Both the City and Atkins have refused to explain this anomaly.

AECOM challenged Atkins’s fundamental assessment of the “Probability of Dam Failure”, saying: “The dams withstood overtopping during the 1975 flood event… the [pond] embankments may be more resistant to overtopping than research figures suggest”.

Dr Hughes claims: “We use rainfall studies by meteorologists going back hundreds of years to calculate the probability of severe storms.”

AECOM found their use of these figures inadequate: “It is extremely unusual to have location specific data for such an extreme event as the 1975 flood and we consider best use has not been made of this valuable information.”

These and many other challenges put in doubt the validity of Atkins’s designs.

Dr Hughes justifies his recommendations by reference to the Pitt Review, commissioned in response to the 2007 floods.

In fact what Pitt said about the few incidents relating to reservoirs was: “Not all of these might be regarded as significant and, in the event, none had to be treated as emergencies.”

Dr Hughes must also be well aware that the Environment Agency states categorically that: “…since 1925, there has been no loss of life due to dam disasters in the UK… the likelihood of a complete dam failure is considered to be very low. The likelihood of flooding from a reservoir is far lower than from other forms of flooding.”

So why is Hampstead Heath to be subjected to this extraordinary requirement of a one-in-400,000-year test, when the official inspection reports require only one in 10,000, and many other places seem satisfied with one in a hundred?

The engineers may be experts but they cannot be allowed to dictate what should happen on Hampstead Heath without question, especially when other, equally qualified, experts have challenged the validity of what is being proposed.

Those whose duty it is to care for the Heath should be exercising a great deal more judgment than they have shown so far.