Devon IS safe from dam collapse

They've been inspected following the Whaley Bridge collapse in Derbyshire.

Questions were asked at last Thursday’s Devon County Council about the safety of Devon’s dams following the substantial damage caused to the Toddbrook Reservoir dam at Whaley Bridge over the summer.

Thousands of people were evacuated from their homes and engineers desperately worked to prevent the dam from catastrophically collapsing.

Cllr Gordon Hook asked for an assurance to be given that Devon’s dams are safe and that their safety is checked on a regular basis by qualified engineers.

He also asked if any concerns had been raised by inspections and what remedial action had been taken, if inspections for the dams had taken place since the Whaley Bridge incident, and that can Newton Abbot residents be assured that there is no risk to them and their homes from the Holbeam Dam?

In response, Cllr Roger Croad, cabinet member for the environment, confirmed that the Environment Agency has completed additional in-house inspections for all the dam sites that it owns, operates and maintains and has confirmed that all three of its dams in Devon are in a safe and satisfactory condition, as have South West Water.

All registered high-risk dams are inspected once every 10 years by an All Reservoirs Panel Engineer and one a year by a Supervising Engineer.

In Devon there are 35 registered high-risk dams, with 23 of these owned and maintained by South West Water, three by the Environment Agency, including the Holbeam Dam, and one by Devon County Council at Stover Park Lake. The remaining eight are privately owned.

He added: “It should be noted, however, that this does not mean that they could not overtop. Each site is designed to store flows in a flood event and to release water at a controlled rate to reduce the risk of flooding downstream.

“In an extreme event, the capacity of the attenuation area upstream may become fully utilised, in which case the dam will overtop. Exceeding the capacity of the storage reservoir should not be mistaken for failure of the dam.”

Cllr Croad said that back in 2012, one of the dams maintained by the Environment Agency at Harbertonford was subject to overtopping during floods. The downstream spillway face was badly eroded during these flood events and the operation of the control gates was compromised.

He said that an inspection was carried out later that year with recommendations being made and implemented over the subsequent years, including the reconstruction of the spillway with armouring to reduce the risk of any future erosion.

In reference to the Holbeam Dam at Ogwell that protects Newton Abbot from the River Lemon, Cllr Croad said that the most recent Section 10 inspection of Holbeam Dam was completed on March 21, 2019.

He said that in this year’s inspection, there were several measures that needed to be taken in the interests of safety, but these were all further improvements in line with current best practice and are not as a result of any defects.

The recommendations included improvements to monitoring, telemetry and weather and vandal proofing and the Environment Agency has been tasked with completing these items in the next three years and has sought the necessary funding to do so.

Cllr Croad added: “The Environment Agency has confirmed that Newton Abbot residents can be assured that there is no risk to them or their homes for any flood event within the design criteria. It is currently believed that the dam provides protection from all events up to about a 1 in 50-year event, which is quantified as an event with a two per cent probability of occurrence within any one year.”

Cllr Hook said that he was reassured by the response as he definitely did not want to see anything like the threat that there was to Whaley Bridge happening in Devon.