Agenda item

Report of the Director of Open Spaces and Heritage.

The Cripsey Brook Flood Storage Area includes a Small Raised Reservoir maintained by the Environment Agency using Forest Land at Thornwood Common,

within Lower Forest, to site the reservoir embankment, under a licence granted by

the City Corporation in March 2000 to the Environment Agency and Epping Forest

District Council.

The reservoir embankment dams a natural basin to prevent severe flooding in

Thornwood hamlet which previously occurred in 1987 following intense thunderstorms.

The crest of the embankment is presently 75cm wide and is used as a footpath with

grass slopes on either side. The reservoir is less than 25,000 m3 and therefore is not

currently governed by the requirements of the Reservoirs Act 1975.

The Environment Agency, in this case responsible for the Cripsey Brook dam, is also the enforcement agency and it has determined on a Risk Assessment basis that all of its non-statutory reservoirs be brought up to statutory standards.

Earth embankments can withstand limited overtopping if the downstream face is not

too steep. A recent safety inspection has noted that the embankment is narrow with

steep slopes and has poor vegetation, which the inspecting engineer concludes could reduce the length of the overspill path potentially resulting early failure and has recommended increase in the width of the crest. This would also make the slopes shallower, reducing overtopping velocity and overall improve its resistance.

The Environment Agency is therefore requesting permission to increase the width of

the crest to 1.5m to bring the flood defence up to the statutory standard.

RESOLVED – that Members:

 Approve the review of the terms of the licence dated the 20 March 2000 that was granted to the Environment Agency and Epping Forest District Council to enable them to carry out works within the original licenced area to widen the Page 195

Agenda Item 18 crest of the Cripsey Brook dam to 1.5m but otherwise to retain all other remaining licence terms.

 Note that the Environment Agency is to contribute up to £2,000 towards legal costs.

 Instruct the Comptroller & City Solicitor to undertake any necessary documentation.