Vann Lake is a 55,000cu.m reservoir retained by an 8m high earth dam in rural Surrey.  The reservoir dates from around 1750 and is now part of a site of Special Scientific Interest (SSSI), designated for a number of features water and woodland features.

The project was implemented following recommendations in the interests of safety from a statutory inspection under Section 10 of the Reservoirs Act 1975.  The works were required to provide a spillway which would safely pass peak flows from a 1 in 150 flood event with sufficient freeboard.

We were appointed to undertake the structural design for the 25m long upgraded spillway comprising a U-trough structure with a public right of way footbridge access along the crest of the dam.  In addition to the new trough structure alterations were also made to the cascade structure to improve flow regulation in flood conditions.