OnSite’s Portadam team recently received an emergency call late on a Friday night. The client’s penstock valve at Willen Lake Reservoir, near Milton Keynes had jammed open during its routine annual maintenance check.

The Project
OnSite mobilised one of its Portadam teams immediately. They arrived on site at 7.30 the following morning – just nine hours after the initial call.
Once the situation had been assessed and the issues discussed with the client, a plan of action to temporarily stem the flow going through the open penstock was agreed. This enabled the Portadam installation to commence, creating a safe, dry working area around the failed valve.
The OnSite team slowed the flow down with the assistance of the client and their operational site team. The lake bed was then checked to establish Portadam support frame requirements.
The bed of Willen Lake, which had once been a gravel pit, proved to be exceptionally uneven. However, this was not an issue for Portadam which is highly versatile and flexible. Despite being a relatively small dam, the frame structure installation for this project utilised the full range of 1.5, 2 and 2.5 metre support frames.

The portability of Portadam enabled installation to be carried
out rapidly, without damaging the uneven lake bed and
without the need for special tools, or heavy machinery.
With the temporary dam in place, the contained area was

The Portadam System
OnSite’s innovative, fully-proven Portadam temporary
damming solution quickly and cost-effectively creates
safe, dry working areas in existing bodies of water,
without impacting riverbeds and without the need for
heavy plant, damaging excavation, or costly piling.
Temporary damming is an ideal solution for construction,
inspection and maintenance work in bodies of standing
water and a variety of watercourses. Portadam has also
been used extensively to create short term, large volume
water storage and containment.
OnSite’s lightweight modular system is rapidly constructed
by hand without special tools; with large dams capable of
supporting up to 2.5 metres of water often delivered in
less than a day. The light construction also means that
installation can be achieved well away from vehicular
access where necessary.

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