Cotswolds

New Clay Lined Parkland Lake Construction

Designed primarily for long-distance swimming by the owner, this three-and-a-half-acre clay-lined new lake enhances views from the Georgian house across the parkland and to the farmland beyond.

The Brief

  • Design and build a new lake suitable for long distance swimming.
  • Visible from multiple rooms within the home.
  • Sit naturally within the heritage-rich parkland.

Before

After

Surveys

Following excavation of test holes across the site and subsequent permeability testing of the underlying clay subsoil, it was determined there was sufficient suitable clay across the working area to create a 1m thick puddled liner (the correct depth to ensure its integrity and longevity).

The lake was designed to have a minimum water depth of 1.8m along the swim line, extending to 3m in the wider sections to create a natural ‘cold core’. This not only helps combat algal growth and reduces evaporation, but also increases dissolved oxygen ­- which is required to maintain a healthy, balanced aquatic ecosystem.

The survey data enabled the production of detailed design drawings to support the planning application. The lake water level was determined by a prominent oak tree; to maintain the level of the ground around it. As part of the design process, the lake was digitally 3D modelled and the earthwork quantities balanced to ensure all excavated soil could be re-incorporated on-site before the project began.
The design stage also considered water supply; via a pipe taken from a new weir constructed across the adjacent brook (to replace an existing derelict structure). To reduce maintenance and potential contamination of the lake, water passes through a meandering silt settlement pond and a network of water control valves before entering the lake.

Earthworks

The lake was constructed in two phases to allow one half to fill over the winter months, and then the second phase constructed the following summer.
Topsoil strip
Subsoil excavation
(Left) 1st phase complete (Right) 2nd phase in construction complete
Subsoil excavation: Lake excavation using GPS enabled diggers and bulldozers ensured a high level of accuracy.

Clay Puddled Liner
Surplus good quality excavated clay is stockpiled for later re-use in areas where clay is not up-to-standard.
The finished lake design has been over excavated by 1m depth on the base and sides. Low permeability clay is then placed in 200mm layers, wetted with a water bowser and then compacted with a pad foot roller to return the lake to design contours. This process breaks up the natural stratification of the clay and binds it back together forming the 1m puddled clay liner.
(Left) Puddled clay Compacted clay with pad foot roller. (Right) Existing clay, not yet excavated, showing the naturally occurring horizontal layers that can cause leaks.
Birds eye view of puddled lake base.
Pad foot roller in the foreground, tractor and water bowser in the background
Clay from the stockpile being shaped and puddled
(Left) 1st phase (Middle) Stockpile of Low permeability clay excavated in 1st phase, for use in puddling of 2nd phase. (Right) 2nd phase

Jetty Construction
Green oak timber jetty constructed over cast in-situ concrete footings. Swim ladder on the front of the jetty to provide direct access to 3m water depth.
New weir to divert water flow from the stream to the lake.
Stream / Meandering pond to create a silt trap for before water enters the lake.
(Left) 2nd phase in construction. (Middle) 1st phase complete. (Right) Stream water supply and silt trap pond
2nd phase nearing completion
Topsoil replacement prior to cultivation and wildflower seeding