A full land and water survey is conducted throughout the farm estate. We then take into account the types of crops being grown, and determine from the soil types how much water will be required for each crop in a dry summer. A calculation of the total required water volume is then made in preparation for an abstraction licence application to the environment agency to fill the reservoir during winter months.
A water abstraction licence can then be applied for based on the total crop requirements, if there is no exisitng water supply to fill the reservoir. AJ Freezer can make an application on your behalf to ensure all the necessary information is provided correctly to the EA.
If an abstraction licence application is successful a location is then proposed for the reservoir taking into account proximity to fields to be irrigated and site geography (lay of the land) and agreed with land owner.
Trial pit excavations are then carried out on the agreed site by digging test pits to a depth of 5 metres. This allows soil engineers to assess the substrata ground conditions and water table for suitability for use in the reservoir construction.
A full topographical survey of the site is carried out.
We arrange for the qualified specialist surveyor to conduct a land level survey of the proposed site.
The design of the reservoir begins. The design takes into account the surveyed field levels, total irrigation water volume requirements for the crops, the site location and shape plus any other factors identified in the trial pit excavations. A full A1 scaled reservoir design is then plotted with all dimensions, depths and volumes of soil to be excavated being calculated.
A planning application is submitted to the Planning Department of the local District Council.
We are experienced with reservoir applications and understand the complex nature of such large earthworks and the impact they can have on local environments. We let experience guide this application and are aware of criteria which needs to be met in order for the planning application to be successful.
If planning application is successful we move to Stage 8…
Tender documents are drawn up with bill of quantities and all relevant details for the construction and are then sent out to suitable contractors for pricing.
The successful tender is chosen based on experience, price and reliability to complete the project. A date is then set to begin groundworks. In order to schedule the best use of early summer weather, this is usually around early spring. The installation of the reservoir liner is time critical and should take place before the strong summer heat begins (early summer or late autumn are the best times for liner installation to prevent liner expansion on hot days).
Construction of reservoir begins – this will generally take 2 to 3 months depending on weather conditions.
AJ Freezer would oversee and supervise the total project from start to completion acting as ‘Engineer to the Project’ to ensure correct construction works and lining are to the required standards.
Construction takes place as follows:
Digging – All topsoil is stripped from the reservoir area, sub-soil is dug out and placed to form the high embankments of the reservoir. Generally, for every 1 metre dug down, the excavated spoil is placed and compacted 1 metre high to form the embankments. This is known as a ‘balanced, cut and fill’ design and is the most efficient construction method of a reservoir.
Underlay – a soft textile layer is installed on the inside walls of the completed reservoir embankments.
Lining – a long life liner membrane is placed on top of the textile. Sections of membrane are ‘welded’ together to form a complete sealed liner (this is when fine weather is required)
Associated filling pipework – underground mains are installed from the abstraction point (river, borehole) to the reservoir. Reservoir abstraction pipes, pumps and pump house are all designed and supplied by AJ Freezer – see our Pumps page.
Filling – Filling takes place over the winter abstraction period (as outlined by the Environment Agency) and in accordance with the issued abstraction licence.
For reservoirs storing over 5 million gallons above the lowest natural ground level around the outside of the reservoir, the project has to be overseen by a Government appointed Panel Engineer. AJ Freezer would then act as ‘Engineer to the Contract’ in these instances, carrying out daily inspections and informing the Panel Engineer of any issues or concerns with construction works or soil changes.
For reservoirs on a flat site, 10 million gallons is the maximum limit which can be stored using the balanced cut and fill design without the requirement of appointing a Panel Engineer.
All reservoirs are logged with the Environment Agency register and have an annual inspection by an independent qualified inspecting engineer. AJ Freezer can organise this and provide the inspector with information and details of the reservoir for him to evaluate.