TECHNIQUE

Pond Construction - Concrete (Managing Wetlands for Wildlife - Implementing Management Plan)

Summary Information
Type of technique Health & Management / Managing Wetlands for Wildlife / Implementing Management Plan / Techniques:
Synonyms and Keywords --
Description
  • The area to be developed into a pond must be excavated to the required shape and depth, allowing for the loss of depth with the thickness of concrete.
  • The excavated area should be made firm before the concrete is poured, to reduce stresses on the concrete, and the addition of a layer of hardcore rammed into the base may be advantageous.
  • A layer of concrete (cement, sand and aggregate in a 1:2:4 mixture) at least four to six inches thick must be laid down.
  • Metal may be incorporated as reinforcement. A layer of wire netting may be used under the concrete to act as reinforcement and help hold the fresh concrete in place on sloping surfaces.
  • Finish with a facing layer of cement containing a waterproofing compound, or with a pond sealer.
  • Plastic sheeting may also be used as a layer between the rough concrete and finishing cement to reduce the risk of water leakage from cracks. This may be moulded to uneven surfaces, should be brought up to the rim level of the pond and well-hidden by the edging concrete or stones to avoid damage by waterfowl.
  • A drain may be incorporated into the bottom of or low on one side of a concrete pond during construction.
  • Sides should be gradually sloping to allow easy exit from the pond.
  • A ledge may be constructed a short distance below the waterline and filled with earth, for planting marginal species.
  • Finish with a wide margin at ground level or a border of paving or aggregate.
Appropriate Use (?)
  • Concrete may be mixed at the site required.
  • Theoretically may be constructed to any shape required.
  • May be constructed in any size.
  • Long-lasting.
Notes
  • The hardest setting is achieved if drying is slow; the use of wet sacking to reduce drying speed may be useful in hot dry weather.
  • Join between base and sides may be sealed with bonding/sealing compounds if the sides are constructed several days after the base.
Complications / Limitations / Risk
  • Not easy to contour .
  • Fresh concrete is toxic. New concrete should be washed, filled and emptied several times and/or left to weather for several weeks with water in before introducing the birds.
  • Cracks are likely to develop , for example if the underlying ground subsides, and are frequently difficult to locate, being covered by mud or sediment.
  • Erosion is likely at the concrete-soil junction unless a border of at least waterfowl neck length is incorporated.
Equipment / Chemicals required and Suppliers
  • Cement mixer.
  • Cement, sand and aggregate.
  • Waterproofing compound.
  • Reinforcing materials for larger areas.
Expertise level / Ease of Use
  • Construction experience required except for small ponds.
  • Considerable amount of labour required.
  • Expert advice is suggested regarding e.g. concrete mix, reinforcement required and any sealants.
Cost / Availability Relatively inexpensive.
Legal and Ethical Considerations  
Author Debra Bourne
Referee  
References B40, B41, B93, B95, B97, B108, B139

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