Dam Wall Maintenance

ENVIROKONSULT™ assists resource managers and owners of dams

with their Dam Safety Inspections by providing a Dam Safety Environmental Monitoring Service in and around earthen dam wall structures.

Regulations in terms of the National Water Act (Act 36 of 1998) require that the owner of a dam follow safe and acceptable practices in respect of the operation and maintenance of his dam.  These regulations also require that the Director General of the Department of Water Affairs should at stipulated intervals be furnished with technical information in respect of the standards applied in operation and maintenance and the condition of the dam.  To comply with the regulations, it is required that the designated engineer in charge issues Dam Safety Inspection Reports on a regular prescribed basis.

Currently there exist a number of environmental issues relating to the integrity of earthen dam wall structures.  These include inter alia the following:

  • Termite infestations:
    Termites are destructive insects which can destroy the vegetation cover which protects the earthen dam wall against erosion.  Routine inspection of dam walls for the presence of termites is crucial in the maintenance programme of any earthen dam wall.
  • Erosion:
    Dam walls should be inspected on a regular basis to detect and address early stages of erosion.  The evaluation of the Vegetation Cover Density (VCD) of an earthen dam wall is important to evaluate the erosion potential of the structure.
  • Invasive brush and tree growth:
    Dam walls should be free from any brush and tree growth as roots have a negative impact on the integrity of the structure.
  • Aquatic vegetation management:
    Build up of aquatic vegetation against and in dam wall and water abstraction structures should be avoided and target vegetation must be controlled before nuisance conditions occur.

The aims of the Dam Safety Environmental Monitoring Service are to:

  • Assist the engineer in the reporting on the condition of dam wall structures as far as its environmental condition is concerned by producing regular reports on the environmental condition of the dam wall structure, which can be added as an addendum to the Dam Safety Inspection Report.
  • Identify problem areas that need to be rectified.
  • In addition, issue the dam owner with site-specific restoration proposals and quotations for the necessary remedial actions.

Services rendered by ENVIROKONSULT™

Routine Monitoring Programme:

The basis of the Dam Wall Maintenance Programme is a routine monitoring programme evaluating the following variables on a set frequency:

  • Termite activity – installation and monitoring of termite monitoring stations in the dam wall structure.
  • Destructive animal activity – monitoring of activity of mammals feeding on termites.
  • Determination of Vegetative Cover Density on dam wall structure.
  • Degree of Terrestrial Weed Infestation on dam wall structure.
  • Degree of Aquatic Vegetation Infestation – as far as dam wall structures and water abstraction structures are endangered by biomass on or underneath the water surface.
  • Determination of Intrusive Tree and Brush Infestation.
  • Presence and Degree of Erosion on dam wall structure.
  • Downstream River Monitoring for possible seepage contamination in outlet water by pesticides and herbicides applied in termite and weed management on the dam wall structure or upstream.
  • Degree of In-lake Reed Encroachment – the uncontrolled proliferation of reeds in the dam basin leads to loss of capacity, increased sedimentation and increased water loss via evapo-transpiration. One hectare of water surface covered by reeds could result in an up to tenfold higher water loss via active evapo-transpiration, as one hectare of open water loss via passive evaporation.  Water loss as a result of evaporation is miscalculated as the much higher loss via reed evapo-transpiration is not accommodated in the water loss formulas.

Dam Wall Maintenance Services provided:

A good maintenance programme will protect a dam against deterioration; prolong its life, and greatly reduce the chance of failure.  Nearly all the components of a dam and its materials are susceptible to damage and deterioration, if not well maintained.  Moreover, the cost of a proper maintenance programme is small compared to the cost of major repairs.  ENVIROKONSULT provide the following restoration services for earthen dam wall maintenance:

  • Routine earthen dam wall inspections;
  • Control of termites;
  • Control burrowing animals and fill animal burrows;
  • Restore and reseed eroded areas and gullies (including hydro-seeding);
  • Controlling terrestrial vegetation on dam wall;
  • Controlling and repairing animal damage;
  • Controlling reed encroachment in dam basin; and
  • Controlling aquatic vegetation in dam.

Regular Reporting:

As far as reporting is concerned, the following deliverables are applicable to this service:

  • Biannual Status Report on the Environmental Condition of Earthen Dam Wall Structures of Reservoirs.
  • Annual Environmental Dam Safety Report for inclusion in the Dam Safety Report.

Professional supervision:

A professional environmental scientist who is also licensed as a PCO (Pest Control Operator) will manage the monitoring programme.  All remedial work will be under the direct supervision of a qualified PCO that will report to a professional environmental scientist.  Audits will be done on a regular basis.  Both reports will be produced and signed off by the programme manager.