Dams and their ancillary features are exposed to environmental conditions such as surface runoff, highly concentrated spillway and channel flow, subsurface flow of water, freeze-thaw cycles, vegetation growth, and wind and wave action.
The properties and performance of earth, rock, concrete, and other materials used to construct dams change over time as a result of exposure. The result can be seen or unseen damage such as cracking and spalling of concrete; settlement and surface erosion of embankments and foundations; hydro-fracturing and subsurface erosion within the dam; and deterioration of riprap and/or corrugated metal conduits. Therefore, it is important to regularly monitor the condition and performance of dams to identify deficiencies and changing conditions. This is best accomplished through the involvement of both the consulting dam engineer and the owner's representative.
Prior to a first inspection, it is recommended that the dam engineer thoroughly review available background information on the design and construction of the dam, subsequent modifications, operation and maintenance activities, performance monitoring data, and prior inspections and analyses. This information review is helpful in identifying significant features or conditions critical to the proper performance of the facility or otherwise meriting close inspection, and will earmark unique features that need to be specifically addressed during the inspection.
Dam inspections generally consist of a visual assessment of the project structures to note:
- Deterioration, movement or instability
- Animal burrows
- Erosion or scour
- Excess seepage
- Maintenance of vegetated areas
- Condition of mechanical works
- Operating condition of instrumentation and monitoring devices
- Condition and performance concerns related to intakes, conduits,
- spillways and channels
- Condition of items specifically noted during the background information review
Many clients request that inspection guidelines be developed for their project(s) to allow effective self-inspection of dam facilities between independent inspections. Schnabel's dam engineers have developed numerous operation, maintenance, and inspection manuals to assist owners. Guidance materials typically include a plan sketch of the facilities to index observations, a checklist of key elements to be inspected, and a response priority for noted observations. Formal training can also be provided to the dam owner's engineering and/or operations personnel.