In memory of Mr. Marian Stefanov
In 2019 during our first on-site inspection, we found many dams in poor conditions: shrubs on both faces, inadequate height, and poor waterproofing.
The government of Bulgaria decided to secure several small earth dams; they began to refurbish the dams’ bodies and install appropriate sensors for long-term monitoring.
Before and after the renovation
The purpose of the monitoring system is to observe the critical parameters and to send warning messages in case of anomalies exceeding thresholds.
The reservoir water level is the most common measurement and is often a regulatory requirement. Uplift pressures are directly related to the headwater level. The water in the reservoir and downstream (absent or negligible in these dams) influences the seepage; changes unrelated to the water level can be an indication of potential problems. The environment in which a dam is built affects its performance, so hydrological and meteorological data must be used to support any safety activities.
To measure the pore water pressure and estimate the seepage, we installed two, four, or six piezometers in each dam. The piezometers respond only to the pressure of the groundwater around them and this is extremely important in earth dams because it allows monitoring of the long-term seepage pattern.
Piezometer and non-woven fabric bag with sand and gravel
We designed a special water level indicator to facilitate the installation procedure and to offer a durable device for accurate measurements.
Pressure probe inside a Casagrande filter anchored to a metallic cubic structure
We proposed a simple but fairly complete weather station with a rainfall gauge, air temperature, atmospheric pressure, and wind direction and velocity.
Weather station with photovoltaic panel
Furthermore, we decided to monitor the stability of the dams using a new in-place inclinometer chain consisting of six to ten bi-axial MEMs probes.
GeoString on the soil during installation
In total, six dams have been instrumented with variations of this system and others will follow in the future.