Impoundment & Reservoir Assessment
Earthen impoundments are used as an engineered containment structures for smaller water reservoirs or storage ponds for municipal or recreational use. The risks associated with potential failure of these types of engineered structures become much higher given that they are typically located closer to populated areas. Therefore it is imperative to ensure the continued stability of earthen impoundments through thorough investigations and risk mitigation.
Uncontrolled seepage through earthen impoundment can lead to decreased stability by way of increased pore water pressure, the transport of finer-grained materials, and piping. Sometimes visual inspections can identify problem areas if the uncontrolled seepage is coming out of the impoundment or if seepage has formed sand boils due to the high water pressures, but there is not always visual evidence on the ground. A geophysical investigation can provide greater insight into known issues within the impoundment, or provide the basis for evaluation when there are no known problems.
The risk for earthen impoundments is that they are typically located near populated areas. HGI can help minimize risk from these structures through geophysical investigations. The information we offer can be used to find small issues early before they become big issues.
HGI has the experience to offer cost-effective geophysical investigations of earthen impoundments. After an initial assessment of the situation, the appropriate geophysical method or group of methods can be identified to provide the proper guidance to safely manage any potential problems, or simply the necessary information to evaluate and monitor the impoundment. All of our methods are non-invasive and safe for both the structure and any personnel.
The electrical resistivity and seismic methods are well-suited for earthen impoundment investigations, given that they are both highly sensitive to detecting the types of contrasts (electrical and structural) associated with seepage and erosion. In particular, low seismic velocity (with seismic methods) and/or high conductivity (with electrical resistivity methods) anomalies can be indicative of deteriorated materials or fluid infiltration. These methods are deployed similarly, using an array of sensors placed in a line along the ground surface and cabling to relay measurements back to a field computer. Electrical resistivity mapping uses a small current injected into the ground to measure the electrical resistance, or resistivity, of the subsurface. Seismic methods instead uses an acoustic source, such as a metal plate struck by a sledgehammer, to measure the movement of sound waves through the subsurface. Data are compiled and modeled to present as cross-sectional profiles that can provide actionable information for mitigation or the assurance that an earthen impoundment’s structural integrity is sound.