Elevation (Manometer) Surveys
Pezonella Associates, Inc. performs elevation surveys of constructed environments such as finished interior spaces and concrete slabs. These surveys assess elevation differences at locations throughout the survey space with respect to a chosen datum (reference location) within or near the survey space. Because the device used to measure elevation differences is known as a manometer, these surveys are often called “manometer surveys.” Manometer surveys are commonly performed for—but are not limited to—the following reasons:
- To determine the likelihood that indications of potential distress (e.g., cracking in floors or walls) have occurred or are occurring due to differential movement of the supporting material beneath the area of interest. In such a scenario, identifiable trends of elevation change over particular distances within the sample space would be expected.
- To determine if and to what degree suspected areas of differential movement within an area of interest are changing over time. This would be determined by conducting successive sampling events of an area of interest at regular intervals and comparing the resulting elevations.
- To determine if a newly-constructed floor or paved area conforms to specified tolerances for levelness or, alternately, a particular degree of slope (e.g., for drainage purposes).
Besides determining if and to what degree differential movement has occurred/continues to occur within an area of interest, the data obtained through manometer surveys constitute an important factor when considering if remedial actions to contain and/or correct such movement may be required.
The manometer used in our elevation surveys is the ZIPLEVEL® Pro-2000 High-Precision Altimeter, shown in the photograph below. This manometer consists of a base unit connected to a hand-held measurement module by a durable and flexible cord; it contains a non-toxic and biodegradable liquid. The measurement module is attached to a rigid, 4-foot-long monopole that stabilizes the measurement module at individual measurement locations. The base unit is placed and secured in a position that precludes its movement during the duration of the survey; the measurement module, mounted on top of the monopole, is positioned at the first measurement location. Next, the measurement module is set to zero and the first measurement location becomes the datum of the survey. The rest of the spot elevations, measured at various locations throughout the sample space, are with respect to the survey datum. Differences in pressure between the datum and each location measured cause movement of the fluid within the manometer. These changes in pressure are caused by differences in elevation; the difference in elevation associated with a particular change in pressure is provided as a measurement reading on the display of the measurement module. Following the survey, the respective locations and elevations of all measurements are used to produce a topographic surface that is superimposed over the layout of the sample space. Among other uses, such a drawing facilitates the identification of discrete locations of differential movement.