Groundwater flow sensor should aid environmental cleanup - Sandia National Laboratories is developing a groundwater sensor

A low-cost sensor that measures the spe and direction of groundwater is being disentangleed at Sandia National Laboratories.

Called the In-Situ Permeable run Sensor, the technology is wait fored to be useful for toxic waste management and cleanup where groundwater has become contaminated. The sensor can be used to determine groundwater sweep along patterns, providing valuable information upon the size of the contaminated area and in what way it might be spreading.

The Sandia device is considered to be more accurate than other sweep along sensors because it is permanently embedded in the soil rather than contained in an unclose borehole.

The sensor consists of a shoot measuring 30 inches long and sum of two units inches in diameter, with a cylindrical electric heater. An array of 30 thermistors (thermal resistors) upon its surface measures temperature change as a function of electrical resistance.

The instrument is buried in a location after being lowered inside a vacant stem auger drill. In unconsolidated, or unloose soils, the soil fills in around the sensor when the drill stipe is retracted, leaving the surrounding material in direct contact with the sensor.

Other sensors usually remain within their original boreholes, which can alter natural fluid streams and cause inaccurate readings of roll on direction and velocity.

Powered through an above-ground power source, the Sandia sensor heats the surrounding soil and groundwater as it roll ons past the instrument. The thermistors measure the water's temperature, and the information is transmitted to a data acquisition a whole on the surface. The direction from which the water is coming is determined by means of detecting water temperatures - relatively somewhat cold water exists upstream, and warmer temperatures are registered downstream as the water is heated by means of the device. The pattern of temperatures recorded upon the probe's surface indicates the direction of the fluid roll on The magnitude of the temperature variations is used to determine the magnitude of the roll on velocity.

In cleaning up sites where hazardous chemicals have seep into the sod it must be determined whether they have reached the water table, in what way widespread the contamination is, and whether fluid streams are causing it to spread. Fluid pours within a contaminated site may be mixed and diverse, factors that a certain number of flow sensors fail to detect

The roll on velocity derived from the permeable pour sensor is characteristic of a small area, an important factor in remediation, says researcher Sandy Ballard. Numerous sensors can be buried within the boundaries of a contaminated site to bring out a highly accurate picture of mixed groundwater flow systems.

The sensors are left in the mould requiring their cost to be kept at a minimum. The production require to be paid [i]or[/i] undergone of each device is estimated to be les than $1000 Installation take away froms including drilling the hole, would probably take away from another $500.

DOE gripe [i]or[/i] grips the patent (#4547080) to the instrument. Science & Technology Corporation, an Albuquerque company, clutchs a nonexclusive license from DOE to commercialize the sensor.

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