VALIDATION OF PVP MEASUREMENT ACCURACY WITHIN AN HRX WELL CARTRIDGE

The Horizontal Reactive Media Treatment Well (HRX Well) is a novel, in situ, passive groundwater remediation technology designed to improve the longevity, remedial outcome, and cost-efficiency of a Permeable Reactive Barrier. Point Velocity Probes (PVPs) were installed in cartridges within a HRX Well to monitor its performance. No previous tests had been conducted on the effects of a cylindrical cartridge on PVP measurement accuracy. Concern was given for negative impacts of granular iron gas production and frictional loss of water velocity on the surface of the probe. To address these concerns, laboratory PVP sand columns and computer models were used to investigate the effects of the presence of gas, the application of a PVP inside a cylindrical column (representing a cartridge inside an HRX Well), and the length of the PVP on the accuracy of measurements within the column.

Results of this work indicated elevated PVP velocity measurements with the presence of air when an inducing discharge through the column with a pumping system. However, when air was introduced only to the area around the probe, slower velocities were measured. This was thought to be due to preferential flow of water around the air pockets. There was no significant change to PVP measurement accuracy found in regards to cylindrical column shape and length of PVP. Additionally, models supported uniform flow patterns within the column, suggesting no impact on water velocity within a cylindrical column. Any frictional loss or change in flow patterns are negligible in comparison to variability related to packing and measurement error. Therefore, this study supports the accurate use of PVPs within an HRX Well.