This project evaluated the performance of the SCAPS Hydrosparge (HS) Volatile Organic Compound (VOC) Sensor System to determine its range of applications, data quality, reliability and cost effectiveness as a groundwater screening tool. The HS VOC Sensor System interfaces a direct push, "mini-well" and sparging unit with a field portable Teledyne or Finnigan direct sampling ion trap mass spectrometer (DSITMS). A 20-ton truck mounted Cone Penetrometer Test (CPT) platform is used to install temporary "mini-wells" by direct push technology. After mini-well installation, the HS VOC sparging device is lowered into the water table via an umbilical cable interfaced to a DSITMS. Thus configured, the HS VOC Sensor System has the capability to perform in-situ analysis to quantify VOCs in groundwater at depths to 50 meters.
The SCAPS HS DSITMS Sensor System was tested to depths of 24 meters at three Department of Defense (DoD) sites with chlorinated VOC and BTEX compound contamination. The results were compared to offsite analysis by EPA method 8260A for VOC identification/quantification and to samples obtained from conventional monitoring wells. There was strong correlation between results of the in-situ HS DSITMS Sensor System and offsite split samples results analyzed by EPA Method 8260A for verification and validation. There was also good correlation between HS DSITMS Sensor System samples collected adjacent to existing conventional monitoring wells and to groundwater in the conventional monitoring wells sparged and analyzed with the HS DSITMS Sensor System. Independent evaluation of performance by the California EPA has resulted in formal certification of performance (www.calepa.ca.gov/EnviroTech/).
The SCAPS HS DSITMS Sensor System can be used as a semi-quantitative in situ measurement device to conduct onsite near real-time interrogation of groundwater for VOC contamination. Data collected by the HS DSITMS system may also be used to optimize the placement and number of conventional wells needed for site characterization and long-term monitoring of installation restoration activities. The HS DSITMS system reduces costly and time-consuming laboratory analysis during initial site investigations, limits potential personnel exposure to contaminated media, and reduces the amount of investigation-derived waste normally generated during conventional drill and sample activities. Although direct comparison of costs is difficult, the HS DSITMS system is typically expected to provide greater than 50 percent savings when compared to conventional monitoring well installation and sample analysis techniques. The HS DSITMS system also provides additional savings derived by optimum placement of conventional monitoring wells and by limiting the number of conventional wells needed to monitor site restoration activities.
The HS System has some limitations that include CPT platform accessibility to site, mini-well screen clogging in silty formations, inefficient well development due to low conductivity groundwater conditions, umbilical transfer line contamination or ITMS overload due to direct sampling in highly contaminated conditions, and impaired CPT mini-well installation in media with cemented sands, gravel, cobbles, boulders, and bedrock. (Project Completed - 2001)