Company Research Studies

The study site is a former dry cleaner with elevated levels of chlorinated solvents in its groundwater.  During the 1986/1987 demolition activities, almost all original vadose zone soils were removed along with volatile organic contaminant (VOC) source areas within them.  Prior to October 2013, VOCs in the soil gases were predominantly at low levels (>5 ppbv), except within a cluster of trees located at the center of groundwater contamination.  After the installation of 40 small diameter BVE™ Treatment System probes and conversion of 30 large diameter cased boreholes into GVE™ vents, the temporal and spatial soil gas pressures/distribution patterns radically changed across the entire Site. This lead to the fast degassing of large quantities of chlorinated solvents from the groundwater.  VOC levels in the shallow soil gases increased by orders of magnitude (up to 3,100 ppmv) and became very mobile, with velocities exceeding 80 feet/day.  Due to the elevated Henry’s constants for the chlorinated solvents, the contaminants that degassed into the vadose zone appeared to periodically dissolve back into groundwater elsewhere as they migrated toward the GVE™ vents.  This flux appears to be similar to large scale gas migration processes previously identified by Morris (1994) only at large scale solid waste landfills.  A combination of soil gas/barometric pressures and the developed preferential pathways of the BVE™/GVE™ Treatment Systems were the driving factors for this “Green” groundwater remediation.  The large data set generated during this study strongly indicates 1) single event soil gas surveys may have a negligible value in correctly identifying contaminated source area(s) or vapor intrusion (VI) issues; 2) small but important contaminated groundwater areas are not likely to be detected during most conventional field studies, but their continual input will significantly extend remediation timeframes/cost; and 3) contaminants-degassing from groundwater may occur any time routes of transport are inadvertently created during assessments and/or construction activities.  Due to the uncertainty associated with most data collection activities, low-cost/high density mitigation measures should be university considered to break the transport pathway(s) between contaminant sources and potential receptors in occupied nearby buildings.

Phytoremedial Treatment of Organic Contaminants in Shallow and Deep Groundwater Aquifers

Trees, such as Hybrid Poplars, have been identified as providing a significant remedial effect on contaminated groundwater.  The reason for this is trees are very adaptive to changes in the quantity of groundwater and fluctuations in the groundwater flow.   In areas were water becomes more plentiful, the trees will grow into and use the water up to the maximum withdraw rate of each tree.  Several critical issues effect the success of a phytoremedial treatment process.  The first issue is to design the system to treat the area-wide “contaminated plume”.  If the design does not integrate site-specific hydrogeological conditions, groundwater flow can be faster in selected areas and the contaminant in those areas may by-pass the treatment system.  Another crucial issue to consider is the ability to target the roots into specific contaminated lithologic zones to reduce treatment time/cost.  In order to eliminate these problems, technological advancements have occurred in the last decade.  These engineered phytoremedial treatment processes are now capable of mitigating groundwater contamination in areas were the source(s) are not well known and/or the extent of contamination is poorly defined.  Through the use of these methods, greater effectiveness is also obtained and groundwater at depths greater than 100 ft. can be treated with the same effectiveness as those at the shallow water table.  Further, unlike conventional phytoremedial systems, documentable data can easily be generated and cost effective modifications to the process can quickly be implemented as required/needed. 

Lithostratigraphy: Implication on Sediment Correlation

Multiple cores from a large basin were analyzed by XRF methods to determine the sediments lithostratigraphy as expressed in its geochemistry.  In general, glacial and interglacial sediments each have a distinctly different chemistry.  During glacial events, the sediments have elevated Ti, Fe, Rb, and Zr concentrations and depressed Sr and Mn concentrations.  The opposite is true of the interglacial brown layers, where Ti, Fe, Rb and Zr are lower with higher levels of Mn and Sr.  These data indicate that there are 18 chemically unique lithologic units (LUs) in the study area sediments not definable by other methods.  Isopach maps indicate two general depositional patterns appear to have existed during the late Quaternary.  The first pattern is defined as a glacial depositional pattern based on sediment thicknesses present in Clark et al. (1980) SLUs F, H, J, and L.  The second pattern is associated with interglacial deposits and is based on sediment thicknesses present in SLUs G, I, and K.  The interglacial pattern is also characterized by much thinner deposits.  Based on the isopach sediment patterns, the potential source areas of the sediments deposited during the glacial and interglacial periods are slightly different.  During glacial stages, a strong Canadian source area is suggested.  During interglacial stages a potential mixture of Canadian and Russian source areas exists for those sediments.  Overall the use of the XRF methodologies developed during this study provide a fast and inexpensive technique to quickly correlate strata that are often miscorrelated by other methods.