A thorough assessment led the former consultant to conclude that there was no cost-effective remedial solution for this site. The soil consists mainly of silt, 
clay and some peat, retarding COI migration. Monitored Natural Attenuation (MNA) was deemed sufficient for this case and accepted by the regulators. A back-up 
scenario was available in case of unexpected COI migration. The client, a real estate investor, prefered to terminate the need for perpetual monitoring and 
was willing to invest a premium in a final remedial solution. However, active measures were required to achieve this goal. Effective in situ remediation is 
not always a simple task:   
1. The subsoil is very sensitive to subsidence (wet clay & peat). The premises, like all other buildings in the area, are not based on firm foundations such 
as pilings. Subsidence is likely to damage the property.   
2. Pump & Treat is virtually impossible, and in view of the low permeability, probably would not affect COI migration.   
3. The area is densely built-up and many cables, lines, pipes, ducts and sewers are present in the subsoil. Visiting customers must not be hindered by remediation 
activities.   
4. The area is a popular recreational-shopping area with fashionable boutiques, cafés, bars, restaurants, and summer boating. 
            

The field contractor assessed available data and concluded that natural attenuation will not sufficiently reduce source zone COI concentrations. An alternative 
remedial solution for this complex case was developed. The solution was based on combining three techniques:   
1. In Situ Chemical Reduction (ISCR) was selected as the most optimal approach for the source zones, where the highest COI concentrations were found. EHC® 
was injected to significantly reduce COI concentrations.   
2. For the other areas, enhanced natural (anaerobic) attenuation was selected, supported by the injection of a suitable substrate, to create and maintain 
a strongly anoxic environment, which facilitates the degradation of chlorinated hydrocarbons.   
3. Soil stabilizing agents were selected that would greatly reduce the soil’s permeability, if necessary. The result would be that groundwater could not 
migrate, eliminating relocation of COIs.   
   
Direct injection. In the first round, Groundwater Technology BV injected a balanced mixture of substrate and zero-valent iron (EHC). Active agents are 
pumped into the ground through a pressurized injector system. The high injection pressure effectively disperses the slurried mixture. The amendment used 
in the first injection-event consisted of a mix of micro-scale ZVI, substrate and fertilizer to chemically convert the COI’s into harmless compounds, as well 
as enhance natural attenuation. Performance monitoring has shown excellent COI reduction in a timely manner. Costs were under EUR 37.000. 
            

EHC® technology describes a family of remediation products used for the in situ treatment of groundwater and saturated soil impacted by heavy metals and persistent 
organic compounds such as chlorinated solvents, pesticides and energetics. The technology is a modification of our DARAMEND® technology which has been used 
since 1992 to treat over 9,000,000 tons of similarly effected soil and sediment. Both EHC® and DARAMEND® are the subjects of numerous patents owned by Adventus 
Intellectual Properties, Inc. (Adventus).   
   
EHC® is a controlled-release, integrated carbon and zero valent iron (ZVI) source that yields redox potential (Eh) in the -500 to -650 mV range. This Eh is 
significantly lower than that achieved when using either organic materials (lactate, molasses, and sugars) or reduced metal alone. Eh potentials in this 
range facilitate the timely and effective removal of normally recalcitrant chlorinated organics (e.g., CT, PCE) and other persistent compounds (e.g., perchlorate) 
without the formation of potentially problematic intermediates, such as DCE/VC from the anaerobic degradation of PCE/TCE or CF/DCM from the anaerobic degradation 
of CT.