Calderwood Building Complex

Since 2017, WHEM has been conducting environmental testing and subsurface characterizations at the Calderwood state office building in Saint Johnsbury that housed administrative and office space for several State of Vermont entities for many years.  The Calderwood building complex was identified as having a former dry cleaner in the 1940-70s, so WHEM was contracted to assess whether contamination remained under or inside the building.  The sampling effort was coordinated with the VT DEC, the Department of Buildings and General Services, and the Human Services Agency.  After sampling results confirmed the presence of PCE in sub-slab vapor, WHEM went on to identify indoor air concentrations in exceedance of Vermont Department of Health guidelines.  This was followed by several rounds of additional testing and characterization. 

To date, sampling has included indoor air, sub-slab soil vapor, deep and shallow ambient soil vapor, soil, groundwater, and concrete.  Use of a membrane interface probe and hydraulic profiling tool (MiHPT) over a multi-day effort ruled out any significant contaminant mass in the soil or groundwater.  However, elevated soil vapor concentrations are present under the former dry cleaning space in the Calderwood building, and also upgradient of the building along the Eastern Avenue corridor.  Concurrent assessments in surrounding properties also revealed soil vapor with PCE, suggesting a large release to the north affecting a large portion of this neighborhood.  

WHEM has gone on to develop an Evaluation of Corrective Action Alternatives and  Interim Corrective Action Plan for the project, which will involve the installation of mitigation systems in each building to control vapor intrusion and allow the buildings to be re-occupied.  Ongoing groundwater monitoring is also being conducted.

Since 2017, WHEM has been conducting environmental testing and subsurface characterizations at the Calderwood state office building in Saint Johnsbury that housed administrative and office space for several State of Vermont entities for many years.  The Calderwood building complex was identified as having a former dry cleaner in the 1940-70s, so WHEM was contracted to assess whether contamination remained under or inside the building.  The sampling effort was coordinated with the VT DEC, the Department of Buildings and General Services, and the Human Services Agency.  After sampling results confirmed the presence of PCE in sub-slab vapor, WHEM went on to identify indoor air concentrations in exceedance of Vermont Department of Health guidelines.  This was followed by several rounds of additional testing and characterization. 

To date, sampling has included indoor air, sub-slab soil vapor, deep and shallow ambient soil vapor, soil, groundwater, and concrete.  Use of a membrane interface probe and hydraulic profiling tool (MiHPT) over a multi-day effort ruled out any significant contaminant mass in the soil or groundwater.  However, elevated soil vapor concentrations are present under the former dry cleaning space in the Calderwood building, and also upgradient of the building along the Eastern Avenue corridor.  Concurrent assessments in surrounding properties also revealed soil vapor with PCE, suggesting a large release to the north affecting a large portion of this neighborhood.

WHEM has gone on to develop an Evaluation of Corrective Action Alternatives and  Interim Corrective Action Plan for the project, which will involve the installation of mitigation systems in each building to control vapor intrusion and allow the buildings to be re-occupied.  Ongoing groundwater monitoring is also being conducted.