Groundwater Modeling, Former Fort Devens, MA

Sovereign completed a major revision to a groundwater flow model for a landfill at the former army base at Fort Devens in Massachusetts.

The ongoing collection of water level and other data along with the recent installation of a barrier wall necessitated an update of an existing MODFLOW groundwater model. After reviewing the model, Sovereign proposed expanding the model domain, converting it to simulate seasonal changes, reassessing other parameters, and developing thorough documentation. The model was calibrated to over 1,100 water levels from 12 different time periods and two different pumping tests, and also to measured groundwater fluxes into a pond adjacent to the landfill.

After successful calibration, the model was used to simulate the flow path of groundwater from the landfill area where dissolved arsenic concentrations exceed standards. Particle tracks show some groundwater is captured by extraction wells at the landfill while others flow into surface water. Model results also show that the barrier wall has been successful in significantly reducing groundwater flow into the nearby pond. The modeling results were used in support of a long-term monitoring plan to continue to evaluate arsenic concentrations in groundwater beneath the site.

Key project elements:

• Subsurface contaminant evaluations and compliance monitoring

• Groundwater and solute transport modeling

• Groundwater-surface water interaction studies

• Landfill monitoring and regulatory compliance