Interpreting and Responding to Intensified Site Characterization Results
Abstract
High-resolution site characterization is being applied at an increasing number of sites especially large-plume sites with long-standing chlorinated solvent source zones. This allows us to improve remedy design and operation, but it can also add to the challenge of regulatory closure, particularly in jurisdictions that require all groundwater to reach MCLs including locations where groundwater cannot be extracted at rates that would allow use for water supply. Common patterns are emerging from these sites, including: Heterogeneous, anisotropic aquifer matrix structure, even at sites that were expected to be relatively homogeneous, Contaminant mass transport focused in a small fraction of the aquifer matrix crosssection (more than 90% of the mass transport is occurring in less than 10% of the aquifer matrix), Extremely small transverse dispersivities; and In locations where the aquifer matrix has been exposed to soluble contaminants over extended periods, a significant portion of the contaminant mass resides in lowerpermeability zones. In many locations, there is a large divergence between contaminant concentrations in groundwater extraction wells (or monitoring wells pumped at modest to high specific flow rates) and small-scale sample collections from lower-permeability zones. Contaminants located in the lower-permeability zones can be very difficult to treat and the challenge of meeting MCLs across all permeabilities is significant. This paper provides details of recent high-resolution sampling programs at large plume sites and examines how site hydrogeology and contaminant chemistry interacted to create the distribution patterns that are being observed. Then, the paper examines the prospects for remedial action in these zones, with data from multiple technologies in heterogeneous aquifers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2011
- Accession Number
- ADA554570
Entities
People
- Fred Payne