Mature groundwater plumes for environmental contaminants pose a complex challenge with regards to accurate delineation of sources, vertical and lateral extent, dominant pathways, and likely storage zones for residual contaminants. It is not uncommon for plumes from multiple sources to commingle and diffuse across a relatively large distance and a varied hydrogeological spatial volume. As a result, uncertainty in the accuracy of the conceptual site model (CSM) increases, and in turn the associated risk assessment, and the costs contemplated for cleanup alternatives. Better data resolution and scale are required to reduce these uncertainties. Low-Level Membrane Interface Probe Technology with Hydraulic Profiling (HPT) provides one approach for obtaining cost-effective and reliable high-resolution data, at a more informative scale in order to improves CSMs and enable better decision-making.