Implications of subsurface heterogeneity at a potential monitored natural attenuation site

Direct-push sampling was conducted at a site previously characterized with conventional monitoring wells. Hydrogeological and chemical heterogeneities not represented in the original site conceptual model were detected by dir ect-push sampling. These heterogeneities were important in terms of their i mpact on the assessment of monitored natural attenuation at the site. This research suggests that additional sampling efforts could be attempted at so me sites to test the accuracy of site conceptual models. The leading edge o f a contaminant plume must be examined closely, because conceptual errors i n this area could easily allow impacts to receptors to remain undetected.