The goal of the PROTECT NIEHS SRP Center is to evaluate exposure to groundwater contamination through karst formations in Northern Puerto Rico and assess the potential impact of said exposure on public health. This will be achieved through integrated analytical, mechanistic, epidemiology and fate-transport studies, along with a centralized, indexed data repository. Prediction of contaminant fate and transport in karst hydrogeological systems is complex due to the presence of a high degree of heterogeneity. Slow seepage through the rock matrix and fast flow through fractures and conduits result in a high temporal and spatial variation in aquifer behavior. Contaminant storage occurs in the rock matrix, but contaminant transport occurs mostly along preferential pathways in the conduit network. Computer models predicting contaminant fate and transport should account for combined matrix and conduit flow. æA distributed groundwater flow and transport model is being developed that includes the central part of the North Coast Limestone Aquifer of Puerto Rico. The model is developed for transport of trichloroethylene (TCE) in the Vega Alta region, where extensive monitoring data and recent monthly weather data are available. The data repository covers i) historical data from more than 1000 wells, springs and contaminated sites; ii) data from biannual field sampling and analysis of 16 wells, 3 springs and 120 tap water samples; iii) continuous meteorological, surface water and groundwater data; and iv) biomedical data (i.e. urine, blood, pregnancy tissues).