The model predictions represent the probability that nitrate concentrations will exceed certain threshold values in private domestic wells based on a limited set of model inputs. In this layer, threshold values of 3 mg/L, 5 mg/L, and 10 mg/L were modeled as representative of the background, elevated, and maximum contaminant level for nitrate in groundwater, respectively. Ultimately, this estimate is just one tool for use by NDEE and agency partners. Regardless of the predicted risk, private domestic well owners are strongly encouraged to sample their well annually to properly assess their specific risk. Model construction and results offer valuable insights into the relationship between nitrate concentrations in Nebraska, common sources, hydrogeological factors, and land-use trends. Exploratory analyses and literature review were first conducted to identify potentially influential factors, then Boosted Regression Trees (BRTs) were trained to classify wells likely to exceed each threshold value. Finally, the BRTs were generalized across the State of Nebraska and evaluated against private domestic well samples from the 2023-2024 NDEE free nitrate sampling effort. Model performance was strong for the testing and training data, and the model surfaces had acceptable performance compared to the fully independent private domestic well samples. However, additional work on the model is recommended to incorporate additional variables known to impact nitrate concentrations and reduce the false negative predictions (under prediction of nitrate concentration). Modeling documentation (Appendix C to the Nitrate Study) is available on the DEE website.<\/p>