The Drinking Water Mapping Application (DWMA) provides EPA with Web-based tools to generate reports and maps vital to managing drinking water programs under the Safe Drinking Water Act. The DWMA is an application within EPA's Watershed Assessment, Tracking & Environmental Results (WATERS) architecture that uses ESRI ArcIMS, the Oracle database, GIS mapping layers using ESRI's SDE, and external image and feature layers from EPA, the USGS, and the Microsoft TerraServer. The current DWMA Version 3 applies the enhanced National Hydrography Dataset (NHDPlus) to develop Source Protection Areas for surface intakes based on NHDPlus catchments. While EPA maintains security policies on the locational data related to drinking water facilities, it is possible to present information from other programs that involve the results of proximity analyses for information in the DWMA. Examples are given on how DWMA content can be applied in cross-program geospatial analyses drawing on information from the EPA's Total Maximum Daily Load (TMDL) program and on approaches developed in a pilot project involving underground storage tanks.