Oxford manages a 2-MGD water supply developed in two glacial-fluvial valleys in Butler County, Ohio. Ground Water Science performed the WHPA delineation (MODFLOW-MODPATH) for the eastern Seven-Mile wellfield, which is also a politically sensitive resource, in a complex two-layer aquifer irregularly confined with multiple clay lens units, using a combination of extensive background information (in some ways misinterpreted in past work) and extensive site work to determine aquifer-stream interactions. Notification of endorsement by the Southwest District Office occurred within two weeks of submittal. Testing at a potential new site proved the site to be economically nonviable.