Covers an area in southeastern Pima County that drains the Arivaca Creek watershed. The purpose of the report is to estimate peak discharge for the 50 year storm frequency event, utilizing the rational method (Q=CiA). This method pre-dates that outlined in the Hydrology Manual for Engineering Design and Floodplain Management within Pima County, Sept. 1979, and is considered less accurate. It is recommended that this report be archived and discontinued for use for regulatory purposes.