CobbFendley completed a comprehensive analysis of a 1000-acre master planned development area located on EPIA property. As a closed basin, the project was impacted by significant off-site flows generated by portions of Ft. Bliss. Flow contributions doubled the retained runoff from approximately 350 acre-feet to over 800 acre-feet. CobbFendley engineers performed the HEC-HMS analysis to verify these impacts based on previously completed analysis in support of an existing Conditional Letter of Map Revision (CLOMR) from 2008. Mitigation design was completed using HEC-RAS to identify the hydraulic structures needed to isolate the off-site flows while evaluation of modifications to existing retention facilities within the development area was completed. A revised CLOMR was prepared to show changes in the floodplain elevation because of proposed development and changes in the existing retention containment requirements. We also completed a comprehensive Master Drainage Plan and estimate of storm water infrastructure improvements. CobbFendley performed several iterations of the infrastructure improvement requirements due to changes in the development plan during project execution. CobbFendley held regular project team meetings to align and adjust the analysis and report as the development scenarios evolved over the course of the project. Regular updates and coordination meetings served to address this fast-moving project and adjust as development scenarios evolved.