2.3.1. Model Grid

The model grid was generated using RGFgrid from the Delft3D software package [6] (Figure 3). The domain spans 116 km of the tidal Delaware River from the downstream water level open boundary at Delaware City, DE, USA to the head of tide at Trenton, NJ, USA. The tidal extents of the Schuylkill River and three tributaries (Cobbs Creek, Frankford Creek, Pennypack Creek) that receive City of Philadelphia CSO discharges are represented in the model. The grid contains 9746 elements with lengths ranging from 17 m in the lateral direction in small tributaries to 650 m longitudinally in the Delaware River, and has five vertical sigma layers that follow the bottom geometry.

**Figure 3.** Model domain and grid.
