The existing computer model was updated to simulate the current and future sanitary sewer collection system using Innovyze's InfoSWMM sewer modeling software. Data for all trunk lines, pipes, and sewer manholes were obtained from the 2012 sewer master plan study and from current GIS data, both of which were provided by the City. Manhole inverts and pipe depths were field verified by the City as needed.
The model includes all pipes within the City with a diameter of 8-inches or greater, and all associated manholes, diversion structures, and lift stations. The pipeline length and diameter data, connectivity of upstream and downstream manholes, and existing or future status were included in the model database. The pipeline slopes in the hydraulic model are calculated based on invert elevations and pipe length. A Manning's "n" value of 0.013 was used for all pipes, based on a typical roughness value for a vitrified clay pipe. Figure 3-2 presents the City's collection system in the hydraulic model, which includes every existing pipe and respective pipe diameter sizes.
During the model update process, it is common to complete minor interpolations or assumptions due to incomplete or inaccurate data. This was done for a small number of manholes and pipes and is documented in Appendix B as "GIS Data/Model Adjustments Summary (Interpolation)."
From the completion of the 2012 master plan to the commencement of the 2019 master plan, new development occurred within the City, particularly on the west side of the City. Much of the growth consisted of residential developments. Due to the residential units being clustered together in developments, the residential flows were added to the model manually by visually assigning the flow for each residential unit to the nearest sewer manhole.
Non-residential flows were added to the model based on data provided by the City. While some of the non-residential connections for which the City provided flow data were already included in the model from 2012, others occupied newly developed areas or replaced non-residential connections that were included in the 2012 sewer master plan study. To avoid repetition of any non-residential flow within the model, the non-residential flow data from 2012 was completely removed from the model before adding the newly provided non-residential flow data from the City.
To add the new non-residential flows to the existing model scenario, a GIS point layer was added to the model, with each point representing a non-residential connection. The location of each point was based upon the address that was provided with the non-residential flow data from the City. Each point contained the calculated flow data associated with the non-residential connection. Using the flow allocation tool, each non-residential flow was assigned to the upstream manhole of the nearest pipe. Following allocation, a visual inspection of the assigned manholes was completed.
A total of approximately 27,500 separate demand loads were entered into the model between the 2012 and 2019 sewer master plan studies.
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