Engineers tell council wastewater model needs update as multifamily growth outpaces assumptions

City engineers urged the Rowlett City Council to update the city's wastewater model after development trends exceeded previous assumptions, particularly in North Shore and Signature Gateway.

Molly Pearson said the current model dates to about 2010 with partial updates in 2015 and that recent flow-monitoring and new multifamily projects have changed demand. "The development assumptions I was given in 2015, the number of multifamily apartments has already exceeded what was in those assumptions," Pearson said, adding that multifamily is higher-density and can markedly raise sanitary flows through the West Side Lift Station and the SH-66 corridor.

Council members repeatedly cautioned against a piecemeal approach, citing Liberty Grove as an example of unintended consequences from spot repairs and development. One councilmember warned, "We don't want to be back up here after this is completed... we didn't consider these issues." Staff said the model update will inform whether the city needs a future parallel force main, upgrades to the West Side Lift Station, and downstream gravity-line upsizing; staff also recommended coordinating model assumptions with community-development staff.

Next steps: staff recommended completing the model update and using it to develop a long-term capital-improvement plan tied to development forecasts and planned annexation or rezoning decisions.