Plummer designed the original 0.68-MGD Denton Creek Regional Wastewater System wastewater treatment plant in the late 1980s, followed by expansions to 2.5 MGD in 1995, to 5 MGD in 2003, and to 11.5 MGD in 2010. The original plant consisted of a primary clarifier, conventional activated sludge basins, rectangular final clarifiers, effluent filters, and the first UV disinfection system in Texas.

In the expansion to 2.5 MGD, the primary clarifier was converted to a sludge holding basin and a sequencing batch reactor was added to provide treatment for the periodic high flows from the Texas Motor Speedway race events.

Additional sequencing batch reactors and cloth filters were added in the expansion to 5 MGD and the UV system was rehabilitated and expanded. The expansion to 5 MGD also included a Tier II Clean Water SRF Environmental Assessment.