Planting trees around the Phase III ponds: As part of Phase II of the project, the team removed invasive plant species and replaced them with native wetland vegetation and trees. Photo by Jaime Flores, Texas Water Resources Institute.
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San Benito transforms abandoned wastewater treatment ponds into coastal wetland habitat BY JAIME FLORES AND KATHY WYTHE
n 2010, the city of San Benito began transforming portions of its wastewater treatment system that not only enhance the city’s treatment of wastewater but also provide a coastal wetland habitat while reducing the amount of bacteria, sediment and nutrients entering the Arroyo Colorado.
After almost a decade, the city has completed the three-phased project. The city now has a 64-acre wetland system that reduces discharge to the Arroyo Colorado while providing a recreational area for citizens and habitat for native plant and wildlife species. According to Jaime Flores, Texas Water Resources Institute (TWRI) Arroyo Colorado Watershed Partnership watershed coordinator, the Arroyo Colorado has high nutrient levels due to nonpoint source runoff from urban and agricultural land and from 24 permitted wastewater treatment facilities that discharge approximately 60 million gallons a day in the Arroyo Colorado watershed. The Arroyo Colorado Watershed Protection Plan, developed by the partnership, identifies wetlands and wastewa-
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ter reuse as management measures to reduce nutrient loadings. Wetlands are able to filter the wastewater, reducing the amount of sediment, nutrients and bacteria, before the water flows into the arroyo. The Texas Commission on Environmental Quality funded Phase I of the San Benito project, which consisted of using outdated, abandoned wastewater polishing ponds to create four one-acre wetland ponds that remove pollutants from the treated wastewater, or effluent, before it is discharged into the Arroyo Colorado. The Arroyo Colorado Watershed Partnership and TWRI began working with San Benito in 2012 on Phase II and then Phase III, both funded by the Texas General Land Office. Phase II involved filling 10 one-acre ponds adjacent to the Phase I ponds and connecting the ponds to form a continuous 14-acre pond system. In Phase III, the city reused three of the 16.67-acre settling ponds from the city’s old wastewater treatment plant. These ponds are approximately 8 feet deep. A separate pump and