CPS Energy & SAWS sustaining beauty of Mitchell Lake

CPS Energy and SAWS (San Antonio Water System) have worked together to conserve water and energy for many years. Some things just never change and sometimes that’s a good thing.  Now, the two city-owned sister utilities are working to benefit the environment. 

Mitchell Lake is home to a body of water that attracts huge numbers of migratory birds.  It was originally built in 1901 as a very progressive wastewater reuse project, and until the 1970s it served as a source of irrigation water for up to 4,500 acres of croplands. 

The lake has come a long way since then, but there is one major concern for SAWS, who oversees maintenance of the lake and has partnered with the National Audubon Society to operate the site as a bird sanctuary.  Remnants of ancient wastewater sludges grow algae, which can get into the Medina River when water leaves the lake after heavy rains.

In response, the pilot stage of a program announced last year to purify water leaving Mitchell Lake is well underway. Taking a natural solution to this problem, the project entails harvesting giant bulrush, alkali bulrush, and Olney’s bulrush for planting in a constructed wetland adjacent to the lake. These long-stemmed plants can grow upwards of 20 feet and naturally filter out the high algal biomass in lake water while removing nitrogen and suspended solids—increasing oxygen and water quality. 

Guess who has plenty of bulrush in San Antonio? Visit Braunig Lake and you’ll see thousands of these plants dancing in the wind. As owners of Braunig Lake, CPS Energy was happy to allow contractors to harvest 5,200 giant bulrush plugs (each plug is 1-2 stems) for the Mitchell Lake project. Harvesters visited the lake on June 19 to pack the stems in buckets and deliver to Mitchell Lake for planting. It’s an incredibly intricate and delicate process to ensure the plants are in good condition for replanting. Both lakes have similar levels of dissolved solids, which gives the Braunig Lake bulrush a better chance of surviving in their new home at the Mitchell Lake wetland. The 5,200 giant bulrush plugs are a drop in the bucket at Braunig where thousands upon thousands of the plants thrive. 

The Mitchell Lake project serves as a great example of CPS Energy’s environmental stewardship. The utility’s environmental sustainability department took root in the operations of the company back in the 1970’s. Since then, CPS Energy has dedicated its efforts to educating and sharing information with customers about its environmental programs, diverse generation mix, energy conservation, and how the utility continues to lower its carbon intensity to reduce its impact on the environment. 

The bulrush plugs are planted at Mitchell Lake the day after they were harvested.

Considered a true gem located in the far southside of town, Mitchell Lake has evolved into a beacon for nature lovers and Science Technology Engineering and Math STEM-based educators. The Audubon Nature Center hosts native plant workshops, birding tours and is home to a day-long festival for the entire family. Learn more about Mitchell Lake here.

Individually, CPS Energy and SAWS have always worked diligently to promote sustainability, encourage economic growth and spur innovation in new technologies. The Mitchell Lake project is another fine example of the accomplishments that can be achieved when they work together for the greater good of the San Antonio community.  

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