White pelicans sit above water level at Mitchell Lake.
White pelicans sit above water level at Mitchell Lake. Credit: Bonnie Arbittier / Rivard Report

Water flowing out of a former sewage dump-turned-bird paradise on San Antonio’s Southside could get a lot cleaner if a new San Antonio Water System project works as planned.

Mitchell Lake Audubon Center, a roughly 600-acre area with shallow ponds and lakes divided by dikes, was once the final resting place for all the sewage sludge generated by a growing San Antonio. Sludge disposal ceased there in 1987.

More than 30 years later, the sludge still causes problems that SAWS hopes to address by harnessing the power of nature. Its long-term plans call for man-made wetlands that cover an area the size of 95 football fields. So far, the utility has spent at least $5.3 million on the project.

“In the ‘60s and ‘70s, we would not have been standing here breathing as freely as we are right now,” SAWS spokeswoman Anne Hayden said on a recent tour of the area off Pleasanton Road between loops 410 and 1604.

“It would have been really, really stinky,” she continued.

Nowadays, Mitchell Lake is a stopover point for thousands of migrating waterfowl and other birds. Bird aficionados have logged 342 species at the site, said Sara Beesley, director of the Mitchell Lake Audubon Center. Audubon maintains a center there that serves as a hub of environmental education and ecotourism.

Even on a gray winter day, visitors to the lake can see white egrets stepping along the shore on spindly legs, great blue herons unfolding their wings, and several species of ducks dabbling at the surface.

But not all the legacies of Mitchell Lake’s smelly past are gone. The solid remnants of the sludge left in Mitchell Lake’s sediments and the algae that feed on them are lowering oxygen levels in the water that leaves the lake and ends up in the Medina River downstream.

Low dissolved oxygen levels harm fish by making it difficult for them to absorb enough of the life-giving gas through their gills. That’s why regulators require certain levels of oxygen in the water discharged from facilities like sewage plants.

Algae in Mitchell Lake create lower oxygen levels that harm fish downstream. Credit: Bonnie Arbittier / Rivard Report

On paper, federal environmental regulators still consider Mitchell Lake a SAWS sewage plant, though no such equipment exists there now. In August 2016, the U.S. Environmental Protection Agency issued an administrative order calling on SAWS to correct the problem.

That requires some action from SAWS, the municipally owned utility providing water and sewer services to 1.8 million people in the San Antonio area. The City of San Antonio, through SAWS, owns the lake but leases it to Audubon.

To combat the sludge’s lingering effects, SAWS is planning to eventually create 125 acres of man-made wetlands, including native plants that can passively purify water flowing through them and help protect against downstream flooding.

“You let the wetlands do what they’re truly intended to do,” Audubon Texas Conservation Director Iliana Peña said. “Plants will uptake nutrients, they’ll add oxygen to the water so that by the time it does leave, it actually is good enough quality to end up back in our rivers.”

SAWS officials expect the project will take quite a while. Initial work on the full 125 acres would not even start until 2021, according to a presentation by SAWS senior analyst and water historian Gregg Eckhardt.

On Jan. 19, the City, through SAWS, purchased 283 acres of land just south of Mitchell Lake, according to county records. At its January meeting, the SAWS board approved the $4 million purchase from a partnership that includes James Trautmann and Robert  Trautmann Jr. of San Antonio and attorney J.C. Treviño III of Laredo, according to state records.

Mitchell Lake dam
A dam at the south end of Mitchell Lake allows some water to flow downstream. Credit: Brendan Gibbons / Rivard Report

The first step is a small pilot project to ensure the man-made wetlands will function as planned. In October, the utility approved a $1.3 million contract with Alan Plummer Associates to design, manage construction, and operate the initial pilot project. SAWS will select a construction contractor under a separate contract.

The project could also involve changes to a dam built in 1901 that would allow better control of lake volume. Water in the lake currently comes from rainwater and cleaned, recycled sewer water treated at SAWS’ Leon Creek Water Recycling Center.

SAWS hopes to get some additional funding from the U.S. Army Corps of Engineers through its ecosystem restoration program.

In an email, SAWS Vice President of Water Resources and Governmental Relations Donovan Burton said SAWS has had “numerous conversations with [the Corps] about this project” but that no money has yet been committed.

SAWS has found an ally in U.S. Rep. Will Hurd (R-Texas) who joined Audubon and SAWS officials on a Feb. 10 birding tour of the lake. Hurd said he would work to get federal funding for the project and get it more attention from the Corps’ Fort Worth district.

“We need to get in the president’s budget, and we want to make sure the [Fort Worth] region makes it a higher priority,” Hurd said.

(From left) Mitchell Lake Audubon Center Director Sara Beesley, U.S. Rep. Will Hurd (R-Texas), SAWS spokeswoman Anne Hayden, and SAWS Vice President of Water Resources and Government Relations Donovan Burton tour Mitchell Lake. Credit: Bonnie Arbittier / Rivard Report

Audubon officials also want to provide some funding for science and monitoring efforts but don’t know how much yet, Peña said.

During the tour, Peña explained that Mitchell Lake is somewhat of an anomaly. For probably thousands of years, it has served as an oasis for birds and other wildlife in an otherwise harsh South Texas thornscrub environment.

The lake appears on Spanish-colonial maps and was once called Lago de los Patos, or Lake of the Ducks, Peña said. It was later renamed after Asa Mitchell, a member of one of the Old Three Hundred families who moved to Texas to settle in Stephen F. Austin’s colony.

In a 1913 book, San Antonian Rudolph Menger wrote that Mitchell Lake was three miles long, shallow enough to wade across, and “an immense gathering place for all sorts of wild animals.”

It still is, with Hurd and others on the tour getting to see a flock of white pelicans perched near the shore waiting to scoop fish into their stretchy pouches.

“I’m just still trying to wrap my head around the fact that we have pelicans in San Antonio,” Hurd said.

This kind of wildlife sanctuary is already serving as an economic driver on the Southside, Peña and Beesley said. Birdwatchers and ecotourists from around the country visit the lake, hoping to add birds to their checklists before moving on to other South Texas bird hotspots.

An American coot swims in Mitchell Lake.
An American coot swims in Mitchell Lake. Credit: Bonnie Arbittier / Rivard Report

There’s some evidence Mitchell Lake is serving as an attraction to residents, too. On its eastern shore lies Mission del Lago golf course and an ever-growing set of housing developments.

In a 2014 news release and promotional materials on its website, developer SouthStar Mission del Lago touts lakeside trails and the “natural beauty” of Mitchell Lake as a reason to buy a home there.

Brendan Gibbons

Brendan Gibbons

Brendan Gibbons is the Rivard Report's environment and energy reporter.