From concept to completion, it took a decade to get from initial assessment of Sessom Creek to construction of the Sessom Creek Phase 1 Restoration Project to its widely-celebrated ribbon cutting. And, just like a small meandering Texas stream, this project took a few twists and turns before it finally found its footing and a team of supporters to see it through to conclusion.

“There was a report done by the City of San Marcos that identified a large and aging sewer pipe running through the middle of Sessom Creek as a potential threat to the water quality of the San Marcos River,” said Shaun Condor, City of San Marcos Director of Engineering and Capital Improvements. The sewer line was exposed and suspended over the creek in several areas as a result of erosion of the streambed, leaving it vulnerable to breakage especially during high stormwater runoff events.  “While we had never experienced a leak from that pipe, we knew it was just a matter of time before it would fail. So, we looked at multiple ways to remedy that problem and finally designed a project to relocate approximately 1,800 feet of 12-inch wastewater main out of Sessom Creek. Early on in the process, staff from the Edwards Aquifer Habitat Conservation Plan (EAHCP) contacted us and talked about their plans to mitigate the large amount of sediment coming from Sessom Creek and depositing in the San Marcos River. In the end, partnering with the EAHCP helped us produce a more cost effective and environmentally sound project that works for the City of San Marcos and the endangered species living in the San Marcos River.”

The Sessom Creek watershed is a relatively small, 430-acre area, but all of its runoff from rainfall empties directly into the headwaters of the San Marcos River where endangered species and their critical habitat are located. Sessom Creek is surrounded by impervious cover with the nearby Texas State University, major thoroughfares, apartment complexes and densely populated neighborhoods. With little to no filtering of Sessom Creek stormwater runoff, pollutants and heavy sediment from the watershed would be deposited directly into the San Marcos River after heavy rains. That particular environmental problem was something the EAHCP had been studying and knew it needed a long-term solution to get the issue under control.

“Early on in the EAHCP implementation, we were spending time and money removing sediment from the San Marcos River to enhance water quality for the endangered Texas wild-rice and fountain darters living near the confluence of Sessom Creek and the San Marcos River,” explained Mark Enders, Habitat Conservation Plan Manager for the City of San Marcos. “We determined that a better EAHCP answer to the sediment question was to greatly reduce the amount of sediment from occurring in the first place. That meant we would need to rework the flow of Sessom Creek, stabilize the streambanks, remove invasive, non-native plants that had a stranglehold on the watershed and replant native plants to secure the streambed and embankments. Fortunately, we were able to join the City of San Marcos’ efforts to relocate the old wastewater main and implement a project to stabilize the streambed and banks to reduce erosion and reduce sedimentation in the San Marcos River.”

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Over the years, non-native plants such as the very hearty ligustrum tree began to assert its vegetation dominance in the watershed. The ligustrum grew so extensively that it created a canopy over the understory blocking out sunlight and essentially outcompeting native plants and grasses. Those native plants are necessary to stabilize the soil and creek banks which in turn prevents erosion.

Another objective of the project design was to slow down the water flowing through the creek after large rains. That called for incorporating “natural stream design” elements to refashion major sections of the creek. Grade and gully controls using large boulders and rocks were installed to reshape the meanders of the creek and reduce the velocity of flowing water. This type of stream restoration is not only less costly than using truckloads of concrete, but it slows water flows to a point where it can more easily seep into the ground. It also reduces sediment movement and is better for the overall ecology of the watershed.