The One Water School

Blue Hole is a renowned, but fragile, swimming spot on Cypress Creek in Wimberley, Texas. (Photo Credit: Courtney Havenwood)

A primary school in a water-stressed region of Texas features multiple One Water strategies to reduce potable water consumption, harvest stormwater runoff, treat and reuse water onsite, and achieve significant long-term savings. By Jay Landers

In August 2020, classes began at the Blue Hole Primary School, a recently completed educational campus in Wimberley, Texas, that includes rainwater harvesting, green infrastructure, and a treatment system to facilitate the beneficial reuse of graywater and blackwater onsite. Conducted as part of a unique partnership involving the local school district, environmental organizations, and engineering and construction firms, the project illustrates the many possibilities and advantages to be gained by deploying One Water strategies.

Air conditioner condensate and rainwater that falls onto the Blue Hole Primary School are captured and used either for flushing fixtures or for irrigation. Any water that exceeds the capacity of the school’s storage tanks is directed to onsite green infrastructure features. (Photo Credit: Wimberley Independent School District)

Watching out for local water bodies

Located about 40 miles southwest of Austin, the city of Wimberley is nestled within the rugged landscape and karst topography of the Texas Hill Country. Home to approximately 3100 residents, Wimberley is situated at the confluence of Cypress Creek and the Blanco River and is renowned for two swimming holes famed for their cold, clear, and clean water—Jacob’s Well and Blue Hole. An artesian spring that includes the second-largest fully submerged cave in Texas, Jacob’s Well forms the headwaters of Cypress Creek, while Blue Hole is a well-known destination on the creek itself. As fragile as they are beloved, the two areas require protection to preserve their natural beauty as well as the quantity and quality of their waters. 

Wimberley is in Hays County, the third-fastest-growing U.S. county between 2010 and 2020. With its population swelling by more than 50 percent during the decade, Hays County is in the midst of a building boom that is leading to more impervious surfaces and stormwater runoff. As a result, higher levels of sediment, nutrients, and bacteria are entering local waterways, including Cypress Creek. Against this backdrop, participants involved in the planning and design of the Blue Hole Primary School wanted to show how responsible development can help to address such problems. 

“Managing stormwater and setting that example for future development was a key component,” says Nick Dornak, the director of watershed services for the Meadows Center for Water and the Environment at Texas State University.

The Meadows Center coordinates the Cypress Creek Watershed Protection Plan, a locally developed effort to protect water quality within the watershed and ensure sufficient groundwater levels needed to maintain flows in Jacob’s Well and Cypress Creek. For this reason, the Meadows Center took a definite interest in the development of the planned Blue Hole Primary School. “The school is located in the heart of the Cypress Creek watershed,” Dornak says.

The school’s proximity to the water feature for which it was named only intensified the need for a properly planned and designed project that would not contribute to the degradation of the iconic swimming hole. “Directly downstream of the school is the Blue Hole swimming area, which is a huge tourist attraction, just a beautiful section of Cypress Creek where thousands of people go every year to swim,” Dornak says. “Maintaining high water quality in Blue Hole is imperative to the city economically as well,” he notes. “We wanted to minimize any kind of site runoff there that could pollute the creek.”

Conserving local water supplies

At the same time, taking steps to reduce water demands associated with the new school would help address another local problem, limited water availability. “In the Hill Country, growth and development have stressed the water supply,” says Robin Gary, the managing director of the Wimberley Valley Watershed Association (WVWA), a nonprofit organization that works to preserve and protect water resources in the Hill Country. 

“Local residents rely on groundwater from the Trinity Aquifer for their sole source of drinking water—either from private wells or groundwater-supplied water utilities,” Gary says. “The Trinity Aquifer is drought-prone and has seen substantial, chronic water level declines over the past years. Innovative water conservation and alternate supply strategies are essential to develop sustainability.”

“Early in the planning process for construction of the new Wimberley Independent School District (ISD) primary campus, the WVWA recognized the opportunity to incorporate One Water principles into the design,” Gary says. “Not only would it serve the community by lessening the water footprint of the campus, but also it would be an optimal teaching platform for these innovative STEM (science, technology, engineering, and math) One Water strategies,” she says.

As the Wimberley ISD moved forward with its efforts to develop the 85,000 sq ft Blue Hole Primary School, Dornak and two WVWA representatives—executive director David Baker and former president and advisor Joe Day—met with the district to pitch the inclusion of various One Water elements on the project. 

“When we were first approached about the project, I was interested, because living in the Hill Country, I know that water is a precious resource,” says Dwain York, the superintendent of the Wimberley ISD. “The more we learned about the possibilities of the system, combined with the contribution from the Meadows Center and WVWA, made the decision to go with the One Water system a no-brainer,” York says.

Reducing demands for potable water

Potable water used by the school comes from wells that have a hydrologic connection to Jacob’s Well. In the past, heavy withdrawals in the area have led to decreases in flows from the spring at Jacob’s Well. “It’s very important to preserve the flows at Jacob’s Well for the health of the creek and watershed and the spring,” Dornak says. “For any new construction project like this, especially a school that can use a lot of water, we’re looking for water efficiencies in a very big way,” he says.

To this end, the school was outfitted with water-efficient fixtures. But that was only the beginning of efforts to reduce the volume of potable water required by the school. Rainwater harvesting, an increasingly common practice in the Hill Country, was integrated into the project design, providing a source of nonpotable water for use onsite to flush toilets. A small portion of the harvested rainwater is used to irrigate landscaping. In this way, the school needs potable water only for drinking and handwashing.

Rainwater collected from the school’s 76,000 sq ft roof flows by gravity either to the main 200,000-gal storage tank or to an 11,000-gal “showpiece” tank located near the school’s front entrance, says Ted Davison, a principal at the architecture and engineering firm O’Connell Robertson, which served as the lead designer on the project. Doucet & Associates provided civil engineering services, while AG|CM, Inc., was the general contractor.

Most of the rainwater collected from the school’s 76,000 sq ft roof flows by gravity to the main 200,000-gal storage tank shown here in the foreground. The tank in the background stores water for use in the event of a fire. (Photo Credit: Wimberley Independent School District)

“All the rainwater that falls onto the building is captured and is used either for flushing fixtures or for irrigation,” Davison says. The rainwater harvesting system also collects condensate from the air conditioning units on the school’s roof, adding as much as 600 to 1200 gal/d depending on weather conditions. “That’s pure water,” he says. “It’s super clean.”

Made of corrugated steel bolted in sections, the rainwater tanks have a plastic liner inside to make them waterproof. Each tank rests on a concrete slab that was structurally reinforced to accommodate the weight of the water. Before it is pumped back to the school for toilet flushing, the harvested water undergoes filtration in bag filters and disinfection by means of ultraviolet light. “We add a dye to it so it’s colored and you know it’s reclaimed water and not drinking water,” Davison says.

To date, the system for collecting and treating rainwater and condensate before use in toilet flushing has worked “flawlessly,” Dornak says. 

Reuse to the rescue

To conserve water supplies even further, all graywater and blackwater from the school are treated onsite and beneficially reused to irrigate a new athletic field constructed on the property. The onsite treatment system represents the most significant change made to the campus as a result of the shift in focus toward greater inclusion of One Water features.

Originally, the Wimberley ISD had planned to connect the school to a centralized wastewater collection system, which would have required constructing a lift station and several miles of sewer line. Expected to cost on the order of $500,000, this plan represented “one of the most expensive components of the traditional construction path” that the district had planned to undertake, Dornak says.

As promoters of the One Water concept, the Meadows Center and the WVWA saw an opportunity. “Our goal was to build [an onsite beneficial reuse] system that was under [$500,000], save them money there, and with any additional savings put in green infrastructure,” Dornak says. 

The right system for the site

The project team selected a recirculating packed bed filter system for onsite reuse. Unlike a traditional activated sludge package plant, the recirculating packed bed filter system is much better suited to handle the episodic, varying loadings from the school, says David Venhuizen, an Austin-based professional engineer who specializes in integrated water resource management and who designed the onsite treatment system for the project. “This kind of technology deals with that just fine,” Venhuizen says. 

The recirculating packed bed filter system was sized for a nominal design flow of 5000 gal/d. Inside the system, influent from the school enters a holding tank before being pumped to the top of one of three filter beds, two of which recirculate their filtrate for further treatment. Filtrate from the third bed enters a final effluent holding tank before being pumped to an 11-zone drip irrigation system used to irrigate the turf of the athletic field. The irrigation system is located below the ground’s surface to ensure maximum efficiency.

Because of the episodic nature of the loadings from the school, the system is set up to continuously recirculate flows when influent levels drop significantly or cease altogether, such as at night or on weekends. As a result, the “filter beds are always loaded steady state,” Venhuizen says. “That’s what the biology likes best.”

Equipped with geotextile media to promote the attached growth processes used to treat the wastewater, the system selected for the project has a greater void volume compared to a traditional recirculating gravel or sand filter. As a result, “you can have a heavier area loading rate on the filter bed,” Venhuizen says, facilitating the use of a smaller filter bed size.

Among its other benefits, the recirculating packed bed filter system does not require a lot of energy to operate. “It doesn’t take any power to run the treatment process,” Venhuizen says, because that is performed by the microorganisms in the filter media. “Water flows down through [the system] by gravity,” he says. “The only thing you need power for is to get the water to the top of the filter bed.” In the event of a power outage, the microorganisms “just sit there patiently waiting for the power to resume and the water to start flowing again, and then they pick right up,” Venhuizen says.

Thanks to the use of the onsite treatment system, the Blue Hole Primary School is not connected to a centralized wastewater collection network. “These are the types of systems that we would like to see developed and implemented more throughout the Hill Country to create more of a distributed infrastructure,” Dornak says.

During the planning and development of the new school, significant thought and effort were devoted to addressing issues related to operation and maintenance of the various One Water components, especially the onsite treatment and reuse system. “That was a big point of concern for the district,” Dornak says. To allay such concerns, the Wimberley ISD contracted with an operator to oversee the system for the first two years and train district staff on how to operate and maintain it.

Initially, the onsite treatment system experienced “several early disruptions,” Dornak says. The problems likely resulted from contaminants overwhelming the filtration system during startup, he notes. In response, the project team cleaned out the tanks and filters and resumed operation of the system. “It has been running smoothly since February,” Dornak says.

Dispersed green infrastructure

Stormwater is managed onsite by a mix of green infrastructure practices as well as enhanced retention ponds that are designed to capture runoff and return it below ground. Permeable pavers, rain gardens, and vegetated swales also help to infiltrate stormwater. “We want that developed site to act like it would in an undeveloped state,” Dornak says.

Pervious pavers are one of several green infrastructure elements that are designed to capture and infiltrate stormwater onsite. (Photo Credit: Wimberley Valley Watershed Association)

“One of the big selling points as well is that we were able to reduce the size of the retention pond that was in the original engineering plans by dispersing the green infrastructure throughout the site,” Dornak says. “So there’s more available land for the school to use, for the kids and development, and less of a giant pond to capture stormwater per city and state requirements.” 

By dispersing the green infrastructure throughout the site, the project team reduced the size of the planned retention pond, freeing up space onsite for other uses. (Photo Credit: Wimberley Valley Watershed Association)

To enable the project to include more green infrastructure than was originally planned, the WVWA secured a $250,000-grant from the Harry L. Willett Foundation.

Demonstrating One Water

Educational signage will be added to the green infrastructure. “We hope for this to be a demonstration to the community and the teachers and students there on the value of managing stormwater for water quality,” Dornak says.

In keeping with the school’s educational mission, the interior of the facility was designed to highlight the building’s many One Water components. “Multiple areas in the school include art and visual and digital displays of the One Water concept,” Davison says. “We opened up a plumbing chase to show the kids how water comes into the plumbing fixtures,” he says. Color-coded pipes indicate which ones contain potable water, reclaimed water, and the wastewater that is to be treated onsite.

This interior window enables students to view the school’s plumbing fixtures, which are color-coded to indicate which ones contain potable water, reclaimed water, and the wastewater that is to be treated onsite. (Photo Credit: Wimberley Independent School District)

To promote awareness of rainwater harvesting, the school’s library includes a clear pipe that is connected to the rainwater collection system. “When it rains, you can actually see the rainwater being captured,” Davison says. 

Connected to the rainwater collection system, this clear pipe in the school’s library enables students to see the system in action. (Photo Credit: Wimberley Independent School District)

Meters were installed throughout the school to quantify how much rainwater is harvested and to track water use onsite. “We’ll be gathering data to share with the school on total volumes of water that we capture and consume,” Davison says.

Saving water and money

The water savings are expected to be significant. Only about 20 percent of the school’s water use is expected to involve potable water used for drinking and handwashing. And that water, of course, will then be put to additional use. “All the water that enters the school from the city water source ultimately stays on the site,” Davison notes.

As a result of its many One Water strategies, the Blue Hole Primary School is expected to use approximately 90 percent less water than a conventional school of its size, Dornak says. By reducing water consumption and avoiding sewer fees, the school will accrue an estimated annual cost savings ranging from $29,000 to $48,000. Over time, such savings will really add up. 

“The idea is that the school and the community are going to get a payback economically from all of these additions that we’re making,” Dornak says. “We expect that to be somewhere between $800,000 and $1 million over the next 30 years.” During this timeframe, the project will conserve 237 acre-feet of groundwater.

Exemplifying what is possible

Aside from its educational benefits to the community, the Blue Hole Primary School illustrates how thoughtful, responsible development can conserve and manage water resources in a real-world setting. What makes the project noteworthy, Davison says, is its use of so many One Water approaches in a manner that makes sense both economically and environmentally. “Pulling them all together on one project, so many concepts all in one place, that is unique,” he says. 

That said, the project at times resembled a balancing act. “We had to balance those ideas into what we could afford, what could be put into the school in a practical, maintainable way and satisfy everybody’s vision for what this needed to be,” Davison says. “I think we’ve done a great job with that.”

Ultimately, the school exemplifies what is possible, Dornak says. “What we’re trying to do with this school is develop this proving ground for One Water and how [the concept] can work for other developments and communities across the Hill Country,” he says. “We wanted the technologies and the systems there that we feel are the best for new developments.”

The school began attracting positive attention almost as soon as it opened. In September 2020, the Texas Water Development Board awarded the Wimberley ISD its Texas Rain Catcher Award, an honor bestowed annually to Lone Star state entities deemed to have displayed excellence in rainwater harvesting. The award was given in the educational/government category.

Blue Hole Primary School offers lessons for Wimberley, the Hill Country, and beyond, Davison says. “It’s showing the community what can be done on water,” he says. “In the Hill Country, [One Water] makes a lot of sense. In areas that are getting less rain and water supply is in demand, and the cost of water goes up, this is going to make more and more sense.”