Confluence Park

Confluence Park is a living learning laboratory designed to inspire people to gain a greater understanding of Texas ecotypes and the impact of urban development on our watershed. Located along the edge of the San Antonio River, Confluence Park is part of the country’s largest urban environmental restoration project and is an inviting gateway to running, biking, and paddling trails.

The client, the San Antonio River Foundation, is dedicated to making the San Antonio River Basin a vibrant cultural, educational, ecological, and recreational experience. The foundation tasked the design team with transforming a former industrial laydown yard into a one-of-a-kind outdoor educational center to serve the San Antonio community.

The design solution was inspired by the client’s stated project directive: to create a park that will educate the community about native Texan ecological systems, river dynamics, watershed protection, and the importance of conserving natural resources. The park is located at the confluence of the San Antonio River and San Pedro Creek, and this idea of confluence—of water, ecology, and culture—is ingrained in every aspect of the design. Large gestures like the shaped land of the park represent the convergence of five regional landscape ecotypes in the south Texas region, while more specific details like the pavilion “petals” are inspired by the plant structures that funnel dew and rainwater to their roots. Even the lines in the design of the paver patterns are reminiscent of the flow and confluence of waterways.

“This project is both architecturally functional but also just a beautiful space where I’d want to be in.”—Jury comment

The $12.8 million park’s elements seek to highlight urban ecology and development, including 3.5 acres of native planting, a 2,000 sq. ft. multipurpose building, a 6,000 sq. ft. central pavilion, and three smaller “satellite” pavilions dispersed throughout the park. The central pavilion, made up of 22 concrete “petals,” forms a network of vaults to provide shade and direct the flow of rainwater into an underground cistern used for the park’s sewage conveyance and irrigation needs. Each petal was cast on-site using a modified tilt-up construction technique and digitally fabricated fiberglass composite molds. They were then lifted into place in pairs to form structural arches. The multipurpose Estela Avery Education Center building houses park amenities and a classroom/event space that opens to the pavilion, blurring the lines between indoors and out. A green roof provides thermal mass for passive heating and cooling, while a solar photovoltaic array is intended to produce 100% of the park’s energy needs. This low-lying building was designed as a dynamic juxtaposition to the pavilion—the board-formed concrete walls are highly textured compared to the smooth, fiberglass-formed petals, and the more geometric forms contrast with the curves of the pavilion.

Confluence Park demonstrates how the conversion of a former blighted industrial laydown yard into a public amenity can showcase sustainability concepts, low-impact design, and thoughtful place-making, underscoring the importance of this small facility’s forward-facing impact on its citizens, visitors, students, and society. 

Confluence Park’s DNA is defined by a spirit of inclusion and collaboration. The conversion of a former blighted industrial laydown yard into a public amenity, designed to be sustainable and low impact and with thoughtful place-making in mind, has had a deep and forward-facing impact on citizens, visitors, students, and society. While the client’s original intent was to provide a river access portal delivering exceptional outdoor educational programming, the project has become something bigger—a destination for the region and San Antonio community. Since opening in March 2018, the park has welcomed more than 32,000 students and registrants from over 350 programs, 70 schools across 11 districts in Texas, and 75 nonprofit partners.

See Fig.1 Design for Equitable Communities.

To support equitable outreach, representatives from the San Antonio River Foundation went door to door updating citizens about the park, leading to overwhelming enthusiasm about the project. Since completion, Confluence Park provides an important free access point on the southside of San Antonio for various amenities along the 16-mile stretch of the Mission Reach and the 140-mile Howard Peak Greenway Trails System. These amenities include uninterrupted connections to the downtown Riverwalk, the Pearl district, and various greenways, trails, and cultural destinations.

Design intent

Who does the project serve? Identify the stakeholders who are directly or indirectly impacted by the project.

A $1 million endowment has been established to offset the cost of school transportation to the park, substitute teachers, and providing specialized educators and speakers at park events. The multipurpose room and the pavilions are available by reservation, free of charge, to schools and nonprofits for educational use. Confluence Park’s community-focused, collaborative ethos, built into the owner’s requirements, has already made its mark: Since opening in March 2018, the park has welcomed more than 32,000 students and registrants from over 350 programs, 70 schools across 11 districts in Texas, and 75 nonprofit partners.

Describe the stakeholder engagement process over the course of the project.

This project went through several iterations and held multiple public meetings prior to the design team’s involvement. These initial meetings were well attended, yet park neighbors still wanted existing fences to remain. Our design team conducted two public meetings that were not well attended. We felt this was due to fatigue and the community’s assumption that nothing would ever happen. To better engage with the park’s direct neighbors, client representatives went door to door updating citizens about the park plans. This engendered overwhelming enthusiasm for the project, which led to the addition of two entry gates and the removal of the fences.

Identify project goals that support equitable communities and describe how those goals were developed.

Confluence Park is part of the country’s largest urban environmental restoration project. Along the Mission Reach, a 16-mile stretch of the San Antonio River, a riparian woodland ecosystem connects the downtown Riverwalk and UNESCO Heritage Sites to the underserved communities of the southside via a network of pedestrian trails. The project’s primary goals were to create a civic space for everyone that leveraged the park’s important location and to promote and encourage the conservation, stewardship, restoration, preservation, and enjoyment of the land and water resources of the San Antonio River Basin, which is the client’s mission.

Describe the project team's explorations or design strategies that respond to the above-stated goals.

A pivotal moment in the design conversation occurred after the design team had presented the first concept for the pavilion, which was a shell structure that handled rainwater in a more traditional way, like an umbrella, directing the water to the edges. One of the clients said they wanted us to create a place where people would say, “Hey, it’s raining, let’s go to Confluence Park!” This led to the design of a pavilion that truly celebrated the collection of rainwater and engaged park visitors in learning more about the stewardship of the region’s water, land, and watershed.

Describe stories or evidence that demonstrate how the project successfully contributes toward more equitable communities.

Since opening in March 2018, Confluence Park has hosted multiple educational summer camps that have engaged the community on water conservation and watershed protection. In the summer of 2018, San Antonio Visual Artist Katie Pell led a summer camp where children created visual art inspired by the San Antonio River. A design team member taught students how the concrete petals collect and filter rainwater and feed the plants in the park. The children learned how many gallons of water it takes to flush toilets and fill up bathtubs, directly relating to activities at home.

Every community is unique, and every project has unique has unique opportunities to respond to issues of equity and inclusion. Describe any exemplary practices or outcomes for this project.

Located in one of the most economically disadvantaged communities in San Antonio, Confluence Park’s design supports equitable communities by providing access to educational and recreational amenities and serving as a gateway to 16 miles of the Mission Reach and its shared hiking, bike, and paddle trails. Vehicle and bicycle parking amenities are accessible to the community free of charge. The design team worked with B-Cycle to install a public biking station on-site so that the community can access the nearby trails and cultural destinations, such as the five 18th-century Spanish missions that stretch along the Mission Reach trail network. This trail system then connects to the greenway trail network, which provides 140 miles of hiking and bike trails in and around the San Antonio area.

The park also supports free programming for events that involve health, well-being, and environmental stewardship. Some of these free events include the twice a year tree giveaways, yoga classes under the pavilion every Sunday morning, Bachata dance classes, and an annual monarch butterfly and pollinator celebration.

A $1 million endowment has been established to offset the cost of school transportation to the park, substitute teachers, and providing specialized educators and speakers at park events. The multipurpose room and the pavilions are available by reservation, free of charge, to schools and nonprofits for educational use.

Confluence Park’s community-focused, collaborative ethos, built into the owner’s requirements, has already had an impact: Since opening, the park has welcomed more than 32,000 students and registrants from over 350 programs, 70 schools across 11 districts in Texas, and 75 nonprofit partners. 

Confluence Park is a living learning laboratory designed to inspire people to gain a greater understanding of Texas ecotypes and the impacts of urban development on our watershed. An inviting gateway to running, biking, and paddling trails, the park is located at the confluence of the San Antonio River and San Pedro Creek. This idea of confluence—of water, ecology, and culture—is ingrained in every aspect of the design. Large gestures like the shaped land of the park represent the convergence of five regional landscape ecotypes in the south Texas region, while more specific details like the pavilion “petals” are inspired by the plant structures that funnel dew and rainwater to their roots. Even the lines in the design of the paver patterns are reminiscent of the flow and confluence of waterways.

The park serves as a teaching tool that aims to inspire people to become more involved with the river, practice environmental stewardship, and gain a greater understanding of the ecotypes of south Texas. A clear demonstration of the five ecotypes found in the south Texas region is strategically placed in the park to address the hydrology of the region relative to the hydrology of the site.

Explore site ecotypes in Fig. 2 Design for Ecosystems.

Design intent

How does the design minimize negative impacts on animals?

This project transformed a former industrial laydown yard into a fully restored landscape of native plants. This landscape acts as a teaching tool while supporting biodiversity by providing animal habitat. To support bird safety, large pivoting wood-slat doors protect the large sliding-glass doors of the education building from bird strikes. Many of the plants provide nectar sources and larvae hosts for local and migrating butterflies. San Antonio is located in the monarch butterfly’s migratory flyway, and the pollinator plants of the park support the city’s Monarch Pledge.

How does the project support biodiversity and improve ecosystem services?

Confluence Park supports and exhibits the efforts to restore the riparian zones along the San Antonio riverbanks to predevelopment biodiversity levels. A recent avian study found that a bald eagle is living along this section of the river. When birds of prey, such as bald eagles, are found in habitats, it demonstrates that the hierarchy of the food chain is strong and stable. Texas Parks & Wildlife Department has also found that the Texas state fish, the Guadalupe bass, which left the San Antonio River a decade ago, is now well-established.

Metrics

0% of site area was vegetated (landscape or green roof) pre-development.

99% of the site area is vegetated (landscape or green roof) post-development.  

There was a 100% increase in vegetated area, post-development.  

100% of the vegetated areas are planted with native species. 

Located along the edge of the San Antonio River, Confluence Park is a pavilion and education center brought to life by rainwater. The building and landforms tell the story of the water cycle on the site and demonstrate strategies for watershed protection and restoration. Using the biomimetic principle of looking toward nature for inspiration, the pavilion geometry is inspired by plants’ use of doubly curved fronds to cantilever and collect rainwater and then redirect it to the root stem. The modular system of concrete “petals” forming the pavilion was developed to collect rainwater and funnel it to the petals’ columnar bases and into a central underground catchment basin.

Supporting low-impact development strategies and watershed protection, all pathways and parking areas are permeable. The catchment basin manages all stormwater for 100-year flood events. Collected rainwater is filtered through alluvial soils and up to 100,000 gallons of water is held below the surface, preventing any contaminated runoff from entering the San Antonio River. This stored water is then used for sewage conveyance and irrigation.

Explore how the pavilion geometry uses the biomimetic principle in Fig. 3 Design for Water.

Design intent

Describe how the project's stormwater and potable water strategies contribute to site and community resilience.

The primary source of pollution for the San Antonio River is stormwater runoff. The San Antonio River Foundation, which teaches programs about watershed protection at Confluence Park, wanted this park to demonstrate resilient strategies for stormwater management. The site manages all stormwater for 100-year flood events. Low-impact development (LID) strategies, such as pervious parking and landscape contouring, are utilized to direct and capture stormwater on-site. Confluence Park’s LID systems create a functioning, appealing site that treats precipitation and stormwater as a resource rather than a waste product.

Describe the quality of the water that runs off the site.

The project is designed so that no water will run off the site unless the storm exceeds a 100-year event. When this does happen, the native San Antonio River ecosystem restoration plant palette along the riverbank and in the park help prevent erosion and filter pollutants. Sustainably preserving and continuously improving water quality beginning at the Mission Reach offers flood protection and promotes healthy ecological and hydrological functions for over 200 miles downstream.

Metrics

Water use intensity (gal/sf/year)

Benchmark: 0.6

Predicted: 21.6

Measured: 3.4

Reduction in potable water use (from benchmark)

Predicted: 3657.9%

Measured: 501%

Total annual water demand met using potable sources

Predicted: 19.2%

Measured: 5%

100% of stormwater is managed on-site. 

Located along the edge of the San Antonio River, Confluence Park is part of the country’s largest urban environmental restoration project and is an inviting gateway to running, biking, and paddling trails. The revitalization of the park’s area transformed an underutilized plot of land into an economic engine for the surrounding area. The concrete material was selected to be durable and resilient—for a 100-year building—while the landscape is reflective of native plantings and regional ecotypes, resulting in minimal maintenance for the owner. The park is unstaffed and publicly accessible, and energy and water costs are offset through thoughtful design strategies.

Aside from nonprofit community engagement, the park has also become a sought-after regional venue for weddings, corporate and cultural events, parties, concerts, and educational seminars, which all contribute valuable operating revenue to the San Antonio River Foundation.

Design intent

How does this project contribute to local and/or disadvantaged economies?

Confluence Park has proven to be a catalyst for thoughtful and equitable development in the adjacent Lone Star neighborhood. During construction of the park, the design for an 81-unit mixed-income apartment complex was approved by the historic district, and construction is now complete. The project features 14 units that are rented at market rate, while the rest of the units are rent-controlled to support the broader community, including lower-income residents.

How did design choices reduce system sizes and minimize materials usage, allowing for lower cost and more efficiently designed systems/structure?

When reviewing cost estimates for the project’s GMP, the specified prefabricated, skid-mounted water filtration system proved to be cost-prohibitive. Instead of value-engineering it from the project, and falling short of project goals, the client tasked the team with finding alternate solutions. The design team reached out to another collaborator for advice on an alternate supplier and discovered the local water filtration company could provide a comparable system, that complied with local codes, at a significant cost savings of around $35,000.

How did life cycle cost analysis influence the project's design?

The conceptual designs for the main and satellite pavilions evolved throughout the course of design. An early concept was a series of petal structures made of wood, steel, and fabric. As the client thought more thoroughly about the project needs and design requirements, a priority was placed on building a durable 100-year structure requiring minimal maintenance that could resist vandalism. Materiality was a key factor in the structure’s durability and longevity, and the design team quickly landed on concrete as it could act as both the structure and the finish.

Cost

$396.26 per square foot 

As the primary energy reduction strategy, the multipurpose building was designed to emerge from the land, allowing the green roof and two sides of the building to utilize thermal mass for passive heating and cooling. The initial intent was to use only fans for comfort and fresh air requirements; however, in the end, mechanical heating and cooling was provided in the classroom space only to control humidity and ensure year-round comfort. To still meet the client’s net-zero energy goals, the design team worked with them to program the thermostat and establish set points for occupied and unoccupied times. Also, a switch was installed along the sliding doors to ensure that the air conditioning would stop running if the sliding-glass doors were left open.

The restrooms are designed to be non-conditioned, and an exhaust fan tied to an occupancy sensor drastically reduces the energy load compared to a baseline building.

The design team worked closely with the client to model the projected use of the building and size of the photovoltaic array to offset 100% of the park’s energy use on an annual basis.

Design intent

Describe any energy challenges associated with the building type, intensity of use, or hours of operation, and how the design responds to these challenges.

The multipurpose room at Confluence Park is designed to be utilized throughout the year. Large sliding-glass doors are designed to add flexibility to the space and capture cool breezes off the San Antonio River. A lesson learned from designing spaces that open up like this is that occupants often leave the air conditioning blasting while the doors are open. Together, the architects and engineers designed a “kill switch” sensor that turns off the HVAC system when the sliding doors are open.

Metrics

Is the building all-electric? Yes.

In its measured usage, including on-site renewables, did the project achieve its 2030 Commitment reduction target (70% reduction by 2015, 80% reduction by 2020)? Yes.

The project's total carbon (embodied + operational) over 10 years in kg CO2e is 239,654.4.

There is a 93% reduction (inclusive of renewables) from benchmark, measured.

58.1% of total energy is derived from renewable sources, measured.

There is a 92% reduction (inclusive of renewables) in operational carbon from benchmark, measured. 

Confluence Park celebrates the outdoors and helps visitors forge meaningful relationships with nature. This relationship is reinforced through biophilic design principles, including looking to nature for design solutions that create comfortable environments. The pavilion forms were designed to shade users while serving as rain-capture elements.

To support and encourage a healthy lifestyle, the River Foundation hosts free athletic community events every Sunday. On the top of a hill overlooking the San Antonio River, in the shade of the pavilion structure, visitors are filled with a sense of wonder and awe, which is one reason the free yoga classes are so popular.

People feel a sense of place at Confluence Park and are drawn to learn more about the purpose of the park and the surrounding river and trails. Part of this connection to place is the intentionally didactic landscape that demonstrates and connects visitors to the beauty of five ecotypes that exist and merge in and around San Antonio.

Design intent

Was a chemicals of concern list or other third-party framework used to inform material selection? If so, how?

Wood was the only finish material used that needed treatment. The products used for finishing the interior and exterior wood were carefully considered. Valhalla Lifetime Treatment was selected for all Eastern red cedar cladding; it is a zero-VOC product made of naturally occurring plant and mineral substances that penetrate the wood fibers to double the lifespan of the wood. Eco Protocote Acri Soy’s clear sealer was used on the interior white oak ceiling. It is a bio-based sealer without toxic solvents or noxious, lingering odors.

Metrics

100% of the regularly occupied area is daylit (sDA 300/50%).

100% of the regularly occupied area is compliant with annual glare criteria (ASE 1000, 250).

94% of the regularly occupied area has quality views.

93% of the regularly occupied area has access to operable windows.

The design goal for maximum C02 meets code. Open air and outside are provided in all of the project’s enclosed spaces.

The unique main pavilion is made of 22 concrete “petals” that form a geometry designed to collect and funnel rainwater. The team considered wood, steel, and fabric for the initial pavilion designs, but concrete offered a thoughtful, resilient solution to achieve the client’s 100-year building goal. Using digitally fabricated, reusable fiberglass molds and a modified tilt-up construction technique, the concrete petals were each cast on-site and lifted into place to form the structural arches. Only three unique molds were needed for the project’s 28 cast concrete petals.

The robotically milled EPS foam used in casting the initial fiberglass molds was either recycled or repurposed by students at a local architecture school. By eliminating interior and exterior cladding, concrete, which served as the structure and finish, also minimizes the use of additional natural resources and adhesives.

Exterior wood-clad pivot doors extend the lifespan of the sliding-glass doors by protecting them from potential vandalism in the public park. The design team chose Eastern red cedar for these doors because it is a locally available, naturally durable material that is often brush cleared and burned on properties in the Texas Hill Country.

See Fig. 4 Design for Resources. 

Design intent

Did embodied carbon considerations inform the design? How?

The primary material used is concrete. Although it is a high-impact carbon material, concrete offered a thoughtful, resilient solution to achieve the client’s 100-year building goal. To help balance out our carbon impact, the building footprint remained small to allow for landscape restoration and carbon capture on-site. Using the Build Carbon Neutral tool, we estimate that the soil of the installed native landscape will offset 87% of the building and petals’ embodied carbon A1-A3 emissions in 20–50 years.

Did the idea of circularity/circular economy inform the design? How?

The landscaping on the three-acre site demonstrates circular economy by incorporating efforts to regenerate nature. The site transformed from a utility laydown yard to an environment with 134 different native Texas plant species. The low-water native plantings are resilient to the local climate. Collected rainwater is used to irrigate the plants, creating a closed-loop water system on-site. Each landscape area is designed to educate visitors about the importance of native landscaping and inspire others to do the same.

Describe any special steps taken during design/construction to make disassembly, deconstruction, or reuse easier at the building's end of life.

With the roof and three sides of the building under a planted native landscape, the multipurpose building utilizes thermal mass to regulate the indoor air temperature so visitors can stay comfortable without the use of air conditioning. As temperatures rise, these spaces will still maintain a good level of comfort with relatively small energy needs. On top of the building’s green roof, there is a solar photovoltaic array that is intended to meet the energy needs of the project. Though this project is currently net metered, it could be converted to on-site storage in the future.

Metrics

0% of project floor area was reused or adapted from existing buildings.

Was embodied carbon modeled? Yes.

22 kgCO2e/sf is the project's embodied carbon intensity.

None of the installed wood is FSC certified. 

The most resilient aspect of this project relative to climate change is the landscape, which is planted entirely with native species that, once established, have minimal water needs.

With the roof and three sides of the building under a planted native landscape, the multipurpose building utilizes thermal mass to regulate the indoor air temperature so that visitors can stay comfortable without the use of air conditioning. As temperatures rise, these spaces will still maintain a good level of comfort with relatively small energy needs. On top of the building’s green roof, a solar photovoltaic array is intended to meet the energy needs of the project. Though this project is currently net metered, it could be converted to on-site storage in the future.

Design intent

In what ways does the design anticipate climate change over the life of the building?

Anticipating a future when municipal water sources may be scarce, Confluence Park is designed to reuse 100% of the rainwater collected on-site. Reclaimed rainwater is used for non-potable uses, such as irrigating the plants during their establishment period and for flushing the toilets in the park after the water is filtered. The goal is for the building to function on as little municipal water as possible, as allowed by today’s building codes.

How does the design anticipate restoring or adapting function in the face of stress or shock, such as natural disasters, blackouts, etc.?

In February 2021, San Antonio experienced Winter Storm Uri, where 69% of Texans lost power and 49% of residents had disruptions in water service. Thirty-one percent of residents experienced water damage to their residences. The passive design of the planted roof and mass wall at Confluence Park protected all of the restrooms’ plumbing systems. The park didn’t experience any broken pipes, or further maintenance of the plumbing system, amid the many days of below-freezing temperatures.

Metrics

Research Score: 100

Resiliency Score: 33

The building can be used as a safe harbor to support the community during a crisis.  

Through passive sustainability, the building can function for 8,760 hours. The project is designed to operate passively throughout disruptions to energy and water resources. 

A common lesson learned from past projects is that HVAC is one of the largest drivers of energy consumption. To reduce cooling needs, the multipurpose building at Confluence Park was originally designed to have no mechanical cooling and only rely on passive strategies. For example, the sliding-glass doors on the west side can be opened and closed.

However, the client opted to add a two-ton air conditioning system for the main space to ensure a comfortable environment. Despite the addition of the AC, the energy model predicted that the project’s largest energy use would come from the water filtration and the irrigation system during the plantings’ establishment period.

To achieve the goal of net-zero energy, a 10kw array was installed. To track the impact that the AC and other elements would have on the building's energy use over time, post-occupancy energy (POE) monitoring was installed. The design team covered the cost of the monitoring system’s subscriptions to allow for the continued relationship between design team, owner, and operators of the project.

Design intent

What lessons learned through this project have been used to improve subsequent projects?

Demonstrating that passive design strategies could keep the building comfortable was challenging. For future projects, we would seek better tools to quantify thermal mass as an effective tool for cooling. The post-occupancy energy lessons have influenced future projects: We have a database showing how all buildings are performing and can compare lessons learned. Our firm has shared lessons learned on POE from Confluence Park and other projects with the architectural community by lecturing at AIA national, local, and internal office events with the hope that other projects can reduce the consumption of energy for a more sustainable future.

If a post-occupancy performance testing was conducted, describe the process and outcomes.

Through the post-occupancy energy evaluation, the design team saw that the AC was accounting for 46% of total energy use. Although the building was programmed to shut the AC off and use temperature setbacks, the thermostat programming allows users to “hold” setpoints, causing the AC to remain on. A lockbox was installed on the thermostat that occupants can access to change temperature temporarily. In addition, energy production was reduced by 30% when plexiglass was installed over the panels after they were vandalized. These findings have led to ongoing attempts to optimize energy use and meet the net-zero goal.

Metrics

Post-Occupancy Evaluation Score: 60

Transparency Score: 60

Commissioning Score: 40

Feedback Score: 100 

Year of design completion: 2016

Year of substantial project completion: 2018

Gross conditioned floor area: 1,003 sq. ft.

Number of stories the building has: One

Project site: Previously developed land

Project site context/setting: Urban

Annual hours of operation: 5,110

Site area: 149,525 sq. ft.

Cost of construction, excluding furnishing: $3,650,873

Total annual users: 9,000 

Engineer – Civil: Pape Dawson

Engineer – MEP: CNG Engineering

Engineer – Structural: Architectural Engineers Collaborative

General Contractor: SpawGlass

Landscape Architect: Rialto Studio

Lighting Design: Mazzetti

Pavilion Designer: Matsys

Petal Formwork: Kreysler & Associates 

Katie Ackerly, AIA, Chair, David Baker, Oakland, Calif.

Julian Owens, Assoc. AIA, Jacobs, Arlington, Va.

Seonhee Kim, AIA, Design Collective, Baltimore

Avinash Rajagopal, Metropolis, New York