It seems an unlikely place for a performance: three deep, concrete trenches, aqua- and ochre-streaked walls, a slightly ribbed, concrete ceiling.
Ancient graffiti is scrawled along the trench walls - 1977, ZEP, ROO, MIK, JIM. Decayed paint is largely scraped away. A turbulent river roils just outside arched windows.
Yet, this is the place, the old Kelly Pool beneath the historic Fairmount Water Works, unused and deteriorating since it was swamped by Hurricane Agnes in 1972, where one of the city's newest and least likely impresarios will present the world premiere of a cantata.
The Philadelphia Water Department has commissioned Tributaries: A Modern Cantata for the decaying pool house and hopes the Saturday-afternoon-only performance will be the first step in an effort to bring Philadelphians back to this once-popular place.
"Innovation is part of the legacy of the Water Works," said executive director Karen Young. "As much has happened in this complex over the centuries as has happened over cities in the same period of time. It's one of the spaces that the public needs to see again."
Young was heartened last summer by a successful performance at the complex below the Philadelphia Museum of Art on the east bank of the Schuylkill. The Hidden City Festival production showed Water Department officials the pool house could be used theatrically with success.
Young and Victoria Prizzia, head of Habitheque, an installation and design firm working with the department's interpretive center, put a team together to focus on how to expand the reach of the Water Works and actively use the largely forgotten pool area below ground level at the north end of the neoclassical complex.
The Water Works, built in 1815, is a National Historic Landmark that once pumped water across the burgeoning city, attracting visitors like young British writer Charles Dickens, who marveled at its architecture and technology. It shut down in 1909.
In 1911, the Philadelphia Aquarium opened within the Water Works facilities, eventually becoming one of the largest aquariums in the world. When it closed in 1962, the Kelly Pool was built, utilizing part of the aquarium space, and it was used by competitive swimmers and Philadelphia School District students. Ten years later, Hurricane Agnes forced its closure.
The concrete pool house, out of use since, is beginning to show signs of life. Since summer, Young and Prizzia's team has had a light show designed for the space, and composers Will and Brooke Blair have created a water-themed sound show using four speakers.
In recent months, seeing the light move in waves across the ceiling, infusing the cavernous space with something flickering and otherworldly, and listening to the Blairs' murmuring sound piece seemed to transform thinking about the space.
During a weekend of discussions on the subject, someone on the design team mentioned the word opera, Will Blair recalled. Everyone took immediate notice.
"You could see this space transformed into something other than just an empty pool," Blair, 34, said while standing in the empty pool this week. "The word opera was thrown out, and we jumped on it. It's one of those gigs you just don't get every day."
Blair, who is managing this production, said he immediately thought of friend and colleague Craig Hendrix, 32, a composer, performer, and founder of the Agave Opera Company, a small group just getting off the ground.
Hendrix was instantly interested.
"The room, right away, was the first note of inspiration, coming here and seeing the space," he said. "The Schuylkill is directly behind these windows, and, acoustically, it's a pleasant space. . . . That and the Water Works being what it is was really the genesis [of Tributaries]. Where the performance and the space meet is what might be the most appealing for audiences, the juxtaposition of an atypical venue with a traditional approach to composition."
Hendrix composed Tributaries, a 30-minute piece for three singers and small orchestra. The whole project will cost about $15,000, Prizzia said.
The orchestra pit for eight musicians will be in one lane (one of the concrete trenches) of the old pool. The audience will be seated in another.
The performance will begin at 4 p.m. The singers will be on platforms in front of the arched stone windows; behind them, the river will slowly dissolve into night.
Each singer will take charge of a movement; all will then join in chorus for Tributaries' fourth and final movement. Hendrix said the first three movements represent small, upstream creeks, the fourth their merging with the Schuylkill. It is, he said, "a vague narrative."
"Each of the singers will take on the voice of someone who would have had some interaction with the tributary at some point in history," he said. "For example, we have a civil engineer who would have been charged with building dams and shaping the creek so civilization could be built. There's no overarching story line for the whole piece."
Young hopes Tributaries is only the first of a series of performances and other events that will attract new audiences to the Water Department's Interpretive Center at the Water Works. The center, open for 10 years, draws about 60,000 visitors a year - a far cry from the million or so who used to visit the aquarium.
Beyond that, discussions are underway about how to renovate and reuse the entire space below ground level. Performances would become a regular feature of a space that once housed the turbines that quenched thirsts from Fairmount to Kensington and South Philadelphia.
"We are trying to activate the space," Young said. "I want to find as many ways as possible to reengage the people."
Tributaries: A Modern Cantata
4 p.m. Saturday at the Water Works, 640 Waterworks Dr.