A team of water engineers and artists has presented the final design for solving Nine Mile Run's storm water runoff problems. More than two years in the making, it calls for a $2.5 million water detention system that combines art elements and environmental education in a public water park.

About 30 people turned out yesterday to watch a PowerPoint explanation of the problem and a computer simulation of the solution at the community center in Summerset at Frick Park.

The Watershed Association has to raise the money to turn what is now a dead-end trolley spur off Braddock Avenue in Swissvale into a system that would catch and detain storm water runoff for the public to view from a lookout platform above.

That spur now ends at the start of Frick Park's Braddock Trail, which is fenced off in front of what used to be the Center for Creative Play. The fence would be a park entrance, which would be part of a long public plaza also using water, including a canal running down steps.

A computer simulation of a runoff event shows the water being rerouted into an overflow spout that gushes it down into a water divider that pushes it into spillways with deeply textured crevices. The water is gushing, like from a spigot turned on to maximum, but when it lands it is toyed with by the up-and-down design of the spillways and drop pools.

The effect is that storm water is detained long enough to let the stream take it in a more orderly way than the frenzied overflow into combined storm/sanitary sewers.

Atelier Dreiseitl, an internationally renowned landscape architecture firm in Uberlingen, Germany, and Cahill Associates, experts in watershed management in West Chester, Chester County, have been working with the watershed association and residents to create a public attraction that also tames "the flooding energy of the stream," as the principals, Herbert Dreiseitl and Thomas Cahill, described it in the foreward of their report.

For all the good it could do Nine Mile Run, the project underscores a much costlier need to remedy the toxic effluent coming from increasingly degraded networks of lines and pipes under the watershed's streets, said Mr. Cahill.

The design team and the watershed association have monitored the water, which Mr. Cahill called "pretty scary" despite costly remediation work the city has done in the park.

"It's so inviting to children and dogs to play in," he said, "but they should not."

In the association's final design report, he wrote that the remedy requires the will of the government and "every resident of the watershed whose runoff conveys pollution from sidewalks and streets to the underground stream."

Brenda Smith, executive director of the association, said the motivation should be strong considering the investment public and private entities are making in water recreation for Pittsburgh's revitalization. Nine Mile Run empties into the Monongahela River.