Replacing the old Duke Diet and Fitness Center on Trinity Avenue with a pollution-controling wetland got a friendly reception from the Open Space and Trails Commission last week.

The commission took no official position on the “South Ellerbe Wetland Concept Plan,” as the city has dubbed the idea. The focus last week was not on pros and cons of the wetland itself but on ways to make the wetland a public amenity as well as a stormwater filter saving taxpayers as much as $20 million.

Responding to a presentation by Paul Wiebke, the city’s acting stormwater manager, commissioners emphasized some concerns:

• safety – keeping children from falling into deep water;

• pest control – discouraging mosquitoes, mice, geese and other critters that would find marshland attractive

• maintenance – keeping the wetland clear of trash swept in by runoff from the 485 urban acres that drain through the 9-acre site and currently send pollutants on toward Ellerbe Creek and Falls Lake.

Since the city began looking into the wetland idea in 2011, some residents have argued instead for buying the 20,000-square foot building and renovating it, with its gymnasium and swimming pool, for a community center.

Engineering studies, though, found that an effective wetland, to filter pollutants out of stormwater before they go downstream, requires the entire site. Wiebke said the building, built as a YMCA in 1955, also has asbestos and lead issues.

Some commissioners pushed for preserving and moving part of the building, and perhaps elevating it, to use as an environmental education center. The idea was left open, but the group held back from recommending it without more research on the practicalities involved.

“We have to continue to look at the bigger picture,” Wiebke said. Durham is facing state regulations for cleaning and protecting Falls Lake will require Durham to spend from $320 million to $370 million in mitigation for the Ellerbe Creek watershed alone over the next 10 to 15 years. Because of its location, receiving runoff from much of downtown Durham and the Trinity Park residential section, a wetland at the Diet and Fitness site could accomplish the same reduction as 15 or more smaller installations spread along the stream.

Even so, Wiebke said, the wetland would be just one step the city needs to even get close to compliance with the two-phase Falls Lake Rules: one phase, difficult and costly in itself, takes effect July 6; the second, which could be far more difficult and expensive, in 2026.

“We’re going to need every tool we have,” he said. “And we still won’t reach the target.”