Sourced from ConstructConnect’s Daily Commercial News
Think of the growing medium specified for green infrastructure as analogous to an iceberg.
“There is a lot that happens below the surface that people don’t see,” said Helle Brodie, landscape architect and president of Brodie & Associates.
Brodie, a speaker on a panel examining what it takes to produce healthy engineered soils for green infrastructure, said success comes when all the players in a green infrastructure project are on the same page.
That includes the owner who must spend “extra money,” the design team, the project manager to make sure everything is built correctly and the contractor responsible for the installation, she told a seminar audience at the Grey to Green Conference in Toronto recently.
Some green infrastructure projects go off the rails because the soils installed by a contractor do not meet the landscape architect’s specifications, she said, citing an example in which a contractor provided sandy loam topsoil as specified but the soil “was filled with salt.”
When she asked the project manager to leach the soil prior to use, she was told, “We don’t have time for that. We are way beyond schedule.”
The result was that the planted native grasses “didn’t establish well,” Brodie said.
In another case vegetation didn’t establish itself in a bioswale — a landscape feature designed to filter out debris and pollution from surface runoff water — because of poor installation. The result was that stormwater caused soil and mulch erosion plus the loss of seeds and some of the plants.
“We had great soils but construction methods weren’t great,” she explained.
Another concern, she said, is when drainage and base preparation specifications are not followed.