The mile-long park is only 35 feet wide, which makes having the right soil instrumental to success, notes Laura Solano, senior associate at Michael Valkenburgh Associates, Inc., the landscape architectural firm that led the project. 'Having plantings, walkways and accessibility while still providing meaningful places is difficult, ' she says. 'Proportionally, the landscape has very little space to do a lot of work, so the viability of the planting areas is essential. '
Soil for the lower level of the park had to be manufactured because there was only slag underneath the existing parking area. 'There was no growth medium there, ' she says. 'It was a parking lot filled and paved over in the 1940s. When excavation for borings was done, we discovered absolutely no soil available for plant growth. ' Other challenges include the severe sectional grade changes that led to a two-level park plan, flooding caused by the location of the lower tier just three feet above the Allegheny River, and an adjacent four-lane highway.