Finding the space for a new urban park is difficult. Sites that aren't already developed are usually contaminated, and property's more expensive than less centrally located areas. To overcome such obstacles, Dallas looked for private partners interested in teaming up to redevelop land that could be enjoyed by workers and downtown residents.

One such property had been a surface parking lot for more than 20 years. Adjacent to an underground food court, a high-rise condominium building, and several office buildings, the 1.45-acre parcel was a prime location.

The city partnered with local media company Belo Corp. and its philanthropic arm, The Belo Foundation. Belo Corp. Chairman Robert Decherd and wife Maureen established an endowment to fund repairs and improvements. Under their agreement, the city agreed to buy and turn over development-ready property that it will maintain once construction is complete. Belo Garden Development LLC is contracting landscape design, paying for construction, and retains naming rights for the park, now known as Belo Garden.

In late 2006, the city hired outside expertise to conduct a Phase I Environmental Site Assessment. Terracon Consultants Inc. determined the site had been used for petroleum/oil facilities, hat manufacturing, an automotive maintenance garage, and a paint spraying operation. It also contains up to 15 feet of non-native fill including construction rubble such as brick, concrete, glass, wood, and — interestingly — cinder.

Turns out a devastating fire destroyed most of Dallas in the late 1800s. So in addition to elevated concentrations of heavy metals, the soil contained cinder. Though it's a naturally occurring byproduct of organic material that doesn't completely burn, cinder contains polycyclic aromatic hydrocarbons (PAHs). These are a broad range of compounds that includes suspect and known carcinogens.

Initial subsurface investigation found arsenic, barium, cadmium, lead, mercury, selenium, and silver as well as PAHs including benzo(a)pyrene, benzo(a)anthracene, benzo(b) fluoranthene, benzo(k)fluoranthene, dibenz(a,h)anthracene, fluoranthene, indeno(1,2,3-c,d)pyrene, phenanthrene, and pyrene. Further investigation was conducted to evaluate contaminant concentrations and characterize the soils for disposal.

The soils were characterized in 2-foot intervals on a 35-square-foot grid across the site. More than 80 borings and four groundwater monitoring wells were installed. Groundwater wasn't contaminated, so soil was the only media requiring remediation.

Because the site will be used as a park, state law requires it to be remediated to levels acceptable for residential use rather than commercial/industrial use typical for downtown properties. Soil containing contaminants above protective concentration levels acceptable for residential use was disposed of at a licensed facility. This resulted in a net deficit of soil, so clean fill and topsoil will be used to bring the site to grade during park construction.