Snapdragon Stadium site prepared to weather storm these days

Those brave souls tailgating in wet weather before Saturday night’s Boise State-San Diego State football game were probably too busy biting into burgers and sipping on soft drinks to notice, but the Mission Valley stadium site handles stormwater way better than it once did.

When SDSU took over the 166-acre property in 2020, the focus was on construction of Snapdragon Stadium at the northwest corner of the site.

Snapdragon’s construction coincided with demolition of the former stadium in the middle of the property. Some of that debris, along with tons of fill dirt, raised the property level 10 or more feet and eliminated the flooding issues that plagued the property for decades.

Perhaps the most famous flooding example came 15 years ago, when the Qualcomm Stadium parking — and the field itself — was flooded 24 hours before kickoff of the Poinsettia Bowl between SDSU and Navy.

Bowl officials had equipment brought in from Riverside County to pump out the water on the field — affectionately nicknamed Lake Murphy — and the field, though a little slippery, was playable by the scheduled kickoff time. SDSU won 35-14, giving the Aztecs their first Division I bowl victory.

SDSU officials not only raised the surface level but also updated the drainage throughout the property, especially on the east side, where 4,600 residential units are planned.

For decades, the site of the former San Diego/Jack Murphy/Qualcomm/SDCCU Stadium was ringed by a nearly 19,000-spot asphalt parking lot that became a contamination source when it rained. Water hit the pavement, picked up bacteria, chemicals and synthetic fluids, among other things, and washed it straight into the San Diego River..

The massive lot has been replaced by 80 acres of open-space parks and landscape that opened two years ago along the property’s southern and eastern borders. The fields and parks have come to be called “The Green Sponge.” Potential contaminants are naturally absorbed and filtered before the water reaches the river.

In addition, water from other areas is “captured and sent through a network of pipes that lead into bioretention basins and engineered wetlands,” according to SDSU

Bioretention basins can be seen south of the trolley station as well as the southwest corner of the property.

The basins are situated above the 100-year floodway. Native plants sit on engineered soil and an “impervious liner” acts as a barrier to groundwater. Once filtered, the water leaves the basin through a perforated drain pipe.

Engineered wetland areas are located just south of Snapdragon Stadium as well as northeast and southeast areas of the site. These are “in-ground concrete structures filled with sand and clay that naturally filters pollutants,” according to SDSU

Contamination of the area dates back four decades, when leaks were discovered at the Mission Valley Terminal fuel storage tank farm located adjacent to the northeast edge of the stadium property.

Petroleum leaked under the parking lot as well as the stadium itself. Cleanup efforts began 20 years ago and included the removal of nearly two million pounds of contamination, according to the San Diego Regional Water Quality Control Board. The board announced three years ago that the soil and water contaminated by petroleum was finally clean.

SDSU announced last year that it had received a $2 million grant from the San Diego River Conservancy to build a laboratory in the River Park for training and research.