Water main tanks in the Mall to collect drainage

Credit: Max Dorosa of Carnegie Mellon's Facilities Management Services Credit: Max Dorosa of Carnegie Mellon's Facilities Management Services Credit: Max Dorosa of Carnegie Mellon's Facilities Management Services Credit: Max Dorosa of Carnegie Mellon's Facilities Management Services

The storm water tanks installed under the Mall, which is the lawn located between Hamerschlag Hall and the College of Fine Arts lawn, aims to help reduce flooding in that area during severe storms by collecting storm water runoff from existing downspouts and catch basins near Doherty, Wean, Baker, and Porter halls.

As reported in The Piper, an official publication by the Internal Communications Department at Carnegie Mellon University, this collection system is comprised of four concrete and waterproof sectioned tanks; each of them being 80 feet in length, 16 feet in width, and 10 feet in height. Collectively, these tanks, which are 416 sq. meters in surface area, can store up to 275,000 gallons of water. The water collected can be reused for the campus chilled water cooling systems, and excess water will be diverted to the city storm water system which is situated downstream of campus buildings, which eventually drains into the Allegheny River, according to Facilities Management Services and Campus Design and Facility Development.

The area of the Mall, which is low-lying, was severely flooded during the major storms in 2004, 2009, and 2011. The Mall Stormwater Management Project is a major sustainability effort the university has conducted to manage stormwater in a way that is constructive for both the campus and the city. A construction crew began excavating the Mall in early May and the site was completely restored in mid-August. The huge dig process, involving a 550-ton crane, was completed in June.

According to Stormwater Report, because of its hilly terrain, generally poor soil quality, and growing land development, stormwater management is one of the major concerns in southwestern Pennsylvania. Generally, Pittsburgh faces a high flood risk throughout the year. Not only does this excess storm water log the municipal systems and create health, economic, and environmental challenges, it also violates the Environmental Protection Agency’s federal Clean Water Act. According to an article by Environment at CMU, the website for environment and sustainability efforts, Pittsburgh’s frequent rainfall as well as melting snow also causes this problem. The article states that “untreated sewage streams into waterways, overflows from manholes or backs up into homeowners’ basements.” In fact, stormwater runoff is the United States’ most common cause of water pollution.

According to Environment at CMU, Carnegie Mellon University has suffered millions of dollars from damage caused by stormwater in the recent years, and has adopted many practices to prevent stormwater damage. For instance, the Purnell Center has a 10,000-gallon stormwater cistern installed on the roof to slow down the flow of storm water. In the Gates Hillman Complex, there is a 10,000-gallon tank that collects rain water and supplies the water for toilets.
In the Morewood Gardens parking lot, there is a dry well installed for run-off that empties into a vegetative swale and a concrete dam. The Cohon Center has a 6,000-gallon water collection tank that is used for flushing toilets and for irrigation. In addition, Carnegie Mellon University has many buildings with Green Roofs, which refers to roofs that are living or vegetated.

According to Facilities Management Services and Campus Design and Facility Development, the storm water tanks installed under the Mall have the capacity to store rain from a 500-year event with empty tanks. As of the beginning of the semester, the project has been completed and moves the campus closer to the idea of sustainability, reusing the resources already around us.