By Jonny Lupsha, Wondrium Staff Writer
Flooding in Washington left puddles in the White House’s press room basement, USA Today reported. The flooding was the result of a major storm that hit the mid-Atlantic last Monday, inviting scrutiny of the site design.
The White House is no stranger to flooding; minor water damage has been reported in the building before. Just as the name implies, the basement is built beneath ground level, which, if not constructed exactly right, can lead to drainage from higher areas and a buildup of storm runoff. Many factors lead to structure-caused water damage and in-home flooding.
Location, Location, Location
The responsibility of ensuring proper storm drainage heavily involves site design. “The site design process can be attributed to a single building lot—but it’s most often applied to an entire development, consisting of multiple residential or commercial properties,” said Dr. Stephen Ressler, Professor Emeritus from the United States Military Academy at West Point. “The site design for a development deals with all aspects of physical layout and integration with local civil infrastructure systems, to include the design of streets, parking lots, and cul-de-sacs; local water supply, wastewater disposal, and storm drainage; as well as modifications of the Earth’s contours through earthwork or grading.”
Storm drainage concerns itself with guiding surface water, mostly rain, away from homes. Dr. Ressler warned against underestimating it, despite its relatively low proportion of the Earth’s water. “If precipitation that falls on your lot isn’t directed away from your house, some of it will seep into the soil around your foundation and may find its way into your basement,” he said. “And if your lot adjoins higher ground, storm runoff will generally flow from that ground onto yours, exacerbating the challenge of conveying surface water away from your foundation.”
The Importance of Grading
Land developers must provide three separate solutions to storm drainage in order to ensure proper water management. The first is a storm sewer, which Dr. Ressler describes as “a network of underground pipes that collect storm water and convey it to a nearby watercourse, lake, or ocean.” The second is a storm water detention pond, which is a basin near a storm drain outlet that allows water to sit temporarily and absorb into the soil or evaporate. Finally, and most relevant to the White House last week, land development design must incorporate “earthwork,” also called grading.
“In general terms, grading reforms the topographical contours of the project site for compatibility with the intended land use,” Dr. Ressler said. “Our design must provide pathways for precipitation that falls on rooftops and unpaved areas to flow overland to the storm sewer inlets without flooding basements, creating unwanted ponds, eroding hillsides, or flooding streets.”
Hypothetically speaking, once we add a house to a land development project—thus accumulating water in its two uphill walls—how will we fix this problem? “We’ll meet this challenge by grading the site to modify the pattern of overland flow,” Dr. Ressler said. “We’ll ensure that the soil around the foundation and the driveway are sloped away from the house, and we’ll sculpt the uphill portion of the yard into a swale, which will divert the flow around the building and down to the street, where the overland flow will be captured by a storm inlet.”
Many factors must be met to avoid basement flooding and interior water damage on a property. Finding appropriate land, ensuring its access to storm sewers and detention ponds, and performing proper grading around the perimeter of the structure are vital—even at 1600 Pennsylvania Avenue.
Dr. Stephen Ressler contributed to this article. Dr. Ressler is Professor Emeritus from the United States Military Academy at West Point and a Distinguished Member of the American Society of Civil Engineers (ASCE). He earned a B.S. from West Point and an M.S. and a Ph.D. in Civil Engineering from Lehigh University, as well as a Master of Strategic Studies from the U.S. Army War College.