More than 25 million visitors a year stop by The National Mall and Memorial Parks. Here are the details on how to restore an area with so much traffic.
Known fondly as “America’s Front Yard,” the National Mall and Memorial Parks is located at the heart of our nation’s capitol and holds tremendous historic value to the millions that set foot there each year.
But when the country’s “Front Yard” needs an overhaul, the resulting landscape project is no small undertaking. Working around visitors and adhering to strict regulations were just two of the challenges posed as this massive restoration project first got underway in 2010.
Overuse has taken a serious toll on the National Mall and has been the key reason behind its dilapidation. By 5 p.m. every day, the Mall is packed with people playing sports like Ultimate Frisbee, softball, football and many other pick-up games – not to mention all of those who use it to get to various museums or simply enjoy the outdoors. On top of that, the Mall gets regular use as a space for festivals, demonstrations and other large-scale events.
“The word ‘overuse’ doesn’t even cut it,” says Michael Stachowicz, turf management specialist at the National Mall and Memorial Parks. “The park gets more than 25 million visitors a year. Some events require tents set up for weeks at a time which kills the grass,” he says. “Couple that with the compaction from so many people on the lawn and you can see where there’s a major problem.
“Soil analysis performed revealed that the bulk density was similar to that of concrete. And the infrastructure that was in place was simply not able to handle the sheer amount of usage the space gets.”
Approaching the problem. When faced with coming up with a solution for the deteriorating Mall, the National Park Service took a progressive approach to the problem. They went and studied other parks and turf industries and sought a plan to better manage the historic space. Part of that plan included hiring a turf manager – Stachowicz – to oversee the area. The other part was a major renovation project. In 2010, a multi-phase historic renovation of the National Mall was launched.
The first major phase was recently completed. Work on Phase One included the irrigation pump station, which will eventually service the entire Mall, and a clean-up of the area near the Capitol in time for the Presidential Inauguration. All of this was completed while minimizing disruption to both visitors and city dwellers, says Stephen Titus, vice president and branch manager of the DC branch of ValleyCrest Landscape Development (VCLD), the landscape developer serving as a major subcontractor to Clark Construction.
The ValleyCrest crew removed the existing improvements and soils to a new subgrade and installed a sub-drainage system, similar to a professional sports field drainage system.
Brian Vinchesi, president of Irrigation Consulting, designed the irrigation system which included the sprinklers and all of the piping. When finished, the system will include four cisterns, each holding 250,000 gallons of water. Two have been built so far. “The pump stations are below the ground in a big room along with two of four cisterns that have been built so far,” Vinchesi says. “In total, they will hold a million gallons of storage. We pump out of one and transfer from the other three. The cistern that has the most water in it transfers first.”
When there isn’t enough rain for the system to run on storm water alone, potable water will be substituted. However, the system is designed to not be wasteful. “We didn’t want to waste money by putting potable water into the cisterns,” Vinchesi says.
“That takes away volume from storm water and we also pay for it to sit there. So we do not put any potable water in unless we are irrigating. We have a flow meter on the potable water and that communicates with the pump station so that we’re able to match the amount of water pumping out into the irrigation system. We never use more potable water than we’d use immediately.”
Even beyond the size and scale of the irrigation system, the operation is complex in other ways. Vinchesi says that regulations required it be an elaborate system. “In DC when you spray water in the air you have to disinfect it,” he says. “So the pump station is also a filtering system with UV disinfection.”
Although the system is highly complex, it was also a goal to keep the amount of equipment needed minimal and keep the system as low maintenance as possible. “The irrigation utilizes HDPE piping, selected for its durability, flexibility to scratching and also because of its environmentally friendly manufacture,” Titus says. “Rain Bird golf irrigation heads and controls were used. The golf type sprinklers were used to minimize the number of heads required and to allow programming flexibility associated with valve-in-head sprinklers.”
Considering previous systems have not held up to the high level of usage the National Mall gets, protecting the new irrigation system was a critical component to its success. Tent stakes had previously done great damage to the Mall’s irrigation system, so the new system’s piping is buried five feet deep. “Minimizing the number of heads also makes them less likely to be damaged,” Vinchesi says.
Stachowicz adds: “The gravel hardscape areas were increased a little so that there was more non-turf event space.”
Overcoming challenges. Besides collecting storm water for reuse, there were other sustainability considerations taken into account on the project. VCLD was able to recycle a majority of the 100-percent copper system rather than send it to a landfill. Existing project soils were also salvaged and later blended with sand and compost to create the specific root zone soil mix for the panels, says Titus. In total, VCLD expended over 21,000 man hours in the installation of Phase One work.
“As each of the areas are relatively small compared to the amount of detail work required, we were consistently working around other trades,” Titus says. “Communication between trades was a key component to successfully completing the work with the project requirements. The National Park Service and the Clark management team understood that grassing windows were the key driver for the project and the decision to change from seed to sod allowed more flexibility when the grasses were installed, thus assisting in keeping the project on schedule.”
It was also necessary to constantly keep in mind that the project should not interfere with visitors’ experiences. “The project was fenced off from the public throughout the project,” Titus says. “Most people who made the effort to learn what was being built were excited to learn that the Mall was being restored to a better condition.”
With the first phase now complete, the restoration project continues to forge ahead. “There’s always something going on here and it can be hard to work around major events and activities – as well as pressing deadlines – but it’s been a team effort to achieve that. The fact is there are people on the lawn all the time and that’s a wonderful thing," Stachowicz says. "It’s a vital green space to DC and certainly one that deserves restoration.”
Web Extra: Read about a cooperative initiative between the United States Arboretum, the United States Department of Agriculture and the National Turfgrass Federation by visiting www.lawnandlandscape.com, clicking the “current issue” tab and looking for “national exhibit focuses on turf” under the web extra section.