One of Washington, D.C.'s most distinguished national landmarks, the Lincoln Memorial Reflecting Pool was nevertheless suffering considerable degradation and in significant need of a major rehabilitation.
Originally built during the 1920s—without any pilings to support it—the iconic pool had sunk by about a foot over the past 90-plus years, falling farther into the area's marshy and salty soils.
This slow sinking caused significant cracking and leaking, which required the city to provide roughly 30 million gallons of water per year—or nearly 600,000 gallons per week—just to replenish the loss. The original pool, which measured 160 ft wide by 2,200 ft long, had a capacity of 6.75 million gallons.
For this $34-million rehabilitation, the Corman Construction-led project team demolished and reconstructed the concrete pool slab, improved accessibility, added security barriers and new sidewalks, refurbished historic finishes and constructed a new water-supply and treatment system that brings the facility up to 21st-century sustainability standards.
To halt the subsidence, contractors installed a foundation built from 2,100 timber piles treated to withstand the area's brackish soil, which is degraded by salt-water intrusion from the nearby tidal basin.
Crews used two mechanical pile-drivers to sink, on average, between 80 to 90 of the 50-ft-long piles per day, working in eight-hour shifts.
The contractor also installed a new raw-water intake and submersible pump system to supply the pool with water from the tidal basin. A new treatment facility filters, treats and recirculates the water, creating a more sustainable system that reduces water usage, improves water quality and eliminates the need for extra water from the city.
Overall, crews installed approximately 6,500 linear ft of water line, 3,500 linear ft of sewer line, 4,400 linear ft of new storm drains and, to connect the pool to the treatment plant, 18,000 linear ft of high-density polyethylene pipe.
Shallower than the original, the new pool has a current capacity of approximately four million gallons of water.
According to the project team, visitors likely will not notice the changes, thanks in part to the pool's improved reflective qualities, which should result from the use of gray concrete at its bottom.
The project also upgraded the visitor experience by adding night lighting.
Lincoln Memorial Reflecting Pool Rehabilitation, Washington, D.C.
Owner National Park Service
Design Firm The Louis Berger Group
General Contractor Corman Construction
Structural Engineer Ammann & Whitney Consulting Engineers
Dynamic Pile Testing D.W. Kozera Inc.
Landscaping Heritage Custom Lawn & Landscape
Electrical Central Armature Works Inc.
Masonry Lorton Stone
Concrete Paving and Exposed Aggregate Metro Paving Corp.
Rebar Furnish, Install Genesis Steel Service Inc.
Asphalt Saw Cutting DOT Diamond Core Drilling Inc.
Quality Control Inspection and Testing CTI Consultants
Concrete, Asbestos Removal Celtic Demolition