The historic DC tide pool is being restored.

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The National Park Service is planning a massive restoration of the crumbling seawall around Washington’s scenic Tidal Basin and a reshaping of the shoreline there and in adjacent West Potomac Park.

Dating more than a century, the historic Tidal Basin is an annual focus of the National Cherry Blossom Festival and is packed with visitors who gather to view and photograph the cherry trees that surround the basin.

And the Martin Luther King Jr. Memorial, Jefferson Memorial, and Franklin Delano Roosevelt Memorial sit on the basin and serve as impressive backdrops.

But portions of the basin’s seawall have been sinking for years, and the structure and its walkway are often swamped by tidal floods, leaving behind debris, trash and dead fish as the water recedes.

A section near the Jefferson Memorial is “underwater twice a day, every day,” Mike Litterst, spokesman for the Park Service’s National Mall and Memorial Parks, said Thursday.

“We rerouted the path in that area to bring it further from the edge,” he said. “We did this about 20 years ago, and it’s underwater, not every day but a few times a month,” he said.

In some places, the seawall has “leveled out between three and four feet” since it was rebuilt in the 1930s and 1940s, he said.

“And at the same time, sea level rise has caused the Tidal Basin to rise a foot,” he said. “So we have water that’s four feet higher than it was supposed to be when they built that.”

Some vegetation grows out of the wall.

A dozen years ago, the Park Service spent more than $12 million to repair the section of seawall in front of the Jefferson Memorial where it slipped and sank in the mud at the bottom of the pool.

Now, the Park Service says a two-part, $5.7 million contract has been awarded to begin the planning and compliance process for the proposed restoration project.

The contract was awarded to HDR, an architecture, engineering and planning firm based in Omaha, and Moffatt & Nichol, an engineering firm from Long Beach, California with expertise on the water.

The Lincoln Memorial rose out of the mud of the Potomac 100 years ago

The park service said it was opening a two-month period for the public on Friday to comment on the project.

The dam was originally constructed between 1893 and 1897, the park service said in a recent historical report. It’s more than a mile and a half around, the report said.

“Despite various repairs over the decades since their original construction, the seawall systems are no longer structurally sound and threaten the historic setting and the safety of visitors,” the park service said in a statement.

“Without improvements, walls will continue to deteriorate and fail, causing sidewalks to buckle and soil to erode,” the statement said.

Sections of the seawall will be rebuilt on new, stronger foundations and the walkways will be replaced.

The sinking section at the Jefferson Memorial was believed to have failed because it was built on a foundation of wooden piers that were not long enough to reach bedrock. The old foundation was replaced with concrete piles and caissons resting on bedrock.

Litterst said he thinks the same procedure will be used this time.

The park service said the seawall repairs should also protect cherry trees from dying from tidal saturation.

A contract to design and execute the project will be awarded next year or early 2024, the park service said.

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