Crews were observed Friday draining the plagued Lincoln Memorial reflecting pool, a landmark at the heart of Donald Trump’s mission to beautify Washington DC.

Interior secretary Doug Burgum, whose agency oversees the National Park Service, told conservative podcaster Katie Miller in an interview released earlier this week that the new round of draining was planned. He also said that the water might still contain debris from an extensive Independence Day fireworks display over the National Mall.

“Drain the water, clean up the fireworks stuff,” Burgum told Miller, who is the wife of deputy White House chief of staff Stephen Miller. “Repair the vandalism that was done. Fill it back up again.”

Early into his second term, Trump set his gaze on the 104-year-old pool on the National Mall, describing it as “filthy dirty” and suggesting his predecessor Joe Biden’s administration failed to maintain the site.

He has sought to make the pool a symbol of American patriotism by having the liner coating the bottom of the structure reflect the hue of the US flag.

The renovation has come under fire for its mounting price tag – as of June, the estimated cost was over $16m – as the project was hindered by algae blooms that turned the pool green-ish and peeling blue liner.

The Trump administration has blamed the pool’s woes on “vandals”. Several people have been arrested related to the unsubstantiated claims, including a former Olympic cyclist David Hearn, who pleaded not guilty to a felony charge of property destruction. Hearn has said he reached inside the pool to examine the peeled sealant and let go of a chunk when he was told to by a park worker.

“This indictment reflects the administration’s effort to shift blame for their own failures,” Hearn’s lawyers said in a statement reported by the Associated Press. “The justice system exists to determine facts, not to provide political cover.”

The overhaul also has been scrutinized after reports emerged that some contractors selected had long ties to Trump, with critics decrying nepotism.

The work on the reflecting pool is just one of a number of projects Trump has spearheaded across the nation’s capital. Most prominently, he demolished the White House’s East Wing to build a $400m ballroom and plans to build a towering arch between the Lincoln Memorial and Arlington national cemetery.

When Trump initially announced his intentions to beautify the reflecting pool this spring, he said he wanted it completed before the nation’s 250th birthday celebrations.

Water was drained and Trump directed that the bottom be painted what he called “American flag blue”. In May, the president posted on his social media site of the pool: “The goal is to have it done, at this higher level, prior to July 4th – We are ahead of schedule!”

But problems began quickly after the initial work was finished. Trump blamed vandals, and court documents later showed that the National Park Service reported to tpolice a 9 June incident in which a sharp knife or razor cut the pool’s new liner.

The pool was closed for the Independence Day celebration, which featured what Trump said was the largest fireworks display in the world. The president had said that the pool would have to be drained anew as part of the new round of repairs.

Burgum has also said that the Trump administration won’t seek bids for the new rounds of repairs. He told CNN’s State of the Union last weekend: “We’ll use the same company because they did a fantastic job.”

Ohio-based Green Water Solutions, also known as Greenwater Services, was given a $1.7m contract to install a water-purification system in the reflecting pool, while Virginia-based Atlantic Industrial Coatings was awarded $14.7m to repaint and waterproof the pool’s concrete floor.

Democratic senators and House members are investigating the pool project, including seeking answers about how much taxpayer funding is involved.

Associated Press contributed reporting