A senior National Park Service (NPS) official’s allegation Wednesday (June 24) appeared to echo US President Donald Trump’s earlier claims of vandalism at the Lincoln Memorial Reflecting Pool in Washington, DC.This came amid controversy surrounding Trump’s $14.2m renovation project of the pool. Trump had pitched it as a bid to give it a makeover ahead of the US’s 250th anniversary celebrations on July 4. Here’s what to know.The pool, dedicated in 1922, is the site where civil rights activist Martin Luther King Jr delivered his iconic “I Have a Dream” speech in 1963, and where the March on Washington, DC, drew hundreds of thousands of people that same year.This April, Trump announced that the pool would be repainted “American flag blue” for the 250th anniversary. Although Trump told reporters in May that the renovation would cost “about $1.8 million” and “take one week”, federal contract records showed it ultimately cost $14.7 million and stretched nearly two months.Also read | Trump orders inspection of DC Reflecting Pool over algae bloom, vandalismFederal records show that the contract for work described as “Paint Lincoln Reflecting Pool” was awarded by the NPS’s Denver Service Center in April on a sole-source basis — which occurs when a contract is awarded to a single supplier without engaging in a competitive bidding process — with one bid received, under urgency provisions.The coating, declared complete on June 6, began peeling within two weeks, while algae turned the water green. This prompted Trump to claim in a social media post that an act of vandalism had sabotaged the renovation: “It was purposefully and criminally done, and somebody had to work very hard, probably in the dark of night.” Earlier this week, he also alleged that vandals had poured fertiliser into the pool to feed the algae.The lawsuitStory continues below this adIn May, a lawsuit was filed by the historic preservation group Cultural Landscape Foundation, which sought to halt the renovation. It claimed that the renovation violated the National Historic Preservation Act, a 1996 law that outlines procedures for changes to historic properties.It was in this case that Frank Lands, the deputy director for operations for NPS, alleged this week that a liner along the bottom of the pool was “cut with a sharp knife or razor” earlier this month. Usually made of vinyl, a liner is a waterproof, often customised membrane that covers the interior of a swimming pool. It holds the water in and prevents leaks, besides acting as a protective barrier between the water and the pool’s structural walls.In the court filing, Lands said that on June 9, US Park Service police responded to an “NPS report of damage to the reflecting pool” — mere days after the renovation project was “substantially complete”. He also said that the NPS planned to start draining the pool after the July 4 celebration “to conduct repairs, including assessing and repairing any damage to the lining”.What caused the discolouration?Aquatic ecologists and pool specialists told NPR the discolouration was caused by a natural bloom of algae from the genus Desmodesmus — a process scientists say is common in shallow, sunny pools. The new, darker interior surface would absorb more sunlight, warm the water, and “ultimately lead to more prolific algae growth”.Story continues below this adThe US Interior Department said the algae was part of the early process of restarting water flow. Residual algae from the supply lines, which have been sitting dormant for eight weeks while construction has been taking place, said communications director Kate Martin.A water treatment expert, writing in Scientific American, noted that the same thing happened when the pool was refilled after its 2012 renovation, before the basin had ever been painted blue.NewsletterFollow our daily newsletter so you never miss anything important. On Wednesday, we answer readers' questions.SubscribeTim Auerhahn, chairman of the engineering consultancy firm Aquatic Council, told several media outlets that the peeling material is polyurea coating, a fast-curing surface membrane often used to seal swimming pools. Experts said that pinning the blame on any single factor would be premature.When applying polyurea, workers need to paint a new coat within 24 hours of the last layer to ensure the layers bond and form a solid, watertight mass. Given the renovation’s roughly eight-week timeline, experts said it is possible the material was not applied adequately.Story continues below this adThe pool’s bottom may also have been affected by heavy equipment, trucks, and a presidential motorcade that drove through the area during the coating’s preparation and application.According to Auerhahn, a coating system can fail for several different reasons or a combination of factors. He warned that if the coating was losing adhesion in multiple locations, it could indicate a “more significant concern”.The author is an intern with The Indian Express.