DOJ admits Trump's Lincoln Memorial Reflecting Pool renovation was 'botched', dismisses case against Olympian

The US Department of Justice (DOJ) has admitted that President Donald Trump's $US14 million ($20 million) renovation of the Lincoln Memorial Reflecting Pool was "hasty and botched".

It comes as government lawyers move to dismiss a criminal case charging a former Olympian with deliberately damaging the monument.

Mr Trump ordered a multi-million-dollar renovation of the Lincoln Memorial Reflecting Pool earlier this year, which aimed to fix leaks and turn the pool a colour he called "American flag blue".

Contracts were awarded to two hand-picked businesses, including a swimming pool contractor, according to The New York Times.

The government bypassed a legal requirement to seek competing bids by citing urgency to get the job done by July 4, which marked America's 250th birthday.

Days after the renovation was completed, algae turned the pool bright green.

Government workers were seen pouring large volumes of bleach into the water in an effort to kill off the algae before the blue lining on the bottom began to peel.

Without providing evidence, Mr Trump later claimed vandals had poured "corrosive and destructive chemicals" into the pool.

On June 19, former Olympic canoeist David "Davey" Hearn, who owned a company that made composite materials for watercraft, stopped by the pool during a 102-kilometre bike ride and reached into the water to examine the peeling coating.

He told the Associated Press he briefly touched a chunk that was still attached to the side of the pool, then let go when a park worker told him to.

National Guard troops and Park Police then detained him for five hours, and he was later indicted for "maliciously" damaging the lining.

Hearn pleaded not guilty earlier this month to one felony count of property destruction.

A trial was scheduled to begin on September 28 in the DC Superior Court.

The charge, which carried a maximum prison sentence of 10 years upon conviction, accused Hearn of causing at least $1,000 in damage to the pool.

Earlier this week, Hearn's lawyers said there were "irregularities" in the legal process.

They pointed to testimony by a National Park Service official that the pool was already damaged before Hearn touched it and couldn't quantify any damage attributable to Hearn.

"The witness's testimony established that the pool had substantial preexisting (sic) damage requiring repair before any alleged conduct by Mr Hearn," his lawyers wrote.

"According to the witness, the pool was leaking more than one million gallons of water per week; its expansion joints had exceeded their service life; and the liner already contained a rip."

In court papers filed on Friday, prosecutors said they had only recently received new information that undermined the basis for the prosecution.

The 20-page filing said additional documents provided by the Department of the Interior showed the damage was the result of a "botched installation" by a contractor and the "rush to complete the project".

A recent visual inspection also revealed damage throughout the pool, including in the middle, where prosecutors say a vandal would not likely have attempted to peel the lining.

"Given all of this newly discovered information, it is difficult to attribute the widespread damage to the Reflecting Pool to vandalism, let alone to establish that fact beyond a reasonable doubt," said the filing from US Attorney Jeanine Pirro, which asked a judge to formally dismiss the case.

The dismissal marks an embarrassing setback for the DOJ, which billed the case as accountability for damage at the landmark.

Hearn has for weeks maintained his innocence and his supporters have characterised the prosecution as a politically motivated attempt by the Trump administration to deflect blame and scapegoat others.

His lawyers said in a statement that the case against him should never have been brought.

"Its dismissal today does not erase the abuse of government power in arresting and charging a patriotic American who did nothing wrong," the lawyers said.

"The government's approach was ready, fire, aim. The administration owes Mr Hearn an apology."