After 20 months and about $34 million of work, the new Lincoln Memorial Reflecting Pool is being refilled again for good.

The pool appeared to be about one-third full Monday afternoon, and the National Park Service said that if all goes well, it could be completely refilled by the weekend.

But Steve Lorenzetti, deputy superintendent of the National Mall and Memorial Parks, said the pool will probably not reopen to the public until the end of the month. Sodding and other work were underway Monday.

The pool, about 160 feet wide and 2,100 feet long, is one of the most iconic sites in the nation but has been an unsightly construction project and off limits to the public since 2010.

Technicians had been adding and draining water for several weeks during tests, but the filling underway is probably final, Lorenzetti said. He added that the new pumps are being operated only during working hours, out of an abundance of caution.

The pool was added shortly after the Lincoln Memorial was dedicated in 1922 before a crowd that included Lincoln’s only surviving son, Robert, who was then 78. It quickly became a gathering place and remained so for 80 years.

Over time, however, the pool began to crack, leak and otherwise deteriorate.

It has been almost completely rebuilt and slightly redesigned. It is shallower, needs less water and is more aesthetically pleasing, with a tinted bottom to make it more reflective.

It employs a new water supply system in which its water will for the first time be drawn from the Tidal Basin — not from city reserves — and be cleaned and recirculated. The old pool could not circulate its often-stagnant water.

Project workers tore out the old concrete bottom and drove 2,133 timber pilings into bedrock to support the new structure before 7 1 / 2 acres of concrete were poured to form a new bottom.

Lorenzetti said a formal dedication ceremony probably will be held later.