Construction at Loudoun Gateway station, part of phase 2 of the Silver Line, on July 26, 2017, in Sterling, Va. (Katherine Frey/The Washington Post)

Metro’s Office of the In­spec­tor General will take over the agency’s in­ves­ti­ga­tion into flawed con­crete in phase 2 of the Silver Line, the Dul­les cor­ri­dor ex­ten­sion be­ing over­seen by the Metropolitan Washington Air­ports Authority, the trans­it a­gen­cy said Wednes­day.

In­spec­tor General Geoff Cherrington said in a news re­lease that his of­fice will con­duct the probe ex­am­in­ing the con­crete flaws re­vealed in May, when a whistleblower’s law­suit alleging test-doc­tor­ing and ma­nip­u­la­tion of pro­ject ma­teri­als be­came pub­lic. In all, 1,500 precast pan­els were said to be in ques­tion, and 20 percent con­tained flaws. The pan­els now re­quire a seal­ant to pre­vent wa­ter in­tru­sion and oth­er types of dam­age.

An­drew Nolan, 28, the former qual­i­ty con­trol man­ag­er of Uni­ver­sal Con­crete, the com­pany in ques­tion, pleaded guil­ty in federal court last month to con­spir­a­cy to com­mit wire fraud for his role in fal­si­fy­ing test data so the con­crete passed in­spec­tion and for or­der­ing oth­ers to do the same.

Cherrington said his re­view will en­com­pass fac­tors such as con­crete qual­i­ty and con­struc­tion prac­tices, along with con­tract com­pli­ance and whether con­struc­tion prob­lems could lead to un­in­tend­ed fu­ture spend­ing. While MWAA is over­see­ing the pro­ject’s con­struc­tion, the six-sta­tion ex­ten­sion is ex­pect­ed to be trans­ferred to Metro upon its es­ti­mat­ed 2020 com­ple­tion date.

“We are in­iti­at­ing this re­view to ensure that WMATA — and by ex­ten­sion, its fund­ing juris­dic­tions and the re­gion’s tax­pay­ers — can be con­fi­dent that they will be re­ceiv­ing a qual­i­ty pro­ject that is safe and re­li­able for rail op­er­ations,” Cherrington said in a state­ment. “In ad­di­tion, we want to clear­ly under­stand what, if any, long-term ex­pense risks are out there as a re­sult of ne­ces­sary rem­edies to ad­dress these qual­i­ty issues.”

Metro said it would in­de­pend­ent­ly re­view the con­crete prob­lems in May, when the whistleblower suit came to light af­ter the U.S. Justice Department and the Vir­ginia attorney gen­er­al inter­vened. But the OIG said its probe will now over­take that in­ves­ti­ga­tion for cost-saving pur­poses.

The federal and state lawsuit against Universal Concrete continues separately.

“Metro wel­comes the OIG’s re­view, and the General Man­ag­er shares the OIG’s in­ter­est in ensuring that the Silver Line con­trac­tor meets their ob­li­ga­tions and de­liv­ers to Metro a fin­ished pro­ject that is safe, re­li­able and main­tain­a­ble,” Metro spokesman Dan Stessel said.

Charles Stark, executive director of the Silver Line rail project, said project officials were not surprised by the IG’s announcement because they knew there was interest in looking into issues raised in the whistleblower lawsuit.

“We of course will extend complete cooperation and supply any information Metro’s IG might request,” Stark said. “We remain committed to turning over a safe and reliable product."