The Post’s investigation of the slowdown in construction of the Department of Homeland Security headquarters at the old St. Elizabeths site may have left readers with the impression that the project is dead. But, despite the delay, there is an opportunity to finish the project and include considerably more employees than originally planned. A public-private partnership could quickly pick up and finish the headquarters complex with little additional appropriations.

Downtown, another historic property, the Old Post Office, is being renovated through a public-private partnership. The developer, not the government, is putting up the $200 million for the construction necessary for a total historic rehabilitation. We are working on a similar public-private partnership for the DHS headquarters that would leave ownership with the federal government but get the remaining buildings completed. This can happen only if the Office of Management and Budget allows the General Services Administration to use the public-private partnership authority Congress authorized for such projects.

The original sin that slows much federal construction is the tradition of paying upfront in cash and only through annual appropriations. Yet Congress already has spent $1.5 billion, one-third of the cost of the total DHS consolidation. The infrastructure necessary for all the planned buildings is complete — the site’s power plant, information technology, electricity and natural gas, telecommunications, data systems, water, a vehicle-screening facility, a perimeter security fence and access roads, in addition to the U.S. Coast Guard headquarters. If the project does not move forward, the money already spent cannot be recovered. But a public-private partnership could free DHS from the appropriations process.

The Post’s investigation singled out the cost of rehabilitating historical structures at St. Elizabeths but did not note that the government will reuse these buildings instead of spending to preserve empty historic landmarks. Work on several historic buildings — the campus power plant, dining facility and credit union — is complete .

The Coast Guard headquarters was up and running on time because in 2009 the Obama administration and Congress allocated virtually complete funding for its construction as part of the stimulus effort to revive the economy. Since then, cuts have dominated appropriations. That is why the project is 11 years behind schedule. Slow-walking the construction funds has cost plenty, but the shallow appropriations nevertheless have preserved the project. The $190 million appropriated for fiscal 2014 is allowing for work to begin on a building for the DHS secretary and his entire staff. And there is $323 million in the administration’s fiscal 2015 budget.

Stopping the project would not save money; it would cost the government dearly. DHS consolidation will cost $4.5 billion, but the leases for the space DHS now uses will cost $5.2 billion over 30 years. Finishing the project will pay for itself in savings from expensive leases.

Moreover, DHS is required by law to be located in the nation’s capital. St. Elizabeths is the only site in the city that can accommodate the DHS agencies and provide secure setbacks. Because the site is government-owned, the outsized cost of land is saved.

Ironically, the delay in DHS construction is allowing planning for more than 20,000 employees, rather than the original 14,000. For example, some Coast Guard employees remain in leased space. GSA is eliminating these leases and consolidating these employees into the new Coast Guard headquarters.

Premature obituaries, including short-term thinking about how to cut costs, harbor no savings at this stage and would create waste on a grand scale. Giving up would leave a living monument to failure, not of construction, but of Congress to finish what it started and said was required to protect our country. Tragically, walking away also would be a betrayal of promises made for development in the city’s lowest-income area, where DHS is located.

The writer, a Democrat, is the D.C. delegate to the House of Representatives.