Four miles from the White House, Army specialists are digging very cautiously into an empty lot where a brick house once stood in one of the district’s toniest neighborhoods, on the edge of the American University campus.

A giant tent covers the site, alarms ready to sound if deadly poisons should leak. After decades of work, decontamination of the old burial ground for World War I chemical munitions is expected to be finished by late next year.

Next year, meanwhile, is also the deadline for Syria to eliminate its entire chemical arsenal, from one end of the country to another, under the American-Russian plan announced 10 days ago.

The disparity between the Syrian rush and the American slog underscores the difficulties facing that plan, even if Syria cooperates. Almost everything about the American effort to rid itself of chemical weapons manufactured from Woodrow Wilson’s presidency to Ronald Reagan’s has been more complex, more time-consuming, more costly and more environmentally fraught than anyone imagined.