Uncle Sam, claims a group of private- sector waste hunters, could save a lot of money by changing his construction and management practices.
* In suburban Washington, D.C., the Federal Highway Administration paid $10, 000 to route a hiking trail around a single chestnut tree.
* In McConnel, Kansas, an Air Force hospital with a 16 percent occupancy rate is scheduled to receive an expensive new building in 1987.
* Overall, the General Services Administration spends about $125 million a year managing government buildings. A life insurance firm with similar holdings does the same job for $9 million.
The President's Private Sector Survey on Cost Control (PPSSCC) says that by following its recommendations, the federal government could save $5.4 billion in construction costs over the next three years. An additional $2.4 billion could be pared off Washington's general property management expense, and $8.5 billion could be cut from outlays for federal hospital management, says the survey.
The PPSSCC is a group of 1,300 private- sector executives appointed by President Reagan to ferret out waste in the federal government. So far, the PPSSCC has made public about half of its cost-savings recommendations - suggestions that would save the US $130 billion over a three-year period, says PPSSCC head J. Peter Grace.
But a healthy chunk of the group's proposed cuts would likely be politically controversial. For instance, many of the PPSSCC's suggestions for saving money on federal construction involve changing environmental laws. The group recommends relaxing regulations governing how much the government must spend to soften the blow of new building on the environment, and urges changes in the Scenic Rivers Act and Clean Water Act.
Citing a proposed highway in Hawaii which has been tangled in litigation and government red tape for 19 years, the PPSSCC says streamlining procedures for producing environmental impact statements could shave $340 million off federal construction costs, over three years.
Perhaps less sensitive is the PPSSCC's conclusion that Uncle Sam could manage facilities better once he's built them. Slothful maintenance wastes $340 million a year, says the group, while $200 million could be saved by taking a more organized approach to energy conservation.
And shrinking bureaucrats' office space, says the PPSSCC, could save $235 million over three years. The General Services Administration goal is an average of 135 square feet per federal employee, but only one agency - the Postal Service - is even remotely close to that figure. At the Office of Personnel Management, each bureaucrat has an average of 206 square feet; at the State Department, the average is 188.
But the biggest ticket item in the latest round of PPSSCC cost-cutting suggestions is federal hospital management. The Army, Navy, and Air Force all have their own hospital systems, says Mr. Grace disapprovingly, leading to duplication of services and many empty beds. The military hospital occupancy rate is about 46 percent, but ''when you get utilization down much below 88 percent you're in trouble,'' says Grace.
Yet all three services are forging ahead with hospital construction. About $ 700 million of these new health facilities could be dispensed with, figures the PPSSCC.
And even more money - $4.3 billion, over three years - could be saved through tightening management at the Veteran's Administration, claims the survey.