Agnes Met An Unfinished Dam

When Tropical Storm Agnes reached the Juniata in June 1972, the new Raystown Dam was not finished. The Geological Survey's report on the storm says construction was not complete when Agnes struck.

The dam held water anyway. The survey found that the uncompleted dam impounded about 159,000 acre-feet of floodwater, cutting the peak flow on the Raystown Branch and on the Juniata below the mouth of the branch.

Just below the dam, the Raystown Branch gauge peaked at 2 in the afternoon on June 23 at 23,300 cubic feet per second. That was a little less than the 24,100 the same gauge had carried on April 3, 1970. Downstream at Mapleton Depot, the Juniata crested at 33.07 feet at 10 that morning, below its 1936 flood mark. Across the basin the flood was generally smaller than 1936, the survey said, but peak flows on the main river were generally the greatest since that year.

How much did the unfinished dam take off the top at Mapleton Depot? The Corps of Engineers' preliminary figures, published in 1973, put the cut at 3.5 feet. The Geological Survey's 1975 report estimated 4.6 feet.

The Corps also counted the money. Its preliminary estimate was that the partly completed project prevented about $59,954,000 in damage. By the end of January 1973, $48,958,000 of the project's estimated $67,800,000 cost had been spent.

Checked 2026-10-31 · County histories and primary sources, read in full

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