Time to get out your ruler or other measuring device.
From the NRCS booklet:
Settlement allowance—Settlement or consolidation
depends on the character of the materials in both the
dam and the foundation and on the construction
method. To allow for settlement, build earth dams
somewhat higher than the design dimensions.
If your
dam is adequately compacted in thin layers under
good moisture conditions, there is no reason to expect
any appreciable settlement in the dam itself, but the
foundation may settle. For a compacted fill dam on
unyielding foundation, settlement is negligible.
Most foundations are yielding, and settlement may
range from l to 6 percent of the height of the dam,
mainly during construction.
The settlement allowance
for a rolled-fill dam should be about 5 percent of the
designed dam height. In other words, the dam is built
5 percent higher than the designed height. After settlement,
the height of the dam will be adequate. Most
pond dams less than 20 feet high, however, are not
rolled fill. For these dams the total settlement allowance
should be about 10 percent.
I would get a rough estimate on how thick (vertical measurement) the area was that they dug out for the pipe. If the amount that it settled is within the NRCS parameters, then I wouldn't loose any sleep over it. If it exceeds that amount, then repack if it can be done without making a mess of the rest of the area.
