Utilities buy "screw-in" ground rods that are driven in with a
gas-powered tool and have a cast screw on the end that goes in the
ground. Some of these can be "extended" to your desired 17 feet. But
these rods are not cheap (hundreds of dollars) and the tools are
exquisitely specialized.

Unless you are having trouble getting the low-resistance-to-ground that
the NEC requires (which might be the case if you live on the side of a
mountain for example) such measures are usually not necessary. If
you're as close to the water table as you claim then
the two code-required 8 foot/10foot rods are probably pretty good
for most purposes.

Plain old water pipe can be driven down (and extended) more easily
than ground rods to your desired 17-foot distance. Depending on
what your inspector says you will probably need the two code-compliant
(shorter) grounding electrodes too.