What kind of chiller do you have? what size tubing and length? I agree that putting the hose in the ice water would not be the best bet, as there is much less heat transfer through the hose wall than you'd want. What I did this summer (in Virginia, 100 degree brew day) is to use my 50' 3/8" IC with the 70 degree or a little more ground water until the temp is under 100, then I set the kettle into that tub with the ice water so it helps knock the temp down easier while running the IC. I was down to 72F in around 25 minutes if I remember correctly.
Primary: 20 min IPA (14oz cascade/5gal), partigyle pale
Bottled: Orange Cream Ale, Big Red Ale, RIS, American Stout, Nut Brown Ale, American Amber Ale, Brown Porter