What volume of water per day will flow .....(using Darcy's Law?)?

It looks like you're having a problem with your units. You need to make sure it's all in feet or all in miles. I know you've got most of it taken care of, but I think the main problem is your gradient. Since it's in feet/mile, you need to convert it to feet/feet. So that makes it 0.00189393939 feet / feet. Plugging this into the equation, it gives a discharge of 601,600 ft^3/day (but you need to fix your significant figures). This is still a large number, but it's in feet per day so that will make the values pretty high.