[quicksix]

Dig a hole next to or near your Thuja, about the same depth and width as the ball and burlap they came out of.
Fill it with water, let that volume drain out. while the sides are still wet fill again and time(roughly) the amount of time it takes to go dry. That is your percolation rate.
You can then adjust the parameters of your drip system (volume, frequency and duration) to provide adequate water for the top 5/6 inches of soil. Deeply water 1-2 a week. Change one parameter at a time.
Water at drip line, because the the root tips are where the root hairs actually take up water. (Transpirational pull)