We like to go down a minimum of 2 feet. We have gone down 4 feet to keep water out of a basement.After 5 feet the cost goes WAY up as you have to shore the trench up as you work, and more people get involved......... 

That's the perf pipe in a black sock Bob is holding in the center of the trench.The perf pipe has holes in it to allow the water in the trench to be drained away.  The black sock helps keep dirt out of the pipe. 

a light rain of rocks...chained up for traction...the drain was working as we installed it. Very wet area.... 

It doesn't get much prettier.....2 foot trench, 2 inches drain rock, 4 inch perf pipe with sock, 16 more inches of drain rock, 36 inch wide filter fabric l[like the black sock but white], 4 more inches of drain rock to the finish grade. 

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