Adding a 45 x 20 paito slab

[ChevyBuilder]

I'm looking to add an 45 x 20 paito slab to the rear of my house and garage. The former farm land, slightly clay soil is frozen for months at a time here in upstate New York. The Back yard grade is flat, Front yard starts to slope down, 10-15 feet from the front of the structure. There are 3 roof gutters that serve 1500sqft, one at each end of the slab and one in the middle, they will need to be extended beyond the slab. The slab pitch will put another 900sqft of runoff at the slab edge. A contractor suggested a french drain or drywell. In my research so far I have seen these used to move water from soil through fabric, stones, and sand into pipes then to an acceptable location. My application calls for moving water the other way...into the ground.

I want this patio to aid in drainage, what would be suggested?


Building Automation Professional

 

[cvg]

dry wells are commonly used in the southwest to drain water from retention basins into the ground. However, they are not very effective in clay soil. Do a perc test to determine rate of infiltration. Check your depth to groundwater and depth to permeable stratum.

Recommend the following:

Infiltration rate for soil should be at least 0.2 inch per hour (although this is poor, it might work)

Drywell should penetrate 10 feet minimum into a permeable stratum

Design to drain the surface water in 36 - 72 hours - longer periods will begin to cause a nuisance and may breed mosquitoes. Plus, you want it to drain before the next rain storm hits.

If the drywell penetrates the water table or perched water, it should be sealed to prevent direct discharge to the aquifer

Consider using an oil/water separator to prevent contamination of the groundwater

Get a permit from the department of environmental quality