According to the USDA Web Soil map, the area of the rain garden originally consisted of soil named Wawasee Loam with a typical soil profile:
- Ap - 0 to 8 inches: loam;
- Bt1 - 8 to 24 inches: loam;
- Bt2 - 24 to 33 inches: clay loam;
- C - 33 to 79 inches: loam.
So, during the Spring of 2018, I rented a "soil borer" from A-1 Rental, as shown below. The tool turned out to be not so much a soil borer, but more of a post hole digger with an approximately five inch cone. The tool did allow me to bore to a depth of around three or four feet, which was desirable. However, an actual soil borer with a relatively small two inch cone would certainly have been easier to manage!
I was hoping to observe an obvious decrease in the clay content of the soil and/or an obvious increase in the sand content. Either would probably correspond with increased soil permeability. Other then the slight color change, the soil all seemed loamy. So, an "easy" fix of boring several holes down below the rain garden probably would not substantially increase infiltration.
That decision has yet to be carried out, but should be accomplished in the near future. Then again, my clients might decide they like the pond in their backyard! Who knows! NOTE: As I performed the soil bore, I observed numerous mosquito larvae swimming joyfully in the standing water.
UPDATE (July 23, 2018): The pond is currently dried up probably due to the drought conditions we have been experiencing for most of this summer. So, the pond should be considered a seasonal pond. No mosquitoes currently anyways!