If you plan to build a drainage bed, or drainage basin, it’s very important that you be aware of the absorption speed of the site’s dirt. This speed will tell you how much area in square feet that the bed should cover for draining water to harden, or absorb into, the soil rather than pooling on or running off the region. Pooling can attract insects and cause smells, and runoff erodes soil and can spread contaminates. Soil’s absorption rate is dependent upon the amount of clay, sand, loam or gravel that the soil contains.
Choose at least three locations to dig a hole at the prospective drainage bed area, with the holes spaced evenly across that area. If the region is large region, then digging over three holes will create more precise soil absorption rate results. For instance, plan to dig 1 hole at each corner and at the center of the future drainage bed area, or dig holes in a grid pattern each 20 feet if the bed area will be very big.
Dig a vertical hole using a 4- to 12-inch circumference in each location chosen for a hole, employing an augur or spade for the endeavor. Every hole’s sides must be vertical, and each hole has to be the same depth water will enter the drainage bed, which usually is 6 to 36 inches below the soil surface.
Roughen the walls of each hole if necessary to keep the absorption conditions natural. If a hole’s sides are smooth, solid surface as opposed to how dirt appears naturally in the lawn, then that state will not lead to an absorption rate that is accurate for the lawn.
Place about a 2-inch-deep layer of 1/2-inch gravel in the bottom of each hole.
Fill each hole with no less than a 12-inch-depth of water, measuring from the top of the gravel. If a hole is fewer than 12 inches deep, then put at least a 6-inch-depth of water from the hole. Allow the water to saturate the soil overnight or for no less than four hours, adding water to each hole as necessary during that time to keep the water level in the 12-inch or even 6-inch depth over the gravel, using whichever water depth you used initially. If, however, you add water to a hole twice and twice the water drains in fewer than 10 minutes, then you don’t have to add water to the hole. Furthermore, if the soil is mostly clay and a hole’s water level does not appear to move, then continue to maintain the hole’s water level for three to five days. The time you maintain a certain water level in each hole is that the saturation period.
Place a yardstick or ruler in each hole the day following the saturation period is over. The yardstick’s or ruler’s ending displaying the 1-inch mark has to be at the hole’s bottom, over the layer of gravel. The yardstick or ruler should make it to the top of the hole, and so use a ruler just in a hole that is no more than 12 inches deep. The water does not have to have drained entirely in the hole, but it has to be fewer than 6 inches deep.
Add enough water to each hole so that the water depth is 6 inches. Refill each hole to the 6-inch water depth every 30 minutes for four hours as water seeps in the hole. Write down the water level in each hole in the four-hour mark, but don’t add water to the holes. Subtract 1 hole’s current degree of water out of six to ascertain how many inches of water have been consumed. Duplicate that job for every single hole. If your lawn has sandy soil and the holes’ water is eliminated before 30 minutes pass, then refill every single hole to the 6-inch water depth every 10 minutes for a period of one hour. Take the water level measurement of the holes in the mark.
Divide the elapsed time by the number of inches the water level dropped in the 6-inch degree in a hole during the last measurement interval. If, for instance, 4 inches of water stayed in a hole following 30 minutes, then divide 30 by 2 to find an absorption rate of 15 minutes per inch for that hole.
Insert the absorption rates of each hole. Divide that total by the number of holes to find the average absorption rate for the whole possible drainage bed area. If you found over a 20-minute per inch difference in the absorption rates of the fastest-draining and slowest-draining holes, then utilize the slowest-draining hole’s absorption speed as the absorption rate for the drainage bed region.