Many homeowners and commercial property managers face the issue of excessive surface water in the turf areas surrounding their homes or businesses. Excess rain water can cause turf diseases and potentially kill your lawn, trees, and shrubs from lack of oxygen in the soil. Coming up with a solution for these problems can be a challenging task when considering such variables as annual rainfall, soil permeability, site topography, and selecting the right drainage system. Sometimes a combination of solutions is required to solve the problem, so it is best to consult a professional contractor to determine which method is best for your specific site conditions. This article gives an overview of the different types of drainage solutions available and the conditions in which they should be used to help you make an informed choice when considering a drainage system for your property.
Downspouts that empty directly into turf or are clogged and not properly redirecting water can cause a number of problems from a leaking or wet basement to a saturated lawn. In the Akron / Canton area of northeastern Ohio, we receive around 36” of rainfall annually which averages out to around 3” per month. An average house has a roof that is approximately 3000 square feet, most of which is typically directed into downspouts or French drains. At 0.623 gallons per square foot for every 1” of rain, in a month about 5607 gallons of water will run off the roof.
This is a significant amount of water which the soil cannot always absorb. Directing the water to municipal storm water collection areas, undeveloped areas on your property, or holding areas are typically the best solutions to this problem. When downspouts become clogged, it is almost always cheaper to simply replace the pipe because snaking does not work for the black corrugated pipe that is used in most downspout installations. This is why for our downspout pipe installations we choose to use HDPE triple wall pipe to provide a longer term solution that can be maintained.
French or sub-surface drains are installed in turf areas that tend to be in low-lying areas and dry out very slowly or sometimes not at all. These drains consist of pipes that are buried 18 to 24 inches below the surface and are surrounded by a permeable backfill such as washed gravel or concrete sand. In Northeastern Ohio where the soil is primarily clay, these drains should be spaced no more than 20 feet apart for optimal performance in turf applications.
French drains do not have to handle the volume of water that downspout drains need to, but they should still be sized appropriately for optimal performance. Water pooling on top of the ground occurs when the soil has absorbed as much water as it is able in the open pore space. The French drains help to lower the water table and increase soil capacity so that it can absorb more water during the next storm. Check out our blog article about French and sub-surface drainage for more information.
Sometimes the simplest solution for a wet lawn is regrading or creating swales to help redirect the storm water. If the lawn slopes towards a house or other structure and the water is creating foundation problems, soil can be added around the building if there is enough exposed foundation. Changing the grade of a site typically requires most, if not all of the existing turf are to be removed and re-shaped. Depending upon the site topography, re-grading can be done to fill in depressions that are holding water, and level out raised areas that are preventing the flow of surface water.
Swales are shallow areas that are shaped to help redirect the flow of surface water. They are made to blend in with existing grades so that the turf area can be mowed without the risks of scalping or operating a mower on a steep slope. The use of regrading and swales for storm water management is always site specific, so it is best to consult a drainage professional regarding other conditions such as potential for increased erosion, percentage of grade, the intended use of the area, and soil stabilization to prevent possible problems.
Impermeable areas such as paved driveways, patios, and turf areas with very compacted soils are places where surface drainage is typically the best option. Surface drains come in many forms such as catch basins, channel drains, and open grates in paved areas. For surface drainage in compacted turf areas, small catch basins with open top grates are recommended. The catch basins help to keep lawn debris such as leaves, soil particles, and grass clippings from entering the drainage system and clogging pipes. When combined with site re-grading, this can be a very effective solution for areas where a French or sub-surface drain would not work because of soil conditions
Storm water from paved areas such as driveways and patios can contribute a substantial amount of water to a lawn and cause extended saturation problems. In order to reduce the effects from runoff, channel drains or open grate drains can be used to collect the water which can then be redirected to another area.
In certain situations it may be hard to redirect water to undeveloped areas or off-site for a number of reasons. These situations may be that the saturated area is lower than all the surrounding land, the municipal storm water system is above the grade of the area to be drained, or if there is nowhere on the site to redirect the water. Water should never be directed onto a neighboring or adjacent property because it is illegal in most areas to do this, especially within municipalities. In situations like this, a dry well is typically the only option other than pumps or other mechanical methods to remove the water.
Modern dry wells are constructed of plastic and are made to store water below grade until it can percolate into the soil. They are installed in a pit and surrounded with a washed gravel that has a 30 to 40 percent void ratio to help increase holding capacity. A typical dry well will hold around 50 gallons by itself, and can hold up to 190 gallons when 1 foot of gravel is placed below and around it. If necessary, multiple dry wells can be installed in the drainage system to provide additional capacity depending upon the area to be drained. In the soil conditions in northeastern Ohio, a conservative estimate is that a dry well can percolate around 100 gallons of water per day into the soil.
For most homeowners and property managers it is best to consult a professional excavation or landscape construction contractor for drainage system design and installation. Jobs such as downspout pipe replacement may seem simple, but it is necessary to determine why the original pipe failed to make sure the next installation will not experience the same problem. For more complex problems in low-lying areas or very saturated lawns the use of multiple systems may be needed to provide the best solution for your storm water problem.
Precision Excavating offers unique and innovative drainage solutions for all project sizes from small lawns to large commercial sites. We have a very thorough knowledge of the causes of drainage problems and the solutions available to provide our customers with the best value for their investment. Contact us for your next drainage project for residential issues such as flooding, standing water, and wet lawns, as well as retention ponds and culverts for commercial drainage solutions.