Landscapers’ Stormwater Management
Property drainage is crucial, though frequently disregarded, a feature that affects most, if not all, properties, whether it’s a solo project or incorporated into a bigger endeavor.
With all of the new buildings, the terrain is continuously changing. This has an impact not just on the site under development, but also on nearby properties, including runoff and drainage concerns.
Stormwater drainage systems that are effective either enable water to move to lower elevations or allow for corrective grading. Because each site is unique, I begin by evaluating its available elevation, soil characteristics, the usual inflow of water volume, and traffic. These variables have an impact on the depth, diameter, thickness, and composition of the pipe that may be used. They also have an impact on the soil separator and gravel that may be utilized.
Details on numerous potential property drainage options are provided below. I’ve also provided a simple equation for determining the gallon capacity when assessing the cost of building a dry well.
Drainage Systems for Homes
Does the property have damp patches or pooling during or after rains? These are the most often encountered issues. Poor drainage areas, which cause these problems, are usually best rectified by adding plastic drain boxes, cap surface drains, or greater capacity concrete catch basins with a lift-off iron frame and grate. Underground drainage pipes of appropriate size, often PVC, are also installed and linked to drain boxes or surface drains. Water may stream downhill along these lines to a lower height.
Drainage lines of any size may be built based on the expected waterflow on the site. 4′′ diameter drainage lines are often utilized in residential applications, but larger diameter drainage lines are required in commercial applications, with the size being specified by technical criteria. (Because each rain event is unique, engineers’ estimations are speculative and should only be used as a guideline. As a result, drainage systems can only be assessed in terms of how many gallons they can flow in a certain time period, such as gallons per minute or hour.)
In many circumstances, bigger diameter pipes are preferable; nevertheless, it is crucial to remember that a larger diameter line does not necessarily result in a better-flowing system. When every inch of elevation is crucial on properties with limited pitch, a smaller diameter pipe may provide a modest advantage and greater flexibility. It may also flow better with little or no silt formation, resulting in improved system performance and lifetime.
Downspouts from the home or building, as well as sump pump ejection lines, may be connected to the drainage system. Rake and seed the dug-up trenches as a last operation, or in many situations, employ a sod cutter to reduce grass damage on the land. Sidewalks, driveways, and curbs are often trimmed and patched.
Grid Technologies
Drainage grid systems are not new and have been utilized effectively in poor drainage regions for many years, such as low-lying sporting fields. They are meant to absorb and divert water below the surface using a tic tac toe pattern of subterranean lines and surface drain caps. This grid is then connected to a PVC drainage pipe that runs to the street or a lower elevation. The surface drains should be the only visible portion of the system after installation.
With over 30 years of experience in landscape drainage, I created a drainage grid system that collects ground water under the surface as well as drains surface water. Instead of utilizing solid PVC drainage pipes meant merely to convey water, I used perforated PVC surrounded by clean pebbles and covered in filter fabric.
Wells that are dry
Installing a dry well is an option if a lower elevation is not accessible to drain to, or if the municipality where your project is situated requires it. Dry wells are intended to enable water to percolate into the soil around them. However, in locations with high levels of soil saturation, absorption may take longer, and the usefulness of a dry well is greatly reliant on the water table. When utilized in combination with dry wells, outdoor sump pumps perform well. (I’ll elaborate later.) I build dry wells by digging a huge hole, lining it with soil separator or filter cloth on all sides (including the top and bottom), and filling it with clean gravel. To collect water, a drain box or catch is placed as an entrance point. A property drainage system that drains directly into the dry well may be built or adjusted.
Large capacity dry wells are effective; but, once full, the dry well will overflow. As a result, if possible, an overflow line should be built.
Here are two basic ways I use to determine a dry well’s gallon capacity based on stone size:
Exemplification 1:
When 2′′ clean gravel is used, 65% of the volume is accessible for water capacity.
A. Dry Well 8’x8’x36″=224 cubic foot hole
B. 224 cubic feet multiplied by 7.5 gallons per cubic foot is 1,680 gallons.
C. 1,680 gallons multiplied by.65 is 1,092 gallon capacity.
Exemplification 2:
When a smaller 34″ cleaned stone is used, 55% of the volume is available for water capacity.
A. Dry Well 8’x8’x36″ = 224 cubic foot hole
B. 224 cubic feet multiplied by 7.5 gallons per cubic foot is 1,680 gallons.
C. 924 gallon capacity (1,680 gallons x.55).
Because the spacing between the stones are greater, the 2′′ stone clearly provides for higher water storage. Smaller 34″ stones might wedge closer together, reducing water capacity.
Sump pumps and catch basins for the outdoors
A lower elevation may not be accessible on many homes to drain water away. In these cases, an outdoor sump pump may be an excellent option. Outdoor sump pumps are comparable to ones used inside, but various safety features should be included. The pump should be designed to industrial standards in order to endure cold conditions. A weep hole may also be put within the sump pit between the pump and the check valve. Long runs moving water uphill will need a bigger, more powerful pump with a wider discharge line diameter.
I suggest a concrete catch basin with an iron frame and a lift-off grate in conjunction with outdoor sump pumps. This is due to the fact that outdoor sump pumps require regular maintenance. Sediment may need to be removed from the pit’s bottom and the pump intake maintained free. The frequency of this maintenance is determined by the site circumstances, but every six to twelve months is a decent rule of thumb. Concrete catch basins allow for more water and sediment buildup, and the lift-off grate provides for easier access. A low-cost solution is a plastic sump pump pit with an interlocking cover.
Another consideration for outdoor sump pump installation is that an electrician will be needed to wire the pump in accordance with local building requirements. It’s also critical to remember to always cut off the power before doing any maintenance or cleaning on the pit. The power must also be turned off during cold weather to avoid the pump from burning out.
