Tired of your lawn flooding because the level of stormwater in the storm drain is too high?
You can raise your stormwater pit to solve this problem!
After consulting your local public utility department, you can choose to raise stormwater pits by using prefabricated collars or pre-made concrete rings or slabs.
On average, Americans use about 82 gallons of water per day for their homes.
Thirty percent of this water is used on the lawn and landscape around a home, which can cause significant water runoff.
This runoff increases erosion, clogs streams, and causes flooding before it travels to larger waterways.
In this article, we’ll discuss how to raise, or build-up, a stormwater pit to minimize the amount of runoff that occurs in your yard.
The purpose of stormwater pits
Rising sea levels, severe weather events, and increased precipitation as a result of climate change are creating the potential for more frequent flooding.
In many areas of Grand Rapids Michigan, they have been building underground cisterns to store excess water during heavy rains instead of letting it rush into the sewers and overwhelm them.
They allow raindrops to accumulate in their design and slowly funnel the water into nearby creeks and rivers.
I’ve seen them in my area, they are basically concrete pits in the ground.
In a city that gets an average of about 40 inches of rainfall per year, these small depressions are becoming more common as a way to deal with increased precipitation during heavy storms.
They are created by removing soil and vegetation from a depression in the ground.
Materials such as gravel, sand, and rocks are then used to build up the sides of the pit and keep it from overflowing during heavy rainfall events if they don’t already have a system for managing runoff in place.
In addition to reducing strain on the city’s sewer systems, outdoor recreational spaces like trails, biking paths, basketball courts, and dog parks have plenty of opportunities to take advantage of these pit’s water storage capabilities.
Ideal depth for a drainage pit
Ponds and drainage pits are necessary features of a landscape to prevent water from pooling or flooding on the surface.
They provide a habitat for aquatic plants and animals, reduce runoff, and give an aesthetically pleasing focal point in a yard.
I’m sure you’ve noticed that drainage ponds can be built both above ground and below, but this article will focus on drainage pits.
Drainage pits collect excess subsurface water from heavy rainfall or irrigation, drain it away from surrounding areas, and prevent groundwater from pooling.
A drainage pit should be at least 3 feet deep.
If the pit is shallower, water will fill it up, overflow on the surface of the soil, and still accumulate around the site.
If a drainage pit is deeper than 4 feet, it may be difficult or impossible to dig without machinery.
Since most pits are relatively small in area—less than 20 square feet—an 36 or 48-inch depth is usually sufficient.
Even smaller pits should be dug 3 to 4 inches below the final grade of the surrounding yard in order for water to flow out of the opening.
However, if a larger area like an entire yard requires drainage, it may be necessary to dig a deeper and larger pit.
Placement of the drainage pit is the most important factor.
It should be placed in an area where water pools or collects, and away from other landscaping features like trees or fences.
How to raise a stormwater pit
Lawns and gardens can be lovely places for people to sit and relax or grow vegetables.
Unfortunately, what you don’t see is the stormwater that flows through your yard every time it rains.
This water comes from your roof, down your driveway and sidewalks, through gutters, and over pavement to the storm drain in the street.
As much as 60 percent of rainwater can go into this drainage system.
That means only 40 percent stays in the ground, where it recharges groundwater to help prevent drought.
By diverting water into landscaping beds, you can keep your garden lush and healthy while retaining the natural resources that support our communities.
If you are building or repairing an impervious surface such as a driveway, sidewalk, porch, or patio, you can capture that water and use it to replace or reduce the amount of potable (drinking) water you need.
At the same time, this “greywater” is an ideal source for irrigating your garden.
The first step in creating a healthy yard with a site-built stormwater pit is finding out what local codes say. In most areas, a building permit is required for a site-built stormwater pit, and guidelines often specify how much water it must retain and how long the rain has to stay in the pit before draining away.
The U.S. Environmental Protection Agency offers model stormwater regulations at its website: https://www.epa.gov/npdes/stormwater-rules-and-notices.
When building a stormwater pit, you can work with prefabricated collars or pre-made concrete slabs on top of the pit and then raise it to the level of the surface surrounding it using gravel or soil.
To keep costs down, reuse materials that are available on-site, such as soil, rocks, logs, gravel, and flat stones.
Stormwater could be collected in the pit using a downspout diverter from your roof, or you can divert runoff from your driveway or other surfaces into the pit with a swale (a shallow trench filled with gravel) and French drain.
Then, when it’s raining, water will fill the pit and saturate the soil below.