Rain and snow — nature's cleanest sources of fresh water. In a perfect world, that water would just soak right into the earth. But between pavement, buildings, and other hard surfaces, storm runoff picks up all kinds of grime before it flows into our water supply. Gross, right?
But here’s the good news: Engineers across the globe are working hard on ways to keep runoff from tainting our rivers, lakes, and oceans. In this blog, we’ll explore why stormwater is such a giant problem and how engineering companies like Verdantas are helping to solve it.
What’s the Importance of Stormwater Testing?
According to the U.S. Environmental Protection Agency (EPA), stormwater runoff is currently one of the greatest threats to clean water in the U.S. It can also cause erosion, flooding, and health issues for people, plants, and animals.
In order to tackle this challenge, it’s helpful to understand what stormwater runoff typically contains in a certain area and exactly how it interacts with its surroundings.
What Are the Common Pollutants in Stormwater Runoff?
Stormwater isn’t all the same. Here are the most common — and most problematic — things scientists find in it:
- Cooking oil and household cleaners
- Motor oil, antifreeze, and gasoline
- Pesticides and fertilizing nutrients like nitrogen and phosphorus
- Soil
- Trash
- Pet waste and animal manure
- Disease-causing bacteria, protozoa, and viruses
- Paint and construction debris
How Does Runoff Affect Humans, Plants, and Animals?
While stormwater is a problem in many places, it’s especially bad around urban and suburban areas where there’s more pavement.
Have you seen signs around certain lakes and ponds saying they’re not safe for swimming? That might be because they contain too much nitrogen and phosphorus (fertilizing nutrients), which often cause algae blooms that can be fatal to humans and pets. These ingredients also lower oxygen levels in the water, which can have a negative impact on fish and other aquatic species.
Stormwater runoff often contains a number of bacteria, viruses, and organisms that can make people really sick. We’ll spare you the details. But we gathered a few stats that aren’t pretty either…
Stormwater Runoff Statistics
- Used oil from one oil change can pollute up to 1M gallons of freshwater
- 1 oz. of bleach requires 312,000 oz. of water to be safe for fish
- People who swim near flowing storm drains are 50% more likely to experience symptoms of ill health
- Americans improperly dump about 193M gallons of used oil every year
How Do You Measure Stormwater Runoff?
If you work in landscaping or you’re a site developer — or if you just want to help, the EPA has designed a stormwater calculator to give you a better sense of how much runoff is leaving a certain property each year.
But when it comes to understanding exactly what’s in that runoff, you’ll probably need the help of a scientist or engineer who can test it. Now, most methods of evaluating stormwater are equally good, but our team wanted to take a closer look at testing runoff sediment.
And…that’s where things get a little hairy. If you want to geek out with us, check out this next segment, or feel free to skip ahead!
Laboratory Analysis and Testing Methods Regarding Sediment
There are two main tests that people like to use when looking at stormwater sediment: mass balance (MB) and effluent sampling. And if you wonder if there’s some kind of scientific rivalry between the two, the answer is yes! Listen, we scientist types like a little drama with our stormwater, okay?
Mass Balance vs. Effluent Sampling
Okay, now here’s the hairy part: MB uses the captured mass and injected mass of sediment to produce a single removal efficiency value. Effluent sampling, on the other hand, uses the calculated influent concentration and average of “snapshots” of the effluent concentration to determine the overall removal efficiency. Say that five times fast!
Between MB and effluent sampling, there’s no clear winner when it comes to producing detailed, reliable results for the most part. However, when it comes to which test is better for sediment, we put the tests to the test!
Our Test
We used a 4-foot-diameter stormwater manufactured treatment device at 2 selected flows of 0.25 cubic feet per second (cfs) and 1.0 cfs. We tested each flow using a variety of testing and collection methods:
- Mass balance
- End-of-pipe effluent sampling, 2-L beaker (EOP-2L)
- End-of-pipe effluent sampling, 1-L bottle (EOP-1L)
- In-line effluent sampling, 1-L bottle
- Isokinetic effluent sampling, 2-L beaker
To learn more about our specific methodologies, design, system setup, and more, click here to read our full study!
The Winner
We found that mass balance testing produces more consistent, reliable data! So take that, team effluent sampling!
How Is Stormwater Regulated in the US?
Because stormwater runoff is such a serious issue (and not everyone does the right thing), regulations have been developed to help protect our waterways and discourage harmful practices. Most stormwater regulations fall under the Clean Water Act (CWA), which is enforced by the EPA.
Complying With Stormwater Regulations
Have a commercial or industrial property? If your facility releases anything other than pure, fresh water at roughly the same temperature as any bodies of water it’s entering, you will need a National Pollutant Discharge Elimination System (NPDES) permit.
However, in order to get that permit, you’ll also need to provide a Stormwater Pollution Prevention Plan (SWPPP) that outlines how your facility will prevent water pollution. Verdantas scientists are ready to help!
Stormwater Detention, Stormwater Treatment, and How an Engineering Company Can Help
At Verdantas, environmental assessment and remediation is one of our specialties, but our experts are also highly experienced in providing regulatory support.
Fortunately, relatively simple and inexpensive solutions like stormwater retention ponds can be highly effective at preventing toxins and garbage from getting into waterways. Other stormwater treatment measures — like sand or organic filters, permeable pavement, and green roofs — can also work wonders.
Every building and every site is different, so the same solution that worked well for one location might not be the best for another. That’s why an environmentally-minded engineering company will take into account the land, changing weather patterns, and any likely contaminants before suggesting a fix. Our scientists and engineers have been actively involved in the development and implementation of several laboratory stormwater verification testing protocols and standards. It’s…kind of our jam.
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