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Is Washout Really That Bad?

Andrew Shipp
Feb 114 min read

I’m going to let you in on a dirty little ‘not-so-secret’ secret of the homebuilding world and weave in some interesting facts along the way that may surprise you.


It happens all the time. Whether it’s painting, concrete pours, mortar work (stucco/stone/brick/tile), or other tasks, when workers finish a job, they are left with dirty tools and often excess materials. The next logical step is to clean off the tools and dispose of said excess materials, but what’s the best way to do this? The often-used method is to grab a hose and wash off the tools in the dirt, and then also dump the materials in the dirt. This is referred to as “washing out on grade.” What’s the big deal? The Earth will take care of it, right? Wrong. Those materials are filled with harmful chemicals that can have major impacts.


Having managed construction sites myself, I can understand why workers have been washing out directly onto the soil for so long. It’s easy. If you’ve ever worked on a construction site, you know they are fast paced. To these workers, time is money and the quickest way to “clean up” is to dump right where they are and move on.


Exactly what chemicals are in paint and concrete-based products (stucco, mortar, and concrete)?


Interesting Fact #1: Many of the chemicals potentially found in washout are either toxic or a known carcinogen… and some are both:

  • Paint: Benzene (a carcinogen), Formaldehyde (a carcinogen), Methylene Chloride (toxic), Styrene (a carcinogen), Mercury (toxic), Glycol (toxic), Isocyanates (toxic), Ammonia (toxic), Copper, Zinc, Lead, Cadmium (toxic), Chromium (toxic), and traces of other toxic metals

  • Concrete: Chromium (toxic), Hexavalent chromium (carcinogen), Lead (toxic), Mercury (toxic), Copper, Iron, Aluminum, Barium, Copper, Magnesium, Manganese, Nickel, Potassium, Selenium, Sodium, Vanadium, and Zinc


Interesting Fact #2: According to the MIT Office of Sustainability, concrete is the second-most used substance in the world. To the tune of approximately 14 billion cubic meters per year, the only substance we use more of is water. That’s a lot of concrete, and a lot of potential contamination washed onto the ground. Not to mention the amount of embodied carbon produced.


Interesting Fact #3: According to the Environmental Protection Agency (EPA), concrete washout has almost the same pH level as Drano® liquid cleaner (pH 12 versus pH 13.5). This means that it is caustic and corrosive, and clearly not meant to be dumped in any location. Safe pH levels for aquatic wildlife are between pH 6.5 – pH 9. Much lower than that of washout.


Interesting Fact #4: According to the Marion Country Conservation District, it would take 800 gallons of clean water to properly dilute 1 gallon of concrete washout. Makes you wonder when you see how much washout your stucco contractor sprays on the ground after only one house. I believe that people haven’t been properly educated on what chemicals are part of the building products they are washing out and therefore cannot know the full extent of damage they are causing.


So what are the potential negative impacts of washout? To name a few:

·       Inhibited plant growth in soil

·       Contaminated rivers, streams, lakes and oceans

·       Impacted wildlife, particularly aquatic wildlife

·       Contaminated ground water

·       Harmful effects to humans

·       And lastly for all the home builders still reading, poor customer perception


What can be done to mitigate washout on construction sites?


First and foremost, there are laws and regulations in place at the Federal, State, and Local levels that are designed to protect the environment and prohibit actions like washout. The practices that builders use to ensure they are meeting these regulations are referred to as a SWPPP (Stormwater Pollution Prevention Plan).


The most useful method in directly preventing washout on grade is for builders to provide proper washout stations on site, with the best practice of having one on each individual lot. Examples of different types of washout stations include:


Sealed, metal containers: These are either roll-off bins or portable metal pans that are fully sealed to prevent leakage. These are the most expensive option, but they are also the most durable. Regular garbage dumpsters do not apply because they often have holes and can leak the liquid on the ground.


“Hay bale and liner” method: This method involves forming a “U” shape with hay bales (usually around 10ft in diameter) and then placing a continuous plastic liner over the entire area. Trades can pull-up their vehicles on the open end of the “U” to washout. The plastic, which should not have any holes or open seams, forms a catch basin for washout, and the hay bales create a dam on the sides and back to prevent washout from running off the edges. These are in-expensive; however the plastic is easily damaged throughout construction and will often need to be re-installed or completely replaced. Hay bales can be replaced with other products to create the U-shaped dam. These can also be as simple as digging a hole in the ground and placing the plastic liner over the hole.


Cardboard boxes with liners: These are exactly as they sound – typically 4’x4’ cardboard boxes with a plastic liner installed in the box. Because they are one of the smallest and least expensive styles of washouts, they are a great option to allow a builder to put one on every lot.


“Open hole in the ground” method: Dig a hole and then pour washout into the hole. Yes, this is a method builders use, but it's not a good one. Let’s be clear – this does nothing to stop contaminants from seeping into the ground. Please stop using this method… or at least pay the extra cost to line the hole with plastic.


There has been a recent surge in heightened awareness of harmful chemicals and the impact they have on our environment and bodies. In fact, on January 15, 2025 (one day ago as I write this article), the FDA banned the use of “red dye No. 3” in foods. If we know that products like paint and concrete are unsafe to be washed into the ground, the homebuilding industry should make it a goal to show the public that not only do we strive for safe homes, but we do our part to keep the environment safe for our communities as well.


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