Concrete washout areas (CWAs) are a common Best Management Practice (BMP) on construction sites, particularly on projects involving concrete foundations, slabs, curbs, sidewalks, or other concrete work. Their purpose is to provide a designated location where concrete trucks, pumps, and other equipment can wash out without releasing concrete slurry into the surrounding environment.
But simply having a concrete washout on site doesn’t mean the BMP is doing its job. A washout that is undersized, damaged, overflowing, improperly located, or not maintained can create its own stormwater compliance problem. Regular inspections are important to make sure the washout remains capable of containing concrete waste throughout the project.
What Is a Concrete Washout?
A concrete washout is a designated containment area used to collect and contain wastewater and residual concrete generated when concrete equipment is cleaned.
Concrete wash water is highly alkaline and can contain suspended solids and other materials that should not be discharged directly onto the ground or into stormwater drainage systems. A properly constructed washout provides a contained location where this material can be collected, managed, and properly disposed of.
Concrete washouts can take several forms depending on the project. Common examples include temporary lined pits, prefabricated washout containers, and other manufactured containment systems.
Regardless of the type used, the basic objective is the same: contain concrete waste and prevent it from entering stormwater runoff or leaving the construction site.
What Does a Properly Functioning Washout Look Like?
A concrete washout should be able to contain the material being placed into it without leaking, overflowing, or creating additional environmental concerns.
The containment structure should remain intact, with no visible tears, holes, leaks, or other damage. The liner should remain properly positioned and should not have pulled away from the sides or become exposed in a way that compromises containment. The washout should also have enough remaining capacity to handle additional concrete washouts.
Signs Your Concrete Washout Isn’t Working
A washout can appear to be in place while still failing to provide adequate containment.
Some warning signs include:
- Concrete slurry or wash water outside the designated containment area.
- Tears, punctures, or holes in the liner.
- Concrete waste accumulating outside the washout.
- The washout becoming too full to safely contain additional material (above 75% capacity).
- Wash water leaking into surrounding soil.
- Runoff entering or leaving the washout.
- The washout being located too close to storm drains, drainage features, or waterways.
- Concrete trucks or workers using an unauthorized location for washout.
Any of these conditions should prompt an evaluation of the BMP and whether corrective action is needed.
Capacity Is a Common Problem
Concrete washouts can fill surprisingly quickly.
Large concrete pours can generate significant amounts of residual material and wash water. If the washout is not monitored, it can reach capacity before the next concrete operation. An overflowing washout defeats the purpose of the BMP and can result in concrete waste being released onto the surrounding site. In Colorado, a CWA should be refreshed before it reaches 75% capacity.
Project teams should monitor the available capacity and plan ahead for removal or replacement when the washout approaches its usable limit. Waiting until the washout is completely full can make maintenance more difficult and increase the risk of an uncontrolled discharge.
Maintenance Is Part of the BMP
Like other stormwater controls, a concrete washout requires ongoing maintenance. Maintenance may include repairing or replacing damaged liners, removing accumulated concrete waste, replacing full containers, and cleaning up material that has escaped the designated containment area.
The washout should also be checked after significant weather events and throughout periods of active concrete work. The goal is to identify problems before the washout fails—not after concrete slurry has already left the containment area.
Don’t Forget About Unauthorized Washout Areas
One of the most common problems isn’t necessarily the designated washout itself—it’s what happens when workers use somewhere else.
Concrete trucks or equipment may occasionally wash out in areas that are more convenient but aren’t designated for concrete waste. This can create an uncontrolled source of concrete slurry and waste.
Clear signage and communication with concrete crews can help prevent this. Everyone working on the project should know where the approved washout is located and understand that concrete washout should occur only in the designated area.
Final Thoughts
Concrete washouts are a relatively simple BMP, but they serve an important purpose on active construction sites. When properly located, constructed, maintained, and used, they provide a controlled location for managing concrete wash water and residual material.
When inspecting a concrete washout, it’s less a matter of, “Is it there?” but rather,
“Does it have enough capacity, is it intact, and is it actually containing the concrete waste?”
Regular inspections and proactive maintenance can help prevent small problems from becoming larger stormwater compliance issues.
At Summit Services Group, we help contractors across Colorado with stormwater inspections, SWMP management, BMP evaluations, and ongoing compliance support. Our goal is to help project teams keep their stormwater controls functional and their projects moving forward.