Not an allowed discharge
Wastewater from concrete washout is on the permit's prohibited list unless it's managed with the control in Part 2.3.4.2
CGP Part 1.3.1The starting point
Every pour ends with chutes, hoppers and hand tools getting rinsed. That water is caustic, with a pH near 12, so a stormwater permit wants it caught in something leak-proof and kept away from drains. Here's what the rules ask, the ways to catch it, and how the washout containers in our provider network were ordered.12
Why it can't go on the ground
Washwater is a slurry of cement fines, sand and metals. Dumped on bare ground, it runs to the nearest inlet or soaks in. In a stream, high pH damages fish gills and makes other pollutants more toxic. In soil, it changes the chemistry enough to stunt plants and can reach groundwater.1
It's also hard on people. Wet concrete and washwater irritate skin and can damage eyes, which is one more reason to keep it in one marked spot.1
| Liquid | pH |
|---|---|
| Safe range for freshwater life | 6.5 to 9 |
| Safe range for saltwater life | 6.5 to 8.5 |
| Concrete washwater | Near 12 |
| Liquid drain cleaner | 13.5 |
Values from EPA's concrete washout fact sheet.1
What the permit says
This is EPA's 2022 Construction General Permit, which applies where EPA is the permitting authority. Most states issue their own construction permit, and the wording can differ, so check the one your site is covered under.2
Wastewater from concrete washout is on the permit's prohibited list unless it's managed with the control in Part 2.3.4.2
CGP Part 1.3.1The starting point
Wash water goes into a leak-proof container or a leak-proof, lined pit, built so it can't overflow from being too small or from rain.2
CGP Part 2.3.4Container or lined pit
Liquid can't go into drainage features, inlets or waters, and can't be left to infiltrate. Hardened concrete is removed like your other construction waste.2
CGP Parts 2.3.4 and 2.3.3Liquids and solids
Washout happens as far as possible from waters, drainage features and storm inlets, in designated areas where feasible.2
CGP Part 2.3.4Location, shown on the site map
Ways to catch it
EPA's fact sheet walks through each of these. The right one depends on who's washing out, how many pours you have, and whether pump trucks are on site.1
| Setup | How it works | Watch for |
|---|---|---|
| Chute washout box on the truck | Mounted on the back of the ready mix truck. The driver rinses into it and takes everything back to the plant. | Only works if the supplier's trucks carry one. Ask when you order the concrete. |
| Washout bucket and pump | Hung on the end of the chute. The rinse is pumped back into the drum and returned to the plant. | Same as above. Nothing stays on your site, which is the point. |
| Hay bale and plastic pit | Dug in or built above grade, lined with plastic. Water evaporates or gets vacuumed out, then the solids get broken up. | Tears in the liner leak. Solids bound up with plastic often go to a landfill, since recyclers usually take only unmixed material. |
| Vinyl container with filter bag | Portable and reusable. The bag lifts out the solids and lets the water drain back. | Easier to set up than a pit. Bags and gelled water still need disposal. |
| Metal washout roll-off | A watertight steel bin, delivered and swapped by the provider. Some have a ramp so pump trucks can reach. | Pump truck hoppers hang low, so they may not reach a bale pit. A bin with a ramp handles them. |
A debris roll-off isn't a washout. A standard roll-off isn't watertight. EPA's fact sheet shows one leaking washwater onto the ground. If the plan is a container, ask for a washout container by name.1
What our network sent out
Delivered through 26 providers in 16 states. Most were the 20 yard size, and three in four were picked up within about 16 days.4
| Size ordered | Containers | Compared |
|---|---|---|
| 20 yard | 86 | |
| 7 yard | 13 | |
| 10 yard | 12 | |
| Other sizes and pans | 22 |
Days on site count from delivery to removal for the 130 containers with both dates. Half stayed between 2 and 16 days. Other sizes run from 6 to 30 yards, plus a few low-profile pans.
Running one
These are EPA's practices for keeping a washout from overflowing and making sure drivers actually use it.1
Put it where trucks can reach it, ideally close to the pour, but not within 50 feet of storm drains, open ditches or water. On undeveloped ground, cover the approach with gravel or rock.
With a lot of concrete work, set washouts in several spots. If drivers can't see one from the pour, put up signs pointing to it.
Look for leaks, torn liners and damaged sides, and see how full it is.
Once it's past 75 percent full, vacuum off the water or let it evaporate. When the solids harden, remove them for recycling.
Before a heavy storm, drop the liquid level or cover the container so it can't overflow.
Show ready mix drivers where it is, and write washout requirements into your contracts with concrete suppliers.
After it leaves
EPA's goal for washout is to recycle all of it. Filtered water can rinse the next chute. Hardened solids get crushed into road base or fill, and coarse aggregate screened out of the rinse can go back into concrete.1
Water that leaves the site gets treated to bring the pH down and pull out metals before it goes to a sewer plant. That plant can have pretreatment limits of its own, so it's contacted first.13 For broken slabs and demo concrete, which is a different load, see concrete disposal.
Tell us the pour dates, whether pump trucks are coming, and where it can sit. We'll line up a watertight container and the swap.
Questions
A leak-proof container or lined pit where ready mix chutes, pump hoppers and tools get rinsed after a pour, so the caustic water and solids stay out of drains and soil.
If your site is under a construction stormwater permit and washout happens on site, yes. EPA's permit doesn't allow washout water to be discharged unless it goes into a leak-proof container or lined pit. Your state's permit may say it differently, so check it.
EPA's fact sheet says not within 50 feet of storm drains, open ditches or water. The federal permit says as far away as possible. Use whichever your permit and plan call for.
No. A standard debris roll-off isn't watertight and can leak washwater. Ask for a washout container, which is built to hold liquid.
As long as the pours last. In our provider network the median container stayed 5½ days, and half stayed between 2 and 16 days.
It's reused for more rinsing, left to evaporate, or pumped out and treated to lower the pH and remove metals before a sewer plant takes it. The hardened solids get crushed and recycled.
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