On a construction site, stockpiles can seem like a relatively minor stormwater concern. A pile of soil, sand, gravel, mulch, or other material may sit in one location for days or weeks without causing an obvious problem. But when rain or runoff reaches an unprotected stockpile, sediment and other pollutants can quickly leave the site.
That is why simply having a stockpile containment measure in place does not necessarily mean the site is protected. The real question is whether the containment is working.
What Is a Construction Stockpile?
Stockpiles are temporary piles of materials that are stored on a construction site for later use. They can either be active, or inactive. Common examples include soil, aggregate, sand, gravel, topsoil, mulch, and excavated material.
Because these materials are often loose and exposed, they can become a significant source of sediment if stormwater comes into contact with them. Wind can also move fine material around the site, while vehicle and equipment traffic can disturb the pile and its surrounding area.
The location and condition of a stockpile therefore matter just as much as the material itself.
What Does Stockpile Containment Look Like?
There isn’t necessarily one single BMP that works for every stockpile. Containment will also look different if a stockpile is active or inactive. According to the CDPS COR4000000 permit, if a stockpile is active, the permittee must implement and maintain control measures necessary to minimize the discharge of pollutants. If a stockpile is inactive for more than 14 days, it must be properly contained and temporarily stabilized.
Depending on the site and material, contractors may use containment practices such as:
- Temporary stabilization (seeding/hydromulch)
- Plastic sheeting or other covers
- Silt fence, big reds, or other perimeter controls
- Berms or diversion measures
- Sediment control logs around the downslope perimeter
- Keeping stockpiles away from drainage paths and inlets
- Properly locating and managing the material within the construction site
The goal is straightforward: keep stormwater from washing through or around the stockpile and carrying sediment off site.
Is the Containment Actually Working?
This is where inspections become important.
A stockpile might technically have a BMP installed around it, but the BMP may no longer be functioning as intended. It’s important to look beyond whether the BMP exists and evaluate whether it is actually controlling the potential source of sediment.
Common questions an inspector asks:
Is the perimeter control installed correctly?
A control that is too far away, improperly installed, damaged, or overwhelmed by runoff may provide little protection. Inspectors look for gaps, undermining, overtopping, accumulated sediment, and other signs that runoff is bypassing the control.
Where is the water going?
A stockpile located directly in the path of concentrated runoff can create a problem even if a BMP surrounds it. If water is flowing toward the pile and then around or through the containment, sediment can be transported to downstream areas, streets, storm drains, or receiving waters.
Is sediment leaving the stockpile area?
Sediment trails, deposits, rills, muddy runoff, or sediment accumulation outside the containment area can indicate that the BMP isn’t adequately controlling the stockpile.
Stockpile Containment Requires Maintenance
Even a properly installed stockpile BMP won’t remain effective without maintenance.
After significant precipitation or runoff events, contractors should evaluate the condition of the stockpile and its controls. Damaged perimeter controls may need to be repaired. Accumulated sediment may need to be removed. Covers may need to be secured or replaced. And if the stockpile has grown or moved, the containment measures may need to be adjusted.
This is particularly important on active construction sites where material is constantly being delivered, moved, and used.
Final Thoughts
Stockpile containment isn’t about simply putting a BMP around a pile and checking it off an inspection form. Effective stormwater management requires looking at the entire situation: the material, the location, the runoff, the containment, and the condition of the surrounding area.
If sediment is escaping, runoff is bypassing the controls, or the BMP is damaged or improperly maintained, the presence of the BMP alone isn’t enough.
Effective stormwater compliance means identifying those problems and addressing them before they become larger issues.
At Summit Services Group, our stormwater compliance inspectors evaluate BMPs based on actual site conditions—not just whether a BMP is present. From routine inspections to corrective action tracking, our team helps contractors and owners identify potential issues and keep their projects moving toward compliance.