336-431-5852
aceavant@aceavant.com
5358 Poole Rd, Archdale, NC 27263
336-431-5852
aceavant@aceavant.com
5358 Poole Rd, Archdale, NC 27263
Sediment basins, sediment traps, and stormwater sediment control for permitted construction sites across North Carolina
We construct sediment basins to the volume and surface area required by the permit for the drainage area they serve, not to a standard size applied across every site.
Basin design, outlet structure, and emergency spillway are built to NCDEQ standards and verified before the contributing drainage area is disturbed.
We install baffles as part of the basin construction scope, so the full system is operational from the first storm event.
We clean accumulated pond sediment before it reaches the one-third capacity threshold that triggers a permit violation.
For drainage areas that do not require a full basin, we install sediment traps sized to the contributing area and construction timeline.
Riprap aprons, energy dissipators, and outlet channel protection are included where the basin design requires them.
Basin construction is phased ahead of clearing and grading so the system is in place before the first runoff event from a disturbed area.
Sediment basins, silt fence, pond baffles, diversion ditches, and stabilization handled by the same team.
A sediment basin is a constructed pond that captures runoff from a disturbed construction site and holds it long enough for suspended soil particles to settle out before the water is discharged. On permitted construction sites, sediment basins are the primary sediment control structure for drainage areas too large to be managed by silt fence and sediment traps alone. Water enters the basin from the disturbed site, slows as it spreads across the basin surface area, and sediment settles to the basin floor while cleaner water exits through the outlet structure. The basin accumulates sediment over time and must be cleaned out regularly to maintain its storage capacity and keep the system functioning through the full construction period.
A sediment trap is a smaller, simpler version of a sediment basin used for drainage areas below the threshold that requires a full basin. Sediment traps are typically constructed by excavating a small ponding area and installing a stone outlet rather than a pipe and riser outlet structure. They are used for smaller disturbed areas, shorter construction windows, and locations on the site where a full basin is not warranted by the drainage area but runoff still needs to be captured and treated before leaving the site. On most commercial construction sites, sediment traps are used throughout the site for smaller drainage areas while the main basin handles the primary site drainage.
The distinction between a sediment trap and a sediment basin is primarily one of size and drainage area. Sediment traps are used for drainage areas up to one acre. Sediment basins are required for larger drainage areas where a trap does not have the surface area and volume to provide adequate settling time. Construction is also different. Sediment traps are typically small excavated areas with a stone outlet that can be constructed quickly with minimal equipment. Sediment basins require more substantial construction including proper outlet structures, emergency spillways, and in many cases pond baffles to prevent short-circuiting between the inlet and outlet. Both are temporary erosion control structures that are removed after the site is permanently stabilized.
We construct sediment basins from the grading plan outward, starting with the basin excavation and embankment, then installing the outlet structure, emergency spillway, and riprap protection before the basin goes into service. Basin location is determined by the erosion control plan, typically at a low point in the site drainage where runoff from the disturbed area can be directed to the basin without crossing areas that are already graded or stabilized.
We establish the basin footprint, outlet structure location, and embankment alignment before excavation begins, confirming that the basin location and orientation match the permit drawings and field drainage conditions.
The basin is excavated to the design volume, with spoil material used to construct the embankment where the design calls for it. Embankment compaction is performed to the specification required for the outlet structure load and the storage volume the embankment must contain.
The riser and barrel outlet structure is installed to the design elevation, providing the principal spillway that controls the normal discharge rate from the basin. Outlet structure installation is the most critical detail in sediment basin construction because a failed outlet releases the full basin volume downstream with no sediment treatment.
The emergency spillway provides an overflow path for storm events that exceed the principal spillway capacity, directing overflow across a stabilized section of the embankment rather than overtopping and eroding an unprotected area. We construct emergency spillways to the design dimensions and stabilize them with riprap or vegetation before the basin goes into service.
Pond baffle installation
Baffles are installed across the basin before it receives runoff, positioned to divide the basin into cells that force water to travel the full basin length before reaching the outlet.
Inlet and outlet protection
Riprap aprons and energy dissipators are installed at the basin inlet to prevent scour from concentrated inflow, and at the outlet to protect the discharge channel from erosion.
A sediment basin that is not maintained loses its effectiveness as pond sediment accumulates and reduces the available storage volume. NCDEQ requires that sediment be removed when accumulation reaches one-third of the design storage volume. On active construction sites with significant disturbed area, basins can reach that threshold faster than expected, particularly after large storm events that move significant sediment volumes across the site. We provide scheduled sediment basin maintenance that includes regular inspections, pond sediment removal before the one-third threshold is reached, outlet structure cleaning, and repair of any erosion or damage to the embankment and spillway after storm events.
Removing accumulated pond sediment from a basin requires equipment that can access the basin floor and move material without damaging the outlet structure or embankment. We use excavators and tracked equipment sized to the basin dimensions, removing sediment and stockpiling or hauling material depending on the project site conditions. Sediment removal is documented and reported as part of the SWPPP maintenance record for the project.
On some sites, particularly road construction and linear infrastructure projects, water and sediment control basins are used as a combination structure that both redirects surface drainage and captures sediment from the disturbed corridor. These structures combine the function of a diversion ditch and a sediment basin in a single installation, intercepting runoff from the disturbed area and treating it before discharge. We construct water and sediment control basins to the design dimensions and maintain them through the construction period the same way we maintain conventional sediment basins.
Sediment basin design in North Carolina is governed by NCDEQ erosion and sediment control standards, which specify minimum surface area, volume, and outlet structure requirements based on the drainage area the basin serves. We work from the permitted erosion control plan on each project, constructing basins to the design dimensions and outlet structure specifications shown in the permit drawings. If field conditions require modifications to the basin location or design, we coordinate with the engineer of record and the permitting authority before making changes that could affect permit compliance.
Sediment basins are installed at the beginning of a construction project and maintained until the site is permanently stabilized and the permit is closed out. Throughout the construction period, basin performance depends on regular inspection, timely sediment removal, and prompt repair of any damage from storm events or construction equipment. We manage sediment basin maintenance as an ongoing scope from installation through permit closeout, so basin performance does not degrade as the project progresses and permit inspections continue.
Sediment basin construction must be complete before the drainage area it serves is disturbed by grading or clearing. We schedule basin construction as one of the first operations on a new project, coordinating with the site grading schedule to confirm the basin is operational before any upslope disturbance begins. Maintenance scheduling is established at project kickoff and adjusted based on storm frequency and sediment accumulation rate as the project progresses.
A sediment basin is a constructed pond on a construction site that captures runoff from disturbed areas and holds it long enough for suspended soil particles to settle out before the water is discharged.
Sediment traps are used for smaller drainage areas, typically up to one acre, and are constructed as simple excavated ponding areas with stone outlets. Sediment basins are required for larger drainage areas and involve more substantial construction including outlet structures, emergency spillways, and pond baffles.
In North Carolina, sediment basins are required when the contributing drainage area exceeds the threshold manageable by sediment traps, as determined by the NCDEQ erosion and sediment control standards and the permitted erosion control plan for the project.
NCDEQ requires sediment removal when accumulation reaches one-third of the design storage volume. On active construction sites after significant storm events, basins can reach that threshold faster than the scheduled inspection interval, which is why post-storm inspection is part of our maintenance scope.
Follow the project engineer and the curing plan. We will advise on realistic windows based on mix strength and site conditions.
Yes, on basins above a certain size, baffles are required by the permit to prevent short-circuiting between the inlet and outlet. We install baffles as part of the basin construction scope so the full system is operational before the basin receives runoff.
Once the site is permanently stabilized and the erosion control permit is closed out, temporary sediment basins are removed, the area is graded, and the disturbed area from the basin removal is stabilized. Some basins are converted to permanent stormwater management features if the site design calls for it.
Yes. We assess the current basin condition, bring it into compliance if needed, and take over ongoing maintenance through permit closeout.