After fresh grading, loose soil is exposed to rainfall, which can carry sediment away from the job site and into local water systems. The storm drain is the quickest route.
Sediment-laden runoff is subject to tight regulation on construction sites. Any water flowing across disturbed ground brings sediment into curbs and drop inlets, and from there into underground storm sewer systems. Once sediment has entered that drainage infrastructure, your crew could face stormwater compliance violations and fines, not to mention expensive cleanup work.
Proper inlet protection captures sediment in the runoff to prevent those problems. However, contractors have to balance effective filtration with adequate drainage capacity. You’ll have to select products for the correct types and sizes of inlets as well as the anticipated water flow and sediment load.
Inlet protection products are one part of a comprehensive stormwater management strategy for contractors, specifiers, and distributors. Read on for guidance on how to select solutions that will protect drainage infrastructure and support regulatory compliance.
Table of Contents
Under the National Pollutant Discharge Elimination System (NPDES), construction operators are responsible for managing pollutant discharges from disturbed sites.
Federal permitting requirements generally apply to construction activities disturbing one acre or more, including smaller projects that belong to a larger common development. The EPA's construction stormwater guidance establishes this threshold, although state and municipal requirements also influence permit coverage.
The NPDES Phase II program expanded stormwater regulations to smaller construction activities and municipal storm sewer systems. Contractors subject to NPDES Phase II compliance requirements must implement appropriate best management practices (BMPs) and maintain them throughout construction.
A Stormwater Pollution Prevention Plan (SWPPP) typically identifies the controls required for a permitted project. Inlet protection devices are recognized as a BMP for controlling sediment before runoff enters public storm drainage systems. While inlet filters are an effective final line of defense to capture sediment before runoff reaches underground drainage infrastructure, they must work alongside other proactive erosion prevention measures.
Federally funded projects may have to deal with specialized procurement considerations in their product selection. For example, the Build America Buy America Act establishes domestic sourcing requirements for certain materials incorporated into covered infrastructure projects.
Since temporary inlet protection products — which are removed after construction — are generally treated separately from permanent mitigation solutions, specifiers must review the applicable funding and contract requirements before making a purchase.
Inlet protection requirements are likely to change as the construction site develops. The initial grading, utility installation, and paving phases each affect where stormwater is likely to travel and which drains are exposed to sediment-laden runoff.
The storm drain inlet protection guidance from the EPA recommends that sites always establish protection in advance of any soil disturbances in areas that drain toward stormwater infrastructure. The drainage area served by each individual inlet control, per the guidance, should also be limited to one acre at most.
Effective construction site sediment control must account for existing drainage structures near any exposed slopes, excavation areas, and soil stockpiles — areas of high risk for sediment-laden runoff. Even inlets outside the immediate work zone have to be considered (and protected) if they receive runoff from disturbed areas.
Drainage patterns will change during construction with fresh areas of excavations or the creation of new temporary access routes. As the work progresses, make sure to protect newly installed inlets before they’re exposed to runoff.
During the paving phase, stormwater begins to travel along gutter lines toward curb openings — a whole new challenge with more focused flow of water, all in one direction. Filters designed exclusively for flat grates won’t effectively protect curb-shaped inlets. Contractors need curb inlet protection appropriate for that lateral flow.
Continue to reassess inlet locations and runoff pathways as each phase advances to address any changes.
Storm drains receive runoff through a multitude of configurations and inlet sizes. There are diverse, custom-sized filtration methods on the market to match the unique requirements in different municipalities and regions.
Though there are nearly innumerable potential sizes, most inlet protection devices fall into several broad categories:
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Grate-enclosing inlet bagsGeotextile filters that completely enclose the storm drain grate rather than hanging beneath it. The grate is removed, inserted into the bag and reinstalled as a covered assembly. Products like the Dandy Bag filter sediment-laden runoff through the fabric before it enters the inlet. |
Below-grate inlet sacksOpen-top geotextile sacks suspended beneath flat storm drain grates to collect sediment as runoff enters the drainage system. The Dandy Sack and Framed Dandy Sack provide below-grate sediment containment with lifting straps for removal and maintenance. |
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Curb inlet filtersSpecialized protection for horizontal openings along curbs and gutters, where runoff approaches from the street. Products include curb bags that enclose the grate, curb sacks with below-grate sediment containment, and barriers designed for curb openings without grates. Dandy Curb, Curb Bag, and Curb Sack accommodate these different configurations. |
Above-grate filtersPop-up or three-dimensional filtration devices that extend above drop inlets to intercept sediment and debris before it reaches the grate. These devices have built-in overflow protection and typically provide accessible surfaces for cleaning. The Dandy Pop uses a dome-shaped design that encloses the grate, while the Dandy Inlet Guard features a patented three-dimensional pyramid fabric filter with built-in overflow protection for heavy rainfall. |
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Perimeter barriersFillable filters, gravel bags, wattles and weighted geotextile barriers positioned around inlet openings to slow runoff and promote sediment settling before water enters the drainage system. The Dandy Recycler is a reusable barrier shipped flat and filled onsite with recycled rubber or aggregate. |
In-basin oil skimmerFloating absorbent devices installed inside catch basins to capture oil from the water's surface. The Dandy Skimmer uses a polymer absorbent that bonds with oil and solidifies it for removal. These devices address oil contamination and complement sediment filtration rather than replacing it. |
Even within those categories, solutions can mainly be divided into above- and below-grate filters. External (above-grate) barriers rely, in part, on temporary ponding, so be sure to consider adequate drainage capacity and overflow conditions when selecting those products. Below-grate systems, by contrast, will generally preserve more of the surrounding paved surface for traffic and construction activities. They’re a great option if you need the grate to remain clear, with minimal risk of disturbance to filtration products from traffic (such as on a roadway).
Some installations combine a few of the above protection methods. For example, you may need to protect a combination curb-and-grate inlet (with a Curb Bag or Curb Sack). Regardless of configuration, the objective is to retain sediment and allow stormwater to reach the drainage system unimpeded, with no unacceptable flooding or bypass.
In your product selection, always account for the inlet's specific physical dimensions and the conditions of the surrounding drainage area. Even if a given filter fits securely under routine runoff conditions, it still needs sufficient capacity to handle the expected sediment load.
Evaluate the following four factors before you specify or purchase inlet protection devices:
In its large-scale testing of inlet protection practices, Auburn University found significant differences in sediment retention between several modified inlet protection installations. During longer-duration tests, sediment retention ranged from 49% (for a wattle barrier) to 84% (for a silt fence configuration). The study further documented a substantial disparity in drainage performance between the tested methods.
Findings like these are the reason it’s important to evaluate sediment retention and drainage capacity together. No device performs in a vacuum. Examine documented performance and installation requirements, then consider how the selected device will function under your site's expected runoff conditions. Only the combination of those factors can point you towards the most effective device.
Inlet protection is one component (the last component) of a larger erosion and sediment control strategy. The less sediment that reaches an inlet due to upstream mitigation measures, the longer your selected filtration system will remain effective — and the longer your maintenance intervals will be.
What measures can you take upstream to help? Here are a few tactics to consider:
Severe storms place intense pressure on all these control measures. To be effective with stormwater runoff management during heavy rain, crews must first identify drainage pathways and areas where storm runoff will concentrate.
In high-flow locations, water can accumulate behind obstructed inlet filters and flood surrounding pavement or bypass the protection entirely. Use upstream measures such as wattles and gravel barriers to help slow the runoff (provided their placement preserves adequate drainage).
Sediment-laden water must often be removed from excavation and utility work with water pumps. Unlike rainfall runoff, though, you have to manage pumped discharge at the outlet of the dewatering equipment.
Geotextile dewatering bags are an analogous solution to inlet filters, but they work at the outlet. The bags capture suspended sediment from pumped water, then release the filtered discharge. Make sure the dewatering bag rests on a stable drainage surface, with sufficient capacity for the pump's flow rate. Discharged water has to have a suitable route away from the filtration area that won’t cause additional erosion.
These practices are the perfect complement to inlet protection because they reduce the sediment load that reaches the downstream drains.
Regardless of the selected product, it takes a proper installation to make sure runoff moves through the filtration material and does not escape around it. Follow manufacturer instructions closely to secure each device and confirm that surrounding pavement or curb openings are appropriately protected.
The installation is not the end, though. Assign maintenance responsibilities to designated personnel on your crew. After rainfall, have the crew members check for:
Remove any accumulated sediment during these inspections so that it doesn’t compromise the device's performance. Double-check reusable filters for damaged seams or fabric before reinstallation. Don’t fall victim to common storm drain inlet protection mistakes, like unsecured devices or missed maintenance, which can lead to non-compliance citations.
Your crew must engage in routine stormwater compliance inspections to evaluate whether installed controls are continuing to function as intended. Inspectors will look for signs of sediment accumulation, damaged materials, unfiltered discharge, or inadequate drainage for site conditions. Set an inspection frequency according to permit requirements and site conditions.
Always carefully document your inspections — and corrective actions — according to the project's SWPPP and applicable permit requirements. Consistency in your records will help to show that appropriate maintenance was performed throughout construction.
Temporary inlet protection solutions are intended to remain in place until the contributing drainage area has been adequately stabilized and the applicable permit requirements allow their removal.
What counts as final stabilization? Generally speaking, stabilization means you’ve established permanent ground cover or completed other approved measures that will prevent any exposed soil from eroding. Until those conditions are satisfied, sediment remains a potential concern — even if major construction activities have finished.
Before you remove any of your inlet protection products, have the crew inspect surrounding drainage areas and remove all collected sediment. Be careful not to let it enter the storm system during removal. If your products are reusable, like ours at Dandy, clean them up and evaluate for damage.
Now you can store or transfer them to another project!
Dandy Products manufactures durable, high-visibility inlet protection solutions at our Ohio facility using domestically sourced materials.
Our product line includes reusable geotextile inlet bags, curb filters and other sediment control products for all sorts of drainage configurations and construction conditions. Whatever size you need, whatever inlet style you’re working with, we’ve got it. You can always get the right solutions, on time, with our custom sizing and established nationwide distribution network.
Explore our inlet protection products or contact the Dandy team to discuss your project specifications. We'll help identify the best solution for your inlet configuration and get you connected with a local distributor.