Inlet protection is a term used to describe a temporary sediment control measure routinely constructed in the drainage area surrounding a storm drain, curb inlet, or drop inlet. Typically installed in areas with unstabilized land, inlet protection is designed to divert water laden with sediment and other contaminants from entering the drainage system.

Construction, utility work, landscape renovations, and other land development activities can produce debris like sediment or create non-stormwater discharges that stormwater runoff can pick up. Often, these activities are carried out in areas where those discharges end up in the gutter or street and subsequently nearby storm sewer inlets and local streams. Frequently, these discharges even clog entire drainage systems.

Temporary controls can be used to protect storm sewer inlets and prevent incursions or at least minimize the volume of polluted stormwater runoff and non-stormwater discharges entering a drainage system. The techniques involved include the installation of protective devices at the inlet or the implementation of temporary runoff capture devices close to the activity.

Techniques to Prevent Pollution

Inlet protection devices need to be constructed in order to ensure that the cleaning and removal of trapped sediment or captured contaminants can be done as easily as possible. When an activity has been initiated that could result in an increase in the potential of stormwater being polluted or the generation of non-stormwater runoff, flow patterns from the site should be observed to determine whether or not flows are capable of entering gutters and streets and reaching a storm sewer inlet. During the activity, inspections should be carried out on the control devices that have been installed to make sure they are working in the intended manner. Methods such as wet/dry vacuum can be utilized to remove sediment and non-stormwater runoff that has been captured.

Types of Inlet Protection Devices

Inlet protection devices vary based on the needs of the project site. They can include compost and fiber logs, silt fence enclosures, rock and gravel filters, straw or hay bale barriers, and more structural devices like concrete block/gravel/mesh wire setups. The right inlet protection device is determined by the type of storm drain inlet, whether it’s a curb inlet, drop inlet, or other inlet structure. Some commonly used devices include:

• Drop inlet baskets: Strategically deployed to trap sediment in larger construction areas, ensuring stormwater runoff is filtered before entering the drainage system.
• Silt fence enclosures: Used to protect surface drainage ditches from excessive runoff, preventing sediment from polluting nearby water bodies.
• Gravel filters and hay bale barriers: Effective for erosion control and stormwater management, helping to capture sediment and manage stormwater flow across construction sites.
• Rock check dams: Installed at key points to slow down stormwater flow, allowing sediment to settle and preventing erosion in critical areas.
• Sediment filters: Designed to capture and filter out sediment from stormwater runoff, preventing pollutants from entering storm drains and water bodies.
• Erosion control blankets: Used to stabilize soil and prevent erosion, particularly on slopes or disturbed areas, while encouraging vegetation growth.

In areas with only surface drainage ditches, stabilization practices, and perimeter controls are essential to mitigate sediment runoff. The proper choice of inlet protection device can prevent sediment buildup and ensure stormwater flows freely, avoiding clogs in the system.

Design and Installation Considerations

The design and installation of inlet protection devices require careful consideration of several factors, including the type of inlet, drainage area, slope, and traffic conditions. Inlet protection devices can be fabricated from clean aggregate, filter fabric, or other materials, or an appropriate device can be selected from the many commercial products available for construction site stormwater management. Devices that are bulky or result in deeply ponded water and sediment deposits may not be appropriate for inlets on or immediately adjacent to public roadways. Selecting the right device ensures effective sediment control and minimizes the risk of flooding or other issues.

Best Practices for Inlet Protection Installation

To ensure that inlet protection measures are effective, proper installation is essential. For example, using filter fabric or placing concrete blocks lengthwise across the inlet can help slow down the flow of stormwater while allowing sediment to settle. It is critical to ensure that devices are installed before soil disturbance occurs. Sediment control practices such as installing sediment traps or using temporary sediment traps during construction can help prevent sediment from entering the storm drain system. Regular inspection and sediment removal are crucial for ensuring that the storm drain drop inlets are functioning correctly.

Storm Drain Maintenance and Sediment Control Practices

Maintaining the efficiency of storm drain systems requires routine checks to avoid clogging and ensure stormwater drainage systems are working as intended. Sediment control practices should include the removal of accumulated sediment and the cleaning of storm sewer inlets regularly to prevent flooding and blockages. For example, clogging storm drain pipes can occur when soil disturbance from construction allows excess dirt and debris to enter the drainage area. Using a combination of sediment filters, gravel filters, and drop inlet baskets can help prevent debris from making its way into the drainage system, ensuring continuous storm flow.

The Role of Sediment Traps and Filters in Erosion Control

Sediment traps play a key role in managing runoff and preventing erosion. Trap sediment devices, such as stone filters and silt fences, are used to stop sediments from entering the drainage system and causing long-term blockages. Temporary sediment traps made from coarse aggregate are highly effective during construction phases when sediment movement is at its highest. Using erosion control methods in conjunction with inlet protection devices ensures that sediment is contained before it enters the system, protecting both surface and subsurface drainage areas.

Inlet Protection for Surface and Subsurface Drainage Systems

It’s essential to differentiate between surface drainage ditches and subsurface systems when planning inlet protection. Surface systems, including storm drains, often require open-channel solutions like hay bale barriers, while subsurface systems may benefit from excavated impounding areas or gravel filters to prevent sediment from clogging drains. Temporary devices, such as drop inlet baskets or wire mesh structures, can be deployed in both surface and subsurface systems, depending on the drainage area and the project’s specific needs.

Temporary vs. Permanent Solutions for Storm Drain Protection

Choosing between temporary and permanent measures for storm drain protection depends on the project’s scope. Temporary measures like excavated traps and concrete block barriers are ideal for short-term projects, while permanent installations like storm drain systems designed to handle stormwater runoff are more suitable for long-term use. In larger projects, perimeter controls such as hay bale barriers combined with filter fabric provide added layers of protection. By using these stormwater management techniques, you can reduce the likelihood of bypass flow and other drainage issues.

Advanced Sediment Control Techniques

For projects that demand more advanced techniques, sediment control methods such as using wire mesh in conjunction with gravel filters or setting up silt fence enclosures are highly effective. Perimeter controls can be used to create barriers that trap sediment while still allowing water to flow through. The use of excavated traps, hay bale barriers, and stone filters provides robust protection against sediment entering drainage systems. It’s also important to note that materials such as coarse aggregate or wire mesh may be needed for projects involving large volumes of sediment.

Costs and Benefits

The estimated cost of inlet protection devices can vary depending on the type and size of the device, as well as the materials used. However, the benefits of inlet protection far outweigh the costs. Properly selected, installed, and maintained inlet protection devices can remove 25 to 35 percent of total solids and 15 to 25 percent of nutrients from incoming flows. This helps protect surface and subsurface systems from damage and contamination. Additionally, these devices can help prevent the clogging of storm drain pipes, ditches, and downgradient sediment traps or ponds, reducing the need for costly maintenance and repairs. Investing in effective inlet protection is a cost-efficient way to ensure long-term environmental and infrastructural health.

Other Factors to Consider

When dealing with non-stormwater discharges, it’s important to use capture devices such as inlet covers and check dams to temporarily contain and then remove runoff. Captured materials, including sediment and pollutants, should be properly disposed of to avoid contamination. Regularly cleaning inlet protection devices is critical to maintain the flow of stormwater and avoid clogging of storm sewer inlets. Additionally, it’s important to ensure that materials such as landscape waste, gravel, or broken asphalt are not placed near storm drain inlets to prevent blockages.

Muller, Inc. operates crews trained in the installation of many different types of inlet protection throughout the Northern Virginia, Maryland, and DC Metro area. Email estimating@mullerec.com or call 202-701-1363 to find out more today.