Louisiana Temporary Construction Entrance BMP

Bordering the Mississippi River to the east and the Gulf of Mexico to the south, the state of Louisiana has developed a primary seafood industry supplying approximately one-quarter of the nation's domestic seafood production.

Louisiana Department of Environmental Quality

In 1972, Congress amended the Federal Water Pollution Control Act, which became known as the Clean Water Act (CWA), establishing a national permitting framework for discharges to surface waters. The Louisiana Department of Environmental Quality (LDEQ) administers the Clean Water Act through the Louisiana Pollutant Discharge Elimination System (LPDES) permit program, which enables oversight of all construction, industrial, and municipal activities that may impact the aquatic ecosystems.

Construction activities disturbing between one and five acres must obtain coverage under the Small Construction Activities General Permit (LAR200000). Activities disturbing five acres or more must obtain coverage under the Large Construction Activities General Permit (LAR100000). The construction operators will apply.

The permit application process involves preparing a Stormwater Pollution Prevention Plan (SWPPP). The Storm Water Management Plan includes components reviewed by the permit authority, including blueprints of the proposed work, potential sources of pollution and sedimentation from runoff, and a list of techniques to mitigate and reduce the impact of these pollution sources. The methods used are referred to as Best Management Practices (BMPs).

One BMP that is needed on nearly all job sites is the Temporary Construction Entrance.

Temporary Stone Construction Entrances

A temporary construction entrance is a technique used to reduce the amount of sediment and debris dragged out from job site exit points onto paved roadways. Sediment deposited on paved roadways can easily wash into storm drains and into rivers and lakes, causing harmful sedimentation. To minimize the impact on water sources, construction operators will install a temporary construction entrance to clean sediment and debris from vehicle tires as they exit the site.

Described in the Louisiana Coastal Zone BMP: Urban Storm Water Runoff Manual, a temporary stone construction entrance is built by placing a filter cloth underneath a gravel pad to stabilize the ground and to trap sediment in the rocks as vehicles leave the site. Bull rock or similar coarse aggregate should be used to ensure a rough surface is created, as it is more effective at dislodging debris. The filter cloth mentioned in the manual is used to keep the aggregate from sinking into the substrate and to prevent rutting. Typical guidance includes a minimum depth of 6 inches, a length of approximately 50 feet, and a width of 20 feet or greater, adjusted as needed to accommodate site traffic and vehicle turning movements.

The gravel pad should be wide enough to provide an exit lane for the largest vehicles that will access the site. This technique is used at any construction site exit where there is a risk of mud, dust, sediment, or debris being deposited onto impermeable roadways. The temporary stone construction entrance pad should include a turning radius when installed perpendicular to an active roadway, allowing vehicles to turn in both directions as they leave the site.

Additional BMPs may be needed to ensure stabilization at the entrance where it crosses a ditch.

After establishing the construction entrance, contractors should continue to monitor for effectiveness as the job progresses. As vehicles drive over the gravel pad, the rocks become saturated with sediment and debris and are compacted, reducing the effectiveness of the entrance. When sediment is tracked onto roadways, contractors are required to perform maintenance on the entrance, including adding aggregate or replacing the bull rock. In addition, any debris deposited on the roadway must be swept regularly before it can be washed into the storm drains.

When the temporary stone construction entrance does not adequately contain sediment and debris, a wash rack may be installed. A wash rack uses pressurized water to clean mud and debris from vehicle tires. The wash rack must have proper drainage into a sediment basin to prevent sediment-laden runoff from leaving the job site. Wash racks can provide additional sediment removal compared to stone construction entrances, but require a water source, power, and proper wastewater containment.

FODS Reusable Stabilized Construction Entrance BMP

The FODS Trackout Control Mat System is a reusable, effective construction entrance that can increase compliance with stormwater permit regulations. The system consists of a single layer of HDPE matting, which forms pyramid-shaped structures on its surface. As vehicles drive over the mats, the pyramids flex and deform the tires, allowing debris trapped in the treads to break loose. The mats will hold mud, sediment, and debris at the base of the pyramids away from tires. Each mat is 12' wide and 7' long and is typically arranged in series to create a single lane for exiting traffic; however, the system is modular and can be installed in various configurations to fit the needs of each project.

The system is highly effective at removing sediment from vehicle tires and has been shown to reduce the need for street sweeping by 59% compared to traditional rock entrances. The system is designed to be relocated and reused repeatedly, allowing contractors to avoid high costs throughout the product's 10+ year lifespan. FODS can be installed on grade or over concrete and asphalt, providing greater flexibility for urban projects. The system does not require a water source or power, allowing contractors to mitigate sedimentation and trackout in many locations and conditions effectively.

Maintenance of the FODS system is completed when 2.5" of sediment builds between the pyramids. The maintenance process involves sweeping the mats to remove sediment and is usually done with a skid steer equipped with a broom attachment or manually with a FODS shovel.

This BMP is intended as a stand-alone solution for construction site trackout.