New Hampshire Temporary Construction Exit BMP

New Hampshire Stabilized Construction Entrances and Trackout Control

EPA Construction General Permit and NHDES Alteration of Terrain Compliance

New Hampshire's water resources shape nearly every construction project in the state. The Merrimack and Connecticut rivers, the Great Bay estuary and the Piscataqua seacoast at Portsmouth, Lake Winnipesaukee and the Lakes Region, and the cold headwater streams of the White Mountains all depend on clean runoff. Because so much of the state drains to sensitive surface waters and public drinking supplies, controlling erosion and keeping construction sediment out of the road is a core compliance duty on New Hampshire sites. A stabilized construction entrance is one of the first and most visible controls an inspector looks for.

New Hampshire is unusual in that two separate permitting tracks apply to construction stormwater, one federal and one state. Understanding which agency requires what is the key to specifying the right construction exit and staying in compliance.

Federal NPDES Coverage: EPA Construction General Permit

New Hampshire is one of the few states that did not seek delegation of the National Pollutant Discharge Elimination System (NPDES) program, so the U.S. Environmental Protection Agency, through EPA New England in Region 1, is the permitting authority for construction stormwater. Construction that disturbs one acre or more, or that is part of a larger common plan of development of that size, requires coverage under the EPA Construction General Permit (CGP).

EPA reissued the current CGP on February 17, 2022, and it runs through February 2027. Operators obtain coverage by preparing a Stormwater Pollution Prevention Plan (SWPPP) and filing a Notice of Intent through EPA's NPDES eReporting Tool (NeT). The CGP requires erosion and sediment controls at the site, including measures to minimize the tracking of sediment off site, along with regular inspections, maintenance, and a posted public notice of permit coverage.

State Coverage: NHDES Alteration of Terrain Permit

Alongside the federal permit, the New Hampshire Department of Environmental Services (NHDES) administers the state's own construction stormwater program through the Alteration of Terrain (AoT) permit, issued under RSA 485-A:17 and the Env-Wq 1500 rules. The AoT program protects surface waters, drinking water supplies, and groundwater by controlling erosion and managing runoff from disturbed land.

An AoT permit is required when earth-moving activity, measured cumulatively over a ten-year period, disturbs more than 100,000 square feet of terrain, or more than 50,000 square feet when any part of the disturbance falls within the protected shoreland defined by RSA 483-B. The AoT application requires an erosion and sediment control plan, and all erosion control measures must be in place before earth disturbance begins. Under the program, a site is considered stabilized when its soils will not erode under the conditions of a ten-year storm. Because the AoT and CGP thresholds differ, many New Hampshire projects must satisfy both, and a single well-chosen construction exit can serve both plans.

Stabilized Construction Entrances in the New Hampshire Stormwater Manual

The New Hampshire Stormwater Manual is the state's primary technical guidance for erosion and sediment control during construction, and it directs operators to use temporary construction entrances and exits to keep equipment from tracking mud onto public streets. A stabilized construction entrance is meant to be installed at every point where construction vehicles leave the site, with all other access restricted so traffic cannot bypass the control. The manual pairs the entrance with supporting practices such as street sweeping, which removes any sediment that escapes the entrance before it can wash into storm drains or surface waters. Routine inspection and maintenance are required so the entrance keeps performing throughout the life of the project.

The Aggregate Construction Entrance and Its Limits

The traditional New Hampshire construction entrance is an aggregate tracking pad, built by placing crushed stone over a geotextile filter fabric to create a rough surface that dislodges sediment from tires. The dimensions are chosen for the expected vehicle traffic and site conditions so vehicles get enough tire rotations before reaching the road.

The weakness of the aggregate pad is maintenance. Over time the stone compacts and the voids fill with sediment, which reduces effectiveness, and the pad must be top dressed with fresh aggregate, repaired, or lengthened, often more frequently during New Hampshire's wet seasons and spring thaw. When an aggregate entrance alone cannot control tracking, operators add supplemental controls such as shaker or rumble plates, steel plates, or cattle-guard style systems that shake sediment loose, or a wheel wash that sprays tires with pressurized water. Each of these adds equipment, water handling, or sediment cleanout, and each carries a recurring cost.

FODS as a Compliant Construction Exit in New Hampshire

Neither EPA nor NHDES maintains a brand-name approval list for construction exits. Both evaluate a construction entrance on whether it performs the required function, removing sediment from tires before vehicles reach the road, and the operator specifies the chosen practice in the project SWPPP and the AoT erosion and sediment control plan. Because the standard is performance based, FODS Trackout Control Mats can be named directly in both plans as the site's stabilized construction entrance without a separate approval letter.

FODS satisfies the same purpose the New Hampshire Stormwater Manual assigns to an aggregate pad, while removing the loose rock and the heavy maintenance cycle that the traditional options depend on. For inspectors working under either the CGP or an AoT permit, the result is a construction exit that meets the intent of the guidance, holds up under repeated traffic and freeze-thaw conditions, and does not need to be rebuilt after every storm.

FODS Trackout Control System

The FODS Trackout Control System is a reusable, manufactured construction entrance BMP made of high-density polyethylene mats with pyramid-shaped surface features. As vehicles pass over the mats, the pyramids flex the tires and open the tread lugs so sediment is released and captured in the voids between the pyramids, which reduces re-tracking. The mats install over soil, concrete, or asphalt without excavation and introduce no loose aggregate to the site, so there is no risk of stone being carried onto active roadways.

Maintenance is simple, usually a pass with a power broom, street sweeper, or hand tools to clear accumulated sediment, and contractors can clean the mats during the routine street sweeping the manual already calls for. The system is modular, so entrances can be reconfigured as site conditions change and relocated through the phases of a project. With a service life of ten years or more, the same mats can be reused across multiple projects, which shifts the cost of a construction exit from a recurring expense to a one-time investment. The water-free, all-weather design is well suited to New Hampshire, where winter conditions and spring thaw can quickly degrade a rock pad or freeze a wheel wash.

Risks of Vehicle Trackout on Roadways

Safety is a primary concern wherever construction traffic meets a public road. Aggregate exits deposit rock and debris onto pavement, creating hazards for drivers and workers, and loose stone can lodge between dual tires. Wheel washes add a cold-weather risk, since dripping vehicles can build ice on New Hampshire roadways. FODS uses a rockless, water-free technique to clean tires and does not carry the same risk of injury or liability as aggregate entrances. The mats are durable and reusable across many projects, which reduces the environmental impact tied to aggregate production, hauling, and disposal. On sites that drain to the Merrimack, the Connecticut, Great Bay, or the lakes and streams of the White Mountains, keeping rock and sediment out of the road also helps keep it out of the water.