Stabilized Construction Entrance: Size, Stone and Tons

The short answer

A stabilized construction entrance is a temporary pad of large, clean, angular stone laid over geotextile fabric where trucks and equipment leave a job site. As tires roll across the rock, the stone flexes the tread and knocks off mud, so less of the site ends up on the public street and in the storm drains. Most erosion control permits require one wherever construction traffic exits onto a road.

There is no single national size. Typical agency details call for a pad at least 50 feet long (100 feet in Washington), 10 to 20 feet wide or the full width of the opening, and 6 to 12 inches of stone in the 1½ to 3½ inch range, or 4 to 8 inch quarry spalls in Washington. For a common 50 by 20 foot pad that is roughly 25 to 50 tons of stone, depending on depth. The rest of this guide shows where those numbers come from and how to work out your own order.

Why sites need one

Bare dirt sticks to tires, especially clay after a rain. Every truck that drives straight from the mud onto the pavement leaves a trail of clods that later washes into the gutter, the catch basins and eventually a creek. The U.S. EPA's fact sheet on construction track-out controls says a stabilized entrance is generally a requirement of any construction permit, and it is often the first thing an inspector or a neighbor sees.

The rock pad does two jobs. The coarse stone shakes and scrapes soil off the tires, and the voids between the stones give that soil somewhere to go so it does not just get carried along. The fabric underneath keeps the stone from being pushed down into soft ground and stops mud from pumping up into the rock. If you are building a permanent driveway later, the same idea applies; see our guide to geotextile fabric for driveways.

Do not expect a rock pad to catch everything. EPA puts sediment removal for gravel pads and shaker racks anywhere from under 30 percent up to 60 percent, while a properly installed wheel washing rack can remove 75 percent or more. Pennsylvania rates a plain rock construction entrance as low efficiency and a rock entrance with a wash rack as high efficiency. The pad is the minimum, not the whole plan.

Stabilized construction entrance dimensions by agency

Here is how several published standards size the pad. Your local permit or plan sheet wins over any of these, so check it first.

Standard	Minimum length	Width	Stone	Depth
Pennsylvania DEP, Standard Construction Detail #3-1 (rock construction entrance)	50 ft	20 ft min.	AASHTO No. 1	8 in
Wisconsin DNR Technical Standard 1057 (stone tracking pad)	50 ft	Full access width, or a 12 ft min. exit lane	3 in max., 25–60% passing 1½ in	12 in
Washington BMP C105 (Ecology manual, adopted by cities such as Bellevue and Tacoma)	100 ft (shorter where the site can't fit it)	15 ft min.	4–8 in quarry spalls	12 in
Michigan EGLE access road guide sheet	50 ft	10 ft min., and at least 2 ft wider than the largest vehicle	2–3 in open-graded or washed angular stone	6 in suggested min.
MDOT construction manual (gravel access approach)	50 ft	Wide enough for all site traffic	3x1 aggregate or approved material	6 in min.
U.S. EPA track-out fact sheet (general guidance)	Long enough for the largest vehicle	Room for two vehicles to pass if traffic is heavy	Large enough not to be carried off site	6 in min.

A few details are worth pulling out of those documents:

Flare the end. EPA and Michigan EGLE both say to widen the pad where it meets the road so long trucks don't cut the corner onto bare dirt as they turn.
One way out. Washington's BMP, as Tacoma adopts it, limits construction traffic to one route where possible, Pennsylvania wants site access limited to the stabilized entrance, and Wisconsin wants every exiting vehicle to cross the full length of the pad. A perfect pad does nothing if drivers go around it.
Ditches need a pipe. If the entrance crosses a roadside ditch or swale, EPA and Pennsylvania call for a culvert or bridge so the water keeps moving. Pennsylvania adds a mountable berm over the pipe where it would otherwise lack enough cover. Our driveway culvert guide covers pipe sizing and permits.
Strip it first. Pennsylvania's detail says to remove the topsoil before placing the fabric and stone.

Construction entrance stone size

The stone has to be big enough that it does not stick in tread and ride off the site, and open enough that there is room between stones for mud. That is why these specs use coarse, single-size rock instead of a dense base like crusher run or 21AA, which packs into a smooth surface and stops cleaning tires.

AASHTO No. 1, the stone in Pennsylvania's detail, is defined in AASHTO M 43 as nominal 3½ to 1½ inch: 90 to 100 percent passes a 3½ inch sieve, 25 to 60 percent passes 2½ inch, and no more than 15 percent passes 1½ inch. Wisconsin's gradation is a little smaller: everything passes 3 inches and only 0 to 20 percent passes ¾ inch. Michigan's guide sheet asks for 2 to 3 inch stone and says angular, crushed rock removes more sediment and lasts longer because the fractured faces leave more pore space.

Bigger is not always better. Washington Ecology notes that WSDOT raised a safety concern about 4 to 8 inch spalls getting stuck between dual truck tires and then flying out at highway speed, and Michigan EGLE warns against sizes that wedge between duals. Wisconsin tells crews to remove stones lodged between dual tires before the truck leaves. EPA also says to avoid sharp-edged stone that can cut tires.

On recycled material, the standards disagree. Wisconsin and Michigan allow recycled or crushed concrete, while Washington prohibits crushed concrete, cement and calcium chloride for this use because they raise the pH of stormwater. If you were planning to use broken concrete from a tear-out, check your state's rule first. Our post on a crushed concrete driveway explains the material itself.

Fabric under the stone

Every standard in the table puts a geotextile under the rock, though Wisconsin only requires one where the soil type or high groundwater calls for it. Michigan EGLE specifies a nonwoven fabric of 8 to 12 ounces per square yard, and EPA also calls for nonwoven geotextile on the graded soil. Washington lists minimum properties instead: 200 psi grab tensile strength, 30 percent maximum elongation, 400 psi Mullen burst strength and an apparent opening size of 20 to 45 (U.S. standard sieve). A Pennsylvania conservation district specification (Wayne County) calls for PennDOT Class 1 geotextile, pinned in place before the stone goes on.

For a small job, a roll of 8 oz nonwoven geotextile fabric and a box of heavy-duty 6-inch landscape staples to hold it flat while you dump the first loads is usually enough. On a permitted commercial site, buy the fabric the plan names.

Worked example: how many tons of stone?

The math is the same as any stone order: length × width × depth in feet gives cubic feet, divide by 27 for cubic yards, then multiply by the stone's weight. We use 1.4 tons per cubic yard below because it is a common planning figure for crushed stone. Large open-graded rock can weigh a bit less per yard than a dense base, so ask your quarry for the weight of the exact product.

Pad (length × width × depth)	Based on	Cubic yards	Tons at 1.4 t/yd³	Fabric
50 ft × 10 ft × 6 in	Michigan EGLE minimum	9.3	13.0	500 sq ft (56 sq yd)
50 ft × 20 ft × 6 in	MDOT-style approach, 20 ft opening	18.5	25.9	1,000 sq ft (111 sq yd)
50 ft × 12 ft × 12 in	Wisconsin minimum exit lane	22.2	31.1	600 sq ft (67 sq yd)
50 ft × 20 ft × 8 in	Pennsylvania detail #3-1	24.7	34.6	1,000 sq ft (111 sq yd)
100 ft × 15 ft × 12 in	Washington BMP C105	55.6	77.8	1,500 sq ft (167 sq yd)

Take the Pennsylvania row as an example: 50 × 20 × 0.667 ft = 667 cubic feet. Divide by 27 to get 24.7 cubic yards, and at 1.4 tons per yard that is about 34.6 tons. Add fabric overlap at the seams, and keep extra stone on hand. Pennsylvania's detail says to keep a stockpile on site for topping up, and in its program manual notes that on some sites the pad needs fresh rock several times a day. You can run any size through our crushed stone calculator and change the weight per yard to match your supplier's number.

Installing it, step by step

Build it before you dig. EPA says to stabilize every entrance and exit before land disturbance starts, so the very first trucks cross rock, not mud.
Lay it out. Mark the length, width and flare. Size it for the biggest truck you expect, with room to turn.
Strip and grade. Remove topsoil and vegetation, then shape the subgrade so water drains off the pad toward a sediment trap or other control, not toward the street. Michigan EGLE notes that a firm, compacted subgrade makes the pad work better and cuts maintenance.
Roll out fabric. Cover the whole footprint, overlap the seams and pin it.
Place the stone. Dump from the road end and push the rock out ahead of the truck so the tires ride on stone, not on bare fabric. Spread it to full depth over the full width.
Leave the surface rough. Here the specs disagree. Wisconsin says not to compact the stone before use, because a smooth surface stops working, while Michigan EGLE calls for placing and compacting the aggregate in layers 3 to 6 inches thick. Follow your permit.

Maintenance and what to do about mud on the road

A rock pad fills with mud and stops working, usually sooner than people expect. Wisconsin notes that stone tracking pads in particular need extra maintenance during and right after heavy hauling, and says to keep the surface loose and rough by scraping, loosening or top-dressing with fresh stone, and to replace the fabric and rock if that fails. Pennsylvania says to extend the pad in 50-foot increments or add a wash rack if trucks keep tracking mud onto the road.

When soil does reach the pavement, the rule is to sweep it up and bring it back on site. Pennsylvania and EPA both say not to wash it or sweep it into ditches, sewers or storm drain inlets. A stiff 24-inch push broom and a square-point shovel handle small spills; a big site will need a sweeper truck after wet days. Once the site is stable, the pad can often be pulled up, or graded out and used as the base for a permanent drive. If you are heading toward a gravel or paved drive, our guide on fixing a muddy driveway covers long-term options.

Stabilized construction entrance FAQ

What is a stabilized construction entrance?

It is a temporary pad of coarse, angular stone over geotextile fabric where vehicles leave a construction site. The rock knocks mud off tires so less soil is tracked onto public roads and into storm drains.

How long and wide should a construction entrance be?

Most published details call for at least 50 feet long. Pennsylvania uses 20 feet wide, Wisconsin the full access width or a 12-foot exit lane, Michigan EGLE at least 10 feet and 2 feet wider than the largest vehicle. Washington calls for 100 feet long and 15 feet wide. Your permit's detail governs.

What size stone is used for a construction entrance?

Coarse, clean, angular rock. Pennsylvania specifies AASHTO No. 1 (nominal 3 1/2 to 1 1/2 inch), Michigan EGLE 2 to 3 inch stone, Wisconsin a gradation topping out at 3 inches, and Washington 4 to 8 inch quarry spalls. Dense base like crusher run fills in and stops cleaning tires.

How many tons of stone does a construction entrance need?

Multiply length, width and depth in feet, divide by 27 for cubic yards, then multiply by the stone weight. A 50 by 20 foot pad 8 inches deep is about 24.7 cubic yards, or about 34.6 tons at a planning weight of 1.4 tons per cubic yard.

Do you need fabric under a construction entrance?

Nearly every standard calls for it. EPA and Michigan EGLE specify nonwoven geotextile, Michigan at 8 to 12 ounces per square yard. Wisconsin requires it where soil type or high groundwater warrants. It keeps stone from sinking into the mud and mud from pumping up into the stone.

The bottom line

A stabilized construction entrance is a simple thing: a fabric-lined pad of coarse, clean, angular stone where trucks leave the site. Most published details land on about 50 feet long, as wide as the opening, and 6 to 12 inches of 1½ to 3½ inch rock, though Washington goes bigger. Figure the cubic yards, multiply by your supplier's weight per yard, order a little extra for top-ups, and keep the pad rough and clean. Above all, read your permit, because the local detail is the one the inspector will check.

Sources checked for this article

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