Crushed Stone, Gravel and Soil Delivery in Fayetteville, AR

Steep Enders soil with stones and swelling clay

The USDA soil survey maps the Enders-Leesburg complex, 20 to 40 percent slopes, at the ZIP's center point, and the Enders series makes up 50 percent of that map unit. Slopes in that range are steep enough that water, soil and loose gravel all head downhill fast whenever it rains.^[1]

The top mineral layer is stony loam, so a shovel will strike rock often. Deeper down, the survey rates shrink-swell in the top 100 cm as high, at 7.5 percent linear extensibility. That means clay layers under the stony surface swell hard when soaked and shrink back as they dry, enough to crack walls, tilt steps and shift a slab.^[1]

The Enders soil is rated well drained, yet it sits in hydrologic group D, with very slow infiltration and high runoff. The survey also lists paralithic bedrock at about 54 inches, a soft rock layer that roots and water pass through slowly. Put those together and you get ground where rain runs off the surface rather than soaking in, which is the main thing every project here has to manage.^[1]

Limestone, shale and sandstone below

The state geologic map shows a stack of Mississippian rock under the center point: Pitkin Limestone, Fayetteville Shale (including the Wedington Sandstone member), and Batesville Sandstone (including the Hindsville Limestone Member). Together they are made of sandstone, shale and limestone, laid down in layers when shallow seas covered the region.^[2]

Those layers explain the stony loam on top. Sandstone and limestone break into the stones a shovel hits, and shale weathers into the clay that swells below. When digging a trench or a footing, expect to pass through soft shale and hard rock in a short distance, and allow extra time for breaking through ledges.^[1],[2]

The ground at the survey point stands 1,540 feet above sea level.^[3]

That height belongs to one mapped point on a steep hillside, so neighboring yards can sit noticeably higher or lower. What matters for a project is the fall across your own lot, which on a 20 to 40 percent slope can be dramatic over a short distance. Measure it with a string line before ordering, since a steep run needs more base and more drainage stone than a flat one of the same size.^[1],[3]

Rain, snow and freeze at Drake Field

Weather normals come from the NOAA station at Fayetteville Drake FLD, AR, about 6 miles away. It averages 47.0 inches of precipitation and 6.5 inches of snow a year. On steep group D ground, a heavy storm becomes fast surface runoff in minutes.^[4]

The Drake Field station counts 94 days a year when the low drops to 32 F or colder. Wet clay that freezes overnight and thaws by afternoon heaves and loosens the ground, so a base on this soil has to stay as dry as possible.^[4]

The median last spring freeze at the station is April 15, and the median first fall freeze is October 21. Plant tender crops after mid April, and plan base work for dry spells within that window.^[4]

A hillside drive that stays in place

On 20 to 40 percent slopes, a gravel drive has two enemies: runoff that cuts ruts down its length and swelling clay that softens the base. Start by cutting the drive into the slope with a cross slope toward the uphill ditch. A ditch or a Drain Rock trench on the uphill side catches water before it crosses the drive, and culverts or rock-lined dips carry it under or across at intervals.^[1],[4]

Lay woven fabric on the subgrade, then build compacted Road Base in thin lifts. On high shrink-swell clay, the fabric keeps clay from mixing into the stone each time the ground swells. Where the drive crosses a wet spot, add a layer of #4 Crushed Stone or 1-1/2" Crushed Gravel under the Road Base for drainage and strength.^[1]

For the top, Asphalt Millings hold best on a steep grade, since they bind into a firm crust. 3/4" Crushed Stone and Driveway Gravel work on gentler sections. Build water bars, low humps of compacted base set at an angle, every so often on the steepest stretch to turn runoff off the drive.^[1]

Slopes, beds and erosion control

With very slow infiltration and high runoff, bare soil on a slope here washes away quickly in heavy rain. Cover it. Shredded mulch knits together and stays put better than loose chips, so Brown Shredded Mulch or Black Shredded Mulch is the better choice on slopes. At the foot of a slope, a band of Riprap slows water and catches soil before it reaches a drive or patio.^[1],[4]

Stony loam over clay makes digging beds slow work. Raised beds filled with Garden Soil skip the rock entirely, and terraced beds held with stone turn a steep yard into flat planting steps. In the ground, blend Compost and Topsoil into the top layer to loosen the clay.^[1]

Along foundations, a strip of River Rock or #57 Crushed Stone over fabric keeps water from soaking in right next to the wall, where swelling clay can do the most damage.^[1]

Riprap or River Rock for a hillside channel

On group D ground, the runoff from a big storm needs a defined path down the slope, or it cuts its own. Owners tend to pick between Riprap and River Rock to line that channel. Riprap is large, angular stone that locks together and stays put even when water rushes over it, which makes it the right choice for the steep upper sections and for outlets where a ditch or culvert empties onto bare ground.^[1],[4]

River Rock is smaller and rounded, so it looks like a natural creek and works well in gentler stretches and in the visible parts of a yard. On slopes of 20 to 40 percent, though, rounded stone can roll and wash away in a hard rain. A good plan is fabric along the full channel, Drain Rock as a bedding layer, Riprap where the grade is steepest or the water turns, and River Rock on the flatter runs near the house. With 47.0 inches of yearly precipitation at Drake Field, the channel will carry water often, so build it wide enough to handle a heavy storm.^[1]

Housing in ZIP 72701 and the ArDOT base spec

The Census counts 20,729 housing units in ZIP 72701. Detached single-family houses make up 51 percent of them, and owners live in 43 percent of the occupied homes.^[5]

Fayetteville as a whole holds 45,303 housing units, and 50 percent are detached houses. The median home dates from 1993 in the ZIP and 1997 across the city. With a mix of houses and rentals, orders range from a few yards of mulch for a slope to a full truck of base for a hillside drive.^[5]

The Arkansas Department of Transportation specifies Aggregate Base Course, Class 7, under Section 303 of its Standard Specifications for Highway Construction (2014). That section covers the compacted stone layer under state roads.^[6]