Gravel, Stone and Soil Delivery in Johnson City, TN

A steep slope of channery silt loam

At the ZIP's center point, the USDA soil survey maps Montevallo channery silt loam, 35 to 50 percent slopes. Montevallo makes up 90 percent of the map unit, so this one soil covers nearly all of it. The word channery means the soil is full of thin, flat fragments of rock, the kind that split off shale.^[1]

The survey rates Montevallo well drained and places it in hydrologic group D, with very slow infiltration and high runoff. That pairing comes from depth. Paralithic bedrock, a soft and weathered rock, lies at about 18 inches. Water moves through the shallow soil but meets the rock fast, then runs downhill.^[1]

Shrink-swell in the top meter rates low, at 0.5 percent. This soil barely heaves at all. A project here has to work with a steep grade, shallow rock and fast runoff.^[1]

Limestone, shale and dolomite below

The geologic map shows a Cambrian unit named Maynardville Limestone, Nolichucky Shale, and Honaker Dolomite at the center point. Its rocks are dolostone, limestone, shale and siltstone. Shale breaks into the flat chips that give the soil its channery name.^[2]

Limestone and dolomite in the same unit weather in a different way from shale. They dissolve slowly in water, and a yard over them can hold small hollows or loose pockets under the soil. A spot that settles after a storm deserves a look before a drive or a pad is built over it. Fill a small hollow with compacted Road Base rather than loose dirt.^[2]

Weathered shale near the surface is soft enough to dig with effort, but it does not make a stable base by itself. Once exposed, it can crumble and slake in rain. A cut bank in shale should be covered, planted or faced with stone so it does not shed chips onto a drive. The ground at the center point stands 1,690 feet above sea level.^[2],[3]

Weather at the Elizabethton gauge

The NOAA normals station at Elizabethton, TN, about 5 miles away, gives the weather averages for this ZIP. It records 48.0 inches of precipitation and 6.0 inches of snow in an average year. On a steep slope with shallow rock, that rain turns into fast runoff, and runoff is the force that cuts ruts into a gravel drive.^[4]

The gauge counts 94 days a year with a low of 32 F or colder. Its median last spring freeze is April 19. Its median first fall freeze is October 24. Wet ground that freezes and thaws loosens stone on a slope, so a drive needs a base that drains and a surface that sheds water fast.^[4]

Switchbacks, culverts and stone that grips

Tennessee's Department of Transportation builds roads over a compacted layer it calls Mineral Aggregate Base, Type A, Section 303 of its Standard Specifications for Road and Bridge Construction (April 1, 2026). A home drive on a hillside uses the same kind of dense, well graded stone.^[5]

On a grade of 35 to 50 percent, a drive straight up the hill is rarely practical. Most hillside drives cut across the slope in one or more turns. Each turn is a place where water wants to leave the drive, so plan a culvert or a stone-lined outlet there. Riprap at the outlet keeps the bank below from eroding.^[1]

Build the drive on firm ground by scraping off the loose top and cutting into the slope. Compact Road Base in thin lifts over the cut. On weathered shale, a layer of fabric under the base keeps chips and silt from mixing in when the ground is wet. A lower course of 1-1/2" Crushed Gravel adds strength on a drive that carries trucks.^[1],[2]

Finish with a thin top of 3/4" Crushed Stone. Angular stone grips tires on a slope, while rounded stone rolls. Water bars set at an angle across the drive turn runoff off the surface every so often, before it can build up speed.^[1],[4]

Crushed stone sizes for a mountain lot

Steep ground asks a lot of every stone size, and each one has a job. #4 Crushed Stone and 1-1/2" Crushed Gravel are the big pieces. They form a strong lower course, bridge soft spots and leave open gaps for water. They are rough to walk on, so they belong under other layers or in ditches.^[1]

#57 Crushed Stone is the middle size. It drains freely, so it fills French drains, the space behind walls and the trench at the foot of a cut bank. #67 Stone is a little smaller and packs a bit tighter, which suits a drive top on a gentle stretch.^[1]

Road Base is the binder. Its mix of stone and fines locks together under a roller, and on a grade that lock keeps the drive from sliding. 3/4" Crushed Stone makes the thin wearing layer on top. #89 Crushed Stone and Walkway Gravel suit paths and steps, where a small, angular stone gives good footing on a slope.^[1]

Riprap is the largest stone and the one that stops erosion. Set it at culvert outlets, along the edge of a creek or at the base of a steep bank where runoff hits hardest. On ground with bedrock at about 18 inches, a ditch cannot go deep, so the stone has to armor a shallow channel.^[1],[4]

Walls, terraces and beds on a hillside

A steep lot gains usable space through terraces. A low retaining wall with a layer of #57 Crushed Stone or Drain Rock behind it lets water drain through, so pressure does not build up. Fill Dirt brings the terrace level, and a layer of Topsoil on top gives plants a root zone.^[1]

With bedrock at about 18 inches, native soil is thin for most plants. Raised beds of Garden Soil, or Topsoil mixed with Compost, give roots the depth they need. Shredded mulch holds well on a slope and slows the runoff that would strip bare soil.^[1]

Spring planting is safest after the median last spring freeze of April 19. Fall planting of shrubs and trees does best a few weeks ahead of October 24, so roots can settle before the cold.^[4]

The Census counts 18,299 housing units in ZIP 37601. Detached single-family houses make up 56 percent, and owners live in 56 percent of the occupied homes. The median home in the ZIP was built in 1981. Johnson City as a whole has 33,360 housing units, with 53 percent detached houses and a median build year of 1983.^[6]