Gravel Delivery in Idaho

The rock maps for our three Idaho cities differ from each other. At Meridian's center point the state geologic map shows gravel, sand and silt, the kind of loose deposit a large river leaves behind. Nampa's center point reads basalt, a dark volcanic rock that cooled from lava. Boise's center point shows mixed clastic rock with basalt and rhyolite, which means broken and cemented sediment alongside two kinds of volcanic stone.^[1]

Those rocks behave differently once crushed. Basalt is hard and heavy, and crushed basalt makes a dark, sharp stone that packs into a tough base. Rhyolite is lighter in color and also hard. River gravel, like the deposit mapped at Meridian's center point, is round to begin with, so it has to be crushed to give it the angular faces a driveway base needs. Washed and screened without crushing, it becomes River Rock and Pea Gravel.^[1]

Soil at the surface is mostly loamy. The USDA survey reads silt loam at Meridian's center point, classed well drained. Nampa's center point shows loam, rated moderately well drained, and Boise's shows loam that is well drained. Silt loam packs firm when dry but gets slick and soft when wet, so fabric under a base helps on ground like Meridian's. Loam is easier: it compacts well and lets rain soak in at a steady pace.^[2]

Ground height runs high across the group. Boise's center point stands 3,500 feet above sea level, the highest of the three. Meridian's reads 2,710 feet and Nampa's 2,450 feet. Each figure is a single spot, and hillside lots on the edge of a city can sit well above the center point while lots in low ground sit below it.^[3]

For a buyer, this means a wide choice of hard stone. #57 Crushed Stone and 3/4" Crushed Stone do most of the work in drives and drains. #89 Crushed Stone and 3/8" Crushed Stone suit paths and paver beds. Road Base and Driveway Gravel blend crushed stone with fines that set up hard. Decomposed Granite and Walkway Gravel give a natural, packed surface that fits a dry, open landscape.^[1]

Dry weather makes most of the year easy for deliveries. The weather station used for Meridian averages 11.5 inches of precipitation a year and the one for Nampa 11.0 inches. Boise's station reads 18.0 inches. With so little rain, the ground is firm most days, and a truck can usually reach a drop spot on hard soil without rutting it. Dust is the bigger nuisance, so wet down a fine pile like Stone Dust Screenings if wind picks up.^[4]

Cold nights are common. The station for Nampa logs 132 days a year at 32 F or colder, Boise's 125 and Meridian's 108. Snow varies widely: Boise's station averages 57.4 inches a year, Meridian's 17.6 inches and Nampa's 9.7 inches. A winter load needs a cleared drop spot and a clear path in. Frozen soil and sand clump and cannot be spread or compacted well until they thaw.^[4]

Spring is when ground gets soft. Melting snow and thawing frost leave the top of the soil wet, and silt loam like the survey shows at Meridian's center point can turn to mud for a while. A paved drive or a firm gravel pad is the safest drop spot then. If the load has to go on a lawn, lay plywood or a tarp first and keep the truck off the softest ground.^[2]

Plan the route before the truck comes. Low limbs, overhead lines, mailboxes, irrigation boxes and narrow gates can all block a truck. A raised dump bed needs open space above it. On hillside lots, a steep drive may be too much for a loaded truck, and the driver may tip at a flat spot near the street instead. Tell us about slopes, soft lanes and tight turns when you order.^[3]

Choose where the pile sits with the next step in mind. A load of stone is heavy to move by wheelbarrow, so drop it as close to the work as the ground allows. On the basalt mapped at Nampa's center point, rock can lie close under the soil, so dig a test hole before you plan a deep drain or a sunken patio near the drop spot. Keep piles off sprinkler heads and valve boxes, which crack under a heavy load.^[1]

Gravel driveways are a common order, and the cold nights set the build. With 132 days at 32 F or colder at the Nampa station, any water held in a base can freeze and lift it. Grade the loam, compact it, and lay a thick layer of Road Base in lifts, then top it with #57 Crushed Stone or Driveway Gravel. Crown the surface and give melt water a path to the edge.^[4]

Water-wise yards are a natural fit for a place this dry. With 11.0 inches of yearly precipitation at the station used for Nampa, many owners replace thirsty lawn with stone. River Rock, Pea Gravel and Decomposed Granite cover open ground and need no watering. Lay fabric under them to keep weeds down, edge the beds with steel or stone, and set drip lines before the stone goes on.^[4]

Garden beds still need good soil. Loam is a fine start, and Garden Soil or Compost mixed into the top helps it hold water through dry summers. Cover the bed with Brown Shredded Mulch, Black Shredded Mulch or Red Mulch to slow evaporation. Topsoil finishes a graded yard before seed or sod, and Fill Dirt builds up low areas first. On the well drained loam at Boise's center point, beds dry out quickly without a mulch cover.^[2]

Snow and runoff still call for drainage now and then. Boise's station averages 57.4 inches of snow a year, and that melt runs toward foundations and low spots. A French drain filled with Drain Rock or #57 Crushed Stone and wrapped in fabric gives it a path away. A dry well of the same stone takes the flow from a downspout. Riprap holds a ditch bank or the outlet of a culvert in place.^[4]

Patios, paths and play areas use the finer materials. Pavers sit on compacted Road Base with a thin bed of Concrete Sand or Stone Dust Screenings. Walkway Gravel and Decomposed Granite pack into firm paths. Wood Chips make a soft cover under swings and trees, and Playground Sand fills a sandbox. Larger acreage jobs use Crushed Concrete, Asphalt Millings, #4 Crushed Stone or Railroad Ballast for lanes and equipment pads.^[2]