Rock, Gravel and Soil Delivery in Chandler, AZ

Sandy loam over old desert gravels

The USDA soil survey maps the ZIP's center point as Mohall sandy loam, and the Mohall series makes up 100 percent of that map unit. Sandy loam is a mix with enough sand to feel gritty between the fingers and enough silt and clay to hold a shape when it is damp. It packs well under a compacted stone layer, and it is easy to dig with a flat spade when you cut an edge for a new bed or a parking strip.^[1]

The survey rates the Mohall soil as well drained, yet it places it in hydrologic soil group C, the group for soils where water soaks in slowly. Those two ratings fit together. Water does not sit in the profile for long once it gets in, but a hard burst of rain can arrive faster than the surface can take it. Plan every flat surface with a slight fall so storm water runs to a planting area or a rock swale instead of pooling against a slab.^[1]

Shrink-swell in the top 100 cm at that point is rated moderate, at 4.5 percent. Soil with a moderate rating grows a little when it gets wet and pulls back as it dries. A compacted base of Road Base spreads the load of a car and evens out small movements, so a stone surface stays flatter than loose fill laid straight on the dirt.^[1]

Below the soil, the USGS geologic map places the center point on Late and middle Pleistocene surficial deposits, a unit made of gravel, sand, silt and clay from the Middle Pleistocene. Old desert deposits like these were spread by water running off the mountains, so a deep hole can turn up rounded cobbles mixed with finer layers. The ground at the center point stands 1,200 feet above sea level.^[2]

Dry years and the odd cloudburst

Weather figures for this area come from the NOAA normals station at Tempe Asu, AZ, about 7 miles away, which averages 8.8 inches of precipitation in a year. A total that low means most days are dry, and dust and wind do more to a stone surface than rain does. Angular stone such as 3/4" Crushed Stone or Decomposed Granite locks into place and resists being scuffed loose by tires or blown around by gusts.^[3]

Average yearly snowfall at Tempe Asu is 0.0 inches. The station logs 10 days a year when the overnight low falls to 32 F or below. A few cold nights do little harm to a gravel drive, but they matter for tender plants and for drip lines left full of water near the surface.^[3]

At that station the median last spring freeze falls on February 13. The median first fall freeze comes on December 5. Planting new shrubs and topping beds with fresh mulch works best in the long mild stretch between those two marks, before the summer heat sets in.^[3]

Desert storms can drop much of a season's rain in an hour or two. On a slow-infiltration soil, that water runs across the surface and carries fine material with it. A shallow swale lined with River Rock or Riprap gives the runoff a channel that will not wash out, and a band of Drain Rock along a wall keeps splashback off the stucco.^[1],[3]

Building a parking pad on this ground

Say you want a side pad for a trailer or a second car. Start by scraping off the loose top layer and any roots until you reach firm sandy loam. Wet the subgrade lightly and run a plate compactor over it, because a dry sandy loam can sound firm and still shift under weight.^[1]

Spread Road Base or 1-1/2" Crushed Gravel in lifts of a few inches, wetting and compacting each lift before the next one goes down. The fines in Road Base bind the larger pieces into a dense mat, which matters on a soil that sheds hard rain. Give the finished surface a gentle crown or a slight fall toward the street so water leaves the pad quickly.^[1]

For the top layer, many owners choose Decomposed Granite for the desert look or Driveway Gravel for a cleaner stone finish. Decomposed Granite packs into a firm, walkable surface that matches the tan ground around it. Driveway Gravel gives better grip after a rare rain and is easier to rake back into place after a tire leaves a rut. Metal or concrete edging along both sides keeps either surface from creeping into the yard.^[1]

Rock yards, beds and shade trees

Many desert yards trade lawn for stone cover, and the choice of rock shapes how the yard looks and how it handles heat. Decomposed Granite makes a soft-toned, firm path between beds. River Rock in a dry creek bed looks natural and moves storm water along. #57 Crushed Stone works under a gravel patio where you want the water to drop straight through.^[1],[3]

Mohall sandy loam drains well, but desert soils hold little organic matter. When you start a new bed for roses, citrus or vegetables, blend Compost into the top layer or fill a raised bed with Garden Soil. Topsoil works for leveling low spots in a yard before you lay new rock or sod.^[1]

Mulch helps roots through both the summer sun and the handful of cold nights. Brown Shredded Mulch and Wood Chips shade the soil, slow evaporation and break down over time into the organic matter these soils lack. Keep mulch a few inches back from tree trunks and away from the house wall.^[3]

Paver patios do well on this ground when the base is right. Compact a layer of Road Base or Crushed Concrete, screed a thin bed of Concrete Sand, set the pavers, and sweep Stone Dust Screenings into the joints. The moderate shrink-swell rating means a thin base can show small dips over the years, so lean toward a thicker compacted layer under spots that carry a grill or a heavy planter.^[1]

Homes in ZIP 85224 and across Chandler

The Census counts 21,530 housing units in ZIP 85224. Detached single-family houses make up 58 percent of them, with apartments, condos and townhomes filling out the rest.^[4]

For comparison, Chandler as a whole holds 112,800 housing units, and 68 percent of those are detached houses.^[4]

The median home in ZIP 85224 was built in 1989. Across the whole city the median build year is 1997, so the housing in this ZIP runs a little older than the city norm.^[4]

Owners live in 54 percent of the occupied homes in ZIP 85224. Owners and renters alike order stone for small jobs, such as a fresh layer of rock in a side yard or a new path to a back gate.^[4]