Bulk Gravel, Stone, Soil and Mulch Delivery in Cambridge, MA

Built-over ground with a dense layer below

The USDA survey maps the Newport-Urban land complex, 3 to 15 percent slopes, at the center point of ZIP 02138. Urban land, meaning paved or built over, makes up 40 percent of that map unit, and the Newport series covers 45 percent. The natural top layer is channery fine sandy loam. Channery means the soil carries flat, thin rock fragments, the kind that clink against a shovel blade and make digging slow.^[1]

The survey rates the soil well drained, yet it sits in hydrologic group D, with very slow infiltration and high runoff. The reason is a restrictive layer of densic material at about 24 inches. Densic material is hard-packed earth that roots and water struggle to get through. Water that soaks into the upper soil can stall on top of that layer and spread sideways. The shrink-swell rating for the top 100 cm is low, at 1.5 percent, so movement from wetting and drying is small.^[1]

The upshot for a project is simple: water that gets into the ground here has a shallow layer to work with before it hits the dense material. Plan for drainage near the surface rather than counting on deep soaking. Free-draining stone under hard surfaces, trenches that carry water to the street or to a planted area, and raised beds all fit that pattern. Deep planting holes for trees can fill like a cup unless the dense layer is broken up or the hole is kept wide and shallow.^[1]

Old slate-like rock and low ground

The USGS state geologic map shows the Cambridge Argillite at the center point, a Neoproterozoic unit of argillite, quartzite, sandstone and conglomerate. Argillite is a hard, fine-grained rock formed from compacted mud, a little like slate without the clean splitting. Weathered fragments of rocks like these are a likely source of the flat channery pieces in the soil above.^[2]

The ground at the center point stands 50 feet above sea level. That is a reading for one point on the map. On a small city lot, the slope that counts is usually the one between the house wall and the sidewalk or alley, and getting that slope right matters more than any other number.^[3]

Long freezing season and steady rain

The NOAA normals station at Jamaica Plain, MA, about 5 miles away, averages 49.4 inches of precipitation a year. Rain and melting snow arrive in every season. On ground with a dense layer below and a lot of pavement around it, that water has few places to soak in, so small yards collect runoff from roofs, walks and neighbors' lots.^[4]

The station counts 121 days a year when the low drops to 32 F or colder. Its median last spring freeze is April 19 and its median first fall freeze is October 23. A gravel or paver surface that holds water will be lifted and loosened by that many freezes. Free-draining stone, a firm base and a surface that sheds water are what keep a walk or parking spot level from one spring to the next.^[4]

Winter also brings shoveling and plowing. Stone surfaces close to walks and stoops get scraped by shovels, and loose gravel ends up in lawns and on sidewalks. A firm surface such as compacted Stone Dust Screenings or Decomposed Granite holds up better near entries than loose stone. Where gravel meets a walk, a solid edge of brick, steel or stone keeps the two apart and gives a shovel blade something to ride along.^[4]

A parking pad on a tight lot

Off-street parking is valuable here, and a gravel pad is the simplest way to make it. Dig out the soil and any old fill to firm ground, pulling out the larger channery fragments and debris. Because water stalls on the densic layer, lay a woven geotextile and build with free-draining stone. A base of #4 Crushed Stone or 1-1/2" Crushed Gravel lets water pass through, and a layer of Road Base on top compacts into a firm bed.^[1]

Finish the pad with 3/4" Crushed Stone or Driveway Gravel, which locks under tires and drains fast. Keep the surface slightly lower than nearby walls and give it a gentle fall toward the street or a planted strip, never toward a basement. Where a pad sits beside a house, a narrow trench of Drain Rock along the wall catches roof drip and keeps water away from an old foundation.^[1],[4]

Small gardens, courtyards and tree beds

Many gardens here are raised beds, planters and narrow strips between walks. The native channery soil, with its dense layer at about 24 inches, is hard to dig and slow to drain, so building up is easier than digging down. Fill raised beds with Garden Soil or a blend of Topsoil and Compost. A bed that sits above the ground drains on its own and warms faster in spring after the April 19 median last freeze.^[1],[4]

Courtyards and side passages suit Pea Gravel or 3/8" Crushed Stone, which drain quickly, feel good underfoot and come up easily if a pipe needs work. Black Shredded Mulch or Brown Shredded Mulch dresses tree beds and shady strips, holding moisture and keeping weeds down. Under a brick or paver path, a compacted layer of Road Base topped with a thin bed of Concrete Sand keeps the bricks level through many freezes.^[1],[4]

Tree pits along walks often hold compacted fill that roots can barely enter. Loosen the top few inches, work in Compost and Topsoil, and cover the pit with a thin layer of Brown Shredded Mulch kept back from the trunk. Avoid piling soil against the trunk itself. A small amount of good soil and steady mulch does more for a street tree than a deep load of fill.^[1]

Old homes and dense housing in ZIP 02138

The Census counts 16,043 housing units in ZIP 02138. Cambridge as a whole has 54,840. Detached single-family houses make up only 14 percent of the ZIP's homes, a little above the 10 percent share for the city. By the Census median, half of the homes in the ZIP date from 1939 or earlier, and the city median year built is 1950. Owners occupy 42 percent of the occupied homes in the ZIP.^[5]

Old buildings and shared lots shape the work here. Most jobs are small: a single parking pad, a rebuilt walk or a few yards of soil for raised beds. Access can be tight. Plan where the load will land before it arrives, protect the sidewalk with plywood or a tarp, and keep the pile clear of drains. A smaller, well-placed delivery makes a narrow site far easier to work.^[5]