Driveways and parking lots in Buffalo, built from the stone base up

Lake-plain silt, frost and the base that has to beat them

The northern half of Erie County, Buffalo included, sits on what the county's USDA soil survey calls the Erie-Ontario lake plain: the flat floor of old glacial lakes. Niagara silt loam is one of the more common soils those lakes left behind. The survey describes it as deep and somewhat poorly drained, says water stands high in its subsoil each year from December to May, and names seasonal wetness and low soil strength among its limits.

Silt is also the soil most prone to frost heave. It wicks moisture up toward the freezing line, that moisture turns into lenses of ice, and the ground lifts. When those lenses melt in late winter and spring, the silt turns soft, and a thin layer of stone on top gets pushed down into it. Put simply, the ground under a driveway is often at its wettest right when the frost comes out. That cycle is behind the ruts, the soft spot by the garage and the potholes that come back every spring.

So the fix happens below the surface. We dig out the topsoil and any soft or organic material until we reach firm subgrade, shape that subgrade so water drains off it, and roll out geotextile fabric wherever wet silt or clay would otherwise swallow the stone. Then the base goes in, compacted in lifts rather than dumped full depth and rolled once. How deep it goes depends on what the excavator uncovers and what's going to drive on it.

Limestone, crushed concrete, millings or gravel on top?

The base and the surface do different jobs, so the stone for each should be chosen on purpose. Angular crushed stone locks together under a compactor; rounded stone rolls under a tire. Here's how the common options behave on a Western New York drive or lot:

• Crushed limestone. Angular and consistent. Coarse sizes build the base, and a finer grade with its dust left in packs into a tight top that sheds water.
• Crushed concrete. Old concrete crushed and screened to size. It compacts hard and makes a solid base, but a load can carry chunks of brick or bits of rebar, so it gets a look before it's spread.
• Asphalt millings. Ground-up old blacktop. Rolled in warm weather they knit into a darker, firmer surface than loose stone, but they're a topping, not a replacement for base.
• Rounded gravel. Drains freely, which makes it useful in drain trenches, but as a driving surface it ruts and scatters where tires turn.
• Blacktop. Laid by a paving company over the base we build and fine-grade. Asphalt only lasts as long as the stone under it stays dry and firm.

Whatever goes on top needs a crown or a cross-slope. A dead-flat stone surface holds puddles, and puddles turn into potholes.

Inside Buffalo city limits: curb cuts and surface rules

A driveway in the city answers to the Buffalo Green Code, and a few of its rules catch people off guard. Any new cut in the curb to reach your property needs a curb cut permit, and the code says curb cuts should sit at least 60 feet from an intersection unless the Commissioner of Public Works, Parks, and Streets allows otherwise. The number and width of cuts are held to the minimum needed for reasonable access.

Surface matters as well. Driveways, parking stalls and drive aisles have to be surfaced with a fixed, firm, non-slip material, and gravel is allowed only with written consent from the Commissioner of Permit and Inspection Services. The piece of driveway inside the public right-of-way must be built to Public Works specifications. So inside the city, a new drive usually means a stone base fine-graded for a paver rather than loose stone left as the finished surface.

For a house in the N-2R, N-3R, N-4-30 or N-4-50 zones, the code allows one driveway, and it must be single-lane. Parking in front of a detached or attached house isn't allowed; the code puts it in a driveway in the side or rear yard. Two-track driveways are allowed when each strip is at least 18 inches wide with living groundcover between, though the stretch in the right-of-way still has to be paved full width from property line to curb. Confirm your zone and the current rules with the City's Permit and Inspection Services office before planning a second driveway, and see our Buffalo excavation page for other work we do in the city.

Road ditches and culverts: the road's owner sets the rules

Out in the towns, plenty of driveways cross an open roadside ditch instead of a curb, and that crossing is where the paperwork lives. Who issues the permit depends on who owns the road. Erie County's highway work permit covers the roads, bridges and culverts under county jurisdiction, and the form itself notes that the state and local governments permit their own. On an Erie County road the permit office wants a week's notice before work begins, and work has to start within 30 days of the permit date.

On a state highway, NYSDOT's entrance standards call for a culvert no smaller than 15 inches inside diameter (12 inches only in extreme conditions, with the Department's approval), tapered or flared end sections instead of headwalls in the clear zone, and at least 12 inches of cover over the pipe. The low point of the driveway belongs at or near the pipe's centerline so road runoff drops into the ditch, and the new entrance can never send water across the pavement or leave it ponding on the shoulder or in the ditch. Afterward, the property owner maintains the driveway out to the edge of the shoulder, pipe included.

Towns can add steps of their own. In Clarence, for example, the building permit checklist for a new home requires a driveway culvert sign-off from whichever highway department controls the road: town, county or state. The applicant buys the pipe, only that department installs it, and culvert and stone have to be in place before any site work starts. We build the drive to fit whatever pipe goes in, so call the highway department for your road early.

Parking lots and private roads: where does the water go?

A parking lot is a big, hard, nearly flat roof lying on the ground, and every drop that lands on it has to go somewhere. Grading a lot means setting the pitch so water runs to catch basins, swales or a ditch instead of sheeting across the entrance or freezing into a rink by the door. We excavate, build the base, grade it and set the catch basins and storm lines before a paving crew ever arrives.

In Buffalo, the Green Code caps surface parking slope at 10%, requires lots to drain into a city sewer or stormwater facility to Buffalo Sewer Authority specifications, and holds lots to the federal ADA standards for accessible parking. For a commercial entrance onto a state highway, NYSDOT skips the drainage study only for small jobs (2,000 square feet or less of new impervious pavement draining to its system, within the limits in its drainage figures); larger ones need a study signed by a New York State Professional Engineer.

Size changes the paperwork too. Clear, dig or grade an acre or more of ground and the owner or operator must be covered by NYS DEC's SPDES general permit for construction stormwater before the work begins, which means writing a Stormwater Pollution Prevention Plan and filing an electronic Notice of Intent. A private road or subdivision street is built like a long, narrow lot: crowned stone base, ditches or swales along the edges, and a culvert at every crossing, often as one piece of larger site development.