Commercial Drainage in Lancaster, PA

Commercial drainage is the set of pipes, inlets, channels and grading that carries stormwater off a business property. It is for owners, HOA boards and property managers who have ponding in a lot, washed-out common areas or runoff that crosses a walkway or a neighbour's line. The aim is simple: water leaves the site on a planned path instead of sitting on pavement and against buildings.

Where commercial properties collect water

Most commercial drainage complaints start in the same few places. A parking lot has a low spot where the pavement settled. A loading dock sits below the grade of the lot behind it. A common area has a slope that sends water toward a building instead of away. A downspout discharges onto asphalt and runs across a drive aisle.

Large paved areas shed water fast, and all of it has to go somewhere. Lancaster receives about 42 inches of precipitation a year, and September is the wettest month. A lot that looks fine in a dry week can hold a shallow lake after one long storm.

• Ponding in parking stalls and drive aisles
• Water running toward a building entrance or dock
• Eroded slopes and washed-out mulch beds in common areas
• Icy patches in winter where meltwater refreezes at the same spot
• Standing water beside a retaining wall or curb

Catch basins and storm inlets for parking lots

A catch basin is a box set into the pavement with a grate on top. Water enters through the grate, drops into the box and leaves through a pipe to a storm line, a swale or an approved outfall. The box has a sump below the outlet so sand and leaves settle out instead of filling the pipe.

Placement matters more than size. A basin goes at the low point and at spots where flow concentrates, such as the end of a long slope or the corner of an aisle. Grates must be rated for the traffic over them, so a delivery lane needs a heavier frame than a pedestrian walkway. Our catch basin installation page covers the basin itself in more detail.

Basins need cleaning. Leaves, mulch and trash block the grate, and sediment builds in the sump. A basin that is never cleaned will flood the lot it was meant to protect.

Trench drains across entrances, docks and walkways

Where water crosses a wide hard surface, a point inlet is not enough. A trench drain is a long, narrow channel with a grate flush to the pavement. It catches sheet flow across the full width of a door, a ramp, a dock apron or a driveway apron before it reaches a building.

The channel body is usually precast polymer concrete or heavy plastic, set in a concrete haunch so it does not shift under wheels. The grate class has to match the load: pedestrian traffic, passenger cars or trucks. A channel also needs a slope to its outlet and a connection to a pipe or catch basin. See our channel drain installation page for how those systems are built.

Regrading, swales and slopes around buildings

Pipes only work if the surface leads water to them. Many commercial sites have grading faults that no inlet will fix: a lot that slopes toward a wall, a landscaped bed that traps water against the foundation, or a common area bowl with no outlet.

Fixes include reshaping the soil so it falls away from the building, cutting a shallow vegetated swale along a property line, and adding a berm or a curb cut to guide flow. A walkable swale in an HOA common area can carry runoff to a basin without looking like a ditch. Slopes that have started to wash out also need stabilising with stone, matting or planting so the same storm does not cut the same gully again.

Pavement repair is a separate trade. If asphalt has settled, drainage work can send water to the right place, but the surface may still need patching or overlaying by a paving contractor.

Roof drains and downspouts on larger buildings

A commercial roof delivers a lot of water to a few points. If those downspouts end at the surface, the water flows across the lot or soaks the soil beside the footing. Connecting them to buried solid pipe carries the flow to a basin, a swale or a storm connection.

Underground downspout lines should be solid pipe, not perforated, with cleanouts at the bends so they can be flushed. Where the building is close to a lot line, the outlet needs to point at a place that can take the water. For smaller buildings and residential-scale roofs, see downspout drainage.

What a site visit and drainage plan involves

We start by walking the property in the rain or right after it, when the problem is visible. We note where water enters, where it ponds and where it leaves. We look at the grade, the existing inlets and pipes, the soil and what sits downstream.

From that we propose a layout: which inlets or channels to add, which pipe runs and slopes to use, where the water should end up, and what surface restoration follows. Work on an occupied property is usually staged so that entrances and parking stay open. You get a written scope you can take to your board or owner.

Some sites need more than a contractor's plan. Large disturbed areas, discharge to a public storm system or work near a stream can involve township or county stormwater rules. We will tell you when a job needs an engineer or a permit, and we do not guess about it.

Keeping a commercial drainage system working

A system that works the year it is built will stop working if nobody looks at it. Inspect basins and trench grates a few times a year and after major storms. Clear the grates, scoop sediment from the sumps and check that outlets are open and not buried in leaves or soil.

Winter adds its own problems. Meltwater that cannot reach an inlet freezes into ice sheets, and a blocked outfall can freeze solid. Keeping the inlets clear before the first freeze is much cheaper than treating an ice patch at a store entrance.

This is the general part of the work for a property manager's calendar. Yard-scale solutions that apply to your whole site are covered under Yard Drainage.