Fixing a wet yard: grading, drains and the erosion rules in Pennsylvania

Updated November 10, 2026 · KeystoneProGuide editorial team

Why does water collect in a yard?

Usually because of the grade, the soil or both. Penn State Extension says a finished grade should slope enough to carry surface water away from buildings, and that the subgrade should be free of depressions where water can collect. Soil type sets how fast water soaks in: Penn State's rain garden guidance puts infiltration at about 2.5 inches an hour in sandy soil, half an inch in silty soil and only a third of an inch in clay. And construction often leaves subsoil severely compacted, Penn State says, which slows drainage further.

So the first job is diagnosis. Watch the yard in a heavy rain, as Penn State suggests, and note where water comes from, where it goes and how long it stands.

What grade does Penn State recommend?

Where possible, a slope away from the foundation of 1 to 4 percent, which is a drop of 1 to 4 feet for every 100 feet. The slope should be enough to move water, yet gentle enough for easy mowing and use. On a lot where the house is built into a hillside, Penn State says drainage swales are needed around the building, and where slopes are steep or grades change sharply it suggests considering retaining walls or ground covers.

How the grade is built matters too. Penn State says rough grading is done on the subsoil before topsoil goes back, that bulldozers can compact soil and a skid steer or tractor with a grading blade is preferable, and that a good lawn then needs at least 4 to 6 inches of topsoil. Mixing some topsoil into the top of the subsoil eases the transition and improves drainage between the layers.

What drainage options are there?

The options run from reshaping the ground to burying pipe. Penn State's own guidance mentions two: regrading, and drainage swales where a house sits into a hillside. Contractors also offer French drains, catch basins, dry wells and surface drains. Angi, a cost survey, gives these national price ranges:

Overall, Angi gives a national average of $4,634 for yard drainage, with most homeowners paying $2,147 to $7,176, and lists lawn grading separately at $1,025 to $3,300. HomeAdvisor's older figure for grading or resloping is $1,000 to $3,000. These are prices only: whether a swale or a pipe suits your yard is a question for a site visit.

Is there a way to keep the water on site?

Yes, and Chester County's planners favor it. A rain garden is a shallow planted basin that takes runoff from a downspout or driveway and lets it soak in. Penn State's siting rules are specific: at least 10 feet from the foundation, not near a septic system, well or utilities, a slope under 10 percent, and a drainage test first, with another site chosen if test holes take more than 24 hours to drain. The Chester County Planning Commission says new stormwater design guidance recommends green practices such as rain gardens, swales and porous pavement wherever possible.

Healthy turf helps as well. The Department of Agriculture says a dense, healthy lawn can help reduce erosion and runoff. On clay or sloping ground, the EPA's WaterSense program suggests splitting irrigation into shorter cycles so water soaks in instead of running off.

When does a regrade need an erosion plan or permit?

State law sets two thresholds, and local rules add more.

• Any size. Erosion and sediment controls are required for every earth disturbance, including those under 5,000 square feet.
• 5,000 square feet or more. A written erosion and sediment control plan is required, prepared by someone trained in erosion control. The Bucks County Conservation District says it must be kept on site, and that many municipalities require the district to review it.
• 1 acre or more. A construction stormwater permit is needed before work starts.
• In or along a stream. The Delaware County Conservation District says many activities in streams, ponds and wetlands need a separate state permit.
• In Philadelphia. Earth disturbance of 5,000 square feet or more needs a Philadelphia Water Department stormwater review before a city permit.

The state rules also tell the contractor how to work: minimize the extent and duration of disturbance, protect existing drainage features and vegetation, and avoid compacting the soil.

Does a drainage contractor need to be registered?

Yes, for most of this work. The Attorney General's guidance says landscapers who place drainage systems at a private residence must register as home improvement contractors. Ask for the PA registration number and check it.

What else should you tell the contractor?

Where your private lines run. Pennsylvania One Call says the utilities do not mark privately owned lines, and lists sprinkler systems or drainage pipes, septic systems and power or gas lines to a pool or grill among them. A drain trench can cross any of them, so mark them before work starts.

If water is reaching the house, start with the warning signs guide, and for the full set of rules, see what Pennsylvania requires. More prices are in the cost guide, and local businesses are on the landscapers directory page.

Sources

1. Lawn Establishment, Penn State Extension
2. How to Make a Rain Garden, Penn State Extension
3. Homeowners and Applicators, Pennsylvania Department of Agriculture
4. Watering Tips (WaterSense), U.S. Environmental Protection Agency
5. How Much Does Yard Drainage Cost? [2026 Data], Angi
6. How Much Does Landscaping Cost? [2026 Data], Angi
7. How Much Does Landscaping Cost?, HomeAdvisor
8. 25 Pa. Code § 102.4. Erosion and sediment control requirements., Commonwealth of Pennsylvania (Pennsylvania Code)
9. 25 Pa. Code § 102.5. Permit requirements., Commonwealth of Pennsylvania (Pennsylvania Code)
10. Projects Under One Acre, Bucks County Conservation District
11. Frequently Asked Questions: Home Improvement Contractor Registration, Pennsylvania Office of Attorney General
12. Private Lines, Pennsylvania One Call System
13. Permitting (Conservation District), Delaware County, Pennsylvania
14. Get a Retaining Wall Permit, City of Philadelphia
15. eTools: Stormwater Best Management Practices, Chester County Planning Commission