State guides · Pennsylvania · Site work
Do I need a stormwater plan? Pennsylvania rules for patios, driveways and additions
Add enough hard surface and your town wants a stormwater plan; disturb enough ground and DEP wants an erosion and sediment control plan. The limits are different in every municipality. Enter what you’re building and where, and see which rules kick in, straight from each town’s ordinance and the state code.
Lock Haven: no plan under 500 sq ft of hard surface and 5,000 sq ft disturbed. Williamsport: under 1,000 sq ft and 5,000 sq ft disturbed. State College: under 10% of the lot, max 2,500 sq ft. Bellefonte: under 10% of the lot, max 5,000 sq ft. Montoursville: under 5,000 sq ft. Lewisburg: under 5,000 sq ft total, at the engineer’s discretion. Statewide, a written erosion and sediment control plan starts at 5,000 sq ft of disturbance, and an NPDES permit at 1 acre. Checked Nov. 13, 2026.
Stormwater plan checker
Hard surface: roofs, patios, walks, paved or gravel drives, sheds. Ground disturbed: everything you dig, grade or strip, at least the size of the new surface.
DEP, statewide
From each town’s stormwater ordinance and 25 Pa. Code § 102.4 and § 102.5. A screen, not an approval; the municipality has the final word.
Thresholds by town
| Municipality | Exempt from a plan | Notes |
|---|---|---|
| City of Lock Haven § 343-28 | Under 500 sq ft of new impervious area and under 5,000 sq ft of earth disturbance (cumulative) | Over either: volume and rate controls plus a stormwater site plan. We found no separate small-project track. The city also has a stormwater fee. |
| City of Williamsport § 1393.02 | Under 1,000 sq ft of impervious area and under 5,000 sq ft disturbed | Minor plan for 1,000 to 5,000 sq ft of connected impervious area, or 5,000 to 20,000 sq ft disturbed with a point discharge to surface water; full plan above that. |
| State College Borough § 14-210 | Under 10% of the site area, up to 2,500 sq ft | Exempt work still has to meet the recharge and water quality volume rules. Work on a one- or two-family home can also qualify if it doesn’t change stormwater beyond the lot. |
| Bellefonte Borough § 490-9 | Under 10% of the site area, up to 5,000 sq ft | Exempt work still has to meet the recharge and water quality volume rules. |
| Lewisburg Borough § 290-7 | Parcels under 5,000 sq ft of total impervious area and under 15,000 sq ft disturbed | May be granted an exemption at the municipal engineer’s discretion; phases count together. |
| Montoursville Borough § 129-14 | Under 5,000 sq ft of total impervious area for the activity | May skip plan preparation and submission but stays subject to the design standards; gravel counts as impervious. |
Lock Haven also has a stormwater fee ordinance; see our PA stormwater fee guide. Other municipality? Find the office on our Pennsylvania permit lookup.
DEP rules that apply everywhere
Erosion and sediment control BMPs are required on every earth disturbance, including jobs under 5,000 sq ft (§ 102.4(b)(1)).
A written erosion and sediment control plan is required at 5,000 sq ft of total disturbance or more, or when the work could discharge to a High Quality or Exceptional Value water (§ 102.4(b)(2)).
An NPDES permit for construction stormwater is required at 1 acre (43,560 sq ft) of disturbance, counting the whole common plan of development (§ 102.5(a)).
Your county conservation district is the usual contact for erosion and sediment control questions. See our PA conservation district list.
Ways to stay under the limit
- Count before you design. A 20 × 25 ft patio is 500 sq ft, already at Lock Haven’s limit.
- Count what’s already there. Most limits are cumulative, and Lewisburg’s is total impervious area on the parcel.
- Keep disturbance tight. Stockpile areas, access paths and regrading all count as disturbed ground.
- Ask about the small-project path. Williamsport has a minor plan, with a sample in its ordinance. Other towns may have a simplified option too, so ask.
Questions
Do I need a stormwater permit for a patio in Pennsylvania?
It depends on the town. Lock Haven exempts projects under 500 sq ft of new impervious area and 5,000 sq ft of earth disturbance; Williamsport under 1,000 sq ft of impervious and 5,000 sq ft disturbed; State College under 10% of the lot up to 2,500 sq ft; Bellefonte under 10% of the lot up to 5,000 sq ft. Separately, DEP requires a written erosion and sediment control plan once earth disturbance reaches 5,000 sq ft.
Does a gravel driveway count as impervious?
Often, yes. Montoursville’s ordinance says areas designed to initially be gravel or crushed stone are assumed to be impervious. Check your own township’s definition before you assume gravel is free.
When do I need an erosion and sediment control plan?
Every earth disturbance in Pennsylvania has to use erosion and sediment control BMPs, even under 5,000 sq ft. A written E and S plan is required at 5,000 sq ft of disturbance or more, or when the work could discharge to a High Quality or Exceptional Value water. At 1 acre or more you need an NPDES construction permit.
Do small projects add up?
Often. Lock Haven’s exemption is for cumulative earth disturbance, Montoursville counts from the date its chapter was enacted, and Lewisburg applies its limit to the total development even if it’s built in phases. A shed this year and a patio next year can push you over.
What if I’m exempt?
Exempt from submitting a plan isn’t exempt from everything. State College and Bellefonte still apply their recharge and water quality volume standards, Montoursville keeps its design standards, and Lock Haven’s exemption doesn’t lift the state water quality rules. DEP’s erosion control rules apply no matter what.
Sources: City of Lock Haven, Code § 343-28, Exemptions; City of Williamsport, Codified Ordinances § 1393.02, Exemptions; Borough of State College, Code § 14-210, Exemptions, Waivers and Exclusions (Ord. 2228, Dec. 16, 2024); Borough of Bellefonte, Code § 490-9, Exemptions; Borough of Lewisburg, Code § 290-7, Exemptions; Borough of Montoursville, Chapter 129 Stormwater Management, § 129-14 (Ord. 492, Sept. 12, 2022); 25 Pa. Code § 102.4, erosion and sediment control requirements; 25 Pa. Code § 102.5, permit requirements. Checked Nov. 13, 2026.
Muthler Landscaping & Construction · Lock Haven, PA
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Cite as: Muthler Landscaping & Construction, “Do I Need a Stormwater Plan? PA Rules for Patios and Driveways,” https://muthlerlandscaping.com/state-guides/pennsylvania/stormwater-plan-rules/ (last checked November 13, 2026).
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