Lower Merion, PA Environmental Rules: Erosion Control (2026)

Section 121-5A limits how much of a site can sit bare during construction: no more than 25% at any one time, though that cap only applies where the pre-development site exceeds four acres, and every bare area must be stabilized within 20 days. Section 121-5B requires a grading or runoff and erosion control permit from the Township Engineer before any grading, excavation, fill or tree clearing, with narrow exemptions for shallow excavations under three feet deep and 1,000 square feet, fills under 10 cubic yards, and any regulated activity creating 1,500 square feet or less of added impervious cover.

Applications must include six copies of plans meeting the Montgomery County Soil and Water Conservation District's standards and the Township's own Erosion and Sediment Control Design Standards, incorporated by reference and available for a $0.10-per-page copying fee. Property owners who believe the chapter creates an unnecessary hardship can request a waiver in writing, but the Township may only grant one after finding the hardship stems from unique physical site conditions, not financial hardship, and that the waiver is the minimum relief needed.