Delaware County, PA Environmental Rules: Stormwater Management (2026)

Chapter 187, titled the 'Ridley Creek Stormwater Management Ordinance of 1989' and adopted under Ord. No. 89-2, is narrower than a countywide stormwater code. Section 187-4 limits applicability to land alteration and disturbance tied to subdivisions and land developments within the Ridley Creek watershed, in cities, boroughs, or townships that have no subdivision ordinance in effect or that have specified coverage under this chapter. Where it applies, § 187-7 bars any earth-moving or land-disturbance activity from starting until a stormwater management plan, reviewed by a qualified engineer, is approved by the municipality.

Section 187-8 exempts subdivisions or land developments creating no more than 7,500 square feet of new impervious area from the full plan requirement, though a sketch plan conforming to § 195-22F of the County's Subdivision and Land Development chapter is still due to the municipal engineer, and a parcel under single ownership gets only one such exemption before the whole parcel needs a full plan. Section 187-10 requires any landowner altering land that affects runoff to keep the postdevelopment peak rate no greater than predevelopment, or otherwise manage volume, velocity and direction to protect health and property. 85 inches respectively. 3 rather than a County-specific fine schedule.