2022 County-wide Act 167 Stormwater Management Model Ordinance

The 90-day period for Pennsylvania Department of Environmental Protection (PADEP) to review the final 2022 County-wide Act 167 Stormwater Management Model Ordinance ended on November 24, 2022. Under the Pennsylvania Stormwater Management Act (PA Act 167), all Chester County municipalities, both MS4 and non-MS4 permittees, are required to adopt stormwater ordinances consistent with the County's Model Ordinance by May 31, 2023. 

On August 17, 2022, the Chester County Board of Commissioners adopted Resolution 55-22 to amend the County-wide Act 167 Stormwater Management Plan for Chester County, PA to replace the 2013 model ordinance with the 2022 County-wide Act 167 Stormwater Management Model Ordinance. This updated ordinance incorporates PA DEP's comments from their review of the Model Ordinance to improve consistency with their state-wide 2022 Stormwater Management Model Ordinance

Model Ordinance Implementation Workshops

The Chester County Water Resources Authority hosted two implementation workshops to assist municipalities with updating their stormwater ordinance. Links to the recordings and PDFs of presentations delivered at both workshops can be found at this page

Please email us at [email protected] with questions relating to the material presented at these workshops or if you have other questions about the updated Model Ordinance.

Links to updated versions of the adopted Model Ordinance and supporting documents can be found below. The following documents were also updated for consistency with the changes to the Model Ordinance: Appendix B, Appendix E, the Matrix of Minimum Standards, Summary of Changes, and Summary of Options. Municipalities should reference these latest documents when updating their ordinance to be consistent with PA DEP’s 2022 Model Ordinance and the County-wide Act 167 Model Stormwater Ordinance. 

County-wide Act 167 Stormwater Management Ordinance

Note: It is recommended that municipalities adopt the Model Ordinance as a stand-alone ordinance. Municipalities do not need to submit their updated ordinance to the Chester County Planning Commission or the Chester County Water Resources Authority (CCWRA) prior to adoption. After the ordinance has been adopted, we ask that an electronic copy along with the completed “Certification of Ordinance Adoption” (linked below) be submitted to CCWRA at [email protected]

Implementation Resources 

The Chester County Water Resources Authority encourages all municipalities to begin reviewing the adopted Model Ordinance and assessing which optional provisions will be included in your updated ordinance. Municipalities with MS4 permits should plan to update their ordinances to be consistent with the updated County-wide Model Ordinance by September 30, 2022, or by the submission of the fourth Annual MS4 Status Report following permit coverage (for new permittees).. Below are additional resources to assist Municipalities with updating their ordinances to be consistent with the County-wide Model Ordinance. 

The updated Model Ordinance is the culmination of nearly three years of collaboration between Chester County, its municipalities, residents, and other stakeholders. Over this period, the Chester County Water Resources Authority hosted or presented at 36 in-person and virtual public and stakeholder input meetings designed to identify ways to improve the implementation and effectiveness of the County’s 2013 model ordinance. The County solicited additional input through the creation of a stormwater management survey that was distributed to municipalities and residents. The updated Model Ordinance was significantly shaped by the input received through these efforts. 

The updated Model Ordinance was designed to meet the needs of Chester County municipalities, fulfill the standards set forth in the Pennsylvania Storm Water Management Act (“Act 167”), and comply with the regulatory requirements of Pennsylvania Department of Environmental Protections’ (PA DEP) National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) program.  The updates incorporated into the Model Ordinance were also designed to comply with the provisions included in PA DEP's 2022 Model Stormwater Management Ordinance.  

Precipitation Resources

Section 706 of the updated Model ordinance requires inspections of BMPs installed after the adoption of this ordinance to be inspected during or immediately after the cessation of a 25-year or greater storm (for inspections conducted by the municipality) or 10-year or greater storm (all other inspections). Municipalities and those with BMP inspection responsibilities should reference NOAA Atlas 14 when assessing when inspections are required. The chart below provides information on average return intervals for Chester County. 

NOAA Atlas 14 Precipitation Estimates
Average of seven locations throughout Chester County, PA

2-Year Storm1.441.722.312.803.24
5-Year Storm1.792.142.873.514.07
10-Year Storm2.032.462.873.514.07
25-Year Storm2.352.893.954.805.75
50-Year Storm2.583.234.465.646.58
100-Year Storm2.823.575.006.427.47

Links to subscribe to real-time precipitation data from the seven USGS precipitation gages in the County are below:  

Additional precipitation data for Chester County can be found at the following links: