The Pennsylvania Storm Water Management Act (Act 167) mandates municipalities to update ordinances to regulate development in line with the watershed stormwater plan. This sheet provides examples of stormwater ordinances from Allegheny County municipalities.
Riparian Buffers
Riparian buffers, vegetated areas along streams, improve stormwater runoff by absorbing and filtering floodwaters. Increasing the buffer area beyond the current 35-foot requirement under Act 167 stormwater ordinance offers greater protection.
Rainfall Amounts
To account for increased rain in Western PA, consider using the upper 90% confidence interval for storms from NOAA Atlas 14. This adjustment enhances runoff protection and will be included in the new PA Stormwater Manual for larger developments.
Special Districts
If certain areas of your municipality face flooding, stream erosion, or water quality issues, designate them as special districts with stricter stormwater controls to ease problem areas. For examples, see City of Pittsburgh Special Districts handling.
Future Maintenance
Pre-treatment localizes sediment maintenance, reducing the need to service entire basins or stormwater control measures. Ordinances encouraging forebays or water quality structures improve longevity and ease maintenance. Adequate access (roads, underground system size, and entry ports) also simplifies inspection and upkeep. For reference, see Monroeville Ordinance
Rate Control – Control the rate of stormwater flowing off a site. Early stormwater management is focused on controlling runoff rates to mitigate downstream flooding. Stormwater ordinances can reduce runoff rates from developed sites compared to pre-existing conditions. Currently, approximately 50% of Allegheny County is covered by a special release rate.
Volume – Control stormwater runoff volume by removing excess runoff via infiltration, evapotranspiration, and capture and reuse. Stormwater control measures for volume control are typically infiltration or extended detention based. Non-structural controls can be considered for volume control credits in ordinance. For reference, see McCandless Volume Credits.
Water Quality – Control water quality flowing off of a site, especially sediment, nitrogen, and phosphorus. Consider formally requiring pre-treatment of stormwater with forebays or filters before entering rate and volume control facilities like infiltration basins or rain gardens. For reference, see Monroeville Ordinance.
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