Many USPS® sites have stormwater retention or detention basins to manage stormwater runoff to prevent flooding, erosion, and discharge of pollutants to surface waters. Sites with retention or detention basins require specific management practices and may be regulated under federal, state, or local laws.
Stormwater basins are man-made depressions that collect stormwater runoff and control discharges. These basins generally fall within the following two categories:
n Retention Basins (also known as wet basins or wet ponds) are designed to retain water for extended time periods. They typically have a permanent pool of water throughout the year (or at least during the wet season) and often look like man-made ponds.
n Detention Basins (also known as dry basins or dry ponds) are designed to detain or temporarily store water after a storm. Unlike retention basins, detention basins are designed to empty water completely and they do not have a large permanent pool of water.
Routine preventative maintenance such as landscaping and inspections, along with prompt corrective actions for any issues identified, are required to keep the basins functioning properly and to maintain water quality. Sites with basins must:
n Identify the location of all retention and detention basins on the property, including risers and outfalls.
n Conduct and document routine visual inspections of each retention and detention basin using the inspection checklist (see blue.usps.gov/sustainability/environmental/_docs/forms/form-sw-ret-det-inspectionchecklist.docx).
n Perform landscaping and grounds maintenance necessary to ensure basin functionality.
n Adhere to the Postal Service™ Zero Discharge Policy, including general good housekeeping and chemical storage requirements.
n Conduct preventive maintenance and complete any other routine repairs and corrective actions necessary to ensure proper basin functionality and stormwater drainage by doing the following:
n Cleaning and removing debris and trash,
n Accumulated sediments, and
n Excess vegetation.
For corrective actions involving structural repairs, alterations or upgrades, and other non-routine repairs, contact the Facilities Response Line at 855-444-6375.
n Operate vehicles on embankments or in basins (except for light-duty lawn equipment necessary to maintain grounds).
n Put landscape waste (e.g., grass clippings or branches) or other materials in basins.
n Apply pesticides within the basin.
Note: Stormwater basins may require permits or have specific design and operating standards in addition to what is discussed above. Review local regulations and issued permits and comply with all requirements.
For more information about stormwater basins:
n Review the Stormwater Retention and Detention Basins Environmental Compliance Bulletin / Standard Work Instruction at blue.usps.gov/sustainability/environmental/_pdf/bp-sw-ret-det.pdf.
n Consult your designated USPS Environmental Specialist at blue.usps.gov/sustainability/regional-environmental-compliance-all.htm.
— Environmental Affairs and Corporate Sustainability,
Corporate Affairs, 5-15-25
