The Municipal Separate Storm Sewer System (MS4) General Permit (GP) is on every regulated small MS4 community’s ongoing “to-do list.” A catch basin inspection program is a component of the GP.

Although permits differ by state, requirements typically begin with prioritizing inspection and cleaning based on a permittee’s knowledge of the system. GPs also require permittees to conduct routine inspections, cleaning, and maintenance of catch basins, and typically include a schedule of routine cleaning to ensure no catch basin sump is more than 50% full at any time.

With increased demand on municipal staff, inspections of catch basins are often secondary which could lead to non-compliance with GP requirements. Without a systematic program, inspections may not be performed in a timely manner and the highest priority attention may not be given to catch basins with excessive sediment accumulation. In addition, documenting, recording, and generating an inspection program report can be labor intensive and may not be a priority task for municipal personnel.

The following steps are recommended to meet the MS4 requirements for inspection of catch basins:

  • Formulate a systematic, efficient inspection program that complies with the MS4 GP Minimum Control Measure (MCM) 6.
  • Generate maps to inventory catch basins and to guide a prioritized inspection schedule.
  • Inspect and record the condition of each catch basin and measure and document the depth of sediment as well as sump depth, if not already known, to determine if catch basins have excess sediment accumulation (more than 50% sump full).
  • Document observations related to potential illicit discharges (debris, waste dumped, foam, oil sheen, etc.) and criticality to support investigation, renewal, or rehabilitation.
  • Evaluate the data collected, summarize results, and make prioritized recommendations for sediment removal and/or other corrective actions.

Wright-Pierce can help you with each of the items above! These deliverables will enable municipalities to better utilize resources and comply with the GP. If desired, field technicians in our infrastructure assessment group, who are certified in the industry standard established by NASSCO, will conduct a full condition assessment of stormwater infrastructure. Wright-Pierce is also available to assist with structural inspection and/or mapping of outfalls, dry weather outfall inspection and sampling, and more.

If you’ve been using a “catch-as-catch-can” approach to your catch basin inspection program, contact us today for a consult about how we can help support your MS4 GP compliance efforts.