Stormwater Vaults: Maintenance & Inspection Essentials

Stormwater vaults are an effective way to manage runoff when surface space is limited – but because they’re underground, they’re often forgotten until a problem arises. Regular inspections and maintenance are essential to keep these systems functioning properly and in compliance with local stormwater regulations.

This guide covers the basics of stormwater vault maintenance, key components to inspect, and best practices to help property owners and managers protect their investment.

What Is a Stormwater Vault?

A stormwater vault, sometimes called an underground detention system, is a large subsurface structure designed to temporarily hold stormwater runoff and release it slowly into the drainage system.

Vaults are commonly installed beneath parking lots, courtyards, and landscaped areas in commercial, municipal, and institutional properties. Because they’re out of sight, vaults require specialized maintenance and inspection procedures to ensure long-term performance.

Why Vault Maintenance & Inspection Matter

Even though a stormwater vault isn’t visible, it plays a critical role in controlling runoff and protecting water quality.

Here’s why routine inspection and maintenance are so important:

• Prevent flooding and failures: Sediment buildup and blocked outlets reduce storage and flow capacity, leading to backups or localized flooding.
• Protect water quality: When sediment and debris accumulate, pollutants like oil and heavy metals can bypass treatment.
• Stay compliant: Most jurisdictions require proof of stormwater system inspections under MS4 or other stormwater permits.
• Extend lifespan: Regular maintenance helps prevent structural deterioration, saving thousands in potential repair or replacement costs.

Key Components to Inspect

During an inspection, it’s important to review every element of the vault system.

1. Access Risers and Manhole Covers
   Check that all lids are secure, watertight, and clearly labeled for stormwater access. Ensure risers are clear of parked vehicles or landscaping that might block entry.
2. Inlet and Outlet Pipes
   Look for sediment, debris, or damage that could block flow. Any obstructions should be cleared immediately.
3. Sediment Storage Sump or Pretreatment Chamber
   Sediment tends to settle in these chambers. If buildup reaches 10–25% of total depth, it’s time for a cleanout.
4. Overflow or Emergency Spillway
   Confirm that the overflow path is clear. Blocked spillways can cause pressure buildup or flooding.
5. Structural Integrity
   Inspect the vault walls and floor for cracks, leaks, or joint separation. Structural damage should be assessed by an engineer.
6. Treatment Media or Filter Cartridges (if applicable)
   If your vault includes treatment components like filter cartridges or sand media, check for clogging and bypass flow. Replace or clean as needed.
7. Safety Features
   Ensure confined space protocols are followed and access points are properly marked to prevent unauthorized entry.

Recommended Inspection & Maintenance Schedule