KAREN D. HAMEL, CSP, CIT
Storm Drain Inlet Protection Torture Test: Real-World Performance of Grizzly Mat
The main idea behind storm drain inserts is to capture dirt and trash so that it’s not carried downstream, or collected way down at the bottom of the catch basin where it’s a nuisance to remove. Bottom line: most inserts just aren’t up to the task. We’ve seen them fail time and time again – not to mention the pain-in-the-back that they are to service.
How many of these failures have you experienced with your current inlet drain protection?
When we set out to make Stormtration™ Grizzly Storm Drain Filter Mat, we elevated our design criteria to prevent all of these problems, and to make it easy for your team to install and maintain your storm drain inlet protection devices in less than 10 minutes.
Design Requirements for Effective Storm Drain Inlet Protection
Making a better version of what currently fails wasn’t an option. The Grizzly Mat was designed with these six criteria in mind.
Thor’s Hammer Torture Test: How We Push Storm Drain Protection to the Limit
Even though there are stringent Stormwater Regulations that require pollutants to be captured, no test protocols exist for validating the effectiveness of storm drain filters. So we designed our own test.
We built a trough that simulated a storm drain, and designed conditions that would subject that rain to a 90-minute extreme storm event.
We needed to know:
To make sure it would hold up under a variety of circumstances, we subjected the Grizzly Mat with five progressively demanding tests:
Stage 1: Clean Water Flow Simulation
Clean water to mimic the beginning of a storm event where rainwater slowly flows into storm drains without picking up much sediment.
Stage 2: Moderate Stormwater With Sediment
Sediment and debris are added to create muddy water, and water flow rate is increased to mimic a moderate rain event.
Stage 3: High Flow Water Stress Test
Heavy clean water flow is introduced to try to wash through the collected sediment and debris.
Stage 4: Extreme Stormwater and Sediment Load
High flow muddy water (maximum sediment, debris and water flow – similar to construction site conditions) is introduced to determine when the Grizzly Mat’s bypass feature will engage to prevent street flooding.
Stage 5: Post-Storm Sediment Stability Test
High flow clean water is introduced to see if it will displace the accumulated sediment.
The Results: Grizzly Mat Performance
In every test condition, the Grizzly Mat continued to perform exactly as intended: allowing clean water to pass while capturing sediment and debris at street level. We got a resounding YES to each of our test questions.
| Test Question | Test Focus | Outcome |
|---|---|---|
| Does the device provide enough flow capacity? | Flow Capacity | YES — Maintained flow capacity even with heavy sediment accumulation. |
| Does the bypass engage at the appropriate time? | Bypass Engagement | YES — Bypass engaged only during extreme Stage 4 conditions. |
| Does the street fully and quickly drain after a rain event? | Drainage Performance | YES — Complete drainage occurred in approximately 6 minutes. |
| Does the device keep more than 80% of sediment out of the inlet? | Sediment Capture | YES — 89.8% sediment capture rate during testing. |
Smarter Storm Drain Inlet Protection: Easier, More Reliable, Lower Maintenance
For crews responsible for stormwater compliance, inlet protection has to do more than capture sediment. It must maintain flow capacity during storms, prevent on-street flooding, and allow the system to drain quickly once the rain stops.
The Thor’s Hammer Torture Test showed that Grizzly Mat delivers on those requirements — maintaining flow, capturing sediment efficiently, and allowing complete drainage even under severe storm conditions.
When stormwater compliance, crew safety, and maintenance efficiency matter, Grizzly Mat offers a smarter approach to storm drain inlet protection. It keeps sediment at street level for easy cleanup, maintains flow during heavy storms, and installs in minutes without removing the grate.
Regulatory Approval: Grizzly Mat is recognized by the Pennsylvania Department of Environmental Protection (PA DEP) as an approved stormwater management solution.
- Approved Post-Construction Erosion and Sediment Control BMP
- Approved Antidegradation Best Available Combination of Technologies (ABACT) for High Quality (HQ) and Exceptional Value (EV) watersheds
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