Storm drain inlets help manage runoff on construction sites, but they can also allow sediment and other pollutants to enter stormwater systems if they aren’t properly protected. Installing inlet protection is an important part of stormwater management, but simply placing a BMP over or around a drain doesn’t guarantee it will work.
For Colorado construction projects, inlet protection should be appropriate for site conditions, maintained throughout construction, and included in routine stormwater inspections.
Common Storm Drain Inlet Protection Mistakes
- Choosing the Wrong Type of Inlet Protection
Not every inlet protection method works for every location. The appropriate BMP depends on factors such as drainage area, expected runoff volume, inlet design, and surrounding site conditions.
For example, a device that works well in a low-flow area may not be suitable where runoff concentrates quickly. Improperly selected or installed protection can cause bypass, flooding, or sediment buildup.
How to avoid it: Choose inlet protection based on the site’s drainage conditions and applicable project requirements. Follow manufacturer instructions and ensure the BMP allows water to drain as intended.
- Allowing Sediment to Build Up
As runoff carries sediment toward an inlet, material can accumulate around the protection device. If sediment isn’t removed, it may reduce drainage capacity, cause ponding, or contribute to bypass during rainfall.
How to avoid it: Check inlet protection during routine inspections and after relevant storm events. Remove accumulated sediment when needed and repair or replace controls that are no longer functioning properly.
- Installing Protection Incorrectly
Even an appropriate BMP can fail if it isn’t installed correctly. Gaps, loose materials, poor placement, or an unsecured device can allow sediment-laden runoff to pass directly into the storm drain.
How to avoid it: Install inlet protection according to the approved specification, manufacturer instructions, and project requirements. Check for gaps, secure the device properly, and confirm runoff is being directed through the intended treatment or filtering area.
- Ignoring Runoff Bypass
Water naturally follows the path of least resistance. If runoff flows around the inlet protection instead of through it, sediment may enter the storm drain without being filtered.
Bypass can occur when protection is poorly fitted, nearby grades direct water around the device, or runoff exceeds the BMP’s capacity.
How to avoid it: Evaluate the surrounding grades and drainage patterns during installation and inspections. Make sure the protection is appropriate for the expected flow and address any areas where runoff can circumvent the control.
- Forgetting About Inlet Protection as the Site Changes
Construction activities can change drainage patterns as grading progresses, pavement is installed, and new areas become disturbed. Inlet protection that worked earlier in the project may no longer be adequate.
How to avoid it: Reevaluate inlet protection when site conditions change. Confirm that the Stormwater Management Plan (SWMP) reflects current conditions where required, and adjust BMPs as needed.
Why Routine Inspections Matter
Storm drain inlet protection needs ongoing attention throughout construction. During inspections, look for damaged or displaced controls, sediment accumulation, signs of bypass, standing water, and changes in the surrounding drainage patterns.
Under Colorado’s COR400000 construction stormwater permit, applicable routine inspections are generally required at least every 14 calendar days and after qualifying storm events, subject to the permit’s conditions and exceptions. Identified deficiencies should be documented and addressed within the applicable permit requirements.
Final Thoughts
Storm drain inlet protection is most effective when the right BMP is installed correctly, maintained consistently, and adjusted as site conditions change. Small issues can become larger problems when controls are overlooked, making regular inspections an important part of construction stormwater compliance.
Summit Services Group helps Colorado contractors manage stormwater compliance through inspections, SWMP support, and corrective action guidance.
Contact Summit Services Group to learn how we can help keep your construction site compliant.