The Michigan Department of Transportation (MDOT) has officially published the results of a two-year evaluation of the Maintainable Weep Hole Filter by JET Filter System. Following the successful demonstration, the product is now included on the AASHTO Product Evaluation List (APEL) under DOT-approved drainage systems.

This placement affirms the filter’s value in modern retaining wall drainage technology and provides engineers and contractors with a trusted solution to combat hydrostatic pressure relief issues behind culverts and walls.

AASHTO, the American Association of State Highway and Transportation Officials, oversees infrastructure standards nationwide. Their APEL serves as a vetted resource of innovative and approved products for transportation infrastructure drainage systems.

Being listed on the APEL reflects product performance under rigorous testing, which positions JET Filter as a go-to choice for DOT drainage applications nationwide.

The demonstration project involved the installation of 52 culvert weep hole filters in a twin-barrel box culvert along US-31 at the Macatawa North Branch. Conducted by Michigan DOT in partnership with JET Filter System, the study evaluated:

• Different filter sizes and configurations

• Varying geotextile filter weep hole fabrics

• System durability under hydraulic and structural stress

This was a critical test of a box culvert drainage solution in a high-flow environment.

Following the successful test results, Michigan DOT issued a state-wide special provision allowing the Maintainable Weep Hole Filter to be used in new or existing retaining walls. This makes it one of the first DOT-evaluated drainage systems of its kind approved at the state level.

Without proper drainage, culverts and retaining walls suffer from trapped moisture that leads to:

• Soil erosion

• Wall cracking and failure

• Increased maintenance costs

The Maintainable Weep Hole Filter addresses these issues by allowing water to escape while preventing backfill loss—and it can be flushed or inspected over time, increasing lifespan and reducing repair cycles.