What is the recommended seam overlap for geotextile fabric on the sides of a bioretention area?

What is the recommended seam overlap for geotextile fabric on the sides of a bioretention area?

• A. 6 inches
• B. 12 inches
• C. 1 inch
• D. 0 inches

Answer: (A)

Seam overlap ensures a continuous geotextile barrier as the bioretention area is installed and backfilled. Using a six-inch overlap on the sides provides enough fabric-to-fabric contact to prevent soil fines from migrating through seams and to maintain the integrity of the filtration layer and underdrain system as the site settles. An overlap of only an inch or none at all can leave gaps that allow bypass flow or clogging of the underdrain, reducing performance. A twelve-inch overlap is generally more material than needed for typical designs and offers no significant extra benefit, so six inches is the practical, effective choice.

Seam overlap ensures a continuous geotextile barrier as the bioretention area is installed and backfilled. Using a six-inch overlap on the sides provides enough fabric-to-fabric contact to prevent soil fines from migrating through seams and to maintain the integrity of the filtration layer and underdrain system as the site settles. An overlap of only an inch or none at all can leave gaps that allow bypass flow or clogging of the underdrain, reducing performance. A twelve-inch overlap is generally more material than needed for typical designs and offers no significant extra benefit, so six inches is the practical, effective choice.