Abstract: A storm sewer filtering apparatus is provided having a filter bag forming a rectangularly shaped substrate retaining volume. A flat bottom surface remains at the bottom of the filter bag and forms the majority of the filtering surface. Geotextile fabric forms a filtering media and incorporates a plurality of woven webbing reinforcement straps to provide additional strength to the finished filter bag. The woven webbing is affixed to the geotextile filtering media by conventional stitching methods, and extends beyond the edge of the respective sidewall for attachment to a drain grate. Rigidly affixed to each terminal end of the attachment strap is a retaining block that is linearly elongated and made of a rigid material, such as wood, metal, or hard plastic.