The US EPA has set forth guidelines in the NPDES Phase II Storm Water Rule that outlines best management practices (BMPs) for controlling storm water pollutants.  Inlet protection devices help to satisfy NPDES Phase II initiatives to address the concerns of construction site storm water runoff and help protect our nation’s water sources.  Numerous products have been developed in recent years with varying application methods and results.

Some inlet protectors are comprised of injection molded plastic housings of specific size and shape – these are expensive to tool and can be overly complex.  Others, such as the IDOT approved Inlet Filter, are comprised of welded steel angles and channels designed to fit a specific size drainage structure.  The steel frames support a sediment bag which filters the storm water.  Various geotextile sediment bag medium, oil absorbent pouches, and other filtration devices can be utilized with the Inlet Filter.  The sediment bag hangs below grade catching stormwater runoff and debris as it is washed into the drainage structure.  The Inlet Filter and other similar inserts offer overflow protection when the sediment bag is completely filled during a major rain event.  This allows roads and jobsites to completely drain, thus eliminating the hazards of standing water and/or jobsite erosion. These types of inlet protectors are preferred by most engineers because of their durability, sediment bag capacity, ease of installation/maintenance, and important overflow benefits.  The problem with these fixed size inlet protectors is that there are hundreds of castings for various curb and catch basin inlets, and one size will not fit all.  Contractors must order and stock specific sizes referencing exact drainage casting make and model numbers.  This is especially difficult for pre-existing road work with older specifications.  Furthermore, the fabrication of the welded steel frames is tedious and labor intensive resulting in higher levels of finished goods, long lead times, and elevated prices.

Other more universal, disposable inlet protectors are comprised of a variety of geotextile fabrics and utilize alternate suspension methods. These sediment bags may be suspended from straps or chains, which are wrapped around or attached to the grate.  Some bags have slots for re-bar used to support two sides of the sediment bag on the outside of the grates, above grade.  Others require that the grate be inserted into a geotextile envelope preventing sediment to enter at the surface.  These “fabric-only” products are more difficult to install and maintain than the drop-in style inlet protectors.  The grate must be lifted along with the full sediment bag when maintenance (emptying) is required.  This often requires machine assistance and multiple laborers.  A bigger problem with these devices is that they leave the roads and surrounding inlet areas with a large amount of sediment at the surface due to reduced or no overflow capabilities.  Engineers tend to shy away from these lower cost options.

In short, State DOTs and Municipalities across the country are struggling to comply with mandates set forth by EPA to find a universally accepted structural BMP to address the issue of storm sewer inlet protection.  We intend to solve that problem.  Our solution is a configurable, adjustable filter frame suspension system made of 11 gauge stamped steel components with built in overflow feature.  This inexpensive, configurable system will replace the welded framework required on current Inlet Filters and offer more versatility to fit the wide array of drainage structures throughout the United States.  As did the previous welded device, this frame is designed to drop into the casting opening and hang suspended on the load bearing lips of the casting beneath the drainage grate.

The configurable system incorporates a series of corner bracket hangers (for rectangular designs) with extruded holes spaced ½” apart connected by channel lengths with through holes at 1” spacing.  This allows for width and length adjustments in ½” increments and up to 5” per side using only ¼-20 thread forming fasteners.  Single and double hangers along with universal corner brackets are offered for different rectangular shaped castings depending on available load bearing surfaces and/or grate contours.  The unique design feature of this system is the hanger hook concept.  These are permanently fixed on some corners, but may also be angularly rotated and positioned at various heights creating a perfect fit for rolled curb, concave, and gutter style storm castings using the universal corners.  This is not possible with other “adjustable” rigid framing technology, which are designed for basic flat round or rectangular grates.

The round designs in our system consist of a specific length channel rolled to standard inlet opening diameters.  Channels are cut to length then rolled.  The channel ends are connected at one of four hanger hooks, each of which contains two fasteners.  Both round and rectangular designs feature 2 lift handles at various spacing widths.  Some rectangular designs with longer spans may incorporate 2 lifting bars in parallel and centered along the width, spaced 14”-16” apart.  Other, smaller rectangular frames feature 2 convenient corner lift handles located at opposite ends and corners.  The lift handles add structural reinforcement to the round designs and allow for easy removal with our universal maintenance tool in any framework.  The maintenance tool is a proprietary design which also incorporates grate lifting hooks, thus serving 2 purposes:  1. to remove the grate easily with up to 2 people, and 2. to quickly and efficiently remove and maintain the inlet filter frame and sediment bag assembly.   

The sediment bag is attached to the frame using a stainless steel quick release style clamping band which is threaded through a seam at the top of the bag.  The cone shaped bag is designed so as not to expand beyond the frame’s perimeter, which is slightly smaller than the clear opening of the casting.  The sediment bag is comprised of an inner and outer layer.  The outer reinforcement layer is typically a flexible polyester mesh weighing at least 4 oz/sq yd.  The mesh fabric may be brightly colored to call out notice of inlet protection, and in our case we use the color orange.  The inner filter layer is a geotextile fabric (either woven or non-woven) with a typical flow rate between 140 and 200 gpm/sqyd.   We have also incorporated a flexible plastic deflector shield that will funnel all storm water into the sediment bag.  This extruded deflector is easily cut to length and is fitted into the U-channel framing held in place with the corner/hanger fasteners and the clamping bands.  Some inlet castings have open curb backs allowing water to bypass the main drainage grate and filter system.  For these designs we have developed a sediment bag with curb guard flap.  The flap is sewn to the main sediment bag at the back of the frame and is pulled up in front of the curb box opening; this design has been common with the traditional Inlet Filter’s prior configurations.  This flap has posed issues in the field where a contractor may not have the means or surface area to stake down or hold the flap in position to effectively cover the curb opening.  Our latest curb flap improvement and invention in this field is the incorporation of neodymium magnets at each corner to secure the flap to the top of the curb box casting.  The magnet is 1” x 1” x .25” square shape inserted into a Velcro pocket hem at the end of the curb box flaps, although various size neodymium (rare earth) magnets are commercially available.  Typically 1 magnet with approx 30 lbs holding force at each corner is required, however additional magnets may be inserted for especially long curb openings requiring additional holding forces.   Another field issue is street sweepers getting hung up in the geotextile fabric and tearing portions away.  The new curb guard flaps are 2-ply utilizing the brightly colored Orange polyester mesh, which adds strength and bringing notice to the curb flaps.  If a street sweeper does catch the flap, the magnets will give way as a fail safe and the fabric will not be torn apart.  Furthermore, the highly visible curb guard flaps may also incorporate company logos or other warnings such as “Dump No Waste - Drains to Lake.”   

The FLeXstorm Inlet Filter System will allow contractors to make adjustments as needed in the field.  Once a job is complete the contractor can take the re-usable filter frame to the next jobsite requirement and equip it with a new sediment bag using only a screwdriver.  Contractors may also break down the components and re-assemble into a completely different model by ordering new or modifying the existing channel lengths.  Parts breakdowns and assembly instructions for each inlet filter requirement are easy to follow with corner bracket holes labeled A, B, C and channel holes labeled 1, 2, 3.  All steel components are corrosion resistant (zinc plated) and stamped with the FLeXstorm part numbers. Again, this will be the first universally accepted design standard for inlet protection guaranteed to fit any drainage structure throughout the United States.