Iowa Dot Gives Scour Protection Method Green Light

The Iowa Department of Transportation has issued a Public Interest Finding (PIF) for the use of ScourStop transition mats on state projects. With the

The Iowa Department of Transportation has issued a Public Interest Finding (PIF) for the use of ScourStop transition mats on state projects. With the issuance of a statewide PIF and Federal Highway Administration (FHWA) approval, designers now can specify the technology [as a proprietary product] on both state and federally funded projects.

Reportedly implemented on a project-by-project basis across the state for several years, ScourStop Transition Mats offer a biotechnical replacement for rock rip-rap that imparts what product engineers contend is permanent protection against scour and erosion at drainage outlets, overflow structures, and stream banks, plus an aesthetically pleasing complement to natural settings. The system comprises a semi-rigid, high-density polyethylene plastic mat (4 ft. x 4 ft. x 0.5 in.) featuring voids throughout the structure that enable vegetative growth. Once vegetated, the mat is largely shielded from the sun and undetectable. By integrating vegetation with latest polymer material technology, ScourStop mechanically protects soil from scour and erosion until shear forces have dissipated; and, the synergy of mechanical protection and vegetation allows the system to resist higher shear stresses and velocities than vegetation alone or rock rip rap.

A Public Interest Finding is a state DOT request for FHWA approval that allows an exception to be made to one of many state or federal rules, policies, or procedures that apply to construction contract lettings. While PIF approval typically remains a rare occurrence, that granted for ScourStop is especially notable, since it is only the eighth blanket PIF (allowing general use statewide) approved by the FHWA in the last 11 years.

Notes Tom Carpenter, creator of ScourStop Transition Mats and President of Erosion Tech LLC, The Public Interest Finding will enable better statewide compliance with NPDES [National Pollutant Discharge Elimination System] Phase II requirements and provides the impetus to specify vegetated, soft-armor best management practices.