New Jersey Department of Environmental Protection (NJDEP) is in the process of certifying removal efficiencies of total suspended solids (TSS) for various manufactured treatment devices (MTDs). Prior to the certification, the removal efficiencies are verified by New Jersey Corporation for Advanced Technology (NJCAT) under some specific laboratory testing and field monitoring conditions. However, the TSS removal performance is expected to vary with operating flow rates, unit sizes, and laboratory or field evaluation techniques. Several technical issues related to the uniform certification have been researched. Among them are difference between TSS and suspended sediment concentration (SSC), extrapolation of operating flow rates, unit size scaling, impacts of particle size and influent concentration, and possibility of bottom sediment re-suspension. NJDEP has made amendments to the TARP field monitoring protocol to further constrain the field monitoring conditions and to additionally require the particle size measurements and the sediment re-suspension tests. Beyond the TSS removal performance, unit-sizing methodology and device maintenance requirements may need to be verified and certified.