FIELD INSTALLATION AND MONITORING OF FILTRATION-ADSORPTION MEDIA USING MULTIPLE DELIVERY SYSTEMS FOR REMOVAL OF METALS FROM STORM WATER

A number of new proprietary devices have recently been developed to deploy treatment media to remove metals and other pollutants associated with storm water. These include systems that are installed primarily at drainage system points nearest the pollutant source, such as catch basins and roof drains.Current case studies underway at the Port of Seattle's Seattle-Tacoma International Airport (STIA) are investigating the performance of commercially available products including media cartridges and a catch basin insert. The configuration and method of deployment of each of these systems results in different hydraulic characteristics requiring tailored methods for design, installation, flow monitoring and water quality sampling to obtain representative performance data.This paper describes issues related to system hydraulics, treatment capacity, and physical configuration that present challenges to monitoring methods and how each of these challenges was addressed. Three water quality monitoring projects are highlighted.Commercially available media cartridge systems and a catch basin insert were deployed within an airport storm drainage system requiring field monitoring under actual operational and runoff conditions. In addition, to simplify screening for larger drainage area applications or implementation of different filtration media, a bench- scale version of the standard commercially available media cartridge will be tested. Following industry standards, flow weighted composite samples for each installation were either collected automatically using flow-meter-controlled automatic samplers or by manual compositing grab samples based on the rainfall hyetograph.At one site, three media cartridge systems treating runoff from an aluminum-zinc alloy-coated steel rooftop were elevated above grade to provide for flow measurement prior to discharge to underground piping. An elevated flow splitter device was also designed, calibrated and installed at this site to measure inflow and to distribute water evenly to all three units simultaneously. Both of these flow monitoring adaptations were employed without altering the intended hydraulics of the commercially available devices. The overall monitoring design was consistent with Washington state TAPE protocols for BMP testing.At another site, the compact underground design of a commercially available catch basin insert was not conducive to direct flow measurement. Conventional monitoring procedures needed to be adapted. In this case, time-paced samples were collected and then manually composited based on the rainfall hyetograph. Additionally, since the catch basin insert is located on a high traffic entrance road to the airport terminal, petroleum hydrocarbon (TPH) removal needed to be accurately determined.The third project, the bench-scaled testing, requires the collection of large volumes of flowweighted composite samples. Custom sampling equipment that incorporated off-the-shelf monitoring instrumentation was designed and fabricated for this purpose. Isco and Sigma samplers were retrofitted to collect up to a 45-gallon composite sample, while concurrently taking a single TPH grab sample at the onset of runoff. This design will allow concurrent sampling that will meet the needs of the airport's NPDES sampling requirements. Storm water samples from two drainage areas of 140 and 460 acres will then be processed through the scaled filtration units to test media performance for the storm water matrix particular to the associated drainage area.