The BioPod biofilter by Oldcastle Infrastructure was tested in accordance with the State of Washington’s Technology Assessment Protocol-Ecology (TAPE) and was granted a General Use Level Designation (GULD) by the Washington Department of Ecology (WDOE) in March 2018. The BioPod was tested at WDOE’s Ship Canal Stormwater Test Facility in Seattle, Wash. The Ship Canal Facility is recognized as a challenging site since runoff is typically high in organics, oily, and has a very fine particle size distribution. The BioPod was able to meet performance requirements for Basic (TSS), phosphorus, and enhanced (metals) treatment at the Ship Canal Facility, but it only treated a small portion of the water year before maintenance was needed to maintain the prescribed hydraulic loading rate. A stipulation of the initial GULD required subsequent hydraulic testing of a BioPod serving a “more typical” drainage to determine an appropriate target maintenance interval. Herrera Environmental Consultants conducted the original BioPod testing to gain GULD approval and was retained by Oldcastle Infrastructure to conduct the additional required hydraulic testing. Although hydraulic testing has been listed as a requirement in the GULD documents for several current treatment products, Oldcastle was the first company to respond. Consequently, Oldcastle and Herrera had to work closely with WDOE to define meaningful test requirements and develop an appropriate test schedule. The monitoring program started in October 2020 at a BioPod that serves a roadway drainage in Des Moines, Wash. The hydraulic capacity of the unit was tested quarterly for more than a year to establish an annual target maintenance interval. This presentation will focus on the test parameters, program challenges, field data, and monitoring results.