Laserfiche WebLink
• Entire State: For treatment installed downstream of detention, the water quality design <br />flow rate is the full 2-year release rate of the detention facility. <br />4. This General Use Level Designation has no expiration date but Ecology may revoke or <br />amend the designation, and is subject to the conditions specified below. <br />Ecology's Conditions of Use: <br />Filterra"j' units shall comply with these conditions shall comply with the following conditions: <br />1. Design, assemble, install, operate, and maintain the Filterra ' units in accordance with <br />applicable Americast Filterra('�' manuals, document, and the Ecology Decision. <br />2. Each site plan must undergo Americast Filterra* review before Ecology can approve the unit <br />for site installation. This will ensure that site grading and slope are appropriate for use of a <br />Filterra® unit. <br />3. Filterra(9' media shall conform to the specifications submitted to and approved by Ecology. <br />4. Maintenance includes removing trash, degraded mulch, and accumulated debris from the <br />filter surface and replacing the mulch layer. Use inspections to determine the site -specific <br />maintenance schedules and requirements. Follow maintenance procedures given in the most <br />recent version of the Filterra' Operation and Maintenance Manual. <br />5. Maintenance: The required maintenance interval for stormwater treatment devices is often <br />dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, <br />Ecology does not endorse or recommend a "one size fits all" maintenance cycle for a <br />particular model/size of manufactured filter treatment device. <br />• Filterra' designs their systems for a target maintenance interval of 6 months. <br />Maintenance includes removing accumulated sediment and trash from the surface area of <br />the inedia, removing the mulch above the media, replacing the mulch, providing plant <br />health evaluation, and pruning the plant if deemed necessary. <br />• Conduct maintenance following manufacturer's guidelines. <br />6. FilterraCRII units come in standard sizes. <br />7. The minimum size filter surface -area for use in western Washington is determined by using <br />the sand filter module in the latest version of WWHM or other Ecology approved continuous <br />runoff model for western Washington. Model inputs include <br />a) Filter media depth: 1.8 feet <br />b) Effective Ponding Depth: 0.75 feet (This is equivalent to the 6-inch clear zone <br />between the top of the mulch and the bottom of the slab plus 3-inches of mulch.) <br />c) Side slopes: Vertical <br />d) Riser height: 0.70 feet <br />e) Filter Hydraulic Conductivity: Use the Hydraulic Conductivity as listed in the table <br />above (use the lowest applicable hydraulic conductivity depending on the level of <br />treatment required) under Ecology's Decision, above. <br />