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Home My WebLink About2026-1 Blanket Adjustment - R-Tank Date: April 23rd, 2026 To: Nathan Janders, Development Engineering Manager From: Joe Farah, Surface Water Utility Engineering Manager Subject: Blanket Adjustment | R-Tank® Stormwater Modules The City of Renton Water Utility Department has issued a blanket adjustment allowing private developments to use the R-Tank system on private property to provide flow control, in accordance with the City adopted 2022 Renton Surface Water Design Manual provided that the following conditions are met: 1. The R-Tank® modules are to be used only on commercial, industrial, or residential site developments where the system will be located within private property. The property owner is responsible for maintenance and operation of the R-Tank® system. 2. The R-Tank® facility shall not be located within the City right-of-way or any easements or tract dedicated to the City. 3. All tank access openings shall be readily accessible by maintenance vehicles. 4. Any maintenance worker that enters the R-Tank® system shall possess a current OSHA Confined Space Entry Certificate. 5. The owner must follow the R-Tank® Operation, Inspection, and Maintenance Guidelines provided by Ferguson Waterworks (See attached Exhibit). 6. The applicant will need to submit a Declaration of Covenant for inspection and maintenance of the R-Tank flow control facility. The Drainage Covenant can be found on the City’s website. A site plan showing the location of the flow control facility must be included as Exhibit A in the declaration of covenant. 7. The approval of this adjustment does not relieve the applicant from other city, state, or federal requirements. Please notify the applicant of our approval of the adjustment request and associated conditions related to the approval listed above. If you have any questions about this adjustment, please contact me or Kevin Evans. Sincerely, Joseph Farah, PE Surface Water Utility Engineering Manager cc: Ron Straka, PE, Utility Systems Director Justin Johnson, PE, Development Engineering Director Kevin Evans, PE, Surface Water Utility Engineer Nathan Nelson, surface water/wastewater/ special projects maintenance manager R-TANK® OPERATION, INSPECTION AND MAINTENANCE STORMWATER MANAGEMENT Rev: 11/02/2022 Operation Your R-Tank System has been designed to function in conjunction with the engineered drainage system on your site, the existing municipal infrastructure, and/or the existing soils and geography of the receiving watershed. Unless your site included certain unique and rare features, the operation of your R-Tank System will be driven by naturally occurring systems and will function autonomously. However, upholding a proper schedule of Inspection & Maintenance is critical to ensuring continued functionality and optimum performance of the system. Inspection Both the R-Tank and all stormwater pre-treatment features incorporated into your site must be inspected regularly. Inspections should be done every six months for the first year of operation, and at least yearly thereafter. Inspections may be required more frequently for pre-treatment systems. You should refer to the manufacturer requirements for the proper inspection schedule. With the right equipment most inspections and measurements can be accomplished from the surface without physically entering any confined spaces. If your inspection does require confined space entry, you must follow all local, regional, and OSHA requirements. All maintenance features of your system can be accessed through a covering at the surface. With the lid removed, you can visually inspect each component to identify sediment, trash, and other contaminants within the structure. Check you construction plans to identify the maintenance features engineered into your R-Tank system, which may include: Upstream Pipes, Inlets, and Manholes  Working from the structures adjacent the R-Tank toward those farther away, check for debris and sediment in both the structures and the pipes. Be sure to Include all structures that contain pre- treatment systems. Some structures may include a sump. Maintenance Ports  Located near the inlet and outlet connections and throughout the system, check sediment depth at each port. Rev: 11/02/2022 Inspection Ports Less common, inspection ports are primarily located within the Treatment Row of an R-Tank System. These should be used to check for sediment deposits but are typically too small to access for backflushing. Treatment Row On installations in 2018 or later, inlet pipes may connect to a row of modules with 12” diameter access holes running horizontally through the module that can be jet vacuumed. Check these rows for accumulation of sediment and debris. All observations and measurements should be recorded on an Inspection Log kept on file. We’ve included a form you can use at the end of this guide. Maintenance For modules taller than 40” the R-Tank System should be back-flushed once sediment accumulation has reached 6”. For modules less than 40” tall, perform maintenance when sediment depths are greater than 15% of the total system height. If your system includes a Treatment Row with linear access through the modules from the inlet pipe, backflush this area when sediment depths reach 6”. BEFORE ANY MAINTENANCE IS PERFORMED ON YOUR SYSTEM - PLUG THE OUTLET PIPE TO PREVENT CONTAMINATION OF THE DOWNSTREAM SYSTEMS. Begin by cleaning all upstream structures, pipes, and pre-treatment systems containing sediment and/ or debris. If your system includes a Treatment Row, this portion of the system should be cleaned with traditional jet-vac equipment. Add a centralizer to the jet for easiest access through the modules. To back-flush the R-Tank, water is pumped into the system through the Maintenance Ports as rapidly as possible. The turbulent action of the water moving through the R-Tank will suspend sediments which may then be pumped out. If your system includes an Outlet Structure, this will be the ideal location to pump contaminated water out of the system. However, removal of back-flush water may be accomplished through the Maintenance Ports, as well. For systems with large footprints that would require extensive volumes of water to properly flush the system, you should consider performing your maintenance within 24 hours of a rain event. Stormwater entering the system will aid in the suspension of sediments and reduce the volume of water required to properly flush the system. STEP BY STEP INSTRUCTIONS FOR INSPECTION AND MAINTENANCE CAN BE FOUND ON THE NEXT PAGE, WITH A MAINTENANCE LOG ON THE LAST PAGE. Rev: 11/02/2022 INSPECTION 1.Upstream Structures a.Remove cover b.Use flashlight to detect sediment deposits If present, measure sediment depth c.Inspect pipes connecting to R-Tank i.If inlet pipes connect to Treatment Row, check sediment depth within these modules ii.If access for measurement inside the Treatment Row is difficult, sediment depth can be estimated based on the coverage of the round, 12” opening of the module d.Inspect pre-treatment systems (if present) e.Record results on Maintenance Log f.Replace cover g.Repeat for ALL Manholes upstream of R-Tank until no sedimentation is observed and all pre- treatment systems have been checked 2.Maintenance Ports a.Remove cap b.Use flashlight to detect sediment deposits c.If present, measure sediment depth with stadia rod d.Record results on maintenance log e.Replace cap f.Repeat for ALL Maintenance Ports 3.Inspection Port a.Remove cap b.Use flashlight to detect sediment deposits c.If present, measure sediment depth with stadia rod d.Record results on Maintenance Log e.Replace cap MAINTENANCE 1.Plug system outlet to prevent discharge of back-flush water 2.Vacuum all upstream structures, inlet pipes, and stormwater pre-treatment systems 3.If a Treatment Row is present, vacuum this row of modules 4.Determine best location to pump out back-flush water. Typically, the outlet structure will work best, but sometimes the Maintenance Ports must be used. 5.Remove cap from Maintenance Port and pump water as rapidly as possible into system through port to suspend sediments, pumping dirty water out of the system from the outlet or nearby Maintenance Port 6.Repeat at all Maintenance Ports until sediment levels are reduced to a satisfactory level 7.Sediment-laden water shall be disposed of per local regulations 8.Replace any remaining caps or covers and remove outlet plug 9.Record the back-flushing event in your Maintenance Log with any relevant specifics Rev: 11/02/2022 R-Tank® Maintenance Log Site Name: Company: Location: Contact: City and State: Phone: System Owner: Email: Date Location Sediment Depth Observations / Notes Initials