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EFFECTIVE DATE: 2/1/2024 Wet Weather Checklist October 1 thru April 30 The following information is provided to assist applicants with the City of Redmond Wet Weather plan process. For detailed design criteria refer to the City of Redmond, Stormwater Technical Notebook, Chapter 7 – Wet Weather and Rainy Season Clearing / Grading, for guidance in assembling a Wet Weather Plan package. Wet Weather Annual Fee Rates technology surcharge will be applied in addition to the listed fee as authorized by Ordinance No. 2090, and extended permanently by Resolution No. 1162 on December 3, 2002. Fees established and adopted under Resolution No. 1364. Submittal Procedure Starting from July 1, 2022 the approved civil construction plan(s) under the issued SITE, Clear and Grade (CGP), or Rough Grade (RGD) permits should also include the approved Wet Weather Plan, in addition to the Dry Season TESC Plan, according to the updated 2022 Stormwater Technical Notebook in Chapter 7.4. During the Coordinated Civil Review (CCR), the applicant must contact their stormwater engineer to obtain a Wet Weather Plan (WWP) number. The proposed WWP will be reviewed as part of the CCR process. Upon CCR approval and if no changes were made to the proposed WWP after the CCR approval, the WWP shall be separated from the approved CCR set and sent to the City with applicable fees to obtain a WWP num- ber (if one has not been provided), and approval signatures. If there have been changes to the WWP following CCR approval, then the revised plans must be sent to the storm water reviewer for further review and approval. Changes to the Wet Weather Plan will require additional review from the Storm Water Engineer and may delay obtaining your WWP number/approval signatures depending on the extend of these changes. If the Site, CGP, or RGD permit have been issued without the approved WWP, you may submit your proposed WWP with applicable fees for review to the Storm Water Engineer. Upon submittal of the final approved Wet Weather Plan (separated from the CCR plan set if part of the ap- proved CCR or stand alone) and all Wet Weather fees have been paid, a Wet Weather Plan number shall be provided and the Wet Weather Plan signed by the Storm Water Engineer(s) following their review and approv- al. If included as part of the CCR and no changes made, then no further review will be required. For projects that have the WWP already included and reviewed as part of the CCR submittal, then only the Wet Weather Annual Inspection Fee is required. If the WWP has not been reviewed as part of the CCR, then a Wet Weather Plan Review Fee will also be required in addition to the Annual Inspection Fee. • Plans are reviewed on a first-come first-served basis. • During periods of heavy volume, space on the review schedule may not be available for the following week. Plan for delays in September and October. • The project contractor should attend at least the first meeting with the Storm Water Engineer reviewing the wet weather plans. ---PAGE BREAK--- Timetable for existing projects with previous CCR submittal without a Wet Weather Plan Projects active prior to October 1st: Provide a plan for review by mid-August. Projects to start construction after October 1st: Work will commence only upon Wet Weather Plan approval. Coordinate Wet Weather Plan with the construction drawings. Submittal Items Wet Weather Plan Package to the City of Redmond Development Engineering Division. The submittal should include the following: • When chemical treatment is proposed submit a Request for Chemical Treatment to Department of Ecology, which is available on their website at: • Construction Stormwater Pollution Prevention Plan Submit a copy that has been updated with the proposed BMP’s for the Wet Weather Plan. Keep a copy of the onsite at all times. • Stormwater Sampling Plan: including collection locations, frequency, analytical tests/procedures, reporting process, and the responsible independent third-party used to perform monitoring and related analytical work. Include pH test- ing to sampling plan once concrete work commences. • Chemical treatment shall only be a Department of Ecology GULD approved technology. • A Wet Weather Plan Showing required TESC BMPs and Seasonal Suspension Plan. Wet Weather TESC Standards Successful Wet Weather TESC will meet all of the following standards: • Site areas which do not need to be disturbed are not disturbed (clearing limits are defined and maintained). • Flows of runoff from areas not under construction are kept off the disturbed soils in the construction areas. • Disturbed soil in an area that is not being worked receives temporary cover/stabilization. • The turbidity in runoff from the construction area does not exceed 25 NTU. • Runoff from the construction area that reaches receiving waters does not cause the turbidity in the receiving waters to increase more than 5 NTU as a result of the project runoff. • Disturbed areas receive final, permanent cover in accordance with the approved project plans, without unnecessary delay. • Off-site streets are kept free of dirt and mud originating from the construction site. (Using sweeping, not flushing, in the streets and, if appropriate, on-site wheel wash facilities). • Dust is controlled and is in compliance with the Puget Sound Clean Air Agency. • Contingency plans for controlling spills and other potential pollutants have been developed and are ready to imple- ment at the construction site. • Work in Critical Areas conforms to requirements of the City’s Critical Areas Ordinance (CAO). See Redmond Zoning Code 21.64 for additional information and definitions regarding Critical Areas. • 24-hour, 7-day-per-week, point(s) of contact is/are designated who can call out and direct crews, obtain materials, and authorize immediate expenditures for on-site temporary erosion and sediment control (TESC) work. • Compliance exists with all project approval conditions and permits (including applicable non-City permits such as, but not limited to, the Hydraulics Project Approval from Washington State Department of Fish and Game and the Wash- ington Department of Ecology • Wet Weather Plans showing required TESC BMPs and Seasonal Suspension Plan for work during the rainy season will be applied only between October 1st through April 30th. ---PAGE BREAK--- Wet Weather Calculations • Chemical and electro-coagulation treatment systems must include storage of 150% of the 10-year storm runoff volume. • Acceptable methods of storage volume calculation: continuous simulation hydrologic model such as WWHM. • Do not deduct the volume potentially treated in a 24-hour period from the storage volume required. • Bench test results are required for all chemical and electro-coagulation system designs. • Using standard BMP or chemical treatment – maximum turbidity discharge: 25 NTU • All projects must submit copies of the SWPP Plan and NPDES application. • List the allowed maximum discharge rate from the project 10-year storm (current land use condition) for pump sizing. • Confirm that the open channel conveyance is not eroded. (If there is potential for erosion, the allowable release rate may be reduced) Wet Weather Construction Drawings to Include: • Half-size plan sheets (11-inch by 17-inch) • Seasonal Suspension Plan • Notes describing steps to shut down project for the rainy season if runoff criteria cannot be met. • Wet Weather Approval Block on each page. • Clearly labeled Plan Number. • Title Block clearly labeled WET WEATHER PLAN and wet weather years. • Disturbed areas delineated: • Specify amount of disturbed area in acres. When applicable, show phasing on plans. • The status of construction: identify completed work as of the date of plan submittal. • Show work to be accomplished during the rainy season. • Label land use/vegetation of areas to remain undisturbed. • Legend covering all wet weather symbols appearing on the drawing. • Discharge water turbidity limits allowed. • Sampling/Monitoring points as presented in the sampling plan. • Delineate sensitive areas and their buffers (ex. steep slopes, wetlands, streams, etc.). When the Wet Weather Plan proposes to use storm detention ponds, tanks or vaults built as part of the project as holding basins or settlement basins: • Plug the discharge pipe. • Gravity flow from these structures is not permitted during the rainy season. • This will prevent turbid water from leaving the site. • Provide a pumped discharge that will be attended during operation. • The pump operator must be familiar with the pH and turbidity discharge limits from the site. • When pumps are proposed, provide pump type, capacity, power source, and back-up power source. • Delineate the drainage basin contributing to each sediment pond and/or sediment trap. • Confirm that proposed erosion control BMP placement does not conflict with construction work. • Show location of wheel wash. Wheel wash per City of Redmond Detail 503A, or as approved by City of Redmond ---PAGE BREAK--- Inspector. • Address pH adjustment process following concrete placement. • Show contour and spot elevation information sufficient to verify collection and transport to proposed treatment system. • Indicate the hierarchy of BMPs to be followed to ensure the performance specification is met. Add contact name and 24-hour telephone number for the project CESCL or other person responsible for erosion control. Plans shall be stamped by a professional engineer registered in the State of Washington. Under special cir- cumstances, where the plan does not include engineering design, the Wet Weather Committee may waive the requirement for a PE stamp. Include a secondary (back-up) treatment BMP Required if primary treatment BMP is determined to be insufficient by the Wet Weather Committee. For projects proposing chemical treatment include the following in the SWPP Plan (BMP C250) • Method of treatment • Treatment process including dosing rates • Method of pH adjustment • Method of testing for residual chemical following treatment • Document Department of Ecology GULD approval for construction treatment Trucking Some applicants have proposed trucking turbid stormwater as a primary or secondary BMP. Hauling turbid water for off-site disposal is generally discouraged because it is an inter-basin transfer. However, hauling may be considered where alternative BMPs are not available or effective. To be considered as a Wet Weather Plan BMP a Haul Plan is re- quired. The Haul Plan shall include the following: • Documentation showing the number of trucks and drivers available to transfer the 10- year 24-hour storm run- off volume. These resources must be available at all time for use on the subject project. • Provide copy of contract with trucking company if outside resources are proposed. Contract must specify duration of agreement, haul volume per trip and trips per day. Must specify capacity of each truck type and number of trained drivers available for the contract peri- od. • Specify the discharge location, provide the name and address of the receiving site. • Include the discharge facility’s Department of Ecology - Stormwater Discharge Permit number. In some cases, this may be a Stormwater Use Permit. Restoration Bonds Restoration bond amount will be set by the Wet Weather Committee. If required, bond will be required prior to commenc- ing work. Bonds may be released once site stabilization has been verified by the City of Redmond Inspector or the rainy sea- son ends. For stabilization by establishing vegetative cover, at least 90% of the disturbed area shall have a stand of grass or other approved plant at least 4 inches high. Updated 2/1/2024