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22-103898-SWPPP-9-6-22 Construction Stormwater General Permit Stormwater Pollution Prevention Plan (SWPPP) for Beehive Food Truck Park Prepared for: The Washington State Department of Ecology Northwest Region Permittee / Owner Developer Operator / Contractor Special Edition of America 6612 NE 1st St Renton, WA 98059 Quyen Phan Vinason Pho TBD Kent, WA Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Dean A. Furr, P.E., CESCL Furr Engineering, PLLC 206.890.8291 SWPPP Preparation Date Mar. 9, 2022 Project Construction Dates Activity / Phase Start Date End Date All phases 5/1/2023 10/1/2023 P a g e | 1 Table of Contents 1 Project Information ...............................................................................................................5 1.1 Existing Conditions .......................................................................................................5 1.2 Proposed Construction Activities ...................................................................................6 2 Construction Stormwater Best Management Practices (BMPs) ............................................7 2.1 The 13 Elements ...........................................................................................................7 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits .........................................7 2.1.2 Element 2: Establish Construction Access .............................................................7 2.1.3 Element 3: Control Flow Rates...............................................................................7 2.1.4 Element 4: Install Sediment Controls .....................................................................9 2.1.5 Element 5: Stabilize Soils.......................................................................................9 2.1.6 Element 6: Protect Slopes......................................................................................9 2.1.7 Element 7: Protect Drain Inlets.............................................................................11 2.1.8 Element 8: Stabilize Channels and Outlets ..........................................................11 2.1.9 Element 9: Control Pollutants ...............................................................................11 2.1.10 Element 10: Control Dewatering ..........................................................................13 2.1.11 Element 11: Maintain BMPs .................................................................................14 2.1.12 Element 12: Manage the Project ..........................................................................14 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .................................17 3 Pollution Prevention Team .................................................................................................17 4 Monitoring and Sampling Requirements ............................................................................18 4.1 Site Inspection ............................................................................................................18 4.2 Stormwater Quality Sampling ......................................................................................18 4.2.1 Turbidity Sampling ...............................................................................................18 4.2.2 pH Sampling ........................................................................................................20 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .........................21 5.1 303(d) Listed Waterbodies ..........................................................................................21 5.2 TMDL Waterbodies .....................................................................................................21 6 Reporting and Record Keeping ..........................................................................................22 6.1 Record Keeping ..........................................................................................................22 6.1.1 Site Log Book ......................................................................................................22 6.1.2 Records Retention ...............................................................................................22 6.1.3 Updating the SWPPP ...........................................................................................22 6.2 Reporting ....................................................................................................................22 6.2.1 Discharge Monitoring Reports ..............................................................................22 6.2.2 Notification of Noncompliance ..............................................................................23 List of Tables Table 1 – Summary of Site Pollutant Constituents .................................................................6 Table 2 – Pollutants ................................................................................................................11 Table 3 – pH-Modifying Sources ............................................................................................12 Table 4 – Dewatering BMPs ....................................................................................................13 P a g e | 2 Table 5 – Management ............................................................................................................14 Table 6 – BMP Implementation Schedule ..............................................................................16 Table 7 – Team Information ....................................................................................................17 Table 8 – Turbidity Sampling Method ....................................................................................18 Table 9 – pH Sampling Method ..............................................................................................20 List of Appendices Appendix/Glossary A. P a g e | 3 Site Map B. BMP Details C. Correspondance D. Site Inspection Form E. Construction Stormwater General Permit F. 303 (d) List Water Bodies/TDML G. Contaminated Site Information H. Engineering Calculations P a g e | 4 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL Certified Erosion and Sediment Control Lead CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model P a g e | 5 1 Project Information Project/Site Name: Beehive Food Truck Park Street/Location: 30640 Pacific Hwy City: Federal Way State: WA Zip code: 98003 Subdivision: - Receiving waterbody: Steel Lake 1.1 Existing Conditions The site includes the parking lot associated with the commercial building at 30640 Pacific Hwy S in Federal Way, WA, and consists of a total area of 33,909 SF (0.78 acre) on parcel no. 0921049121. The northern portion of the site consists of a paved parking lot, and the southern portion of the site is a large, nearly-level area vegetated with grasses. The site is bordered to the north, east, and south by commercial properties, and to the west by Pacific Hwy S. The site soil consists of approximately 6 inches of grass and topsoil underlain by approximately 6 to 6.5 feet of loose- to medium-dense, silty-fine to medium-grained sand with gravel (weathered glacial till). Significant volumes of groundwater are not anticipated to be present at this site. Infiltration is not generally considered feasible on this project due to the large quantity of fill soils, which are of similar composition to native soils and have poor infiltration rates. The following table shows the existing conditions peak runoff rates from the site. Total acreage: 1.085 ac Disturbed acreage: 1.065 ac on-site and 0.019 ac off-site Existing structures: 0 ac Landscape topography: 0.689 ac (grass) Flat, 0% slope Drainage patterns: Collected by catch basins into existing stormwater system Existing Vegetation: grass Critical Areas: N/A List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: N/A Table 1 includes a list of suspected and/or known contaminants associated with the construction activity. List all known or suspected contaminants associated with this site in Table 1. Include contaminants previously remediated. There are no known contaminents within the soil at this location. P a g e | 6 Table 1 – Summary of Site Pollutant Constituents 1.2 Proposed Construction Activities The proposed project will replace and expand the existing parking lot onsite, to be used as as area for food trucks. Utilities similar to those at RV/trailer campsites (water, sewer, etc.) will also be added. Site vegetation will consist of urban landscaping. The following table shows the area breakdown of the developed site: PROPOSED ON-SITE DEVELOPED sf ac DISTURBED AREA 46,394 1.065 IMPERVIOUS 37,455 0.860 PERVIOUS PAVERS/CURB/TRASH 32,788 0.753 CONCRETE SIDEWALK 1,611 0.037 POND/WALLS 3,056 0.070 PERVIOUS (LS) 8,939 0.205 PROP. OFF-SITE DEVELOPMENT sf ac DISTURBED AREA 819 0.019 IMPERVIOUS 461 0.011 DRIVEWAY/RAMP 461 0.011 PERVIOUS (LS) 358 0.008 Table 1: Developed Conditions Area Breakdown Constituent (Pollutant) Location Depth Concentration P a g e | 7 2 Construction Stormwater Best Management Practices (BMPs) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e., hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. 2.1 The 13 Elements 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits The site will be delineated by high visability silt fence along the south, west, and east property lines. No equipment, chemicals, soil deposits or construction materials shall be placed within the protective barriers. Any landscaping activities subsequent to the removal of the barriers shall be accomplished with light machinery or hand labor. List and describe BMPs: BMP C101: Preserving Natural Vegetation BMP C103: High Visibility Plastic or Metal Fence BMP C233: Silt Fence Installation Schedules: once prior to construction Inspection and Maintenance plan: Weekly and daily during storm events Responsible Staff: TBD 2.1.2 Element 2: Establish Construction Access The existing driveway will be utilized to the maximum extent possible during demolition, excavation phases. Street washing is permitted, even after shoveling or sweeping. During construction, if material is being deposited on off-site streets, consider implementing the following: 1. Regenerative-type vacuum sweepers and repeated or continuous sweeping. 2. Wheel wash (or an improved wheel wash if one already exists). 3. Special site procedures and provisions (such as transferring haul-outs to trucks that travel only on paved and maintained surfaces in the site). 4. Suspension of work until dry weather. List and describe BMPs: BMP C105: Stabilized Construction Entrance / Exit. Installed per Plan Inspection and Maintenance plan: Weekly It will be the responsibility to clean all roadway surfaces using regenerative vacuum sweepers. Installation Schedules: once prior to the removal of the existing gravel driveway. Responsible Staff: TBD 2.1.3 Element 3: Control Flow Rates Will you construct stormwater retention and/or detention facilities? Yes No Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? P a g e | 8 Yes No List and describe BMPs: A sediment trap may be constructed to acontrol runoff if necessary. Interceptor swales may be constructed to intercept runoff onto 308th. BMP C240: Sediment Trap BMP C200: Interceptor Swale BMP Installation Schedules: Once at the beginning of the project. Inspection and Maintenance plan: Weekly and after every storm event. Sediment shall be removed when it reaches 1ft above the bottom. Responsible Staff: TBD P a g e | 9 2.1.4 Element 4: Install Sediment Controls Silt fence will be installed along the property line/clearing limits to prevent turbid runoff into the existing storm system. A sediment trap may be constructed to store sediment. List and describe BMPs: BMP C233: Silt Fence BMP C240: Sediment Trap Installation Schedules: once prior to construction activities Inspection and Maintenance plan: Weekly and daily during storm events Responsible Staff: TBD 2.1.5 Element 5: Stabilize Soils All unworked exposed soil will be covered by mulching, plastic covering or permanently vegetated. It is the intent to have all hardscape constructed early in the project. West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: 5/1/2022 End date: 10/1/2023 Will you construct during the wet season? Yes No Construction is not anticipated during the wet season. All proposed hardscaps will be constructed prior to the wet season and all landscaping will be planted and mulched. List and describe BMPs: BMP C121: Mulching BMP C125: Topsoiling/Composting - as a requirement to provide on-site stormwater management to implement BMP T5.13: Post Construction Soil Quality and Depth - Installed per plan BMP C123: Plastic Covering to be used on stockpiles and cut slopes BMP C150: Materials on Hand - in the event that additional TESC materials are necessary during emergency situations. Installation Schedules: As soon as soils get exposed Inspection and Maintenance plan: Weekly and daily during storm events Responsible Staff: TBD 2.1.6 Element 6: Protect Slopes The off-site slopes are currently stabilized. There are no significant slopes onsite. P a g e | 10 Will steep slopes be present at the site during construction? Yes No List and describe BMPs: BMP C120: Temporary and Permanent Seeding BMP C121: Mulching BMP C123: Plastic Covering to be used on stockpiles and cut slopes Installation Schedules: when filling site Inspection and Maintenance plan: Daily Responsible Staff: TBD P a g e | 11 2.1.7 Element 7: Protect Drain Inlets All off-site catchbasins adjacent to the project will be fitted with inlet protection. If on-site catchbasins and yard basins are constructed prior to site stabilization, they shall be fitted with inlet protection as well. List and describe BMPs: BMP C220 Inlet Protection Installation Schedules: Once prior to construction activities Inspection and Maintenance plan: Weekly and during storm events. Sediment buildup must be removed when the device is filled by one third (1/3). Responsible Staff: TBD 2.1.8 Element 8: Stabilize Channels and Outlets There are no channels or outlets to be stabilized Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems. List and describe BMPs: NA Installation Schedules: Inspection and Maintenance plan: Responsible Staff: 2.1.9 Element 9: Control Pollutants The following pollutants are anticipated to be present on-site: Table 2 – Pollutants Pollutant (List pollutants and source, if applicable) concrete from retaining walls, driveway, curbs Asphalt All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. If required, BMPs to be implemented to control specific sources of pollutants are discussed below. List and describe BMPs: BMP C151: Concrete Handling BMP C152: Saw cutting and Surfacing Pollution Prevention BMP C153: Material Delivery, Storage and containment Installation Schedules: Prior to construction and during foundation and driveway construction Inspection and Maintenance plan: Weekly and during storm events Responsible Staff: TBD P a g e | 12 Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No List and describe BMPs: Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Will wheel wash or tire bath system BMPs be used during construction? Yes No If yes, provide disposal methods for wastewater generated by BMPs. If discharging to the sanitary sewer, include the approval letter from your local sewer district under Correspondence in Appendix C. List and describe BMPs: Installation Schedules: Inspection and Maintenance plan: Responsible Staff: Will pH-modifying sources be present on-site? Yes No If yes, check the source(s). Table 3 – pH-Modifying Sources None Bulk cement Cement kiln dust Fly ash Other cementitious materials New concrete washing or curing waters Waste streams generated from concrete grinding and sawing Exposed aggregate processes Dewatering concrete vaults Concrete pumping and mixer washout waters Recycled concrete Recycled concrete stockpiles Other (i.e., calcium lignosulfate) [please describe: ] Construction concrete washout is planned to be done onsite using an eco-pan type system. On a weekly basis the eco pans will be disposed of offsite at an approved facility. List and describe BMPs: BMP C151: Concrete Handling BMP C152: Saw cutting and Surfacing Pollution Prevention BMP C153: Material Delivery, Storage and containment Installation Schedules: Throughout the project Inspection and Maintenance plan: Inspection and Maintenance plan: Inspect weekly and dispose of eco pans weekly or more frequently. Dispose to an approved facility Responsible Staff: TBD Adjust pH of stormwater if outside the range of 6.5 to 8.5 su. Obtain written approval from Ecology before using chemical treatment with the exception of CO2 or dry ice to modify pH. P a g e | 13 Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. Will uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters? Yes No If yes, provide BMPs to contain the wastewater during infiltration. Prior to infiltration, water from water- only based shaft drilling that comes into contact with curing concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su). List and describe BMPs: Installation Schedules: Inspection and Maintenance plan: Responsible Staff: TBD 2.1.10 Element 10: Control Dewatering Dewatering is not anticipated for a project this size. Check treatment of disposal option for dewatering water, if applicable: Table 4 – Dewatering BMPs Infiltration Transport off-site in a vehicle (vacuum truck for legal disposal) Ecology-approved on-site chemical treatment or other suitable treatment technologies Sanitary or combined sewer discharge with local sewer district approval (last resort) Use of sedimentation bag with discharge to ditch or swale (small volumes of localized dewatering) List and describe BMPs: Installation Schedules: Inspection and Maintenance plan: Responsible Staff: P a g e | 14 2.1.11 Element 11: Maintain BMPs All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed and the facility shall be returned to conditions specified in the construction documents. 2.1.12 Element 12: Manage the Project The project will be managed based on the following principles: • Projects will be phased to the maximum extent practicable and seasonal work limitations will be taken into account. • Inspection and monitoring: o Inspection, maintenance and repair of all BMPs will occur as needed to ensure performance of their intended function. o Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s) are located in accordance with applicable requirements of the CSWGP. • Maintain an updated SWPPP. o The SWPPP will be updated, maintained, and implemented in accordance with Special Conditions S3, S4, and S9 of the CSWGP. As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The SWPPP will be reviewed monthly to ensure the content is current. Check all the management BMPs that apply at your site: Table 5 – Management Design the project to fit the existing topography, soils, and drainage patterns Emphasize erosion control rather than sediment control Minimize the extent and duration of the area exposed Keep runoff velocities low Retain sediment on-site Thoroughly monitor site and maintain all ESC measures P a g e | 15 Schedule major earthwork during the dry season Other (please describe) P a g e | 16 Table 6 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season PHASE 1 Pre construction Silt Fence, Construction Entrance, High Visibility Fence, Interceptor Swales and sediment trap 5/1/2023 Dry Demolition Dust Control to include sprinkling water on soil and vacuum or wet sweep fine dirt and skid control materials from paved roads soon after rain events or when needed. 5/14/2023 Dry Site Grading utility trenching Maintain installed BMPS and Dust Control 6/1/2023 Dry VAULT/POND BMP C153: Material Delivery, Storage and containment 6/14/2023 Dry Retaining Wall BMP C151: Concrete Handling, BMP C152: Saw cutting and Surfacing Pollution Prevention, BMP C153: Material Delivery, Storage and containment 7/1/2023 Dry Ballast and Paver construction BMP C151: Concrete Handling, BMP C152: Saw cutting and Surfacing Pollution Prevention, BMP C153: Material Delivery, Storage and containment 8/1/2023 Dry Landscaping BMP C120: Temporary and Permanent Seeding BMP C125: Topsoiling/Composting - as a requirement to provide on-site stormwater management to implement BMP T5.13: Post Construction Soil Quality and Depth - Installed per plan BMP C150: Materials on Hand - in the event that additional TESC materials are necessary during emergency situations. 10/1/2023 Wet Project Complete 10/01/2023 WET P a g e | 17 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs LID is not implemented on the site due to the poor soils. 3 Pollution Prevention Team Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD TBD Resident Engineer Dean A. Furr, P.E., CESCL 206.890.8291 Emergency Ecology Contact Report A Spill 425.649.7000 Emergency Permittee/ Owner Contact TBD 206.391.3311 Non-Emergency Owner Contact Wayne Seminoff 206.391.3311 Monitoring Personnel TBD 206.391.3311 Ecology Regional Office Northwest Regional Office 425.649.7000 P a g e | 18 4 Monitoring and Sampling Requirements Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Stormwater sampling data Create your own Site Inspection Form or use the Construction Stormwater Site Inspection Form found on Ecology’s website. http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html File a blank form under Appendix D. The site log book must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. 4.1 Site Inspection Site inspections will be conducted at least once every calendar week and within 24 hours following any discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is reduced to once per calendar month. The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. 4.2 Stormwater Quality Sampling 4.2.1 Turbidity Sampling Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Check the analysis method you will use: Table 8 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than 33 centimeters. If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. P a g e | 19 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. • Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/CRO_nerts_online.html • Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/ERO_nerts_online.html • Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/NWRO_nerts_online.html • Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 or http://www.ecy.wa.gov/programs/spills/forms/nerts_online/SWRO_nerts_online.html 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period 3. Document BMP implementation and maintenance in the site log book. 4. Continue to sample discharges daily until one of the following is true: • Turbidity is 25 NTU (or lower). • Transparency is 33 cm (or greater). • Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater • The discharge stops or is eliminated. P a g e | 20 4.2.2 pH Sampling pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured concrete over the life of the project). The use of recycled concrete or engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled concrete are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1. Prevent high pH water from entering storm sewer systems or surface water. 2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: Check the analysis method you will use: Table 9 – pH Sampling Method pH meter pH test kit Wide range pH indicator paper P a g e | 21 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies 5.1 303(d) Listed Waterbodies Circle the applicable answer, if necessary: Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No List the impairment(s): If yes, discharges must comply with applicable effluent limitations in S8.C and S8.D of the CSWGP. 5.2 TMDL Waterbodies Waste Load Allocation for CWSGP discharges: Describe the method(s) for TMDL compliance: List and describe BMPs: Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water Body form is included in Appendix F. P a g e | 22 6 Reporting and Record Keeping 6.1 Record Keeping This section does not need to be filled out. It is a list of reminders for the permittee. 6.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Sample logs 6.1.2 Records Retention Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: • CSWGP • Permit Coverage Letter • SWPPP • Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. 6.1.3 Updating the SWPPP The SWPPP will be modified if: • Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. • There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. 6.2 Reporting 6.2.1 Discharge Monitoring Reports P a g e | 23 Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR due date is fifteen (15) days following the end of each calendar month. DMRs will be reported online through Ecology’s WQWebDMR System. To sign up for WQWebDMR go to: http://www.ecy.wa.gov/programs/wq/permits/paris/webdmr.html 6.2.2 Notification of Noncompliance If any of the terms and conditions of the permit is not met, and the resulting noncompliance may cause a threat to human health or the environment, the following actions will be taken: 1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable Regional office ERTS phone number (Regional office numbers listed below). 2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. Specific information to be included in the noncompliance report is found in Special Condition S5.F.3 of the CSWGP. Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by Special Condition S5.A of the CSWGP. • Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County Include the following information: 1. Your name and / Phone number 2. Permit number 3. City / County of project 4. Sample results 5. Date / Time of call 6. Date / Time of sample 7. Project name In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water. P a g e | 24 Appendix/Glossary P a g e | 25 Site Map OHEOHEOHEOHEOHEOHEOHEOHEOHEOHEOHESD XXOHPUGE 39.5'23.8'30.4'0.3'10.2' 0.5'19.7'14.6'14.5'0.5' 190.9'48.9'10.1'0.3'40.5'23.9'23.8'19.5'23.8'40.5' ONE STORYOFFICE BUILDING RH = 491.0' FF = 476.6' CONTAINERS ROOFOVERHANG (TYP.) OVERHEADBEAM (TYP.) SHEDSTEM WALL (TYP.)SSSSSSSSSSSSSSSSSSSSSSSSSDSDSDSDSDSDSDBUS STOP WOOD PLATFORM DS24PI16 DS6EVLT EX SSMH RIM = 478.37' INV N-S = 468.21' SDMHRIM = 479.97' SDMH RIM = 478.70' SDMH RIM = 477.28' CBRIM = 477.02' INV W 12" RCP= 473.82' CB RIM = 478.51' INV W 12" RCP = 475.09' CB RIM = 475.67' INV E 6" RCP = 473.67' CB RIM = 474.82' INV W 6" RCP = 472.62' INV E 12" RCP = 472.62' CB RIM = 474.26'INV W 12" RCP = 469.86' INV S 12" RCP = 469.86' INV N 12" RCP = 469.86' CB RIM = 475.71' UNABLE TO OPEN CB RIM = 474.21'INV W 6" CPEP = 471.71' INV S 12" DI = 471.71'INV E 12" RCP = 471.71' SDMH RIM = 474.38' INV N 36" CMP = 472.15' 475 474 475 476 476 476 475476475 475 476477 477 478479480 480 479478477 478477475476 47547647 6 R=5730.00'(PACIFIC HIGHWAY S)STATE HIGHWAY NO. 1PARCE L N O. 092104 - 9 1 2 0 PARCE L N O . 092104 - 9 1 4 9 PARCE L N O . 09210 4 - 9 2 1 9 S 308TH STREET 178.70'UTILITY EASEMENT AFN: 20090903001420W W W W W W WWWWWWWWWWW W W12" DI8" CONC8" DIN89°50'17"W 251.06' 62.0' 62' 476 CB RIM = 479.80' INV W 12" RCP = 476.40' MEDIAN CURB 476 475 X X X X X X X X X X X X X X X X X X X X XXXXXXXXXXXXXXXXXXX>>>>>>>>>>>>>>>>>>>>>>>>>>>> TBR TBR TYP NR Know what's below. Call before you dig. TOPOGRAPHY, BOUNDARY, AND UTILITIES STATEMENT: FURR ENGINEERING SERVICES PLLC. DOES NOT WARRANT THE TOPOGRAPHY, BOUNDARY, AND/OR EXISTING UTILITIES SHOWN ON THESE PLANS. IT IS THE CONTRACTORS' RESPONSIBILITY TO HAVE ALL EXISTING IMPROVEMENTS FIELD VERIFIED PRIOR TO CONSTRUCTION. ANY SUBSURFACE EXPLORATION OF EXISTING UNDERGROUND UTILITIES (POWER, WATER, SEWER, TELECOM, ETC.) SHALL BE PERFORMED BY THE CONTRACTOR. DISCREPANCIES BETWEEN WHAT IS SHOWN ON THE PLANS AND LOCATED BY THE CONTRACTOR SHALL BE BROUGHT TO THE ATTENTION OF FURR ENGINEERING SERVICES PLLC.. PRIOR TO CONSTRUCTION ACTIVITIES. TJW TESC PLAN C2.0 DAF DAF 21097 July 1, 2022 ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 NE 1/4 OF THE NE 1/4 OF SEC. 06, T. 20N., R. 04 E, W.M.BEEHIVE FOOD PARK 7/1/2022RGG N A FU R SEF ORP I ANO EL T S GE SI N ERED EEATDSNTA WFO . SAHI I N REENOTR46937 EX CB NOT SHOWN XX1 8 2 >> TBR EXISTING TO REMAIN CONSTRUCTION NOTES FLAG CLEARING LIMITS TO EXTENTS SHOWN ON THE PLAN. HIGH VISIBILITY SILT FENCE PER DETAIL ON SHEET C2.1 USE EXISTING DRIVEWAY AS CONSTRUCTION ENTRANCE DURING INITIAL SITE SETUP STABILIZED CONSTRUCTION ENTRANCE PER DETAIL ON SHEET C2.1 COVERED STOCK PILE PER DETAIL ON SHEET C2.1 CATCH BASIN INSERT PER DETAIL ON SHEET C2.1 REMOVE EXIST STRUCTURE SAWCUT FULL DEPTH REMOVE EXISTING STORM DRAINAGE SEDIMENT TRAP PER DETAIL ON SHEET C2.1 INTERCEPTOR SWALE WITH ROCK CHECK DAMS PER DETAILS ON SHEET C2.1 1 2 3 4 5 6 7 8 9 10 11 1 2 1 2 4 3 5 6 6 6 88 8 8 7 7 9 9 9 10 11 11 11 CONSTRUCTION SEQUENCE 1. BEFORE ANY CONSTRUCTION OR DEVELOPMENT ACTIVITY, A PRECONSTRUCTION MEETING MUST BE HELD BETWEEN THE CITY OF FEDERAL WAY, THE APPLICANT AND APPLICANT’S CONSTRUCTION REPRESENTATIVE. 2. FLAG CLEARING LIMITS. 3. INSTALL STABILIZED CONSTRUCTION ENTRANCE. 4. INSTALL FILTER FABRIC FENCE AS INDICATED ON PLAN. 5. INSTALL OFFSITE CATCH BASIN PROTECTION. 6. CONSTRUCT SEDIMENT TRAP/POND. 7. CLEAR AND GRUB AREAS OF THE SITE TO BE ROUGH GRADED OR FILLED. 8. INSTALL INTERCEPTOR SWALES/BERMS AND CHECK DAMS. 9. ROUGH GRADE SITE AND INSTALL STORM CONVEYANCE SYSTEM AND RETENTION/DETENTION FACILITIES. PROVIDE INLET PROTECTION WHERE INDICATED. 10. INSTALL REMAINING UTILITIES. 11. FINISH GRADE SITE AND CONSTRUCT ASPHALT PARKING AREAS, ACCESS DRIVES, SIDEWALKS, CURBS AND GUTTERS. 12. COMPLETE SITE STABILIZATION IN ACCORDANCE WITH LANDSCAPE PLANS. 13. CLEAN STORM DRAINAGE SYSTEM, ON AND OFF SITE, OF ALL SEDIMENT AND DEBRIS. 14. REMOVE TEMPORARY EROSION CONTROL FACILITIES WHEN SITE IS COMPLETELY STABILIZED. TESC LEGEND CLEARING LIMITS SILT FENCE TEMP CONSTRUCTION ENTRANCE SAWCUT LINE CATCH BASIN INSERT ASPHALT/CONCRETE TO BE REMOVED TEMPORARY STOCK PILE INTERCEPTOR SWALE WITH ROCK CHECK DAM TO BE REMOVED SEDIMENT TRAP PLUG WEST HOLE R Know what's below. Call before you dig. TOPOGRAPHY, BOUNDARY, AND UTILITIES STATEMENT: FURR ENGINEERING SERVICES PLLC. DOES NOT WARRANT THE TOPOGRAPHY, BOUNDARY, AND/OR EXISTING UTILITIES SHOWN ON THESE PLANS. IT IS THE CONTRACTORS' RESPONSIBILITY TO HAVE ALL EXISTING IMPROVEMENTS FIELD VERIFIED PRIOR TO CONSTRUCTION. ANY SUBSURFACE EXPLORATION OF EXISTING UNDERGROUND UTILITIES (POWER, WATER, SEWER, TELECOM, ETC.) SHALL BE PERFORMED BY THE CONTRACTOR. DISCREPANCIES BETWEEN WHAT IS SHOWN ON THE PLANS AND LOCATED BY THE CONTRACTOR SHALL BE BROUGHT TO THE ATTENTION OF FURR ENGINEERING SERVICES PLLC.. PRIOR TO CONSTRUCTION ACTIVITIES. TJW TESC NOTES AND DETAILS C2.1 DAF DAF 21097 July 1, 2022 ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 NE 1/4 OF THE NE 1/4 OF SEC. 06, T. 20N., R. 04 E, W.M.BEEHIVE FOOD PARK 7/1/2022RGG N A FU R SEF ORP I ANO EL T S GE SI N ERED EEATDSNTA WFO . SAHI I N REENOTR46937 EROSION CONTROL NOTES 1.APPROVAL OF THIS EROSION AND SEDIMENTATION CONTROL (ESC) PLAN DOES NOT CONSTITUTE AN APPROVAL OF PERMANENT ROAD OR DRAINAGE DESIGN (E.G., SIZE AND LOCATION OF ROADS, PIPES, RESTRICTORS, CHANNELS, RETENTION FACILITIES, UTILITIES, ETC.). 2. THE IMPLEMENTATION OF THESE ESC PLANS AND THE CONSTRUCTION, MAINTENANCE, REPLACEMENT, AND UPGRADING OF THESE ESC FACILITIES IS THE RESPONSIBILITY OF THE APPLICANT/ESC SUPERVISOR UNTIL ALL CONSTRUCTION IS APPROVED. 3. THE BOUNDARIES OF THE CLEARING LIMITS SHOWN ON THIS PLAN SHALL BE CLEARLY FLAGGED BY SURVEY TAPE OR FENCING, IF REQUIRED, PRIOR TO CONSTRUCTION (SWDM APPENDIX D). DURING THE CONSTRUCTION PERIOD, NO DISTURBANCE BEYOND THE CLEARING LIMITS SHALL BE PERMITTED. THE CLEARING LIMITS SHALL BE MAINTAINED BY THE APPLICANT/ESC SUPERVISOR FOR THE DURATION OF CONSTRUCTION. 4. THE ESC FACILITIES SHOWN ON THIS PLAN MUST BE CONSTRUCTED PRIOR TO OR IN CONJUNCTION WITH ALL CLEARING AND GRADING ACTIVITIES, AND IN SUCH A MANNER AS TO INSURE THAT SEDIMENT LADEN WATER DOES NOT ENTER THE DRAINAGE SYSTEM OR VIOLATE APPLICABLE WATER STANDARDS. 5. THE ESC FACILITIES SHOWN ON THIS PLAN ARE THE MINIMUM REQUIREMENTS FOR ANTICIPATED SITE CONDITIONS. DURING THE CONSTRUCTION PERIOD, THESE ESC FACILITIES SHALL BE UPGRADED (I.E. ADDITIONAL SUMPS, RELOCATION OF DITCHES AND SILT FENCES, ETC.) AS NEEDED FOR UNEXPECTED STORM EVENTS. 6. THE ESC FACILITIES SHALL BE INSPECTED DAILY BY THE APPLICANT/CONTRACTOR AND MAINTAINED AS NECESSARY TO ENSURE THEIR CONTINUED FUNCTIONING. 7. ANY AREA STRIPPED OF VEGETATION, INCLUDING ROADWAY EMBANKMENTS, WHERE NO FURTHER WORK IS ANTICIPATED OR A PERIOD OF 2 DAYS (WET SEASON) OR 7 DAYS (DRY SEASON), SHALL BE IMMEDIATELY STABILIZED WITH THE APPROVED ESC METHODS (I.E. SEEDING, MULCHING, NETTING, EROSION BLANKETS, ETC.) 8. ANY AREA NEEDING ESC MEASURES, NOT REQUIRING IMMEDIATE ATTENTION, SHALL BE ADDRESSED WITHIN 15 DAYS. 9. THE ESC FACILITIES ON INACTIVE SITES SHALL BE INSPECTED AND MAINTAINED A MINIMUM OF ONCE A MONTH OR WITHIN THE 24 HOURS FOLLOWING A STORM EVENT. 10. AT NO TIME SHALL MORE THAN ONE FOOT OF SEDIMENT BE ALLOWED TO ACCUMULATE WITHIN A CATCH BASIN. ALL CATCH BASINS AND CONVEYANCE LINES SHALL BE CLEANED PRIOR TO PAVING. THE CLEANING OPERATION SHALL NOT FLUSH SEDIMENT-LADEN WATER INTO THE DOWNSTREAM SYSTEM. 11. STABILIZED CONSTRUCTION ENTRANCES AND WASH PADS SHALL BE INSTALLED AT THE BEGINNING OF CONSTRUCTION AND MAINTAINED FOR THE DURATION OF THE PROJECT. ADDITIONAL MEASURES MAY BE REQUIRED TO INSURE THAT ALL PAVED AREAS ARE KEPT CLEAN FOR THE DURATION OF THE PROJECT. 12. WET SEASON REQUIREMENTS AS DESCRIBED IN APPENDIX D, SECTION D.2.4.2 OF THE KCSWDM ARE IN EFFECT BEGINNING OCTOBER 1 THROUGH APRIL 30. 13. ANY PERMANENT RETENTION/DETENTION FACILITY USED AS A TEMPORARY SETTLING BASIN SHALL BE MODIFIED WITH THE NECESSARY EROSION CONTROL MEASURES AND SHALL PROVIDE ADEQUATE STORAGE CAPACITY. IF THE PERMANENT FACILITY IS TO FUNCTION ULTIMATELY AS AN INFILTRATION OR DISPERSION SYSTEM, THE FACILITY SHALL NOT BE USED AS A TEMPORARY SETTLING BASIN. NO UNDERGROUND DETENTION TANKS OR VAULTS SHALL BE USED AS A TEMPORARY SETTLING BASIN. 14. WHERE SEEDING FOR TEMPORARY EROSION CONTROL IS REQUIRED, FAST GERMINATING GRASSES SHALL BE APPLIED AT AN APPROPRIATE RATE (I.E. ANNUAL OR PERENNIAL RYE APPLIED AT APPROXIMATELY 80 POUNDS PER ACRE). 15. WHERE STRAW MULCH FOR TEMPORARY EROSION CONTROL IS REQUIRED, IT SHALL BE APPLIED AT A MINIMUM THICKNESS OF TWO INCHES. 16. MANAGEMENT PRACTICES PROVIDING SIGNIFICANT TREE PROTECTION SHALL BE PROVIDED PER SECTION 19.120 OF FWRC. P a g e | 26 A. BMP Detail V-4.6 Maintenance Standards for Drainage Facilities The facility-specific maintenance standards contained in this section are intended to be conditions for determining if maintenance actions are required as identified through inspection.They are not intended to be measures of the facility's required condition at all times between inspections.In other words,exceedence of these conditions at any time between inspections and/or maintenance does not automatically constitute a violation of these standards.However,based upon inspection observations,the inspection and maintenance schedules shall be adjusted to minimize the length of time that a facility is in a condition that requires a maintenance action. Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed General Trash &Debris Any trash and debris which exceed 1 cubic feet per 1,000 square feet.In general,there should be no visual evidence of dumping. If less than threshold all trash and debris will be removed as part of next scheduled main- tenance. Trash and debris cleared from site Poisonous Veget- ation and noxious weeds Any poisonous or nuis- ance vegetation which may constitute a haz- ard to maintenance per- sonnel or the public. Any evidence of nox- ious weeds as defined by State or local reg- ulations. (Apply requirements of adopted IPM policies for the use of herb- icides). No danger of poisonous vegetation where main- tenance personnel or the public might normally be. (Coordinate with local health department) Complete eradication of noxious weeds may not be possible.Compliance with State or local erad- ication policies required Contaminants Any evidence of oil,No contaminants or pol- Table V-4.5.2(1)Maintenance Standards -Detention Ponds 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 829 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed and Pollution gasoline,contaminants or other pollutants (Coordinate removal/cleanup with local water quality response agency). lutants present. Rodent Holes Any evidence of rodent holes if facility is acting as a dam or berm,or any evidence of water piping through dam or berm via rodent holes. Rodents destroyed and dam or berm repaired. (Coordinate with local health department; coordinate with Ecology Dam Safety Office if pond exceeds 10 acre-feet.) Beaver Dams Dam results in change or function of the facil- ity. Facility is returned to design function. (Coordinate trapping of beavers and removal of dams with appropriate per- mitting agencies) Insects When insects such as wasps and hornets interfere with main- tenance activities. Insects destroyed or removed from site. Apply insecticides in com- pliance with adopted IPM policies Tree Growth and Hazard Trees Tree growth does not allow maintenance access or interferes with maintenance activ- ity (i.e.,slope mowing, silt removal,vactoring, or equipment move- ments).If trees are not interfering with access or maintenance,do not remove Trees do not hinder main- tenance activities.Har- vested trees should be recycled into mulch or other beneficial uses (e.g., alders for firewood). Remove hazard Trees Table V-4.5.2(1)Maintenance Standards -Detention Ponds (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 830 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed If dead,diseased,or dying trees are iden- tified (Use a certified Arbor- ist to determine health of tree or removal requirements) Side Slopes of Pond Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Any erosion observed on a compacted berm embankment. Slopes should be sta- bilized using appropriate erosion control measure (s);e.g.,rock rein- forcement,planting of grass,compaction. If erosion is occurring on compacted berms a licensed civil engineer should be consulted to resolve source of erosion. Storage Area Sediment Accumulated sediment that exceeds 10%of the designed pond depth unless otherwise specified or affects inletting or outletting condition of the facility. Sediment cleaned out to designed pond shape and depth;pond reseeded if necessary to control erosion. Liner (if Applic- able) Liner is visible and has more than three 1/4- inch holes in it. Liner repaired or replaced. Liner is fully covered. Ponds Berms (Dikes)Settlements Any part of berm which has settled 4 inches lower than the design elevation If settlement is appar- ent,measure berm to determine amount of settlement Dike is built back to the design elevation. Table V-4.5.2(1)Maintenance Standards -Detention Ponds (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 831 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed Settling can be an indication of more severe problems with the berm or outlet works.A licensed civil engineer should be consulted to determine the source of the set- tlement. Piping Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. (Recommend a Goeth- echnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Piping eliminated.Erosion potential resolved. Emergency Over- flow/Spillway and Berms over 4 feet in height Tree Growth Tree growth on emer- gency spillways cre- ates blockage problems and may cause failure of the berm due to uncon- trolled overtopping. Tree growth on berms over 4 feet in height may lead to piping through the berm which could lead to fail- ure of the berm. Trees should be removed. If root system is small (base less than 4 inches) the root system may be left in place.Otherwise the roots should be removed and the berm restored.A licensed civil engineer should be consulted for proper berm/spillway res- toration. Piping Discernable water flow through pond berm. Ongoing erosion with Piping eliminated.Erosion potential resolved. Table V-4.5.2(1)Maintenance Standards -Detention Ponds (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 832 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expected When Maintenance Is Per- formed potential for erosion to continue. (Recommend a Goeth- echnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Emergency Over- flow/Spillway Emergency Over- flow/Spillway Only one layer of rock exists above native soil in area five square feet or larger,or any expos- ure of native soil at the top of out flow path of spillway. (Rip-rap on inside slopes need not be replaced.) Rocks and pad depth are restored to design stand- ards. Erosion See "Side Slopes of Pond" Table V-4.5.2(1)Maintenance Standards -Detention Ponds (continued) Maintenance Component Defect Conditions When Maintenance Is Needed Results Expec- ted When Maintenance Is Performed General Trash &Debris See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Poisonous/Noxious Vegetation See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Contaminants and Pollution See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Rodent Holes See "Detention Ponds"(No.1).See "Detention Ponds"(No.1) Storage Area Sediment Water ponding in infiltration pond after rainfall ceases and appropriate Sediment is removed Table V-4.5.2(2)Maintenance Standards -Infiltration 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 833 Maintenance Component Defect Conditions When Maintenance Is Needed Results Expec- ted When Maintenance Is Performed time allowed for infiltration.Treat- ment basins should infiltrate Water Quality Design Storm Volume within 48 hours,and empty within 24 hours after cessation of most rain events. (A percolation test pit or test of facility indicates facility is only working at 90%of its designed capabilities.Test every 2 to 5 years.If two inches or more sediment is present,remove). and/or facility is cleaned so that infiltration sys- tem works according to design. Filter Bags (if applicable) Filled with Sed- iment and Debris Sediment and debris fill bag more than 1/2 full. Filter bag is replaced or sys- tem is redesigned. Rock Filters Sediment and Debris By visual inspection,little or no water flows through filter during heavy rain storms. Gravel in rock filter is replaced. Side Slopes of Pond Erosion See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Emergency Overflow Spillway and Berms over 4 feet in height. Tree Growth See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Piping See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Emergency Overflow Spillway Rock Missing See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Erosion See "Detention Ponds"(No.1).See "Detention Ponds"(No.1). Pre-settling Ponds and Vaults Facility or sump filled with Sediment and/or debris 6"or designed sediment trap depth of sediment. Sediment is removed. Table V-4.5.2(2)Maintenance Standards -Infiltration (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 834 Maintenance Component Defect Conditions When Maintenance is Needed Results Expec- ted When Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is blocked at any point or the vent is damaged. Vents open and functioning. Debris and Sed- iment Accumulated sediment depth exceeds 10%of the diameter of the storage area for 1/2 length of storage vault or any point depth exceeds 15%of diameter. (Example:72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) All sediment and debris removed from storage area. Joints Between Tank/Pipe Sec- tion Any openings or voids allowing mater- ial to be transported into facility. (Will require engineering analysis to determine structural stability). All joint between tank/pipe sec- tions are sealed. Tank Pipe Bent Out of Shape Any part of tank/pipe is bent out of shape more than 10%of its design shape.(Review required by engineer to determine structural stability). Tank/pipe repaired or replaced to design. Vault Structure Includes Cracks in Wall,Bottom, Damage to Frame and/or Top Slab Cracks wider than 1/2-inch and any evidence of soil particles entering the structure through the cracks,or main- tenance/inspection personnel determ- ines that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the walls. Vault replaced or repaired to design spe- cifications and is structurally sound. No cracks more than 1/4-inch wide at the joint of the inlet/out- let pipe. Manhole Cover Not in Place Cover is missing or only partially in place.Any open manhole requires maintenance. Manhole is closed. Table V-4.5.2(3)Maintenance Standards -Closed Detention Systems (Tanks/Vaults) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 835 Maintenance Component Defect Conditions When Maintenance is Needed Results Expec- ted When Maintenance is Performed Locking Mech- anism Not Work- ing Mechanism cannot be opened by one maintenance person with proper tools. Bolts into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Mechanism opens with proper tools. Cover Difficult to Remove One maintenance person cannot remove lid after applying normal lifting pressure.Intent is to keep cover from sealing off access to maintenance. Cover can be removed and reinstalled by one main- tenance per- son. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, misalignment,not securely attached to structure wall,rust,or cracks. Ladder meets design stand- ards.Allows maintenance person safe access. Catch Basins See "Catch Bas- ins" (No.5)See "Catch Basins" (No.5).See "Catch Basins" (No.5). Table V-4.5.2(3)Maintenance Standards -Closed Detention Systems (Tanks/Vaults)(continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Performed General Trash and Debris (Includes Sediment) Material exceeds 25%of sump depth or 1 foot below orifice plate. Control structure orifice is not blocked.All trash and debris removed. Structural Damage Structure is not securely attached to manhole wall. Structure is not in upright position (allow up to 10% from plumb). Connections to outlet pipe Structure securely attached to wall and outlet pipe. Structure in correct position. Connections to outlet pipe are water tight;structure repaired or replaced and works as Table V-4.5.2(4)Maintenance Standards -Control Structure/Flow Restrictor 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 836 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Performed are not watertight and show signs of rust. Any holes -other than designed holes -in the structure. designed. Structure has no holes other than designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not water- tight or is missing. Gate cannot be moved up and down by one main- tenance person. Chain/rod leading to gate is missing or damaged. Gate is rusted over 50%of its surface area. Gate is watertight and works as designed. Gate moves up and down eas- ily and is watertight. Chain is in place and works as designed. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not work- ing properly due to missing, out of place,or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash,debris,sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking)the overflow pipe. Pipe is free of all obstructions and works as designed. Manhole See "Closed Detention Systems" (No.3). See "Closed Detention Sys- tems" (No.3). See "Closed Detention Sys- tems" (No.3). Catch Basin See "Catch Basins" (No. 5). See "Catch Basins" (No.5).See "Catch Basins" (No.5). Table V-4.5.2(4)Maintenance Standards -Control Structure/Flow Restrictor (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 837 Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Main- tenance is performed General Trash & Debris Trash or debris which is located imme- diately in front of the catch basin opening or is blocking inletting capacity of the basin by more than 10%. Trash or debris (in the basin)that exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the low- est pipe into or out of the basin,but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Trash or debris in any inlet or outlet pipe blocking more than 1/3 of its height. Dead animals or vegetation that could gen- erate odors that could cause complaints or dangerous gases (e.g.,methane). No Trash or debris loc- ated imme- diately in front of catch basin or on grate open- ing. No trash or debris in the catch basin. Inlet and out- let pipes free of trash or debris. No dead animals or vegetation present within the catch basin. Sediment Sediment (in the basin)that exceeds 60 per- cent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin,but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. No sediment in the catch basin Structure Damage to Frame and/or Top Slab Top slab has holes larger than 2 square inches or cracks wider than 1/4 inch.(Intent is to make sure no material is running into basin). Top slab is free of holes and cracks. Frame is sit- Table V-4.5.2(5)Maintenance Standards -Catch Basins 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 838 Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Main- tenance is performed Frame not sitting flush on top slab,i.e.,sep- aration of more than 3/4 inch of the frame from the top slab.Frame not securely attached ting flush on the riser rings or top slab and firmly attached. Fractures or Cracks in Basin Walls/ Bottom Maintenance person judges that structure is unsound. Grout fillet has separated or cracked wider than 1/2 inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. Basin replaced or repaired to design stand- ards. Pipe is regrouted and secure at basin wall. Settlement/ Misalignment If failure of basin has created a safety,func- tion,or design problem. Basin replaced or repaired to design stand- ards. Vegetation Vegetation growing across and blocking more than 10%of the basin opening. Vegetation growing in inlet/outlet pipe joints that is more than six inches tall and less than six inches apart. No veget- ation block- ing opening to basin. No veget- ation or root growth present. Contamination and Pollution See "Detention Ponds"(No.1).No pollution present. Catch Basin Cover Cover Not in Place Cover is missing or only partially in place. Any open catch basin requires main- tenance. Catch basin cover is closed Locking Mech- anism Not Mechanism cannot be opened by one main- tenance person with proper tools.Bolts into Mechanism opens with Table V-4.5.2(5)Maintenance Standards -Catch Basins (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 839 Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Main- tenance is performed Working frame have less than 1/2 inch of thread.proper tools. Cover Difficult to Remove One maintenance person cannot remove lid after applying normal lifting pressure. (Intent is keep cover from sealing off access to maintenance.) Cover can be removed by one main- tenance per- son. Ladder Ladder Rungs Unsafe Ladder is unsafe due to missing rungs,not securely attached to basin wall,mis- alignment,rust,cracks,or sharp edges. Ladder meets design stand- ards and allows main- tenance per- son safe access. Metal Grates (If Applic- able) Grate opening Unsafe Grate with opening wider than 7/8 inch. Grate open- ing meets design stand- ards. Trash and Debris Trash and debris that is blocking more than 20%of grate surface inletting capacity. Grate free of trash and debris. Damaged or Missing. Grate missing or broken member(s)of the grate. Grate is in place and meets design standards. Table V-4.5.2(5)Maintenance Standards -Catch Basins (continued) Maintenance Com- ponents Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed General Trash and Debris Trash or debris that is plugging more than 20%of the openings in the barrier. Barrier cleared to design flow capacity. Metal Damaged/ Missing Bars are bent out of shape more than 3 inches. Bars in place with no bends more than 3/4 Table V-4.5.2(6)Maintenance Standards -Debris Barriers (e.g.,Trash Racks) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 840 Maintenance Com- ponents Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Bars. Bars are missing or entire barrier missing. Bars are loose and rust is causing 50%deterioration to any part of bar- rier. inch. Bars in place according to design. Barrier replaced or repaired to design stand- ards. Inlet/Outlet Pipe Debris barrier missing or not attached to pipe Barrier firmly attached to pipe Table V-4.5.2(6)Maintenance Standards -Debris Barriers (e.g.,Trash Racks)(continued) Maintenance Components Defect Conditions When Maintenance is Needed Results Expec- ted When Main- tenance is Performed External: Rock Pad Missing or Moved Rock Only one layer of rock exists above nat- ive soil in area five square feet or lar- ger,or any exposure of native soil. Rock pad replaced to design stand- ards. Erosion Soil erosion in or adjacent to rock pad. Rock pad replaced to design stand- ards. Dispersion Trench Pipe Plugged with Sed- iment Accumulated sediment that exceeds 20%of the design depth. Pipe cleaned/- flushed so that it matches design. Not Dis- charging Water Prop- erly Visual evidence of water discharging at concentrated points along trench (normal condition is a "sheet flow" of water along trench).Intent is to prevent erosion damage. Trench redesigned or rebuilt to stand- ards. Perforations Plugged. Over 1/2 of perforations in pipe are plugged with debris and sediment. Perforated pipe cleaned or replaced. Table V-4.5.2(7)Maintenance Standards -Energy Dissipaters 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 841 Maintenance Components Defect Conditions When Maintenance is Needed Results Expec- ted When Main- tenance is Performed Water Flows Out Top of "Dis- tributor" Catch Basin. Maintenance person observes or receives credible report of water flow- ing out during any storm less than the design storm or its causing or appears likely to cause damage. Facility rebuilt or redesigned to standards. Receiving Area Over- Saturated Water in receiving area is causing or has potential of causing landslide prob- lems. No danger of landslides. Internal: Manhole/Chamber Worn or Damaged Post, Baffles, Side of Chamber Structure dissipating flow deteriorates to 1/2 of original size or any con- centrated worn spot exceeding one square foot which would make struc- ture unsound. Structure replaced to design stand- ards. Other Defects See "Catch Basins" (No.5).See "Catch Bas- ins" (No.5). Table V-4.5.2(7)Maintenance Standards -Energy Dissipaters (continued) Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem General Sediment Accu- mulation on Grass Sediment depth exceeds 2 inches. Remove sediment deposits on grass treatment area of the bio-swale. When finished,swale should be level from side to side and drain freely toward outlet.There should be no areas of standing water once inflow has ceased. Standing Water When water stands in the swale between storms and does not drain freely. Any of the following may apply: remove sediment or trash blockages, improve grade from head to foot of swale,remove clogged check dams, add underdrains or convert to a wet Table V-4.5.2(8)Maintenance Standards -Typical Biofiltration Swale 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 842 Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem biofiltration swale. Table V-4.5.2(8)Maintenance Standards -Typical Biofiltration Swale (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 843 Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem Flow spreader Flow spreader uneven or clogged so that flows are not uni- formly distributed through entire swale width. Level the spreader and clean so that flows are spread evenly over entire swale width. Constant Base- flow When small quantities of water continually flow through the swale,even when it has been dry for weeks, and an eroded, muddy channel has formed in the swale bottom. Add a low-flow pea-gravel drain the length of the swale or by-pass the baseflow around the swale. Poor Vegetation Coverage When grass is sparse or bare or eroded patches occur in more than 10%of the swale bottom. Determine why grass growth is poor and correct that condition.Re-plant with plugs of grass from the upper slope:plant in the swale bottom at 8- inch intervals.Or re-seed into loosened,fertile soil. Vegetation When the grass becomes excess- ively tall (greater than 10-inches); when nuisance weeds and other vegetation starts to take over. Mow vegetation or remove nuisance vegetation so that flow not impeded. Grass should be mowed to a height of 3 to 4 inches.Remove grass clip- pings. Excessive Shad- ing Grass growth is poor because sunlight does not reach swale. If possible,trim back over-hanging limbs and remove brushy vegetation on adjacent slopes. Table V-4.5.2(8)Maintenance Standards -Typical Biofiltration Swale (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 844 Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem Inlet/Outlet Inlet/outlet areas clogged with sed- iment and/or debris. Remove material so that there is no clogging or blockage in the inlet and outlet area. Trash and Debris Accumulation Trash and debris accumulated in the bio-swale. Remove trash and debris from bioswale. Erosion/Scouring Eroded or scoured swale bottom due to flow chan- nelization,or higher flows. For ruts or bare areas less than 12 inches wide,repair the damaged area by filling with crushed gravel.If bare areas are large,generally greater than 12 inches wide,the swale should be re-graded and re- seeded.For smaller bare areas,over- seed when bare spots are evident,or take plugs of grass from the upper slope and plant in the swale bottom at 8-inch intervals. Table V-4.5.2(8)Maintenance Standards -Typical Biofiltration Swale (continued) Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem General Sediment Accu- mulation Sediment depth exceeds 2-inches in 10%of the swale treatment area. Remove sediment deposits in treatment area. Water Depth Water not retained to a depth of about 4 inches during the wet season. Build up or repair outlet berm so that water is retained in the wet swale. Wetland Veget- ation Vegetation becomes sparse and does not provide adequate fil- tration,OR veget- ation is crowded out Determine cause of lack of vigor of vegetation and correct. Replant as needed.For excess- ive cattail growth,cut cattail shoots back and compost off-site. Table V-4.5.2(9)Maintenance Standards -Wet Biofiltration Swale 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 845 Maintenance Component Defect or Prob- lem Condition When Maintenance is Needed Recommended Maintenance to Correct Problem by very dense clumps of cattail, which do not allow water to flow through the clumps. Note:normally wetland veget- ation does not need to be har- vested unless die-back is causing oxygen depletion in downstream waters. Inlet/Outlet Inlet/outlet area clogged with sed- iment and/or debris. Remove clogging or blockage in the inlet and outlet areas. Trash and Debris Accumulation See "Detention Ponds"(No.1). Remove trash and debris from wet swale. Erosion/Scouring Swale has eroded or scoured due to flow channelization,or higher flows. Check design flows to assure swale is large enough to handle flows.By-pass excess flows or enlarge swale.Replant eroded areas with fibrous-rooted plants such as Juncus effusus (soft rush)in wet areas or snowberry (Symphoricarpos albus)in dryer areas. Table V-4.5.2(9)Maintenance Standards -Wet Biofiltration Swale (continued) Maintenance Component Defect or Prob- lem Condition When Main- tenance is Needed Recommended Maintenance to Cor- rect Problem General Sediment Accu- mulation on Grass Sediment depth exceeds 2 inches. Remove sediment deposits,re-level so slope is even and flows pass evenly through strip. Vegetation When the grass becomes excessively tall (greater than 10-inches); when nuisance weeds and other veget- Mow grass,control nuisance veget- ation,such that flow not impeded. Grass should be mowed to a height between 3-4 inches. Table V-4.5.2(10)Maintenance Standards -Filter Strips 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 846 Maintenance Component Defect or Prob- lem Condition When Main- tenance is Needed Recommended Maintenance to Cor- rect Problem ation starts to take over. Trash and Debris Accumulation Trash and debris accu- mulated on the filter strip. Remove trash and Debris from filter. Erosion/Scouring Eroded or scoured areas due to flow channelization, or higher flows. For ruts or bare areas less than 12 inches wide,repair the damaged area by filling with crushed gravel.The grass will creep in over the rock in time.If bare areas are large,generally greater than 12 inches wide,the filter strip should be re-graded and re- seeded.For smaller bare areas,over- seed when bare spots are evident. Flow spreader Flow spreader uneven or clogged so that flows are not uniformly dis- tributed through entire filter width. Level the spreader and clean so that flows are spread evenly over entire fil- ter width. Table V-4.5.2(10)Maintenance Standards -Filter Strips (continued) Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Main- tenance is Performed General Water level First cell is empty, doesn't hold water. Line the first cell to maintain at least 4 feet of water.Although the second cell may drain,the first cell must remain full to control turbulence of the incoming flow and reduce sed- iment resuspension. Trash and Debris Accumulation that exceeds 1 CF per Trash and debris removed from pond. Table V-4.5.2(11)Maintenance Standards -Wetponds 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 847 Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Main- tenance is Performed 1000-SF of pond area. Inlet/Outlet Pipe Inlet/Outlet pipe clogged with sed- iment and/or debris material. No clogging or blockage in the inlet and outlet piping. Sediment Accumulation in Pond Bot- tom Sediment accu- mulations in pond bot- tom that exceeds the depth of sediment zone plus 6-inches, usually in the first cell. Sediment removed from pond bot- tom. Oil Sheen on Water Prevalent and visible oil sheen. Oil removed from water using oil- absorbent pads or vactor truck. Source of oil located and corrected.If chronic low levels of oil persist,plant wetland plants such as Juncus effusus (soft rush)which can uptake small concentrations of oil. Erosion Erosion of the pond's side slopes and/or scouring of the pond bottom,that exceeds 6-inches,or where continued erosion is prevalent. Slopes stabilized using proper erosion control measures and repair methods. Settlement of Pond Dike/Berm Any part of these com- ponents that has settled 4-inches or lower than the design elevation,or inspector determines dike/berm is unsound. Dike/berm is repaired to spe- cifications. Internal Berm Berm dividing cells should be level. Berm surface is leveled so that water flows evenly over entire length of Table V-4.5.2(11)Maintenance Standards -Wetponds (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 848 Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Main- tenance is Performed berm. Overflow Spillway Rock is missing and soil is exposed at top of spillway or outside slope. Rocks replaced to specifications. Table V-4.5.2(11)Maintenance Standards -Wetponds (continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Main- tenance is Performed General Trash/Debris Accumulation Trash and debris accu- mulated in vault,pipe or inlet/outlet (includes float- ables and non-float- ables). Remove trash and debris from vault. Sediment Accumulation in Vault Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6-inches. Remove sediment from vault. Damaged Pipes Inlet/outlet piping dam- aged or broken and in need of repair. Pipe repaired and/or replaced. Access Cover Damaged/Not Working Cover cannot be opened or removed,especially by one person. Pipe repaired or replaced to proper working specifications. Ventilation Ventilation area blocked or plugged. Blocking material removed or cleared from ventilation area.A specified %of the vault surface area must provide ventilation to the vault interior (see design spe- cifications). Vault Struc- ture Damage -Includes Cracks in Walls Bottom, Damage to Maintenance/inspection personnel determine that the vault is not struc- turally sound. Cracks wider than 1/2- Vault replaced or repairs made so that vault meets design spe- cifications and is structurally sound. Vault repaired so that no cracks Table V-4.5.2(12)Maintenance Standards -Wetvaults 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 849 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Main- tenance is Performed Frame and/or Top Slab inch at the joint of any inlet/outlet pipe or evid- ence of soil particles entering through the cracks. exist wider than 1/4-inch at the joint of the inlet/outlet pipe. Baffles Baffles corroding,crack- ing,warping and/or show- ing signs of failure as determined by main- tenance/inspection staff. Baffles repaired or replaced to specifications. Access Lad- der Damage Ladder is corroded or deteriorated,not func- tioning properly,not attached to structure wall, missing rungs,has cracks and/or misaligned. Confined space warning sign missing. Ladder replaced or repaired to specifications,and is safe to use as determined by inspection per- sonnel.Replace sign warning of confined space entry require- ments.Ladder and entry noti- fication complies with OSHA standards. Table V-4.5.2(12)Maintenance Standards -Wetvaults (continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Main- tenance is Performed Above Ground (open sand fil- ter) Sediment Accumulation on top layer Sediment depth exceeds 1/2-inch. No sediment deposit on grass layer of sand filter that would impede permeability of the filter section. Trash and Debris Accu- mulations Trash and debris accu- mulated on sand filter bed. Trash and debris removed from sand filter bed. Sediment/ Debris in Clean-Outs When the clean-outs become full or partially plugged with sediment and/or debris. Sediment removed from clean- outs. Sand Filter Media Drawdown of water through the sand filter media takes longer than 24-hours,and/or flow Top several inches of sand are scraped.May require replace- ment of entire sand filter depth depending on extent of plugging Table V-4.5.2(13)Maintenance Standards -Sand Filters (Above Ground/Open) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 850 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Main- tenance is Performed through the overflow pipes occurs frequently. (a sieve analysis is helpful to determine if the lower sand has too high a proportion of fine material). Prolonged Flows Sand is saturated for pro- longed periods of time (several weeks)and does not dry out between storms due to con- tinuous base flow or pro- longed flows from detention facilities. Low,continuous flows are lim- ited to a small portion of the facil- ity by using a low wooden divider or slightly depressed sand surface. Short Cir- cuiting When flows become con- centrated over one sec- tion of the sand filter rather than dispersed. Flow and percolation of water through sand filter is uniform and dispersed across the entire filter area. Erosion Damage to Slopes Erosion over 2-inches deep where cause of damage is prevalent or potential for continued erosion is evident. Slopes stabilized using proper erosion control measures. Rock Pad Missing or Out of Place Soil beneath the rock is visible. Rock pad replaced or rebuilt to design specifications. Flow Spreader Flow spreader uneven or clogged so that flows are not uniformly distributed across sand filter. Spreader leveled and cleaned so that flows are spread evenly over sand filter. Damaged Pipes Any part of the piping that is crushed or deformed more than 20% or any other failure to the piping. Pipe repaired or replaced. Table V-4.5.2(13)Maintenance Standards -Sand Filters (Above Ground/Open)(continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 851 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed Below Ground Vault. Sediment Accu- mulation on Sand Media Sec- tion Sediment depth exceeds 1/2-inch. No sediment deposits on sand filter section that which would impede per- meability of the filter sec- tion. Sediment Accu- mulation in Pre- Settling Portion of Vault Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6-inches. No sediment deposits in first chamber of vault. Trash/Debris Accumulation Trash and debris accu- mulated in vault,or pipe inlet/outlet,floatables and non-floatables. Trash and debris removed from vault and inlet/outlet piping. Sediment in Drain Pipes/Cleanouts When drain pipes,cleanouts become full with sediment and/or debris. Sediment and debris removed. Short Circuiting When seepage/flow occurs along the vault walls and corners.Sand eroding near inflow area. Sand filter media section re-laid and compacted along perimeter of vault to form a semi-seal.Erosion protection added to dis- sipate force of incoming flow and curtail erosion. Damaged Pipes Inlet or outlet piping dam- aged or broken and in need of repair. Pipe repaired and/or replaced. Access Cover Damaged/Not Working Cover cannot be opened, corrosion/deformation of cover. Maintenance person cannot remove cover using normal lifting pressure. Cover repaired to proper working specifications or replaced. Ventilation Ventilation area blocked or plugged Blocking material removed or cleared from ventilation Table V-4.5.2(14)Maintenance Standards -Sand Filters (Below Ground/Enclosed) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 852 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed area.A specified %of the vault surface area must provide ventilation to the vault interior (see design specifications). Vault Structure Damaged; Includes Cracks in Walls,Bot- tom,Damage to Frame and/or Top Slab. Cracks wider than 1/2-inch or evidence of soil particles entering the structure through the cracks,or main- tenance/inspection per- sonnel determine that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or evidence of soil particles entering through the cracks. Vault replaced or repairs made so that vault meets design specifications and is structurally sound. Vault repaired so that no cracks exist wider than 1/4-inch at the joint of the inlet/outlet pipe. Baffles/Internal walls Baffles or walls corroding, cracking,warping and/or showing signs of failure as determined by main- tenance/inspection person. Baffles repaired or replaced to specifications. Access Ladder Damaged Ladder is corroded or deteri- orated,not functioning prop- erly,not securely attached to structure wall,missing rungs,cracks,and mis- aligned. Ladder replaced or repaired to specifications, and is safe to use as determined by inspection personnel. Table V-4.5.2(14)Maintenance Standards -Sand Filters (Below Ground/Enclosed)(continued) Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Below Ground Vault Sediment Accu-Sediment depth exceeds 0.25- inches.No sediment depos- Table V-4.5.2(15)Maintenance Standards -Manufactured Media Filters 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 853 Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed mulation on Media. its which would impede permeability of the compost media. Sediment Accu- mulation in Vault Sediment depth exceeds 6-inches in first chamber. No sediment depos- its in vault bottom of first chamber. Trash/Debris Accumulation Trash and debris accumulated on compost filter bed. Trash and debris removed from the compost filter bed. Sediment in Drain Pipes/Clean- Outs When drain pipes,clean-outs, become full with sediment and/or debris. Sediment and debris removed. Damaged Pipes Any part of the pipes that are crushed or damaged due to cor- rosion and/or settlement. Pipe repaired and/or replaced. Access Cover Damaged/Not Working Cover cannot be opened;one per- son cannot open the cover using normal lifting pressure,cor- rosion/deformation of cover. Cover repaired to proper working spe- cifications or replaced. Vault Structure Includes Cracks in Wall, Bottom, Damage to Frame and/or Top Slab Cracks wider than 1/2-inch or evid- ence of soil particles entering the structure through the cracks,or maintenance/inspection personnel determine that the vault is not struc- turally sound. Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or evid- ence of soil particles entering through the cracks. Vault replaced or repairs made so that vault meets design specifications and is structurally sound. Vault repaired so that no cracks exist wider than 1/4-inch at the joint of the inlet/outlet pipe. Baffles Baffles corroding,cracking warp- ing,and/or showing signs of failure as determined by main- tenance/inspection person. Baffles repaired or replaced to spe- cifications. Table V-4.5.2(15)Maintenance Standards -Manufactured Media Filters (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 854 Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Access Ladder Damaged Ladder is corroded or deteriorated, not functioning properly,not securely attached to structure wall, missing rungs,cracks,and mis- aligned. Ladder replaced or repaired and meets specifications,and is safe to use as determ- ined by inspection personnel. Below Ground Cart- ridge Type Media Drawdown of water through the media takes longer than 1 hour, and/or overflow occurs frequently. Media cartridges replaced. Short Circuiting Flows do not properly enter filter cartridges. Filter cartridges replaced. Table V-4.5.2(15)Maintenance Standards -Manufactured Media Filters (continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Performed General Monitoring Inspection of discharge water for obvious signs of poor water quality. Effluent discharge from vault should be clear with out thick visible sheen. Sediment Accu- mulation Sediment depth in bottom of vault exceeds 6-inches in depth. No sediment deposits on vault bottom that would impede flow through the vault and reduce separation effi- ciency. Trash and Debris Accumulation Trash and debris accu- mulation in vault,or pipe inlet/outlet,floatables and non-floatables. Trash and debris removed from vault, and inlet/outlet piping. Oil Accumulation Oil accumulations that exceed 1-inch,at the surface of the water. Extract oil from vault by vactoring.Disposal in accordance with state and local rules and reg- ulations. Table V-4.5.2(16)Maintenance Standards -Baffle Oil/Water Separators (API Type) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 855 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Performed Damaged Pipes Inlet or outlet piping dam- aged or broken and in need of repair. Pipe repaired or replaced. Access Cover Damaged/Not Working Cover cannot be opened, corrosion/deformation of cover. Cover repaired to proper working spe- cifications or replaced. Vault Structure Damage -Includes Cracks in Walls Bot- tom,Damage to Frame and/or Top Slab See "Catch Basins" (No.5) Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or evidence of soil particles entering through the cracks. Vault replaced or repairs made so that vault meets design spe- cifications and is struc- turally sound. Vault repaired so that no cracks exist wider than 1/4-inch at the joint of the inlet/outlet pipe. Baffles Baffles corroding,cracking, warping and/or showing signs of failure as determ- ined by main- tenance/inspection person. Baffles repaired or replaced to spe- cifications. Access Ladder Damaged Ladder is corroded or deteri- orated,not functioning prop- erly,not securely attached to structure wall,missing rungs, cracks,and misaligned. Ladder replaced or repaired and meets spe- cifications,and is safe to use as determined by inspection per- sonnel. Table V-4.5.2(16)Maintenance Standards -Baffle Oil/Water Separators (API Type)(continued) Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed General Monitoring Inspection of discharge water for obvious signs of poor water Effluent discharge from vault should be clear with Table V-4.5.2(17)Maintenance Standards -Coalescing Plate Oil/Water Separators 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 856 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed quality.no thick visible sheen. Table V-4.5.2(17)Maintenance Standards -Coalescing Plate Oil/Water Separators (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 857 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed Sediment Accu- mulation Sediment depth in bottom of vault exceeds 6-inches in depth and/or visible signs of sediment on plates. No sediment deposits on vault bottom and plate media,which would impede flow through the vault and reduce sep- aration efficiency. Trash and Debris Accu- mulation Trash and debris accumulated in vault,or pipe inlet/outlet, floatables and non-floatables. Trash and debris removed from vault,and inlet/outlet piping. Oil Accu- mulation Oil accumulation that exceeds 1-inch at the water surface. Oil is extracted from vault using vactoring methods. Coalescing plates are cleaned by thoroughly rinsing and flushing. Should be no visible oil depth on water. Damaged Coalescing Plates Plate media broken, deformed,cracked and/or showing signs of failure. A portion of the media pack or the entire plate pack is replaced depend- ing on severity of failure. Damaged Pipes Inlet or outlet piping damaged or broken and in need of repair. Pipe repaired and or replaced. Baffles Baffles corroding,cracking, warping and/or showing signs of failure as determined by maintenance/inspection per- son. Baffles repaired or replaced to specifications. Vault Structure Damage - Includes Cracks in Walls,Bottom, Damage to Frame and/or Top Slab Cracks wider than 1/2-inch or evidence of soil particles enter- ing the structure through the cracks,or main- tenance/inspection personnel determine that the vault is not structurally sound. Vault replaced or repairs made so that vault meets design specifications and is structurally sound. Vault repaired so that no cracks exist wider than 1/4-inch at the joint of the Table V-4.5.2(17)Maintenance Standards -Coalescing Plate Oil/Water Separators (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 858 Maintenance Component Defect Condition When Main- tenance is Needed Results Expected When Maintenance is Per- formed Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or evidence of soil particles entering through the cracks. inlet/outlet pipe. Access Ladder Damaged Ladder is corroded or deteri- orated,not functioning prop- erly,not securely attached to structure wall,missing rungs, cracks,and misaligned. Ladder replaced or repaired and meets spe- cifications,and is safe to use as determined by inspection personnel. Table V-4.5.2(17)Maintenance Standards -Coalescing Plate Oil/Water Separators (continued) Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance is Performed General Sediment Accumulation When sediment forms a cap over the insert media of the insert and/or unit. No sediment cap on the insert media and its unit. Trash and Debris Accu- mulation Trash and debris accumulates on insert unit creating a block- age/restriction. Trash and debris removed from insert unit.Runoff freely flows into catch basin. Media Insert Not Remov- ing Oil Effluent water from media insert has a visible sheen. Effluent water from media insert is free of oils and has no visible sheen. Media Insert Water Sat- urated Catch basin insert is saturated with water and no longer has the capacity to absorb. Remove and replace media insert Media Insert- Oil Saturated Media oil saturated due to pet- roleum spill that drains into catch basin. Remove and replace media insert. Media Insert Use Beyond Product Life Media has been used beyond the typical average life of media insert product. Remove and replace media at regular intervals,depend- ing on insert product. Table V-4.5.2(18)Maintenance Standards -Catch Basin Inserts 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 859 Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance is Per- formed General Sediment accumulation on grass filter strip Sediment depth exceeds 2 inches or creates uneven grad- ing that interferes with sheet flow. Remove sediment deposits on grass treatment area of the embankment.When fin- ished,embankment should be level from side to side and drain freely toward the toe of the embankment slope.There should be no areas of standing water once inflow has ceased. No-veget- ation zone/- flow spreader Flow spreader is uneven or clogged so that flows are not uniformly distributed over entire embankment width. Level the spreader and clean to spread flows evenly over entire embank- ment width. Poor veget- ation cov- erage Grass is sparse or bare,or eroded patches are observed in more than 10%of the grass strip surface area. Determine why grass growth is poor and correct the offending condition. Reseed into loosened,fer- tile soil or compost;or, replant with plugs of grass from the upper slope. Vegetation Grass becomes excessively tall (greater than 10 inches);nuis- ance weeds and other veget- ation start to take over. Mow vegetation or remove nuisance vegetation to not impede flow.Mow grass to a height of 6 inches. Media filter drain mix replacement Water is seen on the surface of the media filter drain mix long after the storms have ceased. Typically,the 6-month,24-hour precipitation event should drain within 48 hours.More common storms should drain within 24 hours.Maintenance also needed on a 10-year cycle and during a preservation project. Excavate and replace all of the media filter drain mix contained within the media filter drain. Excessive shading Grass growth is poor because sunlight does not reach If possible,trim back over- hanging limbs and remove Table V-4.5.2(19)Maintenance Standards -Media Filter Drain (MFD) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 860 Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance is Per- formed embankment.brushy vegetation on adja- cent slopes. Trash and debris Trash and debris have accu- mulated on embankment. Remove trash and debris from embankment. Flooding of Media filter drain When media filter drain is inundated by flood water Evaluate media filter drain material for acceptable infiltration rate and replace if media filter drain does not meet long-term infilt- ration rate standards. Table V-4.5.2(19)Maintenance Standards -Media Filter Drain (MFD) (continued) Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance is Performed General Sediment accu- mulation on grass Sediment depth exceeds 2 inches. Remove sediment deposits.Relevel so slope is even and flows pass evenly through strip. Vegetation Grass becomes excessively tall (greater than 10 inches);nuis- ance weeds and other vegetation start to take over. Mow grass and control nuisance veget- ation so that flow is not impeded.Grass should be mowed to a height of 6 inches. Trash and debris Trash and debris have accumulated on the veget- ated filter strip. Remove trash and debris from filter. Table V-4.5.2(20)Maintenance Standards -Compost Amended Vegetated Filter Strip (CAVFS) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 861 Maintenance Component Defect Conditions When Main- tenance is Needed Results Expected When Maintenance is Performed Erosion/scouring Areas have eroded or scoured due to flow chan- nelization or high flows. For ruts or bare areas less than 12 inches wide,repair the damaged area by filling with a 50/50 mixture of crushed gravel and compost.The grass will creep in over the rock in time.If bare areas are large,generally greater than 12 inches wide,the vegetated filter strip should be regraded and reseeded.For smaller bare areas,overseed when bare spots are evident. Flow spreader Flow spreader is uneven or clogged so that flows are not uniformly distributed over entire fil- ter width. Level the spreader and clean so that flows are spread evenly over entire filter width Table V-4.5.2(20)Maintenance Standards -Compost Amended Vegetated Filter Strip (CAVFS)(continued) Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance Facility Footprint Earthen side slopes and berms B,S Erosion (gullies/ rills)greater than 2 inches deep around inlets,outlet, and alongside slopes l Eliminate cause of erosion and stabilize damaged area (regrade,rock,veget- ation,erosion control matting) l For deep channels or cuts (over 3 inches in ponding Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 862 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance depth),temporary erosion control meas- ures should be put in place until per- manent repairs can be made. l Properly designed, constructed and established facilities with appropriate flow velocities should not have erosion prob- lems except perhaps in extreme events.If erosion problems persist,the following should be reas- sessed:(1)flow volumes from con- tributing areas and bioretention facility sizing;(2)flow velo- cities and gradients within the facility; and (3)flow dis- sipation and erosion protection strategies at the facility inlet. A Erosion of sides causes slope to become a haz- ard Take actions to eliminate the hazard and stabilize slopes A,S Settlement greater than 3 Restore to design height Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 863 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance inches (relative to undisturbed sections of berm) A,S Downstream face of berm wet,seeps or leaks evident Plug any holes and com- pact berm (may require consultation with engin- eer,particularly for larger berms) A Any evidence of rodent holes or water piping in berm l Eradicate rodents (see "Pest control") l Fill holes and com- pact (may require consultation with engineer,par- ticularly for larger berms) Concrete side- walls A Cracks or failure of concrete side- walls l Repair/seal cracks l Replace if repair is insufficient Rockery side- walls A Rockery side walls are insec- ure Stabilize rockery side- walls (may require con- sultation with engineer, particularly for walls 4 feet or greater in height) Facility area All main- tenance visits (at least bian- nually) Trash and debris present Clean out trash and debris Facility bottom area A,S Accumulated sediment to extent that infilt- ration rate is l Remove excess sed- iment l Replace any veget- ation damaged or Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 864 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance reduced (see "Ponded water") or surface stor- age capacity sig- nificantly impacted destroyed by sed- iment accumulation and removal l Mulch newly planted vegetation l Identify and control the sediment source (if feasible) l If accumulated sed- iment is recurrent, consider adding pre- settlement or installing berms to create a forebay at the inlet During/after fall leaf drop Accumulated leaves in facility Remove leaves if there is a risk to clogging outlet structure or water flow is impeded Low per- meability check dams and weirs A,S Sediment,veget- ation,or debris accumulated at or blocking (or having the potential to block)check dam,flow con- trol weir or ori- fice Clear the blockage A,S Erosion and/or undercutting present Repair and take pre- ventative measures to pre- vent future erosion and/or undercutting Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 865 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance A Grade board or top of weir dam- aged or not level Restore to level position Ponded water B,S Excessive pond- ing water:Water overflows during storms smaller than the design event or ponded water remains in the basin 48 hours or longer after the end of a storm. Determine cause and resolve in the following order: 1.Confirm leaf or debris buildup in the bottom of the facility is not impeding infilt- ration.If necessary, remove leaf lit- ter/debris. 2.Ensure that under- drain (if present)is not clogged.If neces- sary,clear under- drain. 3.Check for other water inputs (e.g., groundwater,illicit connections). 4.Verify that the facility is sized appro- priately for the con- tributing area. Confirm that the con- tributing area has not increased.If steps #1-4 do not solve the problem, Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 866 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance the bioretention soil is likely clogged by sediment accu- mulation at the sur- face or has become overly compacted. Dig a small hole to observe soil profile and identify com- paction depth or clog- ging front to help determine the soil depth to be removed or otherwise rehab- ilitated (e.g.,tilled). Consultation with an engineer is recom- mended. Bioretention soil media As needed Bioretention soil media pro- tection is needed when performing main- tenance requir- ing entrance into the facility footprint l Minimize all loading in the facility foot- print (foot traffic and other loads)to the degree feasible in order to prevent com- paction of biore- tention soils. l Never drive equip- ment or apply heavy loads in facility foot- print. l Because the risk of compaction is higher during saturated soil Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 867 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance conditions,any type of loading in the cell (including foot traffic) should be minimized during wet con- ditions.â€¢Con- sider measures to distribute loading if heavy foot traffic is required or equip- ment must be placed in facility.As an example,boards may be placed across soil to dis- tribute loads and min- imize compaction. â€¢If compaction occurs,soil must be loosened or oth- erwise rehabilitated to original design state. Inlets/Outlets/Pipes Splash block inlet A Water is not being directed properly to the facility and away from the inlet structure Reconfigure/repair blocks to direct water to facility and away from structure Curb cut inlet/outlet M during the wet season and before severe storm Weekly during fall leaf drop Accumulated leaves at curb cuts Clear leaves (particularly important for key inlets and low points along long, linear facilities) Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 868 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance is forecasted Pipe inlet/out- let A Pipe is dam- aged Repair/replace W Pipe is clogged Remove roots or debris A,S Sediment, debris,trash,or mulch reducing capacity of inlet/outlet l Clear the blockage l Identify the source of the blockage and take actions to pre- vent future block- ages Weekly during fall leaf drop Accumulated leaves at inlets/outlets Clear leaves (particularly important for key inlets and low points along long, linear facilities) A Maintain access for inspections l Clear vegetation (transplant veget- ation when possible) within 1 foot of inlets and outlets,maintain access pathways l Consultation with a landscape architect is recommended for removal,transplant, or substitution of plants Erosion con- trol at inlet A Concentrated flows are caus- ing erosion Maintain a cover of rock or cobbles or other erosion protection measure (e.g., matting)to protect the ground where con- centrated water enters the facility (e.g.,a pipe,curb Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 869 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance cut or swale) Trash rack S Trash or other debris present on trash rack Remove/dispose A Bar screen dam- aged or missing Repair/replace Overflow A,S Capacity reduced by sed- iment or debris Remove sediment or debris/dispose Underdrain pipe Clean pipe as needed Clean orifice at least bian- nually (may need more fre- quent clean- ing during wet season) l Plant roots,sed- iment or debris reducing capacity of underdrain l Prolonged surface ponding (see "Pon- ded water" l Jet clean or rotary cut debris/roots from underdrain(s) l If underdrains are equipped with a flow restrictor (e.g.,ori- fice)to attenuate flows,the orifice must be cleaned reg- ularly. Vegetation Facility bottom area and upland slope vegetation Fall and Spring Vegetation sur- vival rate falls below 75% within first two years of estab- lishment (unless project O&M manual or record drawing stipulates more l Determine cause of poor vegetation growth and correct condition l Replant as neces- sary to obtain 75% survival rate or greater.Refer to ori- ginal planting plan, or approved jur- Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 870 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance or less than 75%survival rate). isdictional species list for appropriate plant replacements (See Appendix 3 - Bioretention Plant List,in the LID Tech- nical Guidance Manual for Puget Sound). l Confirm that plant selection is appro- priate for site grow- ing conditions l Consultation with a landscape architect is recommended for removal,transplant, or substitution of plants Vegetation (general)As needed Presence of dis- eased plants and plant mater- ial l Remove any dis- eased plants or plant parts and dispose of in an approved loc- ation (e.g.,com- mercial landfill)to avoid risk of spread- ing the disease to other plants l Disinfect gardening tools after pruning to prevent the spread of disease l See Pacific North- Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 871 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance west Plant Disease Management Hand- book for information on disease recog- nition and for addi- tional resources l Replant as neces- sary according to recommendations provided for "facility bottom area and upland slope veget- ation". Trees and shrubs All pruning seasons (tim- ing varies by species) Pruning as needed l Prune trees and shrubs in a manner appropriate for each species.Pruning should be performed by landscape pro- fessionals familiar with proper pruning techniques l All pruning of mature trees should be per- formed by or under the direct guidance of an ISA certified arborist A Large trees and shrubs interfere with operation of the facility or access for main- tenance l Prune trees and shrubs using most current ANSI A300 standards and ISA BMPs. l Remove trees and Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 872 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance shrubs,if necessary. Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 873 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance Fall and Spring Standing dead vegetation is present l Remove standing dead vegetation l Replace dead veget- ation within 30 days of reported dead and dying plants (as prac- tical depending on weather/planting sea- son) l If vegetation replace- ment is not feasible within 30 days,and absence of veget- ation may result in erosion problems, temporary erosion control measures should be put in place immediately. l Determine cause of dead vegetation and address issue,if pos- sible l If specific plants have a high mortality rate,assess the cause and replace with appropriate spe- cies.Consultation with a landscape architect is recom- mended. Fall and Planting l When working Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 874 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance Spring beneath mature trees around and below mature trees,follow the most current ANSI A300 stand- ards and ISA BMPs to the extent prac- ticable (e.g.,take care to minimize any damage to tree roots and avoid com- paction of soil). l Planting of small shrubs or ground- covers beneath mature trees may be desirable in some cases;such plant- ings should use mainly plants that come as bulbs,bare root or in 4-inch pots; plants should be in no larger than 1-gal- lon containers. Fall and Spring Presence of or need for stakes and guys (tree growth,mat- uration,and sup- port needs) l Verify location of facility liners and underdrain (if any) prior to stake install- ation in order to pre- vent liner puncture or pipe damage l Monitor tree support systems:Repair and adjust as needed to Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 875 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance provide support and prevent damage to tree. l Remove tree sup- ports (stakes,guys, etc.)after one grow- ing season or max- imum of 1 year. l Backfill stake holes after removal. Trees and shrubs adja- cent to vehicle travel areas (or areas where vis- ibility needs to be main- tained) A Vegetation causes some visibility (line of sight)or driver safety issues l Maintain appropriate height for sight clear- ance l When continued,reg- ular pruning (more than one time/grow- ing season)is required to maintain visual sight lines for safety or clearance along a walk or drive,consider relo- cating the plant to a more appropriate loc- ation. l Remove or trans- plant if continual safety hazard l Consultation with a landscape architect is recommended for removal,transplant, or substitution of Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 876 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance plants Flowering plants A Dead or spent flowers present Remove spent flowers (deadhead) Perennials Fall Spent plants Cut back dying or dead and fallen foliage and stems Emergent vegetation Spring Vegetation com- promises con- veyance Hand rake sedges and rushes with a small rake or fingers to remove dead foliage before new growth emerges in spring or earlier only if the foliage is blocking water flow (sedges and rushes do not respond well to pruning) Ornamental grasses (per- ennial) Winter and Spring Dead material from previous year's growing cycle or dead collapsed foliage l Leave dry foliage for winter interest l Hand rake with a small rake or fingers to remove dead foliage back to within several inches from the soil before new growth emerges in spring or earlier if the foliage collapses and is blocking water flow Ornamental grasses (ever- green) Fall and Spring Dead growth present in spring l Hand rake with a small rake or fingers to remove dead growth before new growth emerges in spring Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 877 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance l Clean,rake,and comb grasses when they become too tall l Cut back to ground or thin every 2-3 years as needed Noxious weeds M (March - October,pre- ceding seed dispersal) Listed noxious vegetation is present (refer to current county noxious weed list) l By law,class A &B noxious weeds must be removed, bagged and dis- posed as garbage immediately l Reasonable attempts must be made to remove and dispose of class C noxious weeds l It is strongly encour- aged that herbicides and pesticides not be used in order to protect water quality; use of herbicides and pesticides may be prohibited in some jurisdictions l Apply mulch after weed removal (see "Mulch") Weeds M (March - October,pre- ceding seed dispersal) Weeds are present l Remove weeds with their roots manually with pincer-type weeding tools,flame Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 878 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance weeders,or hot water weeders as appropriate l Follow IPM pro- tocols for weed man- agement (see "Additional Main- tenance Resources" section for more information on IPM protocols) Excessive vegetation Once in early to mid-May and once in early-to mid- September Low-lying veget- ation growing beyond facility edge onto side- walks,paths,or street edge poses ped- estrian safety hazard or may clog adjacent permeable pave- ment surfaces due to asso- ciated leaf litter, mulch,and soil l Edge or trim ground- covers and shrubs at facility edge l Avoid mechanical blade-type edger and do not use edger or trimmer within 2 feet of tree trunks l While some clip- pings can be left in the facility to replen- ish organic material in the soil,excessive leaf litter can cause surface soil clogging As needed Excessive veget- ation density inhibits storm- water flow bey- ond design ponding or l Determine whether pruning or other routine maintenance is adequate to main- tain proper plant density and aes- thetics Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 879 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance becomes a haz- ard for ped- estrian and vehicular cir- culation and safety l Determine if planting type should be replaced to avoid ongoing main- tenance issues (an aggressive grower under perfect grow- ing conditions should be trans- planted to a location where it will not impact flow) l Remove plants that are weak,broken or not true to form; replace in-kind l Thin grass or plants impacting facility function without leav- ing visual holes or bare soil areas l Consultation with a landscape architect is recommended for removal,transplant, or substitution of plants As needed Vegetation blocking curb cuts,causing excessive sed- iment buildup and flow bypass Remove vegetation and sediment buildup Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 880 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance Mulch Mulch Following weeding Bare spots (without mulch cover)are present or mulch depth less than 2 inches l Supplement mulch with hand tools to a depth of 2 to 3 inches l Replenish mulch per O&M manual.Often coarse compost is used in the bottom of the facility and arbor- ist wood chips are used on side slopes and rim (above typ- ical water levels) l Keep all mulch away from woody stems Watering Irrigation sys- tem (if any) Based on man- ufacturer's instructions Irrigation system present Follow manufacturer's instructions for O&M A Sprinklers or drip irrigation not dir- ected/located to properly water plants Redirect sprinklers or move drip irrigation to desired areas Summer water- ing (first year) Once every 1- 2 weeks or as needed during prolonged dry periods Trees,shrubs and ground- covers in first year of estab- lishment period l 10 to 15 gallons per tree l 3 to 5 gallons per shrub l 2 gallons water per square foot for groundcover areas Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 881 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance l Water deeply,but infrequently,so that the top 6 to 12 inches of the root zone is moist l Use soaker hoses or spot water with a shower type wand when irrigation sys- tem is not present o Pulse water to enhance soil absorption, when feasible o Pre-moisten soil to break surface tension of dry or hydro- phobic soils/mulch,fol- lowed by sev- eral more passes.With this method , each pass increases soil absorption and allows more water to infilt- rate prior to run- off l Add a tree bag or slow-release water- ing device (e.g., Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 882 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance bucket with a per- forated bottom)for watering newly installed trees when irrigation system is not present Summer water- ing (second and third years) Once every 2- 4 weeks or as needed during prolonged dry periods Trees,shrubs and ground- covers in second or third year of estab- lishment period l 10 to 15 gallons per tree l 3 to 5 gallons per shrub l 2 gallons water per square foot for groundcover areas l Water deeply,but infrequently,so that the top 6 to 12 inches of the root zone is moist l Use soaker hoses or spot water with a shower type wand when irrigation sys- tem is not present o Pulse water to enhance soil absorption, when feasible o Pre-moisten soil to break surface tension of dry or hydro- phobic soils/mulch,fol- Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 883 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance lowed by sev- eral more passes.With this method , each pass increases soil absorption and allows more water to infilt- rate prior to run- off Summer water- ing (after establishment) As needed Established vegetation (after 3 years) l Plants are typically selected to be drought tolerant and not require regular watering after estab- lishment;however, trees may take up to 5 years of watering to become fully established l Identify trigger mech- anisms for drought- stress (e.g.,leaf wilt, leaf senescence, etc.)of different spe- cies and water imme- diately after initial signs of stress appear l Water during drought conditions or more often if necessary to main- Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 884 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance tain plant cover Pest Control Mosquitoes B,S Standing water remains for more than 3 days after the end of a storm l Identify the cause of the standing water and take appropriate actions to address the problem (see "Ponded water") l To facilitate main- tenance,manually remove standing water and direct to the storm drainage system (if runoff is from non pollution- generating surfaces) or sanitary sewer system (if runoff is from pollution-gen- erating surfaces) after getting approval from san- itary sewer authority. l Use of pesticides or Bacillus thuring- iensis israelensis (Bti)may be con- sidered only as a temporary measure while addressing the standing water cause.If overflow to Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 885 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance a surface water will occur within 2 weeks after pesticide use, apply for coverage under the Aquatic Mosquito Control NPDES General Per- mit. Nuisance animals As needed Nuisance anim- als causing erosion,dam- aging plants,or depositing large volumes of feces l Reduce site con- ditions that attract nuisance species where possible (e.g., plant shrubs and tall grasses to reduce open areas for geese,etc.) l Place predator decoys l Follow IPM pro- tocols for specific nuisance animal issues (see "Addi- tional Maintenance Resources" section for more information on IPM protocols) l Remove pet waste regularly l For public and right- of-way sites con- sider adding garbage cans with dog bags for picking Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 886 Maintenance Component Recommended Fre- quency a Condition when Main- tenance is Needed (Stand- ards) Action Needed (Pro- cedures) Inspection Routine Main- tenance up pet waste. Insect pests Every site visit asso- ciated with vegetation management Signs of pests, such as wilting leaves,chewed leaves and bark, spotting or other indicators l Reduce hiding places for pests by removing diseased and dead plants l For infestations,fol- low IPM protocols (see "Additional Maintenance Resources" section for more information on IPM protocols) Note that the inspection and routine maintenance frequencies listed above are recom- mended by Ecology.They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater permittees for "stormwater treatment and flow control BMPs/facilities". a Frequency:A =Annually;B =Biannually (twice per year);M =Monthly;W =At least one visit should occur during the wet season (for debris/clog related maintenance,this inspection/maintenance visit should occur in the early fall,after deciduous trees have lost their leaves);S =Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). IPM -Integrated Pest Management ISA -International Society of Arboriculture Table V-4.5.2(21)Maintenance Standards -Bioretention Facilities (continued) Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance Surface/Wearing Course Permeable A,S Runoff from l Clean deposited soil or Table V-4.5.2(22)Maintenance Standards -Permeable Pavement 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 887 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance Pavements, all adjacent per- vious areas deposits soil, mulch or sed- iment on pav- ing other materials from per- meable pavement or other adjacent surfacing l Check if surface elevation of planted area is too high, or slopes towards pave- ment,and can be regraded (prior to regrading,protect permeable pavement by covering with temporary plastic and secure covering in place) l Mulch and/or plant all exposed soils that may erode to pavement surface Porous asphalt or pervious concrete A or B None (routine maintenance) Clean surface debris from pave- ment surface using one or a com- bination of the following methods: l Remove sediment,debris, trash,vegetation,and other debris deposited onto pave- ment (rakes and leaf blowers can be used for removing leaves) l Vacuum/sweep permeable paving installation using: o Walk-behind vacuum (sidewalks) o High efficiency regen- erative air or vacuum sweeper (roadways, parking lots) Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 888 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance o ShopVac or brush brooms (small areas) l Hand held pressure washer or power washer with rotat- ing brushes Follow equip- ment manufacturer guidelines for when equip- ment is most effective for cleaning permeable pave- ment.Dry weather is more effective for some equip- ment. Ab Surface is clogged:Pond- ing on surface or water flows off the per- meable pave- ment surface during a rain event (does not infiltrate) l Review the overall per- formance of the facility (note that small clogged areas may not reduce over- all performance of facility) l Test the surface infiltration rate using ASTM C1701 as a corrective maintenance indicator.Perform one test per installation,up to 2,500 square feet.Perform an additional test for each addi- tional 2,500 square feet up to 15,000 square feet total. Above 15,000 square feet, add one test for every 10,000 square feet. l If the results indicate an infiltration rate of 10 inches per hour or less,then per- form corrective main- Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 889 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance tenance to restore per- meability.To clean clogged pavement surfaces,use one or combination of the following methods: o Combined pressure wash and vacuum system calibrated to not dislodge wearing course aggregate. o Hand held pressure washer or power washer with rotating brushes o Pure vacuum sweep- ers Note:If the annual/biannual routine maintenance stand- ard to clean the pavement surface is conducted using equipment from the list above,corrective main- tenance may not be needed. A Sediment present at the surface of the pavement l Assess the overall per- formance of the pavement system during a rain event. If water runs off the pave- ment and/or there is pond- ing then see above. l Determine source of sed- iment loading and evaluate whether or not the source Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 890 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance can be reduced/eliminated. If the source cannot be addressed,consider increasing frequency of routine cleaning (e.g.,twice per year instead of once per year). Summer Moss growth inhibits infilt- ration or poses slip safety hazard l Sidewalks:Use a stiff broom to remove moss in the summer when it is dry l Parking lots and roadways: Pressure wash,vacuum sweep,or use a com- bination of the two for clean- ing moss from pavement surface.May require stiff broom or power brush in areas of heavy moss. A Major cracks or trip hazards and concrete spalling and raveling l Fill potholes or small cracks with patching mixes l Large cracks and set- tlement may require cutting and replacing the pave- ment section.Replace in- kind where feasible.Repla- cing porous asphalt with conventional asphalt is acceptable if it is a small percentage of the total facil- ity area and does not impact the overall facility function. l Take appropriate pre- Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 891 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance cautions during pavement repair and replacement efforts to prevent clogging of adjacent porous mater- ials Interlocking concrete paver blocks and aggreg- ate pavers A or B None (routine maintenance) Clean pavement surface using one or a combination of the fol- lowing methods: l Remove sediment,debris, trash,vegetation,and other debris deposited onto pave- ment (rakes and leaf blowers can be used for removing leaves) l Vacuum/sweep permeable paving installation using: o Walk-behind vacuum (sidewalks) o High efficiency regen- erative air or vacuum sweeper (roadways, parking lots) o ShopVac or brush brooms (small areas) Note:Vacuum settings may have to be adjusted to pre- vent excess uptake of aggregate from paver open- ings or joints.Vacuum sur- face openings in dry weather to remove dry, encrusted sediment. Ab Surface is l Review the overall per- Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 892 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance clogged:Pond- ing on surface or water flows off the per- meable pave- ment surface during a rain event (does not infiltrate) formance of the facility (note that small clogged areas may not reduce over- all performance of facility) l Test the surface infiltration rate using ASTM C1701 as a corrective maintenance indicator.Perform one test per installation,up to 2,500 square feet.Perform an additional test for each addi- tional 2,500 square feet up to 15,000 square feet total. Above 15,000 square feet, add one test for every 10,000 square feet. l If the results indicate an infiltration rate of 10 inches per hour or less,then per- form corrective main- tenance to restore permeability. l Clogging is usually an issue in the upper 2 to 3 centimeters of aggregate. Remove the upper layer of encrusted sediment,and fines,and/or vegetation from openings and joints between the pavers by mechanical means and/or suction equipment (e.g., pure vacuum sweeper). Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 893 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance b A Sediment present at the surface of the pavement l Assess the over- all per- formance of the pave- ment sys- tem during a rain event.If water runs off the pave- ment and/or there is ponding, then see above. l Determi- ne source of sed- iment loading and eval- uate whether or not the source can be Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 894 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance reduced/- elim- inated.If the source cannot be address- ed,con- sider increas- ing fre- quency of routine cleaning (e.g., twice per year instead of once per year). Summer Moss growth inhibits infilt- ration or poses slip safety hazard l Side- walks: Use a stiff broom to remove moss in the sum- mer when it is dry Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 895 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance l Parking lots and road- ways: Vacuum sweep or stiff broom/- power brush for cleaning moss from pave- ment sur- face A Paver block missing or damaged Remove indi- vidual dam- aged paver blocks by hand and replace or repair per man- ufacturer's recom- mendations A Loss of aggregate material between paver blocks Refill per man- ufacturer's recom- mendations for interlocking paver sec- tions A Settlement of May require Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 896 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance surface resetting Open-celled paving grid with gravel A or B None (routine maintenance) l Remove sediment,debris, trash,vegetation,and other debris deposited onto pave- ment (rakes and leaf blowers can be used for removing leaves) l Follow equipment man- ufacturer guidelines for cleaning surface. Ab Aggregate is clogged:Pond- ing on surface or water flows off the per- meable pave- ment surface during a rain event (does not infiltrate) l Use vacuum truck to remove and replace top course aggregate l Replace aggregate in pav- ing grid per manufacturer's recommendations A Paving grid missing or damaged l Remove pins,pry up grid segments,and replace gravel l Replace grid segments where three or more adja- cent rings are broken or damaged l Follow manufacturer guidelines for repairing sur- face. A Settlement of surface May require resetting A Loss of Replenish aggregate material by Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 897 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance aggregate material in paving grid spreading gravel with a rake (gravel level should be main- tained at the same level as the plastic rings or no more than 1/4 inch above the top of rings).See manufacturer's recom- mendations. A Weeds present l Manually remove weeds l Presence of weeds may indicate that too many fines are present (refer to Actions Needed under "Aggregate is clogged" to address this issue) Open-celled paving grid with grass A or B None (routine maintenance) l Remove sediment,debris, trash,vegetation,and other debris deposited onto pave- ment (rakes and leaf blowers can be used for removing leaves) l Follow equipment man- ufacturer guidelines for cleaning surface. Ab Aggregate is clogged:Pond- ing on surface or water flows off the per- meable pave- ment surface during a rain event (does not infiltrate) Rehabilitate per manufacturer's recommendations. Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 898 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance A Paving grid missing or damaged l Remove pins,pry up grid segments,and replace grass l Replace grid segments where three or more adja- cent rings are broken or damaged l Follow manufacturer guidelines for repairing sur- face. A Settlement of surface May require resetting A Poor grass coverage in paving grid l Restore growing medium, reseed or plant,aerate, and/or amend vegetated area as needed l Traffic loading may be inhibiting grass growth; reconsider traffic loading if feasible As needed None (routine maintenance) Use a mulch mower to mow grass A None (routine maintenance) l Sprinkle a thin layer of com- post on top of grass surface (1/2" top dressing)and sweep it in l Do not use fertilizer A Weeds present l Manually remove weeds l Mow,torch,or inoculate and replace with preferred vegetation Inlets/Outlets/Pipes Inlet/outlet A Pipe is dam-Repair/replace Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 899 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance pipe aged A Pipe is clogged Remove roots or debris Underdrain pipe Clean pipe as needed Clean orifice at least bian- nually (may need more frequent cleaning dur- ing wet sea- son) Plant roots, sediment or debris redu- cing capacity of underdrain (may cause prolonged drawdown period) l Jet clean or rotary cut debris/roots from under- drain(s) l If underdrains are equipped with a flow restrictor (e.g., orifice)to attenuate flows, the orifice must be cleaned regularly Raised sub- surface over- flow pipe Clean pipe as needed Clean orifice at least bian- nually (may need more frequent cleaning dur- ing wet sea- son) Plant roots, sediment or debris redu- cing capacity of underdrain l Jet clean or rotary cut debris/roots from under- drain(s) l If underdrains are equipped with a flow restrictor (e.g., orifice)to attenuate flows, the orifice must be cleaned regularly Outlet struc- ture A,S Sediment, vegetation,or debris redu- cing capacity of outlet struc- ture l Clear the blockage l Identify the source of the blockage and take actions to prevent future blockages Overflow B Native soil is exposed or other signs of erosion dam- age are present at dis- charge point Repair erosion and stabilize sur- face Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 900 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance Aggregate Storage Reservoir Observation port A,S Water remains in the storage aggregate longer than anticipated by design after the end of a storm If immediate cause of extended ponding is not identified,sched- ule investigation of subsurface materials or other potential causes of system failure. Vegetation Adjacent large shrubs or trees As needed Vegetation related fallout clogs or will potentially clog voids l Sweep leaf litter and sed- iment to prevent surface clogging and ponding l Prevent large root systems from damaging subsurface structural components Once in May and Once in September Vegetation growing bey- ond facility edge onto sidewalks, paths,and street edge Edging and trimming of planted areas to control groundcovers and shrubs from overreaching the sidewalks,paths and street edge improves appearance and reduces clogging of permeable pavements by leaf litter,mulch and soil. Leaves, needles, and organic debris In fall (Octo- ber to Decem- ber)after leaf drop (1-3 times, depending on canopy cover) Accumulation of organic debris and leaf litter Use leaf blower or vacuum to blow or remove leaves,ever- green needles,and debris (i.e., flowers,blossoms)off of and away from permeable pavement Note that the inspection and routine maintenance frequencies listed above are recom- Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 901 Component Recommended Fre- quency a Condition when Main- tenance is Needed (Standards) Action Needed (Procedures) Inspection Routine Maintenance mended by Ecology.They do not supersede or replace the municipal stormwater permit requirements for inspection frequency required of municipal stormwater permittees for "stormwater treatment and flow control BMPs/facilities". a Frequency:A=Annually;B=Biannually (twice per year);S =Perform inspections after major storm events (24-hour storm event with a 10-year or greater recurrence interval). b Inspection should occur during storm event. Table V-4.5.2(22)Maintenance Standards -Permeable Pavement (continued) 2014 Stormwater Management Manual for Western Washington Volume V -Chapter 4 -Page 902 P a g e | 27 B. Correspondence Ecology EPA Local Government P a g e | 28 C. Site Inspection Form Create your own or download Ecology’s template: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html Select Permit, Forms and Application to find the link to the Construction Stormwater Site Inspection Form. P a g e | 29 D. Construction Stormwater General Permit (CSWGP) Download the CSWGP: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html P a g e | 30 E. 303(d) List Waterbodies / TMDL Waterbodies Information Proposed New Discharge to an Impaired Water Body form SWPPP Addendum addressing impairment F. Contaminated Site Information The site is not contaminated G. Engineering Calculations The following calculations determine the size of the trap. Sediment Pond/Trap SA= FS (Q₂/ Vs) (Q₂) FS= 2 Factor of Safety Vs 0.00096 ft/sec Settling Velocity Q₂ 15-min Peak from WWHM3 WWHM Input Landcover Basin A Type (AC) Imp. Area 0.86 Grass 0.21 Total Area 1.07 Soil Type = Till Rainfall= Seatac 1.0 Used 15 min. Time series Results Basin A Q10 (cfs) 0.4852 SA (ft²) 1,011