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HomeMy WebLinkAboutRS_SWPPP_Skyhorse_210427_v1Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for Shyhorse Short Plat Prepared for: The Washington State Department of Ecology Northwest Regional Office 3190 160th Ave SE Bellevue, WA 98008 SDP2017-02556 Permittee / Owner Developer Operator / Contractor Newfourth LLC 19244 39th Avenue South Seatac, WA 98188 Newfourth LLC 19244 39th Avenue South Seatac, WA 98188 TBD Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Nicole Mecum Encompass Engineering & Surveying (425) 392-0250 SWPPP Preparation Date 10/14/2020 Project Construction Dates Activity / Phase Start Date End Date Site Grading To Be Determined To Be Determined DEVELOPMENT ENGINEERING Nathan Janders 04/12/2021 TABLE OF CONTENTS PROJECT INFORMATION (1.0) ..................................................................................... 4 CONSTRUCTION STORMWATER BEST MANAGEMENT PRACTICES (BMPS) (2.0) 9 POLLUTION PREVENTION TEAM (3.0) ...................................................................... 24 MONITORING AND SAMPLING REQUIREMENTS (4.0) ............................................. 25 DISCHARGES TO 303(D) OR TOTAL MAXIMUM DAILY LOAD (TMDL) WATERBODIES (5.0) ................................................................................................... 28 REPORTING AND RECORD KEEPING (6.0) ............................................................... 29 List of Tables 1. Summary of Site Pollutant Constituents 2. Pollutants 3. pH-Modifying Sources 4. Management 5. Team Information 6. Turbidity Sampling Method 7. pH Sampling Method List of Appendices A. Civil Site Plans B. BMP Detail C. Site Inspection Form D. CSWGP E. Engineering Calculations 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 Project Information (1.0) Project/Site Name: Skyhorse Short Plat Street/Location: 163XX SE 132nd Street City: Renton State: WA Zip code: 98059 Subdivision: N/A Receiving waterbody: Lower Cedar River and May Creek Existing Conditions (1.1) Total acreage: 3.3 AC Disturbed acreage: 3.0 AC Existing structures: There is an existing single-family residence located on the site. This structure is schedule to remain and is excluded from the project area. Landscape topography: Trees, brush, grass, lawn. Drainage patterns: The site is divided into two basins, reffered to as the north basin and south basin. The north basin drains to a large wetland and eventually to May Creek. The south basin drains to a stormwater pond and eventually to the Lower Cedar River. A full Level II Downstream Drainage Analysis has been prepared for the site and is included in Appendix B of the Technical Information Report. Existing Vegetation: Trees, brush, grass, lawn. Critical Areas: No known critical areas on or adjacent to the site. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: Bioassessment Table 1 includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration Gasoline Construction Vehicles Proposed Construction Activities (1.2) Description of site development: The proposed development will subdivide two existing parcels into 8 single-family residential lots. The proposal will include new right-of-way improvements on both SE 132nd Street and 164th Avenue SE. Description of construction activities: The project site will be cleared and graded prior to the start of construction. The development of the site will include site grading and utilities installation. Utilities will include stormwater, sanitary sewer, potable water, road development, and all private utilities. Description of site drainage including flow from and onto adjacent properties: A Level 2 Downstream Analysis from the engineering Technical Information Report has been included in this section. Level II Downstream Analysis Task 1: Study Area Definition and Maps The project site is split between two major basins, May Creek basin to the north and Lower Cedar River basin to the south. The north portion of the site drains to a large wetland located just south of SE 128th Street via existing conveyance systems in SE 132nd Street and 164th Avenue SE. The south portion of the site drains to a stormwater pond (King County Stormwater Facility D97367) located near Liberty High School. This drainage path conveys stormwater runoff through private properties to the pond, located approximately ¼ mile south of the site. Task 2: Resource Review The following resources were utilized for the downstream analysis: · Adapted Basin Plan – Based on the King County iMap website, the site borders two basins, May Creek and Lower Cedar River. · Floodplain/Floodway (FEMA) Maps – The site is not within a mapped 100-year floodplain. · Offsite Analysis Reports – The downstream analysis for Harmony Grove (Threadgill Plat) was used in assessing the downstream analysis for the south basin. · Sensitive Area Information – Based on the King County iMap website, the site is not located within a coal mine, 100-year floodplain, seismic, erosion, landslide, or wetland area. · King County iMap Drainage Complaints – Drainage Complaints from the King County iMap website and King County Water and Land Resources Division have been reviewed and utilized for this report. Task 3: Field Inspection On August 17, 2016 and November 11, 2016, field inspections were performed on the study area to locate any existing or potential problems. The following section (Task 4) of this report provides a detailed description of each drainage component in the downstream flowpath of the two basins. Task 4: Drainage System Description and Problem Descriptions The downstream conveyance systems are described below. Components of each system are itemized and illustrated in the offsite analysis drainage system tables. North Basin: The roadside ditch (Component 1 on North Offsite Analysis Drainage Table) in SE 132nd Street picks up the flows from the northern basin and conveys to east where the flow enters a 12” ADS pipe. The runoff is then routed to 164th Avenue SE via series of 12” ADS pipes and Type 1 catch basins. (Components 2 to 6) The flow then enters a roadside ditch near the intersection of SE 131st Place and 164th Avenue SE where it enters a 12” concrete pipe culvert (Component 8), crosses SE 131st Place and continues to flow north in a 12” ADS pipe (Component 9) The stormwater then enters a roadside ditch (Component 10) and travel north to a low point where it enters 12” concrete pipe culvert (Component 12) and crosses 164th Avenue SE. The stormwater then enters a wetland stream channel (Component 13) and flows north to the wetland area. The runoff from the wetland is discharged to a stream channel located just south of SE 128th Street and flows up north along the 164th Avenue SE (Components 15 and 16). South Basin: The runoff from the Basin S1 including the south portion of the site drains to a private open ditch located on the west property line of the parcel just south of the site. (Component 1 on South Offsite Analysis Drainage Table) The runoff then enters series of pipe system with Type I catch basins (Components 2 to 4) through private properties and connects to a Type I catch basin located on the north side of SE 135th Street. (Component 5) The flow then crosses SE 135th Street and enters a private 12” storm pipe. (Component 6) The stormwater is then routed to an open channel that carries flow to south where it connects to a stream channel in a forested area. (Components 7 and 8) The steam channel meanders through the forested area and enters 30” concrete culvert pipe located on the north property fence line of Liberty High School. (Component 9) The flow then enters a short stream channel with 30” CMP with trash rack (Component 11) and eventually ends up in the detention pond. (Component 12) The stream channel meanders through the forested area and enters a 30” concrete culvert located on the north property fence line of Liberty High School. (Component 9) The flows are then conveyed by a short stream channel before entering a 30” CMP culvert with trash rack (Component 11). This element outlets to the detention pond near Liberty High School. (Component 12) Existing Drainage Component Conditions: Drainage components in both basins were in good condition at the time of field inspection, and there were no signs of erosion or flooding in any of the drainage components. Besides the stream channels to the wetland and heavily forested areas, most of the ditches and catch basins were well maintained and no major sediment accumulations were observed. Capacity Analysis: Using the Ration Method, 25-year flows were determined and compared with the capacity of existing drainage components. Based on the Manning formula, a 12” diameter pipe sloped at 2 to 10 percent has conveyance capacity ranging from 5.46 to 12.21 CFS. The capacities for the open ditches in the north basin ranges from 40 to 167 CFS. Based on the capacity estimation above, south basin pipe components 2 to 6 meet the 25-year peak flow requirement. Downstream Drainage Complains: Drainage complaints along the downstream systems after 2006 were identified and obtained from King County Water and Land Resources Division. For the south basin, no drainage complains were identified for the ¼ mile reach. Five drainage complaints were identified for the north basin. (Refer to Appendix E for the copies of drainage complaints) Those complaints are mainly for the stream channel north of the wetland near SE 128th Street and mostly concerning high-water level of the channel due to beaver dam activities and debris blocking the culvert inlet. It is our opinion that those complaints can be addressed with regular maintenance and frequent inspection of the channel. With regular maintenance, no flooding or erosion problem is anticipated with the existing channel. Task 5: Mitigation of Existing and Potential Problems The downstream analysis shows that the project has a minor type 1 conveyance system nuisance problem. To mitigate the problem, the project will provide detention/wet vaults that meet the flow control duration standard matching forested conditions. The duration-matching criteria of the proposed detention/wet vaults prevent increases in overflow volume by maintaining or reducing the developed flow volumes to existing forested condition for peak flows rangin 50% of the 2-year up to the full 50-year. Description of final stabilization: Final stabilization will include revegetation and landscaping of exposed areas, as well as paving of roads and sidewalks. A full description can be seen in the landscape plan in the engineering plan sheets. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater: There are no known contaminated soils on site. Construction Stormwater Best Management Practices (BMPs) (2.0) 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. The 12 Elements (2.1) Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1) The limits of clearing and grading will be marked in several ways around the site depending on the location. Combination high visibility orange/silt fencing will be installed along clearing limits. Several trees and other areas of natural vegetation are scheduled to be retained on the site. Trees that are within the clearing limits will need to be protected with a tree protection fence. The development will employ the listed BMPs in order to protect vegetation from three kinds of injuries: Construction Equipment, Grade Changes, and Excavations. During the clearing effort, the topsoil and duff materials should be kept in a separate stockpile for future use to help promote grass growth during project close out. List and describe BMPs: BMP C101: Preserving Natural Vegetation BMP C103: High Visibility Fence BMP C233: Silt Fence Installation Schedules: Marking the clearing limits is one of the first things to be accomplished on the construction site. Prior to any site clearing or grading, areas that are to remain undisturbed during project construction shall be delineated. Once all plat construction is complete, leaving just the residences to be constructed, the clearing limit BMP’s may be removed as approved by the City. Portions of fencing may remain in place if the residence construction is scheduled to begin. Inspection and Maintenance plan: The clearing limits should be observed on a daily basis and thoroughly inspected weekly to ensure they are in place and functioning to protect areas that are not being cleared. If tree roots have been exposed or injured, “prune” cleanly with an appropriate pruning saw or loppers directly above the damaged roots and rcover with native soils. The uphill side of the fencing should be checked regularly for signs of clogging. Sediment deposits should be removed when the deposit reaches approximately one-third the height of the silt fence. Any damaged or missing portions of the clearing limit BMP’s should be repaired or replaced immediately. Responsible Staff: CESCL Element 2: Establish Construction Access (2.1.2) A stabilized construction entrance is proposed for this site. If construction vehicles are observed to be tracking soil onto the roads, the construction entrance will be maintained via the replacement/cleaning of the quarry spalls. If refreshment of the construction access proves ineffective, a wheel wash can be installed at the construction access. A gravel construction parking area is proposed for contractor staging. List and describe BMPs: BMP C105: Stabilized Construction Entrance BMP C107: Construction Road/Parking Area Stabilization Installation Schedules: The stabilized construction entrance should be established at the start of construction for all active access points. The construction road/parking area stabilization should be established after preliminary grading is completed. Inspection and Maintenance plan: The construction entrance will be observed daily for any deficiencies such as dirt or mud covering the rocks. Also, the public roads will be observed on a continual basis during vehicle exiting to ensure no soil deposits are being tracked onto the roadway. If the construction entrance proves inadequate to prevent soil from being deposited onto the roadway, additional measures will be necessary, including street sweeping and the use of a wheel wash for pervasive failures. Other stabilized areas will be inspected regularly, especially after large storm events. Any damaged or missing portions of the site BMP’s should be repaired or replaced immediately. Responsible Staff: CESCL Element 3: Control Flow Rates (2.1.3) At all times, flow rates shall be controlled for this project. Natural drainage patterns shall be protected as much as possible during construction, and concentrated flow should not be permitted. Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. The two stormwater detention/water quality vaults will be utilized as temporary sediment ponds. Prior to leaving the construction site, stormwater runoff will be directed to these facilities in order to control flow rates. Check dams and outlet protections will be utilized to reduce flow velocities and prevent scour. Will you construct stormwater retention and/or detention facilities? Yes No Two permanent stormwater detention/water quality vaults and associated infrastructure will be constructed on site. The vaults have been sufficiently sized to accommodate the devoped site flows. Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? Yes No List and describe BMPs: BMP C207: Check Dams BMP C209: Outlet Protection BMP C241: Temporary Sediment Pond Installation Schedules: Construction of the BMPs and associated infrastructure is scheduled for the beginning of the project. The measures described above are required throughout construction. Inspection and Maintenance plan: The BMPs should be inspected on a weekly basis to verify that the capacity has not diminished due to sedimentation in such a way that the BMP loses efficiency. Check dams shall be monitored for performance and sediment accumulation during and after each runoff producing rainfall. Sediment should be removed when it reaches one half the sump depth. Rock lining should be added as needed to maintain the intended function of the check dams and outlet protection. Sediment should be removed from the pond when it reaches 1-foot in depth. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 4: Install Sediment Controls (2.1.4) In order to minimize the discharge of pollutants, this project will utilize the listed sediment control BMPs. The two stormwater detention/water quality vaults will be utilized as temporary sediment ponds. Areas of disturbed soil shall be routed directly to the vaults before discharging from the site. Silt fencing, as well as interceptor swales will serve to convey flows to the sediment control BMPs. List and describe BMPs: BMP C233: Silt Fence BMP C241: Temporary Sediment Pond Installation Schedules: Implimentation of sediment control BMPs is scheduled for the beginning of the project. These BMPs will be functional before other land disturbing activities take place. The measures described above are required throughout construction. Inspection and Maintenance plan: The sediment control facilities should be inspected on a weekly basis to verify that the capacity has not diminished due to sedimentation in such a way that the BMP loses efficiency. The uphill side of the fencing should be checked regularly for signs of clogging. Sediment deposits should be removed when the deposit reaches approximately one-third the height of the silt fence. Sediment should be removed from the pond when it reaches 1-foot in depth. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 5: Stabilize Soils (2.1.5) Soils on site will be stabilized as appropriate through a variety of methods. These BMPs will be implemented when soil is to remain unworked or at the threat of rain throughout the project. Areas to be paved will be stabilized by the early application of a gravel base. Stock piles will be covered with plastic sheeting unless an extended period of storage is expected, in which case the stockpiles should be seeded and covered with mulch and an erosion control net. Runoff from plastic sheeting will be directed to an acceptable discharge location. During the hot summer months, dust control is necessary. This is accomplished by applying water to dry soils routinely. The water should not be applied in a way that creates runoff, however. 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: Spring 2020 End date: Spring 2022 Will you construct during the wet season? Yes No List and describe BMPs: BMP C101: Preserving Natural Vegetation BMP C120: Temporary and Permanent Seeding BMP C121: Mulching BMP C123: Plastic Covering BMP C140: Dust Control Installation Schedules: Soil Stabilization BMPs will be applied as deemed necessary. Exposed areas should be evaluated and covered to prevent impacts to roadways, drainage ways, or surface waters. Seeding shall be used throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. Inspection and Maintenance plan: Soil Stabilization BMPs should be reviewed daily and thoroughly inspected weekly and after each rainfall event to ensure they are functioning appropriately. All deficiencies shall be repaired or replaced in accordance with the number of days exposed soils may be left exposed. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 6: Protect Slopes (2.1.6) The steepest slopes existing on the site are located in the northeastern edge of the construction area. All slopes created on the site will be stabilized upon completion of grading with a combination of hydroseed and mulch. Seeding will be utilized on disturbed areas that have reached final grade of that will remain unworked for more than 30 days. 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 Installation Schedules: Slopes are to be protected throughout construction. Inspection and Maintenance plan: Stabilized slopes created during construction should be inspected on a weekly basis and after every rainfall event. Repairs to stabilization BMPs should be made in accordance to the exposed soils schedule. Areas that fail to establish at least 80 percent cover will be reseeded as necessary. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 7: Protect Drain Inlets (2.1.7) Catch basin inserts will be installed on all onsite and downstream catch basins. List and describe BMPs: BMP C220: Storm Drain Inlet Installation Schedules: Storm drain inlets are to be installed prior to the start of construction for all existing inlets. Constructed onsite catch basins will be protected prior to the first gravel lift. Inspection and Maintenance plan: All facilities should be inspected weekly and after every rainfall event. BMPs showing 1/3 of their capacity full of sediment should have the sediment removed or the unit replaced. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 8: Stabilize Channels and Outlets (2.1.8) A permanent drainage system will be constructed to convey flows to the stormwater detention/water quality vaults. Runoff will be directed to these BMPs via a series of temporary interceptor swales and culverts. The swales will be constructed with a check dams to reduce the stormwater flow velocities. Outlet protection in the form of riprap pads have been included at applicable locations to reduce flow velocities and scouring. List and describe BMPs: BMP C207: Check Dams BMP C209: Outlet Protection Installation Schedules: Stabilization BMPs are to be implemented after temporary channels are constructed. Channel lining shall be used if other measures prove insufficient for stabilization. Inspection and Maintenance plan: Check dams shall be monitored for performance and sediment accumulation during and after each runoff producing rainfall. Sediment should be removed when it reaches one half the sump depth. Rock lining should be added as needed to maintain the intended function of the check dams and outlet protection. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 9: Control Pollutants (2.1.9) The following pollutants are anticipated to be present on-site: Table 2 – Pollutants Pollutant (and source, if applicable) Gasoline in vehicles Concrete poured in place There are no known pollutants contained on the existing site. During construction, the contractor will need to conduct maintenance, fueling, and repair of heavy equipment and vehicles at the designated gravel contractor parking area, as spills of hazardous materials could result in an environmental event. If a wheel wash is incorporated into the protection plan, the contractor will discharge wheel wash wastewater to a separate on-site treatment system that prevents discharge to surface water, such as closed-loop recirculation or upland land application, or to the sanitary sewer, with local sewer district approval. Concrete will be handled in ways to eliminate concrete, concrete process water, and concrete slurry from entering waters of the state. List and describe BMPs: BMP C151: Concrete Handling BMP C152: Sawcutting and Surfacing Pollution Prevention BMP C153: Material Delivery, Storage and Containment BMP C154: Concrete Washout Area Installation Schedules: BMPs will be implemented at the beginning of construction and as needed throughout the project. Concrete washout BMPs shall be in place prior to the commencement of concrete work. Inspection and Maintenance plan: Inspection of the concrete washout area should be done weekly and prior to expected concrete pours. Washout facilities must be cleaned, or new facilities must be constructed and ready for use one the washout is 75% full. Secondary containment facilities should be inspected daily and repaired or replaced as necessary. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No List and describe BMPs: BMP C153: Material Delivery, Storage and Containment Installation Schedules: Containment of hazardous materials will be conducted throughout the duration of construction. Inspection and Maintenance plan: Containment facilities should be inspected daily and repaired or replaced as necessary. Material storage areas shall be kept clean, organized and equipped with an ample supply of appropriate spill clean-up material. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Will wheel wash or tire bath system BMPs be used during construction? Yes No List and describe BMPs: None Installation Schedules: N/A Inspection and Maintenance plan: N/A Responsible Staff: CESCL Will pH-modifying sources be present on-site? Yes No If yes, check the source(s). Table 3 – pH-Modifying Sources None X Bulk cement Cement kiln dust Fly ash Other cementitious materials X New concrete washing or curing waters X Waste streams generated from concrete grinding and sawing Exposed aggregate processes X Dewatering concrete vaults X Concrete pumping and mixer washout waters Recycled concrete Other (i.e. calcium lignosulfate) [please describe] During this construction activity, the pH levels of stormwater runoff must be monitored. If pH levels exceed 8.5, the level will need to be corrected. The use of CO2 per WDOE standards will rapidly neutralize the water and make it suitable for discharge. List and describe BMPs: BMP C252 High pH Neutralization using CO2 Installation Schedules: pH neutralization using CO2 will be implemented as necessary to correct pH levels in excess of 8.5. Inspection and Maintenance plan: Operators will keep written records related to treatment as detailed in the Stormwater Management Manual for Western Washington. A copy of this record should be given to the client/contractor who should retain the record for three years. Responsible Staff: CESCL 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. Element 10: Control Dewatering (2.1.10) The proposed stormwater detention/water quality vaults will require dewatering during the construction process. Dewatering water will be discharged via one of the approved treatment or disposal options by the Washington DOE. Discharges can be directed through existing vegetation or vegetative filtration areas as long as runoff does not occur. List and describe BMPs: BMP C236: Vegetative Filtration Installation Schedules: Dewatering BMPs will be established prior to the commencement of dewatering activities. Inspection and Maintenance plan: Containment facilities should be inspected regularly and repaired or replaced as necessary. Any damaged or missing portions of the site BMPs should be repaired or replaced immediately. Responsible Staff: CESCL Element 11: Maintain BMPs (2.1.11) 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 will 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 will be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed and the facility will be returned to conditions specified in the construction documents. Element 12: Manage the Project (2.1.12) 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. Table 4 – Management X Design the project to fit the existing topography, soils, and drainage patterns X Emphasize erosion control rather than sediment control Minimize the extent and duration of the area exposed X Keep runoff velocities low X Retain sediment on-site X Thoroughly monitor site and maintain all ESC measures Schedule major earthwork during the dry season Other (please describe) Element 13: Protect Low Impact Development (LID) BMPs (2.1.13) The proposed project will not incorporate LID BMPs. No protection is required for this BMP. Pollution Prevention Team (3.0) Table 5 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD TBD Resident Engineer Nicole Mecum (425) 392-0250 Emergency Ecology Contact TBD TBD Emergency Permittee/ Owner Contact Steve Beck (425) 444-0461 Non-Emergency Owner Contact Steve Beck (425) 444-0461 Monitoring Personnel TBD TBD Ecology Regional Office Northwest (425) 649-7000 Monitoring and Sampling Requirements (4.0) 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 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. Complete the following paragraph for sites that discharge to impaired waterbodies for fine sediment, turbidity, phosphorus, or pH: The receiving waterbody, Lower Cedar River and May Creek, are impaired for: Temperature, Chlorpyrifos, Dissolved Oxygen, pH, Bioassessment and DDT. All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for pH and/or 25 NTU for turbidity. Site Inspection (4.1) 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. Stormwater Quality Sampling (4.2) Turbidity Sampling (4.2.1) 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: Table 6 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) X 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. 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. https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue · Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 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. pH Sampling (4.2.2) pH monitoring is required for “Significant concrete work” (i.e. greater than 1000 cubic yards poured concrete or recycled concrete over the life of the project).The use of 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: Table 7 – pH Sampling Method pH meter X pH test kit Wide range pH indicator paper Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies (5.0) 303(d) Listed Waterbodies (5.1) Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No List the impairment(s): N/A The receiving waterbodies, Lower Cedar River and May Creek, are impaired for: Temperature. All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for pH and/or 25 NTU for turbidity. TMDL Waterbodies (5.2) Waste Load Allocation for CWSGP discharges: No known waste load allocation for CWSGP discharges. The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water Body form is included in Appendix F. Reporting and Record Keeping (6.0) Record Keeping (6.1) Site Log Book (6.1.1) 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 Records Retention (6.1.2) 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. Updating the SWPPP (6.1.3) 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. Reporting (6.2) Discharge Monitoring Reports (6.2.1) 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. Notification of Noncompliance (6.2.2) 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. 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. Appendix/Glossary A. Civil Site Plans B. BMP Detail C. Site Inspection Form Construction Stormwater Site Inspection Form Page 1 Project Name Skyhorse Short Plat Permit # Inspection Date Time Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre Print Name: Approximate rainfall amount since the last inspection (in inches): Approximate rainfall amount in the last 24 hours (in inches): Current Weather Clear Cloudy Mist Rain Wind Fog A. Type of inspection: Weekly Post Storm Event Other B. Phase of Active Construction (check all that apply): Pre Construction/installation of erosion/sediment controls Clearing/Demo/Grading Infrastructure/storm/roads Concrete pours Vertical Construction/buildings Utilities Offsite improvements Site temporary stabilized Final stabilization C. Questions: 1. Were all areas of construction and discharge points inspected? Yes No 2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No 3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No 4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No 5. If yes to #4 was it reported to Ecology? Yes No 6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken, and when. *If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33 cm or greater. Sampling Results: Date: Parameter Method (circle one) Result Other/Note NTU cm pH Turbidity tube, meter, laboratory pH Paper, kit, meter Construction Stormwater Site Inspection Form Page 2 D. Check the observed status of all items. Provide “Action Required “details and dates. Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 1 Clearing Limits Before beginning land disturbing activities are all clearing limits, natural resource areas (streams, wetlands, buffers, trees) protected with barriers or similar BMPs? (high visibility recommended) 2 Construction Access Construction access is stabilized with quarry spalls or equivalent BMP to prevent sediment from being tracked onto roads? Sediment tracked onto the road way was cleaned thoroughly at the end of the day or more frequent as necessary. 3 Control Flow Rates Are flow control measures installed to control stormwater volumes and velocity during construction and do they protect downstream properties and waterways from erosion? If permanent infiltration ponds are used for flow control during construction, are they protected from siltation? 4 Sediment Controls All perimeter sediment controls (e.g. silt fence, wattles, compost socks, berms, etc.) installed, and maintained in accordance with the Stormwater Pollution Prevention Plan (SWPPP). Sediment control BMPs (sediment ponds, traps, filters etc.) have been constructed and functional as the first step of grading. Stormwater runoff from disturbed areas is directed to sediment removal BMP. 5 Stabilize Soils Have exposed un-worked soils been stabilized with effective BMP to prevent erosion and sediment deposition? Construction Stormwater Site Inspection Form Page 3 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 5 Stabilize Soils Cont. Are stockpiles stabilized from erosion, protected with sediment trapping measures and located away from drain inlet, waterways, and drainage channels? Have soils been stabilized at the end of the shift, before a holiday or weekend if needed based on the weather forecast? 6 Protect Slopes Has stormwater and ground water been diverted away from slopes and disturbed areas with interceptor dikes, pipes and or swales? Is off-site storm water managed separately from stormwater generated on the site? Is excavated material placed on uphill side of trenches consistent with safety and space considerations? Have check dams been placed at regular intervals within constructed channels that are cut down a slope? 7 Drain Inlets Storm drain inlets made operable during construction are protected. Are existing storm drains within the influence of the project protected? 8 Stabilize Channel and Outlets Have all on-site conveyance channels been designed, constructed and stabilized to prevent erosion from expected peak flows? Is stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream conveyance systems? 9 Control Pollutants Are waste materials and demolition debris handled and disposed of to prevent contamination of stormwater? Has cover been provided for all chemicals, liquid products, petroleum products, and other material? Has secondary containment been provided capable of containing 110% of the volume? Were contaminated surfaces cleaned immediately after a spill incident? Were BMPs used to prevent contamination of stormwater by a pH modifying sources? Construction Stormwater Site Inspection Form Page 4 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 9 Cont. Wheel wash wastewater is handled and disposed of properly. 10 Control Dewatering Concrete washout in designated areas. No washout or excess concrete on the ground. Dewatering has been done to an approved source and in compliance with the SWPPP. Were there any clean non turbid dewatering discharges? 11 Maintain BMP Are all temporary and permanent erosion and sediment control BMPs maintained to perform as intended? 12 Manage the Project Has the project been phased to the maximum degree practicable? Has regular inspection, monitoring and maintenance been performed as required by the permit? Has the SWPPP been updated, implemented and records maintained? 13 Protect LID Is all Bioretention and Rain Garden Facilities protected from sedimentation with appropriate BMPs? Is the Bioretention and Rain Garden protected against over compaction of construction equipment and foot traffic to retain its infiltration capabilities? Permeable pavements are clean and free of sediment and sediment laden- water runoff. Muddy construction equipment has not been on the base material or pavement. Have soiled permeable pavements been cleaned of sediments and pass infiltration test as required by stormwater manual methodology? Heavy equipment has been kept off existing soils under LID facilities to retain infiltration rate. E. Check all areas that have been inspected. All in place BMPs All disturbed soils All concrete wash out area All material storage areas All discharge locations All equipment storage areas All construction entrances/exits Construction Stormwater Site Inspection Form Page 5 F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number; be specific on location and work needed. Document, initial, and date when the corrective action has been completed and inspected. Element # Description and Location Action Required Completion Date Initials Attach additional page if needed Sign the following certification: “I certify that this report is true, accurate, and complete, to the best of my knowledge and belief” Inspected by: (print) (Signature) Date: Title/Qualification of Inspector: D. Construction Stormwater General Permit (CSWGP) (To be included once CSWGP is issued.) E. Engineering Calculations (Included in the Technical Information Report.)