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SWPPP (2)Construction Stormwater Pollution Prevention Plan (SWPPP) for Mountain Meadows 8818 Burnett Rd. SE Yelm, WA 98594 TPN 21713310400 & 21713310402 City of Yelm Project No. 2020.0341 Olympic Engineering Project No. 21045 August 29, 2021 Prepared by: PO Box 12690 Olympia WA 98508 360.705.2474 www.olyeng.com Page 1 of 14 Certified Erosion and Sediment Control Lead (CESCL) _______________________________ _______________________________ _______________________________ _______________________________ Civil Engineer Chris Merritt, PE Principal Engineer Olympic Engineering, Inc. PO Box 12690 Olympia, WA 98508 (360) 705-2474 chris@olyeng.com Applicant Copper Ridge, LLC Attn: Evan Mann PO Box 73790 Puyallup, WA 98373 (253) 820-7835 Contractor _______________________________ _______________________________ _______________________________ _______________________________ This SWPPP has been prepared by Olympic Engineering based on our estimate of anticipated site conditions throughout construction along with anticipated construction methods and sequencing used by the contractor. The BMP’s suggested in this SWPPP are simply suggestions and the contractor and/or owner is responsible for implementing all BMPs necessary to minimize and prevent erosion and sedimentation throughout construction and through final site stabilization. The owner retains the ultimate responsibility for environmental protection at the site and for ensuring the project is in compliance at all times. 8/29/2021 “I hereby state that this Construction SWPPP for the Mountain Meadows project has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community for professional engineers. I understand that the City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities designed by me." Page 2 of 14 Project Overview The proposal is to subdivide a 4.4-acre parcel into 22 single-family residential lots with associated public roadway, private/public utilities, grading, and storm drainage improvements. The project will be completed in one phase. It is anticipated that construction will begin in fall 2021 with substantial completion by spring/summer 2022. Proposed Stormwater BMP’s: • All disturbed areas not being covered with a hard surface and/or all new lawn and landscape areas will contain soils meeting the Post-Construction Soil Quality and Depth (BMP T5.13) requirements. • Stormwater runoff from the new roadway areas will be collected and tightlined to a Type 2 catch basin containing Baysaver Bayfilter™ cartridges for runoff treatment. Treated stormwater runoff will be conveyed to a below-grade infiltration trench (BMP T7.20) for storage and 100% infiltration. • Stormwater runoff from the roof areas will be tightlined to individual lot Downspout Infiltration Trenches (BMP T5.10A) for storage and 100% infiltration. • Stormwater runoff from the individual lot driveway, walkway, and patio areas will be sheet flow dispersed onto adjacent vegetation (BMP T5.12). The project site is bounded by Burnett Rd. SE to the west; by undeveloped parcels to the east and north; and by developed residential parcels to the south. Topography generally slopes down from east to west at an average slope of approximately 2-3%. Site vegetation consists mainly of pasture grasses and scotch bloom with a few conifer trees located mainly in the southwestern portion of the site. The site and surrounding area are located in a Category I Critical Aquifer Recharge Area (CARA). All stormwater management BMP’s will meet or exceed DDECM requirements. The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston County classifies the on-site and surrounding area soils as Spanaway Gravelly Sandy Loam (HSG A). A Soils Report was prepared by Parnell Engineering, dated September 18, 2020 and the soils encountered were consistent with the Spanaway classification. There are no known critical areas (e.g. wetlands, steep slopes, streams, etc.) on-site or within the immediate vicinity of the site based on review of Thurston County critical areas maps. Per FEMA FIRM Map Panel #53045C0335E, the project site and surrounding areas are within Zone X. The Zone X designation signifies areas that are outside of the 0.2% annual chance floodplain. Objective To control erosion and prevent sediment and other pollutants from leaving the site during the construction phase of a project. To have fully functional stormwater facilities and BMPs for the developed site upon completion of construction. Page 3 of 14 Supplemental Guidelines If a Construction SWPPP is found to be inadequate (with respect to erosion and sediment control requirements), then the Plan Approval Authority within the City shall require that other BMPs be implemented, as appropriate. The Plan Approval Authority may allow development of generic Construction SWPPP’s that apply to commonly conducted public road activities, such as road surface replacement, that trigger this core requirement. They may also develop an abbreviated SWPPP format for project sites that will disturb less than 1 acre. Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The local permitting authority shall take enforcement action - such as a notice of violation, administrative order, penalty, or stop-work order under the following circumstances: • If, during the course of any construction activity or soil disturbance during the seasonal limitation period, sediment leaves the construction site causing a violation of the surface water quality standard; or • If clearing and grading limits or erosion and sediment control measures shown in the approved plan are not maintained. General Requirements Clearing and grading activities for developments shall be permitted only if conducted pursuant to an approved site development plan (e.g., subdivision approval) that establishes permitted areas of clearing, grading, cutting, and filling. These permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree retention areas shall be delineated on the site plans and the development site. The SWPPP shall be implemented beginning with initial land disturbance and until final stabilization. Sediment and Erosion control BMPs shall be consistent with the BMPs contained in Chapter II-4 of Volume II of the WSDOE Stormwater Management Manual for Western Washington (SWMMWW), 2019 ed. Seasonal Work Limitations - From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the site. See Element #12 below for additional information. Project Requirements - Construction SWPPP Elements In most cases, all of the following elements shall apply and be implemented throughout construction. Self-contained sites (discharges only to groundwater) must comply with all elements with the exception of Element 3: Control Flow Rates. Page 4 of 14 The suggested BMPs underlined and in bold are proposed for use in all phases of construction. Additional BMP’s shall be implemented as necessary to minimize and prevent erosion and sedimentation throughout construction. See Volume II of the SWMMWW for reference. All BMP’s shall be maintained until final site stabilization. Element #1: Preserve Vegetation/Mark Clearing Limits • Prior to beginning land disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. These shall be clearl y marked, both in the field and on the plans, to prevent damage and offsite impacts. • Clearly visible plastic, metal, or stake wire fence may be used to mark the clearing limits. • The duff layer, native topsoil, and natural vegetation shall be retained in an undisturbed state to the maximum degree practicable. If it is not practicable to retain the duff layer in place, stockpile it on-site, cover it to prevent erosion, and replace it immediately upon completion of the ground disturbing activities. Suggested BMPs: o BMP C100: Preservation of Native Topsoil (On-site) o BMP C101: Preserving Natural Vegetation (On-site) o BMP C102: Buffer Zones o BMP C103: High Visibility Plastic Fence. o BMP C233: Silt Fence Element #2: Establish Construction Access • Limit construction vehicle access and exit to one route, if possible, or two for linear projects such as roadways where more than one access is necessary for large equipment maneuvering. • Stabilize access points with a pad of quarry spalls or crushed rock, or equivalent BMP prior to traffic leaving the construction site to minimize the tracking of sediment onto public roads. • Wheel wash or tire baths should be located on site, if the stabilized construction entrance is not effective in preventing sediment from being tracked on public roads. • If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example during wet weather) to prevent sediment from entering waters of the state. Remove sediment from roads by shoveling or pickup sweeping and transport to a controlled sediment disposal area. Street washing is allowed only after sediment is removed in this manner. • Control street wash wastewater by pumping back on site to an approved infiltration facility, or otherwise preventing it from discharging into systems tributary to the city municipal separated storm sewer system, wetlands, or waters of the State. Other options include discharge to the sanitary sewer, or discharge to an approved offsite treatment system. For discharges to the sanitary sewer, permits must be obtained from the local jurisdiction providing the sewer. Element #3: Control Flow Rates • Protect properties and waterways downstream from development sites from erosion and the associated discharge of turbid waters due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. Page 5 of 14 • Downstream anal ysis is necessary if changes in offsite flows could impair or alter conveyance systems, stream banks, bed sediment, or aquatic habitat. See Volume I, Chapter 2, for potential offsite analysis requirements and guidelines (Core Requirement #11). • Where necessary to comply with Core Requirement #7, construct stormwater retention/detention facilities as one of the first steps in grading. Ensure that detention facilities are functional prior to construction of site improvements (e.g., impervious surfaces). • Outlet structures designed for permanent detention ponds are not appropriate for use during construction without modification. If used during construction, install an outlet structure that will allow for long-term storage of runoff and enable sediment to settle. Verify that the pond is sized appropriately for this purpose. Restore ponds to their original design dimensions, remove sediment, and install a final outlet structure at completion of the project. • Sites that must implement flow control (Core Requirement #7) for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre-developed condition for the range of pre-developed discharge rates from ½ of the 2-year flow through the 10-year flow as predicted by an approved continuous runoff model. Match the pre-developed condition to the land cover condition immediately prior to the development project. • The City may require pond designs that provide additional or different stormwater flow control if necessary to address local conditions or to protect properties and waterways downstream from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. • If permanent infiltration ponds are used for flow control during construction, protect them from siltation during the construction phase. Suggested BMPs: o BMP C203: Water Bars o BMP C207: Check Dams o BMP C209: Outlet Protection o BMP C235: Wattles o BMP C240: Sediment Trap o BMP C241: Temporary Sediment Pond o Refer to Volumes III and V for site suitability and sizing for infiltration facilities and for design of Detention and Infiltration Facilities for flow control. Element #4: Install Sediment Controls • Prior to leaving a construction site or prior to discharge to an infiltration facility, pass stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP. • Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet the flow control performance standard of Element #3, the first bullet. Full stabilization means concrete or asphalt paving; quarry spalls used as ditch lining; or the use of rolled erosion products, a bonded fiber matrix product, or vegetative cover in a manner that will fully prevent soil erosion. The City shall inspect and approve areas fully stabilized by means other than pavement or quarry spalls. • Construct sediment ponds, vegetated buffer strips, sediment barriers or filters, dikes, and other BMPs intended to trap sediment on site as one of the first steps in grading. Ensure that these BMPs are functional before other land disturbing activities take place. • Where feasible, design outlet structures that withdraw impounded water from the surface to avoid discharging sediment that is still suspended lower in the water column. • Seed and mulch earthen structures such as dams, dikes, and diversions according to the timing indicated in Element #5. Page 6 of 14 • Locate BMPs intended to trap sediment on site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages, often during non-storm events, in response to rain event changes in stream elevation or wetted area. • If installing a floating pump structure, include a stopper to prevent the pump basket from hitting the bottom of the pond. Suggested BMPs: o BMP C231: Brush Barrier o BMP C232: Gravel Filter Berm o BMP C233: Silt Fence o BMP C234: Vegetated Strip o BMP C235: Wattles o BMP C240: Sediment Trap o BMP C241: Temporary Sediment Pond o BMP C250: Construction Stormwater Chemical Treatment o BMP C251: Construction Stormwater Filtration. Element #5: Stabilize Soils • Stabilize all exposed and un-worked soils by application of effective BMPs that prevent erosion; protect the soil from the erosive forces of raindrop impact, flowing water, and wind. • Control stormwater volume and velocity within the site to minimize erosion; and control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize erosion at outlets and to minimize downstream channel and stream bank erosion. • From October 1 through April 30, no soils shall remain exposed and un-worked for more than 2 days. From May 1 to September 30, no soils shall remain exposed and un-worked for more than 7 days. This condition applies to all soils on site, whether at final grade or not. These time limits may be adjusted by the City if it can be shown that the average time between storm events justifies a different standard. • Stabilize soils at the end of the shift before a holiday or weekend if the weather forecast calls for precipitation. Applicable practices include, but are not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, soil application of polyacrylamide (PAM), the early application of gravel base on areas to be paved, and dust control. • Soil stabilization measures should be appropriate for the time of year, site conditions, estimated duration of use, and potential water quality impacts that stabilization agents may have on downstream waters or ground water. • Soil stockpiles must be stabilized from erosion, protected with sediment trapping measures, and when possible, be located away from storm drain inlets, waterways and drainage channels. • Minimize the amount of soil exposed during construction activity. • Minimize the disturbance of steep slopes. • Minimize soil compaction and, unless infeasible, preserve topsoil. • Ensure that gravel base used for stabilization is clean and does not contain fines or sediment. • Linear construction activities, including right-of-way and easement clearing, roadway development, pipelines, and trenching for utilities, shall be conducted to meet the soil stabilization requirements and time periods set forth above. Page 7 of 14 Suggested BMPs: o BMP C120: Temporary and Permanent Seeding o BMP C121: Mulching o BMP C122: Nets and Blankets o BMP C123: Plastic Covering o BMP C124: Sodding o BMP C125: Topsoiling/Composting o BMP C126: Polyacrylamide for Soil Erosion Protection o BMP C130: Surface Roughening o BMP C131: Gradient Terraces o BMP C140: Dust Control Element #6: Protect Slopes • Design and construct cut and fill slopes in a manner that will minimize erosion. • Consider soil type and its potential for erosion. • Reduce slope runoff velocities by reducing the length of continuous slope with terracing and diversions, reducing slope steepness, and roughening slope surface. • Divert offsite stormwater (run-on) or ground water away from slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Manage offsite stormwater separately from stormwater generated on the site. • At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent erosion. • Design temporary pipe slope drains to handle the peak 10-minute velocity of flow from a 10- year, 24-hour event assuming a Type 1A rainfall distribution. Alternatively, the 10-year, 1 hour flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may be used. If a 15-minute (or less) time step is used, no correction factor is required. The hydrologic analysis shall use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis shall use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas shall be modeled as “landscaped” area. • Permanent pipe slope drains shall be sized for the 100-year, 24-hour event. • Provide drainage to remove ground water intersecting the slope surface of exposed soil areas. • Place excavated material on the uphill side of trenches, consistent with safety and space considerations. • Place check dams at regular intervals within channels that are cut down a slope. • Stabilize soils on slopes, as specified in Element #5. • BMP combinations are the most effective method of protecting slopes with disturbed soils. For example, using both mulching and straw erosion control blankets in combination. Suggested BMPs: o BMP C120: Temporary and Permanent Seeding o BMP C121: Mulching o BMP C122: Nets and Blankets o BMP C123: Plastic Covering o BMP C124: Sodding o BMP C130: Surface Roughening o BMP C131: Gradient Terraces o BMP C200: Interceptor Dike and Swale o BMP C201: Grass-Lined Channels Page 8 of 14 o BMP C203: Water Bars o BMP C204: Pipe Slope Drains o BMP C205: Subsurface Drains o BMP C206: Level Spreader o BMP C207: Check Dams o BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam). Element #7: Protect Drain Inlets • Protect all storm drain inlets made operable during construction so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. • Keep all approach roads clean. Do not allow sediment and street wash water to enter storm drains without prior and adequate treatment unless treatment is provided before the storm drain discharges to waters of the state. • Inspect inlets weekly at a minimum and daily during storm events. Clean inlet protection devices, or remove and replace when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer). Suggested BMPs: o BMP C220: Storm Drain Inlet Protection Element #8: Stabilize Channels and Outlets • Design, construct, and stabilize all temporary on-site conveyance channels to prevent erosion from the expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24- hour frequency storm. Alternatively, the 10-year, 1-hour time step flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may be used. If a 15- minute (or less) time step is used, no correction factor is required. The hydrologic analysis shall use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis shall use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas shall be modeled as “landscaped” area. • Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent streambanks, slopes, and downstream reaches at the outlets of all conveyance systems. • The best method for stabilizing channels is to completely line the channel with a blanket product first, then add check dams as necessary to function as an anchor and to slow the flow of water. Suggested BMPs: o BMP C122: Nets and Blankets o BMP C202: Channel Lining o BMP C207: Check Dams o BMP C209: Outlet Protection Page 9 of 14 Element #9: Control Pollutants • Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. • Handle and dispose all pollutants, including waste materials and demolition debris that occur on-site, in a manner that does not cause contamination of stormwater. Woody debris may be chipped, ground, or chopped and spread on site. • Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. On-site fueling tanks shall include secondary containment. Secondary containment means placing tanks or containers within an impervious structure capable of containing 110% of the volume contained in the largest tank within the containment structure. Double- walled tanks do not require additional secondary containment. • Use spill prevention and control measures when conducting fueling, maintenance and repair of heavy equipment and vehicles including oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff. Clean contaminated surfaces immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. • Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that prevents discharge to surface water, such as a closed-loop recirculation or upland land application, or to the sanitary sewer, with local sewer district approval. • Apply agricultural chemicals, including fertilizers and pesticides, in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Follow manufacturers’ recommendations for application rates and procedures shall be followed. • Use BMPs to prevent or treat contamination of stormwater runoff by pH modifying sources. These acidic or basic sources include, but are not limited to, bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete pumping and mixer washout waters. • Adjust the pH of stormwater if necessary to prevent violations of the water quality standards. Projects must obtain written approval from the Department of Ecology prior to using chemical treatment other than CO2 or dry ice to adjust pH. • Washout of concrete trucks shall be performed off-site or in designated concrete washout areas onl y. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge to surface waters of the State if prohibited. Do not use upland land applications for discharging wastewater from concrete washout areas. • Wheel wash or tire bath wastewater shall not be mixed with wastewater from concrete washout areas. Suggested BMPs: o BMP C151: Concrete Handling o BMP C152: Sawcutting and Surfacing Pollution Prevention o BMP C153: Material Delivery, Storage and Containment o BMP C154: Concrete Washout Area o BMP C250: Construction Stormwater Chemical Treatment o BMP C251: Construction Stormwater Filtration o BMP C252: High pH Neutralization Using CO2 Page 10 of 14 o BMP C253: pH Control for High pH Water. o See Volume IV – Source Control BMPs. Element #10: Control De-Watering • Discharge foundation, vault, and trench de-watering water, which have similar characteristics to stormwater runoff at the site, into a controlled conveyance system prior to discharge to a sediment trap or sediment pond. Channels must be stabilized, as specified in Element #8. • Discharge clean, non-turbid de-watering water, such as well-point ground water, to systems tributary to, or directly into surface waters of the State, as specified in Element #8, provided the de-watering flow does not cause erosion or flooding of receiving waters or interfere with operation of the system. Do not route these clean waters through stormwater sediment ponds. Note that “surface waters of the State” may exist on a construction site as well as off site; for example, a creek running through a site. • Handle highly turbid or contaminated dewatering water from construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam, separately from stormwater. • Discharging sediment-laden (muddy) water into waters of the State likely constitutes violation of water quality standards for turbidity. The easiest way to avoid discharging muddy water is through infiltration and preserving vegetation. • Other treatment or disposal options, depending on site constraints, may include: o Infiltration o Transport offsite in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters o Ecology-approved on-site chemical treatment or other suitable treatment technologies o Sanitary sewer discharge with local sewer district approval, if there is no other option o Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. Suggested BMPs: o BMP C203: Water Bars o BMP C236: Vegetative Filtration Element #11: Maintain BMPs • Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to assure continued performance of their intended function. Conduct maintenance and repair in accordance with BMP specifications. • Remove all temporary erosion and sediment control BMPs not designed to remain in place following construction (e.g. compost socks), within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting from removal of BMPs or vegetation. • Protect all BMPs installed for the permanent control of stormwater from sediment and compaction. All BMPs that are to remain in place following completion of construction shall be examined and placed in full operating condition. If sediment enters the BMPs during construction, it shall be removed and the facility shall be returned to the conditions specified in the construction documents. Page 11 of 14 Suggested BMPs o BMP C150: Materials On Hand o BMP C160: Certified Erosion and Sediment Control Lead Element #12: Manage the Project Phasing of Construction: • Phase development projects to the maximum extent practicable and take into account seasonal work limits in order to prevent soil erosion and, to reduce to the maximum extent practicable, the transport of sediment from the site during construction. Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities for any phase. • Clearing and grading activities for developments are permitted only if conducted pursuant to an approved site development plan (e.g., subdivision approval) that establishes permitted areas of clearing, grading, cutting, and filling. When establishing these permitted clearing and grading areas, minimize the removal of existing trees and the disturbance/compaction of native soils except as needed for building purposes. Delineate the permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree retention areas as may be required by the City, on the site plans and the development site. Seasonal Work Limitations: • From October 1 through April 30, clearing, grading, and other soil disturbing activities will not be permitted unless it is shown to the satisfaction of the City that silt-laden runoff will be prevented from leaving the site through a combination of the following: o Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and o Limitations on activities and the extent of disturbed areas; and o Proposed erosion and sediment control measures. • Based on the information provided and/or local weather conditions, the City may expand or restrict the seasonal limitation on site disturbance. The City shall take enforcement action – such as a notice of violation, administrative order, penalty, or stop-work order under the following circumstances: o If, during the course of any construction activity or soil disturbance during the seasonal limitation period, sediment leaves the construction site causing a violation of the surface water quality standard; or o If clearing and grading limits or erosion and sediment control measures shown in the approved plan are not maintained. • The following activities are exempt from the seasonal clearing and grading limitations: o Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and o Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. Page 12 of 14 Coordination with Utilities and Other Contractors: The primary project proponent shall evaluate, with input from utilities and other contractors, the stormwater management requirements for the entire project, including the utilities, when preparing the Construction SWPPP. Inspection and Monitoring: • For construction sites that will disturb 1 acre or more a Certified Erosion and Sediment Control Lead (CESCL) shall be identified in the Construction SWPPP and shall be on-site or on-call at all times. Certification must be obtained through an approved training program that meets the erosion and sediment control training standards established by Ecology. • Project sites less than one acre (not part of a larger common plan of development or sale) may have a person without CESCL certification conduct inspections. The person shall be identified in the Construction SWPPP and shall be on-site or on-call at all times. • All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted at least weekly and immediately following any substantial rainfall event by a person who is knowledgeable in the principles and practices of erosion and sediment control. The CESCL or inspector (project sites less than one acre) must have the skills to: 1) Assess the site conditions and construction activities that could impact the quality of stormwater, and 2) Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. • The CESCL or inspector must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. They must evaluate the effectiveness of BMPs and determine if it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges. • Implement appropriate BMPs or design changes as soon as possible whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant. • Based on the results of the inspection, construction site operators must correct the problems identified by: o Reviewing the SWPPP for compliance with the 13 construction SWPPP elements and making appropriate revisions within 7 days of the inspection. o Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs as soon as possible, addressing the problems no later than within 10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10 days, the construction site operator may request and extension from the City within the initial 10-day response period. o Documenting BMP implementation and maintenance in the site log book (sites larger than 1-acre). o The CESCL or inspector must inspect all areas disturbed by construction activities, all BMPs, and all stormwater discharge points at least once every calendar week and within 24 hours of any discharge from the site. (For purposes of this condition, individual discharge events that last more than one day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, onl y one inspection is required that week). The CESCL or inspector may reduce the Page 13 of 14 inspection frequency for temporarily stabilized, inactive sites to once every calendar month. Maintaining an Updated Construction SWPPP: • The Construction SWPPP shall be retained on-site or within reasonable access to the site. • The SWPPP shall be modified whenever there is a change in the 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 shall be modified if, during inspections or investigations conducted by the owner/operator, City or a state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Suggested BMPs o BMP C150: Materials On Hand o BMP C160: Certified Erosion and Sediment Control Lead o BMP C162: Scheduling Element #13: Protect Low Impact Development BMPs • Protect all Bioretention and Rain Garden BMPs from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the Bioretention and/or Rain Garden BMPs. • Restore Bioretention and Rain Garden BMPs to their fully functioning condition if they accumulate sediment during construction. Restoring the BMP includes removal of sediment and any sediment-laden Bioretention/Rain Garden soils, and replacing the removed soils with soils meeting the design specification. • Prevent compaction of Bioretention, Rain Garden, and other infiltration BMPs by excluding construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. • Protect surrounding land uses from erosion and manage to avoid introducing sediment onto permeable pavements. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment-lade runoff onto permeable pavements. • Clean pavements fouled with sediments or no longer passing an initial infiltration test using procedures acceptable to the City or in accordance with manufacturer’s procedures. • Keep heavy equipment off of existing soils under LID facilities (Bioretention, Rain Gardens, Infiltration Ponds, Permeable Pavements, etc.) that have been excavated to final grade to retain the infiltration rate of the soils. Suggested BMPs o BMP C102: Buffer Zone o BMP C103: High Visibility Fence o BMP C200: Interceptor Dike and Swale o BMP C201: Grass-Lined Channels o BMP C207: Check Dams o BMP C208: Triangular Silt Dike (TSD) (Geotextile-Encased Check Dam). o BMP C231: Brush Barrier Page 14 of 14 o BMP C233: Silt Fence o BMP C234: Vegetated Strip o Additional Guidance: See Chapter 5: Precision Site Preparation and Construction in the LID Technical Guidance Manual for Puget Sound for more detail on protecting LID integrated management practices.