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HomeMy WebLinkAbout03647 - Technical Information Report - Stormwater Pollution Prevention and Spill Plan .,1W lab I■ RHBL TACOMA • SEATTLE Stormwater Pollution Prevention and Spill Plan PREPARED FOR: Renton School District #403 7812 South 124th Street Seattle, WA 98178 PROJECT: Nelsen Middle School Site Improvements Renton, WA 211128.10 PREPARED BY: Michael R. Norton, P.E. Project Engineer REVIEWED BY: Doreen S. Gavin, P.E. Vice President COY OF RENTO RECEIVE° March 2012 MAS 1 5 2U►2 CUSTOM SERVICE Civil Engineers • Structural Engineers • Landscape Architects • Community Planners • Land SurveyorsCNeighbors 34.y7 Storm wa ter Pollution Prevention and Spill Plan PREPARED FOR : Renton School District #403 SAa 7812 South 124th Street S. q Seattle, WA 98178� t.,;;.oof 7 1k r `: j n;. �. PROJECT ti:'. ,� ,p,23467 U •w�, Nelsen Middle School Site A- SISI N� Improvements e -sst C7c' i' oNAL�- Renton, WA �� r .� 211128.10 I hereby state that this Stormwater PREPARED BY. Pollution Prevention and Spill Plan for Nelsen Middle School Site Michael R. Norton, P.E. Improvements has been prepared by Project Engineer me or under my supervision, and meets g the standard of care and expertise that is usual and customary in this community for professional engineers. REVIEWED BY: I understand that the City of Renton does not and will not assume liability Doreen S. Gavin, P.E. for the sufficiency, suitability, or performances of drainage facilities Vice President prepared by me. February, 2012 TABLE OF CONTENTS A. Activity-Specific Information 1 1.0 Storage and Handling of Liquids 1 1.1 Liquids Onsite 1 1,2 Liquid Containers 1 1.3 Secondary Containment Methods 1 2.0 Storage and Stockpiling of Construction Materials and Wastes 1 2.1 Construction Materials and Wastes 1 2.2 Cover Measures 1 2.3 Containers 1 3.0 Fueling 2 3.1 Method of Onsite Fueling 2 3.2 Tanks 2 3.3 Containment Methods for Fuel Spills 2 3.4 Evening Fueling 2 4.0 Maintenance, Repairs, and Storage of Vehicles and Equipment 2 4.1 Maintenance and Repair Areas 2 4.2 Vehicle Fluids 2 4.3 Signage 2 5.0 Concrete Saw Cutting, Slurry, and Washwater Disposal 3 5.1 Truck and Hand Tool Washout Area 3 . 5.2 Sumps 3 5.3 Methods of Collecting, Treating, and Disposal of Wastewater 3 6.0 Handling of pH Elevated Water 3 6.1 Treating and Neutralizing Water 3 6.2 Disposal of Water 3 7.0 Application of Chemicals including Pesticides and Fertilizers 4 7.1 Chemicals 4 7.2 Where and How Chemicals Will Be Applied 4 7.3 Where and How Chemicals Will Be Stored 4 B. Construction Stormwater Pollution Prevention Plan 5 1.0 Introduction 5 2.0 Project Description 6 3.0 Certified Erosion and Sedimentation Control Lead (CESCL) 6 4.0 Existing Site Conditions 7 5.0 Adjacent Areas 7 6.0 Soils 7 7.0 Erosion Problem Areas 8 8.0 Construction Stormwater Pollution Prevention Elements 8 8.1 Mark Clearing Limits 8 8.2 Establish Construction Access 9 8.3 Control Flow Rates 9 8.4 Install Sediment Controls 9 8.4.1 Stabilize Soils 9 8.4.2 Protect Slopes 9 8.4.3 Protect Drain Inlets 9 8.5 Stabilize Channels and Outlets 10 8.6 Control Pollutants 10 8.7 Control Dewatering 11 8.8 Maintain BMPs 11 8.9 Manage the Project 13 9.0 Construction Phasing 13 10.0 Construction Schedule 14 11.0 Financial/Ownership Responsibilities 15 C. Spill Prevention and Cleanup Report 16 1.0 Sources of a Spill 16 2.0 Personnel Responsible for Spill Prevention and Cleanup 16 3.0 Procedures For Monitoring Spill Prevention and Cleanup 16 4.0 Location of Spill Response Materials 16 5.0 Disposal Methods 16 EXHIBITS Exhibit 1 Inspection Logs Exhibit 2 ESC Measures Exhibit 3 SWPPS Site Plan A. ACTIVITY-SPECIFIC INFORMATION 1.0 STORAGE AND HANDLING OF LIQUIDS 1.1 Liquids Onsite Some common liquids to be found on construction sites include, but are not limited to: pesticides, fertilizer, cleaning solvents, glue, adhesives, paints, curing compounds, wastewater from construction equipment washing, wood preservatives, hydraulic oil/fluids, gasoline, diesel fuel, kerosene, and antifreeze/coolant. Descriptions of all of these liquids can be found in Section 8.6 of Part B. 1.2 Liquid Containers Liquids onsite will be stored and handled in a manner that minimizes the chances of a spill. Steel and plastic volumetric capacities of 55 gallons or less are typically used to store liquids. Liquids shall be stored in an impervious containment area under a roof or other appropriate cover. BMPs for Storage of Liquid, Food Waste, or Dangerous Wasted Containers can be found in Exhibit 2. Locations of the containers can be located on the SWPPS Site Plan, Exhibit 3. 1.3 Secondary Containment Methods All liquids on site will be located such that they will be contained in the event of a spill. These containment areas will be sized so that they are large enough to contain a spill. The location of the containment areas can be found on the SWPPS Site Plan, Exhibit 3. 2.0 STORAGE AND STOCKPILING OF CONSTRUCTION MATERIALS AND WASTES 2.1 Construction Materials and Wastes A location will be specified for construction material storage. This area shall be surrounded by a berm to minimize the tracking of materials out of storage areas and to contain sediment within the storage area. All waste material will be collected in a closed metal dumpster. Location of the construction materials and wastes can be found on the SWPPS Site Plan, Exhibit 3. 2.2 Cover Measures Plastic will be used to cover construction materials. Construction waste materials will be collected and stored in a securely closed metal dumpster. This dumpster will be emptied a minimum of once a week and hauled to a local landfill. No construction materials will be buried on site. These covering measures will keep rainwater from contacting construction materials and wastes that can contribute pollution to storm, surface, and ground water. 2.3 Containers Construction waste will be collected in a securely closed metal dumpster so to ensure that rainwater does not get into the container. The location of this dumpster is called out on the SWPPS Site Plan, Exhibit 3. 1 1303013 3.0 FUELING 3.1 Method of Onsite Fueling Equipment onsite will be re-fueled using truck mounted tanks and wet hoses. Proper training of the fueling operator, the use of spill/drip control and reliable fuel transfer equipment with backup shutoff valving are needed to unsure successful onsite fueling with no spills. BMPs for Mobile Fueling of Vehicles and Heavy Equipment can be found in Exhibit 2. 3.2 Tanks One type of fuel tank on site will be tank mounted to trucks which range from anywhere from 50 to 100 gallons of fuel storage. Fuel trucks can also be brought to the site to fuel equipment and vehicles. 3.3 Containment Methods for Fuel Spills Fueling will occur in an area in which a spill is able to be contained. Location of fueling areas can be found on the SWPPS Site Plan, Exhibit 3. 3.4 Evening Fueling Construction activities will occur during the hours of 7:00 AM and 6:00 PM, Monday through Friday as allowed by the City of Renton. Evening fueling is not expected to occur onsite. 4.0 MAINTENANCE, REPAIRS, AND STORAGE OF VEHICLES AND EQUIPMENT 4.1 Maintenance and Repair Areas All areas used for maintenance and repair of vehicles or equipment will use drip pans or plastic beneath the vehicle or equipment. Plastic will also be placed over the vehicle if it is raining. See Exhibit 2 for the BMPs on Maintenance and Repair of Vehicles and Equipment. Areas used for maintenance and repairs can be found on the SWPPS Site Plan, Exhibit 3. 4.2 Vehicle Fluids Some common vehicle fluids include antifreeze, fuel, motor oil and filters, brake fluid, transmission fluid and power steering fluid. These fluids shall be stored in their originally marked containers in an area that is contained, in order to contain spills. Do not mix vehicle fluids. Fluids shall be disposed of at hazardous waste collection sites. 4.3 Signage Signs will be posted for areas designated for vehicle maintenance. The sign will state that no vehicle washing may occur in the area. Locations of the maintenance and repair areas are shown on the SWPPS Site Plan, Exhibit 3. 2 0113013 5.0 CONCRETE SAW CUTTING, SLURRY, AND WASHWATER DISPOSAL 5.1 Truck and Hand Tool Washout Area Truck and hand tool washout area can be found on the SWPPS Site Plan, Exhibit 3. The location of this washout area is not located in a critical aquifer recharge area. The cleaning of hand tools includes, but is not limited to, screeds, shovels, rakes, floats, and trowels. The washout area will be contained to separate the uncontaminated stormwater from the pollutant source. The washout area shall be in an areas awaiting installation of concrete or asphalt. 5.2 Sumps Sumps will be located in cleanout areas to collect washwater. The location of the sump can be found on the SWPPS Site Plan, Exhibit 3. 5.3 Methods of Collecting, Treating, and Disposal of Wastewater Waste water from exposed aggregate processes, concrete grinding and saw cutting, and new concrete washing and curing water will be collected and treated prior to discharge from the site. Wastewater must be conveyed to a sanitary sewer after approval by the local sewer authority, temporarily stored before proper disposal or recycled. There shall be no discharge to the ground, to a storm drain, or to surface water without proper treatment in accordance with Ecology guidance WQ-95-056, "Vehicle and Equipment Washwater Discharges,"June 1995. The BMP for Washing and Steam Cleaning Vehicles/ Equipment/Building Structures in Exhibit 2 explains more on collecting, treating, and disposing of wastewater. 6.0 HANDLING OF PH ELEVATED WATER 6.1 Treating and Neutralizing Water Sampling of water for pH shall be done weekly when significant concrete work or engineered soils. If a reading of 8.5 or more is found in the water, the water shall be diverted away from storm sewer systems and surface water. Adjusting and neutralizing high pH can be done with appropriate treatment BMP such as CO2 sparging or dry ice. Written approval from the Washington State Department of Ecology is required to adjust or neutralize the pH of the water when using other chemical treatments. 6.2 Disposal of Water Once waters are treated with CO2 sparging, dry ice, or other chemical treatment approved by the Washington State Department of Ecology, they can be disposed of the same way they were disposed of before the high pH reading. This could include discharging into the stormwater systems or sanitary sewer system. 3 ©© D O 7.0 APPLICATION OF CHEMICALS INCLUDING PESTICIDES AND FERTILIZERS 7.1 Chemicals An herbicide treatment may be applied on site to prohibit the growth of plant life under impervious surfaces. Application rates will be determined by the manufacturer recommendations of the herbicide treatment being used. 7.2 Where and How Chemicals Will Be Applied The herbicides treatment will be applied using a sprayer. The area under the asphalt track may receive the herbicide treatment to prohibit the grown of plant life. Locations of where chemicals may be applied on site can be found on the SWPPS Site Plan, Exhibit 3. 7.3 Where and How Chemicals Will Be Stored When chemicals are stored on site they shall be properly contained and clearly marked. The Material Safety Data Sheet (MSDS) for each chemical used during construction activities will be kept on site. Chemicals will be stored so that there is a secondary containment option in place in case of a spill. The location of the chemicals to be stored on site can be found on the SWPPS Site Plan, Exhibit 3. 4 B. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN 1.0 INTRODUCTION In 1972, Congress passed the Federal Water Pollution Control Act (FWPCA), also known as the Clean Water Act (CWA), to restore and maintain the quality of the nation's waterways. The ultimate goal was to make sure that rivers and streams were fishable, swimmable and drinkable. In 1987, the Water Quality Act (WQA) added provisions to the CWA that allowed the EPA to govern stormwater discharges from construction sites. In 2005, the EPA published the final notice for General Permits for Stormwater Discharges from Construction Activities Disturbing 1 Acre or Greater. The general permit includes provisions for development of a Construction Stormwater Pollution Prevention Plan (CSWPP) to maximize the potential benefits of pollution prevention, sediment, and erosion control measures at construction sites. The proposed project will disturb more than 1 acre of area and therefore is required to obtain a National Pollutant Discharge Elimination Systems (NPDES) General Permit for Stormwater Associate with Construction Activities. The NPDES permit requires a Construction Stormwater Pollution Prevention Plan (CSWPPP). Development, implementation, and maintenance of the CSWPPP will provide the selected General Contractor with the framework for reducing soil erosion and minimizing pollutants in stormwater during construction of the elementary school. The CSWPPP will: • Define the characteristics of the site and the type of construction that will occur; • Describe the practices that will be implemented to control erosion and the release of pollutants in stormwater; • Create an implementation schedule to ensure that the practices described in this CSWPPP are in fact implemented, and to evaluate the plan's effectiveness in reducing erosion, sediment, and pollutant levels in stormwater discharged from the site; and • Describe the final stabilization/termination design to minimize erosion and prevent stormwater impacts after construction is complete. This CSWPPP includes the following: • Identification of the Certified Erosion and Sedimentation Control Lead with a description of this person's duties; • Identification of the Construction Stormwater Pollution Prevention Team that will assist in implementation of the CSWPPP during construction; • Description of the existing site conditions including existing land use for the site, soil types at the site, as well as the location of surface waters that are located on or next to the site; • Identification of the body or bodies of water that will receive runoff from the construction site, including the ultimate body of water that receives the stormwater; • Identification of drainage areas and potential stormwater contaminants; 5 01110111 • Description of stormwater management controls and various Best Management Practices (BMPs) necessary to reduce erosion, sediment and pollutants in stormwater discharge; • Description of the facility monitoring plan and how controls will be coordinated with construction activities; and • Description of the implementation schedule and provisions for amendment of the plan. 2.0 PROJECT DESCRIPTION This report accompanies the site development and erosion control plans for Nelsen Middle School located at 2403 Jones Avenue South in Renton, WA. Improvements include the construction of a new baseball field; new soccer field with asphalt track; ADA paths from the existing building to the new baseball and soccer fields; landscaping; and stormwater conveyance and flow control facilities. 3.0 CERTIFIED EROSION AND SEDIMENTATION CONTROL LEAD (CESCL) The General Contractor shall designate a Certified Erosion and Sedimentation Control Lead (CESCL) prior to commencing construction. Upon designation, this CSWPPP will be amended with the following information: Name: Company: Address: Office Phone: Mobile Phone: Fax Number: The CESCL is required to meet Washington State Department of Ecology (DOE) certification requirements. Once this individual is identified, the County Inspector will be notified. The duties of the CESCL include: • Implement the CSWPPP/Temporary Erosion and Sediment Control (TESC) plan with the aid of the CSWPPP team; • Oversee maintenance practices identified as BMPs in the CSWPPP; • Conduct or provide for inspection and monitoring activities; • Stormwater shall be sampled using a turbidity meter; • Identify other potential pollutant sources and make sure they are added to the plan; 6 owolI • Identify any deficiencies in the CSWPPP and make sure they are corrected; and • Ensure that any changes in construction plans are addressed in the CSWPPP. To aid in the implementation of the CSWPPP, the members of the CSWPPP team include the following: General Contractor, CESCL, City of Renton Inspector, Renton School District, Bassetti Architects, Associated Earth Sciences, Inc., and AHBL, Inc. The General Contractor will ensure that all housekeeping and monitoring procedures are implemented, while the CESCL Specialist will ensure the integrity of the structural BMPs. The CSWPPP team will observe construction and erosion control practices and recommend revisions or additions to the CSWPPP and drawings. 4.0 EXISTING SITE CONDITIONS The project site is at the existing Nelsen Middle School located at 2403 Jones Avenue South in Renton, WA, King County Parcel No. 2923059061. The project site encompasses 29.54 acres within the Black River Drainage basin as delineated by the King County Water Features Map. There are no wetlands on the project site. The existing school includes a main building on the southeast part of the site, with athletic fields to the north and west, and paved parking areas to the south, northeast and west of the main building. Site topography is relatively flat to gently sloping, with sloped grassy "steps" which lead downward to the north and west to existing sports field areas. The ground surface continues steeply downward from the subject site, approximately 15 to 20 vertical feet to the north and roughly 25 vertical feet to the west, to nearby properties. A wooded stream corridor with areas of ponded water lies to the east. 5.0 ADJACENT AREAS The Nelsen Middle School facility is bound to the north and northwest by multi-family residences off Benson Road South, to the southwest and east by wooded areas, and to the south by Spring Glen Elementary School. In general, runoff from the existing baseball fields and track along the western portion of the site moves as sheet and subsurface flow to the northwest to exit the site. Drainage from the northern field area enters a series of underdrains and is piped via tightline conveyance system to an existing storm drain manhole in the northern portion of the western field areas before exiting the site. 6.0 Sobs The site soils have been classified as Map Unit AgC -- Alderwood gravelly sandy loam, 6 to 15 percent slopes, according to the WA 633 Soil Survey of King County Area, Washington, provided by the Natural Resource Conservation Service. Permeability is moderately rapid in the surface layer and very slow in the substratum. Roots penetrate easily to the consolidated substratum where they tend to mat on the surface. Some roots enter the substratum through cracks. Water moves on top of the substratum in winter. Available water capacity is low. Runoff is slow to medium, and the hazard of erosion is moderate. The City of Renton Soil Survey Map also classifies on-site soils as AgC — Alderwood gravelly sandy loam, 6 to 15 percent slopes. Dm00 •moip A Geotechnical Engineering Report was created in May, 2011 by Associated Earth Sciences, Inc. Subsurface conditions were explored by advancing 13 exploration borings (EB-1 through EB-13) to gain subsurface information about the site. Representative samples of subsurface soils were obtained from each boring at approximately 2.5- 5-foot depth intervals. Fill Existing fill was encountered in all exploration borings except for EB-1, EB-2 and EB-5. The fill ranged in thickness from 4 to 31 feet within the explorations and consisted of loose to medium dense silty sand and gravel with scattered organics. Stratified Drift Sediments (Undifferentiated) All of the exploration encountered medium dense to very dense brownish gray silty sand with gravel and sand lenses and beds, with thick sand beds encountered in exploration borings EB-5 and EB-9. Weathered Tertiary Bedrock At the location of exploration boring EB-3, the stratified drift was underlain by highly fractured silty sand with gravel, which appeared as "chips" in the bedrock. Where encountered, the weathered bedrock extended beyond the depth explored. Groundwater Groundwater seepage was encountered in a thick sand bed in exploration boring EB-9 at the time of drilling. An observation well was placed in exploration boring EB-9 at the time of drilling to determine if a static groundwater level was present and to measure its depth. On April 11, 2011, a static water level was measured at a depth of 33.81 feet. Moist to wet soil was encountered at various depths within the existing fill, suggesting that perched water should be expected throughout the site. 7.0 EROSION PROBLEM AREAS The proposed improvements will create slopes of 3H:1V along the central "stepped" portion of the site. These slopes are considered a potential erosion problem, particularly during the wet season. Cover measures must be in-place to ensure protection of the slopes if construction activities occur during the wet season. 8.0 CONSTRUCTION STORMWATER POLLUTION PREVENTION ELEMENTS The purpose of this section is to describe how each of the twelve CSWPPP elements has been addressed and to identify the type and location of Best Management Practices (BMPs) used to satisfy the required element. If a CSWPPP element is not applicable to the project, a reason is provided. 8.1 Mark Clearing Limits Prior to beginning land disturbing activities, clearing limits will be marked with high visibility plastic or metal fence. Significant vegetation to remain will be marked and protected by fencing. 8 DWDØ 8.2 Establish Construction Access Existing site driveways will be used as construction entrance(s) to the project site. If sediment tracking should occur, the Contractor will be required to sweep the impacted roadways. Dump trucks hauling material to and from the site will be covered by a tarp. If necessary, a wheel wash will also be in place to keep sediment from tracking onto South 27th Street, 8.3 Control Flow Rates Flow rates will be controlled through the use of Temporary Interceptor Swales, Gravel Check Dams, and a Temporary Sediment Pond. 8.4 Install Sediment Controls As part of initial construction activities, BMPs will be installed to trap sediment on-site. The identified BMPs include Silt Fencing, Storm Drain Inlet Protection for new and existing downstream drainage collecting structures, and Temporary Sediment Pond. 8.4.1 Stabilize Soils To prevent soil from the erosive forces of raindrops, flowing water, and wind, the following BMPs will be implemented: • All disturbed areas that will remain unworked will be stabilized with mulch or temporary hydroseed within 2 days (October 1 - March 31) or 7 days (April 1 - September 30). • After fertilizing, all areas that will not be impacted by construction will be seeded. • Steep slopes shall be covered with netting and blankets. • Dust control will be provided by sprinkling the site with water. • Permanent erosion control measures will include site paving and seeding of exposed soils. 8.4.2 Protect Slopes Slopes on the site will be protected to minimize erosion. Nets and Blankets, Mulching, and Temporary and Permanent Seeding will be used to reduce erosion of exposed soils on slopes. 8.4.3 Protect Drain Inlets Storm drain inlets shall be protected so surface water runoff does not enter the conveyance system without first being filtered. Inlets shall be inspected weekly, at a minimum, and daily during storm events. Storm Drain Inlet Protection will be provided. 9 oWDI! 8.5 Stabilize Channels and Outlets Channels and outlets will be stabilized for the project. Temporary Interceptor Swales will be stabilized with Gravel Check Dams. Outlets of interceptor swales will be stabilized with riprap pads where they enter the Temporary Sediment Pond. 8.6 Control Pollutants All waste materials will be collected and stored in a securely closed metal dumpster. All trash and construction debris from the site will be deposited in the dumpster. The dumpster will be emptied a minimum of once per week, and the trash will be hauled to the local landfill. No construction materials will be buried on-site. All personnel will be instructed regarding the correct procedure for waste disposal. Good housekeeping and spill control practices will be followed during construction to minimize stormwater contamination from petroleum.products, fertilizers, and concrete. Table #1 below lists several pollutants that are commonly found on construction sites that have the potential to contaminate storm runoff. These pollutants will be present, mainly in areas of building and pavement construction. The Contractor and CESCL coordinator will be responsible for identifying areas where these pollutants are being used and monitorrunoff coming from these areas. Pollutant sources will be covered with plastic if contaminated runoff is observed from these areas. If contaminated runoff is found in the sediment trap or soils, the CESCL will direct the Contractor to remove the polluted water/soil and dispose of it in an approved area off-site. Table #1 — Potential Construction Site Stormwater Pollutants Trade Name Material Chemical/Physical Description"} Stormwater Pollutants") Pesticides (insecticides, Various colored to colorless liquid, Chlorinated hydrocarbons, fungicides, herbicide, powder, pellets, or grains organophosphates, rodenticides) carbamates, arsenic Fertilizer Liquid or solid grains Nitrogen, phosphorous Plaster White granules or powder Calcium sulphate, calcium carbonate, sulfuric acid Cleaning solvents Colorless, blue, or yellow-green Perchloroethylene, liquid methylene chloride, trichloroethylene, petroleum distillates Asphalt Black solid Oil, petroleum distillates Concrete White solid Limestone, sand Glue, adhesives White or yellow liquid Polymers, epoxies Paints Various colored liquid Metal oxides, stoddard solvent, talc, calcium carbonate, arsenic Curing compounds Creamy white liquid Naphtha Wastewater from Water Soil, oil &grease, solids construction equipment washing Wood preservatives Clear amber or dark brown liquid Stoddard solvent, petroleum distillates, arsenic, copper, chromium 10 01000 Trade Name Material Chemical/Physical Description") Stormwater Pollutants" Hydraulic oil/fluids Brown oily petroleum hydrocarbon Mineral oil Gasoline Colorless, pale brown or pink Benzene, ethyl benzene, petroleum hydrocarbon toluene, xylene, MTBE Diesel fuel Clear, blue-green to yellow liquid Petroleum distillate, oil & grease, naphthalene, xylenes Kerosene Pale yellow liquid petroleum Coal oil, petroleum distillates hydrocarbon Antifreeze/coolant Clear green/yellow liquid Ethylene glycol, propylene glycol, heavy metals (copper, lead, zinc) Erosion Solid Particles Soil, Sediment (1) Data obtained from MSDS when available 8.7 Control Dewatering Large volumes of dewatering of construction areas or utilities are not anticipated because groundwater is not likely to be encountered at elevations of the proposed utility or pond construction. 8.8 Maintain ESC Measures Temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure performance of their intended function. Sediment control BMPs such as silt fence, slope blanket and drain inlet protection shall be inspected weekly or after a runoff-producing event. Temporary erosion and sediment control measures will be removed within 30 days after final site stabilization is achieved. The following inspection and maintenance practices will be used to maintain erosion and sediment controls: High Visibility Plastic or Metal Fence • If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. Temporary and Permanent Seeding • Any seeded areas that fail to establish at least 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows) shell be reseeded. If reseeding is ineffective, an alternate method, such as sodding, or nets/blankets, shall be used. If winter weather prevents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected. • After adequate cover is achieved, any areas that experience erosion shall be reseeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area reseeded and protected by mulch. • Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. 11 Dm00 Mulching • The thickness of the cover must be maintained. • Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. Nets and Blankets • Good contact with the ground must be maintained, and erosion must not occur beneath the net or blanket. • Any areas of the net or blanket that is damaged or not in close contact with the ground shall be repaired or stapled. • If erosion occurs due to poorly controlled drainage, the problem shall be fixed and the eroded area protected. . Dust Control • Respray as necessary to keep dust to a minimum. Interceptor Dike and Swale • Inspect diversion dikes and interceptor swales once a week and after every rainfall. Immediately remove sediment from the flow area. • Damage caused by construction traffic or other activity must be repaired before the end of each working day. • Check outlets and make timely repairs as needed to avoid gulley formation. Check Dams • Check dams shall be monitored for performance and sediment during and after each runoff producing rainfall. Sediment shall be removed when it reaches one half of the sump depth. • Anticipate submergence and deposition above the check dam and erosion from high flows around the edges of the dam. • If significant erosion occurs between dams, install a protective riprap liner in that portion of the channel. Silt Fence • Any damage shall be repaired immediately. • If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a sediment pond. • It is important to check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the sediment. 12 DeHJø • Sediment deposits shall either be removed when the deposit reaches approximately one-third the height of the silt fence, or a second silt fence shall be installed. • If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced. Temporary Sediment Pond • Sediment shall be removed from the pond when it reaches 1-foot in depth. • Any damage to the pond embankments or slopes shall be repaired. The City of Renton Inspector will be notified of daily construction activities and scheduled meetings between the Erosion Control Inspector and the Contractor. The Maintenance Inspection report will be made after each inspection. Examples of the report forms to be completed by the CESCL are attached as Exhibit 1 of this CSWPPP. Completed forms will be provided to the County Inspector and will also be maintained on- site during the entire construction project. If construction activities or design modifications are made to the site plan that could impact stormwater, or if the Inspector, CESCL, or AHBL determines that the measures are not adequate to prevent erosion and the discharge of sediment from the site (based on turbidity measurements), this CSWPPP will be amended appropriately. The amended CSWPPP will have a description of the new activities that contribute to the increased pollutant loading and the planned source control activities. 8.9 Manage the Project The following practices will be required during construction to properly manage activities: • Comply with seasonal work limitations. • Inspect, maintain and repair ESC measures. • Maintain the CSWPPP including narrative and plans on-site at all times. 9.0 CONSTRUCTION PHASING Phased construction is not anticipated for this project. The construction sequence is described below: 1. Arrange and attend pre-construction meeting with the City of Renton, Engineer, Contractor, CESCL and Owner. 2. Stake/flag clearing and construction limits. 3. Construct all temporary erosion control measures according to the plan. 4. Demolish existing site features indicated for removal. 5. Maintain erosion control measures in accordance with King County and City of Renton standards and manufacturer's recommendations. 13 OCIDIN 6. Rough grade site. All grading shall be done in conformance with the plan and the Geotechnical Engineer's recommendations. 7. Adjust temporary erosion control measures as necessary to match site conditions as construction progresses. 8. Apply erosion control mulch and seeding, straw mulch or equal, to areas that will not be brought to final grade or permanently vegetated within 2 days of exposure during the dry season and 7 days of exposure during the wet season. 9. Apply slope blankets to all slopes greater than 4 feet in height and have reached final grading. 10. Construct storm drainage features. Construct storm drain inlet protection for all catch basins subject to on-site runoff. 11. Relocate erosion control measures or install new measures so that, as site conditions change, the erosion and sediment control is always in accordance with the City of Renton CSWPPP minimum requirements. 12. Final grade site and construct final surfacing treatments. Ensure that surface water is positively directed towards proposed stormwater control facilities. 13. Remove the remaining temporary erosion control items once site has been stabilized and upon approval. 14. Complete final hydroseeding. 10.0 CONSTRUCTION SCHEDULE Construction is scheduled to begin and end in summer of 2012. Based on the construction schedule, construction will be ongoing during the dry season of 2012. During construction, measures will be taken to prevent the transportation of sediment from the site to receiving water. These measures include the use of: • Construction Entrance • Sediment Pond • Construction Road/Parking Area Stabilization • Storm Drain Inlet Protection • Temporary and Permanent Seeding • Silt Fence • Check Dams • Mulching • Nets and Blankets 14 • Interceptor Dike and Swale 11.0 FINANCIAL/OWNERSHIP RESPONSIBILITIES Renton School District is the party responsible for initiation of bonds and other financial securities. 15 DWIJØ C. SPILL PREVENTION AND CLEANUP REPORT 1.0 SOURCES OF A SPILL Spills can happen at many locations on the site. One source of a spill is when liquid or solid materials are being unloaded and loaded. Spills can also occur during the maintenance and repair of vehicles and equipment, when mobile fueling of vehicle and heavy equipment takes place, where vehicles and equipment are parked and stored, at the location where liquid, food waste, or dangerous waste containers are stored and during the washing and steam cleaning of vehicles, equipment, and building structures. BMPs for all of these instances can be found in Exhibit 2. 2.0 PERSONNEL RESPONSIBLE FOR SPILL PREVENTION AND CLEANUP The person responsible for spill prevention and cleanup shall be a person that is available onsite. This person will be named by the general contractor, their contact information will be provided, and this report will be amended to provide the information below. This information can also be found on the SWPPS Site Plan, Exhibit 3. Name: Name: Address: Office Phone: Cell Phone: Fax Number: 3.0 PROCEDURES FOR MONITORING SPILL PREVENTION AND CLEANUP Vehicles, heavy equipment and storage areas will be inspected on a regular basis to assure that there are no spills. In the case of a spill the area shall be cleaned immediately and the contaminated water and soils disposed of according to Section 5.0 of Part C. BMPs for Spills of Oil and Hazardous Substances can be found in Exhibit 2. 4.0 LOCATION OF SPILL RESPONSE MATERIALS Spill response materials will be stored on site. The location of these materials will be determined at a later date by the contractor. 5.0 DISPOSAL METHODS Contaminated water shall be disposed of according to the Environmental Protection Agency's policies. Contaminated soil shall be disposed of properly in accordance with all applicable regulations. Work with Local and State regulatory agencies to develop options for treatment or disposal of contaminated soils. 16 owo• This analysis is based on data and records either supplied to or obtained by AHBL, Inc. These documents are referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. We conclude that this project, as proposed, will not create any new problems within the existing downstream drainage system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. e1 i 'YI,to,ti, Michael R. Norton, P.E. • Project Engineer MRN/Isk March, 2012 Q:\2011\211128\10_CIV\NON_CAD\REPORTS\CSWPP\211128-SWPPS(Draft).doc 17 Dm00 EXHIBITS Exhibit 1 Inspection Logs Nelsen Middle School Site Improvements Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form To be completed every 7 days and within 24 hours of a rainfall event of 0,5 inch or more. Inspector: Date: Inspector's Qualifications: Days since last rainfall: Amount of last rainfall: inches Stabilization Measures Drainage Area Date Since Date of Next Stabilized Stabilized Condition Last Disturbance (yes/No) With Disturbance Stabilization required: To be performed by: On or before: • Nelsen Middle School Site Improvements Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form Perimeter Structural Controls: Date: Silt Fence Drainage Area Has Silt Reached 1/3 Is Fence Properly Is There Evidence of Perimeter of Fence Height? Secured? Washout or Overtopping? Maintenance required for silt fence and straw bales: To be performed by: On or before: Nelsen Middle School Site Improvements Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form Changes required to the pollution prevention plan: Reasons for changes: I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are signification penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. Signature: Date: Exhibit 2 ESC Measures SECTION D.3 ESC MEASURES conveyed to a stabilized discharge point downstream of the disturbed areas. Surface water collection measures shall be installed concurrently with or immediately following rough grading and shall be designed,constructed,and stabilized as needed to minimize erosion. 7. Dewatering Control:The water resulting from construction site de-watering activities must be treated prior to discharge or disposed of as specified. 8. Dust Control:Preventative measures to minimize wind transport of soil shall be implemented when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources. 9. Flow Control: Surface water from disturbed areas must be routed through the project's onsite flow control facility or other provisions must made to prevent increases in the existing site conditions 2- year and 10-year runoff peaks discharging from the project site during construction. D.3.1 CLEARING LIMITS Prior to any site clearing or grading,those areas that are to remain undisturbed during project construction shall be delineated. At a minimum,clearing limits shall be installed at the edges of all critical area buffers and any other areas required to be left uncleared such as portions of the site subject to clearing limits under KCC 16.82.150,areas around significant trees identified to be retained,and other areas identified to be left undisturbed to protect sensitive features. Purpose: The purpose of clearing limits is to prevent disturbance of those areas of the project site that are not designated for clearing or grading. This is important because limiting site disturbance is the single most effective method for reducing erosion. Clearing limits may also be used to control construction traffic,thus reducing the disturbance of soil and limiting the amount of sediment tracked off site. When to Install: Clearing limits shall be installed prior to the clearing and/or grading of the site. Measures to Use: Marking clearing limits by delineating the site with a continuous length of brightly colored survey tape is sometimes sufficient. The tape may be supported by vegetation or stakes,and it shall be 3 to 6 feet high and highly visible. Critical areas and their buffers require more substantial protection and shall be delineated with plastic or metal safety fences or stake and wire fences. Fencing may be required at the County's discretion to control construction traffic or at any location where greater protection is warranted. Permanent fencing may also be used if desired by the applicant. Silt fence, in combination with survey flagging, is also an acceptable method of marking critical areas and their buffers. D.3.1.1 PLASTIC OR METAL FENCE ►oo:..•o.❖r�0000•�woe oo•:�.•oo.•. o.•000.•a.❖ Code: FE Symbol: 4'W4!.!.!.!.!.:, .!.11AN i!.+ Purpose Fencing is intended to(1)restrict clearing to approved limits;(2)prevent disturbance of critical areas, their buffers,and other areas required to be left undisturbed;(3)limit construction traffic to designated construction entrances or roads; and(4)protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits,plastic or metal fence may be used: 1. At the boundary of critical areas,their buffers,and other areas required to be left uncleared. 2. As necessary to control vehicle access to and on the site(see Sections D.3.4.1 and D.3.4.2). 1/9/2009 2009 Surface Water Design Manual—Appendix D D-8 D.3.1 CLEARING LIMITS Design and Installation Specifications 1. The fence shall be designed and installed according to the manufacturer's specifications. 2. The fence shall be at least 3 feet high and must be highly visible. 3. The fence shall not be wired or stapled to trees. Maintenance Requirements 1. If the fence has been damaged or visibility reduced,it shall be repaired or replaced immediately and visibility restored. 2. Disturbance of a critical area,critical area buffer,native growth retention area,or any other area required to be left undisturbed shall be reported to the County for resolution. D.3.1.2 STAKE AND WIRE FENCE Code: SWF Symbol: SWF Purpose Fencing is intended to(1)restrict clearing to approved limits;(2)prevent disturbance of critical areas, their buffers,and other areas required to be left undisturbed;(3) limit construction traffic to designated construction entrances or roads;and(4)protect any areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits,stake or wire fence may be used: 1. At the boundary of critical areas,their buffers,and other areas required to be left uncleared. 2. As necessary,to control vehicle access to and on the site(see Sections D.3.4.1 and D.3.4.2). Design and Installation Specifications See Figure D.3.1.A for details. Maintenance Requirements 1. If the fence has been damaged or visibility reduced,it shall be repaired or replaced immediately and visibility restored. 2. Disturbance of a critical area, critical area buffer,native growth retention area,or other area required to be left undisturbed shall be reported to the County for resolution. 3. The County may require more substantial fencing if the fence does not prevent encroachment into those areas that are not to be disturbed. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-9 D.3.2 COVER MEASURES D.3.2.2 MULCHING • Code: MU Symbol: Purpose The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture,holding fertilizer,seed,and topsoil in place,and moderating soil temperatures. There is an enormous variety of mulches that may be used. Only the most common types are discussed in this section. Conditions of Use As a temporary cover measure,mulch should be used: 1. On disturbed areas that require cover measures for less than 30 days 2. As a cover for seed during the wet season and during the hot summer months 3. During the wet season on slopes steeper than 3H:1 V with more than 10 feet of vertical relief. Design and Installation Specifications For mulch materials,application rates,and specifications,see Table D.3.2.A. Note. Thicknesses may be increased for disturbed areas in or near critical areas or other areas highly susceptible to erosion. Maintenance Standards 1. The thickness of the cover must be maintained. 2. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related,then the drainage problem shall be assessed and alternate drainage such as interceptor swales may be needed to fix the problem and the eroded area remulched. 2009 Surface Water Design Manual-Appendix D 1/9/2009 D-13 SECTION D.3 ESC MEASURES r E ., t-`, 6 i iJ. ..... 1101 tu A ._ . .. .._. • f 4j.� t ix4-L�ftr t x;^ ouf,; sYF rt it •; - ?.• •� .1 r 0 • • Mulch Quality Standards Application Rates Remarks Material Straw Air-dried;free from 2"-3"thick;2-3 Cost-effective protection when applied with adequate undesirable seed and bales per 1000 sf thickness, Hand-application generally requires coarse material or 2-3 tons per acre greater thickness than blown straw. Straw should be crimped to avoid wind blow. The thickness of straw may be reduced by half when used in conjunction with seeding. Wood Fiber No growth inhibiting Approx. 25-30 lbs Shall be applied with hydromulcher. Shall not be Cellulose factors per 1000 sf or used without seed and tackifier unless the application 1000-1500 lbs per rate is at least doubled. Some wood fiber with very acre long fibers can be effective at lower application rates and without seed or tackifier. Compost No visible water or 2"thick min.; More effective control can be obtained by increasing dust during handling. approx. 100 tons thickness to 3". Excellent mulch for protecting final Must be purchased per acre(approx. grades until landscaping because it can be directly from supplier with 800 lbs per cubic seeded or tilled into soil as an amendment. Sources Solid Waste Handling yard) for compost are available from the King County Permit. Commission for Marketing Recyclable Materials at (206)296-4439. Compost may not be used in Sensitive Lake'basins unless analysis of the compost shows no phosphorous release. Hydraulic This mulch category Apply at rates from The BFM shall not be applied immediately before, Matrices includes hydraulic 3,000 lbs per acre during or immediately after rainfall so that the matrix (Bonded slurries composed of to 4,000 lbs per will have an opportunity to dry for 24 hours after Fiber Matrix) wood fiber, paper fiber acre and based on installation.Application rates beyond 2,500 pounds or a combination of manufacturers may interfere with germination and are not usually the two held together recommendations recommended for turf establishment. BFM is by a binding system. generally a matrix where all fiber and binders are in The BFM shall be a one bag, rather than having to mix components from mixture of long wood various manufacturers to create a matrix. BFMs can fibers and various be installed via helicopter in remote areas. They are bonding agents. approximately$1,000 per acre cheaper to install. Chipped Site Average size shall be 2"minimum This is a cost-effective way to dispose of debris from Vegetation several inches. thickness clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of surface waters. If seeding is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment. ' Sensitive lake means a lake that has proved to be particularly prone to eutrophication;the County gives this designation when an active input plan has been adopted to limit the amount of phosphorous entering the lake. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-14 • D.3.2 COVER MEASURES D.3.2.3 NETS AND BLANKETS Code: NE Symbol: Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition,some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets are strands of material woven into an open,but high-tensile strength net(for example,jute matting). Blankets are strands of material that are not tightly woven,but instead form a layer of interlocking fibers,typically held together by a biodegradable or photodegradable netting(for example,excelsior or straw blankets). They generally have lower tensile strength than nets,but cover the ground more completely. Coir (coconut fiber)fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: 1. For permanent stabilization of slopes 2H:I V or greater and with more than 10 feet of vertical relief. 2. In conjunction with seed for final stabilization of a slope,not for temporary cover. However,they may be used for temporary applications as long as the product is not damaged by repeated handling. In fact,this method of slope protection is superior to plastic sheeting,which generates high-velocity runoff(see Section D.3.2.4). 3. For drainage ditches and swales(highly recommended). The application of appropriate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open,porous structure. Synthetic nets and blankets may be used to permanently stabilize channels and may provide a cost-effective,environmentally preferable alternative to riprap. Design and Installation Specifications 1. See Figure D.3.2.B and Figure D.3.2.0 for typical orientation and installation of nettings and blankets. Note:Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. 2. With the variety of products available,it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer thoroughly consults the manufacturer's information and that a site visit takes place in order to insure that the product specified is appropriate. 3. Jute matting must be used in conjunction with mulch(Section D.3.2.2). Excelsior,woven straw blankets,and coir(coconut fiber)blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. Other types of products will have to be evaluated individually. In general,most nets (e.g.,jute matting)require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. 4. Purely synthetic blankets are allowed but shall only be used for long-term stabilization of waterways. The organic blankets authorized above are better for slope protection and short-term waterway protection because they retain moisture and provide organic matter to the soil,substantially improving the speed and success of re-vegetation. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-15 SECTION D.3 ESC MEASURES Maintenance Standards 1. Good contact with the ground must be maintained,and there must not be erosion beneath the net or blanket. 2. Any areas of the net or blanket that are damaged or not in close contact with the ground shall be repaired and stapled. 3. If erosion occurs due to poorly controlled drainage,the problem shall be fixed and the eroded area protected. FT . ______ _ FIGURE D.3.2.B WATERWAY INSTALLATION DO NOT STRETCH BLANKETS/MATTINGS TIGHT - ALLOW THE ROLLS TO MOLD TO ANY IRREGULARITIES SLOPE SURFACE SHALL BE SMOOTH BEFORE PLACEMENT FOR PROPER SOIL CONTACT ANCHOR, STAPLE, AND INSTALL CHECK SLOTS AS PER MANUFACTURER'S RECOMMENDATIONS AVOID JOINING MATERIAL IN THE CENTER OF THE DITCH LIME, FERTILIZE AND SEED BEFORE INSTALLATION t MIN. 4" OVERLAP : . •'' •:.:,Vtj....'..:.•.:74i.: WI J. .,1:. et.illi d.' L ...1t1,, 11=1 I ',.S: A.; .Q'.,. +i A.01MIN. 6" OVERLAP 1-1 1 5,.,` F!fi r,{• 6' -MEI I 1,1�II-v , ., N:•.:•r; '�-`=1 I EI II= i—ii= -IIImo- - -11k 'I I-i I I-III-I 11=' . iFIGURE D.3.2.0 SLOPE INSTALLATION SLOPE SURFACE SHALL BE SMOOTH BEFORE IF THERE IS A BERM AT THE PLACEMENT FOR PROPER SOIL CONTACT TOP OF SLOPE, ANCHOR STAPLING PATTERN AS PER ...ee.:.;.s,• UPSLOPE OF THE BERM • MANUFACTURER'S RECOMMENDATIONS ----7".- MIN. ---7,MIN. 2" / -. F.._I 1 OVERLAP // -1�I_. I 1 ANCHOR IN 6"x6" WIN. TRENCH �+ / I ,, AND STAPLE AT 12. INTERVALS �;•: / / V I1E1' I MIN. 6" OVERLAP Allalpip. � ��=1_ 1 I - • : ••. . I'I ••.„. STAPLE OVERLAPS '� I1 i�I 1111 1 T...� FI i - MAX. 5' SPACING BRING MATERIAL DOWN TO A LEVEL AREA, TURN DO NOT STRETCH BLANKETS/MATTINGS TIGHT - THE END UNDER 4" AND STAPLE AT 12" INTERVALS ALLOW THE ROLLS TO MOLD TO ANY IRREGULARITIES FOR SLOPES LESS THAN 3H:1V, ROLLS LIME, FERTILIZE AND SEED BEFORE INSTALLATION. MAY BE PLACED IN HORIZONTAL STRIPS PLANTING OF SHRUBS, TREES, ETC. SHOULD OCCUR AFTER INSTALLATION. 1/9/2009 2009 Surface Water Design Manual–Appendix D D-16 D.3.2 COVER MEASURES D.3.2.4 PLASTIC COVERING Code: PC Symbol: Purpose Plastic covering provides immediate,short-term erosion protection to slopes and disturbed areas. Conditions of Use 1. Plastic covering may be used on disturbed areas that require cover measures for less than 30 days. 2. Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term applications. 3. Clear plastic sheeting may be used over newly-seeded areas to create a greenhouse effect and encourage grass growth. Clear plastic should not be used for this purpose during the summer months because the resulting high temperatures can kill the grass. 4. Due to rapid runoff caused by plastic sheeting,this method shall not be used upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. Note: There have been many problems with plastic, usually attributable to poor installation and maintenance. However, the material itself can cause problems, even when correctly installed and maintained, because it generates high-velocity runoff and breaks down quickly due to ultraviolet radiation. In addition, if the plastic is not completely removed, it can clog drainage system inlets and outlets. It is highly recommended that alternatives to plastic sheeting be used whenever possible and that its use be limited. Design and Installation Specifications 1. See Figure D.3.2.D for details. 2. Plastic sheeting shall have a minimum thickness of 0.06 millimeters. 3. If erosion at the toe of a slope is likely,a gravel berm,riprap,or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff. .1 FIGURE D.3.2.D PLASTIC COVERING 10' MAX. TIRES, SANDBAGS, OR EQUIVALENT MAY BE USED TO WEIGHT PLASTIC SEAMS BETWEEN SHEETS MUST 41 1 OVERLAP A MINIMUM OF 12" AND III 1=1 1 III-� I-1 I I-I � ��^ BE WEIGHTED OR TAPED III-1il = - IIIIll 111-111_ 1111111111111., E TOE IN SHEETING IN 10' MAX. MINIMUM 4"X4" TRENCH I I-1I1-11 _ ��1 III-111 4, '`• 1 I I-1 1I- IIIIIIIII L111 C� v U PROVIDE ENERGY DISSIPATION 11=1 i I I I v ` ,,, ,• ,. . AT TOE WHEN NEEDED j! _ -Imo,,,.. ... • . . 111- - 1-1 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-17 SECTION D.3 ESC MEASURES Maintenance Standards for Plastic Covering 1. Tom sheets must be replaced and open seams repaired. 2. If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced. 3. When the plastic is no longer needed,it shall be completely removed. D.3.2.5 STRAW WATTLES —so i IP— Code: SW Symbol: Purpose Wattles are erosion and sediment control barriers consisting of straw wrapped in biodegradable tubular plastic or similar encasing material. Wattles may reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sediment. Straw wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. The wattles are placed in shallow trenches and staked along the contour of disturbed or newly constructed slopes. Conditions of Use 1. Install on disturbed areas that require immediate erosion protection. 2. Use on slopes requiring stabilization until permanent vegetation can be established. 3. Can be used along the perimeter of a project,as a check dam in unlined ditches and around temporary stockpiles 4. Wattles can be staked to the ground using willow cuttings for added revegetation. 5. Rilling can occur beneath and between wattles if not properly entrenched,allowing water to pass below and between wattles Design and Installation Specifications 1. It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope contour. 2. Narrow trenches should be dug across the slope,on contour,to a depth of 3 to 5 inches on clay soils and soils with gradual slopes. On loose soils,steep slopes, and during high rainfall events,the trenches should be dug to a depth of 5 to 7 inches,or/2 to 2/3 of the thickness of the wattle. 3. Start construction of trenches and installing wattles from the base of the slope and work uphill. Excavated material should be spread evenly along the uphill slope and compacted using hand tamping or other method. Construct trenches at contour intervals of 3 to 30 feet apart depending on the steepness of the slope,soil type,and rainfall. The steeper the slope the closer together the trenches should be constructed. 4. Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. 5. Install stakes at each end of the wattle,and at 4 foot centers along the entire length of the wattle. 6. If required,install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. 7. At a minimum,wooden stakes should be approximately x' x 24 inches. Willow cuttings or 3/8 inch rebar can also be used for stakes. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-18 D.3.2 COVER MEASURES D.3.2.6 TEMPORARY AND PERMANENT SEEDING Code: SE Symbol: Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use I. 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. 2. Vegetation-lined channels shall be seeded. Channels that will be vegetated should be installed before major earthwork and hydroseeded or covered with a Bonded Fiber Matrix(BFM). 3. Retention/detention ponds shall be seeded as required. 4. At the County's discretion,seeding without mulch during the dry season is allowed even though it will take more than seven days to develop an effective cover. Mulch is,however,recommended at all times because it protects seeds from heat,moisture loss,and transport due to runoff. 5. At the beginning of the wet season,all disturbed areas shall be reviewed to identify which ones can be seeded in preparation for the winter rains(see Section D.5.2). Disturbed areas shall be seeded within one week of the beginning of the wet season. A sketch map of those areas to be seeded and those areas to remain uncovered shall be submitted to the DDES inspector. The DDES inspector may require seeding of additional areas in order to protect surface waters, adjacent properties,or drainage facilities. 6. At final site stabilization,all disturbed areas not otherwise vegetated or stabilized shall be seeded and mulched(see Section D.5.5). Design and Installation Specifications 1. The best time to seed is April 1 through June 30,and September 1 through October 15. Areas may be seeded between July 1 and August 31,but irrigation may be required in order to grow adequate cover. Areas may also be seeded during the winter months,but it may take several months to develop a dense groundcover due to cold temperatures. The application and maintenance of mulch is critical for winter seeding. 2. To prevent seed from being washed away,confirm that all required surface water control measures have been installed. 3. The seedbed should be firm but not compacted because soils that are well compacted will not vegetate as quickly or thoroughly. Slopes steeper than 3H:1V shall be surface roughened. Roughening can be accomplished in a variety of ways,but the typical method is track walking,or driving a crawling tractor up and down the slope,leaving cleat imprints parallel to the slope contours. 4. In general, 10-20-20 N-P-K(nitrogen-phosphorus-potassium)fertilizer may be used at a rate of 90 pounds per acre. Slow-release fertilizers are preferred because they are more efficient and have fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over- application of fertilizer. Disturbed areas within 200 feet of water bodies and wetlands must use slow- release Iow-phosphorus fertilizer(typical proportions 3-1-2 N-P-K). 5. The following requirements apply to mulching: a) Mulch is always required for seeding slopes greater than 3H:1 V(see Section D.4.2.1). 2009 Surface Water Design Manual--Appendix D 1/9/2009 D-21 SECTION D.3 ESC MEASURES b) If seeding during the wet season,mulch is required. c) The use of mulch may be required during the dry season at the County's discretion if grass growth is expected to be slow,the soils are highly erodible due to soil type or gradient,there is a water body close to the disturbed area,or significant precipitation(see Section D.5.2)is anticipated before the grass will provide effective cover. d) Mulch may be applied on top of the seed or simultaneously by hydroseeding. 6. Hydroseeding is allowed as long as tackifier is included. Hydroseeding with wood fiber mulch is adequate during the dry season. During the wet season,the application rate shall be doubled because the mulch and tackifier used in hydroseeding break down fairly rapidly. It may be necessary in some applications to include straw with the wood fiber,but this can be detrimental to germination. 7. Areas to be permanently landscaped shall use soil amendments. Good quality topsoil shall be tilled into the top six inches to reduce the need for fertilizer and improve the overall soil quality. Most native soils will require the addition of four inches of well-rotted compost to be tilled into the soil to provide a good quality topsoil. Compost used should meet Ecology publication 98-38 specifications for Grade A quality compost. 8. The seed mixes Iisted below include recommended mixes for both temporary and permanent seeding. These mixes,with the exception of the wetland mix,shall be applied at a rate of 120 pounds per acre. This rate may be reduced if soil amendments or slow-release fertilizers are used. Local suppliers should be consulted for their recommendations because the appropriate mix depends on a variety of factors,including exposure,soil type,slope, and expected foot traffic. Alternative seed mixes approved by the County may be used. Table D.3.2.B presents the standard mix for those areas where just a temporary vegetative cover is required. 741:4171,3;711::119,7et,. , P.+ ia 'axe}! /� 1 [7.1 sr'•3, T'k. . ^,i�ar i'l tn,j a co-, ,it t t'' 7i`I '1't d 3.rfi, i� 7 -•, - �i. T i Jif: f- T t ( ) tF��f, # 'f.TC Y'e �, i e' i+ 4 j ? v �V , �` to ,4 t,F,rl,k ,,l )0,,)4 ' ltd � a,ly,l',0[i7.,,44 Ia to i,p) fuo it .t0.)c0 !,4gJkt6bx f',-,t rt� , e` . i. .tT2)eaf _.,i,f.. 44,:f'El;,1,i4 1LAA...f E s,,1° 1 j{ 5,f i...).44,e-,,,,. ..i_.4, ),uei e1, _•41.,1,.l i;11`,,;s'`irul;.e 14% : " f r1 b %Weight % Purity %Germination Chewings or red fescue 40 98 90 Festuca rubra var. commutate or Festuca rubra Annual or perennial rye 40 98 90 Lolium multitlorum or Latium perenne Redtop or colonial bentgrass 10 92 85 Agrostis alba or Agrostis tennis White dutch clover 10 98 90 Trifolium repens 1/9/2009 2009 Surface Water Design Manual—Appendix D D-22 • D.3.2 COVER MEASURES Table D.3.2.0 provides just one recommended possibility for Iandscaping seed. `k, • 11 •141 F 1495 t1ia.f 7 t i ` s A. / k{ . l'[ 1 .:l' "V.if � xxtrz . . ast � { �r��� � �"1, .u�al, - y, ( t, �''"R Nx t'�a �� � P. ,*.1};:44. fdk't ti %Weight % Purity % Germination Perennial rye blend 70 98 90 Lolium perenne J Chewings and red fescue blend 30 98 90 Festuca rubra var. commutate or Festuca rubra This turf seed mix in Table D.3.2.D is for dry situations where there is no need for much water. The advantage is that this mix requires very little maintenance. kt r t,� ?$ 4 'r n}w ;t it, rh;.• a{ :?�� �} f aJ '�' Rrt�. ) f5 .. ` r' ,. i., t' j,. L� !1 'J le°J�t \I ( ° 44 6 is ��,',,A,...„0:� t 0,,f a iJ•„�f,,i- } t. ,..S -eta ., •S {?411 ,a'4 » 6 . - , a 7, a 4. M y r`i } b r �� %Weight % Purity %Germination Dwarf tall fescue(several varieties) 45 98 90 Festuca arundinacea var. Dwarf perennial rye(Barclay) 30 98 90 Lolium perenne var. barclay Red fescue 20 98 90 Festuca rubra Colonial bentgrass 5 98 90 Agrostis tenuis Table D.3.2.E presents a mix recommended for bioswales and other intermittently wet areas. Sod shall generally not be used for bioswales because the seed mix is inappropriate for this application. Sod may be used for lining ditches to prevent erosion,but it will provide little water quality benefit during the wet season. i 4 �kr fi r; Lf pr jk .If '� c ,k�s -:-r,,1tt. •yltt l t l 5 ,• a , 1. i'{ 1 1 Y . 5f,{%� 131.1 t 3t ,'t ;� , ,4 a+r '' Jr ,i;. , , . OA rF n ,x Ras t r4� y;\•th N k 'ygr,4,i'A {,'yA q 1^ .1}•. I.r"t, .a : I (Q(y"( 1 �}�t y f i `y ,T s r a t7.a�, "N� z,,, ^f r.,,4{, lQ• •*). ,,z•.c. 1 34,„.,, :�. • ;r :,I. . sk .. a '.`,v � �;J, 1 T `J�1'M 4;,.it i,.hs"'C .- , r 1 a., - I. , a >. ,+1 5 r it 4 ...1 %Weight % Purity % Germination Tall or meadow fescue 75-80 98 90 Festuca arundinacea or Festuca elattar t Seaside/Creeping bentgrass 10-15 92 85 Agrostis palustris Redtop bentgrass 5-10 90 80 Agrostis alba or Agrostis gigantea *Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-23 SECTION D.3 ESC MEASURES The seed mix shown in Table D.3.2.F is a recommended low-growing,relatively non-invasive seed mix appropriate for very wet areas that are not regulated wetlands(if planting in wetland areas,see Section 6.3.1 of the Surface Water Design Manual). Other mixes may be appropriate,depending on the soil type and hydrology of the area. Apply this mixture at a rate of 60 pounds per acre. 7:;f a S :X17 1 SL'k i n>, d 9`. {tic i r.M r:1 V .',v ;rpt .e r�+ 4 t�i� `)h t4 i�,f�t a��t� ).`W.'--.,O,',4.9 Y�; ,�1 t.�'t .�9 �. f ," sf �' � 4 u °j s � f �. h��}� 4.� t-s� �3..4.j °d fi'F Itol N i4.4 9�N}i,e .� �'4 a . 1,19,),?b 4�71,`I rill / '41..•4 ` _0 1 )4,,kill ATL 4�'�,ss��..,,c `��y^��.t0 �4� to,0 tt y-r 4,,t ie,,:w jt' E, ky44 ''101. .,,e •,•‘';1. .. c, .)34* 34, W-.;T''''' V m,.'w1L�rki f,,,,,,r, e.::R �.,: %Weight % Purity %Germination Tall or meadow fescue 60-70 98 90 Festuca arundinacea or Festuca elatior Seaside/Creeping bentgrass 10-15 98 85 Agrostis palustris Meadow foxtail 10-15 90 80 Alepocurus pratensis Alsike clover 1-6 98 90 Tnfolium hybridum Redtop bentgrass 1-6 92 85 Agrostis alba *Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix The meadow seed mix in Table D.3.2.G is recommended for areas that will be maintained infrequently or not at all and where colonization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. The appropriateness of clover in the mix may need to be considered as this can be a fairly invasive species. If the soil is amended,the addition of clover may not be necessary. '!I {.1 y f5rt(t vrJY !H K f��4 4 ° fj, 4 t' 11 itL.' 1,7 4 i414�..,�' fi a;fli 'f�'rt 1' .g3�AW T y., q` kir.-. . {i+ r}4 yY�``4 y 4} tri,3l.Ep tT &Xf lI" 14,000.1fe# *tet,�� iVi �5,;J,�! s' , ti `.i dt:'O tt;0044.n'Vr.l;i.�1 i., 3�1.. 1 itat ::.tNI*ti i stli"ital c.N?1 ' i: !.'ola f't dj k 4: e,t . % Weight % Purity %Germination Redtop or Oregon bentgrass 40 92 85 Agrostis alba or Agrostis oregonensis Red fescue 40 98 90 Festuca rubra White dutch clover 20 98 90 Tnfolium repens Maintenance Standards for Temporary and Permanent Seeding 1. Any seeded areas that fail to establish at least 80 percent cover within one month shall be reseeded. If reseeding is ineffective,an alternate method,such as sodding or nets/blankets,shall be used. If winter weather prevents adequate grass growth,this time limit may be relaxed at the discretion of the County when critical areas would otherwise be protected. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-24 • D.3.2 COVER MEASURES 2. After adequate cover is achieved,any areas that experience erosion shall be re-seeded and protected by mulch. If the erosion problem is drainage related,the problem shall be fixed and the eroded area re-seeded and protected by mulch. 3. Seeded areas shall be supplied with adequate moisture,but not watered to the extent that it causes runoff. D.3.2.7 SODDING Code: SO Symbol: Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: 1. Disturbed areas that require short-term or long-term cover 2. Disturbed areas that require immediate vegetative cover 3. All waterways that require vegetative lining(except biofiltration swales—the seed mix used in most sod is not appropriate for biofiltration swales). Waterways may also be seeded rather than sodded, and protected with a net or blanket(see Section D.3.2.3). Design and Installation Specifications Sod shall be free of weeds, of uniform thickness(approximately 1-inch thick),and shall have a dense root mat for mechanical strength. The following steps are recommended for sod installation: 1. Shape and smooth the surface to final grade in accordance with the approved grading plan. 2. Amend two inches(minimum)of well-rotted compost into the top six inches of the soil if the organic content of the soil is less than ten percent. Compost used should meet Ecology publication 98-38 specifications for Grade A quality compost. 3. Fertilize according to the supplier's recommendations. Disturbed areas within 200 feet of water bodies and wetlands must use non-phosphorus fertilizer. 4. Work lime and fertilizer 1 to 2 inches into the soil,and smooth the surface. 5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close,tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1 V. 6. Roll the sodded area and irrigate. 7. When sodding is carried out in alternating strips or other patterns,seed the areas between the sod immediately after sodding. Maintenance Standards If the grass is unhealthy,the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability,or some other cause,the sod shall be removed,the area seeded with an appropriate mix, and protected with a net or blanket. 2009 Surface Water Design Manual-Appendix D 1/9/2009 D-25 SECTION D.3 ESC MEASURES D.3.3 PERIMETER PROTECTION Perimeter protection to filter sediment from sheetwash shall be located downslope of all disturbed areas and shall be installed prior to upslope grading. Perimeter protection includes the use of vegetated strips as well as,constructed measures,such as silt fences,fiber rolls,sand/gravel barriers,brush or rock filters, triangular silt dikes and other methods. During the wet season,50 linear feet of silt fence(and the necessary stakes)per acre of disturbed area must be stockpiled on site. Purpose:The purpose of perimeter protection is to reduce the amount of sediment transported beyond the disturbed areas of the construction site. Perimeter protection is primarily a backup means of sediment control. Most,if not all,sediment-laden water is to be treated in a sediment trap or pond. The only circumstances in which perimeter control is to be used as a primary means of sediment removal is when the catchment is very small(see below). When to Install: Perimeter protection is to be installed prior to any upslope clearing and grading. Measures to Use:The above measures may be used interchangeably and are not the only perimeter protection measures available. If surface water is collected by an interceptor dike or swale and routed to a sediment pond or trap,there may be no need for the perimeter protection measures specified in this section. Criteria for Use as Primary Treatment:At the boundary of a site,perimeter protection may be used as the sole form of treatment when the flowpath meets the criteria listed below. If these criteria are not met, perimeter protection shall only be used as a backup to a sediment trap or pond. Average Slope Slope Percent Flowpath Length 1.5H:1 V or less 67%or less 100 feet 2H:1V or less 50%or less 115 feet 4H:1 V or less 25%or less 150 feet 6H:1 V or less 16.7%or less 200 feet 10H:1 V or less 10%or less 250 feet D.3.3.1 SILT FENCE Code: SF Symbol: X X X X---X Purpose Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use 1. Silt fence may be used downslope of all disturbed areas. 2. Silt fence is not intended to treat concentrated flows,nor is it intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a silt fence, rather than by a sediment trap or pond,is when the area draining to the fence is small(see"Criteria for Use as Primary Treatment"on page D-30). Design and Installation Specifications 1. See Figure D.3.3.A and Figure D.3.3.B for details. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-30 D.3.3 PERIMETER PROTECTION 2. The geotextile used must meet the standards listed below. A copy of the manufacturer's fabric specifications must be available on site. AOS(ASTM D4751) 30-100 sieve size(0.60-0.15 mm)for slit film 50-100 sieve size(0.30-0.15 mm)for other fabrics Water Permittivity(ASTM D4491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM D4632) 180 lbs. min.for extra strength fabric 100 lbs. min.for standard strength fabric Grab Tensile Elongation(ASTM D4632) 30% max. Ultraviolet Resistance(ASTM D4355) 70% min. 3. Standard strength fabric requires wire backing to increase the strength of the fence. Wire backing or closer post spacing may be required for extra strength fabric if field performance warrants a stronger fence. 4. Where the fence is installed,the slope shall be no steeper than 2H:1 V. 5. If a typical silt fence(per Figure D.3.3.A)is used,the standard 4 x 4 trench may not be reduced as long as the bottom 8 inches of the silt fence is well buried and secured in a trench that stabilizes the fence and does not allow water to bypass or undermine the silt fence. Maintenance Standards 1. Any damage shall be repaired immediately. 2. If concentrated flows are evident uphill of the fence,they must be intercepted and conveyed to a sediment trap or pond. 3. It is important to check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs,replace the fence or remove the trapped sediment, 4. Sediment must be removed when the sediment is 6 inches high. 5. If the filter fabric(geotextile)has deteriorated due to ultraviolet breakdown, it shall be replaced. FIGURE D.3.3.A SILT FENCE JOINTS IN FILTER FABRIC SHALL BE SPLICED AT POSTS. USE STAPLES, WIRE RINGS, OR EQUIVALENT TO ATTACH FABRIC TO POSTS. 2"x2" BY 14 Go. WIRE OR EQUIVALENT, IF STANDARD STRENGTH FABRIC USED �,�..+---. I FILTER FABRIC I I ---: I z II I N I I :Awe, Iil 1o1=1- — _ is „11t' 1„11 11=11=11,,,111111 II°'ll, _ =TT>= -1111 0— z 6' MAX. MINIMUM 4"x4" TRENCHT lJ WI NATIVE BACKFILL SOIL ENCH OR 3/4TH 1.5" .N POST SPACING MAY BE INCREASED WASHED GRAVEL TO 8' IF WIRE BACKING IS USED 2"x4" WOOD POSTS, STEEL FENCE NOTE: FILTER FABRIC FENCES SHALL BE POSTS, REBAR, OR EQUIVALENT INSTALLED ALONG CONTOUR WHENEVER POSSIBLE 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-31 SECTION D,3 ESC MEASURES IFIGURE D.3.3.B SILT FENCE INSTALLATION BY SLICING , . It . .11 . : 'SILT FcNCE , ' .. • .... .•,•,:. lciiii Or tAO: — BELT 1.--. T 1, L.' •' -111' TOF 0" • FLOW ,...,. ; ' 8 - • ••- •—isr....:: • . . 100% :COMPACTION pAcp•NAL.:41-Aq.NEINIT EACH SIDE p.Ovfat_Es 5T4blonf . . ,. - . Nr-- .0.1vr s4;40*. #4t."VN7/4/71 '/: ',...... -Iv liwilliiiiiii aii.%ilfnigli. 5'#:'/ ' ''J§k#4 N.,- '1\*•\ Mit!..ii !:•'•,i: 1 ft OV,2>.'A‘¢ giligNiiiii; ..,, U.!• \ Aeie% !,..-iv,vt,,,,Nitf .N.(W4Q*404,P4e. AttAdimatt DEIAIL ; 4A404 •, ""*PAr: 1.. GATHER FABRIC AT POSTS, IF :NtEDED. a s,.,Av4.‘, -"44:440W). ls,`A0 /*." 4 41444.&-4" 2. UTILIZE THREE TIES PER POST; ALL WITHIN • PA t'o$V,..1"*.",' VW4*,k.* TOP 8" OF FAV.iP , . Watt3. ivsiTioN 04.1, TIE: 0140010Y, ep.610VRING ; . HOLES VekTICALLY **ANNUM OF 1" APART. 1. POST SPACING; 7. MAX. ON OPEN RuNs. 4MAX: ON POOLING AREAS. 4. HANG EACH. TIE, ..(M A P6§T. .NtriIPLt AND TIGHTEN :SECURELY: USE CABLE TIES 2. POST DEPTH: AS: MUCH BELOW (50 143s) PP'W-• WIRE. GROUND:AS FABRIC ABOVE GROUND. I PONDING KtOKT MAX. 44, ATTACH FABRIC TO UPSTREAM -SIM OF P091. 4. DRIVE OVER Mil SIDE or 041. ROLL OF SILT FENCE FENCE 2 TO 4 TIMES WITH utylot EXERTING: 60 P5.I. OR GREATER. 5. NO MORE: Il-IAN 24" OF A W. ARIC IS ALLOWED;ABOVE AROUND: PLOW 6, VIBRATORY PLOW IS NOT ACCEPTABLE BECAUSE OF HORIZONTAL '•GOMPAGTION. •" • -dts--- OPERATION • iiiL at ' : .PABRIC ABOVE -' • ....sli , , • 'GROUND IIIIIIIIIIMIIViii .„., SLICING BLADE 3 1rV Ask ;(gtri10,1 MDI-) ' . • TM .• ,.• : " 'N..' , i••1 ' ''...sr;CP:$•\° 1 HORIZONTAL CHISEL POINT . .. .40 • '/ • / / , virr •. /. • (76„m WIDTH) ‘. <.\<\, ,, 4\ ' . . .f‹10: \4 .„, -,, -.N., go.0-3oomm SILT FENCE INSTALLATION SY SLICING METHOD . . 1/9/2009 2009 Surface Water Design Manual-Appendix D D-32 • D.3.4 TRAFFIC AREA STABILIZATION D.3.4.1 STABILIZED CONSTRUCTION ENTRANCE MEM Code: CE Symbol: Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by motor vehicles or runoff by constructing a stabilized pad of quarry spalls at entrances to construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site.Access and exits shall be limited to one route if possible,or two for linear projects such as roadway where more than one access/exit is necessary for maneuvering large equipment. Design and Installation Specifications 1. See Figure D.3.4.A for details. 2. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM D4751) 200 psi min. Grab Tensile Elongation (ASTM D4632) 30%max. Mullen Burst Strength(ASTM D3786-80a) 400 psi min. AOS (ASTM D4751) 20-45(U.S. standard sieve size) 3. Hog fuel(wood based mulch)may be substituted for or combined with quarry spalls in areas that will not be used for permanent roads. The effectiveness of hog fuel is highly variable,but it has been used successfully on many sites. It generally requires more maintenance than quarry spalls. Hog fuel is not recommended for entrance stabilization in urban areas. The inspector may at any time require the use of quarry spalls if the hog fuel is not preventing sediment from being tracked onto pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent roadbeds because organics in the subgrade soils cause difficulties with compaction. 4. Fencing(see Section D.3.1)shall be installed as necessary to restrict traffic to the construction entrance. 5. Whenever possible,the entrance shall be constructed on a firm,compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. Maintenance Standards 1. Quarry spalls(or hog fuel)shall be added if the pad is no longer in accordance with the specifications. 2. If the entrance is not preventing sediment from being tracked onto pavement,then alternative measures to keep the streets free of sediment shall be used. This may include street sweeping,an increase in the dimensions of the entrance,or the installation of a wheel wash. If washing is used,it shall be done on an area covered with crushed rock, and wash water shall drain to a sediment trap or pond. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-39 SECTION D.3 ESC MEASURES 3. Any sediment that is tracked onto pavement shall be removed immediately by sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street,except when sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets,a small sump must be constructed. The sediment would then be washed into the sump where it can be controlled. Wash water must be pumped back onto the site and can not discharge to systems tributary to surface waters. 4. Any quarry spalls that are loosened from the pad and end up on the roadway shall be removed immediately. 5. If vehicles are entering or exiting the site at points other than the construction entrance(s),fencing (see Section D.3.1)shall be installed to control traffic. FIGURE D.3.4.A STABILIZED CONSTRUCTION ENTRANCE AS PER KING COUNTY ROAD STANDARDS, DRIVEWAYS SHALL BE PAVED TO THE EDGE s op9 OF R-O-W PRIOR TO INSTALLATION OF THE c•Okel- ��°�� CONSTRUCTION ENTRANCE TO AVOID 0 ' / DAMAGING OF THE ROADWAY ,•101 IT IS RECOMMENDED THAT THE R = 25' MIN. wiiif� ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE PAD Wiritteib 4' ti INSTALL DRIVEWAY CULVERT IF THERE V�r4b,4,0t�,� IS A ROADSIDE DITCH PRESENT, AS 4-04A-ore. PER KING COUNTY ROAD STANDARDS \�j��7��I�;��r� `',~,' ` 4. I��� 4"-B" QUARRY SPALLS viA tl‘tioig.�r V GEOTEXTILE 11.044.4141 '' 1") 12" MIN. THICKNESS PROVIDE FULL WIDTH OF INGRESS/EGRESS AREA 1/9/2009 2009 Surface Water Design Manual—Appendix D D-40 D.3.4 TRAFFIC AREA STABILIZATION D.3.4.2 CONSTRUCTION ROAD/PARKING AREA STABILIZATION Code: CRS Symbol: Purpose Stabilizing subdivision roads,parking areas,and other onsite vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or runoff. Conditions of Use 1. Roads or parking areas shall be stabilized wherever they are constructed,whether permanent or temporary,for use by construction traffic. 2. Fencing(see Section D.3.1)shall be installed, if necessary,to limit the access of vehicles to only those roads and parking areas that are stabilized. Design and Installation Specifications 1. A 6-inch depth of 2-to 4-inch crushed rock,gravel base,or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATB)may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If the area will not be used for permanent roads, parking areas,or structures,a 6-inch depth of hog fuel may also be used,but this is likely to require more maintenance. Whenever possible,construction roads and parking areas shall be placed on a firm,compacted subgrade. Note:If the area will be used for permanent road or parking installation later in the project, the subgrade will be subject to inspection. 2. Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain transversely.Drainage ditches shall be provided on each side of the roadway in the case of a crowned section,or on one side in the case of a super-elevated section. Drainage ditches shall be designed in accordance with the standards given in Section D.3.6.3 (p. D-60)and directed to a sediment pond or trap. 3. Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet-flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation,then it is generally preferable to use the vegetation to treat runoff,rather than a sediment pond or trap. The 50 feet shall not include vegetated wetlands. If runoff is allowed to sheet flow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no concentrated runoff is created. 4. In order to control construction traffic,the County may require that signs be erected on site informing construction personnel that vehicles,other than those performing clearing and grading,are restricted to stabilized areas. 5. If construction roads do not adequately reduce trackout to adjacent property or roadways,a wheel wash system will be required. Maintenance Standards Crushed rock,gravel base,hog fuel,etc. shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-41 SECTION D.3 ESC MEASURES D.3.4.3 WHEEL WASH Ow— Code: W W Symbol:' LTD --.1.,_ -�.__.}- Purpose Wheel wash systems reduce the amount of sediment transported onto paved roadways and into surface water systems by construction vehicles. Conditions of Use When a stabilized construction entrance is not preventing sediment from being tracked onto pavement: • Wheel washing is generally an effective erosion and sediment control method and BMP when installed with careful attention to topography. For example,a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck wheels and undercarriage can run unimpeded into the street. • Pressure washing combined with an adequately sized and properly surfaced wash pad with direct drainage discharge to a large 10 foot x 10-foot sump can be very effective. Design and Installation Specifications A suggested detail is shown in Figure D.3.4.B. 1. A minimum of 6inches of asphalt treated base(ATB)over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash area. 2. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. 3. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. 4. Midpoint spray nozzles are only needed in very muddy conditions. 5. Wheel wash systems should be designed with a small grade change,6 to 12 inches for a 10-foot wide pond,to allow sediment to flow to the low side of the pond and to help prevent re-suspension of sediment. 6. A drainpipe with a 2 to 3 foot riser should be installed on the low side of the wheel wash pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. 7. Polyacrylamide(PAM)added to the wheel washwater at a rate of 0.25--0.5 pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or erosion control and is being applied by a water truck,the same truck may be used to change the washwater. Maintenance Standards 1. The wheel wash should start out each day with clean,fresh water. 2. The washwater should be changed a minimum of once per day. On large earthwork jobs where more than 10-20 trucks per hour are expected,the washwater will need to be changed more often. 3. Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system,such as a closed-loop recirculation system or land application, or to the sanitary sewer system with proper local sewer district approval or permits. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-42 D.3.4 TRAFFIC AREA STABILIZATION FIGURE D.3.4.B WHEEL WASH AND PAVED CONSTRUCTION ENTRANCE •=3" TRASH:PUMP WITH FLOATS - 0" SEWER PIPE WITH ON $(./CT1014 HOSE i3uTTRFLY vAINE0 . ... i- .i'', et-ittjULE:40. S.LIMP. WIT4 5. '-1 :SN . --1.1-4/2" 'SCHEDULE 40: • 'NA'.'SPRAYERS 1 MIDPOINT SPRAY NOZZLES, .51 I 1 IF NEEDED SLOPE $05iVw ', SLOPt ..i I .---.11.•- % SLOPE . . ---------- ,---„, 1 ..‘ , , ._____ 1 0 ' • ,,,,,, I, i 'x -6." ATAID .00Nst,46.010,, $,L91,1 .1 . ENTRANCE —15. ATH APRON; TO,i:PPOTEGT -BALL VALAts- .• - • GROUND FROM SPLASHING 'WATER ASPHALT CURE..ON THE 8" pLEEVE I./NDEP ROAD - LOW ROAD SIDE TO DIRECT WATER BACK TO POND .01:41 viEw I -IV 15' 20' lb • 50' _ ---- —--•-- Ak: '''. K4'i7 , v4411,: s: CURB , . 'T•t!."11, ,,, ,-.4..-,\.-,,? <>„,-, ...,,AA 6" SLEEVE I ELEVATION VIEW 1.0..cATE :INVERT OF Top. PIPE 1' ABOVE BOTTOM OF WHEEL WASH 18' se.1 MP r • WATER LEVEL -.2.2, 51 12' as ea I i T . . DRAIN -RIPE 1:1 SLOPE iSaTION A-A I NOTES:, 1. 8uti,t? ,13'iiil:' SUMP TO AGCOMCiDATE CLEANING ,BY TRACKHOE. WHEEL WASH 2009 Surface Water Design Manual-Appendix D 1/9/2009 D-43 • D.3.5 SEDIMENT RETENTION D.3.5.2 SEDIMENT POND Code: SP Symbol: Purpose Sediment ponds remove sediment from runoff originating from disturbed areas of the site. Sediment ponds are typically designed to only remove sediment as small as medium silt(0.02 mm). As a consequence,they usually reduce turbidity only slightly. Conditions of Use A sediment pond shall be used where the contributing drainage area is 3 acres or more. Design and Installation Specifications 1. See Figure D.3.5.B,Figure D.3.5.C, and Figure D.3.5.D for details. 2. If permanent runoff control facilities are part of the project,they should be used for sediment retention (see"Use of Permanent Drainage Facilities"on page D-44). Determining Pond Geometry 1. Obtain the discharge from the hydrologic calculations for the 2-year peak flow using KCRTS with 15- minute time steps(Q2). The 10-year KCRTS 15-minute peak flow shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required,the Rational Method may be used(Section 3.2.1 of the Surface Water Design Manual). 2. Determine the required surface area at the top of the riser pipe with the equation: SA = 2 x Q2/0.00096 or 2080 square feet per cfs of inflow See Section D.3.5.1 (p.D-45)for more information on the derivation of the surface area calculation. 3. The basic geometry of the pond can now be detennined using the following design criteria: • Required surface area SA(from Step 2 above)at top of riser • Minimum 3.5-foot depth from top of riser to bottom of pond • Maximum 3:1 interior side slopes and maximum 2:1 exterior slopes. The interior slopes may be increased to a maximum of 2:1 if fencing is provided at or above the maximum water surface • One foot of freeboard between the top of the riser and the crest of the emergency spillway • Flat bottom • Minimum one foot deep spillway • Length-to-width ratio between 3:1 and 6:1. Sizing of Discharge Mechanisms Principal Spillway:Determine the required diameter for the principal spillway(riser pipe). The diameter shall be the minimum necessary to pass the developed condition 10-year peak flow using KCRTS with 15- minute time steps(Qio). Use Figure 5.3.4.H(SWDM Chapter 5)to determine this diameter(h=one foot). Note:A permanent control structure may be used instead of a temporary riser. 2009 Surface Water Design Manual-Appendix D 1/9/2009 D-47 SECTION D.3 ESC MEASURES Emergency Overflow Spillway:Determine the required size and design of the emergency overflow spillway for the developed condition 100-year KCRTS 15-minute peak flow using the procedure in Section 5.3.1 ("Emergency Overflow Spillway"subsection)of the Surface Water Design Manual. Dewatering Orifice:Determine the size of the dewatering orifice(s)(minimum 1-inch diameter)using a modified version of the discharge equation for a vertical orifice and a basic equation for the area of a circular orifice. 1. Determine the required area of the orifice with the following equation: s( )0.5 G A° = A 2h =4.81(10 )A3a 0.6x3600Tg°5 where Ao = orifice area(square feet) As = pond surface area(square feet) h = head of water above orifice(height of riser in feet) T = dewatering time(24 hours) g = acceleration of gravity(32.2 feet/second2) 2. Convert the required surface area to the required diameter D(inches)of the orifice: D=24x A° =13.54x A° �VYf 7F 3. The vertical,perforated tubing connected to the dewatering orifice must be at least 2 inches larger in diameter than the orifice to improve flow characteristics. The size and number of perforations in the tubing should be large enough so that the tubing does not restrict flow. The flow rate should be controlled by the orifice. Additional Design Specifications • The pond shall be divided into two roughly equal volume cells by a permeable divider that will reduce turbulence while allowing movement of water between cells. The divider shall be at least one- half the height of the riser and a minimum of one foot below the top of the riser. Wire-backed,2-to 3-foot high,extra strength filter fabric(see Section D.3.3.1)supported by treated 4"x4"s may be used as a divider. Alternatively,staked straw bales wrapped with filter fabric(geotextile)may be used. If the pond is more than 6 feet deep,a different mechanism must be proposed. A riprap embankment is one acceptable method of separation for deeper ponds. Other designs that satisfy the intent of this provision are allowed as long as the divider is permeable,structurally sound,and designed to prevent erosion under or around the barrier. • To aid in determining sediment depth,one-foot intervals shall be prominently marked on the riser. • If an embankment of more than 6 feet is proposed,the pond must comply with the criteria under "Embankments"in Section 5.3.1 of the Surface Water Design Manual. Maintenance Standards 1. Sediment shall be removed front the pond when it reaches 1 foot in depth. 2. Any damage to the pond embankments or slopes shall be repaired. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-48 P.3.5 SEDIMENT RETENTION 1. FIGURE D.3.5.B SEDIMENT POND PLAN VIEW KEY Dv1DER INTO SLOPE TO PREVENT FLOW -- AROUND SIDES -411111 THE POND LENGTH SHALL BE 3 TO 8 TIMES THE MAXIMUM POND WIDTH ,� EMERGENCYOVERFLOW 11111i11111Mr"lb410 SPILLWAY q NM 47, .��. rte 1� POND LENGTH r 1...�•. NFLOW '�� ` � M1wlr .� ��� • SIL7 FENCE OR RfSfR PIPE +� EOUNAIENT DMDER ' DISCHARGE TO STABILTZEO CONVEYANCE,OUTLET OR • LEVEL SPREADER r A a F.11 I • NOTE:POND MAY BE FORMED BY BERM OR , OY PARTIAL OR COMPLETE EXCAVATION ---" mir s FIGURE D.3.5.0 SEDIMENT POND CROSS SECTION RISER PIPE CREST OF 5' MIN.WIDTH (PRINCIPAL SPILLWAY) EMERGENCY SPILLWAY OPEN AT TOP WITH '// TRASH RACK I� IM PI— k PER FIG. 5.3.7.0EMBANKMENT COMPACTED 95%. -1I III— \_ 1' MIN. PERVIOUS MATERIALS SUCH AS ■, DEWATERWC DEVICE I _ _____ GRAVEL OR CLEAN SAND SHALL u "S (SEE RISER DETAIL)N I NOT BE USED. bk } S ==_===___=- -_' 1.5' `r -- - - 11 1L-11-11!...31,•—•11-T 011�111ar- 1 I I -11 11 1- -p I—u n -1'_11H111 °AI_II •I:IE1 `T 1,9' II I"II� DISCHARGE TO STABILIZED WIRE-BACKED SILT FENCE, DEWATERING CONCRETE BASE CONVEYANCE, OUTLET OR STAKED HAYBALES WRAPPED ORIFICE (SEC RISER DETAIL) LEVEL SPREADER WITH FILTER FABRIC,OR EOUNALENT DIVIDER 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-49 • SECTION D3 ESC MEASURES FIGURE D.3.5.D SEDIMENT POND RISER DETAIL POLYET NE CAP PROVIDE ADEQUATE STRAPPING INK PERFORATED POLYETHYLENE - METAL DRAINAGE TUBING, DIAMETER - CORRUGATEDAL RATED MIN. 2" LARGER THAN DEWATERING ORIFICE. - TUBING SHALL COMPLY '_ WITH ASTM F667 ANO - 3.5. MIN. AASHTO M294. -- WATERTIGHT EC-WATERING ORIFICE, SCHEDULE COUPLING TACK WELD 40 STEEL STUB MIN. DIAMETER AS PER CALCULATIONS 7+,1 1 1 1 En 6" MIN. r--- J 18" MIN. { ALTERNATIVELY. METAL STAKES AND WIRE MAY 8E USED TO CONCRETE 60.5£ PREVENT FLOTATION �+-2X RISER OW. MLN. • • • • 1/9/2009 2009 Surface Water Design Manual—Appendix D D-50 D.3.5 SEDIMENT RETENTION D.3.5.3 STORM DRAIN INLET PROTECTION • Code: FFP or CBI or CBP Symbol: II I or or orr Purpose Storm drain inlets are protected to prevent coarse sediment from entering storm drainage systems. Temporary devices around storm drains assist in improving the quality of water discharged to inlets or catch basins by pending sediment-laden water. These devices are effective only for relatively small drainage areas. Conditions of Use 1. Protection shall be provided for all storm drain inlets downslope and within 500 feet of a disturbed or construction area,unless the runoff that enters the catch basin will be conveyed to a sediment pond or trap. 2. Inlet protection may be used anywhere at the applicant's discretion to protect the drainage system. This will,however,require more maintenance,and it is highly likely that the drainage system will still require some cleaning. 3. The contributing drainage area must not be larger than one acre. Design and Installation Specifications I. There are many options for protecting storm drain inlets. Two commonly used options are filter fabric protection and catch basin inserts. Filter fabric protection(see Figure D.3.5.E)is filter fabric (geotextile)placed over the grate. This method is generally very ineffective and requires intense maintenance efforts. Catch basin inserts(see Figure D.3.5.F)are manufactured devices that nest inside a catch basin. This method also requires a high frequency of maintenance to be effective. Both options provide adequate protection,but filter fabric is likely to result in ponding of water above the catch basin,while the insert will not. Thus,filter fabric is only allowed where ponding will not be a traffic concern and where slope erosion will not result if the curb is overtopped by ponded water. Trapping sediment in the catch basins is unlikely to improve the water quality of runoff if it is treated in a pond or trap because the coarse particles that are trapped at the catch basin settle out very quickly in the pond or trap. Catch basin protection normally only improves water quality where there is no treatment facility downstream. In these circumstances,catch basin protection is an important last line of defense. It is not,however,a substitute for preventing erosion. The placement of filter fabric under grates is generally prohibited and the use of filter fabric over grates is strictly limited and discouraged. 2. It is sometimes possible to construct a small sump around the catch basin before final surfacing of the road. This is allowed because it can be a very effective method of sediment control. 3. Block and gravel filters,gravel and wire mesh filter barriers,and bag barriers filled with various filtering media placed around catch basins can be effective when the drainage area is 1 acre or less and flows do not exceed 0.5 cfs. It is necessary to allow for overtopping to prevent flooding. Many manufacturers have various inlet protection filters that are very effective in keeping sediment-laden water from entering the storm drainage system. The following are examples of a few common methods. a) Block and gravel filters(Figure D.3.5.G)are a barrier formed around an inlet with standard concrete block and gravel, installed as follows: • Height is 1 to 2 feet above the inlet. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-51 • SECTION D.3 ESC MEASURES • Recess the first row of blocks 2 inches into the ground for stability. • Support subsequent rows by placing a 2x4 through the concrete block opening. • Do not use mortar. • Lay some blocks in the bottom row on their side for dewatering the pooled water. • Place cloth or mesh with 1/2 inch openings over all block openings. • Place gravel below the top of blocks on slopes of 2:1 or flatter. • An alternate design is a gravel donut. b) Gravel and wire mesh filters consist of a gravel barrier placed over the top of an inlet This structure generally does not provide overflow. Install as follows: • Cloth or comparable wire mesh with'/2 inch openings is placed over inlet. • Coarse aggregate covers the cloth or mesh. • Height/depth of gravel should be 1 foot or more, 18 inches wider than inlet on all sides. c) Curb inlet protection with a wooden weir is a barrier formed around an inlet with a wooden frame and gravel,installed as follows: • Construct a frame and attach wire mesh(1/2 inch openings)and filter fabric to the frame. • Pile coarse washed aggregate against the wire/fabric. • Place weight on frame anchors. d) Curb and gutter sediment barriers(Figure D.3.5.H)consist of sandbags or rock berms(riprap and aggregate)3 feet high and 3 feet wide in a horseshoe shape, installed as follows: • Bags of either burlap or woven geotextile fabric,filled with a variety of media such as gravel, wood chips,compost or sand stacked tightly allows water to pond and allows sediment to separate from runoff. • Leave a "one bag gap" in the top row of the barrier to provide a spillway for overflow. • Construct a horseshoe shaped berm,faced with coarse aggregate if using riprap,3 x 3 and at least 2 feet from the inlet. • Construct a horseshoe shaped sedimentation trap on the outside of the berm to sediment trap standards for protecting a culvert inlet. 4. Excavated drop inlet sediment traps are appropriate where relatively heavy flows are expected and overflow capability is needed. If emergency overflow is provided,additional end-of-pipe treatment may be required. Excavated drop inlets consist of an excavated impoundment area around a storm drain. Sediment settles out of the stormwater prior to enter the drain. Install according to the following specifications: a) The impoundment area should have a depth of 1 -2 feet measured from the crest of the inlet structure. b) Side slopes of the excavated area must be no steeper than 2:1. c) Minimum volume of the excavated area should be 35 cubic yards. d) Install provisions for draining the area to prevent standing water problems. e) Keep the area clear of debris. f) Weep holes may be drilled into the side of the inlet. g) Protect weep holes with wire mesh and washed aggregate. 1/9/2009 2009 Surface Water Design Manual—Appendix D D-52 D.3.5 SEDIMENT RETENTION h) Weep holes must be sealed when removing and stabilizing excavated area. i) A temporary dike may be necessary on the downslope side of the structure to prevent bypass flow. Maintenance Standards 1. Any accumulated sediment on or around inlet protection shall be removed immediately. Sediment shall not be removed with water,and all sediment must be disposed of as fill on site or hauled off site. 2. Any sediment in the catch basin insert shall be removed when the sediment has filled one-third of the available storage. The filter media for the insert shall be cleaned or replaced at least monthly. 3. Regular maintenance is critical for all forms of catch basin/inlet protection. Unlike many forms of protection that fail gradually,catch basin protection will fail suddenly and completely if not maintained properly. FIGURE D.3.5.E FILTER FABRIC PROTECTION STANDARD STRENGTH FILTER FABRIC GRATE NOTE: ONLY TO BE USED WHERE I PONDING OF WATER ABOVE THE II I I I II I CATCH BASIN WILL NOT CAUSE TRAFFIC PROBLEMS AND WHERE I1— _ II— EROSION OF WILLVERFLOW NOTRESULT IN -1l 11 CATCH BASIN II FIGURE D.3.5.F CATCH BASIN INSERT CATCH BASIN -GRATE NOTE: THIS DETAIL IS ONLY III'I OVERFLOW IIIA SCHEMATIC. ANY INSERT IS SOLID -I AL.5 OWD. OASRAGEMHNE, MEANS III= TO DEWATER THE STORED FILTER MEDIA —II SEDIMENT, AN OVERFLOW, AND FOR DEWATERING ill 11111 I 1 II CAN BE EASILY MAINTAINED. 77 I POROUS BOTTOM I I I i 1 11 ll1 111E- 11 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-53 • SECTION D.3 ESC MEASURES FIGURE D.3.5.G BLOCK AND GRAVEL CURB INLET PROTECTION A \E!AcK ‘SJPEWALK CATCH BASIN COVER, • 2)(4 WOOD C) CURB INLET IMEMIF M MIME= 4",:fith CURE( FACE );1*,:4 1 IIIii11tL irt ?1.! **NW' • . 41-1‘..; l4**14r:: rttA *.;• b°•'0,4" . 414/34. 3/4" DRAIN ..GRAVEL • vso:n (20mrti) CONCRETE BLOCKS WIRE 'SCREEN OR A FILTER FABRIC IPLAN VIEW 3/4'! DRAIN GRAVEL UOITal) • CATCH BASIN COVER POND HEIGHT—A ,oww-Low WATER t' t A• Emir WIRE SCRgy CURB INLET FILT,Ett CATCH BASIN 2x4 WOOD STUD (1.0060'TIMBER ,STOD) SECTION A-A l NOtt$:, 1.. USE'BLOCK AND GRAVEL TYPE SEDIMENT BARRIER WHEN CURB INLET IS LOCATED IN GENTLY SLOPING SEGMENT, WHERE WATER CAN POND AND ALLOW SEDIMENT TO SEPARATE FROM RUNOFF. 2, BARRIER. SHALL ALLOW FOR OVERFLOW FROM SEVERE STORM EVENT. .3. INSP.Fer BARRIPS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENT NO GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY 1N4yEbridtM BLOCK AND GRAVEL CURB INLET PROTECTION 1/912009 2009 Surface Water Design Manual—Appendix D D-54 D.3.5 SEDIMENT RETENTION FIGURE D.3.5.H CURB AND GUTTER BARRIER PROTECTION BACK OF SIDEWALK Wil;11:3/NO TO OVERLAP ONTO CURB INLET • 1 RUNOFF , • — \\\._ CURB FACE - pkt_wAyf GUTTER DRAIN GRATE OfrAVEL,FILLED SANDBAGS STACKED TIGHTLY PLAN VIEW) NOTES: 1.. PLAGE CURB 1YPE SEDIMENT BARRIERS ON GENTLY SLOPING STREET SEGteNT8, WHERE WATER CAN .POND AND ALLOW SEDIMNENT TO ,SEPAWE FROM RUNOFF. 2. - ANDBAGS OF :EjTHER BURLAP OR WOVEN GEOTEXTILE FABRIC, ARE FIIIED WITH 9RAVEE, LAYERED AND PACKED TIGHTLY, (3, LEAVE A .-ONE SANDBAG CAP IN THE TOP ROW TO PROVIDE A SPILLWAY FOR ovERFLOW. 4. 1NSPEOrtrARRIERS AND REMOVE 'gEDIMENT AFTER EACH STOR NI EVENT. SEDIMENT AND GfAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEVATELY. CURB AND GUTTER RAMER 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-55 • D.3.6 SURFACE WATER COLLECTION • FIGURE D.3.6.A SKETCH PLAN OF SURFACE WATER CONTROLS r FLOW / '-----(r�„ PIPE SLOPE DRAIN ,;� '� �1 INTERCEPTOR DIKE II Hi iii II _,�� TOP OF SLOPE 'OUTLET PROTECTION r TOE OF SLOPE 111rDICDTCH It 110,, SEDIMENT POND - ti - _ SILT FENCE - - `\ STREAM D.3.6.1 INTERCEPTOR DIKE AND SWALE Code: ID or IS Symbol: io ow or s im► Purpose Interceptor dikes and swales intercept storm runoff from drainage areas on or above disturbed slopes and convey it to a sediment pond or trap. They may also be used to intercept runoff from undisturbed areas and convey the runoff to a point below any exposed soils. Interception of surface water reduces the possibility of slope erosion. Interceptor dikes and swales differ from ditches(see Section D.3.6.3)in that they are intended to convey smaller flows along low-gradient drainage ways to larger conveyance systems such as ditches or pipe slope drains. Conditions of Use Interceptor dikes and swales are required in the following situations: 1. At the top of all slopes in excess of 3H:1 V and with more than 20 feet of vertical relief. 2. At intervals on any slope that exceeds the dimensions specified in this section for the horizontal spacing of dikes and swales. Design and Installation Specifications 1. See Figure D.3.6.B for details of an interceptor dike and Figure D.3.6.0 for an interceptor swale. 2009 Surface Water Design Manual—Appendix D 1/9/2009 0-57 SECTION D.3 ESC MEASURES 2. Interceptor dikes and swales shall be spaced horizontally as follows: Average Slope Slope Percent Flowpath Length 20H:1 V or less 3-5% 300 feet (l0 to 20)H:I V 5-10% 200 feet (4 to 10)H:I V 10-25% 100 feet (2 to 4)H:1V 25-50% 50 feet 3. For slopes steeper than 2H:1V with more than 10 feet of vertical relief,benches may be constructed or closer spaced interceptor dikes or swales may be used. Whichever measure is chosen,the spacing and capacity of the measures must be designed by the engineer and the design must include provisions for effectively intercepting the high velocity runoff associated with steep slopes. 4. If the dike or swale intercepts runoff from disturbed areas, it shall discharge to a stable conveyance system that routes the runoff to a sediment pond or trap(see Section D.3.5). If the dike or swale intercepts runoff that originates from undisturbed areas,it shall discharge to a stable conveyance • system that routes the runoff downslope of any disturbed areas and releases the water at a stabilized outlet. 5. Construction traffic over temporary dikes and swales shall be minimized. Maintenance Standards 1. Damage resulting from runoff or construction activity shall be repaired immediately. 2. If the facilities do not regularly retain storm runoff,the capacity and/or frequency of the dikes/swales shall be increased. FIGURE D.3.6.B INTERCEPTOR DIKE 2:1 MAX. SLOPE DIKE MATERIAL COMPACTED 2' MIN. 90% MODIFIED PROCTOR r r 18" MIN. [l —III - =111111-11I I I 1=1 11=II1i=11 _I !-I I -I DIKE SPACING DEPENDS ON SLOPE GRADIENT FIGURE D.3.6.0 INTERCEPTOR SWALE 2:1 MAX. SLOPE LEVEL BOTTOM /4`�11I-11II141 1' MIN. _— - SII-SII—ISI-II- _111=--111:=111-1-111=1 1- _ —111- _111-1111 11-_111=1 I =111=1 I I=1 2' MIN. SWALE SPACING DEPENDS ON SLOPE GRADIENT 1/9/2009 2009 Surface Water Design Manual—Appendix D D-58 D.3.6 SURFACE WATER COLLECTION a) Relief drains are used either to lower the water table in large,relatively flat areas,improve the growth of vegetation,or to remove surface water. They are installed along a slope and drain in the direction of the slope. They may be installed in a grid pattern,a herringbone pattern,or a random pattern. b) Interceptor drains are used to remove excess groundwater from a slope,stabilize steep slopes, and lower the water table below a slope to prevent the soil from becoming saturated. They are • installed perpendicular to a slope and drain to the side of the slope. They usually consist of a single pipe or single pipes instead of a patterned layout. 2. Size of Drains—Size subsurface drains to carry the required capacity without pressurized flow. Minimum diameter for a subsurface drain is 4 inches. 3. Outlet—Ensure that the outlet of a drain empties into a channel or other watercourse above the normal water level. Maintenance Standards 1. Subsurface drains shall be checked periodically to ensure that they are free flowing and not clogged with sediment or roots. 2. The outlet shall be kept clear and free of debris. 3. Surface inlets shall be kept open and free of sediment and other debris. 4. Trees located too close to a subsurface drain often clog the system with roots. If a drain becomes clogged,relocate the drain or remove the trees as a last resort. Drain placement should be planned to minimize this problem. 5. Where drains are crossed by heavy equipment,the line shall be checked to ensure that it is not crushed and have adequate cover protection. D.3.6.4 DITCHES Code: Dl Symbol: Purpose Ditches convey intercepted runoff from disturbed areas to and from sediment ponds or traps. They also convey runoff intercepted from undisturbed areas around the site to a non-erosive discharge point. Conditions of Use Ditches may be used anywhere that concentrated runoff is to be conveyed on or around the construction site. Temporary pipe systems may also be used to convey runoff. Design and Installation Specifications 1. Channels and ditches shall be sized to accommodate the developed condition 10-year KCRTS 15- minute peak flow with 0.5 feet of freeboard. If no hydrologic analysis is required for the site,the Rational Method may be used [see Section 3.2.1 of the Surface Water Design Manual(SWDM)]. 2. See SWDM Section 4.4.1 for open-channel design requirements. 3. The only exception to the requirements of SWDM Section 4.4.1 is the use of check dams,rather than grass lining,for channels in which the design flow velocity does not exceed 5 fps. See Figure D.3.6.E for details on check dam installation. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-61 SECTION D.3 ESC MEASURES Maintenance Standards I. Any sediment deposition of more than 0.5 feet shall be removed so that the channel is restored to its design capacity. 2. If the channel capacity is insufficient for the design flow, it must be determined whether the problem is local(e.g.,a constriction or bend)or the channel is under-designed. If the problem is local,the channel capacity must be increased through construction of a berm(s)or by excavation. If the problem is under-design,the design engineer shall be notified and the channel redesigned to a more conservative standard to be approved by King County. 3. The channel shall be examined for signs of scouring and erosion of the bed and banks. If scouring or erosion has occurred,affected areas shall be protected by riprap or an erosion control blanket or net. FIGURE D.3.6.E CHECK DAMS ROCK MUST COMPLETELY COVER THE BOTTOM AND SIDES OF THE DITCH T \,_�A 6" MIN. �� T �d •, ��'��''-e 24 MIN. Nukukowillkila :111 0716.4111,!- CROSS SECTION 2:1 SLOPES — at4 2"--4" ROCK 1 I - A B lily l l I V1 -11 i III= L4.01-.1r-AL—�.� -�l i �—III—T==.1 I — „ L = THE DISTANCE SUCH THAT POINTS '' T-1 I IH I I=1= A AND B ARE OF EQUAL ELEVATION -- -I CHECK DAM SPACING 1/9/2009 2009 Surface Water Design Manual—Appendix D D-62 D.3.6 SURFACE WATER COLLECTION 0.3.6.5 OUTLET PROTECTION Code: OP Symbol •~`•'•'��•.: Purpose Outlet protection prevents scour at conveyance outlets. Conditions of Use Outlet protection is required at the outlets of all ponds,pipes,ditches,or other approved conveyances, and where runoff is conveyed to a natural or manmade drainage feature such as a stream,wetland,lake,or ditch. Design and Installation Specifications For the standard pipe slope drains in Section D.3.6.2 and other smaller conveyance systems,the standard rock pad(6 feet by 8 feet)made of I-foot thick quarry spall is adequate. For all other outlets,the outlet protection shall meet the requirements of the "Outfalls"section of Core Requirement#4 and Section 4.2.2 of the Surface Water Design Manual. Maintenance Standards for Outlet Protection If there is scour at the outlet,the eroded area shall be protected with more conservative measures proposed by the design engineer and approved by King County. D.3.6.6 LEVEL SPREADER Code: LS Symbol: Purpose Level spreaders convert concentrated runoff to sheet flow and release it onto areas stabilized by existing vegetation. Conditions of Use Level spreaders may be used where runoff from undisturbed areas or sediment retention facilities is discharged. This practice applies only where the spreader can be constructed on undisturbed soil and the area below the level lip is vegetated and low gradient(see below). Note:Level spreaders are conceptually an ideal way to release storm water since the vegetation and soil allow for the removal offnes from runoff that cannot be removed by settling or filtration. Unfortunately, the performance record of spreaders in the field is dismal. They are frequently under-designed and, despite the best installations, are rarely perfectly level, which results in the release of stormwater at a particular point. This concentrated runoff can result in catastrophic erosion downslope. Given such design failures, the use of spreaders Is not encouraged. However, where slopes are gentle and the water volume is relatively low, spreaders may still be the best method. When proposing their use, the designer shall carefully evaluate the site for possible concerns. Design and Installation Specifications I. See Figure D.3.6.F for detail. Other designs may be used subject to County approval. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-63 SECTION D.3 ESC MEASURES D.3.8 DUST CONTROL Preventative measures to minimize the wind transport of soil shall be taken when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources or adjacent properties. Purpose:To prevent wind transport of dust from exposed soil surfaces onto roadways,drainage ways,and surface waters. When to Install: Dust control shall be implemented when exposed soils are diy to the point that wind transport is possible and roadways, drainage ways,or surface waters are likely to be impacted. Dust control measures may consist of chemical,structural,or mechanical methods. Measures to Install: Water is the most common dust control(or palliative)used in the area. When using water for dust control,the exposed soils shall be sprayed until wet, but runoff shall not be generated by spraying. Calcium chloride,Magnesium chloride,Lignin derivatives,Tree Resin Emulsions,and Synthetic Polymer Emulsions may also be used for dust control. Exposed areas shall be re-sprayed as needed. Oil shall not be used for dust control. The following table lists many common dust control measures. Some of the measures are not recommended for use in King County and must have prior approval prior to use from the DDES inspector assigned to specific projects. 119/2009 2009 Surface Water Design Manual—Appendix D D-66 D.3.8 DUST CONTROL Y' {`a7;.;%€4:14,17 'i/>`Mgiin` z 7 P ;t ,41 ii.t t{. 1iriils e k� : 's 11 � h it'd � fl5 i� �a�_3 ,, fiiU ;'Fef �" i}r t st ]tyy?Pt• ttsj /,.t i({ Ori, },44.4t�' w f R 4� 1(� `I,}y X}PN ycf{�it tlj s , at - - k i - � §tt}'s yr y�1/ )� �p�t-<Y 7� 7� �.e�{r'#�®IAIJU1t©�E�1/0������)I �Rm tl�l'� �y{ /Ka fir ` Jt z }L. <0..},J,?�. `tFt ; ("l .1L h. t,Jl ,,). jru..;e..wr�r #��P�E,ti.,•��.tisi.,..- ,:i"; METHOD CONSIDERATIONS SITE PREPARATION RECOMMENDED APPLICATION RATE Water -Most commonly used practice For all liquid agents: 0.125 gal/sq yd every -Evaporates quickly -Blade a small surface 20 to 30 minutes -Lasts less than 1 day -Crown or slope surface to avoid ponding -Compact soils if needed -Uniformly pre-wet at 0.03—0.3 gal/sq yd -Apply solution under pressure. Overlap solution 6—12 inches -Allow treated area to cure 0—4 hours -Compact area after curing -Apply second treatment before first treatment becomes ineffective Salts -Restricts evaporation Apply 38%solution at Calcium -Lasts 6-12 months 1.21 Um2(0.27 gal/yd2) Chloride -Can be corrosive or as loose dry granules (CadI) -Less effective in low humidity per manufacturer -Can build up in soils and leach by rain Magnesium -Restricts evaporation Apply 26—32%solution Chloride -Works at higher temperatures and lower at 2.3 Um2(0 5 (MgCI) humidity than CaCI gallyd2) -May be more costly than CaCI Sodium -Effective over smaller range of Per Manufacturer Chloride conditions (NaCl) -Less expensive -Can be corrosive -Less effective in low humidity Silicates -Generally expensive -Available in small quantities -Require Second application Surfactants -High evaporation rates -Effective for short time periods -Must apply frequently Copolymers -Forms semi-permeable transparent 750—940 L/ha(80— crust 100 gal/ac) -Resists ultraviolet radiation and moisture induced breakdown -Last 1 to 2 years Petroleum -Used oil is prohibited as a dust control Use 57—63%resins as Products method base. Apply at 750— -Bind soil particles 940 Uha(80-100 -May hinder foliage growth gal/ac) -Environmental and aesthetic concerns -Higher cost Lignin -Paper industry waste product Loosen surface 25-50 Sulfonate -Acts as dispersing agent mm (1 —2 inches) Need -Best in dry climates 4-8%fines -Can be slippery -Will decrease Dissolved Oxygen in waterways therefore cannot be used adjacent to surface water systems Vegetable -Coat grains of soils, so limited binding Per Manufacturer Oils ability -May become brittle -Limited availability Spray on -Available as organic or synthetic Per Manufacturer Adhesives -Effective on dry, hard soils -Forms a crust -Can last 3 to 4 years 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-67 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL D.4 ESC PERFORMANCE AND COMPLIANCE PROVISIONS The changing conditions typical of construction sites call for frequent field adjustments of existing ESC measures or additional ESC measures in order to meet required performance. In some cases,strict adherence to specified measures may not be necessary or practicable based on site conditions or project type. In other cases,immediate action may be needed to avoid severe impacts. Therefore,careful attention must be paid to ESC performance and compliance in accordance with the provisions contained in this section. D.4.1 ESC SUPERVISOR For projects in Targeted,Full,or Large Project Drainage Review,the applicant must designate an ESC supervisor who shall be responsible for the performance,maintenance,and review of ESC measures and for compliance with all permit conditions relating to ESC as described in the ESC Standards. The applicant's selection of an ESC supervisor must be approved by King County. For projects that disturb one acre or more of land,the ESC supervisor must be a Certified Professional in Erosion and Sediment Control(see www.cpesc.net for more information)or a Certified Erosion and Sediment Control Lead whose certification is recognized by King County.° King County may also require a certified ESC supervisor for sites smaller than one acre of disturbance if DDES determines that onsite ESC measures are inadequately installed, located,or maintained. For larger,more sensitive sites,King County may require a certified ESC supervisor with several years of experience in construction supervision/inspection and a background in geology,soil science,or agronomy. Typically, if a geotechnical consultant is already working on the project,the consultant may also be the designated ESC supervisor. The design engineer may also be qualified for this position. This requirement shall only be used for sensitive sites that pose an unusually high risk of impact to surface waters as determined by DDES. At a minimum,the project site must meet all of the following conditions in order to require the applicant to designate a certified ESC supervisor with such expertise: • Alderwood soils or other soils of Hydrologic Group C or D • Five acres of disturbance • Large areas(i.e.,two or more acres)with slopes in excess of 10 percent. Proximity to streams or wetlands or phosphorus-sensitive lakes,such as Lake Sammamish,shall also be a factor in determining if such expertise in the ESC supervisor is warranted. However,proximity alone shall not be a determining factor because even projects that are a considerable distance from surface waters can result in significant impacts if there is a natural or constructed drainage system with direct connections to surface waters. The name,address,and phone number of the ESC supervisor shall be supplied to the County prior to the start of construction. A sign shall be posted at all primary entrances to the site identifying the ESC supervisor and his/her phone number. The requirement for an ESC supervisor does not relieve the applicant of ultimate responsibility for the project and compliance with King County Code. 8 King County recognition of certification means that the individual has taken a King County-approved third party training program and has passed the King County-approved test for that training program. 2009 Surface Water Design Manual—Appendix D 1/9/2009 D-69 . 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S�4�;:. �•� ���..� , t .-, - .i- I� RELOCAIE EX1571NG SIORAGE UIYT.COORDINA7E NEW LOCAD961 MTH C+JhEP. , � 2�"` ' `` ; , � / , .. - = � ' IS SEE JRd47ECTUNAI PLhliS�LR 14�ER10.V COURTYhRO OEY�k'1115134 � _ ��I�ea� ` d'�"'/ . � : a� �y� � ��,�, � ;�'� , � � . 16 OEL(CW91 EXIS7WG STORN 6RAN S71iUCNRE � � � � ��sre . 16� - j - � - CMEroNw� 'M r��� � � i t 17 PROTECI Cb51fHC Tli£E TO 4DJN4 S. g�yg�y� -� �. . : 11. _ ._. ~�����ad - - r . t•, � �� � -�- OQ�'�"`�a°C9y lrM�caP°Mhk� �� � . _. _--- cmo-�w.a�� r' _ _ : � F - . \, IS PRO7ECTC%ISIWGWAfERUyE O6Jd Ne�q�. ��p,I4nw� � � . . . - .;ft � , � i � �' � — 14 PROIECI U051fNC 5�1lTMY$E4ER UNE � � � `- -- � ��� -��� ��, - 20 PROIECI E10511NG BfNpi(IYP.1 � � 2N87 - i - ` , � . _ _ t`Y ' '� [heded iareeMpllmre�o q1YS1se0vUs .� °+rorn��� � � . _. --� � _- -- _ y; ., _ _ ..�� �'� - � 2� PROTECI E10SRNC flFILINC �3�CNAL b� Q � s �-/ -.-� �_ _. - -- /: �- _ �-� � "_� .�-i -_ � -e - - YT DE1LOlx9�LONCRE�E TO f116➢NG,qP.T(3 P/1lFlS) �,.i:_ �-�%-i:�r — -- _ - _ -- _ __ �-- - _�„z-tf_�' ���""�.'e-.a`�-. ivar T A C O M A - 3 E A T T t E "-' � - - - - Y3 llElfOl3�E%�S71HG BERM�IND UNGSCAPIHG MF'ROl(MIA7E i4RS SHGYd7.SEE . 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SEE SNfEI CI.1 FCAt COHSTRtICRON SfUUENCF. �J.J / �.' � � - - _ .85 � �. �- O1 °ROfECT FlOSTKG FFtiGE � C E `� / -� a�, - _ 4� - � �..� - ��.'�e r �� .,... ?. SEE SMEE7 CI.�Fpt ESC SlANDARD NOIES �e p� O olt0lECT E70S14lG SfORY STRIICRdtE AND A559pF1ED APWR7EHMlCES � �-���� - . __- ' �.•'� }. OEAlOUPAMI:1T IS IH:k7ENT OF 1HE ipRK UNJEF t�il$CpH7RAC(TO 3 PROiECT EIOSTdh;5lORIY OR►A ll!€ � ��' /:�.5 - �� � � � IHOICAIE 6Y IM���IM'G UR`5 REnWIFED!OR fW�COH iRUCII(IN.I7 O O ��' � 1 . � ' 1 � VS 1F�COkIRACTO4S NESPi1F73BIUTY TD fULLY Ri.�M1EN 1Hf 91E OO ���SH E7(IS114C FEkCC/8.4CXS70P . z � -- a"'"��'� yp �; i I CONDITAYS fND i0 CDRRELAIC hIESE OBSERVAT�NS W7H lliC PROJECS e5 U 9 O°'f5`+ ' S 9L!fENCE WqtN ANJ W0.UJE ALL N[OESSAHY OELIOUIIOH,NNt1HEfl SHONlF IXi � Cf.4 � � �,`� , � � i �f ��'�O ■ NDf,ANO HOI�E ML SUCH CO515 W 1HC BASF&D. O �pq��IIlIIS � - . T j(�IpqRARY IN7FRiEPTOR�ITQi W � `'�l. ,�O Y ""l .A � .. �.. � 1. 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PR91EC7 EX51piG SiWIiARY SE%fR 11NE i ' " • �y 1' � -._ . -'�-' n�ws�wat�w ,_.. . .. . .- _ - � _ '_-. . .�.,_ _ �-.___ .. _ _ :` �+ 16 i r 6 9 �•` � �� 13 �. 1 � {�@ � • � ' : N�-- ,� � l, - - -� _ - • - --.. �R " - . �'` _' 12 �`v ; '� `� ' -<� �i.:r��.�����/_• -� - � ,� �- 14 PIMJ'ECI ElQS11CC NAIER 11NE hND ASSOpA1;0 1➢AURIENAHCfS W� , . y . --"� ---- f .,�•.. i� - .,� .-��3� -.- '- - .y• � ✓�`.,�- �` � '. .� r _ . - '�`+ � -. PROKCf El(1516C fl7E R'A7R/NI ANO ASSOPAIED APPUBTE1UHlE Z � _ T7 _� b -�.. ._. -_-_ - ----- ' '------�- --- .__ ..:. _ 13 �. , - � , _ `� _ _'�. � �,�� x. � 15 _ c 'J � ��;� -� � _ ! �i• �.�n- \� � -���----� - ,� .S. �' ? � 16 PROIEG�£7BSIpIC UIUtt VA0.1 AND ASSCqAhI}l�PPUARMAN�S '.." ..I ; '- ��y - '� � � � .: *- .-.. . . _ �:�- '- �'4.nf Lw . . .... _, �.._. ' .., . , .... - .'`� fi � �1 _ 17 PflC7EC.EXISIWC PO#R LNE _J' � �- �. -- � _ . _ __ _ .._ - ..- . .� /`- ._. ., � +; �i _ o� r 4■ - '.Y ,_ u .. - - --- _ - 1 1 , -,_, .Y.: ' �1-' .., .. 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