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18025 - NPR DRAINAGE REPORT 12.18.18YELM AUTO RECYCLING D R A I N A G E R E P O R T S E P T E M B E R 2 0 1 8 R E V I S E D D E C E M B E R 2 0 1 8 Table of Contents Part 1 – Project Site Analysis and Data Part 2 – Site Development Layout Part 3 – Offsite Analysis Report Part 4 – Applicable Minimum Requirements Part 5 – Permanent Stormwater Control Plan Part 6 – Source Control BMPs Part 7 – Construction SWPPP Part 8 – Special Reports and Studies Part 9 – Other Permits Part 10 – Operational and Maintenance Plan Part 11 – Bond Quantities and Financial Responsibility Part 12 – Grading and Drainage Plans APPENDIX 1 – CALCULATIONS APPENDIX 2 – GEOTECHNICAL REPORT ____________________________________________________ 18025 Drainage Report 1-1 Project Engineer Prepared by: RB Engineering, Inc. (RBE) PO Box 923 Chehalis, WA 98532 (360) 740-8919 Robertb@RBEngineers.com Contact: Robert W. Balmelli PE RBE Project: 17041 Prepared for: NPR Holdings LLC Ubaida Mufrej 3655 E. Marginal Ways Seattle, Washington 98134 ubaida@safariexports.com Reference: 2014 WSDOE Stormwater Manual Project Engineers Certification “I hereby certify that this Drainage and Erosion Control Plan for Yelm Auto Recycling has been prepared by me or under my supervision and meets minimum standards the Stormwater Management Manual for Western Washington and normal standards of engineering practice. I hereby acknowledge and agree that the jurisdiction does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities designed by me.” Project Engineers Stamp ____________________________________________________ 18025 Drainage Report 1-2 PART 1 – PROJECT SITE ANALYSIS AND DATA Permit Requested: Site Plan Review Other Permits Required: Building Permit Grading/Earthwork SEPA Review Agency Permit No.: Pending Site Address: 939 Northern Pacific Rd Yelm, Washington 98597 Section, Township, Range: Section 19 Township 17 Range 02E, W.M Total Site Area: 13.93 Acres Zoning: I - Industrial Project Overall Description The project includes the development of an auto wrecking yard named, Yelm Auto Recycling, on lot 64300900200. Development will include 4 structures to be used for office space, storage and general shop/maintenance space. Construction will also include onsite customer parking, graveled and paved vehicle storage yards, water, sewer, and power service, stormwater facilities. Frontage improvements are proposed, but will be deferred until required by the City. Proposed Flow Control Improvements The flow control facilities consist of bioretention cells, infiltration trenches and infiltration cells. Test pits dug at the facility locations revealed infiltration rates more than 100 in/hr. For design purposes, stormwater facilities were modeled with 20 in/hr. The soils report can be found in Appendix #2 of this document. Proposed Water Quality Improvements The water quality facilities consist of bioretention cells. The bioretention cells are designed to treat 91% of the runoff profile. The bioretention cells utilize a 12 in/hr design infiltration rate with a Ksat safety factor of 4. Proposed Conveyance System The proposed conveyance systems will consist of Type I catch basins and conveyance pipe in various sizes to distribute stormwater to the proposed stormwater facilities. Proposed Discharge Location The project site will infiltrate all runoff at the proposed infiltration trenches/cells. Downstream Condition The site contains a ridge running SE to NW. The ridge effectively splits the site with stormwater ____________________________________________________ 18025 Drainage Report 1-3 naturally draining to the east/west boundaries. The proposed improvements will have no effect on the existing conditions as runoff will be contained on-site. Given the sites native well- draining soils it is likely that stormwater presently is infiltrated before leaving the site. 100-year overflows will be directed to undeveloped property through natural drainage routes. See Section 3 for a map of the offsite overflow path. Onsite Soils and Geology An on-site soils report was completed for this project site be Parnell Engineering, LLC. A copy of the report is included in Appendix 2 of this document. The report stated that infiltration on-site is feasible with calculated infiltration rates exceeding 100 in/hr. The report recommends a design infiltration of 20 in/hr be used. Based upon this information the storm design concept of infiltration was selected. ____________________________________________________ 18025 Drainage Report 2-1 PART 2 – SITE DEVELOPMENT LAYOUT Project Topography The site topography is nearly level to gently sloping. Elevations range from a high of 338 ft. at the south-central portion of the site to a low of 328 ft. at the NE corner of the site. Land Use and Ground Cover Site vegetation consists of sparsely located conifer trees along with Scotch Broom, indigenous brush and field grass. The subject site is bounded by rural residential property to the north, undeveloped property to the east, Northern Pacific Road NW to the south, and a private drive- way to the west. Natural or Man-Made Drainage Patterns The site contains a ridge running SE to NW. The ridge effectively splits the site with stormwater naturally draining to the east/west boundaries. The proposed improvements will have no effect on the existing conditions as runoff will be contained on-site. Given the sites native well- draining soils it is likely that stormwater presently is infiltrated before leaving the site. Tributary and Discharge Points of Flow There are no tributary points of flow. The centralized ridge on-site prevents off-site flows from entering the project. Historical Drainage Problems RBE is not aware of any historical drainage problems for this site. Existing Utilities (Storm, Sewer, Water) The existing utilities available to site include power, water, sewer, storm. Erosion Potential The site has a slight erosion potential. As part of the development plans a detailed Erosion Control Plan and Storm Water Pollution Prevention Plan will be prepared and submitted with the final drainage report for use during site construction to minimize erosion and mitigate sedimentation within and off the site. Critical Areas Onsite The site does not contain any critical areas Existing Fuel Storage Tanks Review of the onsite parcels resulted in no evidence of existing fuel storage tanks above or below ground for this property. Groundwater Wells The property does not include any onsite ground water wells. ____________________________________________________ 18025 Drainage Report 2-2 Septic Systems There are no septic systems on-site. Aquifer Recharge Area The site is within the City of Yelm Aquifer Recharge Area. Wellhead Protection Area The site is not within any wellhead protection areas for public utilities. ____________________________________________________ 18025 Drainage Report 3-1 PART 3 – OFFSITE ANALYSIS REPORT RBE staff visually inspected the site and offsite surrounding areas. With all runoff being infiltrated an offsite analysis was deemed unnecessary. 100-year overflows will be directed offsite through undeveloped natural drainage paths. See the offsite drainage path map on the following page. Overlow Route 5,762 12/16/2018 Note: Legend Map Created Using GeoData Public Website The information included on this map has been compiled by Thurston County staff from a variety of sources and is subject to change without notice. Additional elements may be present in reality that are not represented on the map. Ortho-photos and other data may not align. The boundaries depicted by these datasets are approximate. This document is not intended for use as a survey product. ALL DATA IS EXPRESSLY PROVIDED ‘AS IS’ AND ‘WITH ALL FAULTS’. Thurston County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. In no event shall Thurston County be liable for direct, indirect, incidental, consequential, special, or tort damages of any kind, including, but not limited to, lost revenues or lost profits, real or anticipated, resulting from the use, misuse or reliance of the information contained on this map. If any portion of this map or disclaimer is missing or altered, Thurston County removes itself from all responsibility from the map and the data contained within. The burden for determining fitness for use lies entirely with the user and the user is solely responsible for understanding the accuracy limitation of the information contained in this map. Authorized for 3rd Party reproduction for personal use only. Scale 1: Published: Feet 2500 500 Label - Parcel Number Parcel Boundaries Contours 2ft 1996 (NGVD 29) Roads - Major Major Roads Ramp I 5; US 101 Roads (Large Scale) Railroads County Border 2018©Thurston County ____________________________________________________ 18025 Drainage Report 4-1 PART 4 – APPLICABLE MINIMUM REQUIREMENTS The minimum requirements for stormwater development are listed in Volume I of the 2012 SMMWW as amended in December 2014. Determination of applicable minimum requirements area determined in Section 2.4 of the Manual. Applicable Criteria Areas Existing Site Impervious Coverage 0.86 AC New Plus Replaced Impervious Surface 12.45 AC Vegetation Area Converted to Lawn or Landscaped Area 0.73 AC Land Disturbing Area 13.22 AC ____________________________________________________ 18025 Drainage Report 4-2 Based on the thresholds given in Figures 2.4.1, the project must address or comment on Minimum Requirements #1 through #9. These requirements as they apply to the project are discussed in more detail below. Minimum Requirement (MR) #1 – Stormwater Site Plans: This project meets requirement #1 by preparation of this Drainage Report and the Drainage Control Plans. MR #2 – Construction Storm Water Pollution Prevention Plan: This project is designed to meet the intent of Construction SWPPP Elements #1 through #13 as detailed in Section 2.5.2. A SWPPP will be created as a standalone document for this project and submitted with the final drainage report. MR #3 – Source Control of Pollution: All known, available and reasonable source control BMPs shall be applied to the project to limit pollutants coming in contact with stormwater. The BMPs for this project will be incorporated into the project’s Final Operation and Maintenance Plan. MR #4 – Preservation of Natural Drainage Systems/Outfalls: Proposed stormwater will be infiltrated on-site. There will be no effect to the sites natural drainage. MR #5 – On-Site Stormwater Management: This requirement will be met by choosing any BMP and demonstrating compliance with the LID Performance Standard. Bioretention and infiltration treches/cells will be utilized to infiltrate 100% of the runoff onsite. Soil Amendments will be utilized for all pervious areas. MR #6 – Runoff Treatment: This project exceeds the criterion for this requirement. Bioretention cells will be used to provide treatment. An oil control catch basin will be installed on the eastern portion of the lot where vehicles will be initially stored and cleaned. MR #7 – Flow Control: This project exceeds the criterion for this requirement. Bioretention cells and infiltration trenches/cells will be used to provide flow control. The LID Performance Standard will be met by infiltrating 100% of the project. ____________________________________________________ 18025 Drainage Report 4-3 MR #8 – Wetlands Protection: There are no wetlands within the proposed project limits. MR #9 – Operation & Maintenance: An Operation and Maintenance Manual has been created as a standalone document for the developer and property owners. ____________________________________________________ 18025 Drainage Report 5-1 PART 5 – PERMANENT STORMWATER CONTROL PLAN Existing Site Hydrology Existing site hydrology is based on our site investigation, field topographic survey, aerial topographic mapping and completed soils review for the subject project. The site consists of the basins outlined below. Pre-developed Basins Current Land Use: Vacant Lot Land Use Assumptions and Site Parameters Basin ID Land Use Cover Slope Acres Hydrologic Group Comments P1 Forested Flat 0.34 A P2 Forested Flat 6.77 A P3 Forested Flat 5.53 A P4 Forested Flat 0.59 A Total 13.23 Developed Site Hydrology A complete summary for each developed sub-basin is included in the chart below. Because of the existing topography, the site is considered a single basin for overall development purposes. Basin Summary Proposed Land Use: Commercial – Auto Recycling Land Use Assumptions and Site Parameters Basin ID Land Use Cover Slope Acres Hydrologic Group Comments D1 Paved Flat 0.15 Sidewalks Flat .05 Landscape Flat 0.14 A 0.34 D2 Gravel Flat 5.66 Asphalt Flat 0.82 Sidewalk Flat 0.03 Roof Flat 0.07 Landscape Flat 0.18 6.76 ____________________________________________________ 18025 Drainage Report 5-2 D3 Gravel Flat 4.28 A Asphalt Flat 1.15 Roof Flat 0.08 Landscape Flat 0.02 5.53 D4 Aspahlt Flat 0.14 Sidewalk Flat 0.05 Landscape Flat 0.40 A 0.59 Total 13.23 Flow Control Analysis The proposed storm water facilities were designed using the MGS Flood storm water model. This project provides 100% infiltration and meets both the LID Performance Standard and Stream Protection Duration. See Appendix #1 of this report for calculations. Water Quality Analysis The drainage basins delineated for this project will have openly exposed pollution generating impervious surfaces. These tributary areas will be treated using the following treatment technologies listed under the associated drainage basins. See Appendix #1 of this report to see that each of the 4 developed basins will infiltration at least 91% of the runoff profile through a bioretention cell. Pollutants of Concern Oil Control Facility A portion of this project will be required to provide oil control facility based on the analysis below. An Oil Control catch basin will be installed in the area for initial intake and cleaning of the vehicles. This area is in the eastern portion of the lot in Basin #3. Oil Control Determination Chart ADT 100 Vehicles or Greater per 1000 SF Building Area Yes or No Site Subject to Petroleum Storage or Transfer Greater than 1500 Gallons per year.Yes or No Site have Parking, Storage or maintenance of 25 or more vehicles over 25 Tons gross weight. (Trucks, Buses, Trains, Heavy Equipment) Yes or No Road Intersection with measured ADT of 25000 vehicles or more on main roadway and 15000 vehicles or more on intersection roadway. Yes or No ____________________________________________________ 18025 Drainage Report 5-3 Phosphorus Control Required Oil Control Determination Chart Local Government Require Phosphorus control Yes or No Enhanced Treatment Required Oil Control Determination Chart Site discharge directly to fresh waters or conveyance systems tributary to fresh waters?Yes or No Site uses infiltration strictly for flow control and the discharge is within 1.4 mile of fresh water designate for aquatic life?Yes or No Site an industrial project site?Yes or No Site a commercial project site?Yes or No Site a multi-family residential project site Yes or No UGA – Fully controlled and partially controlled limited access highways with AADT 15000 or greater No UGA - All other roads with and AADT of 7500 or greater.No Outside UGA - Roads with and AADT of 15,000 or greater unless discharging to a Strahler order Stream or large No Outside UGA - Road with an AADT of 30,000 or greater if discharging to a 4th Strahler order stream or larger.No Selected BMP’s: (See Appendix #1 for sizing) Basin D1 Water Quality Facility: BMP T7.30 – Bioretention Cell (39’ L x 3’ W) Flow Control Facility: BMP – Infiltration Trench (28’ L x 4’ W x 3’ D) Basin D2 Water Quality Facility: BMP T7.30 – Bioretention Cell (520’ L x 8’ W) Flow Control Facility: BMP – Infiltration Cell (532’ L x 4.6’ W) Basin D3 Water Quality Facility: BMP T7.30 – Bioretention Cell (540’ L x 6.5’ W) Flow Control Facility: BMP – Infiltration Cell (500’ L x 3.9’ W) Basin D4 Water Quality Facility: BMP T7.30 – Bioretention Cell (27’ L x 4’ W) Flow Control Facility: BMP – Infiltration Trench (26’ L x 4’ W x 3’ D) ____________________________________________________ 18025 Drainage Report 6-1 PART 6 – SOURCE CONTROL BMPS The following permanent source control BMPs will be utilized for this project and will be included in the final Operation and Maintenance Manual submitted prior to final project acceptance by the County. Landscape and Lawn Vegetation Management ________________________________________________________________________ December 2018 Stormwater Site Plan Report 1 PART 7 – CONSTRUCTION SWPPP All new development and redevelopment shall comply with Construction SWPPP Elements #1 through #12 outlined in the Manual. A full SWPPP has been prepared for this project and will be submitted for review at construction plan submittal. The project’s SWPPP is included below. Element 1: Mark Clearing Limits • Prior to beginning land disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. These shall be clearly marked, both in the field and on the plans, to prevent damage and offsite impacts. • Plastic, metal, or stake wire fence may be used to mark the clearing limits. • Suggested BMPs: BMP C101: Preserving Natural Vegetation BMP C102: Buffer Zones BMP C103: High Visibility Plastic or Metal Fence BMP C104: Stake and Wire Fence Element 2: Establish Construction Access • Construction vehicle access and exit shall be limited to one route if possible, or two for linear projects such as roadways where one access is necessary for large equipment maneuvering. • Access points shall be stabilized with quarry spall or crushed rock to minimize the tracking of sediment onto public roads. • Wheel wash or tire baths should be located on-site, if applicable. • Roads shall be cleaned thoroughly at the end of each day. Sediment shall be removed from roads by shoveling or pickup sweeping and shall be transported to a controlled sediment disposal area. Street washing will be allowed only after sediment is removed in this manner. • Street wash wastewater shall be controlled by pumping back on-site or otherwise be prevented from discharging into systems tributary to state surface waters. • Construction access restoration shall be equal to or better than the pre-construction condition. • Suggested BMPs: BMP C105: Stabilized Construction Entrance BMP C106: Wheel Wash BMP C107: Construction Road/Parking Area Stabilization ________________________________________________________________________ December 2018 Stormwater Site Plan Report 2 Element 3: Control Flow Rates • Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site, as required by local plan approval authority. • Downstream analysis is necessary if changes in offsite flows could impair or alter conveyance systems, stream banks, bed sediment, or aquatic habitat. • Where necessary to comply with Minimum Requirement #7, stormwater detention facilities shall be constructed as one of the first steps in grading. Detention facilities shall be functional prior to construction of site improvements (e.g. impervious surfaces). • Suggested BMPs: BMP C240: Sediment Trap BMP C241: Temporary Sediment Pond Refer to Volume 3, Detention Facilities Element 4: Install Sediment Controls • The duff layer, native top soil, and natural vegetation shall be retained in an undisturbed state to the maximum extent practicable. • Prior to leaving a construction site or prior to discharge to an infiltration facility, stormwater runoff from disturbed areas shall pass through a sediment pond or other appropriate sediment removal BMP. Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet the flow control performance standard of Element #3, bullet #1. Full stabilization means concrete or asphalt paving; quarry spalls used as ditch lining; or the use of rolled erosion products, a bonded fiber matrix product, or vegetative cover in a manner that will fully prevent soil erosion. The local permitting authority shall inspect and approve areas fully stabilized by means other than pavement or quarry spalls. • BMPs intended to trap sediment on site shall be constructed as one of the first steps in grading. These BMPs shall be functional before other land disturbing activities take place. • Earthen structures such as dams, dikes, and diversions shall be seeded and mulched according to the timing indicated in Element #5. • BMPs intended to trap sediment on site must be located in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off- channel areas or drainages, often during non-storm events, in response to rain event changes in stream elevation or wetted area. • Suggested BMPs BMP C230: Straw Bale Barrier BMP C231: Brush Barrier BMP C232: Gravel Filter Berm BMP C233: Silt Fence BMP C234: Vegetated Strip ________________________________________________________________________ December 2018 Stormwater Site Plan Report 3 BMP C235: Straw Wattles BMP C240: Sediment Trap BMP C241: Temporary Sediment Pond BMP C250: Construction Stormwater Chemical Treatment BMP C251: Construction Stormwater Filtration Element 5: Stabilize Soils • Exposed and unworked soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrops, flowing water, and wind. • From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days. From May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. This stabilization requirement applies to all soils on site, whether at final grade or not. These time limits may be adjusted by the local permitting authority if it can be shown that the average time between storm events justifies a different standard. • Soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. • Applicable practices include, but are not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, soil application of polyacrylamide (PAM), the early application of gravel base on areas to be paved, and dust control. • Selected soil stabilization measures shall be appropriate for the time of year, site conditions, estimated duration of use, and the water quality impacts that stabilization agents may have on downstream waters or ground water. • Soil stockpiles must be stabilized and protected with sediment trapping measures. • Linear construction activities such as right-of-way and easement clearing, roadway development, pipelines, and trenching for utilities, shall be conducted to meet the soil stabilization requirement. Contractors shall install the bedding materials, roadbeds, structures, pipelines, or utilities and re-stabilize the disturbed soils so that: − from October 1 through April 30 no soils shall remain exposed and unworked for more than 2 days and − from May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. • Suggested BMPs: BMP C120: Temporary and Permanent Seeding BMP C121: Mulching BMP C122: Nets and Blankets BMP C123: Plastic Covering BMP C124: Sodding BMP C125: Top soiling BMP C126: Polyacrylamide for Soil Erosion Protection BMP C130: Surface Roughening ________________________________________________________________________ December 2018 Stormwater Site Plan Report 4 BMP C131: Gradient Terraces BMP C140: Dust Control BMP C180: Small Project Construction Stormwater Pollution Prevention Element 6: Protect Slopes • Design, construct, and phase cut and fill slopes in a manner that will minimize erosion. • Consider soil type and its potential for erosion. • Reduce slope runoff velocities by reducing continuous length of slope with terracing and diversions, reduce slope steepness, and roughen slope surface. • Divert upslope drainage and run-on waters with interceptors at top of slope. Stormwater from off site should be handled separately from stormwater generated on the site. Diversion of offsite stormwater around the site may be a viable option. Diverted flows shall be redirected to the natural drainage location at or before the property boundary. • Contain down slope collected flows in pipes, slope drains, or protected channels. Check dams shall be used within channels that are cut down a slope. • Provide drainage to remove ground water intersecting the slope surface of exposed soil areas. • Excavated material shall be placed on the uphill side of trenches, consistent with safety and space considerations. • Stabilize soils on slopes, as specified in Element #5. • Suggested BMPs BMP C120: Temporary and Permanent Seeding BMP C130: Surface Roughening BMP C131: Gradient Terraces BMP C200: Interceptor Dike and Swale BMP C201: Grass-Lined Channels BMP C204: Pipe Slope Drains BMP C205: Subsurface Drains BMP C206: Level Spreader BMP C207: Check Dams BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam) Element 7: Protect Drain Inlets • Storm drain inlets operable during construction shall be protected so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 5 • Approach roads shall be kept clean. Sediment and street wash water shall not be allowed to enter storm drains without prior and adequate treatment unless treatment is provided before the storm drain discharges to waters of the state. • Inlets should be inspected weekly at a minimum and daily during storm events. Inlet protection devices should be cleaned or removed and replaced before six inches of sediment can accumulate. • Suggested BMPs: BMP C220: Storm Drain Inlet Protection Element 8: Stabilize Channels and Outlets • Temporary on-site conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the expected flow velocity of a 2-year, 24-hour frequency storm for the developed condition. An existing drainage ditch will provide on-site conveyance for erosion protection of the site. • Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches shall be provided at the outlets of all conveyance systems. • Suggested BMPs: BMP C202: Channel Lining BMP C209: Outlet Protection Element 9: Control Pollutants • All pollutants, including waste materials and demolition debris, that occur on site during construction shall be handled and disposed of in a manner that does not cause contamination of stormwater. Woody debris may be chopped and spread on site. • Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and non-inert wastes present on the site (see Chapter 173-304 WAC for the definition of inert waste). • Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. • Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system or to the sanitary sewer. • Application of agricultural chemicals including fertilizers and pesticides shall be conducted in a manner and at application rate that will not result in loss of chemicals to stormwater runoff. Manufacturer recommendations for application rates and procedures shall be followed. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 6 • BMPs shall be used to prevent or treat contamination of stormwater runoff by pH modifying sources. These sources include bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, and concrete pumping and mixer washout waters. Stormwater discharges shall not cause a violation of the water quality standard for pH in the receiving water. • Suggested BMPs: BMP C151: Concrete Handling BMP C152: Sawcutting and Surfacing Pollution Prevention See Volume IV – Source Control BMPs Element 10: Control De-Watering • Foundation, vault, and trench de-watering water shall be discharged into a controlled conveyance system prior to discharge to a sediment pond. Channels must be stabilized, as specified in Element #8. • Clean, non-turbid de-watering water, such as well-point ground water, can be discharged to systems tributary to state surface waters, as specified in Element #8, provided the de-watering flow does not cause erosion or flooding of receiving waters. These clean waters should not be routed through stormwater sediment ponds. • Highly turbid or contaminated dewatering water from construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam shall be handled separately from stormwater. • Other disposal options, depending on site constraints, may include: 1. infiltration, 2. transport off site in vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters, 3. on-site treatment using chemical treatment or other suitable treatment technologies, 4. sanitary sewer discharge with local sewer district approval, or 5. use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. Element 11: Maintain BMPs • Temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with BMPs. • Sediment control BMPs shall be inspected weekly or after a runoff-producing storm event during the dry season and daily during the wet season. The inspection frequency for stabilized, inactive sites shall be determined by the local permitting authority based on the level of soil stability and potential for adverse environmental impacts. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 7 • Temporary erosion and sediment control BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. Element 12: Manage the Project • Phasing of Construction Development projects shall be phased where feasible in order to prevent, to the maximum extent practicable, the transport of sediment from the development site during construction. Re-vegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities for any phase. Clearing and grading activities for development shall be permitted only if conducted pursuant to an approved site development plan (e.g., subdivision approval) that establishes permitted areas of clearing, grading, cutting, and filling. When establishing these permitted clearing and grading areas, consideration should be given to minimizing removal of existing trees and minimizing disturbance and compaction of native soils except as needed for building purposes. These permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree retention areas as may be required by local jurisdictions, shall be delineated on the site plans and the development site. • Seasonal Work Limitations From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that the transport of sediment from the construction site to receiving waters will be prevented through a combination of the following: 1. Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and 2. Limitations on activities and the extent of disturbed areas; and 3. Proposed erosion and sediment control measures. Based on the information provided and local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The local permitting authority shall take enforcement action - such as a notice of violation, administrative order, penalty, or stop-work order under the following circumstances: − If, during the course of any construction activity or soil disturbance during the seasonal limitation period, sediment leaves the construction site causing a violation of the surface water quality standard; or − If clearing and grading limits or erosion and sediment control measures shown in the approved plan are not maintained. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 8 Local governments may restrict clearing and grading activities where site conditions may present a significant risk of impact to property or critical areas. Contact the local government permitting authority for information on specific site restrictions. The following activities are exempt from the seasonal clearing and grading limitations: 1. Routine maintenance and necessary repair of erosion and sediment control BMPs, 2. Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil, and 3. Activities where there is one hundred percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. • Coordination with Utilities and Other Contractors The primary project proponent shall evaluate, with input from utilities and other contractors, the stormwater management requirements for the entire project, including the utilities, when preparing the Construction SWPPP. • Inspection and Monitoring All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. A certified professional in erosion and sediment control shall be identified in the Construction SWPPP and shall be on-site or on-call at all times. Sampling and analysis of the stormwater discharges from a construction site may be necessary on a case-by-case basis to ensure compliance with standards. The local permitting authority may establish monitoring and reporting requirements when necessary. Whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, the SWPPP shall be modified, as appropriate, in a timely manner. • Maintenance of the Construction SWPPP The Construction SWPPP shall be retained on-site or within reasonable access to the site. The Construction SWPPP shall be modified whenever there is a significant change in the design, construction, operation, or maintenance of any BMP. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 9 Project Specific Construction BMPs ________________________________________________________________________ December 2018 Stormwater Site Plan Report 10 BMP C105: Stabilized Construction Entrance Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by vehicles or equipment 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. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications • See Figure 4.2 for details. Note: the 100’ minimum length of the entrance shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100’). • 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) • Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose. • Hog fuel (wood-based mulch) may be substituted for or combined with quarry spalls in areas that will not be used for permanent roads. Hog fuel is generally less effective at stabilizing construction entrances and should be used only at sites where the amount of traffic is very limited. Hog fuel is not recommended for entrance stabilization in urban areas. The effectiveness of hog fuel is highly variable and it generally requires more maintenance than quarry spalls. 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 degradation of the subgrade support over time. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 11 • Fencing (see BMPs C103 and C104) shall be installed as necessary to restrict traffic to the construction entrance. • 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 • Quarry spalls (or hog fuel) shall be added if the pad is no longer in accordance with the specifications. • 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. • Any sediment that is tracked onto pavement shall be removed by shoveling or street 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, the construction of a small sump shall be considered. The sediment would then be washed into the sump where it can be controlled. • Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. • If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see BMPs C103 and C104) shall be installed to control traffic. • Upon project completion and site stabilization, all construction accesses intended as permanent access for maintenance shall be permanently stabilized. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 12 BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well- established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch with straw or an erosion control blanket until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. • Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydro seeding. See BMP C121: Mulching for specifications. • Seed and mulch, all disturbed areas not otherwise vegetated at final site stabilization. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. Design and Installation Specifications Seed retention/detention ponds as required. Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be established by seed before water flow; install sod in the channel bottom—over hydromulch and erosion control blankets. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 13 • Confirm the installation of all required surface water control measures to prevent seed from washing away. • Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 percent tackifier. See BMP C121: Mulching for specifications. • Areas that will have seeding only and not landscaping may need compost or meal-based mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on the disturbed soil surface before application. • When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent. • Enhance vegetation establishment by dividing the hydromulch operation into two phases: 1. Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. 2. Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: 1. Installing the mulch, seed, fertilizer, and tackifier in one lift. 2. Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. 3. Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: • Irrigation. • Reapplication of mulch. • Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum). • Seed may be installed by hand if: ________________________________________________________________________ December 2018 Stormwater Site Plan Report 14 • Temporary and covered by straw, mulch, or topsoil. • Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets. • The seed mixes listed in the tables below include recommended mixes for both temporary and permanent seeding. • Apply these mixes, with the exception of the wetland mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. • Consult the local suppliers or the local conservation district for their recommendations because the appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the local authority may be used. • Other mixes may be appropriate, depending on the soil type and hydrology of the area. • Table 4.1.2 lists the standard mix for areas requiring a temporary vegetative cover. • Table 4.1.3 lists a recommended mix for landscaping seed. Table 4.1.3 Landscaping Seed Mix % Weight % Purity % Germination Perennial rye blend Lolium perenne 70 98 90 Table 4.1.2 Temporary Erosion Control Seed Mix % Weight % Purity % Germination Chewings or annual blue grass Festuca rubra var. commutata or Poa anna 40 98 90 Perennial rye - Lolium perenne 50 98 90 Redtop or colonial bentgrass Agrostis alba or Agrostis tenuis 5 92 85 White dutch clover Trifolium repens 5 98 90 ________________________________________________________________________ December 2018 Stormwater Site Plan Report 15 Chewings and red fescue blend Festuca rubra var. commutata or Festuca rubra 30 98 90 • Table 4.1.4 lists a turf seed mix for dry situations where there is no need for watering. This mix requires very little maintenance. Table 4.1.4 Low-Growing Turf Seed Mix % Weight % Purity % Germination Dwarf tall fescue (several varieties) Festuca arundinacea var. 45 98 90 Dwarf perennial rye (Barclay) Lolium perenne var. barclay 30 98 90 Red fescue Festuca rubra 20 98 90 Colonial bentgrass Agrostis tenuis 5 98 90 • Table 4.1.5 lists a mix for bioswales and other intermittently wet areas. Table 4.1.5 Bioswale Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca elatior 75-80 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or Agrostis gigantea 5-10 90 80 * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix ________________________________________________________________________ December 2018 Stormwater Site Plan Report 16 • Table 4.1.6 lists a low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wetlands. Apply this mixture at a rate of 60 pounds per acre. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Table 4.1.6 Wet Area Seed Mix* % Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca elatior 60-70 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus pratensis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 * Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix • Table 4.1.7 lists a recommended meadow seed mix for infrequently maintained areas or non-maintained areas 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. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover. Table 4.1.7 Meadow Seed Mix % Weight % Purity % Germination Redtop or Oregon bentgrass Agrostis alba or Agrostis oregonensis 20 92 85 ________________________________________________________________________ December 2018 Stormwater Site Plan Report 17 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 ________________________________________________________________________ December 2018 Stormwater Site Plan Report 18 • Roughening and Rototilling: • The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk slopes before seeding if engineering purposes require compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded. • Restoration-based landscape practices require deeper incorporation than that provided by a simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, permanent areas shall use soil amendments to achieve organic matter and permeability performance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth. • Fertilizers: • Conducting soil tests to determine the exact type and quantity of fertilizer is recommended. This will prevent the over- application of fertilizer. • Organic matter is the most appropriate form of fertilizer because it provides nutrients (including nitrogen, phosphorus, and potassium) in the least water-soluble form. • In general, use 10-4-6 N-P-K (nitrogen-phosphorus- potassium) fertilizer at a rate of 90 pounds per acre. Always use slow-release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agitate, more than 20 minutes before use. Too much agitation destroys the slow-release coating. • There are numerous products available that take the place of chemical fertilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow- release, available nitrogen. • Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix: • On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre of mulch with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numerous products are available commercially. Installed ________________________________________________________________________ December 2018 Stormwater Site Plan Report 19 products per manufacturer’s instructions. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. • BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation establishment. Advantages over blankets include: • BFM and MBFMs do not require surface preparation. • Helicopters can assist in installing BFM and MBFMs in remote areas. • On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses for safety. • Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets. Maintenanc e Standards Reseed any seeded areas that fail to establish at least 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, or nets/blankets. 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. • Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area. • Supply seeded areas with adequate moisture, but do not water to the extent that it causes runoff. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C120. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.h tml. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 20 BMP C130: Surface Roughening Purpose Surface roughening aids in the establishment of vegetative cover, reduces runoff velocity, increases infiltration, and provides for sediment trapping through the provision of a rough soil surface. Horizontal depressions are created by operating a tiller or other suitable equipment on the contour or by leaving slopes in a roughened condition by not fine grading them. Conditions for Use • All slopes steeper than 3:1 and greater than 5 vertical feet require surface roughening. • Areas with grades steeper than 3:1 should be roughened to a depth of 2 to 4 inches prior to seeding. • Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding takes place. • Slopes with a stable rock face do not require roughening. • Slopes where mowing is planned should not be excessively roughened. Design and Installation Specifications There are different methods for achieving a roughened soil surface on a slope, and the selection of an appropriate method depends upon the type of slope. Roughening methods include stair-step grading, grooving, contour furrows, and tracking. See Figure 4.6 for tracking and contour furrows. Factors to be considered in choosing a method are slope steepness, mowing requirements, and whether the slope is formed by cutting or filling. • Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough after filling. • Stair-step grading is particularly appropriate in soils containing large amounts of soft rock. Each "step" catches material that sloughs from above, and provides a level site where vegetation can become established. Stairs should be wide enough to work with standard earth moving equipment. Stair steps must be on contour or gullies will form on the slope. • Areas that will be mowed (these areas should have slopes less steep than 3:1) may have small furrows left by disking, harrowing, raking, or seed-planting machinery operated on the contour. • Graded areas with slopes greater than 3:1 but less than 2:1 should be roughened before seeding. This can be accomplished in a variety of ways, including "track walking," or driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. • Tracking is done by operating equipment up and down the slope to leave horizontal depressions in the soil. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 21 Maintenance Standards • Areas that are graded in this manner should be seeded as quickly as possible. • Regular inspections should be made of the area. If rills appear, they should be re-graded and re-seeded immediately. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 22 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use • In areas (including roadways) subject to surface and air movement of dust where on-site and off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications • Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching, or paving is impractical, apply gravel or landscaping rock. • Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition, if stable. Maintain the original ground cover as long as practical. • Construct natural or artificial windbreaks or windscreens. These may be designed as enclosures for small dust sources. • Sprinkle the site with water until surface is wet. Repeat as needed. To prevent carryout of mud onto street, refer to Stabilized Construction Entrance (BMP C105). • Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. • Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust suppressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. • PAM (BMP C126) added to water at a rate of 0.5 lbs. per 1,000 gallons of water per acre and applied from a water truck is more effective than water alone. This is due to the increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily transported by wind. Adding PAM may actually reduce the quantity of water needed for dust control, especially in eastern Washington. Since the wholesale cost of PAM is about $ 4.00 per pound, this is an extremely cost-effective dust control method. Techniques that can be used for unpaved roads and lots include: • Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. ________________________________________________________________________ December 2018 Stormwater Site Plan Report 23 • Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. • Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. • Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction. • Encourage the use of alternate, paved routes, if available. • Restrict use by tracked vehicles and heavy trucks to prevent damage to road surface and base. • Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. • Pave unpaved permanent roads and other trafficked areas. • Use vacuum street sweepers. • Remove mud and other dirt promptly so it does not dry and then turn into dust. • Limit dust-causing work on windy days. • Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP. Maintenance Standards Respray area as necessary to keep dust to a minimum. ____________________________________________________ 18025 Drainage Report 7-24 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use • In areas (including roadways) subject to surface and air movement of dust where on-site and off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications • Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching, or paving is impractical, apply gravel or landscaping rock. • Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition, if stable. Maintain the original ground cover as long as practical. • Construct natural or artificial windbreaks or windscreens. These may be designed as enclosures for small dust sources. • Sprinkle the site with water until surface is wet. Repeat as needed. To prevent carryout of mud onto street, refer to Stabilized Construction Entrance (BMP C105). • Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. • Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust suppressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. • PAM (BMP C126) added to water at a rate of 0.5 lbs. per 1,000 gallons of water per acre and applied from a water truck is more effective than water alone. This is due to the increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily transported by wind. Adding PAM may actually reduce the quantity of water needed for dust control, especially in eastern Washington. Since the wholesale cost of PAM is about $ 4.00 per pound, this is an extremely cost- effective dust control method. Techniques that can be used for unpaved roads and lots include: • Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. • Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. ____________________________________________________ 18025 Drainage Report 7-25 • Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. • Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction. • Encourage the use of alternate, paved routes, if available. • Restrict use by tracked vehicles and heavy trucks to prevent damage to road surface and base. • Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. • Pave unpaved permanent roads and other trafficked areas. • Use vacuum street sweepers. • Remove mud and other dirt promptly so it does not dry and then turn into dust. • Limit dust-causing work on windy days. • Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP. Maintenance Standards Respray area as necessary to keep dust to a minimum. ____________________________________________________ 18025 Drainage Report 7-26 BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. This BMP is intended to minimize and eliminate concrete process water and slurry from entering waters of the state. Conditions of Use Any time concrete is used, these management practices shall be utilized. Concrete construction projects include, but are not limited to, the following: • Curbs • Sidewalks • Roads • Bridges • Foundations • Floors • Runways Design and Installation Specifications • Concrete truck chutes, pumps, and internals shall be washed out only into formed areas awaiting installation of concrete or asphalt. • Unused concrete remaining in the truck and pump shall be returned to the originating batch plant for recycling. • Hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels shall be washed off only into formed areas awaiting installation of concrete or asphalt. • Equipment that cannot be easily moved, such as concrete pavers, shall only be washed in areas that do not directly drain to natural or constructed stormwater conveyances. • Washdown from areas such as concrete aggregate driveways shall not drain directly to natural or constructed stormwater conveyances. • When no formed areas are available, washwater and leftover product shall be contained in a lined container. Contained concrete shall be disposed of in a manner that does not violate groundwater or surface water quality standards. Maintenance Standards Containers shall be checked for holes in the liner daily during concrete pours and repaired the same day. ____________________________________________________ 18025 Drainage Report 7-27 BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. This BMP is intended to minimize and eliminate process water and slurry from entering waters of the State. Conditions of Use Anytime sawcutting or surfacing operations take place, these management practices shall be utilized. Sawcutting and surfacing operations include, but are not limited to, the following: • Sawing • Coring • Grinding • Roughening • Hydro-demolition • Bridge and road surfacing Design and Installation Specifications • Slurry and cuttings shall be vacuumed during cutting and surfacing operations. • Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. • Slurry and cuttings shall not drain to any natural or constructed drainage conveyance. • Collected slurry and cuttings shall be disposed of in a manner that does not violate groundwater or surface water quality standards. • Process water that is generated during hydro-demolition, surface roughening or similar operations shall not drain to any natural or constructed drainage conveyance and shall be disposed of in a manner that does not violate groundwater or surface water quality standards. • Cleaning waste material and demolition debris shall be handled and disposed of in a manner that does not cause contamination of water. If the area is swept with a pick-up sweeper, the material must be hauled out of the area to an appropriate disposal site. ____________________________________________________ 18025 Drainage Report 7-28 Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum trucks. ____________________________________________________ 18025 Drainage Report 7-29 BMP C220: Storm Drain Inlet Protection Purpose To prevent coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area. Conditions of Use Where storm drain inlets are to be made operational before permanent stabilization of the disturbed drainage area. Protection should 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. Inlet protection may be used anywhere to protect the drainage system. It is likely that the drainage system will still require cleaning. Table 4.9 lists several options for inlet protection. All of the methods for storm drain inlet protection are prone to plugging and require a high frequency of maintenance. Drainage areas should be limited to 1 acre or less. Emergency overflows may be required where stormwater ponding would cause a hazard. If an emergency overflow is provided, additional end-of-pipe treatment may be required. Table 4.9 Storm Drain Inlet Protetion Type of Inlet Protection Emergency Overflow Applicable for Paved/ Earthen Surfaces Conditions of Use Drop Inlet Protection Excavated drop inlet protection Yes, temporary flooding will occur Earthen Applicable for heavy flows. Easy to maintain. Large area Requirement: 30’ X 30’/acre Block and gravel drop inlet protection Yes Paved or Earthen Applicable for heavy concentrated flows. Will not pond. Gravel and wire drop inlet protection No Applicable for heavy concentrated flows. Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet protection with a wooden weir Small capacity overflow Paved Used for sturdy, more compact installation. Block and gravel curb inlet protection Yes Paved Sturdy, but limited filtration. Culvert Inlet Protection Culvert inlet sediment trap 18 month expected life. ____________________________________________________ 18025 Drainage Report 7-30 Design and Installation Specifications Excavated Drop Inlet Protection - An excavated impoundment around the storm drain. Sediment settles out of the stormwater prior to entering the storm drain. • Depth 1-2 ft as measured from the crest of the inlet structure. • Side Slopes of excavation no steeper than 2:1. • Minimum volume of excavation 35 cubic yards. • Shape basin to fit site with longest dimension oriented toward the longest inflow area. • Install provisions for draining to prevent standing water problems. • Clear the area of all debris. • Grade the approach to the inlet uniformly. • Drill weep holes into the side of the inlet. • Protect weep holes with screen wire and washed aggregate. • Seal weep holes when removing structure and stabilizing area. • It may be necessary to build a temporary dike to the down slope side of the structure to prevent bypass flow. Block and Gravel Filter - A barrier formed around the storm drain inlet with standard concrete blocks and gravel. See Figure 4.14. • Height 1 to 2 feet above inlet. • Recess the first row 2 inches into the ground for stability. • Support subsequent courses by placing a 2x4 through the block opening. • Do not use mortar. • Lay some blocks in the bottom row on their side for dewatering the pool. • Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings. • Place gravel just below the top of blocks on slopes of 2:1 or flatter. • An alternative design is a gravel donut. • Inlet slope of 3:1. • Outlet slope of 2:1. • 1-foot wide level stone area between the structure and the inlet. • Inlet slope stones 3 inches in diameter or larger. • Outlet slope use gravel ½- to ¾-inch at a minimum thickness of 1-foot. ____________________________________________________ 18025 Drainage Report 7-31 Figure 4.14 – Block and Gravel Filter Gravel and Wire Mesh Filter - A gravel barrier placed over the top of the inlet. This structure does not provide an overflow. • Hardware cloth or comparable wire mesh with ½-inch openings. • Coarse aggregate. • Height 1-foot or more, 18 inches wider than inlet on all sides. • Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure. • If more than one strip of mesh is necessary, overlap the strips. • Place coarse aggregate over the wire mesh. • The depth of the gravel should be at least 12 inches over the entire inlet opening and extend at least 18 inches on all sides. ____________________________________________________ 18025 Drainage Report 7-32 Catchbasin Filters - Inserts should be designed by the manufacturer for use at construction sites. The limited sediment storage capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. The maintenance requirements can be reduced by combining a catchbasin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way. • 5 cubic feet of storage. • Dewatering provisions. • High-flow bypass that will not clog under normal use at a construction site. • The catchbasin filter is inserted in the catchbasin just below the grating. Curb Inlet Protection with Wooden Weir – Barrier formed around a curb inlet with a wooden frame and gravel. • Wire mesh with ½-inch openings. • Extra strength filter cloth. • Construct a frame. • Attach the wire and filter fabric to the frame. • Pile coarse washed aggregate against wire/fabric. • Place weight on frame anchors. Block and Gravel Curb Inlet Protection – Barrier formed around an inlet with concrete blocks and gravel. See Figure 4.14. • Wire mesh with ½-inch openings. • Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. • Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. • Place blocks on their sides across the front of the inlet and abutting the spacer blocks. • Place wire mesh over the outside vertical face. • Pile coarse aggregate against the wire to the top of the barrier. Curb and Gutter Sediment Barrier – Sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure 4.16. • Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. ____________________________________________________ 18025 Drainage Report 7-33 • Construct a horseshoe shaped sedimentation trap on the outside of the berm sized to sediment trap standards for protecting a culvert inlet. Maintenance Standards • Catch basin filters should be inspected frequently, especially after storm events. If the insert becomes clogged, it should be cleaned or replaced. • For systems using stone filters: If the stone filter becomes clogged with sediment, the stones must be pulled away from the inlet and cleaned or replaced. Since cleaning of gravel at a construction site may be difficult, an alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. • Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. ____________________________________________________ 18025 Drainage Report 7-34 Figure 4.15 – Block and Gravel Curb Inlet Protection A Plan View Wire Screen or Filter Fabric Catch Basin Curb Inlet Concrete Block Ponding Height Overflow 2x4 Wood Stud (100x50 Timber Stud) Concrete Block Wire Screen or Filter Fabric Curb Inlet ¾" Drain Gravel (20mm) ¾" Drain Gravel (20mm)Section A - A Back of Curb Concrete Block 2x4 Wood Stud Catch BasinBack of Sidewalk NOTES: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. ____________________________________________________ 18025 Drainage Report 7-35 Figure 4.16 – Curb and Gutter Barrier ____________________________________________________ 18025 Drainage Report 7-36 BMP C235: Straw Wattles Purpose Straw wattles are temporary erosion and sediment control barriers consisting of straw that is wrapped in biodegradable tubular plastic or similar encasing material. They 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. See Figure 4.21 for typical construction details. Conditions of Use • Disturbed areas that require immediate erosion protection. • Exposed soils during the period of short construction delays, or over winter months. • On slopes requiring stabilization until permanent vegetation can be established. • Straw wattles are effective for one to two seasons. • If conditions are appropriate, wattles can be staked to the ground using willow cuttings for added revegetation. • Rilling can occur beneath wattles if not properly entrenched and water can pass between wattles if not tightly abutted together. Design Criteria • It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope contour. • 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 areas with high rainfall, the trenches should be dug to a depth of 5 to 7 inches, or 1/2 to 2/3 of the thickness of the wattle. • Start building trenches and installing wattles from the base of the slope and work up. Excavated material should be spread evenly along the uphill slope and compacted using hand tamping or other methods. • 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. • Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. • Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. • If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. ____________________________________________________ 18025 Drainage Report 7-37 • At a minimum, wooden stakes should be approximately 3/4 x 3/4 x 24 inches. Willow cuttings or 3/8-inch rebar can also be used for stakes. Maintenance Standards • Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake protruding above the wattle. • Wattles may require maintenance to ensure they are in contact with soil and thoroughly entrenched, especially after significant rainfall on steep sandy soils. ____________________________________________________ 18025 Drainage Report 7-38 • Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. • Figure 4.21 – Straw Wattles ____________________________________________________ 18025 Drainage Report 8-1 PART 8 – SPECIAL REPORTS AND STUDIES 1. Soils Report – Parnell Engineering, LLC – See Appendix 2 of this document. ____________________________________________________ 18025 Drainage Report 9-1 PART 9 – OTHER PERMITS The following is a list of regulatory permits needed for this project and copies are attached if available. SEPA Review – Pending Determination Grading and Drainage – Pending Final Drainage and Grading Plans Building Permits – Pending Design and Permitting ____________________________________________________ 18025 Drainage Report 10-1 PART 10 – OPERATION AND MAINTENANCE MANUAL A final Operation and Maintenance Manual has been prepared as a separate document. ____________________________________________________ 18025 Drainage Report 11-1 PART 11 – BOND QUANTITIES/FINANCIAL RESPONSIBILITY Facility agreements and financial guarantees when required will be reviewed by the applicant and executed at the appropriate time determined by the reviewing agency. ____________________________________________________ 18025 Drainage Report 12-1 PART 12 – GRADING AND DRAINAGE PLANS The half size drawing of the site civil grading and drainage plans are included on the following pages. DESIGN PERMIT MANAGEEngineeringNPR RECYCLINGILTRLEMLABW.EBORAPPROVAL EXPIRES:APPROVED FOR CONSTRUCTIONBY:DATE:C3.1GRADING AND DRAINAGE PLANNORTHERN PACIFIC RD NW1 C3.3 2C3.3 SEE SHEET C3.2C3.35C3.48C3.48C3.51C3.35C3.35C3.47GRAVEL YARD STORAGE AREA -STRIP TOP 4" SOD AND FINE GRADE.ADD 6" OF CSBC COMPACTED TO 95%. DESIGN PERMIT MANAGEEngineeringNPR RECYCLINGILTRLEMLABW.EBORAPPROVAL EXPIRES:APPROVED FOR CONSTRUCTIONBY:DATE:C3.2YARD GRADINGAND DRAINAGE PLAN4 C3.3 3 C3.3 SEE SHEET C3.13C3.41C3.44C3.46C3.36C3.3GRAVEL YARD STORAGE AREA -STRIP TOP 4" SOD AND FINE GRADE.ADD 6" OF CSBC COMPACTED TO 95%.2C3.46C3.45C3.35C3.35C3.35C3.35C3.35C3.35C3.36C3.46C3.47C3.4 APPENDIX #1 Basin Map BMP Calculations Overflow Calculations Conveyance Calculations DESIGN PERMIT MANAGE Engineering NPR RECYCLING ILTRLEMLABW.E BOR BASINBASIN MAP NORTHERN PACIFIC ROAD SE ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 201610012 Project Simulation Performed on: 12/14/2018 10:10 AM Report Generation Date: 12/14/2018 11:04 AM ————————————————————————————————— Input File Name: BASIN #1.fld Project Name: NPR RECYCLING Analysis Title: BIORETENTION AND INFILTRATION TRENCH Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.336 0.333 Area of Links that Include Precip/Evap (acres) 0.000 0.003 Total (acres) 0.336 0.336 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Forest 0.336 ---------------------------------------------- Subbasin Total 0.336 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Pasture 0.123 Impervious 0.210 ---------------------------------------------- Subbasin Total 0.333 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: BASIN #1 BIORETENTION Link Type: Bioretention Facility Downstream Link Name: BASIN #1 INFILTRATION TRENCH Base Elevation (ft) : 335.20 Riser Crest Elevation (ft) : 336.20 Storage Depth (ft) : 1.00 Bottom Length (ft) : 39.0 Bottom Width (ft) : 3.0 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 117 Area at Riser Crest El (sq-ft) : 405 (acres) : 0.009 Volume at Riser Crest (cu-ft) : 325. (ac-ft) : 0.007 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 3.00 Biosoil Porosity (Percent) : 40.00 Maximum Elevation of Bioretention Soil : 337.00 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 8.00 Common Length (ft) : 0.000 Riser Crest Elevation : 336.20 ft Hydraulic Structure Geometry Number of Devices: 0 ------------------------------------------ Link Name: BASIN #1 INFILTRATION TRENCH Link Type: Infiltration Trench Downstream Link: None Trench Type : Trench on Embankment Sideslope Trench Length (ft) : 28.00 Trench Width (ft) : 4.00 Trench Depth (ft) : 3.00 Trench Bottom Elev (ft) : 331.45 Trench Rockfill Porosity (%) : 40.00 Constant Infiltration Option Used Infiltration Rate (in/hr): 20.00 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Subbasin: Subbasin 1 ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 8.153E-02 5-Year 0.107 10-Year 0.127 25-Year 0.150 50-Year 0.181 100-Year 0.222 200-Year 0.232 ********** Link: BASIN #1 BIORETENTION ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 8.153E-02 5-Year 0.107 10-Year 0.127 25-Year 0.150 50-Year 0.181 100-Year 0.222 200-Year 0.232 ********** Link: BASIN #1 BIORETENTION ********** Link Outflow 1 Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 6.264E-02 5-Year 8.592E-02 10-Year 0.102 25-Year 0.116 50-Year 0.141 100-Year 0.160 200-Year 0.188 ********** Link: BASIN #1 BIORETENTION ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 336.224 1.11-Year 336.227 1.25-Year 336.231 2.00-Year 336.243 3.33-Year 336.248 5-Year 336.253 10-Year 336.259 25-Year 336.265 50-Year 336.274 100-Year 336.280 ********** Link: BASIN #1 INFILTRATION TRENCH ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 6.264E-02 5-Year 8.592E-02 10-Year 0.102 25-Year 0.116 50-Year 0.141 100-Year 0.160 200-Year 0.188 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 105.069 _____________________________________ Total: 105.069 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 47.629 Link: BASIN #1 BIORETENTIO 98.486 Link: BASIN #1 INFILTRATIO 9.043 _____________________________________ Total: 155.158 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.665 ac-ft/year, Post Developed: 0.982 ac -ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: BASIN #1 BIORETENTION ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 105.48 Inflow Volume Including PPT-Evap (ac-ft): 107.66 Total Runoff Infiltrated (ac-ft): 98.49, 91.48% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 9.04 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 91.48% ********** Link: BASIN #1 INFILTRATION TRENCH ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 9.04 Inflow Volume Including PPT-Evap (ac-ft): 9.04 Total Runoff Infiltrated (ac-ft): 9.04, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: BASIN #1 INFILTRATION TRENCH *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.606E-04 2-Year 0.000 5-Year 2.687E-04 5-Year 0.000 10-Year 2.707E-04 10-Year 0.000 25-Year 1.017E-03 25-Year 0.000 50-Year 1.272E-03 50-Year 0.000 100-Year 1.843E-03 100-Year 0.000 200-Year 2.769E-03 200-Year 0.000 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 201610012 Project Simulation Performed on: 12/14/2018 10:53 AM Report Generation Date: 12/14/2018 10:54 AM ————————————————————————————————— Input File Name: BASIN #2.fld Project Name: NPR RECYCLING Analysis Title: BIORETENTION AND INFILTRATION CELL Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 6.766 6.670 Area of Links that Include Precip/Evap (acres) 0.000 0.096 Total (acres) 6.766 6.766 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Forest 6.766 ---------------------------------------------- Subbasin Total 6.766 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Grass 0.185 Impervious 6.485 ---------------------------------------------- Subbasin Total 6.670 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: BASIN #2 BIORETENTION Link Type: Bioretention Facility Downstream Link Name: BASIN #2 INFILTRATION CELL Base Elevation (ft) : 330.00 Riser Crest Elevation (ft) : 331.00 Storage Depth (ft) : 1.00 Bottom Length (ft) : 520.0 Bottom Width (ft) : 8.0 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 4160. Area at Riser Crest El (sq-ft) : 7,364. (acres) : 0.169 Volume at Riser Crest (cu-ft) : 8,252. (ac-ft) : 0.189 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 3.00 Biosoil Porosity (Percent) : 40.00 Maximum Elevation of Bioretention Soil : 332.00 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 0.000 Riser Crest Elevation : 331.00 ft Hydraulic Structure Geometry Number of Devices: 0 ------------------------------------------ Link Name: BASIN #2 INFILTRATION CELL Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 328.00 Riser Crest Elevation (ft) : 331.00 Max Pond Elevation (ft) : 333.00 Storage Depth (ft) : 3.00 Pond Bottom Length (ft) : 532.0 Pond Bottom Width (ft) : 4.6 Pond Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 2447. Area at Riser Crest El (sq-ft) : 12,430. (acres) : 0.285 Volume at Riser Crest (cu-ft) : 22,153. (ac-ft) : 0.509 Area at Max Elevation (sq-ft) : 19445. (acres) : 0.446 Vol at Max Elevation (cu-ft) : 53,978. (ac-ft) : 1.239 Constant Infiltration Option Used Infiltration Rate (in/hr): 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 0.000 Riser Crest Elevation : 331.00 ft Hydraulic Structure Geometry Number of Devices: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Subbasin: Subbasin 1 ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.518 5-Year 3.294 10-Year 3.831 25-Year 4.619 50-Year 5.595 100-Year 6.854 200-Year 7.169 ********** Link: BASIN #2 BIORETENTION ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.518 5-Year 3.294 10-Year 3.831 25-Year 4.619 50-Year 5.595 100-Year 6.854 200-Year 7.169 ********** Link: BASIN #2 BIORETENTION ********** Link Outflow 1 Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.834 5-Year 2.476 10-Year 2.912 25-Year 3.316 50-Year 4.259 100-Year 4.680 200-Year 5.501 ********** Link: BASIN #2 BIORETENTION ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 331.116 1.11-Year 331.130 1.25-Year 331.146 2.00-Year 331.195 3.33-Year 331.224 5-Year 331.239 10-Year 331.268 25-Year 331.293 50-Year 331.350 100-Year 331.374 ********** Link: BASIN #2 INFILTRATION CELL ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.834 5-Year 2.476 10-Year 2.912 25-Year 3.316 50-Year 4.259 100-Year 4.680 200-Year 5.501 ********** Link: BASIN #2 INFILTRATION CELL ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 328.014 1.11-Year 328.017 1.25-Year 328.020 2.00-Year 328.268 3.33-Year 328.420 5-Year 328.511 10-Year 328.646 25-Year 328.923 50-Year 329.013 100-Year 329.244 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 2115.767 _____________________________________ Total: 2115.767 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 70.555 Link: BASIN #2 BIORETENTIO 3018.675 Link: BASIN #2 INFILTRATIO 291.377 _____________________________________ Total: 3380.607 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 13.391 ac-ft/year, Post Developed: 21.396 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: BASIN #2 BIORETENTION ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 3255.55 Inflow Volume Including PPT-Evap (ac-ft): 3310.78 Total Runoff Infiltrated (ac-ft): 3018.68, 91.18% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 291.38 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 91.18% ********** Link: BASIN #2 INFILTRATION CELL ********** Basic Wet Pond Volume (91% Exceedance): 32403. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 48604. cu-ft Time to Infiltrate 91% Treatment Volume, (Hours): 2.28 Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 291.38 Inflow Volume Including PPT-Evap (ac-ft): 291.38 Total Runoff Infiltrated (ac-ft): 291.38, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: BASIN #2 INFILTRATION CELL *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 5.247E-03 2-Year 0.000 5-Year 5.412E-03 5-Year 0.000 10-Year 5.451E-03 10-Year 0.000 25-Year 2.048E-02 25-Year 0.000 50-Year 2.562E-02 50-Year 0.000 100-Year 3.712E-02 100-Year 0.000 200-Year 5.575E-02 200-Year 0.000 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 201610012 Project Simulation Performed on: 12/14/2018 11:37 AM Report Generation Date: 12/14/2018 11:37 AM ————————————————————————————————— Input File Name: BASIN #3.fld Project Name: NPR RECYCLING Analysis Title: BASIN #3 BIORETENTION AND INFILTRATION CELL Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 5.530 5.450 Area of Links that Include Precip/Evap (acres) 0.000 0.079 Total (acres) 5.530 5.529 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Forest 5.530 ---------------------------------------------- Subbasin Total 5.530 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Pasture 0.022 Impervious 5.428 ---------------------------------------------- Subbasin Total 5.450 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: BASIN #3 BIORETENTION Link Type: Bioretention Facility Downstream Link Name: BASIN #3 INFILTRATION CELL Base Elevation (ft) : 329.50 Riser Crest Elevation (ft) : 330.50 Storage Depth (ft) : 1.00 Bottom Length (ft) : 531.0 (The length of the cell is 540, but inlet protection areas were removed for a conservative calculation) Bottom Width (ft) : 6.5 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 3452. Area at Riser Crest El (sq-ft) : 6,713. (acres) : 0.154 Volume at Riser Crest (cu-ft) : 7,147. (ac-ft) : 0.164 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 3.00 Biosoil Porosity (Percent) : 40.00 Maximum Elevation of Bioretention Soil : 331.50 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 0.000 Riser Crest Elevation : 330.50 ft Hydraulic Structure Geometry Number of Devices: 0 ------------------------------------------ Link Name: BASIN #3 INFILTRATION CELL Link Type: Structure Downstream Link: None Prismatic Pond Option Used Pond Floor Elevation (ft) : 327.50 Riser Crest Elevation (ft) : 330.50 Max Pond Elevation (ft) : 331.50 Storage Depth (ft) : 3.00 Pond Bottom Length (ft) : 500.0 Pond Bottom Width (ft) : 3.9 Pond Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 1950. Area at Riser Crest El (sq-ft) : 11,344. (acres) : 0.260 Volume at Riser Crest (cu-ft) : 19,779. (ac-ft) : 0.454 Area at Max Elevation (sq-ft) : 14620. (acres) : 0.336 Vol at Max Elevation (cu-ft) : 32,754. (ac-ft) : 0.752 Constant Infiltration Option Used Infiltration Rate (in/hr): 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 24.00 Common Length (ft) : 0.000 Riser Crest Elevation : 330.50 ft Hydraulic Structure Geometry Number of Devices: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Subbasin: Subbasin 1 ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.107 5-Year 2.757 10-Year 3.207 25-Year 3.863 50-Year 4.683 100-Year 5.737 200-Year 6.001 ********** Link: BASIN #3 BIORETENTION ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 2.107 5-Year 2.757 10-Year 3.207 25-Year 3.863 50-Year 4.683 100-Year 5.737 200-Year 6.001 ********** Link: BASIN #3 BIORETENTION ********** Link Outflow 1 Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.549 5-Year 2.081 10-Year 2.453 25-Year 2.805 50-Year 3.484 100-Year 3.958 200-Year 4.661 ********** Link: BASIN #3 BIORETENTION ********** L ink WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 330.603 1.11-Year 330.614 1.25-Year 330.630 2.00-Year 330.674 3.33-Year 330.698 5-Year 330.713 10-Year 330.738 25-Year 330.761 50-Year 330.803 100-Year 330.832 ********** Link: BASIN #3 INFILTRATION CELL ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 1.549 5-Year 2.081 10-Year 2.453 25-Year 2.805 50-Year 3.484 100-Year 3.958 200-Year 4.661 ********** Link: BASIN #3 INFILTRATION CELL ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 327.513 1.11-Year 327.515 1.25-Year 327.529 2.00-Year 327.781 3.33-Year 327.920 5-Year 327.999 10-Year 328.130 25-Year 328.375 50-Year 328.451 100-Year 328.681 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 1729.263 _____________________________________ Total: 1729.263 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 8.519 Link: BASIN #3 BIORETENTIO 2534.927 Link: BASIN #3 INFILTRATIO 236.765 _____________________________________ Total: 2780.210 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 10.945 ac-ft/year, Post Developed: 17.596 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: BASIN #3 BIORETENTION ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 2724.75 Inflow Volume Including PPT-Evap (ac-ft): 2772.36 Total Runoff Infiltrated (ac-ft): 2534.93, 91.44% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 236.76 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 91.44% ********** Link: BASIN #3 INFILTRATION CELL ********** Basic Wet Pond Volume (91% Exceedance): 27911. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 41867. cu-ft Time to Infiltrate 91% Treatment Volume, (Hours): 2.22 Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 236.76 Inflow Volume Including PPT-Evap (ac-ft): 236.76 Total Runoff Infiltrated (ac-ft): 236.76, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: BASIN #3 INFILTRATION CELL *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 4.289E-03 2-Year 0.000 5-Year 4.423E-03 5-Year 0.000 10-Year 4.455E-03 10-Year 0.000 25-Year 1.674E-02 25-Year 0.000 50-Year 2.094E-02 50-Year 0.000 100-Year 3.034E-02 100-Year 0.000 200-Year 4.557E-02 200-Year 0.000 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.46 Program License Number: 201610012 Project Simulation Performed on: 12/14/2018 11:59 AM Report Generation Date: 12/14/2018 12:00 PM ————————————————————————————————— Input File Name: BASIN #4.fld Project Name: NPR RECYCLING Analysis Title: BASIN #4 BIORETENTION AND INFILTRATION TRENCH Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.589 0.586 Area of Links that Include Precip/Evap (acres) 0.000 0.002 Total (acres) 0.589 0.588 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Forest 0.589 ---------------------------------------------- Subbasin Total 0.589 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Outwash Pasture 0.401 Impervious 0.185 ---------------------------------------------- Subbasin Total 0.586 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: BASIN #4 BIORETENTION Link Type: Bioretention Facility Downstream Link Name: BASIN #4 INFILTRATION TRENCH Base Elevation (ft) : 332.50 Riser Crest Elevation (ft) : 333.50 Storage Depth (ft) : 1.00 Bottom Length (ft) : 27.0 Bottom Width (ft) : 4.0 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 108. Area at Riser Crest El (sq-ft) : 330. (acres) : 0.008 Volume at Riser Crest (cu-ft) : 278. (ac-ft) : 0.006 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 3.00 Biosoil Porosity (Percent) : 40.00 Maximum Elevation of Bioretention Soil : 334.50 Native Soil Hydraulic Conductivity (in/hr) : 20.00 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 8.00 Common Length (ft) : 0.000 Riser Crest Elevation : 333.50 ft Hydraulic Structure Geometry Number of Devices: 0 ------------------------------------------ Link Name: BASIN #4 INFILTRATION TRENCH Link Type: Infiltration Trench Downstream Link: None Trench Type : Trench on Embankment Sideslope Trench Length (ft) : 26.00 Trench Width (ft) : 4.00 Trench Depth (ft) : 3.00 Trench Bottom Elev (ft) : 329.75 Trench Rockfill Porosity (%) : 40.00 Constant Infiltration Option Used Infiltration Rate (in/hr): 20.00 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ********** Subbasin: Subbasin 1 ********** Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 7.211E-02 5-Year 9.449E-02 10-Year 0.112 25-Year 0.139 50-Year 0.160 100-Year 0.196 200-Year 0.205 ********** Link: BASIN #4 BIORETENTION ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 7.211E-02 5-Year 9.449E-02 10-Year 0.112 25-Year 0.139 50-Year 0.160 100-Year 0.196 200-Year 0.205 ********** Link: BASIN #4 BIORETENTION ********** Link Outflow 1 Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 5.568E-02 5-Year 7.580E-02 10-Year 9.163E-02 25-Year 0.101 50-Year 0.137 100-Year 0.145 200-Year 0.177 ********** Link: BASIN #4 BIORETENTION ********** Link WSEL Stats WSEL Frequency Data(ft) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) WSEL Peak (ft) ====================================== 1.05-Year 333.523 1.11-Year 333.525 1.25-Year 333.529 2.00-Year 333.539 3.33-Year 333.544 5-Year 333.548 10-Year 333.555 25-Year 333.559 50-Year 333.572 100-Year 333.575 ********** Link: BASIN #4 INFILTRATION TRENCH ********** Link Inflow Frequency Stats Flood Frequency Data(cfs) (Recurrence Interval Computed Using Gringorten Plotting Position) Tr (yrs) Flood Peak (cfs) ====================================== 2-Year 5.568E-02 5-Year 7.580E-02 10-Year 9.163E-02 25-Year 0.101 50-Year 0.137 100-Year 0.145 200-Year 0.177 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 184.184 _____________________________________ Total: 184.184 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Subbasin 1 155.278 Link: BASIN #4 BIORETENTIO 86.975 Link: BASIN #4 INFILTRATIO 7.854 _____________________________________ Total: 250.106 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.166 ac-ft/year, Post Developed: 1.583 ac -ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: BASIN #4 BIORETENTION ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 93.07 Inflow Volume Including PPT-Evap (ac-ft): 94.92 Total Runoff Infiltrated (ac-ft): 86.97, 91.63% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 7.85 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 91.63% ********** Link: BASIN #4 INFILTRATION TRENCH ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 7.85 Inflow Volume Including PPT-Evap (ac-ft): 7.85 Total Runoff Infiltrated (ac-ft): 7.85, 100.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.00 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Link: BASIN #4 INFILTRATION TRENCH *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 4.568E-04 2-Year 0.000 5-Year 4.711E-04 5-Year 0.000 10-Year 4.745E-04 10-Year 0.000 25-Year 1.783E-03 25-Year 0.000 50-Year 2.230E-03 50-Year 0.000 100-Year 3.231E-03 100-Year 0.000 200-Year 4.854E-03 200-Year 0.000 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS ------------------------------------------------------------------------------------------------- MEETS ALL LID DURATION DESIGN CRITERIA: PASS ------------------------------------------------------------------------------------------------- BASIN Q100 H MIN. L L100 = [Q100/(3.21H3/2)] - 2.4 H EMERGENCY SPILLWAY SIZING Figure 3.2.5 - Weir Section for Emergency Overflow Spillway 0.7 ft. min 0 5 ft i #2 6.854 0.22 20.16 --> DESIGN = 21' #3 5.737 0.20 19.50 --> DESIGN = 21' Q100 = 100-YEAR STORM (CFS) H = OVERFLOW HEIGHT (FT) L = LENGTH OF SPILLWAY (FT) SPILLWAY AND EMERGENCY OVERFLOW DESIGN CONVEYANCE CALCULATIONS BASIN #1 An 8" Diam. Per MGS Flood, the max 100 year flow = 0.16 cfs Circular Diameter (ft) = 0.67 Invert Elev (ft) = 336.50 Slope (%) = 5.07 N-Value = 0.012 Calculations Compute by: Known Q Known Q (cfs) = 0.16 Highlighted Depth (ft) = 0.11 Q (cfs) = 0.160 Area (sqft) = 0.04 Velocity (ft/s) = 4.22 Wetted Perim (ft) = 0.56 Crit Depth, Yc (ft) = 0.19 Top Width (ft) = 0.50 EGL (ft) = 0.39 CONVEYANCE CALCULATIONS CONVEYANCE CALCULATIONS BASIN #4 An 8" Diam. HDPE pipe @ 5.62% is proposed to convey the deferred frontage improvements to the Bioretention cell. Per MGS Flood, the max 100 year flow = 0.15 cfs Circular Diameter (ft) = 0.67 Invert Elev (ft) = 335.31 Slope (%) = 5.62 N-Value = 0.012 Calculations Compute by: Known Q Known Q (cfs) = 0.15 Highlighted Depth (ft) = 0.10 Q (cfs) = 0.150 Area (sqft) = 0.03 Velocity (ft/s) = 4.53 Wetted Perim (ft) = 0.53 Crit Depth, Yc (ft) = 0.18 Top Width (ft) = 0.48 EGL (ft) = 0.42 APPENDIX # 2 SOILS REPORT: Parnell Engineering, LLC