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HomeMy WebLinkAboutRS_Prelim_TIR_250728_v1 PRELIMINARY TECHNICAL INFORMATION REPORT ______________________________________________________________ Vuong Short Plat 12820 156th Avenue SE Renton, WA 98059 Prepared For: GoFeasibility P.O. Box 1176 Sumner, WA 98390 7/5/24 Date: July 5, 2024 ______________________________________________________________ P.O. Box 121, Sumner, WA 98390 (206) 450-5096 www.tebaldiengineering.com TABLE OF CONTENTS 1.0 PROJECT OVERVIEW Figure 1 – Technical Information Report (TIR) Worksheet Figure 2 – Vicinity Map 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Core Requirements 2.2 Analysis of the Special Requirements 3.0 OFF-SITE ANALYSIS Figure 3 – Downstream Map 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology Figure 4 – Soils B. Developed Site Hydrology C. Performance Standards D. Flow Control System E. Water Quality System 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 6.0 SPECIAL REPORTS AND STUDIES 7.0 OTHER PERMITS 8.0 CSWPP ANALYSIS AND DESIGN 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 10.0 OPERATIONS AND MAINTENANCE MANUAL Appendix A - Soil Characterization and Infiltration Letter prepared by Innovative Geoservices dated December 20, 2022 Appendix B - WWHM Calculations 1.0 PROJECT OVERVIEW The project is located in Section 14, Township 23 North, Range 5 East, Willamette Meridian, King County, Washington in the City of Renton at 12820 156th Avenue SE, Renton, WA on tax parcel number 3664500165. More specifically, the project is located at the City of Renton at 12820 156th Avenue SE, Renton, WA on tax parcel number 3664500165. The project proposes subdivide the existing parcels into 3 total lots. An area table has been provided below in this section. The 1.07-acre property is bound by single-family residences to the north, south, and east and 156th Avenue SE to the west. The existing topography varies from approximately 0 to 10 percent and the site generally falls from north to south. The vegetation on the project site consists of existing landscaping and pasture area. In the existing condition, runoff from the project area sheet flows to the southwest to the existing storm system in 156th Avenue SE. Runoff in the developed condition for the on-site portion of the project will be collected and infiltrated on-site via full infiltration. Runoff for the existing and proposed ROW/road areas will be collected and routed to the existing drainage system in 156th Avenue SE. There are no known critical areas on the subject property. Area Summary Pre-Developed Developed Parcel Area 46,576 SF 46,576 SF Project Area (clearing limits) - 24,300 SF Existing Buildings - - Existing Driveway/Walk - - New Pervious - 29,712 SF Proposed On-site Roof/Driveway* - 8,800 SF Offsite Sidewalk - 1,831 SF Offsite Pavement/Driveway (PGIS) - 9,423 SF Total Impervious - 20,054 SF *Assumes 4,400 SF impervious per lot. Ha Vuong 12820 156th Avenue SE Renton, WA 98059 Chris Tebaldi, P.E. Tebaldi Engineering, LLC 206-450-5096 Vuong Short Plat 12820 156th Avenue SE Renton, WA 98059 X X 7/5/24 7/5/24 X Alderwood Finn 1 None 0 X X X X X X X 7/5/24 X X 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Core Requirements Core Requirement No. 1: Discharge at the Natural Location. Response: The existing site currently sheet flows to the south to the existing storm drainage system in 156th Avenue SE. Runoff in the developed condition will be connected to the existing storm system or infiltrated. Core Requirement No. 2: Off-Site Analysis. Response: A downstream analysis has been completed. See section 3.0 of this report. Core Requirement No. 3: Flow Control. Response: The proposed project is subject to the requirements of flood prone flow control for the target surfaces. Based on the allowable exception 2 under core requirement #3, flow control is waived for any threshold discharge area in which there is no more than a 0.15 difference in the sum of peak flows between the proposed 100-year peak and the historic 100-year peak. Therefore, no flow control facility is required and flow durations do not need to be met as a part of flow control analysis. Flow control requirements have been met by not increasing the post-developed flow rate by more than 0.15 cfs utilizing a 15-minute timestep over the pre-developed forested condition in accordance with the 2022 City of Renton Surface Water Design Manual. See section 4.0. Core Requirement No. 4: Conveyance System. Response: The proposed conveyance system will be designed to convey the 100-year design storm. Please refer to Section 5.0 for calculations. Core Requirement No. 5: Construction Stormwater Pollution Prevention. Response: Temporary erosion control measures for this project include stabilized construction entrance, perimeter runoff control; cover practices of the disturbed areas and construction sequence. Core Requirement No. 6: Maintenance and Operations. Response: The drainage facilities for this project will be privately maintained and have been designed in accordance with the 2022 City of Renton Surface Water Design Manual. Core Requirement No. 7: Financial Guarantees and Liability. Response: Any financial guarantees will be posted/secured as required by the City of Renton. Core Requirement No. 8: Water Quality. Response: Water quality treatment is required as the pollution generating impervious surface is more than 5,000 square feet. See section 4.0. Core Requirement No. 9: Flow Control BMPs Response: The proposed project will utilize the list approach to the flow control BMP requirement. See section 4.0 of this report. 2.2 Analysis of the Special Requirements Special Requirement No. 1: Other Adopted Area-Specific Requirements. Response: This special requirement does not apply to this project. Special Requirement No. 2: Flood Hazard Area Delineation. Response: The project is not located in a floodplain or floodway. Special Requirement No. 3: Flood Protection Facilities. Response: This requirement does not apply. Special Requirement No. 4: Source Control. Response: This requirement does not apply. Special Requirement No. 5: Oil Control. Response: This requirement does not apply. 3.0 OFF-SITE ANALYSIS The project site currently sheet flows to the southwest. Runoff from the site currently sheetflows southwest approximately 50 feet discharging into the existing stormwater system in 156th Avenue SE. Runoff then flows south approximately 1500 feet in a series of pipes and catch basins into an existing City of Renton stormwater facility. Runoff leaves the facility and flows south for approximately 3,800 lineal feet prior to discharge into a natural conveyance. The conveyance flows into the Cedar River which ultimately discharges into Lake Washington. See Downstream Map in this section. Downstream Drainage Map SITE Pipe and ditch conveyance system Ex. City Stormwater Facility Pipe and ditch conveyance system 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology The existing project area consists of an existing residence along with the associated driveway, landscaping and trees. On-site soils consist of glacial till (Alderwood series) according to the Geotechnical Engineering Report. Runoff in the existing condition sheet flows to the south. An area summary of the predeveloped condition has been included in section 1.0. B. Developed Site Hydrology The developed site consists of 3 new single-family residential lots and associated driveway and landscaping. The proposed project will propose to design the on-site impervious to each lot to 4,400 square feet of rooftop and driveway to be routed to on-site infiltration trenches. The runoff from the proposed roadway and sidewalk will be directly discharged to the existing drainage facilities in 156th Avenue SE. WWHM models show that the project complies with minimum requirement #3 with the use of infiltration facilities for the on-site portion of runoff and direct discharge of the offsite road improvements. C. Performance Standards The project is located within the City of Renton. The project site lies within the level 3 flood prone flow control standards. The project does not exceed the thresholds requiring a flow control facility per the 2022 City of Renton Surface Water Management Manual. The project as proposed is increasing flows from the historic predeveloped condition by less than 0.15 cfs using a 15-minute time step. See calculations in Appendix B. As a part of the Flow Control BMPs and minimum requirement #9, the proposed project is choosing the list approach for minimum requirement #9. The BMP Requirements have been summarized below for feasibility: Full Dispersion: This BMP is infeasible due to lack of available flow path and native vegetation. Full Infiltration: This BMP is feasible for the on-site portion of the development and will be utilized. Infiltration rate calculations have been completed in accordance with the 2022 City of Renton Surface Water Management Manual. Limited Infiltration: Not applicable as full infiltration will be utilized. Bioretention: Not applicable as full infiltration will be utilized. Permeable Pavement: Not applicable as full infiltration is proposed for the on-site BMPs. Permeable pavement is not proposed for the new public roads. Basic Dispersion: This BMP is infeasible as dispersion flowpaths cannot be met. Reduced Impervious Surface Credit: Not applicable. Soil Amendment: All disturbed soils will be amended in accordance with the City of Renton requirements. Perforated Pipe Connection: Not applicable. D. Flow Control System The proposed project will utilize full infiltration for the on-site portions of the project including rooftops, driveways and pervious surfaces. The right-of-way and future right-of-way areas will utilize direction connection to the existing storm drainage system in 156th Avenue SE. E. Water Quality System Water quality is required for this project as the pollution generating impervious surface is more than 5,000 square feet. Water quality will be met for the right-of-way and future right-of-way areas through the use of Contech stormfilters or other approved water quality BMPs. 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN The conveyance system will be adequately sized during the final engineering phase. 6.0 SPECIAL REPORTS AND STUDIES Soils Report: Soil Characterization and Infiltration Letter prepared by Innovative Geoservices dated December 20, 2022. The report has been included in Appendix A. 7.0 OTHER PERMITS Other permits necessary for this project include: • ROW permit 8.0 CSWPP ANALYSIS AND DESIGN The site will utilize Appendix D of the 2022 City of Renton Surface Water Management Manual and the standard design details from the 2019 Stormwater Management Manual for Western Washington for the erosion and sedimentation control design. Refer to the approved TESC plan. Below is a breakdown of how each require element is addressed: 1. Clearing Limits Clearing limits will be established in the field. Clearing limits will be clearly marked for fenced. 2. Cover Measures Disturbed areas will be covered through temporary or permanent means. Any soils unworked for more than 7 days during the dry season (May 1 to September 30) or 2 days during the wet season (October 1 to April 30) will have erosion control nets/blankets, plastic sheeting and temporary or permanent seeding. 3. Perimeter Protection Perimeter protection is proposed for the downslope areas as shown on the approved plans. Perimeter protection shall be used in the form of silt fence. 4. Traffic Area Stabilization A temporary construction entrance is proposed at the entry to the site. 5. Sediment Retention Sediment retention is proposed in the form of catch basin inlet protection as downstream catch basins from the subject project area. 6. Surface Water Collection Surface water will be intercepted by the silt fence. Any runoff that leaves the proposed site will be intercepted in downstream storm drainage systems. 7. Dewatering Controls No dewatering is anticipated as a part of this project. 8. Dust Control Dust control will be achieved by watering any exposed soils. 9. Flow Control Additional flow control measures are not required as a part of this project. 10. Control Pollutants The only anticipated potential source of pollutants associated with the project would be from mobile fueling of construction equipment as necessary. If necessary, mobile fueling shall be done in accordance with BMP A-48 from the 2021 King County Stormwater Pollution Prevention Manual. 11. Protect Existing and Proposed Flow Control BMPs There are no existing or proposed BMPs on or immediately downstream of the project site. The perimeter protection measures along with catch basin inlet protection will aid in the protection of any downstream storm drainage systems. 12. Maintain BMPs All BMPs will be maintained and repaired in accordance with BMP specifications. 13. Manage the Project The project will be managed to ensure that all applicable and installed BMPs are adequately maintained and functioning. In addition, any necessary modifications or repairs to the erosion control BMPs will be done immediately to avoid impact to downstream properties and storm systems. T E B A L D I ENG I N E E R I N G, LLC TE PROPOSED DRIVEWAY CONCRETE GRAVEL EXISTING PROPERTY BOUNDARY EXISTING CONTOUR LINE EXISTING GRAVEL DRIVEWAY EXISTING LOT LINE EXISTING EASEMENT LINE 15 6 LOT 2 T E B A L D I ENG I N E E R I N G, LLC TE PROPOSED DRIVEWAY CONCRETE GRAVEL EXISTING PROPERTY BOUNDARY EXISTING CONTOUR LINE EXISTING GRAVEL DRIVEWAY EXISTING LOT LINE EXISTING EASEMENT LINE Soil Map—King County Area, Washington (Soils Map) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/8/2024 Page 1 of 3 52 5 9 5 8 0 52 5 9 5 9 0 52 5 9 6 0 0 52 5 9 6 1 0 52 5 9 6 2 0 52 5 9 6 3 0 52 5 9 6 4 0 52 5 9 5 8 0 52 5 9 5 9 0 52 5 9 6 0 0 52 5 9 6 1 0 52 5 9 6 2 0 52 5 9 6 3 0 52 5 9 6 4 0 565350 565360 565370 565380 565390 565400 565410 565420 565430 565440 565450 565460 565350 565360 565370 565380 565390 565400 565410 565420 565430 565440 565450 565460 47° 29' 13'' N 12 2 ° 7 ' 5 7 ' ' W 47° 29' 13'' N 12 2 ° 7 ' 5 1 ' ' W 47° 29' 10'' N 12 2 ° 7 ' 5 7 ' ' W 47° 29' 10'' N 12 2 ° 7 ' 5 1 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 20 40 80 120 Feet 0 5 10 20 30 Meters Map Scale: 1:514 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 19, Aug 29, 2023 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 31, 2022—Aug 8, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—King County Area, Washington (Soils Map) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/8/2024 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes 1.2 100.0% Totals for Area of Interest 1.2 100.0% Soil Map—King County Area, Washington Soils Map Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 7/8/2024 Page 3 of 3 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Maintenance covenants will be prepared, reviewed, and recorded prior to plan approval if required. All bond quantity forms and required bonds will be secured prior to permit issuance. 10.0 OPERATIONS AND MAINTENANCE MANUAL A separate operations and maintenance manual will be provided during the final engineering phase. APPENDIX A INNOVATIVE GEO-SERVICES, LLC ENGINEERING GEOLOGY SERVICES ENGGEOLOGIST.COM 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Van Vuong December 20, 2022 14349 SE 92nd ST Newcastle, WA 98059 Soil Characterization and Infiltration Letter Address 12820 156th AV SE Renton, WA Parcel No. 3664500165 Site Visit Performed 12/09/2022 INTRODUCTION It is the intent of this evaluation to describe the surface and subsurface conditions observed on the residential lot located at 12820 156th AV SE in Renton, WA. Site observations are related to surface water runoff and storm water control planning. The parcel is a developed 46,575 sf lot (1.07 acre) with access from 156th AV SE which extends across the west property line. The parcel contains a single-family structure on the western third of the lot with a paved driveway entering the lot at the northwest corner. Development plans call for creating a three-lot plat with the existing home on 123 ft wide western most lot and two new 83 ft wide lots to the east. Access to the three-lot plat will be via a new road extending east across the south property line. This report is for the exclusive use of Van Vuong, his consultants and contractors for the intended purpose described. Site observations and exploration methods applied and described in this study represent the standard of practices for the industry. Sources of information cited are uniformly accepted resources when utilized in conjunction with field reconnaissance as confirmation. Opinions are based on using these standardized practices to adequately characterize the local surficial geology and general conditions at the site. SITE AND PROJECT DESCRIPTION The 1.07-acre parcel is a rectangular lot extending east from 156th AV SE approximately 289 ft. and is nearly 161 ft wide. The parcel will be divided into three lots with the existing home on the western 123 ft lot and two 83 ft wide lots to the east. Access to the three lots will be provided by a new road across the south property line. The parcel is located in an established residential neighborhood with direct access from 156th AV SE. Surface grades across the parcel are predominantly gentle, rising gently across the parcel to the north and northeast. The new residential plat will be served by municipal water, sewer and private storm water control systems. Sewer service will be extended east from 156th AV SE near the southwest corner of the parcel and water service will be extended from the northwest corner. Surface water runoff currently flows to the south and southwest across the grassy areas surrounding the home. Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 2 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Site plan Topography and Aerial Photo obtained from King County GIS EVALUATION METHODS We Observed surface and subsurface conditions at the project site on December 9th, 2022. Our evaluation involved a review of available public mapping and information, three exploration soil pits and conducted two EPA Falling Head Perk tests. SITE SOILS The Natural Resources Conservation Service (NRCS) describes the soil across the parcels as Alderwood gravelly sandy loam. This silty, sand and gravel were derived from glacial deposits from the advance and retreat of the Frasier Ice sheet across the region. IGS Soil Pit and Perk Test IGS Soil Pit and Perk Test Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 3 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Alderwood AgC – Alderwood gravelly sandy loam, 8 – 15 percent slopes This rolling Alderwood soil is moderately well drained. It formed in glacial till on broad uplands. Vegetation is hardwoods and conifers. Elevation ranges from 200 to 800 feet. The mean annual precipitation is about 35 inches, mean annual air temperature is about 50 degrees F, and the frost- free season averages about 180 days. Individual soil areas average about 125 acres in size. Most slopes average about 8 percent. Granite boulders and stones are strewn across some slopes. Included with this soil in mapping are small areas of better drained Indianola loamy sand on the side slopes and poorer drained Norma sandy loam or Dupont muck in troughs. In addition, some areas of Alderwood gravelly sandy loam and Kapowsin gravelly loam, zero to six percent slopes, are included. In a typical soil profile, a mat of undecomposed needles and wood fragments rests upon a 1 ½ inch thick very dark grayish brown gravelly sandy loam surface layer. The subsoil and the upper part of the substratum, to a depth of 38 inches, are dark yellowish brown, brown, and dark grayish brown gravelly VUONG PROPERTY (APPROX. LOCATION) Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 4 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com sandy loam. The lower parrot of the substratum, to a depth of more than 60 inches, is weakly cemented compact glacial till. Reaction is medium acid. The water table is perched above the very slowly permeable, weakly cemented and compact part of the substratum during periods of heavy rainfall. However, the perched water table is of short duration because the water flows laterally above this layer to seeps at the bottom of slopes. Very few roots penetrate this dense substratum. The available water capacity is low. Surface runoff is medium, and the erosion hazard is moderate. Because of its proximity to urban centers, this Alderwood soil is subject to urbanization pressure. The soil has an inherent ability to support a large load. Soil slope and the weakly cemented, compact substratum are its limiting features. In areas of moderate to high population density, onsite sewage disposal systems often fail or do not function properly during periods of rainfall in winter. Excavation for basements and utility lines is difficult to cover excavated soil material. SITE GEOLOGY According to maps from the Washington Division of Geology and Earth Resources, this region of King County lies in the glacial lowland area of multiple glacial advance and recessional periods. The surface deposits are described as glacial till consisting of well compacted, fine to medium grain, poorly sorted sand with gravel and cobbles. Geology of the Renton Quadrangle, WA, (Excerpt) Mapping prepared by D.R. Mullineaux, 1965 Findings / Infiltration Feasibility On December 9th, 2022, IGS visually inspected the parcel and observed the excavation of three exploratory soil pits. Two soil pits were excavated near the southwest and southeast portions of the parcel. Infiltration testing was conducted in each hole at a depth of 18 in. to 24 in. Raw infiltration rates were observed in the two shallow soil pits using the EPA Falling Head guidelines. Following each test the exploratory soil pit was excavated to a depth of 5 ft. to confirm soil textures below the test elevation. The native soil is described as silty, gravelly sand consistent with the NRCS classification of Alderwood gravelly sandy loam. No groundwater or indications of seasonal groundwater were observed in the soil pits. VUONG PROPERTY Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 5 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Infiltration testing in TP 1 indicates a raw infiltration rate of 5 in/hr. at 18 in and 7 in/hr. in TP 2 at 24 in. Testing was conducted in tan silty sand with small gravel and rocks. We recommend using an infiltration rate of 4 in/hr. for storm water infiltration or dispersion planning. Vegetative ground cover consisting of grasses with landscape shrubs and a few conifer trees. Glacial Till (restrictive layer) was encountered at a depth of 60 in. across the south side of the parcel and 48 in. in the north. Site observations indicate the soil is consistent across the property. CLOSURE Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. We appreciate the opportunity to be of service on this project. If you have any questions regarding this letter or any aspects of the project, please feel free to contact our office. Respectfully submitted, Innovative GEO-Services, LLC Rex Humphrey, L.E.G. Principal Engineering Geologist Attached: Soil Test Pits TP 1, 2 and 3 12/20/2022 Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 6 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 7 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com Vuong Soil and Infiltration Study 12820 156th AV SE, Renton December 20, 2022 Page 8 253 279-4205 17903 82nd ST E, Bonney Lake, WA 98391 rex@enggeologist.com APPENDIX B WWHM2012 PROJECT REPORT v 7/8/2024 1:07:40 PM Page 2 General Model Information WWHM2012 Project Name:v Site Name:VUONG Site Address: City: Report Date:7/8/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.167 Version Date:2023/03/31 Version:4.2.19 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year v 7/8/2024 1:07:40 PM Page 3 Landuse Basin Data Predeveloped Land Use PREDEV Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 1.12 Pervious Total 1.12 Impervious Land Use acre Impervious Total 0 Basin Total 1.12 v 7/8/2024 1:07:40 PM Page 4 Mitigated Land Use OFFSITE Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.063 Pervious Total 0.063 Impervious Land Use acre ROADS FLAT 0.199 DRIVEWAYS FLAT 0.017 SIDEWALKS FLAT 0.042 Impervious Total 0.258 Basin Total 0.321 v 7/8/2024 1:07:40 PM Page 5 On-site (Each Lot) Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.1 Impervious Total 0.1 Basin Total 0.1 v 7/8/2024 1:07:40 PM Page 6 Routing Elements Predeveloped Routing v 7/8/2024 1:07:40 PM Page 7 Mitigated Routing Gravel Trench Bed 1 Bottom Length:100.00 ft. Bottom Width:4.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1.5 Pour Space of material for first layer:0.3 Material thickness of second layer:0 Pour Space of material for second layer:0 Material thickness of third layer:0 Pour Space of material for third layer:0 Infiltration On Infiltration rate:4 Infiltration safety factor:1 Total Volume Infiltrated (ac-ft.):18.616 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):18.616 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:1.5 ft. Riser Diameter:10 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.009 0.000 0.000 0.000 0.0278 0.009 0.000 0.000 0.037 0.0556 0.009 0.000 0.000 0.037 0.0833 0.009 0.000 0.000 0.037 0.1111 0.009 0.000 0.000 0.037 0.1389 0.009 0.000 0.000 0.037 0.1667 0.009 0.000 0.000 0.037 0.1944 0.009 0.000 0.000 0.037 0.2222 0.009 0.000 0.000 0.037 0.2500 0.009 0.000 0.000 0.037 0.2778 0.009 0.000 0.000 0.037 0.3056 0.009 0.000 0.000 0.037 0.3333 0.009 0.000 0.000 0.037 0.3611 0.009 0.001 0.000 0.037 0.3889 0.009 0.001 0.000 0.037 0.4167 0.009 0.001 0.000 0.037 0.4444 0.009 0.001 0.000 0.037 0.4722 0.009 0.001 0.000 0.037 0.5000 0.009 0.001 0.000 0.037 0.5278 0.009 0.001 0.000 0.037 0.5556 0.009 0.001 0.000 0.037 0.5833 0.009 0.001 0.000 0.037 0.6111 0.009 0.001 0.000 0.037 0.6389 0.009 0.001 0.000 0.037 v 7/8/2024 1:07:40 PM Page 8 0.6667 0.009 0.001 0.000 0.037 0.6944 0.009 0.001 0.000 0.037 0.7222 0.009 0.002 0.000 0.037 0.7500 0.009 0.002 0.000 0.037 0.7778 0.009 0.002 0.000 0.037 0.8056 0.009 0.002 0.000 0.037 0.8333 0.009 0.002 0.000 0.037 0.8611 0.009 0.002 0.000 0.037 0.8889 0.009 0.002 0.000 0.037 0.9167 0.009 0.002 0.000 0.037 0.9444 0.009 0.002 0.000 0.037 0.9722 0.009 0.002 0.000 0.037 1.0000 0.009 0.002 0.000 0.037 1.0278 0.009 0.002 0.000 0.037 1.0556 0.009 0.002 0.000 0.037 1.0833 0.009 0.003 0.000 0.037 1.1111 0.009 0.003 0.000 0.037 1.1389 0.009 0.003 0.000 0.037 1.1667 0.009 0.003 0.000 0.037 1.1944 0.009 0.003 0.000 0.037 1.2222 0.009 0.003 0.000 0.037 1.2500 0.009 0.003 0.000 0.037 1.2778 0.009 0.003 0.000 0.037 1.3056 0.009 0.003 0.000 0.037 1.3333 0.009 0.003 0.000 0.037 1.3611 0.009 0.003 0.000 0.037 1.3889 0.009 0.003 0.000 0.037 1.4167 0.009 0.003 0.000 0.037 1.4444 0.009 0.004 0.000 0.037 1.4722 0.009 0.004 0.000 0.037 1.5000 0.009 0.004 0.000 0.037 1.5278 0.009 0.004 0.040 0.037 1.5556 0.009 0.004 0.115 0.037 1.5833 0.009 0.004 0.211 0.037 1.6111 0.009 0.005 0.323 0.037 1.6389 0.009 0.005 0.445 0.037 1.6667 0.009 0.005 0.575 0.037 1.6944 0.009 0.005 0.706 0.037 1.7222 0.009 0.006 0.835 0.037 1.7500 0.009 0.006 0.957 0.037 1.7778 0.009 0.006 1.067 0.037 1.8056 0.009 0.006 1.163 0.037 1.8333 0.009 0.007 1.242 0.037 1.8611 0.009 0.007 1.305 0.037 1.8889 0.009 0.007 1.355 0.037 1.9167 0.009 0.008 1.396 0.037 1.9444 0.009 0.008 1.458 0.037 1.9722 0.009 0.008 1.503 0.037 2.0000 0.009 0.008 1.546 0.037 2.0278 0.009 0.009 1.589 0.037 2.0556 0.009 0.009 1.630 0.037 2.0833 0.009 0.009 1.670 0.037 2.1111 0.009 0.009 1.709 0.037 2.1389 0.009 0.010 1.748 0.037 2.1667 0.009 0.010 1.785 0.037 2.1944 0.009 0.010 1.822 0.037 2.2222 0.009 0.010 1.858 0.037 2.2500 0.009 0.011 1.894 0.037 v 7/8/2024 1:07:40 PM Page 9 2.2778 0.009 0.011 1.929 0.037 2.3056 0.009 0.011 1.963 0.037 2.3333 0.009 0.011 1.996 0.037 2.3611 0.009 0.012 2.029 0.037 2.3889 0.009 0.012 2.062 0.037 2.4167 0.009 0.012 2.094 0.037 2.4444 0.009 0.012 2.125 0.037 2.4722 0.009 0.013 2.156 0.037 2.5000 0.009 0.013 2.187 0.037 v 7/8/2024 1:07:40 PM Page 10 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.12 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.063 Total Impervious Area:0.358 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.043753 5 year 0.072135 10 year 0.093679 25 year 0.123788 50 year 0.148206 100 year 0.174259 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.124641 5 year 0.159355 10 year 0.183162 25 year 0.21427 50 year 0.238233 100 year 0.262902 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.054 0.167 1950 0.063 0.169 1951 0.090 0.103 1952 0.030 0.084 1953 0.025 0.093 1954 0.037 0.102 1955 0.057 0.115 1956 0.046 0.111 1957 0.042 0.130 1958 0.042 0.102 v 7/8/2024 1:08:04 PM Page 11 1959 0.036 0.102 1960 0.070 0.107 1961 0.035 0.109 1962 0.024 0.092 1963 0.034 0.109 1964 0.043 0.101 1965 0.032 0.134 1966 0.028 0.087 1967 0.066 0.153 1968 0.039 0.176 1969 0.038 0.123 1970 0.031 0.117 1971 0.040 0.139 1972 0.069 0.149 1973 0.032 0.084 1974 0.037 0.130 1975 0.052 0.137 1976 0.037 0.100 1977 0.013 0.102 1978 0.031 0.130 1979 0.019 0.173 1980 0.098 0.166 1981 0.029 0.129 1982 0.068 0.187 1983 0.047 0.145 1984 0.030 0.093 1985 0.017 0.128 1986 0.073 0.108 1987 0.067 0.169 1988 0.029 0.099 1989 0.018 0.134 1990 0.187 0.238 1991 0.084 0.189 1992 0.035 0.092 1993 0.034 0.086 1994 0.014 0.086 1995 0.045 0.113 1996 0.107 0.128 1997 0.084 0.121 1998 0.030 0.118 1999 0.117 0.256 2000 0.033 0.124 2001 0.008 0.134 2002 0.045 0.161 2003 0.062 0.131 2004 0.072 0.238 2005 0.047 0.106 2006 0.049 0.096 2007 0.139 0.223 2008 0.147 0.185 2009 0.066 0.154 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1874 0.2555 2 0.1473 0.2381 3 0.1386 0.2380 v 7/8/2024 1:08:04 PM Page 12 4 0.1167 0.2234 5 0.1068 0.1891 6 0.0979 0.1866 7 0.0900 0.1845 8 0.0845 0.1758 9 0.0844 0.1730 10 0.0731 0.1691 11 0.0722 0.1687 12 0.0698 0.1673 13 0.0687 0.1664 14 0.0680 0.1613 15 0.0672 0.1539 16 0.0665 0.1526 17 0.0663 0.1492 18 0.0625 0.1453 19 0.0623 0.1388 20 0.0568 0.1369 21 0.0536 0.1340 22 0.0521 0.1336 23 0.0491 0.1336 24 0.0474 0.1310 25 0.0467 0.1301 26 0.0462 0.1300 27 0.0455 0.1296 28 0.0454 0.1290 29 0.0429 0.1283 30 0.0424 0.1280 31 0.0418 0.1237 32 0.0399 0.1231 33 0.0389 0.1211 34 0.0375 0.1183 35 0.0371 0.1168 36 0.0368 0.1155 37 0.0366 0.1130 38 0.0360 0.1106 39 0.0352 0.1089 40 0.0349 0.1087 41 0.0342 0.1081 42 0.0341 0.1069 43 0.0326 0.1061 44 0.0325 0.1031 45 0.0319 0.1020 46 0.0315 0.1018 47 0.0311 0.1017 48 0.0301 0.1016 49 0.0301 0.1008 50 0.0295 0.0996 51 0.0289 0.0987 52 0.0285 0.0957 53 0.0283 0.0931 54 0.0254 0.0930 55 0.0237 0.0923 56 0.0194 0.0918 57 0.0181 0.0866 58 0.0173 0.0857 59 0.0139 0.0855 60 0.0128 0.0841 61 0.0085 0.0836 v 7/8/2024 1:08:04 PM Page 13 v 7/8/2024 1:08:04 PM Page 14 Duration Flows The Duration Matching Failed Flow(cfs)Predev Mit Percentage Pass/Fail 0.0219 18454 25581 138 Fail 0.0232 16093 22972 142 Fail 0.0244 14324 20621 143 Fail 0.0257 12694 18630 146 Fail 0.0270 11176 16788 150 Fail 0.0283 9888 15197 153 Fail 0.0295 8816 13740 155 Fail 0.0308 7843 12523 159 Fail 0.0321 7005 11400 162 Fail 0.0334 6288 10316 164 Fail 0.0346 5679 9428 166 Fail 0.0359 5168 8609 166 Fail 0.0372 4699 7841 166 Fail 0.0385 4278 7101 165 Fail 0.0397 3903 6504 166 Fail 0.0410 3527 5961 169 Fail 0.0423 3183 5480 172 Fail 0.0436 2864 5048 176 Fail 0.0448 2592 4616 178 Fail 0.0461 2353 4250 180 Fail 0.0474 2139 3895 182 Fail 0.0487 1951 3583 183 Fail 0.0499 1796 3320 184 Fail 0.0512 1669 3086 184 Fail 0.0525 1514 2832 187 Fail 0.0538 1343 2624 195 Fail 0.0551 1223 2430 198 Fail 0.0563 1123 2274 202 Fail 0.0576 1042 2119 203 Fail 0.0589 969 1951 201 Fail 0.0602 910 1804 198 Fail 0.0614 838 1678 200 Fail 0.0627 766 1559 203 Fail 0.0640 704 1465 208 Fail 0.0653 633 1361 215 Fail 0.0665 570 1255 220 Fail 0.0678 488 1164 238 Fail 0.0691 425 1095 257 Fail 0.0704 376 1017 270 Fail 0.0716 341 954 279 Fail 0.0729 307 901 293 Fail 0.0742 270 848 314 Fail 0.0755 235 804 342 Fail 0.0767 196 743 379 Fail 0.0780 171 705 412 Fail 0.0793 145 664 457 Fail 0.0806 125 626 500 Fail 0.0819 107 592 553 Fail 0.0831 95 561 590 Fail 0.0844 84 533 634 Fail 0.0857 71 491 691 Fail 0.0870 61 468 767 Fail 0.0882 55 436 792 Fail 0.0895 45 417 926 Fail v 7/8/2024 1:08:04 PM Page 15 0.0908 40 400 1000 Fail 0.0921 37 383 1035 Fail 0.0933 35 359 1025 Fail 0.0946 29 350 1206 Fail 0.0959 25 336 1344 Fail 0.0972 22 319 1450 Fail 0.0984 17 305 1794 Fail 0.0997 15 287 1913 Fail 0.1010 11 271 2463 Fail 0.1023 9 253 2811 Fail 0.1035 8 242 3025 Fail 0.1048 8 227 2837 Fail 0.1061 8 219 2737 Fail 0.1074 7 206 2942 Fail 0.1086 7 197 2814 Fail 0.1099 7 188 2685 Fail 0.1112 7 180 2571 Fail 0.1125 7 173 2471 Fail 0.1138 7 164 2342 Fail 0.1150 7 161 2300 Fail 0.1163 6 154 2566 Fail 0.1176 5 146 2920 Fail 0.1189 5 136 2720 Fail 0.1201 5 128 2560 Fail 0.1214 4 123 3075 Fail 0.1227 4 122 3050 Fail 0.1240 4 116 2900 Fail 0.1252 4 110 2750 Fail 0.1265 4 108 2700 Fail 0.1278 4 106 2650 Fail 0.1291 4 100 2500 Fail 0.1303 4 91 2275 Fail 0.1316 4 88 2200 Fail 0.1329 4 87 2175 Fail 0.1342 3 81 2700 Fail 0.1354 3 78 2600 Fail 0.1367 3 78 2600 Fail 0.1380 3 75 2500 Fail 0.1393 2 71 3550 Fail 0.1405 2 69 3450 Fail 0.1418 2 64 3200 Fail 0.1431 2 63 3150 Fail 0.1444 2 63 3150 Fail 0.1457 2 60 3000 Fail 0.1469 2 58 2900 Fail 0.1482 1 57 5700 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. v 7/8/2024 1:08:04 PM Page 16 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. v 7/8/2024 1:08:04 PM Page 17 LID Report v 7/8/2024 1:08:12 PM Page 18 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. v 7/8/2024 1:08:12 PM Page 19 Appendix Predeveloped Schematic v 7/8/2024 1:08:12 PM Page 20 Mitigated Schematic v 7/8/2024 1:08:13 PM Page 21 Predeveloped UCI File v 7/8/2024 1:08:13 PM Page 22 Mitigated UCI File v 7/8/2024 1:08:13 PM Page 23 Predeveloped HSPF Message File v 7/8/2024 1:08:13 PM Page 24 Mitigated HSPF Message File v 7/8/2024 1:08:13 PM Page 25 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2024; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com