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19-105869-00-SU-Exhibit #004-Tech Information Report-12-11-2020-V1
PRELIMINARY TECHNICAL INFORMATION REPORT for 37325 8TH AVE S FEDERAL WAY SHORT SUBDIVISION Owner/Applicant Eunhee Kim 37325 8th Ave S Federal Way, WA 98003 (818) 321-4243 Report Prepared by Eui Kim Professional Engineer 37325 8th Ave S Federal Way, WA 98003 (818) 321-4243 Report Issue Date December 15, 2019 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 1 of 53 Revision: December 10, 2020 Eui Kim Professional Engineer PRELIMINARY TECHNICAL INFORMATION REPORT 37325 8TH AVE PRELIMINARY PLAT TABLE OF CONTENTS SECTION I ...................................................................................................................... 4 PROJECT OVERVIEW ............................................................................................... 4 PREDEVELOPED SITE CONDITIONS ....................................................................... 4 DEVELOPED SITE CONDITIONS .............................................................................. 4 NATURAL DRAINAGE SYSTEM FUNCTIONS .......................................................... 5 SECTION II ..................................................................................................................... 6 CONDITIONS AND REQUIREMENTS SUMMARY .................................................... 6 SECTION III .................................................................................................................... 8 OFF-SITE ANALYSIS.................................................................................................. 8 TASK 1: DEFINE AND MAP THE STUDY AREA ........................................................ 8 TASK 2: RESOURCE REVIEW ................................................................................... 8 TASK 3: FIELD INSPECTION ..................................................................................... 9 TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS ... 9 TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS ......................... 9 SECTION IV .................................................................................................................... 9 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ...... 9 EXISTING SITE HYDROLOGY (PART A) ................................................................... 9 TASK 4.1: Flow Control and Water Quality Design ................................................... 10 4.4 Water Quality ....................................................................................................... 11 SECTION V ................................................................................................................... 11 CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................. 11 TASK 5.1: CONVEYANCE SYSTEM ANALYSIS AND DESIGN ............................... 11 APPENDIX A ................................................................................................................ 33 Rational Runoff Calculation and determining Storm drain Pipe Size ....................... 33 APPENDIX B ................................................................................................................ 42 WWHM Output .......................................................................................................... 42 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 2 of 53 PRELIMINARY TECHNICAL INFORMATION REPORT 37325 8TH AVE PRELIMINARY PLAT TABLE OF CONTENTS ADDITION; 1. Wetland Determination Reconnaissance Report 2. Frontage Improvement of engineering plan is attached as C-01, C02 and C03 and storm drainage, erosion and sediment control are included into the drawing. Eui Kim Professional Engineer List of Figures Figure 1A Site Map .........................................................................................................13 Figure1B the Green/Duwamish River Watershed.......................................................... 14 Figure 2 TIR Worksheet ………………………………………………… ........................... 15 Figure 3 Geologic Map……............................................................................................ 20 Figure 4 King County iMAP showing Elevation, Environmental Sensitive Area, Flood Inf, Stormwater Service Area, Wetland................................................... 21 Figure 4.1 FEMA Firm Flood Insurance Rate Map ………………………………………. 22 Figure 5 Land Slide Hazard Area, Seismic Hazard Area ............................................. 24 Figure 6 Development Area Map .................................................................................. 25 Figure 7 Drainage Basins & Site Characteristic Map ................................................... 26 Table 1 soil Pit analysis and Test ……………………………………….…………………27 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 3 of 53 SECTION I PROJECT OVERVIEW The Project is the Short subdivision of the one existing parcel into 4 single-family residential lots per the City of Federal Way (City) subdivision process. Each parcel is zoned RS 35 and sums up to a total site area of 3.547 acres. The Tax Parcel Number is 3221049023. The Project location is 37325 8th Ave S, Federal Way; King County, Washington. The Project will meet the drainage requirements of the 2016 King County Surface Water Design Manual (Manual). The purpose of this Preliminary Technical Information Report (TIR) is to provide the technical information and design analysis required for preparing the drainage design for the proposed 4 lots short subdivision on subject parcel. The City of Federal Way adopted the current 2016 King County Surface Water Design Manual (2016 KCSWDM) for all development within the city. This project will follow the 2016 KCSWDM requirements. The proposed development is 4-lot Short Plat on a rectangular-shaped parcel within the RS35.0 (Single Family Residential) zone. The project site is bordered to south by a residential church adjacent, east by 8th Ave, and north by 373rd Street. The total lot area is approximately 154,487 SF (3.547 acre). PREDEVELOPED SITE CONDITIONS Total existing Site area is approximately 154,487 s.f. (3.547 ac). The total project development area is 154,487 s.f. (3.547 ac) which excludes Road dedicated to the City of Federal Way. The Site contains one single family residences, associated driveways and outbuildings, and landscaping. The Site sits on the hill sloped to a ridge and slopes to the east west. The whole of the site is moderately sloping westerly and easterly and is surrounded by 373th Street S and 8th Ave on the north and east, respectively. Topography indicates that the Site is contained within single distinct Threshold Discharge Areas, TDA A shown on the TDA map on Figure 7. TDA appears to be similar in land use/cover with developed areas of landscaping and home sites along with portions of forested. For the purpose of hydrologic calculations, the entire Site is modeled as till forest. DEVELOPED SITE CONDITIONS The applicant is seeking approval to subdivide 5.41 acres into 4 single–family residential lots with sizes ranging from approximately 35,000 s.f. to 36,600 s.f. All existing improvements located on the Site will be stayed until separate plat construction permit. Impervious surfaces include the 4 residences and their driveways, the proposed roadways dedicated to the City of Federal Way after short-subdivision done by individual owner and the City. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 4 of 53 119.41'119.41' 244.18'30'35'30'30'30'30'30'30'30' 30'30' 2'-11"'2'-11"'2'-11"'CENTERLINE LINE PER (R4) LOT 2 35,008.22 S.F. S 373RD ST.DRIVEWAY1'-8"'149.99'143.37'298.38' (C & R2)30'30'30'30'30'30' 2'-11"' 2'-11"'2'-11"'N01°23'32"E 2626.78' MON TO MON8TH AVE S656.76' (C) 665.75' (R2)S 3 7 5 T H S T . S 37 3 R D P L. 1'-8"' 10"' GRACELAND SHORT PLAT CITY OF FEDERAL WAY, WASHINGTON (N)STREET DESIGN Scale: 1"= 60'-0" STREET 373TH S1 Scale: 1"= 60'-0" STREET 8TH AVE2 Scale: 1"=20'-0" STREET P- TYPE3 Scale: N/A STREET LIGHTING DETAILD Scale: N/A DRIVE ENTRYC Scale: 1"=10'-0" SECTION BB Scale: 1"=10'-0" SECTION AA A - B - C D 2'-11"'2'-11"'GRACELAND SHORT PLAT CITY OF FEDERAL WAY, WASHINGTON (N)EROSION & BMP PLAN 1.EXCAVATION BELOW EXISTING FINISH GRADE ARE FOR FOOTING FOR THE CONSTRUCTION OF A BUILDING ONLY AND WILL BE AUTHORIZED BY A BUILDING PERMIT. 2.ANY CUT OR FILL SHALL NOT EXCEED 50 CUBIC YARDS OF MATERIAL NOR EXCEED ONE FOOT IN DEPTH OR HEIGHT. 3. IF MORE THAN 50 CUBIC YARDS OF CUT AND FILL IS BEING MOVED ON THE PROJECT SITE A GRADING PERMIT SHALL BE REQUIRED FROM THE PUBLIC WORKS DEPARTMENT. 4. IF CUT/FILL IS LESS THAN 50 CUBIC YARDS: EROSION AND SEDIMENT CONTROL BEST MANAGEMENT PRACTICES SHALL BE IMPLEMENTED AND MAINTAINED TO MINIMIZE AND/OR PREVENT THE TRANSPORT OF SOIL FROM THE CONSTRUCTION SITE. APPROPRIATE BMPS FOR CONSTRUCTION RELATED MATERIALS, WASTES, SPILLS, OR RESIDUES SHALL BE IMPLEMENTED TO ELIMINATE OR REDUCE TRANSPORT FROM THE SITE TO THE STREETS, DRAINAGE FACILITIES, OR ADJOINING PROPERTIES BY WIND OR RUNOFF. 5. LOTS SHALL BE GRADED TO DRAIN SURFACE WATER AWAY FROM THE FOUNDATION WALLS. THE GRADE SHOULD FALL A MIN. OF 6" WITHIN THE FIRST 10 FT (5%). WHERE LOT LINES, WALLS, SLOPES OR OTHER PHYSICAL BARRIER PROHIBIT 6" OF FALL WITHIN 10 FT, DRAINS OR SWALES SHALL BE CONSTRUCTED TO ENSURE DRAINAGE AWAY FROM THE STRUCTURE (CRC R401.3). 6. IMPERVIOUS SURFACES WITHIN 10 FT OF THE BUILDING FOUNDATION SHALL BE SLOPED A MIN. OF 2% AWAY FROM THE BUILDING (CRC R401.3 EXCEPTION). 7. WE, THE DESIGNER,ENGINEER, CONTRACTOR AND PROPERTY OWNER(S) OF A PROJECT HEREIN THE ATTACHED SET OF DRAWINGS, UNDERSTAND THAT SAID INFORMATION WILL BE A BASIS FOR SUBSEQUENT CITY ACTION ON THE PROJECT PROPOSED AND DESCRIBED HEREON. P.L. 20% max SLOPE 2% min SLOPE CONC. FTG PER STRUCTURAL DESIGN TOP OF SLAB ELEVATION PER PLAN 1. REPLACE EXISTING DRAINAGE TOWARD RETAINING WALL. 2. PROVIDE NEW MIN. SLOPE 2%. 1. THE CONTRACTOR SHALL BE RESPONSIBLE TO INSTALL ALL EROSION CONTROL FACILITIES AS SHOWN ON THE APPROVED EROSION CONTROL PLAN OR AS DIRECTED BY THE CITY ENGINEER AT THE END OF EACH WORKING DAY. A.WHENEVER THE 5-DAY RAIN PROBABILITY EXCEEDS 40% BETWEEN THE DATES OF OCTOBER 15 AND APRIL (RAIN SEASON). B.WHENEVER THE DAILY RAIN PROBABILITY EXCEEDS 50% THE REMAINDER OF THE YEAR AND APRIL 15 (RAINY SEASON). 2.THE CONTACT PERSON RESPONSIBLE FOR EROSION CONTROL IS THE OWNER. 3.THE CONTRACTOR SHALL BE RESPONSIBLE FOR PROVIDING AN EMERGENCY WORK CREW AT ALL TIMES DURING THE RAINY SEASON THE CONTRACTOR SHALL STOCKPILE THE NECESSARY EROSION CONTROL MATERIALS ON SITE TO FACILITATE RAPID INSTALLATION OF EROSION CONTROL FACILITIES. 4. THE CONTRACTOR SHALL CONSTRICT DESILTING FACILITIES AS NECESSARY FOR THE DURATION OF THE PROJECT. 5.THE CONTRACTOR SHALL TAKE MEASURE TO PREVENT RUNOFF OVER THE TOP OF THE SLOPES. 6. AFTER RAIN STORM: A.THE CONTRACTOR SHALL REMOVE ALL SILT,STANDING WATER ,AND DEBRIS FROM EROSION CONTROL FACILITIES. B.THE CONTRACTOR SHALL BE RESPONSIBLE TO PREVENT PUBLIC ACCESS INTO AREAS WHERE STANDING WATER POSES A POTENTIAL HAZARD. 7 .IN HIGH WIND AREAS THE CONTRACTOR SHALL WATER SPRAY GRADED AREAS ON a DAILY BASIS TO CONTROL DUST OR WINDY PERIODS,WHEN NECESSARY,THE CONTRACTOR SHALL TAKE MEASURES TO CONTROL DUST OR WIND BLOWN DEBRIS BY INSTALLING DEBRIS FENCES,ADDITIONAL TRASH ENCLOSURES ,CHEMICAL LAND TREATMENT ,GEOMATS ,ETC.THE CONTRACTOR SHALL IMPLEMENT LONG TERM WIND EROSION CONTROL MEASURES FOR ANY AREA THAT IS NOT IMPROVED IN A MANNER FOLLOWING GRADING LONG TERM WIND EROSION CONTROL MEASURES INCLUDE BUT NOT LIMITED TO:PERIMETER WALLS ,WIND BARRIERS ,SOIL DUST PALLIATIVES ,SOIL MATS , HYDROSEEDING AND IRRIGATION SYSTEM . 8. THE CITY ENGINEER RESERVES THE RIGHT TO REQUIRE ALTERNATIVE OR ADDITIONAL EROSION CONTROL FACILITIES AS HE DEEMS NECESSARY. 9. PROVIDE PORTABLE TOILET AND HAND WASH STATION PER OSHA REGULATIONS OR PROVIDE ACCESS FOR CONSTRUCTION WORKERS TO RESTROOM INSIDE THE HOUSE. 10. THE DISCHARGE OF POLLUTANTS TO ANY STORM DRAINAGE IS PROHIBITED. NO SOLID WASTE, PETROLEUM BYPRODUCTS, SOIL PARTICULATE, CONSTRUCTION WASTE MATERIALS, OR WASTEWATER GENERATED ON CONSTRUCTION SITE OR CONSTRUCTION ACTIVITIES SHELL BE PLACED, CONVEYED OR DISCHARGED INTO THE STREET, GUTTER OR STORM DRAIN SYSTEM. Low Impact Development (LID) Post Construction Stormwater Mitigation Best Management Practices (BMPs) STORMWATER BMP(s) VERIFICATION Upon installation of the approved stormwater BMPs, a Stormwater Observation Report (SOR) Form shall be submitted to Department of Public Works, Bureau of Sanitation. 201 N. Figueroa, 3rd floor, station 18. The SOR Form must be with filed and approved by the Bureau of Sanitation prior to the issuance of a Certificate of Occupancy. Project Address: _______________________________________________________________________ RESIDENTIAL (1 UNITS OR LESS, <5,000SF) Item # Stormwater BMP 1 Rain Tank(s) – 55 to 130 gal each 2 Rain Tank(s) – > 130 gal min 3 4 Shade Tree - min 15 gal Flow thru Planter(s) 5 Permeable pavers/Porous concrete (min 10% open space) 6 Rain Garden 7 Dry Well 8 SUMP Pump (modification was not required) ALL OTHER DEVELOPMENT (Residential: 5 ≥ units, 10,000 ≥ SF, within a ESA and ≥2,500SF) Item #Stormwater BMP 1 Infiltration Basin / Trench 2 Dry Well 3 4 5 6 7 10 Permeable pavers / Porous concrete (min 10% open space) Rain Tank(s) – 530 gal min Cistern Flow thru Planter(s) Biofiltration 8 Vegetative Swale / Filter Strip 9 Catch Basin Filter(s) Trench Drain Filter(s) 11 Down Spout Filter(s) 12 SUMP Pump (modification was not required) * At a minimum: Site Plan, Architectural Elevations, Roof Plan, Civil Sheets and Detail #____ - Lined; ________total SF # ____ - Unlined; _____total SF Above Grade Below Grade Incidental;____________ total SF Infiltration;___________ total SF Incidental; ____________ total SF Infiltration; ___________ total SF #____ - Lined; _________total SF # ____ - Unlined; _______total SF Description (Units, total) Reference Sheet(s)* (Sheet #) Description (Units, total) Reference Sheet(s)* (Sheet #)Treat & DischargeCapture& UseInfiltration37325 8th Ave, Federal Way, WA 98003 xxx xxx Scale: 1"= 80'-0" 4 LOT SITE PLAN1 This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 To: Mr. Eunhee Kim 37325 8th Ave. S. Federal Way WA. 98003 Subject: Wetland Determination Reconnaissance Report RE: 37325 8th Ave. S. Federal Way WA. 98003 (Parcel # 3221049023) Background: BAI Inspection Services LLC. Inspection Specialist & Environmental Consultants has been retained by ABD Properties Mr. Eunhee Kim to perform a wetland site review of the subject property noted above. This reconnaissance site visit and report is to determine if the site contains any wetland conditions and / or characteristics of a wetland prior to the planned division lot split sales and development installation of a single-family residences, of the parcel property as shown in the addendum photographs at the rear of this report. Appendix “A” Definitions: Wetlands are those areas that are inundated or saturated by surface or ground water at a frequency and duration enough to support, and that under normal circumstances, do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Swamps, fresh and saltwater marshes, bogs, and some meadows are examples of wetlands. Some riparian areas adjacent to streams are also wetlands. BAI Inspection Services site visit was June 30/2020 @ 10:00AM. the weather was partial overcast and dry with recent rain during the spring hydro period with ambient temperatures of 65 degrees Fahrenheit. During this single site visit we observed the following site conditions. Findings: 1. The subject parcel is in the city of Federal Way Washington county of King. The site generally slopes to the West and North. The site is generally sloped 6% -10% along the western property boundary. The property has gradual sloping terraces to the Western and Northern property boundary. The properties to the north and south have been elevated. A storm drain ditch is located near south side of 373rd Street front of the property. Overall size of the parcel property is approximately 149,410 This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 total square feet or 4.10 acres parcel of land that is well drained with no standing water or evidence of hydrophytic characteristics. The site is largely grazed and has an existing single-family residence that was constructed in the year of 1938 situated along the south west side of the parcel property. The vegetative strata dominate species is as follows: Top canopy trees along the south sides of the property are - Crab Apple (Malus "Robinson") The general property parcel middle and lower strata are primarily common daisies (Bellis perennis) grass (Poaceae) reed canary grass (Phalaris arundinacea) invasive species of Himalayan blackberry (Rubus armeniacus) parallel the south and east sides of the parcel. 2. Soil conditions were well drained pebbly, gravely, sandy loam soils. There was no standing water / aquatic habitat or wetland type vegetation across any strata observed in the site determination walk. Drainage swales exist along the east side parcel but were dry & chocked out with non-wetland type vegetation grass and weeds. Due Diligence: Washington State Fish & Game National Wetland Inventory King County Assessor’s office parcel records CAO critical area ordnance. Records Review: Records review of the subject property shows that the subject property is not listed in the National Wetlands Inventory List or the King County Critical Areas Ordnance List. However, there is an identified fresh water forested shrub wetland to the west and a creek identified as Hylebos creek located to the west of the subject property. Hylebos Creek is a stream located in the U.S. state of Washington near Tacoma and emptying into Commencement Bay, part of Puget Sound. It flows through southern King County and northern Pierce County, through the cities of Tacoma, Federal Way, Milton, and Fife, as well as the Puyallup Indian Reservation that drains into Puget Sound Commencement Bay. The subject property north west corner parcel is greater than 350’ feet from Hylebos creek to the west measuring approximately 600 liner feet. The subject property is This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 approximately 300 feet or greater than that to the edge of the identified wetland to the west. See the below photograph. Conclusion: This entire subject property parcel contains no characteristics of a wetland based on the specific vegetation, soil, hydrology and habitat requirements defined in the “Routine Determination” method outlined in the Washington State Wetlands Identification and Delineation Manual, Ecology Publication #96-94; and the Wetland Rating System for Western Washington, Revised 2010, Ecology Publication #04-06-025; and the Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region U.S. Army Corps of Engineers May 2010. User Reliance: BAI’s work was performed consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions. Information provided to BAI by client representatives and site contacts has been accepted in good faith and is assumed to be accurate. BAI’s findings are based on observations and data collected at one point in time. Assessment results are based upon conditions and operations at the time of the site visit. A change in any of these factors may alter the findings and conclusions expressed by BAI. A site walkthrough, by nature, is limited in its ability to fully assess potential environmental liabilities associated with any real estate transaction or construction activity. Further This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 investigation would be required to identify potential environmental liabilities, which may be present at the site, but were beyond the scope of this environmental site assessment. State and federal laws and regulations referenced in this report are provided for information purpose and should not be construed as legal opinion or recommendation. Use and distribution of this document is limited to BAI’s client and those parties identified for distribution by the client. This report is the product of BAI, which has been produced in accordance with a specific contract between BAI and its Client who is represented by the party to whom this report is addressed. This report is the work product for the sole use and benefit of the contracting Client. It does not create any right or benefits to parties other than the Client and BAI except such other rights as are specifically called for herein. BAI consents to the release of this report to third parties at the discretion of the Client. However, any use of or reliance upon this information by a party other the Client shall be solely at the risk of such third party and without legal recourse against BAI, its affiliates, associates, employees, officers, or directors, regardless of whether the action in which recovery of the damages sought is based upon contract, tort (including the sole, concurrent or other negligence and strict liability of BAI, statute or otherwise). This report shall not be used or relied upon by a party which does not agree to be bound by the above statement. This report is valid as of the date shown and BAI shall not be held responsible for subsequent changes in Physical/Chemical/Environmental Conditions and/or legislation over which BAI has no control. Qualifications: We declare that, to the best of our professional knowledge and belief, we meet the definition of Environmental professional as defined in subsection 312.10 of 40 CFR 312. We have the specific qualifications based on education, training, and experience to assess a property of the nature, history, and setting of the subject property. We have developed and performed the all appropriate inquiries, wetlands, and other environmental site assessments in conformance with the standards and practices set forth in 40 CER Part 312 This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 Sincerely, Scott Barry Scott Barry-Wetland Biologist CEC/CEC # 77246 This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 Appendix “A” Addendum Photographs. Wetland Determination Data Form. BAI Client Consultant Contract. This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 View Looking Northwest Lowest Point Subject Property This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 Photo Showing Dominate Lower Strata This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 East Drainage Swale View Looking North This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 Data Point DP-1 & DP-2 Sand Loam Soil This report has been produced in accordance with our signed contract and is subject to the terms and conditions agreed upon therein. All printed comments and the opinions expressed herein are those of the inspection company. BAI Services Inc. Project # 2020/326306 Data Point DP-1 & DP-2 Sand Loam Soil US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys, and Coast Region VEGETATION – Use scientific names of plants Tree Stratum (Plot size: 100) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet: 1. Crab Apple. (Malus "Robinson" 10 yes UPL Number of Dominant Species That Are OBL, FACW, or FAC: 3 (A) 2. 3. Total Number of Dominant Species Across All Strata: 3 (B) 4. 50% = , 20% = 80 = Total Cover Percent of Dominant Species That Are OBL, FACW, or FAC: 100 (A/B) Sapling/Shrub Stratum (Plot size: 100) 1. Himalayan blackberry (Rubus armeniacus) 20 FAC Prevalence Index worksheet: 2. common daisies (Bellis perennis) 80 FAC Total % Cover of: Multiply by: 3. OBL species x1 = 4. FACW species x2 = 5. FAC species x3 = 50% = , 20% = 20 20 = Total Cover FACU species x4 = Herb Stratum (Plot size: 100) UPL species 80 x5 = 400 1. Grass (Poaceae) 10 UPL Column Totals: 80 (A) 400 (B) 2. Reed canary grass Phalaris arundinacea( 20 FAC Prevalence Index = B/A = 480 3. Hydrophytic Vegetation Indicators: 4. 1 – Rapid Test for Hydrophytic Vegetation 5. 2 - Dominance Test is >50% 6. 3 - Prevalence Index is <3.01 7. 4 - Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 8. 9. 5 - Wetland Non-Vascular Plants1 10. Problematic Hydrophytic Vegetation1 (Explain) 11. 1Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic. 50% = , 20% = 10 = Total Cover Woody Vine Stratum (Plot size: ) 1. Hydrophytic Vegetation Present? Yes No 2. 50% = , 20% = = Total Cover % Bare Ground in Herb Stratum 5 Remarks: Project Site: 37325 8th Ave. S. Federal Way WA. 98003 City/County: Federal Way/King Sampling Date: June 30/2020 Applicant/Owner: Eunhee Kim State: WA Sampling Point: DP-1 Investigator(s): Scott Barry Section, Township, Range: N/A Landform (hillslope, terrace, etc.): Hillslope Terrace Local relief (concave, convex, none): none Slope (%): 8 Subregion (LRR): NW Lat: 47 16 01 52 Long: 122 19 34 47 Datum: 0 Soil Map Unit Name: 4890000011 NWI classification: AASHTO Are climatic / hydrologic conditions on the site typical for this time of year? Yes No (If no, explain in Remarks.) Are Vegetation , Soil , or Hydrology , significantly disturbed? Are “Normal Circumstances” present? Yes No Are Vegetation , Soil , or Hydrology , naturally problematic? (If needed, explain any answers in Remarks.) SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes No Is the Sampled Area within a Wetland? Yes No Hydric Soil Present? Yes No Wetland Hydrology Present? Yes No Remarks: No Hydrophytic present US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 SOIL Sampling Point: DP-1 Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 18 10YR4/3 100 10YR4/3 100 C M Sandy Loam Matrix 1Type: C= Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains. 2Location: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: Histosol (A1) Sandy Redox (S5) 2 cm Muck (A10) Histic Epipedon (A2) Stripped Matrix (S6) Red Parent Material (TF2) Black Histic (A3) Loamy Mucky Mineral (F1) (except MLRA 1) Very Shallow Dark Surface (TF12) Hydrogen Sulfide (A4) Loamy Gleyed Matrix (F2) Other (Explain in Remarks) Depleted Below Dark Surface (A11) Depleted Matrix (F3) 3Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic. Thick Dark Surface (A12) Redox Dark Surface (F6) Sandy Mucky Mineral (S1) Depleted Dark Surface (F7) Sandy Gleyed Matrix (S4) Redox Depressions (F8) Restrictive Layer (if present): Hydric Soils Present? Yes No Type: Depth (inches): Remarks: HYDROLOGY Wetland Hydrology Indicators: Primary Indicators (minimum of one required; check all that apply) Secondary Indicators (2 or more required) Surface Water (A1) Water-Stained Leaves (B9) Water-Stained Leaves (B9) High Water Table (A2) (except MLRA 1, 2, 4A, and 4B) (MLRA 1, 2, 4A, and 4B) Saturation (A3) Salt Crust (B11) Drainage Patterns (B10) Water Marks (B1) Aquatic Invertebrates (B13) Dry-Season Water Table (C2) Sediment Deposits (B2) Hydrogen Sulfide Odor (C1) Saturation Visible on Aerial Imagery (C9) Drift Deposits (B3) Oxidized Rhizospheres along Living Roots (C3) Geomorphic Position (D2) Algal Mat or Crust (B4) Presence of Reduced Iron (C4) Shallow Aquitard (D3) Iron Deposits (B5) Recent Iron Reduction in Tilled Soils (C6) FAC-Neutral Test (D5) Surface Soil Cracks (B6) Stunted or Stresses Plants (D1) (LRR A) Raised Ant Mounds (D6) (LRR A) Inundation Visible on Aerial Imagery (B7) Other (Explain in Remarks) Frost-Heave Hummocks (D7) Sparsely Vegetated Concave Surface (B8) Field Observations: Surface Water Present? Yes No Depth (inches): Wetland Hydrology Present? Yes No Water Table Present? Yes No Depth (inches): Saturation Present? (includes capillary fringe) Yes No Depth (inches): Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: None Remarks: No Hydrology Indicators Project Site: 37325 8th Ave. S. Federal Way WA. 98003 NATURAL DRAINAGE SYSTEM FUNCTIONS The Site consists of Single Threshold Discharge Areas (TDA) on Figure 7. Runoff from TDA East appears to converge at a low point at the northwest corner of the Site. Field investigation would indicate that this runoff infiltrates and never leaves the Site by the existing side ditch at the 373rd Street; field insitu testing would appear to confirm this observation. Based on the Soil Report, American Geoservices, Septic Feasibility Report, Project No: 0177-WA19 dated September 2019 said: “Soils profile: Medium sands, loamy coarse sands, loamy medium sands, (Soil Type 3) in upper 2.5’-3.0’ followed by gravelly to very gravelly coarse sands (Soil Type 1) extending to the maximum explored depth of 8 feet. Groundwater: Not encountered; Soil mottling present within 2.5-3.0 feet of the ground surface. Design Long Term Acceptance Rate (LTAR) or Loading Rate for Residential Effluent Using Gravity or Pressure Distribution: 0.80. Conclusion: Site is suitable for on-site waste treatment as per the most current King County, WA, On-site Sewage Regulations, provided adequate setbacks are provided for all the components of on-site sewage systems.” A review of the soil is attached at King County Health Department approval Letter. In conclusion, all upstream runoff of the Site and can be considered negligible for the scope of this project due to no foreseen negative impacts being anticipated from the upstream areas at the ridge of hill. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 5 of 53 SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 – Discharge at the Natural Location: All Site runoff will infiltrate, no discharge is anticipated in the developed area. Discharging to the natural drainage location at the existing side ditch of 373rd Street helps to prevent adverse impacts to downstream properties caused by developing 3 lots, and to discharge in a manner that does not significantly impact downhill properties or drainage systems. The proposed discharge from the site will mimic the existing drainage conditions. The runoff will be collected and conveyed to the existing gravel ditch which will be utilized to infiltrate the stormwater into the soils or new storm drain pipe installed by widening of road dedicated. • C.R. #2 – Offsite Analysis: An offsite analysis is included in Section III. The Analysis describes the Site’s runoff pattern in detail. • C.R. #3 – Flow Control: Flow control will be provided in order to protect downstream properties and resources from increases in peak, duration and volume of runoff generated by new development. The gravel trench/or storm drainage pipe system will provide flow control for the project site after road dedicated to the City constructed. • C.R. #4 – Conveyance System: New pipe systems and ditches/channels are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. All conveyance system elements for the proposed project will be analyzed, designed, and constructed to provide a minimum level of protection against overtopping, flooding, erosion, and structural failure. The proposed conveyance system consists of 8” pipe system which will convey stormwater from the impervious areas to the on-site infiltration trench but this conveyance system will be a part of road expansion of the road dedicated to the City. • C.R. #5 – Erosion and Sediment Control: The Project do not needs to provide any minimum ESC measures. But in order to help minimize the erosion and transport of sediment, several erosion control measures as detailed in the King County Erosion and Sediment Control (ESC) Standards adopted as Appendix D of the 2016 KCSWM will be utilized. • C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City/County. An Operation and Maintenance 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 6 of 53 Manual will be included in Section X at the time of construction plan preparation. All privately maintained drainage facilities shall be maintained as specified in Appendix A of the 2016 KCSWM. A copy of the Operation and Maintenance Manual shall be retained on site and will be transferred with property to new owner. • C.R. #7 – Financial Guarantees and Liability: Prior to commencing construction of each site development, the Applicant must post a drainage facilities restoration and Site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. • C.R. #8 – Water Quality: It is exemption per Condition 1: Surface Area Exemption per less than 5,000 sf of new plus replaced PGIS ( pollution-generating impervious surface) and less than ¾ acre of new PGIS that is not fully dispersed will be added. • C.R. #9 – Flow Control BMP’s: Any impervious surface served by an infiltration facility designed in accordance with the flow control facility requirement (Section 1.2.3.1), the facility implementation requirements (Section 1.2.3.2), and the design criteria for infiltration facilities (Section 5.2) is exempt from the flow control BMPs requirement. (Manual, Section 1.2.9.1(A)) • S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 – Floodplain/Floodway Delineation: The Project parcel is not within a 100year floodplain defined by any of FEMA’s floodplain insurance rate maps. No other specific data exists establishing the base (100-year) flood elevation through the Site. • S.R. #3 – Flood Protection Facilities: Not applicable for this Project. • S.R. #4 – Source Control: Not applicable for this Project. • S.R. #5 – Oil Control: Not applicable for this Project. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 7 of 53 SECTION III OFF-SITE ANALYSIS An offsite Level One Downstream Analysis was prepared by Eui Kim Professional Engineer and is included in this Section. TASK 1: DEFINE AND MAP THE STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2016 King County Surface Water Design Manual (Manual). The Site is located at 37325 8th Ave S Federal Way, WA. See Figures 2 through 7 for maps of the study area. TASK 2: RESOURCE REVIEW • Adopted Basin Plans: None at this time. • Floodplain/Floodway Map and FEMA: No floodplains exist on site, See Figure 4. • Other Offsite Analysis Reports: See Figure 1B The Green/Duwamish River Watershed Map • Sensitive Areas King county iMaps: no Sensitive Area, See Figures 4. • Figure 4 Streams and 100-Year Floodplains and Floodway: There are no floodplains onsite. A stream is located within 1 mile of the site along the downstream path. • Figure 4 Wetlands: King County has not identified any wetlands in the immediate vicinity of the project site, however one wetland is found within one mile over the highway of the site. • Figure 4 Erosion Hazard: There are no mapped Erosion Hazard Areas onsite,. • Figure 4 Landslide Hazard: There is one area mapped • Figure 4 Seismic Hazard: There are no mapped Seismic Hazard Areas on the project site. • Road Drainage Problems: None noted. • USDA King County Soils Survey: See Figure 3. • Wetlands Inventory: Vol. 1 East (1990) – The wetland inventory revealed no additional wetlands within the downstream path. • Migrating River Studies: None are applicable to the site. • Washington State Department of Ecology's latest published Clean Water Act Section 303d list of polluted waters: None listed along the ¼ mile downstream path. • King County Designated Water Quality Problems: None at this time. • Adopted Stormwater Compliance Plans: None applicable to this site. • Basin Reconnaissance Summary Reports: No reports available for this area. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 8 of 53 TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA In evaluating the upstream area, we reviewed the King County iMap, a field topographic survey, and area topography from King County iMap. Negligible runoff may enter from 8th Ave S but will not impact the project given the proposed road and drainage improvements. Otherwise, runoff does not enter the Site from any other direction. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTION Runoff from TDA on Figure 7 appears to converge at low point at the northwest corner with no apparent outlet. Field observation of the vegetation in this area indicates that water does not pond and would therefore appear to infiltrate. This observation was confirmed with in-situ infiltration testing that confirmed that runoff does indeed infiltrate. Should the soil ever saturate and the area overflow, runoff would head west side ditch near 373rd Street. Runoff from TDA sheet flows to the west through ditch at 373rd Street to the stream at the lower area. TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in Figure 7, the Downstream Map. The drainage area is located within the Green/Duwamish River Watershed area. TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS The project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY (PART A) WWHM was used to model the peak runoff from the Site. Per Table 3.2.2.b of the Manual the soil type is modeled as “Type C” for the gravelly silty sandy SM/GM classification as shown in Table 1 on page 26, Soils Classification. The entire Site is modeled as “Pasture.” Results of the WWHM analysis are included in this section. Because the project is proposing full infiltration, the entire Site was modeled as a single basin, despite the single threshold discharge areas in the predeveloped condition. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 9 of 53 TASK 4.1: Flow Control and Water Quality Design This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2016 King County Surface Water Design Manual (Manual). The Site is located at 37325 8th Ave S Federal Way, WA. The proposed analysis parameters are as follows: WWHM Methodology Seatac Rainfall region with a precipitation factor of 1.0 Type “C” soil is used in WWHM model. Total area = 154,487 SF = 3.546 acre Approximately 4,500 s.f. of on-site hard surface area will be added. 4.2 Existing Basin Summary Total pervious = 3.547 acres (154,487 sf) Existing road = 0.0376 acres (1,600 sf) Total area Included in the Analysis = 3.547 acres (154,487 sf) Refer to the Existing Basin Map attached later in this section for more details. 4.3 Developed Basin Summary Total pervious: = 3.547 acres (154,487 sf) Roof = 0.11 acres (4,800 sf) Existing Road = 0.0376 acres (1,600 sf) Driveway and walkway incl road dedicated to the City = 0.295 acres (12,858 sf) Total area = 3.547 acres (154,487 sf) On Site Impervious Areas = 0.435 acre (18,958 sf ) = 12.3% of total area Refer to the Developed Basin Map attached later in this section for more details. The infiltration trench has been sized 350’ (L) X 3.1’ (W) X 3’ (D),at the side of 373rd Street collecting all storm drainage from the project site. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 10 of 53 4.4 Water Quality Water quality is exempt because the total PGIS is only 4,500 sf, and is less than the threshold limit of 5,000 sf. SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN TASK 5.1: CONVEYANCE SYSTEM ANALYSIS AND DESIGN The conveyance system mainly consists of 8” PVC at 8% min Storm Drainage for the site. The peak runoff calculation using Rational Method are as follow: Storm Drain Runoff From KSCSDM Figure 3.2.1.A-D aR bR Tc Pr iR IR 2-yr 1.58 0.58 0.73 1.6 1.90 3.03 10-yr 2.44 0.64 0.73 2.4 2.98 7.16 25-yr 2.66 0.65 0.73 2.7 3.26 8.81 100-yr 2.61 0.63 0.73 3.2 3.18 10.18 IR=(Pr)(iR) (Peak Rainfalll Intensity) iR=(aR)(Tc)^-(bR) (Unit Peak Rainfall Intensity Factor) Storm Drainage System for Area: Peak Runoff C Roof Area (A) IR Q25 = 3.01 cfs 0.2 3.547 2.248 Conveyance Pipe Analysis: See Appendix A 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 11 of 53 Storm drain pipe Tightline SIZE (IN) SLOPE (FT/FT) MANNING COEFFICEN T, n 25-yr Peak Flow Rate for Roofs Area THREE 8” CIP PIPE 8’’ 0.1 0.012 30fps Using 8” CIP Pipe for each storm drain trench, the capacity is sufficient to handle 25 year peak flow rate. We strongly recommend the City to consider adopt this size as it is ultimately protection of the site from flooding during 25-year storm event 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 12 of 53 FIGURE 1: SITE LOCATION MAPREFERENCE: GOOGLE MAPS USGS TOPOGRAPHIC MAPS SITE LOCATION SITE LOCATION 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 13 of 53 FIGURE 1A .PI E R C E C O . FEDERAL WA Y KI N G C O . TUKWILA RENTON SEATTLE SEATTLE BURIEN NORMANDY PARK SEATAC FEDERAL WAY ALGONA AUBURN KENT DES MOINES BLACK DIAMOND ENUMCLAW COVINGTON MAPLE VALLE YMauryIsland Island Vashon 509 900 167 167 515 405 99 99 5 5 164 18 516 169 Elliott Bay G R E E N RIVERPugetSoundCo v i n gton CrN ew a u k u m CreekJenkinsCreekSoosCreekMillCreekB l ackRi verHammCrDuwamis h R iv e r GREEN RIVER Howard Hanson Reservoir Lake Sawyer Howard Hanson Dam Tacoma Headworks Watershed Boundary Basin Boundary River Major Road Open Water 02 4 6 Miles May 2006 N Department of Natural Resources and Parks Water and Land Resources Division The Green/Duwamish River Watershed Produced by: Department of Natural Resources and Parks, WLRD, GIS, Visual Communications & Web Unit File Name: 0605greenbase sk Lower Green River Subwatershed Middle Green River Subwatershed Upper Green River Subwatershed Duwamish Estuary Subwatershed 12/16/2019Eui Kim, Professional EngineerGraceland Short Subdivision Page 14 of 53FIGURE 1B 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 15 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 16 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 17 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 18 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 19 of 53 FIGURE 3: GEOLOGIC MAP REFERENCE U.S. GEOLOGIC SURVEY SITE LOCATION LEGEND 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 20 of 53 King County iMAP, Elevation, environmental sensitive area, flood info, landslides, stormwater services, wetland 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 21 of 53 FIGURE 4 12/16/2019Eui Kim, Professional EngineerGraceland Short Subdivision Page 22 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 23 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 24 of 53 FIGURE 5 Total area of Predevelopment: Lot #1: 3.547 acre Total: 3.547 acre Roof Area: 1680 sf (0.04 acre) Front Road: 150ft x 10 ft=1500 sf (0.034 acre) total area: 3.547 acre Total area of development: Lot #1: 36,608.37 sf 0.84 acre Lot #2: 35,008.22 sf 0.804 acre Lot #3: 35,010.28 sf 0.804 acre Lot #4: 35,002.41 sf 0.804 Total: 141,629.28 sf, 3.252 Acre New Road dedicated to the city: 0.295 acres Roof : 2,000 sf x 4 units=8000sf (0.18 acre) total area: 3.547 acre 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 25 of 53 FIGURE 6 1 2 3 4 5SCALE : drainage basins & subbasins1"=30'-0"A-8TH AVE S S 372ND STS 373RD STEL 120EL 100 12/16/2019Eui Kim, Professional EngineerGraceland Short Subdivision Page 26 of 53FIGURE 7 TP1 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-6” Topsoil 6”-30” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium to fine sands 4 0.6 No groundwater table 30 30”-84” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 84”-96” Cemented silty sandy gravel (GM) Gravelly to very gravelly sands, cemented 1 Limiting layer No groundwater table TP2 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-6” Topsoil 6”-40” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium to fine sands 4 0.6 No groundwater table 33 40”-84” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 27 of 53 TABLE 1 TP3 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-8” Topsoil 8”-40” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands 4 0.6 No groundwater table 30 40”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table TP4 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-8” Topsoil 8”-36” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands 4 0.6 No groundwater table 33 36”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 28 of 53 TP5 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-12” Topsoil 12”-36” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands; Occasional roots and organics 4 0.6 No groundwater table 36 36”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table TP6 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-10” Topsoil 10”-36” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands; some clay 4 0.6 No groundwater table 36 36”-72” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 72”-96” Cemented silty sandy gravel (GM) Gravelly to very gravelly sands, cemented Limiting layer No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 29 of 53 TP7 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-12” Topsoil 12”-36” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands, trace roots and organics 4 0.6 No groundwater table 30 36”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table TP8 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-12” Topsoil 12”-36” Gravelly silty sand (SM/GM) Medium sands, loamy coarse sands, loamy medium sands, trace roots and organics 4 0.6 No groundwater table 27 36”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 30 of 53 TP9 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-8” Topsoil 8”-30” FILL: Silty gravelly sand, some trash, some organics (SM) Medium sands, loamy coarse sands, loamy medium sands 4 0.6 No groundwater table 36 30”-96” Silty sandy gravel (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table TP10 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-8” Topsoil 8”-60” Silty gravelly sand with some cobbles (SM) Medium sands, loamy coarse sands, loamy medium sands 4 0.6 No groundwater table 48 60”-96” Silty sandy gravel, some cobbles, some cementation noted (GM) Gravelly to very gravelly silty sands 3 0.8 No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 31 of 53 TP11 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-8” Topsoil 8”-60” Silty gravelly sand with some cobbles (SM) Medium sands, loamy coarse sands, loamy medium sands 4 0.8 No groundwater table 50 60”-96” Silty sandy grave, some cobbles, minor cementation noted (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table TP12 Depth (Inches) USCS Classification Soil Textural Classification Soil Type Loading Rate (gal/sq.ft./day) Ground water Table Depth to Soil Mottling (Inches) 0”-12” Topsoil 12”-60” Silty gravelly sand with some cobbles (SM) Medium sands, loamy coarse sands, loamy medium sands 4 0.6 No groundwater table 50 60”-96” Silty sandy gravel, some cobbles, some cementation noted (GM) Gravelly to very gravelly sands 3 0.8 No groundwater table 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 32 of 53 Rational Runoff Method of Predevelpoment Calulation per King County surface Water Design Manual April 24, 2016 Area: A1: Area of residential of 1 lots: 3.547 AC Area A2: New Road 0. AC ≔A1 3.547 AC AC≔A2 0 ≔At =+A1 A2 3.547 Descriptive ofFlowpath Segments for Tc L1=383ft, 125 ft and 90 ft 9% slope s1= 0.09 meadow kg = 2.5 ≔L1 383 ≔s1 0.09 ≔kR 2.5 ≔T1 =―――――L1 ⋅60 ⎛⎝⋅kR ‾‾s1 ⎞⎠ 8.511 min. ≔Tc =T1 8.511 Coefficients for the rational Method Equation per Table 3.2.1.B 25 years aR=2.66 bR=0.65 ≔aR 2.66 ≔bR 0.65 ≔i25 =⋅aR Tc ⎛⎝-bR⎞⎠0.661 Compute: Composite Runoff Coefficient Cc A1: C1 from Table 3.2.1 A (page 3-15) 1 units per 3.54 AC 0.4 DU/GA, C=0.2 ≔C1 0.2 A2: Road, Pavement and roof, C=0.9 Created with PTC Mathcad Express. See www.mathcad.com for more information. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 33 of 53 APPENDIX A ≔C1 0.2 A2: Road, Pavement and roof, C=0.9 ≔C2 0.9 ≔Cc =―――――― ⎛⎝+⋅C1 A1 ⋅C2 A2⎞⎠ At 0.2 PR Total precipitation at the Site for 24 hour duration storm event for given return frequency per Fig 3.2.1 A through D ≔PR 3.4 ≔I25 =⋅PR i25 2.248 Peak Runoff Rate: ≔Q25 =⋅⋅Cc I25 At 1.595 cfs Created with PTC Mathcad Express. See www.mathcad.com for more information. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 34 of 53 Rational Runoff Method of Post-develpoment Area: A1: Area of residential of 4 lots: 3.252 AC Area A2: New Road 0.295 AC ≔A1 3.252 AC ≔A2 0.295 AC ≔At =+A1 A2 3.547 Descriptive ofFlowpath Segments for Tc L1=383ft, 125 ft and 90 ft 9% slope s1= 0.09 meadow kg = 2.5 ≔L1 383 ≔s1 0.09 ≔kR 2.5 ≔T1 =―――――L1 ⋅60 ⎛⎝⋅kR ‾‾s1 ⎞⎠ 8.511 min. ≔Tc =T1 8.511 Coefficients for the rational Method Equation per Table 3.2.1.B 25 years aR=2.66 bR=0.65 ≔aR 2.66 ≔bR 0.65 ≔i25 =⋅aR Tc ⎛⎝-bR⎞⎠0.661 Compute: Composite Runoff Coefficient Cc A1: C1 from Table 3.2.1 A (page 3-15) 1 units per 35,000 sf 1.25 DU/GA, use 1.5 DU/GA, C=0.33 ≔C1 0.33 A2: Road, Pavement and roof, C=0.9 Created with PTC Mathcad Express. See www.mathcad.com for more information. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 35 of 53 ≔C1 0.33 A2: Road, Pavement and roof, C=0.9 ≔C2 0.9 ≔Cc =―――――― ⎛⎝+⋅C1 A1 ⋅C2 A2⎞⎠ At 0.377 PR Total precipitation at the Site for 24 hour duration storm event for given return frequency per Fig 3.2.1 A through D ≔PR 3.4 ≔I25 =⋅PR i25 2.248 Peak Runoff Rate: ≔Q25 =⋅⋅Cc I25 At 3.01 cfs Per Figure 4.2.1.F Stormwater pipe 8" CIP Pipe will be installed after City Street improvements. Created with PTC Mathcad Express. See www.mathcad.com for more information. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 36 of 53 Created with PTC Mathcad Express. See www.mathcad.com for more information. 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 37 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 38 of 53 2.05 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 39 of 53 FIGURE A1 3.0 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 40 of 53 3.4 4.1 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 41 of 53 WWHM2012 PROJECT REPORT 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 42 of 53 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 43 of 53 default[4]12/15/2019 4:08:40 PM Page 2 General Model Information Project Name: default[4] Site Name: Kim 37325 Site Address: 37325 8th Ave S City:Federal Way Report Date: 12/15/2019 Gage:Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 44 of 53 default[4]12/15/2019 4:08:40 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Pasture, Mod 3.546 Pervious Total 3.546 Impervious Land Use acre ROADS FLAT 0.04 ROOF TOPS FLAT 0.04 Impervious Total 0.08 Basin Total 3.626 Element Flows To: Surface Interflow Groundwater 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 45 of 53 default[4]12/15/2019 4:08:40 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Pasture, Mod 3.252 Pervious Total 3.252 Impervious Land Use acre ROADS MOD 0.295 ROOF TOPS FLAT 0.11 Impervious Total 0.405 Basin Total 3.657 Element Flows To: Surface Interflow Groundwater 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 46 of 53 default[4]12/15/2019 4:08:40 PM Page 9 Appendix Predeveloped Schematic 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 47 of 53 default[4]12/15/2019 4:08:40 PM Page 10 Mitigated Schematic 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 48 of 53 default[4]12/15/2019 4:08:41 PM Page 12 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 default[4].wdm MESSU 25 Mitdefault[4].MES 27 Mitdefault[4].L61 28 Mitdefault[4].L62 END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 14 IMPLND 2 IMPLND 4 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 14 C, Pasture, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 14 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 14 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 49 of 53 default[4]12/15/2019 4:08:41 PM Page 13 14 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 14 0 4.5 0.06 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 14 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 14 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 14 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 2 ROADS/MOD 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 2 0 0 1 0 0 0 4 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 2 0 0 4 0 0 0 1 9 4 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 2 0 0 0 0 0 4 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 2 400 0.05 0.1 0.08 4 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 50 of 53 default[4]12/15/2019 4:08:41 PM Page 14 2 0 0 4 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 2 0 0 4 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 51 of 53 default[4]12/15/2019 4:08:41 PM Page 15 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** END MASS-LINK END RUN 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 52 of 53 default[4]12/15/2019 4:08:41 PM Page 18 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. 2005-2019; 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 12/16/2019 Eui Kim, Professional Engineer Graceland Short Subdivision Page 53 of 53