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04139M Prelim TIR
Core Design, Inc. MERLINO SHORT PLAT i Merlino Short Plat Table of Contents 1 PROJECT OVERVIEW ................................................................................................................ 1 Figure 1-1: Vicinity Map ........................................................................................................ 2 2 CONDITIONS AND REQUIREMENTS SUMMARY ................................................................ 3 2.1 Core Requirements ................................................................................................................ 3 2.1.1 Core Requirement #1: Discharge at the Natural Location ............................................ 3 2.1.2 Core Requirement #2: Offsite Analysis ......................................................................... 3 2.1.3 Core Requirement #3: Flow Control ............................................................................. 3 2.1.4 Core Requirement #4: Conveyance System .................................................................. 3 2.1.5 Core Requirements #5: Erosion and Sediment Control ................................................. 3 2.1.6 Core Requirement #6: Maintenance and Operations ..................................................... 3 2.1.7 Core Requirement #7: Financial Guarantees and Liability ............................................ 3 2.1.8 Core Requirement #8: Water Quality ............................................................................ 3 2.2 Special Requirement #1: Other Adopted Area-Specific Requirements ................................ 4 2.2.1 Critical Drainage Areas ................................................................................................. 4 2.2.2 Master Drainage Plan .................................................................................................... 4 2.2.3 Basin Plans..................................................................................................................... 4 2.2.4 Salmon Conservation Plans (SCPs) ............................................................................... 4 2.2.5 Stormwater Compliance Plans (SWCPs) ....................................................................... 4 2.2.6 Lake Management Plans (LMPs) .................................................................................. 4 2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) ........................................................... 4 2.2.8 Shared Facility Drainage Plans (SFDPs) ....................................................................... 4 2.3 Special Requirement #2: Floodplain / Floodway Delineation .............................................. 4 2.4 Special Requirement #3: Flood Protection Facilities ............................................................ 4 2.5 Special Requirement #4: Source Controls ............................................................................ 4 2.6 Special Requirement #5: Oil Control .................................................................................... 4 3 OFFSITE ANALYSIS .................................................................................................................. 5 3.1 Study Area Definition and Maps ........................................................................................... 5 3.2 Resource Review ................................................................................................................... 5 Basin Reconnaissance Summary Reports ............................................................................... 5 FEMA Maps ........................................................................................................................... 5 Sensitive Areas Folio .............................................................................................................. 5 City of Renton Soil Survey ..................................................................................................... 5 Downstream Drainage Complaints ......................................................................................... 5 Core Design, Inc. MERLINO SHORT PLAT ii 3.3 Field Investigation ................................................................................................................. 5 Upstream Tributary Area ........................................................................................................ 5 Level 1 Downstream Analysis ................................................................................................ 6 Field Investigation .............................................................................................................. 6 3.4 Mitigation of Existing and Potential Problems ..................................................................... 6 Downstream Drainage Problems Requiring Special Attention .............................................. 6 Department of Ecology 303d Listings .................................................................................... 6 Drainage Adjustments ............................................................................................................ 6 4 FLOW CONTROL AND WATER QUALITY DESIGN ............................................................. 7 4.1 Existing Site Hydrology ........................................................................................................ 7 4.2 Developed Site Hydrology .................................................................................................... 8 Figure 4-1: Existing Conditions Basin Exhibit ...................................................................... 9 Figure 4-2: Developed Conditions Exhibit .......................................................................... 10 4.3 Performance Standards........................................................................................................ 11 Flow Control: Duration Standard Matching Forested Site Conditions ................................ 11 Conveyance Capacity ........................................................................................................... 11 Water Quality: Basic Water Quality Menu .......................................................................... 11 4.4 Flow Control System ......................................................................................................... 11 Calculation of Lot Impervious Area ..................................................................................... 11 Flow Control BMPs/Individual Lot BMPs ........................................................................... 12 Bypass Area .......................................................................................................................... 13 Detention Pond Modeling ..................................................................................................... 14 KCRTS Vault Calculation ................................................................................................ 14 4.5 Water Quality Calculations ................................................................................................. 15 Basic Wetvault ...................................................................................................................... 15 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN ........................................................... 17 6 SPECIAL REPORTS AND STUDIES ....................................................................................... 19 7 OTHER PERMITS ...................................................................................................................... 21 8 ESC ANALYSIS AND DESIGN ................................................................................................ 23 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .................................................................................................................................. 25 9.1 Bond Quantities ................................................................................................................... 25 9.2 Facility Summaries ............................................................................................................. 25 9.3 Declaration of Covenant ..................................................................................................... 25 10 OPERATIONS AND MAINTENANCE .................................................................................. 27 Core Design, Inc. MERLINO SHORT PLAT iii Appendix A – Parcel & Basin Information King County Parcel Report (2225069082) King County Parcel Report (2225069083) Appendix B – Resource Review & Off-site Analysis Documentation FEMA Map (53033C0977F) City of Renton Aquifer Protection Zones City of Renton Groundwater Protection Areas City of Renton Sensitive Area Maps City of Renton Soil Survey Drainage Complaints Exhibit Downstream Drainage Map Appendix C – Pond Sizing City of Renton Flow Control Map Rainfall Region & Regional Scale Factor (Figure 3.2.2.A) KCRTS Hydrologic Soils Group Table (Table 3.2.2.B) Mean Annual Storm Precipitation (Figure 6.4.1.A) KCRTS Input Vault Summary Peaks Analysis Durations Analysis Appendix D – Conveyance Calculations To be provided at Final Engineering Core Design, Inc. MERLINO SHORT PLAT iv Core Design, Inc. MERLINO SHORT PLAT Page 1 1 PROJECT OVERVIEW The project site is located at Cedar Avenue S and SE 7th Street in the City of Renton, King County. Specifically the project is in the northwest quarter of Section 20, Township 23 North, Range 5 East, W.M. The site is bordered by the Cedar Crest Condominiums to the north, single- family residential homes on the east, the Puget Sound Energy transmission line to the south and I- 405 to the west. The King County tax parcel ID numbers for the two parcels involved in the project are shown in Table 1 below (refer to the King County Parcel Reports included in Appendix A). Table 1: Parcel Information KC Parcel # Parcel Area (SF) 0007200194 38,569 2023059085 122,374 The project site is approximately 1.50 acres in size and is currently covered in grass. Cedar Avenue S drains south though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I-405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch flowing south on the west boundary of the site. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch on the west boundary. The site does not receive any upstream flow. The site was mass graded as part of the I-405 project, so there will be no clearing and minimal grading to construct seven single-family lots, the stormwater vault and the associated utilities. Half-street frontage improvements on Cedar Avenue S will be completed to provide 13.5 feet of pavement from the right of way centerline, curb and gutter an 8-foot planter and a 5-foot sidewalk. See Figure 1-1: Vicinity Map, provided below. The project will be designed using the guidelines and requirements established in the 2009 King County Surface Water Design Manual (2009 KCSWDM) and City of Renton Amendments to the King County Surface Water Manual (COR Amendments) The project is required to apply a Flow Duration Standard to Forested Conditions and Basic Water Quality. The drainage analysis for detention sizing was modeled using the King County Runoff Time Series (KCRTS) software. The water quality facility sizing calculations are based on methods described in Chapter 6 of the 2009 KCSWDM. The conveyance calculations will be completed using the Rational Method and the King County Backwater program. One combined detention and water quality treatment vault will be located at the south end of Cedar Avenue S in the cul-de-sac. The treated and detained flows will then be discharged west into the existing ditch north of the WSDOT access road where it will combine with a ditch flowing south at the bottom of the 2:1 slope. Core Design, Inc. MERLINO SHORT PLAT Page 2 Figure 1-1: Vicinity Map PROJECT Core Design, Inc. MERLINO SHORT PLAT Page 3 2 CONDITIONS AND REQUIREMENTS SUMMARY The proposed project is classified as requiring “Full Drainage Review” per the COR Amendments. Therefore, all eight core requirements and five special requirements will be addressed per Section 1.1 of the 2009 KCSWDM). 2.1 Core Requirements 2.1.1 Core Requirement #1: Discharge at the Natural Location The combined detention and water quality vault will discharge at the natural discharge location to the ditch north of the WSDOT access road and the ditch at the bottom of the 2:1 slope on the west side of the project. 2.1.2 Core Requirement #2: Offsite Analysis This core requirement is addressed in Section 3 of this report. 2.1.3 Core Requirement #3: Flow Control The detention vault has been designed to a flow control duration standard matching forested site conditions per page 1-35 of the COR Amendments. This requires that the developed condition discharge durations match the existing condition durations from 50% of the 2-year to the 50-year storm events and that the developed 2-year and 10-year peak discharge rates do not exceed the existing 2-year and 10-year peak discharge rates, respectively. 2.1.4 Core Requirement #4: Conveyance System A backwater analysis using King County Backwater (KCBW) will be performed during final engineering and will show that the proposed conveyance system provides sufficient capacity for the 25-year storm as calculated by the Rational Method. 2.1.5 Core Requirements #5: Erosion and Sediment Control Erosion and sediment control will be provided through catch basin protection, silt fencing and mulching. The permanent detention/water quality vault will also be utilized as a temporary sediment pond during construction. 2.1.6 Core Requirement #6: Maintenance and Operations The homeowners association will be responsible for the maintenance and operations of the stormwater vault. 2.1.7 Core Requirement #7: Financial Guarantees and Liability A bond quantities worksheet will be provided in Section 9 of this Report during Final Engineering. 2.1.8 Core Requirement #8: Water Quality Basic water quality treatment will be provided by dead storage in the vault. Core Design, Inc. MERLINO SHORT PLAT Page 4 2.2 Special Requirement #1: Other Adopted Area-Specific Requirements 2.2.1 Critical Drainage Areas This project is not in an aquifer protection zone or groundwater protection area. 2.2.2 Master Drainage Plan Not applicable. 2.2.3 Basin Plans Not applicable. 2.2.4 Salmon Conservation Plans (SCPs) Not applicable. 2.2.5 Stormwater Compliance Plans (SWCPs) Not applicable. 2.2.6 Lake Management Plans (LMPs) Not applicable. 2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) This project is not within a floodplain (see FEMA map included in Appendix B) and is not within an area with an applicable Flood Hazard Reduction Plan. Therefore, additional requirements from a Flood Hazard Reduction Plan do not apply. 2.2.8 Shared Facility Drainage Plans (SFDPs) Not applicable. 2.3 Special Requirement #2: Floodplain / Floodway Delineation This project is not located within the 100-year floodplain (see FEMA Map included in Appendix B). 2.4 Special Requirement #3: Flood Protection Facilities As this project is not located within a 100-year floodplain there are no levees, revetments or berms within the project. 2.5 Special Requirement #4: Source Controls These requirements are not applicable as the project is not a commercial, industrial or multi- family development. 2.6 Special Requirement #5: Oil Control This requirement does not apply because the project is not a commercial or industrial development nor is it expected to have more than 15,000 vehicles per day. Core Design, Inc. MERLINO SHORT PLAT Page 5 3 OFFSITE ANALYSIS 3.1 Study Area Definition and Maps The proposed project contains parcel numbers 0007200194 and 2023059085 totaling 3.69 acres. A map of the downstream can be found in Appendix B Downstream Drainage Map. 3.2 Resource Review Basin Reconnaissance Summary Reports No Basin Reconnaissance Summary Reports are available for the area that is within one mile of this project site. FEMA Maps A FEMA map dated May 16, 1995 number 53033C0977F was reviewed. The site is not located within a floodplain as it is covered by “Zone X – Outside of 500-year floodplain. The FEMA Map is included in Appendix B. Sensitive Areas Folio The City of Renton Sensitive Area Maps are included in Appendix B. Below is a summary of the project site regarding Coal Mine Hazards, Erosion Hazards, Steep Slopes and Landslides: • Coal Mine Hazard – A small area on the north east portion of the site located with a high coal mine hazard area. About a quarter of the site on the east is also located in a low coal mine hazard area. • Erosion Hazard – High • Steep Slopes – Due to the 2:1 slopes a majority of the site is located within the 40% to 90% slope range with the remainder of the site no steeper than 10%. • Landslide Hazard - Moderate City of Renton Soil Survey The City of Renton Soil Survey Reference 11-C shows the site as having BeD or Beausite (Till) soils. The Soils Map exhibit is included in Appendix B. Downstream Drainage Complaints Drainage complaints were researched within the study area. King County lists only one complaint (for dumping) downstream of the site which is over a quarter of a mile away and was closed in 1995, therefore there are no current documented downstream problems associated with this project site. See the Drainage Complaint Exhibit Appendix B. 3.3 Field Investigation Upstream Tributary Area There is no upstream tributary area for this project. Core Design, Inc. MERLINO SHORT PLAT Page 6 Level 1 Downstream Analysis Field Investigation A field investigations was conducted on March 7, 2014. The weather was sunny, clear and approximately 60 degrees. Cedar Avenue S drains south though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I- 405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch at the bottom of the slope. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch at the bottom of the 2:1 slope. The two ditches drain to a 54-inch catch basin with a birdcage into a piped system continuing west for 250 feet down the side slope on the east side of I-405 to a drainage structure in the shoulder. Drainage continues north for approximately 2,800 feet through a series of catch basins and pipes in I-405 to a WSDOT detention pond located west of I-405 and east of S 3rd Street. 3.4 Mitigation of Existing and Potential Problems Downstream Drainage Problems Requiring Special Attention Type 1 – Conveyance System Nuisance Problems There are no known, reported or observed current downstream conveyance nuisance problems. Type 2 – Severe Erosion Problems There are no known, reported or observed current downstream severe erosion problems Type 3-Severe Flooding Problems There are no known, reported or observed current downstream severe flooding problems. Department of Ecology 303d Listings Type 1 – Bacteria Problems There are no known or reported bacteria problems. Type 2 – Dissolved Oxygen (DO) Problems There are no known or reported dissolved oxygen problems. Type 3 – Temperature Problems There are no known or reported temperature problems. Type 4 – Metals Problems There are no known or reported downstream metals problems. Type 5 – Phosphorous Problems There are no known or reported downstream phosphorous problems. Type 6 – Turbidity Problems There are no known or reported downstream turbidity problems. Type 7 – High pH Problems There are no known or reported high pH problems. Drainage Adjustments There is no drainage adjustment proposed for this project. Core Design, Inc. MERLINO SHORT PLAT Page 7 4 FLOW CONTROL AND WATER QUALITY DESIGN 4.1 Existing Site Hydrology The project site is approximately 1.50 acres in size and is currently covered in grass. Cedar Avenue S drains south at approximately 2.5% though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I-405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch flowing south on the west boundary of the site. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch on the west boundary. See Table 4- 1 below and Figure 4-1: Existing Conditions. A site Soils Map is included in Appendix B and the KCRTS Hydrologic Soils Group table (Table 3.2.2.B) is included in Appendix C. There are approximately 0.14 acres of existing impervious area from Cedar Avenue S which will enter the proposed drainage system due to the frontage improvements. This area has been modeled as impervious in the pre-developed conditions. Historic site conditions are assumed for all existing onsite area of 1.50 acres per Section 1.2.3.1 of the 2009 KCSWDM (page 1-43) and are modeled as Till Forest. Table 4-1 Existing Conditions Areas GROUND COVER AREA (acres) Till-Forest 1.50 Impervious 0.14 TOTAL 1.64 The peak flow rates for the pre-developed conditions as determined by KCRTS (one hour time steps) are shown below. A regional scale factor of ST 1.0 was used as determined by Figure 3.2.2.A in Appendix C. Flow Frequency Analysis Time Series File:04139m_pre.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.116 2 2/09/01 15:00 0.175 1 100.00 0.990 0.054 7 1/05/02 16:00 0.116 2 25.00 0.960 0.105 3 2/28/03 3:00 0.105 3 10.00 0.900 0.035 8 8/26/04 2:00 0.103 4 5.00 0.800 0.063 6 1/05/05 8:00 0.094 5 3.00 0.667 0.103 4 1/18/06 16:00 0.063 6 2.00 0.500 0.094 5 11/24/06 4:00 0.054 7 1.30 0.231 0.175 1 1/09/08 9:00 0.035 8 1.10 0.091 Computed Peaks 0.156 50.00 0.980 Core Design, Inc. MERLINO SHORT PLAT Page 8 4.2 Developed Site Hydrology The site was mass graded as part of the I-405 project, so there will be no clearing and minimal grading to construct seven single-family lots, stormwater vault and associated utilities. All of the lots will drain to Cedar Avenue S. Half street frontage improvements on Cedar Avenue S will be completed to provide 13.5 feet of pavement from the right of way centerline, curb and gutter, an 8-foot planter and a 5-foot sidewalk. The developed condition areas are summarized in Table 4-2 and Figure 4-2 Developed Conditions Map. Table 4-2 Developed Condition Areas GROUND COVER AREA (acres) Till-Grass 0.62 Impervious 1.02 TOTAL 1.64 The undetained peak flow rates for the developed conditions as determined by KCRTS (one hour time steps) are shown below. Flow Frequency Analysis Time Series File:04139m_dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.298 6 2/09/01 2:00 0.602 1 100.00 0.990 0.243 8 1/05/02 16:00 0.382 2 25.00 0.960 0.358 3 2/27/03 7:00 0.358 3 10.00 0.900 0.263 7 8/26/04 2:00 0.316 4 5.00 0.800 0.316 4 10/28/04 16:00 0.316 5 3.00 0.667 0.316 5 1/18/06 16:00 0.298 6 2.00 0.500 0.382 2 10/26/06 0:00 0.263 7 1.30 0.231 0.602 1 1/09/08 6:00 0.243 8 1.10 0.091 Computed Peaks 0.529 50.00 0.980 Core Design, Inc. MERLINO SHORT PLAT Page 11 4.3 Performance Standards All stormwater facilities will be designed in accordance with the 2009 KCSWDM with the COR Amendments, with Flow Control Duration Standard Matching Forested Site Conditions. The proposed water quality treatment system will meet requirements from the Basic Water Quality Protection Menu. Flow Control: Duration Standard Matching Forested Site Conditions The Flow Control Duration Standard Matching Forested Site Conditions requires maintaining the durations of developed flows at their pre-development levels for all flows greater than one-half of the 2- year peak flow through the 50-year peak flow. The pre-development peak flow rates for the 2-year and 10-year runoff events must also be maintained under this requirement. Conveyance Capacity The proposed conveyance system will be designed with sufficient capacity to convey and contain the 25- year peak flow as determined by the Rational Method. It will also be verified that the 100-year peak flow will not create or aggravate a severe flooding or erosion problem per Section 1.2.2. Water Quality: Basic Water Quality Menu The Basic Water Quality Menu includes one pollutant removal targets: • Total Suspended Solids = 80% reduction The Basic Water Quality Menu, described in detail in Section 6.1.1 of the 2009 KCSWDM (page 6-4), provides eight options to meet the pollutant removal targets listed above. • Option 1: Biofiltration Swale • Option 2: Filter Strip • Option 3: Wetpond • Option 4: Wetvault • Option 5: Stormwater Wetland • Option 6: Combined Detention and Wetpool Facilities • Option 7: Sand Filter • Option 8: Stormfilter The project proposes to apply Option 4, a Wetvault. More detailed discussion and preliminary sizing calculations of the flow control and water quality treatment facility proposed for this project follows later in this section. 4.4 Flow Control System Calculation of Lot Impervious Area The impervious area per lot applied to the developed basin time series file was determined using the criteria in the 2009 KCSWDM page 3-27 and page 3-2 of the COR Amendments. The proposed development is urban residential. The site zoned R-8. The minimum i mpervious area per lot per the 2009 KCSWDM (page 3-27) would either be 4,000 square feet or the maximum impervious area as stated in Section 3.2.2.1 of the COR SWDMA, whichever is less. The maximum impervious surface allowed in the R-8, zone in the City of Renton, is 75%. Core Design, Inc. MERLINO SHORT PLAT Page 12 Flow Control BMPs/Individual Lot BMPs This project will not be served by an infiltration facility and therefore must apply flow control BMPs to supplement the flow mitigation provided by the detention vault. This project has lots less than 22,000 square feet so it is subject to the small lot BMP requirements. Full dispersion and full infiltration of the roof runoff is not feasible, so one or more of the following BMPs must be applied to an impervious area equal to at least 10% of the lot for lots up to 11,000 square feet and 20% of the lot for lots between 11,000 and 22,000 square feet. • Limited Infiltration • Basic Dispersion • Rain Garden • Permeable Pavement • Rainwater Harvesting • Vegetated Roof • Reduced Impervious Surface Credit • Native Growth Retention Credit This project will be implementing the reduced impervious surface credit to meet the requirements for individual lot BMPs. It is anticipated that less than 4,000 square feet of impervious area will be constructed on each lot. The actual amount of impervious area per lot will be determined during Final Engineering. Table 4-3 below summarizes the breakdown of the onsite areas. Table 4-3 Onsite Areas Lot Total Area (sf) Land Use Area Impervious (sf) Effective Impervious (sf) Till Grass (sf) Individual Lot BMP (sf) 1 7,112 4,000 3,289 3,112 711 2 6,709 4,000 3,329 2,709 671 3 6,652 4,000 3,335 2,652 665 4 6,595 4,000 3,341 2,595 660 5 7,080 4,000 3,292 3,080 708 6 7,013 4,000 3,299 3,013 701 7 7,989 4,000 3,201 3,989 799 ROW 14,307 9,620 9,620 4,687 Offsite 6,175 6,175 6,175 0 TOTAL to Vault 69,632 44,325 38,880 25,837 TOTAL to Vault (ac) 1.60 1.01 0.89 0.59 Notes: 1. Impervious Area = 4,000 sf or 75% of the Total Area, whichever is less 2. Effective Impervious Area = Impervious Area – Individual Lot BMP 3. Pervious Grass Area = Total Area – Impervious Area 4. Individual Lot BMP Area = 10% of Total Area (This area would not drain to the vault.) Therefore, there is a total of 1.60 acres draining to the vault consisting of 1.01 acres of impervious area and 0.59 acres of till-grass. As a conservative measure for preliminary sizing, the total impervious area was used in sizing the vault instead of the effective impervious area. Core Design, Inc. MERLINO SHORT PLAT Page 13 Bypass Area Due to topographic constraints, a small portion of the area on top of the vault will not discharge to the vault and will therefore be modeled as onsite bypass area. Thus, the detention vault will over-detain the remainder of the project to compensate for the unmitigated flows and the point of compliance will be evaluated at the point downstream of the pond at which the mitigated and unmitigated flows combine. Table 4-4 below summarizes the bypass area. Table 4-4 Bypass Area GROUND COVER AREA (SF) AREA (AC) Till-Grass 1,247 0.03 Impervious 639 0.01 TOTAL 1,886 0.04 Therefore, there is 0.05 acres of Till Grass bypass area. The associated unmitigated peak flows as determined with KCRTS 1-hour time intervals is shown below. Flow Frequency Analysis Time Series File:04139m_bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.005 4 2/09/01 2:00 0.011 1 100.00 0.990 0.004 7 1/05/02 16:00 0.006 2 25.00 0.960 0.006 2 2/27/03 7:00 0.005 3 10.00 0.900 0.003 8 8/26/04 2:00 0.005 4 5.00 0.800 0.004 6 10/28/04 16:00 0.005 5 3.00 0.667 0.005 3 1/18/06 16:00 0.004 6 2.00 0.500 0.005 5 11/24/06 3:00 0.004 7 1.30 0.231 0.011 1 1/09/08 6:00 0.003 8 1.10 0.091 Computed Peaks 0.009 50.00 0.980 Core Design, Inc. MERLINO SHORT PLAT Page 14 Detention Pond Modeling The proposed detention vault will be located at the south end of Cedar Avenue S with 8.3 feet of live storage. KCRTS Vault Calculation Type of Facility: Detention Vault Facility Length: 56.00 ft Facility Width: 40.00 ft Facility Area: 2240. sq. ft Effective Storage Depth: 8.20 ft Stage 0 Elevation: 216.00 ft Storage Volume: 18368. cu. ft Riser Head: 8.20 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.63 0.030 2 4.70 1.00 0.049 4.0 3 6.50 0.75 0.019 4.0 Top Notch Weir: None Outflow Rating Curve: None The proposed detention vault includes a two orifice control structure. The first orifice is 5/8 inches in diameter and is at the bottom of the riser. The second orifice is 4.7 feet above the live/dead interface elevation and is 1 inch in diameter and the third orifice is ¾ inches in diameter and 6.5 feet above the live/dead interface. The proposed vault will require a storage volume of 18,593 cubic feet with 8.3 feet of live storage. Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.60 0.41 8.30 224.30 18593. 0.427 2 0.30 0.10 8.06 224.06 18052. 0.414 3 0.30 0.08 7.14 223.14 15990. 0.367 4 0.36 0.07 6.77 222.77 15163. 0.348 5 0.32 0.06 5.94 221.94 13310. 0.306 6 0.19 0.03 4.86 220.86 10888. 0.250 7 0.24 0.02 4.47 220.47 10018. 0.230 8 0.26 0.02 3.24 219.24 7258. 0.167 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.41 0.01 ******** ******* 0.42 2 0.10 0.01 ******** ******* 0.10 3 0.08 0.01 ******** 0.11 0.09 4 0.07 0.01 ******** ******* 0.08 5 0.06 0.01 ******** ******* 0.06 6 0.03 0.00 ******** 0.06 0.04 7 0.02 0.00 ******** ******* 0.02 8 0.02 0.00 ******** ******* 0.02 Core Design, Inc. MERLINO SHORT PLAT Page 15 The combined outflow from the detention vault control structure and developed condition bypass area releases 0.04 cfs for the 2-year event and 0.09 cfs for the 10-year event. These release rates are below the pre-developed peak flows of 0.06 cfs and 0.11 cfs for the 2-year and 10-year rates, respectively. Therefore, the proposed facility meets the peak release rate requirements. The flow duration comparison analysis results for the provided detention vault are shown below. There is less than 10% excursion between the 2-year and 50-year release rate and the curve is entirely under the target curve for the required range of 50% 2-year to 2-year. Therefore, the proposed detention facility meets the flow duration requirement. Duration Comparison Anaylsis Base File: 04139m_pre.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.031 | 0.70E-02 0.65E-02 -7.2 | 0.70E-02 0.031 0.029 -8.7 0.038 | 0.52E-02 0.49E-02 -5.4 | 0.52E-02 0.038 0.037 -3.8 0.045 | 0.39E-02 0.36E-02 -5.9 | 0.39E-02 0.045 0.043 -2.8 0.051 | 0.29E-02 0.28E-02 -1.7 | 0.29E-02 0.051 0.050 -1.2 0.058 | 0.19E-02 0.17E-02 -10.9 | 0.19E-02 0.058 0.057 -1.2 0.064 | 0.14E-02 0.11E-02 -25.0 | 0.14E-02 0.064 0.060 -7.0 0.071 | 0.10E-02 0.91E-03 -11.1 | 0.10E-02 0.071 0.066 -5.9 0.077 | 0.85E-03 0.67E-03 -21.2 | 0.85E-03 0.077 0.074 -4.6 0.084 | 0.57E-03 0.38E-03 -34.3 | 0.57E-03 0.084 0.079 -5.4 0.090 | 0.44E-03 0.23E-03 -48.1 | 0.44E-03 0.090 0.082 -9.1 0.097 | 0.20E-03 0.13E-03 -33.3 | 0.20E-03 0.097 0.094 -3.2 0.103 | 0.11E-03 0.00E+00 -100.0 | 0.11E-03 0.103 0.098 -4.7 0.110 | 0.49E-04 0.00E+00 -100.0 | 0.49E-04 0.110 0.102 -7.4 0.116 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.116 0.103 -11.9 Maximum positive excursion = 0.001 cfs ( 1.3%) occurring at 0.052 cfs on the Base Data:04139m_pre.tsf and at 0.053 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.014 cfs (-12.0%) occurring at 0.116 cfs on the Base Data:04139m_pre.tsf and at 0.102 cfs on the New Data:dsout.tsf 4.5 Water Quality Calculations Basic Wetvault A Basic Wetvault includes a permanent wetpool that allows for the removal of 80% of Total Suspended Solids. Section 6.4.1.1 outlines a 4-step process to calculate the required wetpool volume. Step 1: Identify required wetpool volume factor (f) A basic wetpond requires a volume factor of 3.0. Core Design, Inc. MERLINO SHORT PLAT Page 16 Step 2: Determine rainfall (R) for the mean annual storm Figure 6.4.1.A (page 6-71 in the 2009 KCSWDM, included below and in Appendix C) is used to determine the rainfall, in inches, for the mean annual storm. The rainfall is then converted into feet for use in Equation 6-13 (shown below). The mean annual storm rainfall for this project site is 0.47” as noted on the project-specific Figure 6.4.1.A included in Appendix C. Step 3: Calculate runoff from the mean annual storm (Vr) for the developed site The land cover types and associated areas for each in the developed project site are used to calculate the amount of rainfall, in cubic feet, that runs off each land cover type. Coefficients specific to the four U.S. Department of Agriculture soil survey cover categories are weighted by the drainage areas and then multiplied by the rainfall, R, from Step 2. Equation 6-13 𝑉𝑉𝑟𝑟=(0.9𝐴𝐴𝑖𝑖+0.25𝐴𝐴𝑡𝑡𝑡𝑡+0.10𝐴𝐴𝑡𝑡𝑡𝑡+0.01𝐴𝐴𝑜𝑜)𝑥𝑥(𝑅𝑅) where Vr = calculated volume of runoff from mean annual storm Ai = area of impervious surface (43,795 sf) Atg = area of till soil covered with grass (25,837 sf) Atf = area of till soil covered with forest (0 sf) Ao = area of outwash soil covered with grass or forest (0 sf) R = rainfall from mean annual storm (0.039 ft) Using Equation 6-13 above and the land cover areas in the developed basin calculations, the volume of runoff from the mean annual storm is 1,797 cubic feet. Step 4: Calculate wetpool volume (Vb) The numbers / results from the previous steps are used in Equation 6-14 (shown below) to calculate the required wetpool volume. Equation 6-14 𝑉𝑉𝑏𝑏=𝑓𝑓𝑉𝑉𝑟𝑟 where Vb = calculated required minimum wetpool volume f = volume factor from Step 1 (3.0) Vr = volume of runoff from mean annual storm (1,797 cf) Using Equation 6-14 above and the results from the previous steps, the required minimum wetpool volume, Vb is 5,390 cubic feet. The proposed wetpool yields a volume of 5,440 cubic feet. Core Design, Inc. MERLINO SHORT PLAT Page 17 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN The onsite conveyance system will be analyzed using the King County Back Water (KCBW) program per the requirements described in Chapter 4 of the 2009 KCSWDM during Final Engineering. Core Design, Inc. MERLINO SHORT PLAT Page 18 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 19 6 SPECIAL REPORTS AND STUDIES The geotechnical report for this project completed by Icicle Creek Engineers, Inc. is provided under a separate cover. Core Design, Inc. MERLINO SHORT PLAT Page 20 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 21 7 OTHER PERMITS Ø NPDES Permit Ø Building Permits Ø ROW Use Permit Core Design, Inc. MERLINO SHORT PLAT Page 22 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 23 8 ESC ANALYSIS AND DESIGN This section will be completed during Final Engineering. Core Design, Inc. MERLINO SHORT PLAT Page 24 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 25 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 9.1 Bond Quantities A Site Improvement Bond Quantity Worksheet will be included prior to approval of the final engineering plans. 9.2 Facility Summaries Not applicable. 9.3 Declaration of Covenant Not applicable. Core Design, Inc. MERLINO SHORT PLAT Page 26 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 27 10 OPERATIONS AND MAINTENANCE The operations and maintenance information will be provided at Final Engineering. Core Design, Inc. MERLINO SHORT PLAT Page 28 THIS PAGE INTENTIONALLY LEFT BLANK Appendix A Parcel & Basin Information King County Parcel Report (2225069082) King County Parcel Report (2225069083) This report was generated on 3/3/2014 4:27:16 PM Contact us at giscenter@kingcounty.gov. © 2010 King County Electoral Districts King County planning and critical areas designations King County Districts and Development Conditions for parcel 0007200194 Parcel number 0007200194 Address Not Available Jurisdiction Renton Zipcode 98057 Kroll Map page 337 Thomas Guide page 656 Drainage Basin Black River and Lower Cedar River Watershed Duwamish - Green River and Cedar River / Lake Washington WRIA Duwamish-Green (9) and Cedar-Sammamish (8) PLSS NW - 20 - 23 - 5 Latitude 47.47216 Longitude -122.20223 Voting district RNT 11-1015 King County Council district District 5, Dave Upthegrove (206) 296-1005 Congressional district 9 Legislative district 11 School district Renton #403 Seattle school board district does not apply (not in Seattle) District Court electoral district Southeast Fire district does not apply Water district does not apply Sewer district does not apply Water & Sewer district does not apply Parks & Recreation district does not apply Hospital district Public Hospital District No. 1 Rural library district Rural King County Library System Tribal Lands?No King County zoning NA, check with jurisdiction Development conditions None Comprehensive Plan does not apply Urban Growth Area Urban Community Service Area does not apply Community Planning Area Newcastle Coal mine hazards?Yes Erosion hazards?Yes Landslide hazards?None mapped Seismic hazards?None mapped Potential annexation area does not apply Rural town?No Water service planning area does not apply Roads MPS zone 329 Transportation Concurrency Management does not apply Forest Production district?No Agricultural Production district?No Critical aquifer recharge area?None mapped 100-year flood plain?None mapped Wetlands at this parcel?None mapped This report was generated on 3/3/2014 4:29:50 PM Contact us at giscenter@kingcounty.gov. © 2010 King County Electoral Districts King County planning and critical areas designations King County Districts and Development Conditions for parcel 2023059085 Parcel number 2023059085 Address 700 BENSON RD S Jurisdiction Renton Zipcode 98057 Kroll Map page 337 Thomas Guide page 656 Drainage Basin Black River and Lower Cedar River Watershed Duwamish - Green River and Cedar River / Lake Washington WRIA Duwamish-Green (9) and Cedar-Sammamish (8) PLSS NW - 20 - 23 - 5 Latitude 47.47216 Longitude -122.20322 Voting district RNT 11-1015 King County Council district District 5, Dave Upthegrove (206) 296-1005 Congressional district 9 Legislative district 11 School district Renton #403 Seattle school board district does not apply (not in Seattle) District Court electoral district Southeast Fire district does not apply Water district does not apply Sewer district does not apply Water & Sewer district does not apply Parks & Recreation district does not apply Hospital district Public Hospital District No. 1 Rural library district Rural King County Library System Tribal Lands?No King County zoning NA, check with jurisdiction Development conditions None Comprehensive Plan does not apply Urban Growth Area Urban Community Service Area does not apply Community Planning Area Newcastle and Green River Valley Coal mine hazards?Yes Erosion hazards?Yes Landslide hazards?None mapped Seismic hazards?None mapped Potential annexation area does not apply Rural town?No Water service planning area does not apply Roads MPS zone 329 Transportation Concurrency Management does not apply Forest Production district?No Agricultural Production district?No Critical aquifer recharge area?None mapped 100-year flood plain?None mapped Wetlands at this parcel?None mapped Appendix B Resource Review & Off-site Analysis Documentation FEMA Map (53033C0977F) City of Renton Aquifer Protection Zones City of Renton Groundwater Protection Areas City of Renton Sensitive Area Maps City of Renton Soil Survey Drainage Complaints Exhibit Downstream Drainage Map Appendix C Pond Sizing City of Renton Flow Control Map Rainfall Region & Regional Scale Factor (Figure 3.2.2.A) KCRTS Hydrologic Soils Group Table (Table 3.2.2.B) Mean Annual Storm Precipitation (Figure 6.4.1.A) KCRTS Input Vault Summary Peaks Analysis Durations Analysis Page 1 KCRTS Program...File Directory: C:\KC_SWDM\KC_DATA\ [C] CREATE a new Time Series ST 1.50 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.00 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.14 0.00 0.000000 Impervious 04139M_Pre.tsf T 1.00000 T [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Pre.tsf 04139M_Pre.pks [R] RETURN to Previous Menu [C] CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.03 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.01 0.00 0.000000 Impervious 04139M_Bypass.tsf T 1.00000 T [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Bypass.tsf 04139M_Bypass.pks [R] RETURN to Previous Menu [C] CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.59 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 1.01 0.00 0.000000 Impervious 04139M_Dev.tsf T 1.00000 T Page 2 [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Dev.tsf 04139M_Dev.pks [D] Compute Flow DURATION and Exceedence 04139M_Pre.tsf 04139M_Pre.dur F F 36 0.0031 0.026 [R] RETURN to Previous Menu Page 2 Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 56.00 ft Facility Width: 40.00 ft Facility Area: 2240. sq. ft Effective Storage Depth: 8.20 ft Stage 0 Elevation: 216.00 ft Storage Volume: 18368. cu. ft Riser Head: 8.20 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.63 0.030 2 4.70 1.00 0.049 4.0 3 6.50 0.75 0.019 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 216.00 0. 0.000 0.000 0.00 0.01 216.01 22. 0.001 0.001 0.00 0.02 216.02 45. 0.001 0.001 0.00 0.03 216.03 67. 0.002 0.002 0.00 0.04 216.04 90. 0.002 0.002 0.00 0.05 216.05 112. 0.003 0.002 0.00 0.21 216.21 470. 0.011 0.005 0.00 0.37 216.37 829. 0.019 0.006 0.00 0.53 216.53 1187. 0.027 0.008 0.00 0.70 216.70 1568. 0.036 0.009 0.00 0.86 216.86 1926. 0.044 0.010 0.00 1.02 217.02 2285. 0.052 0.011 0.00 1.18 217.18 2643. 0.061 0.011 0.00 1.34 217.34 3002. 0.069 0.012 0.00 1.50 217.50 3360. 0.077 0.013 0.00 1.66 217.66 3718. 0.085 0.014 0.00 1.82 217.82 4077. 0.094 0.014 0.00 1.98 217.98 4435. 0.102 0.015 0.00 2.14 218.14 4794. 0.110 0.016 0.00 2.30 218.30 5152. 0.118 0.016 0.00 2.46 218.46 5510. 0.127 0.017 0.00 2.62 218.62 5869. 0.135 0.017 0.00 2.79 218.79 6250. 0.143 0.018 0.00 2.95 218.95 6608. 0.152 0.018 0.00 3.11 219.11 6966. 0.160 0.019 0.00 3.27 219.27 7325. 0.168 0.019 0.00 3.43 219.43 7683. 0.176 0.020 0.00 3.59 219.59 8042. 0.185 0.020 0.00 3.75 219.75 8400. 0.193 0.021 0.00 3.91 219.91 8758. 0.201 0.021 0.00 4.07 220.07 9117. 0.209 0.021 0.00 4.23 220.23 9475. 0.218 0.022 0.00 4.39 220.39 9834. 0.226 0.022 0.00 4.55 220.55 10192. 0.234 0.023 0.00 4.70 220.70 10528. 0.242 0.023 0.00 4.71 220.71 10550. 0.242 0.023 0.00 4.72 220.72 10573. 0.243 0.024 0.00 4.73 220.73 10595. 0.243 0.025 0.00 4.74 220.74 10618. 0.244 0.026 0.00 4.75 220.75 10640. 0.244 0.028 0.00 4.76 220.76 10662. 0.245 0.030 0.00 4.77 220.77 10685. 0.245 0.030 0.00 4.78 220.78 10707. 0.246 0.031 0.00 4.79 220.79 10730. 0.246 0.032 0.00 4.95 220.95 11088. 0.255 0.037 0.00 5.12 221.12 11469. 0.263 0.041 0.00 5.28 221.28 11827. 0.272 0.045 0.00 5.44 221.44 12186. 0.280 0.048 0.00 5.60 221.60 12544. 0.288 0.051 0.00 5.76 221.76 12902. 0.296 0.053 0.00 5.92 221.92 13261. 0.304 0.056 0.00 6.08 222.08 13619. 0.313 0.058 0.00 6.24 222.24 13978. 0.321 0.060 0.00 6.40 222.40 14336. 0.329 0.062 0.00 6.50 222.50 14560. 0.334 0.063 0.00 6.51 222.51 14582. 0.335 0.064 0.00 6.52 222.52 14605. 0.335 0.065 0.00 6.53 222.53 14627. 0.336 0.066 0.00 6.54 222.54 14650. 0.336 0.067 0.00 6.55 222.55 14672. 0.337 0.068 0.00 6.56 222.56 14694. 0.337 0.068 0.00 6.72 222.72 15053. 0.346 0.073 0.00 6.88 222.88 15411. 0.354 0.077 0.00 7.04 223.04 15770. 0.362 0.081 0.00 7.21 223.21 16150. 0.371 0.084 0.00 7.37 223.37 16509. 0.379 0.087 0.00 7.53 223.53 16867. 0.387 0.090 0.00 7.69 223.69 17226. 0.395 0.093 0.00 7.85 223.85 17584. 0.404 0.096 0.00 8.01 224.01 17942. 0.412 0.098 0.00 8.17 224.17 18301. 0.420 0.101 0.00 8.20 224.20 18368. 0.422 0.101 0.00 8.30 224.30 18592. 0.427 0.410 0.00 8.40 224.40 18816. 0.432 0.975 0.00 8.50 224.50 19040. 0.437 1.710 0.00 8.60 224.60 19264. 0.442 2.500 0.00 8.70 224.70 19488. 0.447 2.780 0.00 8.80 224.80 19712. 0.453 3.040 0.00 8.90 224.90 19936. 0.458 3.280 0.00 9.00 225.00 20160. 0.463 3.490 0.00 9.10 225.10 20384. 0.468 3.700 0.00 9.20 225.20 20608. 0.473 3.900 0.00 9.30 225.30 20832. 0.478 4.080 0.00 9.40 225.40 21056. 0.483 4.260 0.00 9.50 225.50 21280. 0.489 4.430 0.00 9.60 225.60 21504. 0.494 4.590 0.00 9.70 225.70 21728. 0.499 4.750 0.00 9.80 225.80 21952. 0.504 4.910 0.00 9.90 225.90 22176. 0.509 5.050 0.00 10.00 226.00 22400. 0.514 5.200 0.00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.60 0.41 8.30 224.30 18593. 0.427 2 0.30 0.10 8.06 224.06 18052. 0.414 3 0.30 0.08 7.14 223.14 15990. 0.367 4 0.36 0.07 6.77 222.77 15163. 0.348 5 0.32 0.06 5.94 221.94 13310. 0.306 6 0.19 0.03 4.86 220.86 10888. 0.250 7 0.24 0.02 4.47 220.47 10018. 0.230 8 0.26 0.02 3.24 219.24 7258. 0.167 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.41 0.01 ******** ******* 0.42 2 0.10 0.01 ******** ******* 0.10 3 0.08 0.01 ******** 0.11 0.09 4 0.07 0.01 ******** ******* 0.08 5 0.06 0.01 ******** ******* 0.06 6 0.03 0.00 ******** 0.06 0.04 7 0.02 0.00 ******** ******* 0.02 8 0.02 0.00 ******** ******* 0.02 ---------------------------------- Route Time Series through Facility Inflow Time Series File:04139m_dev.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.602 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.415 CFS at 9:00 on Jan 9 in Year 8 Peak Reservoir Stage: 8.30 Ft Peak Reservoir Elev: 224.30 Ft Peak Reservoir Storage: 18593. Cu-Ft : 0.427 Ac-Ft Add Time Series:04139m_bypass.tsf Peak Summed Discharge: 0.423 CFS at 9:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.100 2 2/09/01 20:00 0.415 8.30 1 100.00 0.990 0.023 7 1/07/02 4:00 0.100 8.12 2 25.00 0.960 0.074 4 3/06/03 22:00 0.083 7.14 3 10.00 0.900 0.019 8 8/26/04 7:00 0.074 6.77 4 5.00 0.800 0.034 6 1/08/05 1:00 0.056 5.94 5 3.00 0.667 0.056 5 1/19/06 0:00 0.034 4.86 6 2.00 0.500 0.083 3 11/24/06 8:00 0.023 4.47 7 1.30 0.231 0.415 1 1/09/08 9:00 0.019 3.24 8 1.10 0.091 Computed Peaks 0.310 8.27 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.103 2 2/09/01 20:00 0.423 1 100.00 0.990 0.023 7 12/29/01 9:00 0.103 2 25.00 0.960 0.076 4 3/06/03 21:00 0.085 3 10.00 0.900 0.020 8 8/26/04 4:00 0.076 4 5.00 0.800 0.035 6 1/08/05 2:00 0.058 5 3.00 0.667 0.058 5 1/18/06 22:00 0.035 6 2.00 0.500 0.085 3 11/24/06 8:00 0.023 7 1.30 0.231 0.423 1 1/09/08 9:00 0.020 8 1.10 0.091 Computed Peaks 0.316 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 31402 51.210 51.210 48.790 0.488E+00 0.004 6942 11.321 62.531 37.469 0.375E+00 0.007 6069 9.897 72.428 27.572 0.276E+00 0.010 4666 7.609 80.038 19.962 0.200E+00 0.013 4964 8.095 88.133 11.867 0.119E+00 0.015 2627 4.284 92.417 7.583 0.758E-01 0.018 1938 3.160 95.577 4.423 0.442E-01 0.021 1523 2.484 98.061 1.939 0.194E-01 0.024 720 1.174 99.235 0.765 0.765E-02 0.027 31 0.051 99.286 0.714 0.714E-02 0.029 19 0.031 99.317 0.683 0.683E-02 0.032 38 0.062 99.379 0.621 0.621E-02 0.035 56 0.091 99.470 0.530 0.530E-02 0.038 35 0.057 99.527 0.473 0.473E-02 0.041 32 0.052 99.579 0.421 0.421E-02 0.043 34 0.055 99.635 0.365 0.365E-02 0.046 22 0.036 99.671 0.329 0.329E-02 0.049 22 0.036 99.706 0.294 0.294E-02 0.052 21 0.034 99.741 0.259 0.259E-02 0.055 32 0.052 99.793 0.207 0.207E-02 0.057 31 0.051 99.843 0.157 0.157E-02 0.060 17 0.028 99.871 0.129 0.129E-02 0.063 16 0.026 99.897 0.103 0.103E-02 0.066 3 0.005 99.902 0.098 0.978E-03 0.068 2 0.003 99.905 0.095 0.946E-03 0.071 5 0.008 99.914 0.086 0.864E-03 0.074 8 0.013 99.927 0.073 0.734E-03 0.077 9 0.015 99.941 0.059 0.587E-03 0.080 7 0.011 99.953 0.047 0.473E-03 0.082 8 0.013 99.966 0.034 0.342E-03 0.085 4 0.007 99.972 0.028 0.277E-03 0.088 2 0.003 99.976 0.024 0.245E-03 0.091 3 0.005 99.980 0.020 0.196E-03 0.094 2 0.003 99.984 0.016 0.163E-03 0.096 3 0.005 99.989 0.011 0.114E-03 0.099 5 0.008 99.997 0.003 0.326E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 31390 51.190 51.190 48.810 0.488E+00 0.004 6889 11.235 62.425 37.575 0.376E+00 0.007 5980 9.752 72.177 27.823 0.278E+00 0.010 4912 8.010 80.188 19.812 0.198E+00 0.013 4888 7.971 88.159 11.841 0.118E+00 0.016 2580 4.207 92.366 7.634 0.763E-01 0.019 1956 3.190 95.556 4.444 0.444E-01 0.021 1410 2.299 97.856 2.144 0.214E-01 0.024 818 1.334 99.189 0.811 0.811E-02 0.027 60 0.098 99.287 0.713 0.713E-02 0.030 17 0.028 99.315 0.685 0.685E-02 0.033 38 0.062 99.377 0.623 0.623E-02 0.036 57 0.093 99.470 0.530 0.530E-02 0.039 35 0.057 99.527 0.473 0.473E-02 0.042 32 0.052 99.579 0.421 0.421E-02 0.044 33 0.054 99.633 0.367 0.367E-02 0.047 25 0.041 99.674 0.326 0.326E-02 0.050 20 0.033 99.706 0.294 0.294E-02 0.053 20 0.033 99.739 0.261 0.261E-02 0.056 32 0.052 99.791 0.209 0.209E-02 0.059 34 0.055 99.847 0.153 0.153E-02 0.062 14 0.023 99.870 0.130 0.130E-02 0.064 15 0.024 99.894 0.106 0.106E-02 0.067 6 0.010 99.904 0.096 0.962E-03 0.070 2 0.003 99.907 0.093 0.930E-03 0.073 4 0.007 99.914 0.086 0.864E-03 0.076 7 0.011 99.925 0.075 0.750E-03 0.079 9 0.015 99.940 0.060 0.603E-03 0.082 8 0.013 99.953 0.047 0.473E-03 0.084 7 0.011 99.964 0.036 0.359E-03 0.087 5 0.008 99.972 0.028 0.277E-03 0.090 2 0.003 99.976 0.024 0.245E-03 0.093 3 0.005 99.980 0.020 0.196E-03 0.096 2 0.003 99.984 0.016 0.163E-03 0.099 4 0.007 99.990 0.010 0.978E-04 0.102 3 0.005 99.995 0.005 0.489E-04 Duration Comparison Anaylsis Base File: 04139m_pre.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.031 | 0.70E-02 0.65E-02 -7.2 | 0.70E-02 0.031 0.029 -8.7 0.038 | 0.52E-02 0.49E-02 -5.4 | 0.52E-02 0.038 0.037 -3.8 0.045 | 0.39E-02 0.36E-02 -5.9 | 0.39E-02 0.045 0.043 -2.8 0.051 | 0.29E-02 0.28E-02 -1.7 | 0.29E-02 0.051 0.050 -1.2 0.058 | 0.19E-02 0.17E-02 -10.9 | 0.19E-02 0.058 0.057 -1.2 0.064 | 0.14E-02 0.11E-02 -25.0 | 0.14E-02 0.064 0.060 -7.0 0.071 | 0.10E-02 0.91E-03 -11.1 | 0.10E-02 0.071 0.066 -5.9 0.077 | 0.85E-03 0.67E-03 -21.2 | 0.85E-03 0.077 0.074 -4.6 0.084 | 0.57E-03 0.38E-03 -34.3 | 0.57E-03 0.084 0.079 -5.4 0.090 | 0.44E-03 0.23E-03 -48.1 | 0.44E-03 0.090 0.082 -9.1 0.097 | 0.20E-03 0.13E-03 -33.3 | 0.20E-03 0.097 0.094 -3.2 0.103 | 0.11E-03 0.00E+00 -100.0 | 0.11E-03 0.103 0.098 -4.7 0.110 | 0.49E-04 0.00E+00 -100.0 | 0.49E-04 0.110 0.102 -7.4 0.116 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.116 0.103 -11.9 Maximum positive excursion = 0.001 cfs ( 1.3%) occurring at 0.052 cfs on the Base Data:04139m_pre.tsf and at 0.053 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.014 cfs (-12.0%) occurring at 0.116 cfs on the Base Data:04139m_pre.tsf and at 0.102 cfs on the New Data:dsout.tsf Cumulative ProbabilityDischarge (CFS)-2105-1105010 oo ooo R 1 2 5 10 20 30 40 50 2 60 70 80 5 90 10 95 20 98 50 99 100 Return Period rdout.pks in Sea-Tac dsout.pks 04139M_Pre.pks Probability ExceedenceDischarge (CFS)0.000.020.040.060.080.100.12-510 -410 -310 -210 -110 010 o oo ooo R rdout.dur dsout.dur 04139M_Pre.dur Appendix D Conveyance Calculations (To be provided at Final Engineering)