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Home My WebLink AboutTIR160072016 D. R. STRONG Consulting Engineers Inc. The Pines Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT for THE PINES PRELIMINARY PLAT 850 & 870 Monroe Avenue NE, Renton, Washington NSER ISS E FORP I N G O ER DETS REE N G INELA 53232 OIETATHSOY SF OT GNIHASWIDEIPL.O C BAD E N GI N E E R BAD E N GI N E E R ILA Z ____________________________________________________________________________ DRS Project No. 16007 Renton File No. Owner/Applicant Harbour Homes, LLC 400 North 34th Street, Suite 300 Seattle, Washington 98103 Report Prepared by D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue Kirkland, WA 98033 (425) 827-3063 Report Issue Date June 6, 2016 2016 D. R. STRONG Consulting Engineers Inc. The Pines Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT THE PINES PRELIMINARY PLAT TABLE OF CONTENTS SECTION I ...................................................................................................................... 1 Project Overview ......................................................................................................... 1 Predeveloped Site Conditions ..................................................................................... 1 Developed Site Conditions .......................................................................................... 1 SECTION II ................................................................................................................... 11 Conditions and Requirements Summary ................................................................... 11 Conditions of Approval............................................................................................... 13 SECTION III .................................................................................................................. 14 Off-Site Analysis ........................................................................................................ 14 Task 1: Define and Map Study Area ...................................................................... 15 Task 2: Resource Review ...................................................................................... 16 Task 3: Field Inspection ......................................................................................... 25 Task 4: Drainage System Description and Problem Descriptions .......................... 26 Task 5: Mitigation of Existing or Potential Problems .............................................. 29 SECTION IV .................................................................................................................. 35 Flow Control Analysis and Water Quality Design ...................................................... 35 Existing Site Hydrology .......................................................................................... 35 Developed Site Hydrology ...................................................................................... 37 Performance Standards ............................................................................................. 40 Flow Control System ................................................................................................. 41 Water Quality Treatment System ............................................................................... 47 SECTION V ................................................................................................................... 49 Conveyance System Analysis and Design ................................................................ 49 SECTION VI .................................................................................................................. 50 Special Reports and Studies ..................................................................................... 50 SECTION VII ................................................................................................................. 51 Other Permits, Variances and Adjustments ............................................................... 51 SECTION VIII ................................................................................................................ 52 CSWPPP Analysis and Design (Part A) .................................................................... 52 SWPPP Plan Design (Part B) .................................................................................... 52 SECTION IX .................................................................................................................. 54 Bond Quantities, Facility Summaries, and Declaration of Covenant .......................... 54 Stormwater Facility Summary Sheet ......................................................................... 55 2016 D. R. STRONG Consulting Engineers Inc. The Pines Technical Information Report Renton, Washington SECTION X ................................................................................................................... 57 Operations and Maintenance Manual ........................................................................ 57 APPENDICES ............................................................................................................... 58 Appendix “A” Legal Description ................................................................................. 59 List of Figures Figure 1 TIR Worksheet .................................................................................................. 2 Figure 2 Vicinity Map ....................................................................................................... 7 Figure 3 Drainage Basins, Subbasins, and Site Characteristics ..................................... 8 Figure 4 Soils .................................................................................................................. 9 Figure 5 City of Renton Topography Map ..................................................................... 17 Figure 6 City of Renton Coal Mine Hazard Areas Map ................................................. 18 Figure 7 City of Renton Flood Hazards Map ................................................................. 19 Figure 8 City of Renton Streams and Wetlands Map .................................................... 20 Figure 9 City of Renton Landslide Hazards Map ........................................................... 21 Figure 10 City of Renton Seismic Hazard Areas Map ................................................... 22 Figure 11 FEMA Map .................................................................................................... 23 Figure 12 King County iMap Drainage Complaints Map................................................ 24 Figure 13 Offsite Analysis Downstream Map ................................................................ 30 Figure 14 Offsite Analysis Downstream Table .............................................................. 31 Figure 15 Predeveloped Area Map ............................................................................... 36 Figure 16 Developed Area Map .................................................................................... 39 Figure 17 Detention & Water Quality Facility Details ..................................................... 48 2016 D. R. STRONG Consulting Engineers Inc. Page 1 The Pines Technical Information Report Renton, Washington SECTION I PROJECT OVERVIEW The Project is the proposed subdivision of two parcels into 14 single-family residential lots, per the City of Renton’s (City) subdivision process. The Project is located at 850 & 870 Monroe Avenue NE, Renton, Washington (Site) also known as Tax Parcel Numbers 092305-9116, & -9117. The Project will meet the drainage requirements of the 2009 King County Surface Water Design Manual (Manual), as adopted by the City. PREDEVELOPED SITE CONDITIONS The total existing Site area is approximately 107,969 s.f. (2.48 acres). The Site is currently developed with two single family homes, gravel driveways, one detached garage, two sheds, a barn, and landscaping. The south-eastern portion of the Site appears to be undisturbed and in a forested condition with light underbrush. A high point exists at the eastern property line of the Site creating a shallow grade west maintaining one Threshold Discharge Areas (TDA). Runoff generated by the TDA gradually sheet flows east to west towards Monroe Avenue NE. The Natiral Discarge Area (NDA) of the Site is runoff sheet flow over the west property line. Sheet flow is captured by the curb and gutter located on the east side of Monroe Ave NE where runoff then enters one of two, type 1 catch basins creating two downstream paths. Runoff collected by the two catch basins is conveyed to a 24” diameter pipe where the two downstream paths converge and flow south through the existing stormwater system. DEVELOPED SITE CONDITIONS The applicant is seeking approval to subdivide 2.48 acres into 14 single–family residential lots (Project), with lot sizes ranging from approximately 5,001 s.f. to 6,990 s.f. All existing improvements located on the Site will be demolished or removed during plat construction. The project is required to provide level 2 flow control and basic water quality treatment. The Site falls within the Peak Rate Flow Control Stadard area matching existing Site conditions. The proposed impervious surface areas are as follows: frontage improvements consisting of a 5’ sidwalk along Monroe Ave NE, Road A, the 14 new single-family residences and their driveways, and Tract B, the detention facility, will generate approximately 63,723 s.f. of impervious area (1.46 acres). The remainder of the developed Site will be modeled as till grass 42,063 s.f. (0.97 acre). A small portion of ROW frontage on Monroe Ave NE, along the north half of the Site will be bypass. Bypass runoff will continue along its current flow path and converge with the Site runoff after detention, flowing south within the Monroe Ave NE conveyance system. (See Section IV). 2016 D. R. STRONG Consulting Engineers Inc. Page 2 The Pines Technical Information Report Renton, Washington FIGURE 1 TIR WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Harbour Homes, LLC Phone: (206) 315-8130 Address: 400 North 34th St, Suite 300 Seattle, WA 98103 Project Engineer: Yoshio L. Piediscalzi, P.E. Company: D. R. STRONG Consulting Engineers Inc. Phone: (425) 827-3063 Project Name: The Pines City Permit#: U 2016-0XXXX Location: Township: 23 North Range: 05 East Section: 09 Site Address: 850 & 870 Monroe Avenue NE Renton, WA Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse Services Subdivision / Short Subdivision / UPD Building Services: M/F / Commercial / SFR Clearing and Grading Right-of-Way Other: DFW HPA Shoreline Mngmt COE 404 Structural DOE Dam Safety Rockery/Vault FEMA Floodplain ESA Section 7 COE Wetlands Other: Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review Full / Targeted / (circle): Large Site Date (include revision June 6th, 2016 dates): Date of Final: Site Improvement Plan (Engr. Plans) Type (circle one): Full / Modified / : Small Site Date (include revision dates): Date of Final: Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) _____________________________________________________________________________________ _____________________________________________________________________________________ ____________________________________________________________________________________ Date of Approval: 2016 D. R. STRONG Consulting Engineers Inc. Page 3 The Pines Technical Information Report Renton, Washington Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: TBD Completion Date Describe: Monitor discharge location during construction. Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: Highlands Special District Overlays: N/A Drainage Basin: East Lake Washington – Renton Stormwater Requirements: Level 2 Flow Control and Basic WQ treatment Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/ Stream Lake Wetlands Closed Depression Floodplain Other Steep Slope Erosion Hazard Landslide Hazard Coal Mine Hazard Seismic Hazard Habitat Protection Part 10 SOILS Soil Type AmC Slopes 6-15% Erosion Potential Moderate to Severe High Groundwater Table Sole Source Aquifer other Seeps/Springs Additional Sheets Attached 2016 D. R. STRONG Consulting Engineers Inc. Page 4 The Pines Technical Information Report Renton, Washington Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core Requirement #2 – Offsite Analysis SEPA Additional Sheet Attached LIMITATION / SITE CONSTRAINT Part 12 TIR SUMMARY SHEET Threshold Discharge Area: Site comprised of one TDA (name or description) Core Requirements (all 8 apply) Discharge of Natural Location yes Number of Natural Discharge Locations: 1 Offsite Analysis Level: 1 / 2 / 3 dated: 03/21/16 Flow Control Level: 1 / 2 / 3 or Exemption Number (incl. facility summary sheet Small Site BMPS N/A Conveyance System Spill containment located at: TBD Erosion and Sediment Control ESC Site Supervisor: T/B/D Contact Phone: T/B/D After Hours Phone: T/B/D Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No Liability Water Quality Type: Basic / Sens Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. Landscape Management Plan: Yes / No Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared / None Requirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/A Source Control Describe Landuse: (comm. / industrial landuse) Describe any structural controls: Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? 2016 D. R. STRONG Consulting Engineers Inc. Page 5 The Pines Technical Information Report Renton, Washington Other Drainage Structures Describe: Runoff will be collected and conveyed to the wet-vault detention facility located in Tract B. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operations of Permanent Facilities Flag Limits of SAO and open space Preservation areas Other Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other Vault Biofiltration Wetpool Media Filtration Oil Control Spill Control Flow Control BMPs Other Wet-vault 2016 D. R. STRONG Consulting Engineers Inc. Page 6 The Pines Technical Information Report Renton, Washington Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other: Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other: Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 2016 D. R. STRONG Consulting Engineers Inc. Page 7 The Pines Technical Information Report Renton, Washington FIGURE 2 VICINITY MAP The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Site 2016 D. R. STRONG Consulting Engineers Inc. Page 8 The Pines Technical Information Report Renton, Washington FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS 2016 D. R. STRONG Consulting Engineers Inc. Page 9 The Pines Technical Information Report Renton, Washington FIGURE 4 SOILS 2016 D. R. STRONG Consulting Engineers Inc. Page 10 The Pines Technical Information Report Renton, Washington King County Area, Washington AmC—Arents, Alderwood material, 6 to 15 percent slopes Map Unit Setting x National map unit symbol: 1hmsq x Mean annual precipitation: 35 to 60 inches x Mean annual air temperature: 50 degrees F x Frost-free period: 150 to 200 days x Farmland classification: Not prime farmland Map Unit Composition x Arents, alderwood material, and similar soils: 100 percent x Estimates are based on observations, descriptions, and transects of the map unit. Description of Arents, Alderwood Material Setting x Landform: Till plains x Parent material: Basal till Typical profile x H1 - 0 to 26 inches: gravelly sandy loam x H2 - 26 to 60 inches: very gravelly sandy loam Properties and qualities x Slope: 6 to 15 percent x Depth to restrictive feature: 20 to 40 inches to densic material x Natural drainage class: Moderately well drained x Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) x Depth to water table: About 16 to 36 inches x Frequency of flooding: None x Frequency of ponding: None x Available water storage in profile: Very low (about 2.3 inches) Interpretive groups x Land capability classification (irrigated): None specified x Land capability classification (nonirrigated): 4s x Hydrologic Soil Group: B/D See Appendix B for Geotechnical Engineering Study 2016 D. R. STRONG Consulting Engineers Inc. Page 11 The Pines Technical Information Report Renton, Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: x C.R. #1 – Discharge at the Natural Location: Existing drainage discharges the Site at one location, maintaining one TDA. The topography indicates that all stormwater runoff leaves the Site as sheet flow across the west property line. Runoff is collected by the curb and gutter on the east side of Monroe Avenue NE. x C.R. #2 – Offsite Analysis: Analysis is included in Section III. The Analysis describes the Site’s runoff patterns in detail. x C.R. #3 – Flow Control: The Project is required to adhere to Level 2 Flow Control Standards. One detention/wetvault will provide flow control as required for the new and replaced impervious and pervious surfaces. The Site is required to “match developed discharge durations to existing conditions durations for the range of predeveloped discharge rates from 50% of the two-year peak flow up to the full 50- year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2 and the 10 year return periods,” (City of Renton 2009 Surface Water Design Manual Amendment, Sec. 1.2.3.1). A detention vault will accommodate this requirement. x C.R. #4 – Conveyance System: New pipe systems 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. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. This analysis will be performed at time of construction plan preparation. x C.R. #5 – Erosion and Sediment Control: The Project will provide the seven minimum ESC measures. A temporary erosion and sedimentation control plan will be prepared at the time construction plan preparation. x C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual will be included in Section X at the time of construction plan preparation. x C.R. #7 – Financial Guarantees: Prior to commencing construction, 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 2016 D. R. STRONG Consulting Engineers Inc. Page 12 The Pines Technical Information Report Renton, Washington two-year period following posting of the drainage defect and maintenance financial guarantee. x C.R. #8 – Water Quality: The Project is required to provide basic water quality treatment. A wetvault will accommodate this requirement. x S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. x S.R. #2 – Floodplain/Floodway Delineation: Not applicable for this Project. x S.R. #3 – Flood Protection Facilities: Not applicable for this Project. x S.R. #4 – Source Control: Not applicable for this Project. x S.R. #5 – Oil Control: Not applicable for this Project. x S.R. #6 – Aquifer Protection Area: Site not located within zones 1 and 2, therefore not applicable for this Project. 2016 D. R. STRONG Consulting Engineers Inc. Page 13 The Pines Technical Information Report Renton, Washington CONDITIONS OF APPROVAL The Pines U 2016-0XXXX TBD 2016 D. R. STRONG Consulting Engineers Inc. Page 14 The Pines Technical Information Report Renton, Washington SECTION III OFF-SITE ANALYSIS An offsite Level One Downstream Analysis was prepared by D.R. STRONG Consulting Engineers Inc. and is included in this section. 2016 D. R. STRONG Consulting Engineers Inc. Page 15 The Pines Level One Downstream Analysis Renton, Washington LEVEL ONE DOWNSTREAM ANALYSIS DISCLAIMER: This report was prepared at the request of HARBOUR HOMES, llc for the 2.8 acre parcel known as a portion of the SOUTHWEST Quarter of Section 09, Township 23 North, Range 5 East, W.M., in King County, Tax Parcel Numbers 092305-9116, & -9117 (Site). D. R. STRONG Consulting Engineers Inc. (DRS) has prepared this report for the exclusive use of DRS, the owner, and their agents, for specific application to the development project as described herein. Use or reliance on this report, or any of its contents for any revisions of this project, or any other project, or by others not described above, is forbidden without the expressed permission by DRS. TASK 1: DEFINE AND MAP STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2009 King County Surface Water Design Manual and City Amendments as adopted by the City of Renton (Manual). The Site is located at 850 & 870 Monroe Avenue NE, Renton, Washington. The Project is the subdivision of three parcels into 14 single-family lots. See Figures 1, 2, 3, and 5 for maps of the study area. 2016 D. R. STRONG Consulting Engineers Inc. Page 16 The Pines Level One Downstream Analysis Renton, Washington TASK 2: RESOURCE REVIEW x Adopted Basin Plans: The City of Renton and King County Department of Development and Environmental Services (DDES) and Department of Natural Resources and Parks (DNRP) do not have a specific plan for the East Lake Washington Drainage Basin. x Finalized Drainage Studies: No available applicable drainage studies at this time. x Basin Reconnaissance Summary Reports: None available. x Comprehensive Plans: Renton’s Comprehensive Plan, adopted on June 22, 2015, effective July 1, 2015. x Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 10. x Other Offsite Analysis Reports: Albert Balch’s President Park No. 7 & No. 8 and Skyland Heights No. 2. x Sensitive Areas Map Folios: See Figures 6-9. x DNRP Drainage Complaints and Studies: Per King County Water and Land Resources Division, there were no complaints within the downstream paths, within approximately one mile from the Site within the last 10 years. See figure 11. x USDA King County Soils Survey: See Figure 4 x Wetlands Inventory: Vol. 2 East (1990) – No wetlands identified along the downstream paths in the KC Wetlands Inventory. The City of Renton Mapping Applications indicates there are also no wetlands along the downstream path. See Figure 8. x Migrating River Studies: The Site is not located near the channel migration zones of Cedar River, Tolt River, Raging River, Snoqualmie River, or Green River. x King County Designated Water Quality Problems: Per the Washington State Water Quality Assessment 303(d)/305(b) Integrated Report current as of 2012, there are no water quality problems within 1 mile downstream of the Site. 2016 D. R. STRONG Consulting Engineers Inc. Page 17 The Pines Level One Downstream Analysis Renton, Washington FIGURE 5 CITY OF RENTON TOPOGRAPHY MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 18 The Pines Level One Downstream Analysis Renton, Washington FIGURE 6 CITY OF RENTON COAL MINE HAZARD AREAS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 19 The Pines Level One Downstream Analysis Renton, Washington FIGURE 7 CITY OF RENTON FLOOD HAZARDS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 20 The Pines Level One Downstream Analysis Renton, Washington FIGURE 8 CITY OF RENTON STREAMS AND WETLANDS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 21 The Pines Level One Downstream Analysis Renton, Washington FIGURE 9 CITY OF RENTON LANDSLIDE HAZARDS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 22 The Pines Level One Downstream Analysis Renton, Washington FIGURE 10 CITY OF RENTON SEISMIC HAZARD AREAS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 23 The Pines Level One Downstream Analysis Renton, Washington FIGURE 11 FEMA MAP Site (Approximate) 2016 D. R. STRONG Consulting Engineers Inc. Page 24 The Pines Level One Downstream Analysis Renton, Washington FIGURE 12 KING COUNTY IMAP DRAINAGE COMPLAINTS MAP Site 2016 D. R. STRONG Consulting Engineers Inc. Page 25 The Pines Level One Downstream Analysis Renton, Washington TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA Upon evaluation of the upstream area through examining COR topographic map (see Figure 5) and by conducting field reconnaissance on March 21st 2016, the upstream tributary area for the Site is considered negligible. Runoff from the north and east is captured by the developed single-family lots and conveyed to the existing conveyance systems located in NE 9th St and Olympia Ave NE, respectively. Runoff from the south is also collected by the developed single-family lots and conveyed to Monroe Ave NE and south away from the Site. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTIONS The Site is contained within one Threshold Discharge Area (TDA). Runoff from the Site sheet flows over the west property line to the vertical curb and gutter located on the east side of Monroe Avenue NE. Runoff then flows north via curb and gutter before being collected by one of two catch basins. Runoff from each catch basin is conveyed to the 24” diameter pipe and catch basin conveyance system within Monroe Avenue NE, which flows south towards NE 7th St. The conveyance system then turns west at NE 7th St. and continues to flow that direction for over a quarter-mile downstream of the Site. 2016 D. R. STRONG Consulting Engineers Inc. Page 26 The Pines Level One Downstream Analysis Renton, Washington TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in the Downstream Map Figure 12 and Downstream Table Figure 13. The drainage area is located within the East Lake Washington - Renton Drainage Basin. The drainage area was evaluated by reviewing available resources described in task 2, and by conducting a field reconnaissance on March 21st, 2016 under rainy conditions. DOWNSTREAM PATH 1 “A1” is the Natural Discharge Area (NDA) for path 1 from the TDA of the Site. It is located along the western property line (±0). From Point “A1” to Point “B1”, runoff continues to flow west as sheet flow over approximately 7.5 feet of till grass and a 6-inch concrete curb. No concentrated flow was observed (±0’-8’). Point “B1”, runoff is collected by the concrete gutter located along the east side of Monroe Avenue NE (±8’). From Point “B1” to Point “C1”, runoff flows north as channel flow via vertical curb and gutter. Light flow was observed (±8’-140’). Point “C1”, runoff enters a Type 1 CB, Facility ID No. 136224 (±140’). From Point “C1” to Point “D1”, runoff flows northwest as pipe flow via 8” PVC. Trickle flow was observed (±140’-154’). Point “D1”, runoff enters a Type 2 CB, Facility ID No. 136225 (±154’). From Point “D1” to Point “E1”, runoff flows west as pipe flow via 12” CPEP/LCPE. Moderate flow observed (±154’-182’). Point “E1”, runoff enters a Type 2 CB, Facility ID No. 135946 (±182’). From Point “E1” to Point “F1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±182’-403’). Point “F1”, runoff enters a Type 2 CB, Facility ID No 135945 (±403’). From Point “F1” to Point “G1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±403’-553’). Point “G1”, runoff enters a Type 2 CB, Facility ID No 135942 (±553’). From Point “G1” to Point “H1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±553’-695’). Point “H1”, runoff enters a Type 2 CB, Facility ID No 136001 (±695’). From Point “H1” to Point “I1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±695’-824’). Point “I1”, runoff enters a Type 2 CB, Facility ID No 135998 (±824’). 2016 D. R. STRONG Consulting Engineers Inc. Page 27 The Pines Level One Downstream Analysis Renton, Washington From Point “I1” to Point “J1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±824’-958’). Point “J1”, runoff enters a Type 2 CB, Facility ID No 135996 (±958’). From Point “J1” to Point “K1”, runoff flows south as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±958’-1,093’). Point “K1”, runoff enters a Type 2 CB, Facility ID No 135994. COR Maps incorrectly identifies the structure as a type 1 (±1,093’). From Point “K1” to Point “L1”, runoff flows southwest as pipe flow via 24” CPEP/LCPE. Moderate flow was observed (±1,093’-1,124’). Point “L1”, runoff enters a Type 2 CB, Facility ID No 135993 (±1,124’). From Point “L1” to Point “M1”, runoff flows westerly as pipe flow via 24” CPEP. Moderate flow was observed (±1,124’-1,238’). Point “M1”, runoff enters a Type 2 CB, Facility ID No 134697 (±1,238’). From Point “M1” to Point “N1”, runoff flows westerly as pipe flow via 24” CPEP. Moderate flow was observed (±1,238’-1,300’). Point “N1”, runoff enters a Type 2 CB, Facility ID No 134696 (±1,300’). From Point “N1” to Point “O1”, runoff flows westerly as pipe flow via 24” CPEP. Moderate flow was observed (±1,300’-1,444’). Point “O1”, runoff enters a Type 2 CB, Facility ID No 134695 (±1,444’). From Point “O1” to Point “P1”, runoff flows southwesterly as pipe flow via 24” CPEP. Moderate flow was observed (±1,444’-1,562’). Point “P1”, runoff enters a Type 2 CB, Facility ID No 134693 (±1,562’). From Point “P1” to Point “Q1”, runoff flows southwesterly as pipe flow via 24” CPEP. Moderate flow was observed (±1,562’-1,625’). Point “Q1”, runoff enters a Type 2 CB, Facility ID No 127707 located in the sidewalk (±1,625’). From Point “Q1” to Point “R1”, runoff flows southwest as pipe flow via 24” CPEP. Moderate flow was observed (±1,625’-1,678’). Point “R1”, runoff enters a Type 2 CB, Facility ID No 134691 (±1,678’). From Point “R1” to Point “S1”, runoff flows westerly as pipe flow via 24” CPEP. Moderate flow was observed (±1,678’-1,806’). Point “S1”, runoff enters a Type 2 CB, Facility ID No 134688. This concluded the quarter-mile downstream reconnaissance (±1,806’). DOWNSTREAM PATH 2 “A2” is the Natural Discharge Area (NDA) for path 2 from the TDA of the Site. It is located along the west property line of parcel 092305-9116 (±0’). 2016 D. R. STRONG Consulting Engineers Inc. Page 28 The Pines Level One Downstream Analysis Renton, Washington From Point “A2” to Point “B2”, runoff continues to flow west as sheet flow over approximately 7.5 feet of till grass and a 6-inch concrete curb. No concentrated flow was observed (±0’-8’). Point “B2”, runoff is collected by the concrete gutter located along the east side of Monroe Avenue NE (±8’). Point “B2” to Point “C2”, runoff flows north as channel flow via vertical curb and gutter. Light flow was observed (±8’-108’). Point “C2”, runoff enters a Type 1 CB, Facility ID No. 135944 (±108’). From Point “C2” to Point “F1”, runoff flows west as pipe flow via 8” PVC. Light flow was observed (±108’-134’). Point “F1”, runoff enters a Type 2 CB, Facility ID No. 135945 where runoff from downstream path 2 converges with runoff downstream path 1 (±134’). 2016 D. R. STRONG Consulting Engineers Inc. Page 29 The Pines Level One Downstream Analysis Renton, Washington TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths revealed no complaints within the last ten years. 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. A wetvault will provide flow control and basic water quality requirements for the entire Site. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction. 2016 D. R. STRONG Consulting Engineers Inc. Page 30 The Pines Level One Downstream Analysis Renton, Washington FIGURE 13 OFFSITE ANALYSIS DOWNSTREAM MAP 2016 D. R. STRONG Consulting Engineers Inc. Page 31 The Pines Level One Downstream Analysis Renton, Washington FIGURE 14 OFFSITE ANALYSIS DOWNSTREAM TABLE DOWNSTREAM PATH 1 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A1 Natural discharge area Runoff exits at the NDA along the western property line of the Site. r0’ None Observed None Anticipated No concentrated flow observed A1-B1 West sheet flow Sheet flow over till grass and 6” curb None Observed None Anticipated No concentrated flow observed B1 6” Vertical curb and gutter East side of Monroe Avenue NE r8’ None Observed None Anticipated Light flow observed B1-C1 North channel flow 6” concrete vertical curb and gutter None Observed None Anticipated Light flow observed C1 Type 1 CB Renton Facility No. 136224 ±140’ None Observed None Anticipated Light flow observed C1-D1 Northwest pipe flow 8” Ø PVC None Observed None Anticipated Light flow observed D1 Type 2 CB Renton Facility No. 136225 ±154’ None Observed None Anticipated Light flow observed D1-E1 West pipe flow 12” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed E1 Type 2 CB Renton Facility No. 135946 ±182’ None Observed None Anticipated Moderate flow observed E1-F1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed F1 Type 2 CB Renton Facility No. 135945 ±403’ None Observed None Anticipated Moderate flow observed F1-G1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed 2016 D. 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Page 32 The Pines Level One Downstream Analysis Renton, Washington G1 Type 2 CB Renton Facility No. 135942 ±553’ None Observed None Anticipated Moderate flow observed G1-H1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed H1 Type 2 CB Renton Facility No. 136001 ±695’ None Observed None Anticipated Moderate flow observed H1-I1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed I1 Type 2 CB Renton Facility No. 135998 ±824’ None Observed None Anticipated Moderate flow observed I1-J1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed J1 Type 2 CB Renton Facility No. 135996 ±958’ None Observed None Anticipated Moderate flow observed J1-K1 South pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed K1 Type 2 CB Renton Facility No. 135994 ±1,093’ None Observed None Anticipated Moderate flow observed K1-L1 Southwest pipe flow 24” Ø CPEP/LCPE None Observed None Anticipated Moderate flow observed L1 Type 2 CB Renton Facility No. 135993 ±1,124’ None Observed None Anticipated Moderate flow observed L1-M1 Westerly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed M1 Type 2 CB Renton Facility No. 134697 ±1,238’ None Observed None Anticipated Moderate flow observed M1-N1 Westerly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed N1 Type 2 CB Renton Facility No. 134696 ±1,300’ None Observed None Anticipated Moderate flow observed N1-O1 Westerly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed O1 Type 2 CB Renton Facility No. 134695 ±1,444’ None Observed None Anticipated Moderate flow observed O1-P1 Southwesterly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed 2016 D. R. STRONG Consulting Engineers Inc. Page 33 The Pines Level One Downstream Analysis Renton, Washington DOWNSTREAM PATH 2 P1 Type 2 CB Renton Facility No. 134693 ±1,562’ None Observed None Anticipated Moderate flow observed P1-Q1 Southwesterly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed Q1 Type 2 CB Renton Facility No. 134692 located in the sidewalk ±1,625’ None Observed None Anticipated Moderate flow observed Q1-R1 Southwesterly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed R1 Type 2 CB Renton Facility No. 134691 ±1,678’ None Observed None Anticipated Moderate flow observed R1-S1 Westerly pipe flow 24” Ø CPEP None Observed None Anticipated Moderate flow observed S1 Type 2 CB Renton Facility No. 134688. This was the end of the field reconnaissance at over ¼ mile downstream from the Site. ±1,806’ None Observed None Anticipated Moderate flow observed Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mi=1,320 ft Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A1 Natural discharge area Runoff exits at NDA along the western property line of parcel 092305-116. r0’ None Observed None Anticipated No concentrated flow observed A1-B1 West sheet flow Sheet flow over till grass and 6” curb None Observed None Anticipated No concentrated flow observed B1 6” Vertical curb and gutter East side of Monroe Avenue NE r8’ None Observed None Anticipated Light flow observed B1-C1 North channel flow 6” concrete vertical curb and gutter None Observed None Anticipated Light flow observed C1 Type 1 CB Renton Facility No. 135944 ±108’ None Observed None Anticipated Light flow observed 2016 D. R. STRONG Consulting Engineers Inc. Page 34 The Pines Level One Downstream Analysis Renton, Washington C1-F1 West pipe flow 8” Ø PVC None Observed None Anticipated Light flow observed F1 Type 2 CB Renton Facility No. 135945. Downstream path 2 combines with downstream path. r134’ None Observed None Anticipated No concentrated flow observed 2016 D. R. STRONG Consulting Engineers Inc. Page 35 The Pines Technical Information Report Renton, Washington SECTION IV FLOW CONTROL ANALYSIS AND WATER QUALITY DESIGN EXISTING SITE HYDROLOGY KCRTS was used to model runoff from the Site. The Site falls within the Peak Rate Flow Control Stadard area matching existing Site conditions. The Site was modeled with existing forested, pasture and impervious surfaces (see figure 15). Results of the KCRTS analysis are included in this section. Modeling Input for the TDA Pre-Developed KCRTS Modeling Input Modeling Results Flow Frequency Analysis Time Series File:predev.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 0.181 2 2/09/01 18:00 0.310 1 100.00 0.990 0.077 7 1/05/02 16:00 0.181 2 25.00 0.960 0.170 3 2/28/03 3:00 0.170 3 10.00 0.900 0.030 8 8/26/04 2:00 0.160 4 5.00 0.800 0.097 6 1/05/05 8:00 0.153 5 3.00 0.667 0.160 4 1/18/06 16:00 0.097 6 2.00 0.500 0.153 5 11/24/06 4:00 0.077 7 1.30 0.231 0.310 1 1/09/08 6:00 0.030 8 1.10 0.091 Computed Peaks 0.267 50.00 0.980 2016 D. R. STRONG Consulting Engineers Inc. Page 36 The Pines Technical Information Report Renton, Washington FIGURE 15 PREDEVELOPED AREA MAP 2016 D. R. STRONG Consulting Engineers Inc. Page 37 The Pines Technical Information Report Renton, Washington DEVELOPED SITE HYDROLOGY Soil Type The soil types are unchanged from predeveloped conditions. Land covers KCRTS was used to model the developed peak runoff from the Site. The portions of the Site within the developable area tributary to the proposed detention facility were modeled as “Till Grass”, and Impervious as appropriate. Results of the KCRTS analysis are included in this section. Modeling Input for DEV Site of the TDA Developed KCRTS Modeling Input Modeling Results Flow Frequency Analysis Time Series File: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 0.457 6 2/09/01 2:00 0.927 1 100.00 0.990 0.371 8 1/05/02 16:00 0.580 2 25.00 0.960 0.550 3 2/27/03 7:00 0.550 3 10.00 0.900 0.399 7 8/26/04 2:00 0.485 4 5.00 0.800 0.481 5 10/28/04 16:00 0.481 5 3.00 0.667 0.485 4 1/18/06 16:00 0.457 6 2.00 0.500 0.580 2 10/26/06 0:00 0.399 7 1.30 0.231 0.927 1 1/09/08 6:00 0.371 8 1.10 0.091 Computed Peaks 0.812 50.00 0.980 2016 D. R. STRONG Consulting Engineers Inc. Page 38 The Pines Technical Information Report Renton, Washington Modeling Input for the Bypass of the TDA Developed KCRTS Modeling Input Modeling Results Flow Frequency Analysis Time Series File: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 0.002 3 2/09/01 2:00 0.004 1 100.00 0.990 0.001 6 1/05/02 16:00 0.002 2 25.00 0.960 0.002 2 2/27/03 7:00 0.002 3 10.00 0.900 0.001 7 8/26/04 2:00 0.002 4 5.00 0.800 0.001 8 10/28/04 16:00 0.002 5 3.00 0.667 0.002 4 1/18/06 13:00 0.001 6 2.00 0.500 0.002 5 11/24/06 3:00 0.001 7 1.30 0.231 0.004 1 1/09/08 6:00 0.001 8 1.10 0.091 Computed Peaks 0.003 50.00 0.980 2016 D. R. STRONG Consulting Engineers Inc. Page 39 The Pines Technical Information Report Renton, Washington FIGURE 16 DEVELOPED AREA MAP 2016 D. R. STRONG Consulting Engineers Inc. Page 40 The Pines Technical Information Report Renton, Washington PERFORMANCE STANDARDS The Site is required to adhere to Level 2 Flow Control Standards of the existing site conditions (reference 11-A of COR 2009 Surface Water Design Manual Amendment). A wet-vault will provide flow control and basic water quality treatment. The Project is required to “match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10-year return periods. Assume existing site conditions as the predeveloped condition” (2009 Surface Water Design Manual Amendment, Sec. 1.2.3.1). 2016 D. R. STRONG Consulting Engineers Inc. Page 41 The Pines Technical Information Report Renton, Washington FLOW CONTROL SYSTEM The Project will utilize an detention facility designed to control site runoff. The King County Runoff Time Series (KCRTS) software was used to size the facility. The detention pond design information is included in this section. Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 56.06 ft Facility Width: 56.06 ft Facility Area: 3143. sq. ft Effective Storage Depth: 7.50 ft Stage 0 Elevation: 383.00 ft Storage Volume: 23573. cu. ft Riser Head: 7.50 ft Riser Diameter: 18.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.93 0.064 2 4.30 1.24 0.075 4.0 3 6.00 1.10 0.040 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 383.00 0. 0.000 0.000 0.00 0.01 383.01 31. 0.001 0.002 0.00 0.02 383.02 63. 0.001 0.003 0.00 0.03 383.03 94. 0.002 0.004 0.00 0.04 383.04 126. 0.003 0.005 0.00 0.05 383.05 157. 0.004 0.005 0.00 0.06 383.06 189. 0.004 0.006 0.00 0.07 383.07 220. 0.005 0.006 0.00 0.08 383.08 251. 0.006 0.006 0.00 0.22 383.22 692. 0.016 0.011 0.00 0.37 383.37 1163. 0.027 0.014 0.00 0.52 383.52 1634. 0.038 0.017 0.00 0.67 383.67 2106. 0.048 0.019 0.00 0.81 383.81 2546. 0.058 0.021 0.00 0.96 383.96 3017. 0.069 0.023 0.00 1.11 384.11 3489. 0.080 0.025 0.00 1.25 384.25 3929. 0.090 0.026 0.00 1.40 384.40 4400. 0.101 0.028 0.00 1.55 384.55 4872. 0.112 0.029 0.00 1.69 384.69 5312. 0.122 0.030 0.00 1.84 384.84 5783. 0.133 0.032 0.00 1.99 384.99 6255. 0.144 0.033 0.00 2.14 385.14 6726. 0.154 0.034 0.00 2.28 385.28 7166. 0.165 0.035 0.00 2.43 385.43 7638. 0.175 0.036 0.00 2.58 385.58 8109. 0.186 0.038 0.00 2.72 385.72 8549. 0.196 0.039 0.00 2.87 385.87 9020. 0.207 0.040 0.00 3.02 386.02 9492. 0.218 0.041 0.00 3.17 386.17 9963. 0.229 0.042 0.00 2016 D. 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Page 42 The Pines Technical Information Report Renton, Washington 3.31 386.31 10403. 0.239 0.043 0.00 3.46 386.46 10875. 0.250 0.043 0.00 3.61 386.61 11346. 0.260 0.044 0.00 3.75 386.75 11786. 0.271 0.045 0.00 3.90 386.90 12258. 0.281 0.046 0.00 4.05 387.05 12729. 0.292 0.047 0.00 4.19 387.19 13169. 0.302 0.048 0.00 4.30 387.30 13515. 0.310 0.048 0.00 4.31 387.31 13546. 0.311 0.049 0.00 4.33 387.33 13609. 0.312 0.050 0.00 4.34 387.34 13641. 0.313 0.052 0.00 4.35 387.35 13672. 0.314 0.054 0.00 4.36 387.36 13704. 0.315 0.057 0.00 4.38 387.38 13766. 0.316 0.060 0.00 4.39 387.39 13798. 0.317 0.062 0.00 4.40 387.40 13829. 0.317 0.063 0.00 4.42 387.42 13892. 0.319 0.063 0.00 4.56 387.56 14332. 0.329 0.071 0.00 4.71 387.71 14804. 0.340 0.078 0.00 4.86 387.86 15275. 0.351 0.083 0.00 5.00 388.00 15715. 0.361 0.087 0.00 5.15 388.15 16187. 0.372 0.092 0.00 5.30 388.30 16658. 0.382 0.096 0.00 5.45 388.45 17129. 0.393 0.099 0.00 5.59 388.59 17569. 0.403 0.103 0.00 5.74 388.74 18041. 0.414 0.106 0.00 5.89 388.89 18512. 0.425 0.110 0.00 6.00 389.00 18858. 0.433 0.112 0.00 6.01 389.01 18889. 0.434 0.112 0.00 6.02 389.02 18921. 0.434 0.113 0.00 6.03 389.03 18952. 0.435 0.115 0.00 6.05 389.05 19015. 0.437 0.117 0.00 6.06 389.06 19047. 0.437 0.119 0.00 6.07 389.07 19078. 0.438 0.122 0.00 6.08 389.08 19110. 0.439 0.123 0.00 6.09 389.09 19141. 0.439 0.124 0.00 6.10 389.10 19172. 0.440 0.125 0.00 6.25 389.25 19644. 0.451 0.133 0.00 6.40 389.40 20115. 0.462 0.141 0.00 6.54 389.54 20555. 0.472 0.147 0.00 6.69 389.69 21027. 0.483 0.153 0.00 6.84 389.84 21498. 0.494 0.158 0.00 6.99 389.99 21970. 0.504 0.163 0.00 7.13 390.13 22410. 0.514 0.168 0.00 7.28 390.28 22881. 0.525 0.173 0.00 7.43 390.43 23353. 0.536 0.177 0.00 7.50 390.50 23573. 0.541 0.179 0.00 7.60 390.60 23887. 0.548 0.644 0.00 7.70 390.70 24201. 0.556 1.490 0.00 7.80 390.80 24515. 0.563 2.590 0.00 7.90 390.90 24830. 0.570 3.890 0.00 8.00 391.00 25144. 0.577 5.360 0.00 8.10 391.10 25458. 0.584 6.790 0.00 8.20 391.20 25773. 0.592 7.320 0.00 8.30 391.30 26087. 0.599 7.810 0.00 8.40 391.40 26401. 0.606 8.280 0.00 8.50 391.50 26716. 0.613 8.720 0.00 8.60 391.60 27030. 0.621 9.130 0.00 8.70 391.70 27344. 0.628 9.530 0.00 8.80 391.80 27658. 0.635 9.920 0.00 8.90 391.90 27973. 0.642 10.280 0.00 9.00 392.00 28287. 0.649 10.640 0.00 9.10 392.10 28601. 0.657 10.980 0.00 2016 D. 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Page 43 The Pines Technical Information Report Renton, Washington 9.20 392.20 28916. 0.664 11.320 0.00 9.30 392.30 29230. 0.671 11.640 0.00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.93 0.78 7.62 390.62 23938. 0.550 2 0.46 0.18 7.50 390.50 23569. 0.541 3 0.46 0.15 6.67 389.67 20978. 0.482 4 0.49 0.11 5.89 388.89 18516. 0.425 5 0.55 0.11 5.82 388.82 18285. 0.420 6 0.29 0.07 4.54 387.54 14256. 0.327 7 0.37 0.04 3.65 386.65 11477. 0.263 8 0.40 0.04 2.84 385.84 8916. 0.205 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.78 0.00 ******** ******* 0.78 2 0.18 0.00 ******** 0.18 0.18 3 0.15 0.00 ******** ******* 0.15 4 0.11 0.00 ******** ******* 0.11 5 0.11 0.00 ******** ******* 0.11 6 0.07 0.00 ******** ******* 0.07 7 0.04 0.00 ******** ******* 0.04 8 0.04 0.00 ******** ******* 0.04 ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.927 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.783 CFS at 9:00 on Jan 9 in Year 8 Peak Reservoir Stage: 7.62 Ft Peak Reservoir Elev: 390.62 Ft Peak Reservoir Storage: 23938. Cu-Ft : 0.550 Ac-Ft Add Time Series:bypass.tsf Peak Summed Discharge: 0.786 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 0.179 2 2/09/01 20:00 0.783 7.62 1 100.00 0.990 0.044 7 12/28/01 18:00 0.179 7.50 2 25.00 0.960 0.108 5 3/06/03 22:00 0.152 6.67 3 10.00 0.900 0.040 8 8/26/04 7:00 0.110 5.89 4 5.00 0.800 0.070 6 1/05/05 16:00 0.108 5.82 5 3.00 0.667 0.110 4 1/18/06 23:00 0.070 4.54 6 2.00 0.500 0.152 3 11/24/06 7:00 0.044 3.65 7 1.30 0.231 0.783 1 1/09/08 9:00 0.040 2.84 8 1.10 0.091 Computed Peaks 0.581 7.59 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- 2016 D. R. STRONG Consulting Engineers Inc. Page 44 The Pines Technical Information Report Renton, Washington Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.180 2 2/09/01 20:00 0.786 1 100.00 0.990 0.045 7 12/28/01 18:00 0.180 2 25.00 0.960 0.108 5 3/06/03 22:00 0.153 3 10.00 0.900 0.040 8 8/26/04 7:00 0.111 4 5.00 0.800 0.070 6 1/05/05 15:00 0.108 5 3.00 0.667 0.111 4 1/18/06 23:00 0.070 6 2.00 0.500 0.153 3 11/24/06 7:00 0.045 7 1.30 0.231 0.786 1 1/09/08 9:00 0.040 8 1.10 0.091 Computed Peaks 0.584 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.003 36753 59.936 59.936 40.064 0.401E+00 0.008 5555 9.059 68.995 31.005 0.310E+00 0.013 4662 7.603 76.598 23.402 0.234E+00 0.018 4005 6.531 83.129 16.871 0.169E+00 0.023 3566 5.815 88.945 11.055 0.111E+00 0.028 2379 3.880 92.825 7.175 0.718E-01 0.033 1596 2.603 95.427 4.573 0.457E-01 0.038 1079 1.760 97.187 2.813 0.281E-01 0.043 733 1.195 98.382 1.618 0.162E-01 0.048 530 0.864 99.247 0.753 0.753E-02 0.053 166 0.271 99.517 0.483 0.483E-02 0.058 19 0.031 99.548 0.452 0.452E-02 0.063 16 0.026 99.574 0.426 0.426E-02 0.068 39 0.064 99.638 0.362 0.362E-02 0.073 21 0.034 99.672 0.328 0.328E-02 0.078 15 0.024 99.697 0.303 0.303E-02 0.083 16 0.026 99.723 0.277 0.277E-02 0.088 18 0.029 99.752 0.248 0.248E-02 0.093 17 0.028 99.780 0.220 0.220E-02 0.098 22 0.036 99.816 0.184 0.184E-02 0.103 27 0.044 99.860 0.140 0.140E-02 0.108 27 0.044 99.904 0.096 0.962E-03 0.113 18 0.029 99.933 0.067 0.669E-03 0.118 2 0.003 99.936 0.064 0.636E-03 0.123 2 0.003 99.940 0.060 0.603E-03 0.128 4 0.007 99.946 0.054 0.538E-03 0.133 3 0.005 99.951 0.049 0.489E-03 0.138 3 0.005 99.956 0.044 0.440E-03 0.143 4 0.007 99.962 0.038 0.375E-03 0.148 3 0.005 99.967 0.033 0.326E-03 0.153 6 0.010 99.977 0.023 0.228E-03 0.158 2 0.003 99.980 0.020 0.196E-03 0.163 2 0.003 99.984 0.016 0.163E-03 0.168 2 0.003 99.987 0.013 0.130E-03 0.173 3 0.005 99.992 0.008 0.815E-04 0.178 4 0.007 99.998 0.002 0.163E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.003 36730 59.899 59.899 40.101 0.401E+00 0.008 5529 9.017 68.916 31.084 0.311E+00 0.013 4828 7.873 76.789 23.211 0.232E+00 0.018 3960 6.458 83.247 16.753 0.168E+00 0.023 3497 5.703 88.950 11.050 0.111E+00 0.028 2366 3.858 92.808 7.192 0.719E-01 0.033 1589 2.591 95.400 4.600 0.460E-01 0.038 1085 1.769 97.169 2.831 0.283E-01 2016 D. R. STRONG Consulting Engineers Inc. Page 45 The Pines Technical Information Report Renton, Washington 0.043 729 1.189 98.358 1.642 0.164E-01 0.048 556 0.907 99.265 0.735 0.735E-02 0.053 155 0.253 99.517 0.483 0.483E-02 0.058 19 0.031 99.548 0.452 0.452E-02 0.063 16 0.026 99.574 0.426 0.426E-02 0.068 39 0.064 99.638 0.362 0.362E-02 0.073 20 0.033 99.671 0.329 0.329E-02 0.078 17 0.028 99.698 0.302 0.302E-02 0.083 16 0.026 99.724 0.276 0.276E-02 0.088 17 0.028 99.752 0.248 0.248E-02 0.093 15 0.024 99.777 0.223 0.223E-02 0.098 24 0.039 99.816 0.184 0.184E-02 0.103 26 0.042 99.858 0.142 0.142E-02 0.108 26 0.042 99.901 0.099 0.995E-03 0.113 20 0.033 99.933 0.067 0.669E-03 0.118 1 0.002 99.935 0.065 0.652E-03 0.123 3 0.005 99.940 0.060 0.603E-03 0.128 5 0.008 99.948 0.052 0.522E-03 0.133 1 0.002 99.949 0.051 0.506E-03 0.138 4 0.007 99.956 0.044 0.440E-03 0.143 3 0.005 99.961 0.039 0.391E-03 0.148 4 0.007 99.967 0.033 0.326E-03 0.153 6 0.010 99.977 0.023 0.228E-03 0.158 2 0.003 99.980 0.020 0.196E-03 0.164 2 0.003 99.984 0.016 0.163E-03 0.169 2 0.003 99.987 0.013 0.130E-03 0.174 3 0.005 99.992 0.008 0.815E-04 0.179 4 0.007 99.998 0.002 0.163E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.048 | 0.77E-02 0.58E-02 -24.6 | 0.77E-02 0.048 0.048 -1.3 0.059 | 0.57E-02 0.45E-02 -20.7 | 0.57E-02 0.059 0.048 -17.2 0.069 | 0.45E-02 0.36E-02 -19.7 | 0.45E-02 0.069 0.059 -14.4 0.079 | 0.33E-02 0.30E-02 -8.5 | 0.33E-02 0.079 0.073 -6.9 0.089 | 0.25E-02 0.24E-02 -2.0 | 0.25E-02 0.089 0.089 -0.4 0.099 | 0.18E-02 0.17E-02 -2.7 | 0.18E-02 0.099 0.099 -0.5 0.109 | 0.13E-02 0.90E-03 -30.4 | 0.13E-02 0.109 0.104 -4.6 0.120 | 0.95E-03 0.65E-03 -31.0 | 0.95E-03 0.120 0.108 -9.3 0.130 | 0.65E-03 0.52E-03 -20.0 | 0.65E-03 0.130 0.120 -7.8 0.140 | 0.46E-03 0.44E-03 -3.6 | 0.46E-03 0.140 0.138 -1.6 0.150 | 0.23E-03 0.29E-03 28.6 | 0.23E-03 0.150 0.154 2.3 0.160 | 0.16E-03 0.20E-03 20.0 | 0.16E-03 0.160 0.165 3.2 0.170 | 0.49E-04 0.11E-03 133.3 | 0.49E-04 0.170 0.178 4.5 0.181 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.181 0.179 -0.7 Maximum positive excursion = 0.010 cfs ( 6.3%) occurring at 0.152 cfs on the Base Data:predev.tsf and at 0.161 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.014 cfs (-21.5%) occurring at 0.064 cfs on the Base Data:predev.tsf and at 0.050 cfs on the New Data:dsout.tsf 2016 D. R. STRONG Consulting Engineers Inc. Page 46 The Pines Technical Information Report Renton, Washington 2016 D. R. STRONG Consulting Engineers Inc. Page 47 The Pines Technical Information Report Renton, Washington WATER QUALITY TREATMENT SYSTEM The Project is required to adhere to the City of Renton’s Basic Water Quality treatment criteria. A combined detention/water quality vault located within Tract B is proposed to accommodate this requirement. Preliminary sizing for a wetvault was calculated from the formula provided by Section 6.4.1.1 Methods of Analysis of the Manual. The minimum wetpool volume required is 8,282 cubic feet. The Project will provide 15,520 cubic feet of dead storage. 2016 D. R. STRONG Consulting Engineers Inc. Page 48 The Pines Technical Information Report Renton, Washington FIGURE 17 DETENTION & WATER QUALITY FACILITY DETAILS (To be completed at time of final engineering) 2016 D. R. STRONG Consulting Engineers Inc. Page 49 The Pines Technical Information Report Renton, Washington SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per Core Requirement #4 of the KCSWDM, the conveyance system must be analyzed and designed for the existing tributary and developed onsite runoff. Pipe systems shall be designed to convey the 100-year design storm. The Rational Method will be used to calculate the Q-Ratio for each pipe node. A conveyance system consisting primarily of pipes and catch basins will be designed for the Project. Onsite runoff will be collected by the multiple catch basins. Pipes are typically eight-inch to twelve-inch diameter LCPE material. A backwater analysis will be provided at time of final engineering. 2016 D. R. STRONG Consulting Engineers Inc. Page 50 The Pines Technical Information Report Renton, Washington SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies have been provided with this submittal. Wetland Memo: Re-Align Environmental – April 21st, 2016 Geotechnical Engineering Study: Earth Solutions NW, LLC – April 27, 2016 Traffic Memorandum: Gibson Traffic Consultants, Inc. – May 9, 2016 2016 D. R. STRONG Consulting Engineers Inc. Page 51 The Pines Technical Information Report Renton, Washington SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS x Hammerhead turnaround approval at the end of internal Road A, by Corey Thomas, dated April 6, 2016. 2016 D. R. STRONG Consulting Engineers Inc. Page 52 The Pines Technical Information Report Renton, Washington SECTION VIII CSWPPP ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design will meet the seven minimum King County requirements: 1. Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Site disturbed areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. A stabilized construction entrance will be located at the point of ingress/egress (i.e. onsite access road). 5. The detention pond will act as a sediment pond for sediment retention. Perimeter silt fences will provide sediment retention within the bypass areas. 6. Surface water from disturbed areas will sheet flow to the sediment pond for treatment. 7. Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. SWPPP PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP’s listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash-up waters from water-based paints in sanitary sewer; disposing of wastes from oil-based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 2016 D. R. STRONG Consulting Engineers Inc. Page 53 The Pines Technical Information Report Renton, Washington 3. Building demolition: Protect stormwater drainage system from sediment-laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP will be completed and submitted at time of final of engineering. 2016 D. R. STRONG Consulting Engineers Inc. Page 54 The Pines Technical Information Report Renton, Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – will be submitted at final engineering 2. The Stormwater Facility Summary Sheet is included in this section 2016 D. R. STRONG Consulting Engineers Inc. Page 55 The Pines Technical Information Report Renton, Washington STORMWATER FACILITY SUMMARY SHEET Development The Pines Date June 6, 2016 Location: 850 & 870 Monroe Ave NE, Renton, Washington 98056 ENGINEER DEVELOPER Name Yoshio L Piediscalzi, P.E. Name Jamie Waltier Firm D. R. STRONG Consulting Engineers, Inc. Firm Harbour Homes, LLC Address 620 7th Avenue Address 400 North 34th St, Suite 300 Kirkland, WA 98033 Seattle, WA 98103 Phone (425) 827-3063 Phone (206) 315-8130 Developed Site: 2.509 acres Number of lots: 14 Number of detention facilities on site: Number of infiltration facilities on site: ___1__ vaults ______ vaults ______ pond ______ ponds ______ tanks ______ tanks Flow control provided in regional facility (give location)___________________________ No flow control required_____ Exemption number ______________________________ Downstream Drainage Basins Immediate Major Basin Basin Renton East Lake Washington Number & type of water quality facilities on site: biofiltration swale (regular/wet/ or continuous inflow?) ______ sand filter (basic or large?) ______ sand filter, linear (basic or large?) ______ CONTECH Stormfilter __1___ combined detention/WQ vault ______ sand filter vault (basic or large?) ______ combined detention/wetpond ______ stormwater wetland ______ compost filter ______ wetvault (basic or large?) ______ filter strip ______ Wetvault ______ flow dispersion ______ pre-settling pond ______ farm management plan ______ flow-splitter catchbasin ______ landscape management plan ______ oil/water separator (baffle or coalescing plate?) ______ catch basin inserts: Manufacturer____________________________________________ ______ pre-settling structure: Manufacturer__________________________________________ 2016 D. R. STRONG Consulting Engineers Inc. Page 56 The Pines Technical Information Report Renton, Washington DESIGN INFORMATION INDIVIDUAL BASIN Water Quality design flow Water Quality treated volume Drainage basin(s) 1 Onsite area (includes frontage) 2.4424 Offsite area 0.0668 Type of Storage Facility Detention Vault Live Storage Volume (required) 23,573 Predev Runoff Rate 2-year 0.097 10-year 0.170 100-year 0.310 Developed Runoff Rate 2-year 0.070 (includes bypass) 10-year 0.153 100-year 0.786 Type of Restrictor Size of orifice/restriction No. 1 0.93‖ Ø 0.00’ No. 2 1.24‖ Ø 4.30’ No. 3 1.10‖ Ø 6.00’ 2016 D. R. STRONG Consulting Engineers Inc. Page 57 The Pines Technical Information Report Renton, Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL Excerpts from the 2009 KCSWDM will be provided at final engineering. 2016 D. R. STRONG Consulting Engineers Inc. Page 58 The Pines Technical Information Report Renton, Washington APPENDICES 2016 D. R. STRONG Consulting Engineers Inc. Page 59 The Pines Technical Information Report Renton, Washington APPENDIX ―A‖ LEGAL DESCRIPTION THE SOUTH 2 ACRES OF THE NORTH 4 ACRES OF THE SOUTHWEST QUARTER OF THE SOUTHWEST QUARTER OF THE NORTHEAST QUARTER OF SECTION 9, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON; EXCEPT THE EAST 130 FEET THEREOF; AND EXCEPT THE WEST 30 FEET FOR MONROE AVENUE N.E.; ALSO THE NORTH 2 ACRES OF THE SOUTHWEST QUARTER OF THE SOUTHWEST QUARTER OF THE NORTHEAST QUARTER OF SECTION 9, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON; EXCEPT THE WEST 30 FEET FOR COUNTY ROAD; EXCEPT THE EAST 130 FEET THEREOF; AND EXCEPT THE NORTH 48 FEET.