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Home My WebLink AboutFULL RPT Renton Highlands 2-BASINS TIR 11-14-24Deccio Engineering Inc. 17217 7th Avenue W. Bothell, WA. 98012 (206) 390-8374 Fax: (425) 741-8214 Renton Highland 6-Lot Short Plat LUA24-000078 Drainage Design Report, O&M Manual & SWPP Report Property Location: 5815 NE 8th Street Renton, WA October 20, 2023 Revised: February 14, 2024 Revised: October 14, 2024 Revised: October 22, 2024 Revised: November 14, 2024 Prepared for: Sazei Design Group LLC 11/14/2024 Deccio Engineering Inc Page i TABLE OF CONTENTS SECTION 1 PROJECT OVERVIEW 1 o Figure 1: TIR Worksheet 2 o Figure 2: Site Location Map 7 o Figure 3: Existing Site Characteristic, Drainage Basins, and Sub-Basins 8 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY 10  King County Requirements SECTION 3 OFF-SITE ANALYSIS 13  Sensitive Areas Map 14  Drainage Complaint Map 15 o Figure 4: Upstream and Downstream Flow Map 15 o Figure 5: Downstream System Table 16 SECTION 4 FLOW CONTROL & WATER QUALITY ANALYSIS AND DESIGN 15 o Figure 6: Soils Logs 16 o Figure 7: Developed Conditions Map 16 o Infiltration Requirements 17 o Soil Management Plan 18 SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 21 SECTION 6 SPECIAL REPORTS AND STUDIES 33 SECTION 7 OTHER PERMITS 33 SECTION 8 SWPPP ANALYSIS AND DESIGN 33 SECTION 9 BONDS, SUMMARIES AND COVENANTS 37 SECTION 10 OPERATIONS AND MAINTENANCE MANUAL 38  Operations and Maintenance Procedures Appendix A Pipe Conveyance Charts Pump Charts WWHM12 Results Pit Infiltration Report Renton Highlands 6-Lot SP TIR Revised November 14, 2024 1 | Page TIR SECTION 1 PROJECT OVERVIEW Project: Renton Highlands 6-Lot short plat Site Information: The proposed project is the construction of a six lot short plat. The site is located at 5815 NE 8th Street More generally the site is located within SW ¼ of Section 11, Township 23 North, Range 05 East, W.M., (Parcel# 1123059068) see Figure 2: Vicinity Map. The site is bordered by residential properties on the north, south, east, and west sides of the site. Pre-developed Site Conditions: The site is 84,070 sf in size, is vacant with a cover of trees. The lot is split into two sub-basins with runoff leaving the site to the south for Sub-basin 1 and to the west then north for Subbasin 2. The lot is flat with slopes less that 2%. There are no known sensitive areas on-site. Please refer to Figure 3: Existing Conditions Map.. Developed Site Conditions: The project will consist of construction of a 6-lot short plat with the average lot size of 9,000 sf. Drainage from Sub-basin 1 (Lots 1 to 4) will drain to an onsite vault for storage and discharge. The drainage from Sub-basin 2 (Lots 5 &6) will be disbursed using basic dispersion and partial infiltration. Half street frontage improvement will be required on Pasco Place NE consisting of curbs, gutters and sidewalks. The city is only requiring a sidewalk fronting NE 8th street. Flow control for Sub-basin 1, will be provided in the form of a closed detention vault. The site will be served by public water and sewer. Please refer to Figure 7: Developed Conditions Map The total PGHS area for Sub-basin 2 is over 5,000 requiring enhanced basic water quality in the form of a Filterra filter system. Renton Highlands 6-Lot SP TIR Revised November 14, 2024 2 | Page Figure 1: TIR Worksheet Renton Highlands 6-Lot SP TIR Revised November 14, 2024 3 | Page Figure 1: TIR Worksheet Renton Highlands 6-Lot SP TIR Revised November 14, 2024 4 | Page Figure 1: TIR Worksheet Renton Highlands 6-Lot SP TIR Revised November 14, 2024 5 | Page Figure 1: TIR Worksheet filterra Renton Highlands 6-Lot SP TIR Revised November 14, 2024 6 | Page Figure 1: TIR Worksheet Renton Highlands 6-Lot SP TIR Revised November 14, 2024 7 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 8 | Page Figure 2: Site Location Map Renton Highlands 6-Lot SP TIR Revised November 14, 2024 9 | Page Figure 3: Drainage Basins, Sub-basins and Site Characteristics Renton Highlands 6-Lot SP TIR Revised November 14, 2024 10 | Page TIR SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY The City of Renton has adopted the City of Renton 2022 storm water manual which governs the design of stormwater systems to serve this project. The Core and Special Requirements are being met in the following manner: City of Renton 2022 Storm Water Manual Core Requirements: 1. Discharge at the Natural Location Under 1.2.1-2, The surveyed contours show the site is contained within two subbasins: Sub-Basin 1 drains to the south and Sub-basin 2 drains to the west, then north. Each sub- basin will drain to its current location thereby maintain the natural discharge location 2. Off-site Analysis The Level 1 downstream analysis showed that there will be minimal impacts on the downstream conditions for both basins, since the site proposes to use detention and basic dispersion to address all stormwater runoff. 3. Flow Control The site will meet the flow control standards using on-site detention in the form of a detention vault and on site BMPs. 4. Conveyance System Sub-Basin 1: The site is using catch basins and 12” storm pipe to collect the on-site runoff sending it to the detention vaults which discharge it to an existing 12-inch storm pipe located at the south end of Pasco Street. Sub-Basin 2: The site is using BMPs for runoff dispersion, therefor there are no pipes or conveyance systems other than the roof drains. 5. Temporary Erosion & Sediment Control All TESC measures proposed will conform to the 2022 Renton Stormwater Manual during construction. Refer to Section 9 of this TIR for additional information. The measures shown on the TESC plans include: Clearing limits, sediment control, soil stabilization, BMP’s maintenance and construction sequence 6. Maintenance & Operations Maintenance and Operations manual has been provided at the back of this report. Note that a “Declaration of Covenant” may be required. See Section 10. 7. Financial Guarantees & Liability A completed bond quantity worksheet maybe required 8. Water Quality The total PGHS area is over 5,000 sf and therefore, water quality in the form a Contech Filterra system is proposed to meet the enhanced basic treatment requirement. Refer to Section 4 of this report. Renton Highlands 6-Lot SP TIR Revised November 14, 2024 11 | Page 9. Flow Control BMP’s Both basins were was reviewed for Flow Control. Sub-Basin 1 will use detention and porous pavement. Sub-basin 2 will use partial infiltration and dispersion on-site BMP’s (see review of BMP’s Below) City of Renton 2022 storm water manual Special Requirements: 1. Other Adopted Area-Specific Requirements There are no area-specific requirements for this project site. 2. Floodplain/Floodway Delineation A review of the FEMA FIRM panels for the site, shows that the site and area of work is outside any floodplain areas and site does not contain any floodplain/floodway delineations. 3. Flood Protection Facilities There are no flood protection facilities located on or directly adjacent to the site. 4. Source Control The final site does not meet the threshold for source control requirements. 5. Oil Control The final site does not meet the threshold for oil control requirements. 6. Aquifer Protection Area None known. REVIEW OF BMP’S SUB-BASIN #1 ROOFS: 1. Full Dispersion in accordance with BMP T5.30 is infeasible because a 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. Downspout Full Infiltration Systems in accordance with BMP T5.10A is infeasible. Per the Geotech report from Ages Engineering the lots on Sub- basin 1 are not suitable for infiltration . 2. Rain Gardens in accordance with BMP T5.14A and Bioretention in accordance with Chapter 7 is infeasible since the soils consist of dense to very dense sand/silt at 1 to 4 feet as noted by the geotechnical engineer and there is no positive outfall for the BMP.. 3. Downspout Dispersion Systems in the form of dispersion trenches in accordance with BMP T5.10B are not feasible since the site cannot meet the required flow paths. 4. Perforated Sub-out Connection will be used Renton Highlands 6-Lot SP TIR Revised November 14, 2024 12 | Page Other Hard Surfaces: 1. Full Dispersion in accordance with BMP T5.30 in Volume V, Chapter 5 of this manual. Is not feasible since site cannot meet the 100-ft flow paths for the site. 2. Permeable pavement in accordance with BMP T5.15 in Chapter 5 of Volume V, (Permeable Pavement will be used on the driveways.) SUB-BASIN #2 ROOFS: 1. Full Dispersion in accordance with BMP T5.30 is infeasible because a 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. Downspout Full Infiltration Systems in accordance with BMP T5.10A is A PIT test supporting a design infiltration rate of 1.22-inch/hour is proposed for 3,000 sf of roof area for Lots 5 and 6. This will reduce the net runoff to under 0.15 cfs and allow the use of the remaining BMPS 2. Rain Gardens in accordance with BMP T5.14A and Bioretention in accordance with Chapter 7 is infeasible since the site is to flat with no positive outfall. 3. Downspout Dispersion Systems in the form of splash blocks with 100-ft flow paths in accordance with BMP T5.10B (will be used for the roof areas.) 4. Perforated Sub-out Connection N/A Other Hard Surfaces: 1. Full Dispersion in accordance with BMP T5.30 in Volume V, Chapter 5 of this manual. Is not feasible since site cannot meet the 100-ft flow paths for the site. 2. Permeable pavement in accordance with BMP T5.15 in Chapter 5 of Volume V, (Permeable Pavement will be used on the driveways.) City of Renton Conditions FINDINGS/CONCLUSIONS: To be determined Renton Highlands 6-Lot SP TIR Revised November 14, 2024 13 | Page TIR SECTION 3 OFF-SITE ANALYSIS TASK 1 – STUDY AREA DEFINITIONS AND MAPS Overview This section of the TIR is a Level 1 Downstream Analysis per the City of Renton 2022 storm water manual Section 2.3. The site is 84,070 sf in size and contains an existing cover of trees and landscaping . Upstream Drainage Analysis / Upstream Contributing Area Based on the site contours, all upstream off-site runoff is intercepted by NE 8th Street, therefore there is little if any off-site runoff enters onto the site. TASK 2 – RESOURCE REVIEW Adopted Basin Plan The site is located in two sub-basins, the May Creek Sub-basin and the Cedar River/Lake Washington Basin Basin Reconnaissance Summary Report We are not aware of a current Basin Reconnaissance Summary Report for this area. Critical Drainage Area The site is not considered to be within a critical drainage area as defined by the City of Renton 2022 storm water manual A review of the DOE “water quality assessment” web site shows that the section of the site discharges into is not on the DOE 303(d) list. Sensitive Area Maps Per City of Renton the site does not contain any sensitive areas.. Soils Survey The Geotech report prepared for the site, shows the soils to be a dense sand-silt Wetland / Stream Inventory There are no wetlands or stream noted A review of the FEMA FIRM panels for the site, shows that the site is outside any floodplain areas and site does not contain any floodplain/floodway delineations. Drainage Complaints There appeared to be 14-drainage complaints downstream of the two sub-basins, and all were closed by 2006. (See “Drainage Complaints Map”) Renton Highlands 6-Lot SP TIR Revised November 14, 2024 14 | Page TASK 3 – FIELD INSPECTION A Level 1 site inspection was performed on October 10, 2023. The weather was clear. The inspection focused on identifying potential downstream drainage and water quality problems SUB-BASIN #1 As previously indicated, the site slopes from north to south with all runoff leaving the site and discharging onto the adjacent property to the south. TASK 4 – DRAINAGE SYSTEM DESCRIPTION, AND PREDICTED DRAINAGE AND WATER QUALITY PROBLEMS OFFSITE LEVEL ONE DOWNSTREAM ANALYSIS 1. The runoff leaves the site and flows into the storm system on NE 7th Place where it flows west for 700 feet to Nile Avenue NE and flows south for a distance of 2,200. At the intersection of Nile Ave NE and ne 4th street the drainage turns and flows west in the storm drainage system serving NE 4th street for a distance of over 1,300 feet. The total distance covered is just under 1-mile Sub-Basin 1 Predicted Drainage and Water Quality Problems There appeared to be no issues downstream and since detention is provided for the site improvements, the proposed project should have little if any impact on downstream conditions. TASK 5 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS The project proposes to provided detention and water quality to address the storm water runoff from the proposed site improvements, thus mitigating any downstream impacts. SUB-BASIN #2 As previously indicated, Lots 5 and 6 slope from east to west with all runoff leaving the site and discharging onto the adjacent property to the south. The drainage from NE 8th flows west to Nile Ave NE. TASK 4 – DRAINAGE SYSTEM DESCRIPTION, AND PREDICTED DRAINAGE AND WATER QUALITY PROBLEMS OFFSITE LEVEL ONE DOWNSTREAM ANALYSIS 1. The runoff leaves the site flows overland to the west for 300-ft and into the storm system serving Nile Avenue NE where it is joined by the runoff from NE 8th Street, where it turns and flows north for a distance of 1,300 feet to SE 117th Street. At this intersection of the drainage flows the to west and discharges into a wetlands were it then flows north-west in an unnamed stream for a distance of over 3,200 feet. The total distance covered is just under 1-mile Renton Highlands 6-Lot SP TIR Revised November 14, 2024 15 | Page Note: There were no indications of issues noted. Where visible the stream channel appeared to be in good condition and well vegetated. However, most of the downstream was on private property and not accessible to inspection. Sub-Basin 2 Predicted Drainage and Water Quality Problems There appeared to be no issues downstream and since basic dispersion is proposed for the site improvements, the proposed project should have little if any impact on downstream conditions. TASK 5 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS The project proposes to use dispersion to address storm water runoff from the proposed site improvements, thus mitigating any downstream impacts Renton Highlands 6-Lot SP TIR Revised November 14, 2024 16 | Page Figure 5: Upstream Area and Downstream Flow Map Renton Highlands 6-Lot SP TIR Revised November 14, 2024 17 | Page Figure 6: Downstream System Table Renton Highlands 6-Lot SP TIR Revised November 14, 2024 18 | Page Drainage Complaints Renton Highlands 6-Lot SP TIR Revised November 14, 2024 19 | Page 1) Complaint number 2009-0889 Complaint type FI Date received Problem REM Date closed 12/30/2009 Address 11840 148TH AVE SE 2) Complaint number 2000-0528 Complaint type FCC Date received Problem MMG Date closed 8/29/2000 3) Complaint number 2001-0027 Complaint type C Date received Problem DDM Date closed 2/2/2001 4) Complaint number 1994-1000 Complaint type RN Date received Problem FLOODING Date closed 3/21/1995 Address 11615 148TH AVE SE Parcel 1023059390 Comments LACK OF CONVEYANCE THROUGH PVT PROP 5) Complaint number 1995-0009 Complaint type C Date received Problem EROSION Date closed 1/24/1995 6) Complaint number 1996-0552 Complaint type R Date received Problem FLDG Date closed 4/8/1996 7) Complaint number 1996-0185 Complaint type C Date received Problem FLDG Date closed 2/26/1996 Renton Highlands 6-Lot SP TIR Revised November 14, 2024 20 | Page 8) Complaint number 1989-0150 Complaint type C Date received Problem DRNG/ERO Date closed 3/24/1989 9) Complaint number 1988-0790 Complaint type C Date received Problem DRNG Date closed 1/24/1989 10) Complaint number 1999-0151 Complaint type C Date received Problem DRAINAGE Date closed 3/8/1999 11) Complaint number 1989-0776 Complaint type C Date received Problem FLDG Date closed 2/22/1990 12) Complaint number 1995-0104 Complaint type C Date received Problem H2OLEVEL Date closed 2/14/1995 13) Complaint number 1996-0323 Complaint type C Date received Problem WETLAND Date closed 2/26/1996 Address 12227 148TH AVE S 14) Complaint number 2006-0515 Complaint type C Date received Problem RFN Date closed 8/30/2006 15) Complaint number 1996-0880 Complaint type WQC Date received Problem EROSION Date closed 12/3/2008 Renton Highlands 6-Lot SP TIR Revised November 14, 2024 21 | Page TIR SECTION 4 FLOW CONTROL & WATER QUALITY ANALYSIS AND DESIGN SUB-BASIN #1 The WWHM Ver.12 Hydraulic Simulation Model was used to calculate the pre-developed and developed flows for the Hydrographs for the 2-year and 50-year, 24-hour duration design storm events for the existing and developed conditions. Pump System: In lieu of using the standard control structure design, the vault was sized using SSD (stage-storage-discharge) input tables to size the pumps to release 50-percent of the 2-year peak flow through the 50-year flow in order to provide the required detention for the developed site runoff. The hydrographs were generated using the following information: WWHM12 Input Information • Regional Gage Station: SeaTac • Precip Scale: 1.00 • Soils Type: Till Sub-Basin-1: Existing Site Hydrology The Sub-Basin is 1.51 acres in size The WWHM12 runoff was calculated using existing forested conditions to determine the total allowable release rate from the Existing Site. (See Figure 3: “Existing Site Conditions”). The site soils are identified as Till Type C,. Existing Area: 1. Onsite Area 1.51 acres (forested) Total Area: 1.51 Acres Sub-Basin: Developed Site Hydrology The runoff from the developed site conditions including roof areas, driveways, and landscaping, will be collected and conveyed in catch basins and pipes to the storm water detention vault located in the along the south side of the site. Discharge from the site will be pumped up and into an existing storm pipe system located on Pasco Place. (See Figure 6: “Developed Site Conditions”) The total area to be detained 1.51 acres. It is assumed that each lot will have 4,000 of impervious area (3,400 sf roof & 600 sf driveways) Renton Highlands 6-Lot SP TIR Revised November 14, 2024 22 | Page Impervious Areas: Developed Sub-Basin  New Roofs: 4 Total (3,400 sf each) 0.310 acres  Driveways (600 sf each) 0.055 acres  Pasco Place Pavement: 0.160 acres  Side Walks: 0.050 acres  Tract Access Drive: 0.136 acres Total Impervious Area: 0.711 acres (Impervious) Pervious Area:  Lawn Area/Landscape: Pervious 0.799 acres Total Pervious Area: 0.799 acres (Lawn/Landscape) Total Site Area: 1.51 acres Results of WWHM12 Computer Analysis: Storm Event Mitigated. Site Predev. Site • 2-year, return period: 0.018138 cfs 0.030877 cfs • 50-year, return period: 0.073620 cfs 0.085596 cfs • 100-year, return period: 0.092800 cfs 0.095251 cfs The runoff from the site improvements will be detained and released at the required pre- developed rates. See Appendix A for WWHM12 calculation results. Maintenance Access: The paved access drive to the vault will provide the required maintenance access to the control structure. Detention Calculation Results: A summary of the detention calculations and vault design are shown on the following pages. The concrete vault will provide the required flow control for the site improvements. BMP SELECTION: Due to the site constraints, and soils type the only BMP that is feasible to use is having all downspouts tied into perforated stub outs prior to discharging into the storm drain system • Soil Amendment BMP’s: Will be used on site Renton Highlands 6-Lot SP TIR Revised November 14, 2024 23 | Page Figure 3: Sub-basins and Existing Site Conditions Renton Highlands 6-Lot SP TIR Revised November 14, 2024 24 | Page Figure 7: Developed Site Conditions Renton Highlands 6-Lot SP TIR Revised November 14, 2024 25 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 26 | Page WWHM12 SSD RESULTS SUB-BASIN #1: FLOW CONTROL SYSTEM Results From WWHM12 Calculations: Retention/Detention Facility  Type Of Facility: Detention Vault  Side Slopes: Vert Conc Walls  Pond Bottom Width: 59-ft (Actual: 52-ft)  Pond Bottom Length: 59-ft (Actual: 67-ft)  Pond Bottom Area: 3,481- sf (Actual: 3,484-sf)  Effective Live Storage Depth: 6.0 ft  Live Storage Volume Required: 20,886 cu.-ft  Live Storage Volume Provided: 20,904 cu.-ft (at Vault Size Designed)  Dead Storage Volume Req’d: 1,741 cu.-ft (at 0.5-ft depth)  Dead Storage Volume Provided: 1,742 cu.-ft (at 0.5 ft depth)  Water Quality System: Filterra The results of the WWHM12 calculations are included in Appendix A Renton Highlands 6-Lot SP TIR Revised November 14, 2024 27 | Page PUMP DESIGN: Per Table 1.2.3.A of Core Requirement #3, under Forested Conditions the discharge must match the peaks for the 50% of the 2-year and 10-year return periods. Per the WWHM12 results: • 50% of 2-Year Predeveloped Flow: = 0.020 cfs or 9 gpm • 10-Year Predeveloped Flow: = 0.050 cfs or 22.5 gpm The duplex pump system was designed to match the required flow rates per the table below; The Pump Table above, lists the allowable flow rates in GPM and the required pumps to be used. • Pump 1 Zoeller Model 264 (or equal) @ 9.0 gpm • Pump 2 Zoeller Model 266 (or equal) @ 22.5gpm • A backup emergency generator is required for the pump system See Appendix B for WWHM12 calculation results and pump tables SUB-BASIN #2 (Lots 5 & 6) The WWHM Ver.12 Hydraulic Simulation Model was used to calculate the pre-developed and developed flows for the Hydrographs for 100-yr, 24-hour duration design storm events for the existing and developed conditions. The hydrographs were generated using the following information: The trenches are designed to infiltrate 3,000 sf (1,500 sf per lot) of the roof areas The PIT infiltration test performed on the site showed a design rate of 1.22 inch per hour. Under the City of Renton design manual, only the infiltration BMP can be used as a flow credit. INFILTRATION DESIGN A PIT Infiltration test and Standard Subsurface Investigation Report by Hamid Koresan PE, dated August 22, 2024 prepared for the site showed the site soils to be a silty-sand (SM) - series to a depth of 5-ft with no signs of groundwater. The “PIT” Infiltration tests performed estimated Renton Highlands 6-Lot SP TIR Revised November 14, 2024 28 | Page the Measured Infiltration rate at approximately 3.43 -inches per hour with a Design Rate of 1.22 in/hr. (See Appendix A) The project will address the stormwater runoff as follows: • Each lot will infiltrate 1,500 sf of roof areas (3,000 sf total). This area can then be removed for the 100-flow calculations The WWHM12 program was the used to size the trench with the following results: Roof/Driveway Trench Sizing: • Total Roof Area: 3,000 sf : 0.068 acres (roof) • Trench Size for one lot: 1,500 sf or 0.034 • Design Infiltration rate: 1.22 inch per hr Results: • Trench Size: 50-ft x 5-ft x 2-ft deep (two required) Renton Highlands 6-Lot SP TIR Revised November 14, 2024 29 | Page Lots 5 and 6 Infiltration Results Renton Highlands 6-Lot SP TIR Revised November 14, 2024 30 | Page Sub-basin 2: 100-Year Flow calculations: The WWHM12 results show the difference between the site flow for the 100-year pre and post flows is under the 0.15 cfs making Subbasin 2 eligible for small site BMPS which will include: • Downspout Full Infiltration Systems in accordance with BMP T5.10A o For 1,500 sf of each roof (Allowed as a credit in the WWHM12 program) • Downspout Dispersion Splash blocks w/100 ft flow paths in accordance with BMP T5.10B o This BMP is not allowed in the WWHM12 modeling program • Pervious Pavement Driveways o This BMP is not allowed in the WWHM12 modeling program WWHM12 Input Information • Regional Gage Station: SeaTac • Precip Scale: 1.00 • Soils Type: Till Sub-Basin-2: Existing Site Hydrology The Sub-Basin is 0.53 acres in size The WWHM12 runoff was calculated using existing forested conditions to determine the pre-developed 100-year flow for the Existing Site. (See Figure 3: “Existing Site Conditions”). The site soils are identified as Till Type C,. Existing Area: Existing Pavement 0.074 acres (Impervious) Onsite Area 0.456 acres (Forested) Total Area: 0.530 Acres Sub-Basin: Developed Site Hydrology The runoff from the developed site conditions including roof areas, driveways, will be managed through the use of drainage BMP’s. (See Figure 6: “Developed Site Conditions”) The total area to be detained: 0.461 acres = 0.53 acres – 0.069 acres (To be infiltrated) Impervious Areas: Developed Sub-Basin  New Roofs: 6,000 sf – 3,000 sf (to be infiltrated) 0.069 acres  Driveways: 1,200 sf 0.027 acres  Ex Pavement NE 8th St 0.074 acres Total Impervious Area: 0.170 acres (Impervious) Pervious Area:  Lawn Area/Landscape: Pervious 0.291 acres Total Pervious Area: 0.291 acres (Lawn/Landscape) Total Site Area: 0.461 acres WWHM12 Flow Results o Developed 100-yr 0.2258 cfs – Pre-dev 0.0851 = 0.14070 cfs < 0.15 cfs, Therefore, sub-basin 2 is eligible for on-site BMPs to control the stormwater runoff. Renton Highlands 6-Lot SP TIR Revised November 14, 2024 31 | Page WATER QUALITY Sub-Basin 2: The total PGHS areas for Lots 5 and 6 is 1,200 sf. The added PGHS area for the widening of NE 8th has a net area new area of 1,200 sf for a total of 2,400 sf which is under the 5,000 sf threshold. Therefore, water quality is not required Landscaping: BMP T5.13 “Post Construction Soil Quality and Depth” The top soils will be stockpile on-site and reused per BMP T5.13 “Post Construction Soil Quality and Depth” which requires “Stockpile existing top soils during grading and replace it prior to planting…” In addition, the soils will be required to be tested for organic compliance. (See work sheets on following pages). SECTION 5: CONVEYANCE SYSTEM ANALYSIS AND DESIGN Sub-Basin 1: The piping and conveyance system for the interception of the drainage from the site was designed to convey the runoff from the 100-year, 24-hour storm event. (See Flow Charts Appendix A) The following conveyance capacity calculations for the on-site systems were calculated using the 100- year developed flow results from roadways, Parking and Driveway’s and the SBUH Method for the storm calculations. Design results: Storm Event Dev. On Site • 100-year, return period: 1.90 cfs: Dev flows for 12-inch pipe from the site improvements to the vault PIPE CAPACITY: ROADWAYS TO VAULT The 12- HDPE pipe from the Roads to vault was sized to handle the runoff from the 100-year storm. (See Appendix A “Pipe Conveyance Charts”) Using D.O.T. Chart 35 "Design Charts For Open Channel Flow": 12" HDPE Pipe Slope: 0.50 % Minimum Slope, Mannings: n = .012 100-Year Dev. Flows: 1.90 cfs Design Flow Capacity Results: 12" Pipe Capacity: = 2.70 cfs (flowing full) > 1.90 cfs required Velocity: = 3.95 fps > 3.00 fps required Therefore the 12" HDPE is adequate. 12-INCH POND STANDPIPE OVERFLOW: The 12- Stand pipe used as a the vertical over flow for the vault was sized to handle the runoff from the 100-year developed storm. (See Appendix A “Figure III-2.38 “Riser Inflows Curves”) Concrete Vault: Peak Stage above overflow: 0.5 feet from overflow to top of vault lid Capacity Required: 1.90 cfs Capacity Provided: 4.80 cfs Therefore, overflow ok. Renton Highlands 6-Lot SP TIR Revised November 14, 2024 32 | Page WATER QUALITY: Landscaping: BMP T5.13 “Post Construction Soil Quality and Depth” The top soils will be stockpile on-site and reused per BMP T5.13 “Post Construction Soil Quality and Depth” which requires “Stockpile existing top soils during grading and replace it prior to planting…” In addition, the soils will be required to be tested for organic compliance. (See work sheets on following pages). Roadway, Parking & Driveway Water Quality: Water quality will be provided by installing a “Filterra Peak Diversion” (FTPD) filter structure from Contech StormWater Management Inc. Contech Stormwater Management provided the sizing letter on the following page, based on the site plans. (Sizing will be provided upon preliminary approval by the City) Renton Highlands 6-Lot SP TIR Revised November 14, 2024 33 | Page SAMPLE Renton Highlands 6-Lot SP TIR Revised November 14, 2024 34 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 35 | Page TIR SECTION 6 SPECIAL REPORTS AND STUDIES • Structural Vault calculations, TIR SECTION 7 OTHER PERMITS Below is the list of anticipated permits required for this project. Other permits may be required that are not mentioned below. • Building Permit – New apartment building • Structural Vault Permit TIR SECTION 8 CSWPPP ANALYSIS AND DESIGN For the purposes of this report, several standard erosion control procedures will be utilized by the contractor to minimize the amount of erosion and sedimentation perpetuated by the construction of the site. Furthermore, these techniques are proposed for the Construction Stormwater Pollution Prevention Plan (CSWPPP) and should be reviewed and instituted by the onsite contractor. Some of the measures include filter fabric fence, and standard ground cover practices. A construction sequence will also be used to minimize the impacts of erosion due to construction. ESC Plan Analysis and Design (Part A) 1. At 1.51 acres and 0.52 acres in size, the sub-basins small requiring only minimal ESC measures. The 13-Elements of a Construction CSWPPP listed below, discuss and describe the appropriate ESC measure to be used. 2. Due to the small size of the site, no ESC facilities are proposed. Therefore, no analysis of the site’s ESC facilities was required. The proposed BMPs consist of standard items including: filter fences, construction entrance, CB inlet protection and plastic cover, etc. No sediment traps are proposed. If required, the vault can be used as a temporary sediment pond. 3. The area of the development with any high erosion are minimal and will be controlled by the filter fence around the perimeter of the site. 4. There were no special reports done for the site. 5. No exceptions or modifications are proposed of the “Erosion and Sedimentation Control Standards” Renton Highlands 6-Lot SP TIR Revised November 14, 2024 36 | Page THE 13 ELEMENTS OF A CONSTRUCTION CSWPPP 1. Preserve Vegetation/Mark Clearing Limits: The clearing limits are indicated on the plan sheet. Furthermore, clearing and grading will be limited to only areas that need to be disturbed for grading/construction of the road surface to preserve as much natural vegetation as possible. Field marking the clearing limits shall be completed prior to clearing and grubbing activities. BMP's: Preserve Natural Vegetation (VEG) Field Marking Clearing Limits (CL) 2. Establish Construction Access: Access to the construction site shall be limited to the rock construction entrance. The construction entrance shall be extended to provide access to the construction vehicle/equipment staging and employee parking areas. BMP's: Stabilized Construction Entrance (CE) 3. Control of Flow Rates: Storm water detention: No detention is proposed for the site since the increase in volume is minimal 4. Installation of Perimeter Sediment Controls: Sediment control will be provided through a combination of filtration through the surround on-site vegetation, filter fence, straw bails, BMP's: Silt Fence (FF) 5. Soils Stabilization: Temporary and permanent soil stabilization will be provided. Temporary stabilization will be provided through the application of straw and/or plastic sheeting to exposed, worked earth. From October 1 until April 30, no exposed soil may remain exposed and unworked for more than two days; after May 1, no exposed soil may remain exposed and unworked for more than seven days. BMP's: Plastic Sheeting, 6. Slope Protection: Slopes shall be protected from erosion through cover and prevention of concentrated surface runoff flows. BMP's: Plastic Sheeting, 7. Protection of Permanent Drain Inlets and Dust/Mud Control: Inlet protection will be provided for all catch basins. BMP’s: Inlet Protection BMP’s: Street Sweeping and watering of dust areas 8. Stabilization of Channels and Outlets: All channel slopes shall be constructed and protected against erosion in accordance with City of Renton BMP's: None required 9. Pollutant Control: Pollutants shall be controlled as described in the Potential Pollutants section of this SWPPP. 10. Dewatering Control: De-watering: Interception of the water table is not expected to occur, even if there is an increase in precipitation. However, should ground water flows be encountered, the flows can be directed to on site native vegetation for cleanup. BMP's: Native vegetation (As Required) 11. BMP Maintenance: All BMP's and SWPPP elements shall be inspected daily and maintained as required. 12. Project Management: The project shall be managed in a cooperative effort by the project manager, contractor, engineer, and the county inspector. During the construction process, if unforeseen issues arise that cannot be resolved on site, construction activity (other than SWPPP maintenance) shall be halted and the county inspector and the project engineer are to be contacted and informed of the situation. The Erosion Control Lead TBD Renton Highlands 6-Lot SP TIR Revised November 14, 2024 37 | Page 13. Protect On-Site Stormwater Management BMPs For Runoff From Roofs And Other Hard Surface On-site stormwater management BMPs used for runoff from roofs and other hard surfaces include: full dispersion, roof downspout full infiltration or dispersion systems, perforated stubout connections, rain gardens, bioretention systems, permeable pavement, sheetflow dispersion, and concentrated flow dispersion. The areas on the site to be used for these BMPs shall be protected from siltation and compaction during construction by sequencing the construction in a fashion to install these BMPs at the latter part of the construction grading operations, by excluding equipment from the BMPS and the associated areas, and by using the erosion and sedimentation control BMPs. BMP C102: Buffer Zone Since the project is for residential apartments, under the City of Renton 30.63 A.530, (2) the project does not fall under the “High Use Sites” covering commercial or industrial sites. BMP C-151: Concrete Handling (Design and Installation Specifications) Concrete truck chutes, pumps, and internals shall be washed out only into formed areas awaiting installation of concrete or asphalt. Unused concrete remaining in the truck and pump shall be returned to the originating batch plant for recycling. Hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels shall be washed off only into formed areas awaiting installation of concrete or asphalt. Equipment that cannot be easily moved, such as concrete pavers, shall only be washed in areas that do not directly drain to natural or constructed stormwater conveyances. Washdown from areas such as concrete aggregate driveways shall not drain directly to natural or constructed stormwater conveyances. When no formed areas are available, washwater and leftover product shall be contained in a lined container. Contained concrete shall be disposed of in a manner that does not violate groundwater or surface water quality standards Maintenance Standards: Containers shall be checked for holes in the liner daily during concrete pours and repaired the same day Soil Management Plan for “Post Construction Soil Standard” The top soils will be stockpile on-site and reused per “Implementation Options #4b “Amend existing soil in place per the Post Construction Soil Standard” which requires “Stockpile existing top soils during grading and replace it prior to planting…” In addition, the soils will be required to be tested for organic compliance. See the following requirements. Amend Existing Soils, Purpose and Definition Naturally occurring (undisturbed) soil and vegetation provide important stormwater functions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment and pollutant biofiltration; water interflow storage and transmission; and pollutant decomposition. These functions are largely lost when development strips away native soil and vegetation and replaces it with minimal topsoil and sod. Not only are these important stormwater functions lost, but such landscapes themselves become pollution- generating pervious surfaces due to increased use of pesticides, fertilizers and other landscaping and household/industrial chemicals, the Renton Highlands 6-Lot SP TIR Revised November 14, 2024 38 | Page concentration of pet wastes, and pollutants that accompany roadside litter. Establishing soil quality and depth regains greater stormwater functions in the post development landscape, provides increased treatment of pollutants and sediments that result from development and habitation, and minimizes the need for some landscaping chemicals, thus reducing pollution through prevention. Applications and Limitations Establishing a minimum soil quality and depth is not the same as preservation of naturally occurring soil and vegetation. However, establishing a minimum soil quality and depth will provide improved on-site management of stormwater flow and water quality. Soil organic matter can be attained through numerous materials such as compost, composted woody material, biosolids, and forest product residuals. It is important that the materials used to meet the soil quality and depth BMP be appropriate and beneficial to the plant cover to be established. Likewise, it is important that imported topsoils improve soil conditions and do not have an excessive percent of clay fines. Design Guidelines Soil retention. The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In any areas requiring grading remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. Soil quality. All areas subject to clearing and grading that have not been covered by impervious surface, incorporated into a drainage facility or engineered as structural fill or slope shall, at project completion, demonstrate the following: I. A topsoil layer with a minimum organic matter content of ten percent dry weight in planting beds, and 5% organic matter content (based on a loss-on-ignition test) in turf areas, and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least 4 inches with some incorporation of the upper material to avoid stratified layers, where feasible. 2. Planting beds must be mulched with 2 inches of organic material 3. Quality of compost and other materials used to meet the organic content requirements: a. The organic content for -pre-approved” amendment rates can be met only using compost that meets the definition of -composted materials” in WAC I73-350-220. This code is available online at: http://www.ecy.wa.gov/programs/swfa/facilities/350.html. Compost used in bioretention areas should be stable, mature and derived from yard debris, wood waste, or other organic materials that meet the intent of the organic soil amendment specification. Biosolids and manure composts can be higher in bio-available phosphorus than compost derived from yard or plant waste and therefore are not allowed in bioretention areas due to the possibility of exporting bio-available phosphorus in effluent. The compost must also have an organic matter content of 35% to 65%, and a carbon to nitrogen ratio below 25:I. The carbon to nitrogen ratio may be as high as 35:I for plantings composed entirely of plants native to the Puget Sound Lowlands region. b. Calculated amendment rates may be met through use of composted materials as defined above; or other organic materials amended to meet the carbon to nitrogen ratio requirements, and meeting the contaminant standards of Grade A Compost. The resulting soil should be conducive to the type of vegetation to be established. Renton Highlands 6-Lot SP TIR Revised November 14, 2024 39 | Page Implementation Options: The soil quality design guidelines listed above can be met by using one of the methods listed below. I. Leave undisturbed native vegetation and soil, and protect from compaction during construction. 2. Amend disturbed soil according to the following procedures: b. Scarify subsoil to a depth of one foot c. In planting beds, place three inches of compost and till in to an eight-inch depth. d. In turf areas, place two inches of compost and till in to an eight-inch depth. e. Apply two to four inches of arborist wood chip, coarse bark mulch, or compost mulch to planting beds after final planting. Alternatively, disturbed soil can be amended on a site-customized manner so that it meets the soil quality criteria set forth above, as determined by a licensed engineer, geologist, landscape architect, or other person as approved by City of Renton. 3. Stockpile existing topsoil during grading, and replace it prior to planting. Stockpiled topsoil must be amended if needed to meet the organic matter and depth requirements by following the procedures in method (2) above). 4. Import topsoil mix of sufficient organic content and depth to meet the organic matter and depth requirements. 5. More than one method may be used on different portions of the same site. Soil that already meets the depth and organic matter quality standards, and is not compacted, does not need to be amended. Maintenance Soil quality and depth should be established toward the end of construction and once established, should be protected from compaction, such as from large machinery use, and from erosion. Soil should be planted and mulched after installation. Plant debris or its equivalent should be left on the soil surface to replenish organic matter. TIR SECTION 9 BONDS, SUMMARIES AND COVENANTS All the necessary documents listed below will be included after first review comments are received. These will include: • Bond Quantities, • Flow Control and Water Quality Facility Summary Sheet and Sketch • Declaration of Covenant for Privately Maintained Flow Control and WQ Facilities • Declaration of Covenant for Privately Maintained Flow Control BMPs Renton Highlands 6-Lot SP TIR Revised November 14, 2024 40 | Page TIR SECTION 10 OPERATIONS AND MAINTENANCE MANUAL Stormwater System Description The stormwater system for the site is fairly basic and contains the following elements: • 12”-inch storm pipe • Catch basin • Detention Vault • Filterra • Pump System • Infiltration Renton Highlands 6-Lot SP TIR Revised November 14, 2024 41 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 42 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 43 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 44 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 45 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 46 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 47 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 48 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 49 | Page Renton Highlands 6-Lot SP TIR Revised November 14, 2024 50 | Page APPENDIX A PIPE CAPACITY PUMP CURVES LOT 5&6 INFILTRATION WWHM12 RESULTS BASIN-2 100-YR FLOW WWHM12 RESULTS DETENTION VAULT WWHM12 RESULTS PIT INFTRATION RESULTS WWHM2012 PROJECT REPORT default[60]10/25/2024 9:33:12 AM Page 2 General Model Information WWHM2012 Project Name:default[60] Site Name: Site Address: City: Report Date:10/25/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2023/01/27 Version:4.2.19 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year default[60]10/25/2024 9:33:12 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.034 Pervious Total 0.034 Impervious Land Use acre Impervious Total 0 Basin Total 0.034 default[60]10/25/2024 9:33:12 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.034 Impervious Total 0.034 Basin Total 0.034 default[60]10/25/2024 9:33:12 AM Page 6 Mitigated Routing Gravel Trench Bed 1 Bottom Length:50.00 ft. Bottom Width:5.00 ft. Trench bottom slope 1:0.01 To 1 Trench Left side slope 0:0.01 To 1 Trench right side slope 2:0.01 To 1 Material thickness of first layer:2 Pour Space of material for first layer:0.33 Material thickness of second layer:0 Pour Space of material for second layer:0 Material thickness of third layer:0 Pour Space of material for third layer:0 Infiltration On Infiltration rate:1.22 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):5.262 Total Volume Through Riser (ac-ft.):0.001 Total Volume Through Facility (ac-ft.):5.262 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:1.9 ft. Riser Diameter:6 in. Element Flows To: Outlet 1 Outlet 2 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.005 0.000 0.000 0.000 0.0222 0.005 0.000 0.000 0.007 0.0444 0.005 0.000 0.000 0.007 0.0667 0.005 0.000 0.000 0.007 0.0889 0.005 0.000 0.000 0.007 0.1111 0.005 0.000 0.000 0.007 0.1333 0.005 0.000 0.000 0.007 0.1556 0.005 0.000 0.000 0.007 0.1778 0.005 0.000 0.000 0.007 0.2000 0.005 0.000 0.000 0.007 0.2222 0.005 0.000 0.000 0.007 0.2444 0.005 0.000 0.000 0.007 0.2667 0.005 0.000 0.000 0.007 0.2889 0.005 0.000 0.000 0.007 0.3111 0.005 0.000 0.000 0.007 0.3333 0.005 0.000 0.000 0.007 0.3556 0.005 0.000 0.000 0.007 0.3778 0.005 0.000 0.000 0.007 0.4000 0.005 0.000 0.000 0.007 0.4222 0.005 0.000 0.000 0.007 0.4444 0.005 0.000 0.000 0.007 0.4667 0.005 0.000 0.000 0.007 0.4889 0.005 0.000 0.000 0.007 default[60]10/25/2024 9:33:12 AM Page 9 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.034 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.034 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.001 5 year 0.00157 10 year 0.001893 25 year 0.002236 50 year 0.002447 100 year 0.002628 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.001 0.000 1950 0.001 0.000 1951 0.002 0.000 1952 0.001 0.000 1953 0.001 0.000 1954 0.001 0.000 1955 0.001 0.000 1956 0.001 0.000 1957 0.001 0.000 1958 0.001 0.000 default[60]10/25/2024 9:33:51 AM Page 32 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2024; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com WWHM2012 PROJECT REPORT default[60]10/25/2024 8:08:07 AM Page 2 General Model Information WWHM2012 Project Name:default[60] Site Name: Site Address: City: Report Date:10/25/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2023/01/27 Version:4.2.19 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year default[60]10/25/2024 8:08:07 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.456 Pervious Total 0.456 Impervious Land Use acre ROADS FLAT 0.074 Impervious Total 0.074 Basin Total 0.53 default[60]10/25/2024 8:08:07 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.291 Pervious Total 0.291 Impervious Land Use acre ROADS FLAT 0.074 ROOF TOPS FLAT 0.069 DRIVEWAYS FLAT 0.027 Impervious Total 0.17 Basin Total 0.461 default[60]10/25/2024 8:08:07 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.456 Total Impervious Area:0.074 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.291 Total Impervious Area:0.17 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.035654 5 year 0.047469 10 year 0.055828 25 year 0.067021 50 year 0.075831 100 year 0.085054 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.084923 5 year 0.117182 10 year 0.140638 25 year 0.172735 50 year 0.19848 100 year 0.225836 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.050 0.126 1950 0.046 0.123 1951 0.044 0.078 1952 0.026 0.051 1953 0.023 0.054 1954 0.030 0.068 1955 0.035 0.073 1956 0.034 0.073 1957 0.040 0.095 1958 0.027 0.064 default[60]10/25/2024 8:09:03 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2024; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com WWHM2012 PROJECT REPORT default[10]11/13/2024 6:22:01 AM Page 2 General Model Information Project Name:default[10] Site Name: Site Address: City: Report Date:11/13/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year default[10]11/13/2024 6:22:01 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 1.51 Pervious Total 1.51 Impervious Land Use acre Impervious Total 0 Basin Total 1.51 Element Flows To: Surface Interflow Groundwater default[10]11/13/2024 6:22:01 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.799 Pervious Total 0.799 Impervious Land Use acre ROADS FLAT 0.296 ROOF TOPS FLAT 0.31 DRIVEWAYS FLAT 0.055 SIDEWALKS FLAT 0.05 Impervious Total 0.711 Basin Total 1.51 Element Flows To: Surface Interflow Groundwater SSD Table 1 SSD Table 1 default[10]11/13/2024 6:22:01 AM Page 6 Mitigated Routing SSD Table 1 Depth:6 ft. Element Flows To: Outlet 1 Outlet 2 SSD Table Hydraulic Table Stage Area Volume (feet) (ac.) (ac-ft.) Manual NotUsed NotUsed NotUsed NotUsed 0.080 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.200 0.080 0.016 0.020 0.000 0.000 0.000 0.000 0.400 0.080 0.037 0.020 0.000 0.000 0.000 0.000 0.600 0.080 0.052 0.020 0.000 0.000 0.000 0.000 0.800 0.080 0.069 0.020 0.000 0.000 0.000 0.000 1.000 0.080 0.091 0.020 0.000 0.000 0.000 0.000 1.200 0.080 0.106 0.020 0.000 0.000 0.000 0.000 1.400 0.080 0.112 0.020 0.000 0.000 0.000 0.000 1.600 0.080 0.128 0.020 0.000 0.000 0.000 0.000 1.800 0.080 0.144 0.020 0.000 0.000 0.000 0.000 2.000 0.080 0.160 0.020 0.000 0.000 0.000 0.000 2.200 0.080 0.176 0.020 0.000 0.000 0.000 0.000 2.400 0.080 0.192 0.020 0.000 0.000 0.000 0.000 2.600 0.080 0.208 0.020 0.000 0.000 0.000 0.000 2.800 0.080 0.224 0.020 0.000 0.000 0.000 0.000 3.000 0.080 0.240 0.020 0.000 0.000 0.000 0.000 3.200 0.080 0.256 0.020 0.000 0.000 0.000 0.000 3.400 0.080 0.272 0.020 0.000 0.000 0.000 0.000 3.600 0.080 0.288 0.020 0.000 0.000 0.000 0.000 3.800 0.080 0.304 0.020 0.000 0.000 0.000 0.000 4.000 0.080 0.320 0.020 0.000 0.000 0.000 0.000 4.200 0.080 0.336 0.050 0.000 0.000 0.000 0.000 4.400 0.080 0.352 0.050 0.000 0.000 0.000 0.000 4.600 0.080 0.368 0.050 0.000 0.000 0.000 0.000 4.800 0.080 0.384 0.050 0.000 0.000 0.000 0.000 5.000 0.080 0.400 0.050 0.000 0.000 0.000 0.000 5.200 0.080 0.416 0.050 0.000 0.000 0.000 0.000 5.400 0.080 0.432 0.050 0.000 0.000 0.000 0.000 5.600 0.080 0.448 0.050 0.000 0.000 0.000 0.000 5.800 0.080 0.464 0.050 0.000 0.000 0.000 0.000 6.000 0.080 0.480 0.050 0.000 0.000 0.000 0.000 default[10]11/13/2024 6:22:01 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.51 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.799 Total Impervious Area:0.711 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.044395 5 year 0.069724 10 year 0.084079 25 year 0.099286 50 year 0.108697 100 year 0.116701 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.022484 5 year 0.030506 10 year 0.03675 25 year 0.045782 50 year 0.053398 100 year 0.061827 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.044 0.020 1950 0.054 0.020 1951 0.098 0.050 1952 0.031 0.020 1953 0.025 0.020 1954 0.038 0.020 1955 0.061 0.020 1956 0.049 0.020 1957 0.039 0.020 1958 0.044 0.020 default[10]11/13/2024 6:22:27 AM Page 8 1959 0.038 0.020 1960 0.066 0.041 1961 0.037 0.020 1962 0.023 0.020 1963 0.032 0.020 1964 0.042 0.020 1965 0.030 0.020 1966 0.029 0.020 1967 0.060 0.020 1968 0.038 0.020 1969 0.037 0.020 1970 0.030 0.020 1971 0.032 0.020 1972 0.073 0.050 1973 0.033 0.020 1974 0.036 0.020 1975 0.049 0.020 1976 0.035 0.020 1977 0.004 0.020 1978 0.031 0.020 1979 0.019 0.020 1980 0.069 0.050 1981 0.028 0.020 1982 0.053 0.020 1983 0.048 0.020 1984 0.029 0.020 1985 0.017 0.020 1986 0.077 0.020 1987 0.068 0.020 1988 0.027 0.020 1989 0.018 0.020 1990 0.142 0.034 1991 0.086 0.038 1992 0.033 0.020 1993 0.034 0.020 1994 0.012 0.020 1995 0.049 0.020 1996 0.104 0.050 1997 0.087 0.050 1998 0.020 0.020 1999 0.082 0.037 2000 0.034 0.020 2001 0.006 0.020 2002 0.038 0.020 2003 0.048 0.020 2004 0.062 0.050 2005 0.045 0.020 2006 0.053 0.020 2007 0.106 0.050 2008 0.136 0.050 2009 0.067 0.020 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1423 0.0500 2 0.1363 0.0500 3 0.1056 0.0500 default[10]11/13/2024 6:22:27 AM Page 9 4 0.1040 0.0500 5 0.0978 0.0500 6 0.0870 0.0500 7 0.0857 0.0500 8 0.0815 0.0500 9 0.0769 0.0410 10 0.0728 0.0380 11 0.0690 0.0368 12 0.0681 0.0341 13 0.0669 0.0200 14 0.0661 0.0200 15 0.0621 0.0200 16 0.0610 0.0200 17 0.0604 0.0200 18 0.0544 0.0200 19 0.0530 0.0200 20 0.0526 0.0200 21 0.0494 0.0200 22 0.0486 0.0200 23 0.0485 0.0200 24 0.0480 0.0200 25 0.0475 0.0200 26 0.0446 0.0200 27 0.0441 0.0200 28 0.0436 0.0200 29 0.0419 0.0200 30 0.0392 0.0200 31 0.0383 0.0200 32 0.0379 0.0200 33 0.0377 0.0200 34 0.0376 0.0200 35 0.0373 0.0200 36 0.0368 0.0200 37 0.0359 0.0200 38 0.0352 0.0200 39 0.0344 0.0200 40 0.0343 0.0200 41 0.0331 0.0200 42 0.0330 0.0200 43 0.0325 0.0200 44 0.0319 0.0200 45 0.0308 0.0200 46 0.0308 0.0200 47 0.0304 0.0200 48 0.0300 0.0200 49 0.0294 0.0200 50 0.0289 0.0200 51 0.0276 0.0200 52 0.0269 0.0200 53 0.0249 0.0200 54 0.0232 0.0200 55 0.0197 0.0200 56 0.0186 0.0200 57 0.0175 0.0200 58 0.0174 0.0200 59 0.0116 0.0200 60 0.0062 0.0200 61 0.0042 0.0200 default[10]11/13/2024 6:22:27 AM Page 11 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0222 17567 3052 17 Pass 0.0231 16164 2992 18 Pass 0.0239 14970 2935 19 Pass 0.0248 13858 2881 20 Pass 0.0257 12814 2810 21 Pass 0.0266 11813 2721 23 Pass 0.0274 10904 2659 24 Pass 0.0283 10121 2601 25 Pass 0.0292 9388 2532 26 Pass 0.0301 8729 2468 28 Pass 0.0309 8147 2415 29 Pass 0.0318 7599 2357 31 Pass 0.0327 7060 2297 32 Pass 0.0336 6590 2239 33 Pass 0.0344 6149 2173 35 Pass 0.0353 5777 2121 36 Pass 0.0362 5433 2072 38 Pass 0.0371 5097 2029 39 Pass 0.0379 4808 1989 41 Pass 0.0388 4526 1952 43 Pass 0.0397 4252 1915 45 Pass 0.0405 4017 1886 46 Pass 0.0414 3784 1868 49 Pass 0.0423 3546 1852 52 Pass 0.0432 3339 1832 54 Pass 0.0440 3138 1810 57 Pass 0.0449 2952 1789 60 Pass 0.0458 2787 1773 63 Pass 0.0467 2597 1746 67 Pass 0.0475 2447 1729 70 Pass 0.0484 2306 1711 74 Pass 0.0493 2160 1686 78 Pass 0.0502 2026 0 0 Pass 0.0510 1898 0 0 Pass 0.0519 1790 0 0 Pass 0.0528 1688 0 0 Pass 0.0537 1584 0 0 Pass 0.0545 1483 0 0 Pass 0.0554 1381 0 0 Pass 0.0563 1292 0 0 Pass 0.0571 1219 0 0 Pass 0.0580 1154 0 0 Pass 0.0589 1098 0 0 Pass 0.0598 1048 0 0 Pass 0.0606 997 0 0 Pass 0.0615 930 0 0 Pass 0.0624 883 0 0 Pass 0.0633 837 0 0 Pass 0.0641 789 0 0 Pass 0.0650 743 0 0 Pass 0.0659 713 0 0 Pass 0.0668 668 0 0 Pass 0.0676 630 0 0 Pass default[10]11/13/2024 6:22:27 AM Page 12 0.0685 595 0 0 Pass 0.0694 565 0 0 Pass 0.0703 539 0 0 Pass 0.0711 496 0 0 Pass 0.0720 473 0 0 Pass 0.0729 434 0 0 Pass 0.0737 399 0 0 Pass 0.0746 366 0 0 Pass 0.0755 348 0 0 Pass 0.0764 323 0 0 Pass 0.0772 296 0 0 Pass 0.0781 272 0 0 Pass 0.0790 256 0 0 Pass 0.0799 235 0 0 Pass 0.0807 217 0 0 Pass 0.0816 195 0 0 Pass 0.0825 180 0 0 Pass 0.0834 158 0 0 Pass 0.0842 145 0 0 Pass 0.0851 129 0 0 Pass 0.0860 119 0 0 Pass 0.0869 109 0 0 Pass 0.0877 97 0 0 Pass 0.0886 91 0 0 Pass 0.0895 82 0 0 Pass 0.0903 76 0 0 Pass 0.0912 68 0 0 Pass 0.0921 61 0 0 Pass 0.0930 54 0 0 Pass 0.0938 48 0 0 Pass 0.0947 41 0 0 Pass 0.0956 38 0 0 Pass 0.0965 33 0 0 Pass 0.0973 27 0 0 Pass 0.0982 22 0 0 Pass 0.0991 21 0 0 Pass 0.1000 20 0 0 Pass 0.1008 19 0 0 Pass 0.1017 17 0 0 Pass 0.1026 14 0 0 Pass 0.1035 12 0 0 Pass 0.1043 9 0 0 Pass 0.1052 4 0 0 Pass 0.1061 3 0 0 Pass 0.1069 3 0 0 Pass 0.1078 3 0 0 Pass 0.1087 3 0 0 Pass default[10]11/13/2024 6:22:27 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. default[10]11/13/2024 6:22:27 AM Page 14 LID Report default[10]11/13/2024 6:22:34 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. default[10]11/13/2024 6:22:34 AM Page 16 Appendix Predeveloped Schematic default[10]11/13/2024 6:22:35 AM Page 17 Mitigated Schematic default[10]11/13/2024 6:22:35 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 default[10].wdm MESSU 25 Predefault[10].MES 27 Predefault[10].L61 28 Predefault[10].L62 30 POCdefault[10]1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 10 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 10 C, Forest, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 10 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 10 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO default[10]11/13/2024 6:22:35 AM Page 19 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 10 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 10 0 4.5 0.08 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 10 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 10 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 10 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 default[10]11/13/2024 6:22:35 AM Page 20 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 10 1.51 COPY 501 12 PERLND 10 1.51 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC default[10]11/13/2024 6:22:35 AM Page 21 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN default[10]11/13/2024 6:22:35 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 default[10].wdm MESSU 25 Mitdefault[10].MES 27 Mitdefault[10].L61 28 Mitdefault[10].L62 30 POCdefault[10]1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 16 IMPLND 1 IMPLND 4 IMPLND 5 IMPLND 8 RCHRES 1 COPY 1 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 SSD Table 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY default[10]11/13/2024 6:22:35 AM Page 23 PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 4 ROOF TOPS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 4 0 0 1 0 0 0 5 0 0 1 0 0 0 8 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 0 1 9 4 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** default[10]11/13/2024 6:22:35 AM Page 24 # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 4 0 0 0 0 0 5 0 0 0 0 0 8 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 4 400 0.01 0.1 0.1 5 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 4 0 0 5 0 0 8 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 4 0 0 5 0 0 8 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 16 0.799 RCHRES 1 2 PERLND 16 0.799 RCHRES 1 3 IMPLND 1 0.296 RCHRES 1 5 IMPLND 4 0.31 RCHRES 1 5 IMPLND 5 0.055 RCHRES 1 5 IMPLND 8 0.05 RCHRES 1 5 ******Routing****** PERLND 16 0.799 COPY 1 12 IMPLND 1 0.296 COPY 1 15 IMPLND 4 0.31 COPY 1 15 IMPLND 5 0.055 COPY 1 15 IMPLND 8 0.05 COPY 1 15 PERLND 16 0.799 COPY 1 13 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO default[10]11/13/2024 6:22:35 AM Page 25 RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 SSD Table 1 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 31 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.080000 0.000000 0.000000 0.000000 0.200000 0.080000 0.016000 0.020000 0.400000 0.080000 0.037000 0.020000 0.600000 0.080000 0.052000 0.020000 0.800000 0.080000 0.069000 0.020000 1.000000 0.080000 0.091000 0.020000 1.200000 0.080000 0.106000 0.020000 1.400000 0.080000 0.112000 0.020000 1.600000 0.080000 0.128000 0.020000 1.800000 0.080000 0.144000 0.020000 2.000000 0.080000 0.160000 0.020000 2.200000 0.080000 0.176000 0.020000 2.400000 0.080000 0.192000 0.020000 2.600000 0.080000 0.208000 0.020000 2.800000 0.080000 0.224000 0.020000 3.000000 0.080000 0.240000 0.020000 3.200000 0.080000 0.256000 0.020000 3.400000 0.080000 0.272000 0.020000 3.600000 0.080000 0.288000 0.020000 3.800000 0.080000 0.304000 0.020000 4.000000 0.080000 0.320000 0.020000 4.200000 0.080000 0.336000 0.050000 default[10]11/13/2024 6:22:35 AM Page 26 4.400000 0.080000 0.352000 0.050000 4.600000 0.080000 0.368000 0.050000 4.800000 0.080000 0.384000 0.050000 5.000000 0.080000 0.400000 0.050000 5.200000 0.080000 0.416000 0.050000 5.400000 0.080000 0.432000 0.050000 5.600000 0.080000 0.448000 0.050000 5.800000 0.080000 0.464000 0.050000 6.000000 0.080000 0.480000 0.050000 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1001 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN default[10]11/13/2024 6:22:35 AM Page 29 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. 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Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Lots 5 and 6 Renton Infiltration Report Page 1 PIT INFILTRATION TEST AND STANDARD SUBSURFACE INVESTIGATION REPORT October 20, 2024 INTRODUCTION The proposed project is the construction of a six lot short plat. The site is located at 5815 NE 8th Street . The drainage from Sub-basin 2 (Lots 5 & 6) is proposing to use partial infiltration of 3,000 sf of roof area. This report is being prepared using Section 5 of the 2022 Renton Stormwater Management Manual. SUBSURFACE CONDITIONS The soils were visually classified in general as Ground Moraine Deposit (Qgt) as well as a Alterwood Sandy Loam (AgC) with slopes less than 3-percent, presented in Figure 1. The logs of the test pits are attached to this report and are presented as Figure 2. HYDROGEOLOGIC CONDITIONS The soils were moist with no indication of high groundwater including seepage when the test pit was excavated down to 5.0 feet after the PIT infiltration test was performed. INFILTRATION TESTING: A small-scale Pilot Infiltration Test (PIT) was performed to evaluate the infiltration rate of the soil. The infiltration test was conducted at a depth of 2.5-feet below the ground surface, which is close to the anticipated bottom of the infiltration facility. Setup: The test pit dug was rectangular in shape, and measured roughly 4.0’x 4.5’x 3.0’ (width x length x depth). A vertical measuring rod was installed in the pit for the purpose of measuring the depth of ponded water Based on the geometry of the test pit dug for SL-1, the total plan area of the bottom of the test pit is calculated as follows: Test Pit Bottom Area = (4.01)(4.51) Test Pit Bottom Area = 18.0 ft2 Soaking Period: In preparation for the soaking period, the test pit was filled with water to a depth of over 12-inches. A plastic tray was utilized as a splash block to help prevent water flowing into the test pit from disturbing soils at the bottom of the pit, and the hose administering water to the pit was held in place over the splash block using a clamp. The water level in the pit was maintained at a depth of a minimum of 12-inches for over 6-hours, as required by the test procedure. Measurement of Infiltration Rate: Upon completion of the soaking period, the water was allowed to drain until achieving a water depth of between 8 and 16 inches, and the flow rate of the water into the test pit was adjusted to a rate that was expected to maintain the water level at the same point between 8 to 16 inches in depth over the course of an hour. The instantaneous flow-rate and water depth were then measured and recorded every 15-minutes (approximately) over the course an hour. A summary of this recorded data is provided in the table below Lots 5 and 6 Renton Infiltration Report Page 2 Table 1: Measured Infiltration Data During Flow Period 15-min Interval Time of Measurement Instantaneous Flow Rate Water Depth - hour:minute gal/min inches 1 1:00 0.000 12 2 1:30 0.218 10.1 Stabilized Flow Period: 3 1:45 0.436 9.25 4 2:00 0.436 8.38 5 2:15 0.436 7.50 6 2:30 0.436 6.64 Average Stabilized Flow Rate = 0.436 The flow-rate was adjusted after the first two 15-minute intervals, so that a stabilized flow rate was achieved that would maintain a depth of water at the same point over a one-hour time period. Accordingly, readings shown in table 1 above represent data collected during this 1-hour period of stabilized flow. Measured Stabilized Flow Rate Calculation: From the data presented in table 1, the measured stabilized flow infiltration rate was computed by dividing the average flow-rate by the horizontal bottom area of the test pit and converting to inches per hour Drawdown Time: Upon completion of the 1-hour stabilized flow period, the water flowing into the test pit was shut off to allow the water-level in the test pit to drop. During this “drawdown” time, measurements of the water-level were taken periodically for three-hours. The data measurements are provided in table 2 below: Table 2: Measured Infiltration Data for Drawdown Time Time Δ Time Depth Δ Depth Infiltration Rate hour:minute minutes inches inches inches/hour 1:00 - 16 - - 1:30 30 14.23 1.77 3.54 2:00 30 12.48 1.75 3.50 1:30 30 10.73 1.75 3.50 3:00 30 8.98 1.74 3.48 3:30 30 7.24 1.76 3.52 4:00 30 5.49 1.75 3.50 Average Infiltration Rate = 3.48 Measured Infiltration Rate: Based the measured infiltration data above it was determined that the average infiltration rate is 3.48 inches per hour ( I measured ) which will be used for the base rate and then apply the correction factors per Section 5.2 of the KCSWM Manual. Lots 5 and 6 Renton Infiltration Report Page 3 I measured = 3.48 incℎes⁄ℎour F testing = 0.50 For PIT test F Geometry = 4 D/W + 0.05 = 4 (2/4) + 0.05 = 2.05 = 1.0 (Must be between 0.25 & 1) F plugging = 0.7 I Design = 3.43 x 0.50 x 1.0 x 0.7 = 1.22 inches/hour Therefore, the design and sizing of the infiltration rate will be based on a rate of I Design = 1.22 in/hr and the WWHM3 design program. 10/20/24 Lots 5 and 6 Renton Infiltration Report Page 4 FIGURE 1 Lots 5 and 6 Renton Infiltration Report Page 5 FIGURE 2 Lots 5 and 6 Renton Infiltration Report Page 6 UNIFIED SOIL CLASSIFICATION