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Home My WebLink AboutRS_TIR_240513_v4FES Project 20069 TOC Stormwater Site Plan/Report Grant Place Townhomes 1600 Grant Avenue S Renton, WA 98055 Jurisdiction: City of Renton Permit #: PR23-000126, LUA23-000283, C23006099 Parcel #202305-9052 For: Siki Chang Skyline Properties, Inc 50 116th AVE SE, Ste 120 Bellevue, WA, 98004 Prepared: April 3, 2023 Revised: 5/13/2024 Prepared by: R. Elliott, E.I.T. FES Project #20069 R G G N A FU R SEF O R P I ANO EL T S GE SI N ERE DEEATDSNTAWFO . SAHI INREENOT R46937 5/13/2024 SURFACE WATER UTILITY JFarah 09/03/2024 DEVELOPMENT ENGINEERING NJanders 09/16/2024 FES Project 20069 Page 2 TABLE OF CONTENTS 1.0 PROJECT OVERVIEW ................................................................................................ 3 Technical Information Report (TIR) Worksheet ........................................................... 4 Vicinity Map ................................................................................................................ 9 2.0 CONDITIONS AND REQUIREMENTS SUMMARY ................................................... 10 2.1 Analysis of the Nine (9) Core Requirements ....................................................... 11 2.2 Analysis of the Special Requirements ................................................................. 13 2.3 Conditions of Approval ........................................................................................ 13 3.0 OFFSITE ANALYSIS ................................................................................................. 14 3.1 Task 1: Define and Map the Study Area. ............................................................. 14 3.2 Task 2: Review All Available Information on the Study Area ............................... 14 3.3 Task 3: Field Inspect the Study Area ................................................................... 15 3.4 Task 4: Describe the Drainage System ............................................................... 15 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ...................................................................... 18 4.1 VAULT ANALYSIS .............................................................................................. 20 Existing Conditions ................................................................................................... 22 4.2 WATER QUALITY SYSTEM ............................................................................... 23 Proposed Conditions ................................................................................................. 24 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN................................................. 25 5.1 Uniform Flow Analysis Method ............................................................................ 25 5.2 Backflow Analysis Method .................................................................................. 26 5.3 Grate Inlet Capacity Analysis .............................................................................. 29 7.0 OTHER PERMITS ...................................................................................................... 35 8.0 CSWPP ANALYSIS AND DESIGN ............................................................................ 36 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ................................................................................................................................ 37 10.0 OPERATIONS AND MAINTENANCE MANUAL ........................................................ 38 Appendix A: Pacific Engineering Downstream Analysis ............................................... 53 Appendix B: Geotechnical Report ................................................................................... 54 Appendix C: As-Built Survey Drawings ........................................................................... 55 Appendix D: Flow Control and Water Quality Calculations ........................................... 56 Appendix E: StormFilter Details....................................................................................... 57 FES Project no. 20069 Page 3 1.0 PROJECT OVERVIEW This project proposes the construction of eight townhouse buildings on a single 92,828 sf (2.131 ac) parcel (no. 202305-9052) located at 1600 Grant Ave. S, Renton, WA 98055. This project is the continuation of an expired plat (civil permit no. U16004475); currently, the site is partially developed with several constructed buildings, building foundations, utilities, and rough-graded alley. Stormwater onsite is collected by the onsite storm system and conveyed into a combined detention/wetvault, which discharges through a Contech StormFilter manhole and into the municipal storm system within Grant Ave. Low Impact Development (LID) BMPs are generally infeasible onsite due to unsuitable soils, high/perched groundwater, and the amount of completed construction onsite. A letter from a licensed geotechnical engineer has been added to the 2005 geotechnical investigation to confirm site conditions and to approve construction to continue as proposed. The City of Renton has amended the 2021 King County Stormwater Design Manual (KCSWDM) to create the 2022 City of Renton Surface Water Design Manual (CoRSWDM), which serves as the governing document for stormwater management within the city. This report shall serve to comply with the updated requirements of this manual and the Renton Municipal Code. FES Project no. 20069 Page 4 Technical Information Report (TIR) Worksheet FES Project no. 20069 Page 5 FES Project no. 20069 Page 6 FES Project no. 20069 Page 7 FES Project no. 20069 Page 8 FES Project no. 20069 Page 9 Vicinity Map Scale: NTS PROJECT SITE FES Project no. 20069 Page 10 2.0 CONDITIONS AND REQUIREMENTS SUMMARY Per KCSWDM Section 1.1, Figure 1.1.2.A: Flow Chart for Determining Type of Drainage Review Required, this project is required to comply with Full Drainage Review per Section 1.1.2.4: Therefore, this project must comply with all nine core requirements in Section 1.2 and all five special requirements in Section 1.3. FES Project no. 20069 Page 11 2.1 Analysis of the Nine (9) Core Requirements 2.1.1 Core Requirement #1: Discharge at the Natural Location This project is a continuation of an expired permit, with a previously-designed stormwater system onsite discharging from the site into the municipal storm system through the existing manhole in Grant Ave. This project proposes discharge through this system. Therefore, the existing drainage pattern is maintained under the developed condition. See Section 3.4 of this report. FES Project no. 20069 Page 12 2.1.2 Core Requirement #2: Offsite Analysis See Section 3.0: Offsite Analysis. 2.1.3 Core Requirement #3: Flow Control Per CORMaps and the CoRSWDM, this project is required to provide flow control, and must implement the Flow Control Duration Standard matching forested site conditions. Therefore, the existing/predeveloped condition shall be modeled as forest. See Section 4.0: Flow Control, Low Impact Development (LID), and Water Quality Facility Analysis and Design. 2.1.4 Core Requirement #4: Conveyance System Conveyance shall be primarily through 12” CMP pipe; see Section 5.0: Conveyance System Analysis and Design. 2.1.5 Core Requirement #5: Erosion and Sediment Control A Temporary Erosion and Sediment Control (TESC) plan is included separately as a part of this submittal. 2.1.6 Core Requirement #6: Maintenance and Operations Maintenance and operations instructions and a sample log of maintenance activities are provided in Section 10.0 of this report. 2.1.7 Core Requirement #7: Financial Guarantees and Liability Bond quantity analysis will be provided separately at final approval. 2.1.8 Core Requirement #8: Water Quality Because this project proposes the development of a multifamily project, Enhanced Basic Water Quality is required per CoRSWDM Section 1.2.8.1(A). Water quality will be provided by a two-facility treatment train consisting of a combined detention/wet vault and a ConTech Stormfilter with ZPG filters. See Section 4.2: Water Quality System. 2.1.9 Core Requirement #9: Flow Control BMPs This project was evaluated per CoRSWDM Section 1.2.9.2.2: Large Lot BMP Requirements: 1. Full dispersion: Dispersion is not feasible on this project due to insufficient vegetated flowpath. 2. Full infiltration of roof runoff: Infiltration is not feasible on this project due to unsuitable soils and high/perched groundwater. 3. Where (1) and (2) are infeasible, the following BMPs must be evaluated for feasibility: a. Full infiltration: Infiltration is not feasible on this project due to unsuitable soils and high/perched groundwater. b. Limited infiltration: Infiltration is not feasible on this project due to unsuitable soils and high/perched groundwater. c. Bioretention: Bioretention is not feasible due to unsuitable soils and high/perched groundwater. d. Permeable Pavement: Permeable pavement is not feasible due to unsuitable soils and high/perched groundwater and slopes greater than 5%. FES Project no. 20069 Page 13 4. All target surfaces not mitigated by Requirements (1), (2), and (3) above must be mitigated to the maximum extent feasible using Basic Dispersion. Dispersion is not feasible due to insufficient vegetated flow path. 5. For projects that will result in an impervious surface coverage on the buildable portion of the site/lot of less than 45%, flow control BMPs must be applied to 50% of target impervious surfaces. There are no feasible flow control BMPs from requirements (1), (2), (3), and (4) above. Native Growth Retention Credit shall be applied to the proposed 2,595 square-foot native growth protection area (NGPA). 6. The soil moisture holding capacity of new pervious surfaces must be protected in accordance with the soil amendment BMP as detailed in Appendix C, Section C.2.13. Disturbed soil shall be amended with compost. 7. Any proposed connection of roof downspouts to the local drainage system must be via a perforated pipe connection as detailed in Appendix C, Section C.2.11. Roof drain connections shall be composed of perforated pipe. 2.2 Analysis of the Special Requirements 2.2.1 Special Requirement No. 1: Other Adopted Area-Specific Requirements. • Critical Drainage Areas (CDAs): There are no CDAs adopted in King County at this time. • Master Drainage Plans (MDPs): This project is not a part of an MDP. • Basin Plans (BPs): This project is subject to the City of Renton Shoreline Master Program. • Salmon Conservation Plans (SCPs): This project is subject to the requirements of the WRIA 9 Salmon Habitat Plan. • Stormwater Compliance Plans (SWCPs): This project is subject to the provisions of the 2022 King County Stormwater Management Program Plan (SWMP). • Lake Management Plans (LMPs): No known LMPs apply to this project. • Hazard Mitigation Plan: This project is subject to the requirements of the King County FHMP and the City of Renton’s Hazard Mitigation Plan. • Shared Facility Drainage Plans (SFDPs): This project is not subject to shared facility drainage requirements. 2.2.2 Special Requirement No. 2: Flood Hazard Area Delineation There are no flood hazards on or adjacent to the site; see Section 3.2 of this report. 2.2.3 Special Requirement No. 3: Flood Protection Facilities N/A 2.2.4 Special Requirement No. 4: Source Control N/A 2.2.5 Special Requirement No. 5: Oil Control N/A 2.2.6 Special Requirement No. 6: Aquifer Protection Area N/A 2.3 Conditions of Approval Reserved. FES Project no. 20069 Page 14 3.0 OFFSITE ANALYSIS 3.1 Task 1: Define and Map the Study Area. See the Downstream Map at the end of this section. A level 1 downstream analysis was performed by pacific engineering design, llc, and is attached to this report as appendix A. 3.2 Task 2: Review All Available Information on the Study Area King County iMap was used to review the site and the area approximately ½ mile downstream: Category Project Site Within ¼ mi. downstream Environmentally Sensitive Areas Tributary basin (2005 CAO) Lower Lower Potential landslide hazard areas No No Potential landslide hazard areas 50-foot buffer No No Landslide hazards, incorporated KC No No Potential steep slope hazard areas No No Basin condition (2005 CAO) Low Low Shoreline condition (2005 CAO) N/A N/A Erosion hazard (1990 SAO) Yes No Seismic hazard (1990 SAO) No No Coal Mine hazard (1990 SAO) Yes Yes Stream (1990 SAO) No Unclassified Wetland (1990 SAO) No No Sensitive area notice on title No No Chinook distribution No No Wildlife network No No Channel migration hazard areas No No Flooding info River gages N/A N/A Flood photos N/A N/A River miles from flood patrol map book N/A N/A River facilities N/A N/A Flood phases N/A N/A Elevation certificates N/A N/A Letter of Map Amendment and Revisions N/A N/A FEMA cross-sections N/A N/A FEMA FIRM panels 53033C0979G 53033C0979G FEMA floodway N/A N/A FEMA 100-year floodplain N/A N/A FEMA 500-year floodplain N/A N/A FEMA area with reduced risk due to levee No No Regulatory floodplain No No King County sea level rise risk area No No Groundwater Groundwater sources N/A N/A Groundwater quality sampling sites No No Groundwater management areas South King County South King County Areas susceptible to groundwater contamination Low Low Critical aquifer recharge area No No Sole source aquifer No No Wellhead protection areas – one year time of travel No No Wellhead protection areas – five years time of travel No No Wellhead protection areas – ten years time of travel Yes Yes Water service area City of Renton City of Renton FES Project no. 20069 Page 15 Category Project Site Within ¼ mi. downstream Hydrography and Hydrology Hydrogauges N/A N/A Lake buoy N/A N/A Lakes and large rivers N/A N/A Streams N/A N/A Drainage basin Black River Black River Water resource inventory areas Duwamish-Green (09) Duwamish-Green (09) River Corridor Mapping Historical Landslides No No Fans and debris flows No No Rock fall No No Deep-seated landslide No No Shallow debris slides No No Noxious weeds No No Stormwater Services Stormwater Facilities N/A N/A Drainage studies N/A N/A Neighborhood drainage projects N/A N/A Surface water engineering projects N/A N/A Drainage complaints N/A N/A Surface Water Design Manual Flow control N/A N/A Water quality N/A N/A The City of Renton’s GIS resources were also reviewed: Category Project Site Within ¼ mi. downstream Coalmines Severity: Moderate Severity: Moderate Erosion Hazard Severity: High Severity: High Flood N/A N/A Landslide Hazard Severity: Moderate Severity: Moderate Regulated Slopes >15%, ≤25% >15%, ≤25%, >25%, ≤40% Seismic Hazard Areas No No Seismic Faults Yes Yes Regulated Shoreline N/A N/A Wetlands N/A N/A Wellhead Protection Area N/A N/A Streams (classified) N/A Thunder Hills Creek Classification Type: Np – Non-Fish Water Feature Type: Stream 3.3 Task 3: Field Inspect the Study Area A site visit was performed by Dean A. Furr of Furr Engineering Services to confirm the findings of the downstream analysis performed by Pacific Engineering. See Appendix A: Pacific Engineering Downstream Analysis. 3.4 Task 4: Describe the Drainage System Site drainage is collected into a vault, which discharges into the municipal storm system in Grant Ave. Water is discharged through a 15-inch culvert across Grant Ave, then sheet-flows northwest along a vegetated path. See the downstream map and table at the end of this section. ABC D PROJECT SITE ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 GRANT PLACE TOWNHOMESDOWNSTREAM MAPRCE 4/1/2024 20069 DOWNSTREAM FLOWPATH N STORM STRUCTURE FES Project no. 20069 Page 17 Downstream Table 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 % ¼ 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. A Site discharge — — N/A — Onsite SWPPP measures in place during construction. A→B 12” CMP conveyance 28 N/A N/A B Type 2 storm drain manhole 28 N/A N/A B→C 15” CMP culvert 96 N/A N/A C Culvert outlet 96 N/A Damage from wildlife, overgrowth by vegetation C→D Sheet flow 1,320 N/A N/A D Terminus of downstream analysis 1,320 N/A — FES Project no. 20069 Page 18 4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN This project is a continuation of an expired plat and is currently partially-constructed. Refer to civil permit no. U16004475 for previous site conditions. See the existing Conditions Exhibit at the end of this section. Table 1, below, shows a breakdown of proposed project subbasins: SUBBASINS sf ac ONSITE 90,186 2.070 ONSITE BYPASS 2,739 0.063 FRONTAGE 2,547 0.058 UPSTREAM BACKYARDS 9,583 0.220 Table 1: Project subbasin breakdown. The proposed conditions are summarized in the tables below: ONSITE WWHM LANDUSE TYPE DESCRIPTION sf ac BASIN TOTAL DISTURBED AREA 90,186 2.070 IMPERVIOUS TOTAL IMPERVIOUS 63,597 1.460 PGHS 25,756 0.591 ROADS/MOD ROAD 23,330 0.536 DRIVEWAYS/FLAT VAULT ACCESS 2,426 0.056 NON-PGHS 37,841 0.870 ROOF TOPS/FLAT TOWNHOUSE ROOFS 28,171 0.647 SIDEWALKS/FLAT SIDEWALKS 8,562 0.197 SIDEWALKS/FLAT RETAINING WALLS 1,108 0.025 C, LAWN, MOD PERVIOUS (LS) 23,994 0.551 C, FOREST, MOD NGPA 2,595 0.060 Table 2: Proposed onsite conditions area breakdown. ONSITE BYPASS WWHM LANDUSE TYPE DESCRIPTION sf ac BASIN TOTAL DISTURBED AREA 2,739 0.063 IMPERVIOUS TOTAL IMPERVIOUS 1,683 0.039 PGHS 1,310 0.030 ROADS/MOD ROAD 1,310 0.030 NON-PGHS 373 373 SIDEWALKS/MOD SIDEWALKS 373 0.009 C, LAWN, MOD PERVIOUS (LS) 1,056 0.024 Table 3: Proposed onsite bypass area breakdown. FES Project no. 20069 Page 19 FRONTAGE WWHM LANDUSE TYPE DESCRIPTION sf ac BASIN TOTAL DISTURBED AREA 2,547 0.058 IMPERVIOUS TOTAL IMPERVIOUS 1,554 0.036 PGHS 716 0.016 ROADS/FLAT ROAD 716 0.016 NON-PGHS 838 0.019 SIDEWALKS/FLAT SIDEWALKS 838 0.019 C, LAWN, MOD PERVIOUS (LS) 993 0.023 Table 4: Proposed offsite frontage area breakdown. UPSTREAM WWHM LANDUSE TYPE DESCRIPTION sf ac C, LAWN, MOD PERVIOUS (LS) 9,583 0.220 Table 5: Upstream tributary area breakdown. See the Developed Conditions Exhibit at the end of this section. WWHM 2012 was used to model the site using the inputs in Table 6, below: WWHM INPUTS AC PREDEVELOPED - TOTAL 2.192 C, FOREST, FLAT 0.135 C, FOREST, MOD 1.304 C, FOREST, STEEP 0.752 PREDEVELOPED - UPSTREAM 0.220 C, LAWN, MOD 0.220 DEVELOPED - ONSITE 2.070 C, FOREST, MOD 0.060 C, LAWN, MOD 0.551 ROADS/MOD 0.536 ROOF TOPS/FLAT 0.647 DRIVEWAYS/FLAT 0.056 SIDEWALKS/MOD 0.222 DEVELOPED - BYPASS 0.063 C, LAWN, MOD 0.024 ROADS/MOD 0.030 SIDEWALKS/MOD 0.009 DEVELOPED - FRONTAGE 0.058 C, LAWN, MOD 0.023 ROADS/FLAT 0.016 SIDEWALKS/FLAT 0.019 DEVELOPED - UPSTREAM 0.220 C, LAWN, MOD 0.220 Table 6: WWHM inputs. The existing (historic) condition is modelled as forest, using hydrologic soil group C. Run-on from the upstream area and from the frontage improvements to Grant Ave. are considered bypass. FES Project no. 20069 Page 20 4.1 VAULT ANALYSIS An onsite storm system, designed by others, has been installed. This system was analyzed in order to determine the system’s available capacity and to design storm drainage meeting the flow control and water quality requirements. Table 7, below, summarizes the as-built data analysis, and the available live and dead storage: (a) Vault length (ft) 90.08 (b) Vault width (ft): 40.8 (c) Vault area (sf): 3,764 (d) Water quality outlet ie: 290.87 (e) Min. freeboard (ft): 0.5 (f) Min. sediment storage (ft): 0.5 Vault access (g) Inside roof elevation (h) Floor elevation (i) Vault depth (ft) (j) Dead storage depth (ft) (k) Dead storage volume (cf) 1 299.71 286.55 13.16 3.82 15,874 2 299.52 286.44 13.08 3.93 16,278 3 299.73 286.21 13.52 4.16 17,123 4 299.71 285.28 14.43 5.09 20,540 5 299.72 285.58 14.14 4.79 19,438 6 299.73 284.92 14.81 5.45 21,863 7 299.71 284.91 14.80 5.46 21,900 8 299.67 284.89 14.78 5.48 21,973 Avg. 299.69 285.60 14.09 4.77 17,535 (m) High water surface elevation: 299.05 (n) Live storage depth (ft): 8.15 (o) Live storage volume (cf): 29,960 Table 7: as-built storage volume calculations. Values in the table were calculated as follows: (a) Vault length (ft): As-built vault length. (b) Vault width (ft): As-built vault width. (c) Vault area (cf): (a)*(b) (d) Water quality outlet ie: As-built outlet invert elevation. (e) Min. freeboard (ft): Minimum required freeboard per CoRSWDM. (f) Min. sediment storage (ft): Minimum required sediment depth per CoRSWDM. (g) Inside roof elevation: As-built inside roof elevation. (h) Floor elevation: As-built floor elevation. (i) Vault depth (ft): (g) - (h) (j) Dead storage depth (ft): (d) - (h) - (f) (k) Dead storage volume (cf): (i)*(c) (m) High water surface elevation: [minimum (g)] - (d) (n) Live storage depth (ft): (m) – (d) (o) Live storage volume (cf): (n)*(c) Therefore, the existing combined detention/wetvault provides an approximate live storage volume of 29,960 cf and an average dead storage volume of 17,535 cf. The proposed detention vault system and outlet riser were modeled in WWHM using the following parameters: FES Project no. 20069 Page 21 PROPOSED VAULT SYSTEM Riser height (ft) 8.15 Width (ft) 90.06 Length (ft) 40.80 Volume (cf) 29,960 Riser diameter (in) 18 Riser type Notched Notch type Rectangular Notch height (ft) 1.900 Notch width (ft) 0.010 Orifice diameter (in) at 0 ft elevation 0.910 Orifice diameter (in) at 4 ft elevation 0.980 Table 8: WWHM design parameters. This vault system shall be sufficient to provide the required level of flow control; see Appendix D: Flow Control and Water Quality Calculations. Frontage section and by-pass basin were included as by-pass mitigation as per City of Renton Storm water manual section 1.2.3.2(E): flow control facility was sized to compensate for the by- pass areas and inflow from lawn areas above. Resulted flow frequencies are provided in table 9. RETURN PERIOD FLOW FREQUENCY (CFS) 501, Historical 701, Unmitigated 801, Mitigated 2-YEAR 0.0908 0.6917 0.0561 5-YEAR 0.1519 0.9015 0.0840 10-YEAR 0.1965 1.0506 0.1060 25-YEAR 0.2563 1.2508 0.1383 50-YEAR 0.3029 1.4090 0.1658 100-YEAR 0.3509 1.5750 0.1964 Δ100-YEAR 1.2241 Table 9: Historic and Developed flow rates TO BE USED IN BACKFLOW ANALYSIS, TO SIMILATE VAULT OVERFLOW ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 GRANT PLACE TOWNHOMESFIGURE XXXX: EXISTING CONDITIONS EXHIBITRCE 3/17/2023 20069 ROOF ASPHALT (ONSITE) CONCRETE (ONSITE) GRAVEL ASPHALT (OFFSITE) CONCRETE (OFFSITE) LEGEND N PROPERTY BOUNDARY DISTURBED AREA FLAT SLOPE, <5% MODERATE SLOPE, 5-15% STEEP SLOPE, >15% FES Project no. 20069 Page 23 4.2 WATER QUALITY SYSTEM Enhanced Basic Level Water Quality will be provided by a treatment train of a combined wet/detention vault and a Stormfilter unit. WWHM was used to calculate the required water quality volume of 0.2144 ac•ft (9,339 cf); see Appendix D: Flow Control and Water Quality Calculations. The existing vault provides 17,534 cf dead storage (see Table 7); therefore, the existing vault shall be sufficient to provide the required water quality volume for the first stage of the treatment train. The second stage of the treatment train shall consist of a ConTech StormFilter manhole. This product is approved for General Use Level for Basic Treatment by the Washington State Department of Ecology, using either PhosphoSorb or ZPG media. See Appendix E: StormFilter Details. See table 10 for calculations. WATER QUALITY DESIGN DATA Effective Cartridge Height (inches) 12 18 27 Cartridge Flow Rate (gpm/cartridge) 5 7.5 11.3 Cartridge Flow Rate (cfs/cartridge) 0.0134 0.0167 0.0302 WQ flow rate (cfs) 0.0266 Peak flow rate (cfs) (see section 5.1) 0.1153 Required number of cartridges 9 7 4 Provided capacity (cfs) 0.1206 0.1169 0.1208 Table 10: Water quality design ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 RCE 4/1/2024 20069 GRANT PLACE TOWNHOMESDEVELOPED CONDITIONS EXHIBITROOF ASPHALT CONCRETE GRASSCRETE LEGEND N PROPERTY BOUNDARY SUBBASIN BOUNDARY OFFSITE SUBBASIN ONSITE SUBBASIN ONSITE BYPASS SUBBASIN FES Project no. 20069 Page 25 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 5.1 Uniform Flow Analysis Method The constructed stormwater conveyance system onsite consists typically of 12” corrugated storm pipe and was analyzed using Manning’s equation in order to ensure sufficient capacity. 𝑄=1.49 𝑛∗𝐴∗𝑅௛ ଶ ଷ ∗𝑆ଵ ଶ where 𝑛= Manning’s coefficient = 0.012 𝑄= flow 𝐴= area 𝑅௛ = hydraulic radius 𝑆= pipe slope The most constrained pipe in the system shall be considered; see Appendix C: As-Built Survey drawings. Given: 𝐴= 0.785 sf 𝑅௛ = 4” 𝑆= 0.041 𝑄=1.49 0.012 ∗ 0.785 ∗(0.25)ଶ ଷ ∗(0.041)ଵ ଶ = 7.842 𝑐𝑓𝑠(5.1) at 100% pipe capacity, and 4.705 cfs at 60% capacity. Given 100-year peak flows of 1.5750 cfs, each component of the conveyance system is sufficient to convey peak flows at 60% capacity. Additionally, discharge from the vault must be considered, based upon the most constrained pipe: 𝑄=1.49 0.012 ∗ 0.785 ∗(0.25) ଶ ଷ ∗(0.002) ଵ ଶ = 1.669 𝑐𝑓𝑠(5.2) at 100% pipe capacity, and 1.002 cfs at 60% capacity. Therefore, all pipes downstream of the vault shall have sufficient capacity to convey the peak flows of 0.1964 cfs. Peak flow to the water quality facility shall consist of peak theoretical flow that can pass through the orifices on the riser. There are two orifices with thin wall 𝐶ௗ = 0.61. Orifice 1: Dia. 0.91” at elevation 0.0’ (8.15’ of static head) 𝐴ଵ =𝜋𝑟ଶ = 3.14 ⋅ 0.91" 12 ⋅ 2 = 0.0045𝑠𝑓 𝑄ଵ,௣௘௔௞ =𝐶ௗ𝐴ଵඥ2𝑔𝐻= 0.61⋅ 0.0045 ⋅√2 ⋅ 32.17 ⋅ 8.15 = 0.0631 𝑐𝑓𝑠 (5.3) Orifice 2: Dia. 0.98” at elevation 4.0’ (4.15’ of static head) 𝐴ଶ =𝜋𝑟ଶ = 3.14 ⋅ 0.98" 12 ⋅ 2 = 0.0052𝑠𝑓 𝑄ଶ,௣௘௔௞ =𝐶ௗ𝐴ଶඥ2𝑔𝐻= 0.61⋅ 0.0052 ⋅√2 ⋅ 32.17 ⋅ 4.15 = 0.0522 𝑐𝑓𝑠 (5.4) Total: 𝑄௣௘௔௞ = 0.0631+ 0.0522 = 0.1153 𝑐𝑓𝑠 FES Project no. 20069 Page 26 6” ROOF DRAIN ANALISYS Peak 100 years flow from buildings 8, 7 and 6 according to WWHM will be 0.0698 CFS, and 6” PVC pipe capacity at 100% is 2.35 CFS, and 1.58 CFS at 60% capacity. Therefore, roof drain conveyance system is sufficient to convey peak flows at 60% capacity. 𝑄=1.49 𝑛∗𝐴∗𝑅௛ ଶ ଷ ∗𝑆ଵ ଶ =1.49 0.012 ∗ 0.196 ∗(0.125)ଶ ଷ ∗(0.15)ଵ ଶ = 2.35 𝑐𝑓𝑠 Where: 𝑛= 0.012 − Manning’s coefficient, 𝑄− peak flow, 𝐴= 0.196 𝑆𝐹− area, 𝑅௛ = 1.5" hydraulic radius, 𝑆= 0.15 pipe slope. 5.2 Backflow Analysis Method Backflow analysis was performed for 100 years flow, for each catch basin as per City of Renton Storm water manual section 4.2.1.2. Flows for each catch basin were calculated with WWHM 2012. Sub-basin division is summarized in table 11. Results are presented in the table 12. Exhibit with WWHM Printouts is presented at Appendix D. For the pipe section between the vault and existing street SDMH-1 100 years maximum unmitigated flow of Q=1.5750 CFS was used. For the route between the vault and existing street SDMH-1 via storm filter manhole maximum possible water quality flow of Q=0.1153 CFS was utilized. # Surface area, AC Q100, CFS TOTAL DRIVEWAY SIDEWALK ROOF PERVIOUS CB1 0.000 0.000 0.000 0.000 0.000 0.0000 CB2 0.058 0.018 0.017 0.000 0.023 0.0373 CB3 0.335 0.201 0.006 0.090 0.038 0.2603 CB4 0.177 0.028 0.028 0.000 0.121 0.0940 CB6 0.209 0.062 0.000 0.146 0.001 0.1693 CB7 0.042 0.002 0.016 0.000 0.024 0.0231 CB8 0.085 0.051 0.013 0.000 0.021 0.0638 CB9 0.096 0.045 0.002 0.005 0.044 0.0611 CB10 0.095 0.053 0.000 0.027 0.015 0.0748 CB11 0.094 0.051 0.000 0.027 0.015 0.0733 CB12 0.024 0.021 0.001 0.000 0.002 0.0209 CB13 0.121 0.024 0.035 0.000 0.063 0.0700 CB15 0.164 0.000 0.030 0.072 0.063 0.0990 CB16 0.158 0.000 0.035 0.066 0.057 0.0964 CB17 0.144 0.000 0.028 0.066 0.050 0.0886 CB18 0.033 0.000 0.007 0.000 0.025 0.0164 Table 11: Sub-Basins per each catch basin. CB1CB2CB15CB3CB4CB16CB17CB18CB7CB6CB13CB12CB11CB10CB9CB8BY-PASSYARD DRAINSDIRECTLY TOTHE VAULTTIGHTLINE TO CB3TIGHTLINE TO CB3TIGHTLINE TO CB3DISTANCE BETWEEN CATCH BASINS 381'30'FLAT DWFLAT DW5.4%6.9%8.8%14.9%15.0%8.5%9.1%6.1%7.5%2.9%3.1%14.2%4.1%15.0%ph 206.890.82914715 142nd Pl. SW #B,Edmonds, WA 98026NMFE5/13/202420069GRANT PLACE TOWNHOMES BACKFLOW ANALISYS EXHIBITROOFASPHALTCONCRETELEGEND FES Project no. 20069 Page 28 Backflow Analysis Table JOB NAME: Grant Place Townhomes PREPARED BY: Feliks Matveev JOB NUMBER: 20069 DESIGN STORM: 100 YEAR FROM CB TO CB FLOW, CFS PIPE LENGTH (FEET) PIPE DIA. (IN) MANN- ING'S n VALUE OUTLET ELEV. (FEET) INLET ELEV. (FEET) PIPE AREA (SQ FT) FLOW VELO- CITY (FT/SEC) VELO- CITY HEAD (FEET) TAIL- WATER ELEV. (FEET) FRIC- TION LOSS (FEET) ENTRANCE HGL ELEV. (FEET) ENTRANCE HEAD LOSS (FEET) EXIT HEAD LOSS (FEET) OUTLET CONTROL ELEV. (FEET) INLET CONTROL ELEV. (FEET) APP- ROACH VELO- CITY HEAD (FEET) BEND HEAD LOSS (FEET) JUNC- TION HEAD LOSS (FEET) HEAD- WATER ELEV. (FEET) RIM EL VLT A7 CB8 0.56 23 12 0.012 288.61 300.63 0.79 0.71 0.01 299.02 0.00 301.63 0.00 0.01 301.64 301.63 0.01 0.01 0.00 301.65 303.51 CB8 CB9 0.49 80 12 0.012 300.63 312.18 0.79 0.63 0.01 301.65 0.01 313.18 0.00 0.01 313.19 313.18 0.00 0.00 0.00 313.18 315.61 CB9 CB10 0.43 85 12 0.012 312.18 315.99 0.79 0.55 0.00 313.18 0.01 316.99 0.00 0.00 317.00 316.99 0.00 0.00 0.00 316.99 319.95 CB10 CB11 0.36 102 12 0.012 315.99 323.97 0.79 0.45 0.00 316.99 0.01 324.97 0.00 0.00 324.97 324.97 0.00 0.00 0.00 324.97 327.12 CB11 CB12 0.28 105 12 0.012 323.97 332.19 0.79 0.36 0.00 324.97 0.01 333.19 0.00 0.00 333.19 333.19 0.00 0.00 0.00 333.19 335.03 CB12 CB13 0.26 42 12 0.012 332.19 336.82 0.79 0.33 0.00 333.19 0.00 337.82 0.00 0.00 337.82 337.82 0.00 0.00 0.00 337.82 340.50 CB13 CB6 0.19 52 12 0.012 336.82 341.04 0.79 0.24 0.00 337.82 0.00 342.04 0.00 0.00 342.04 342.04 0.00 0.00 0.00 342.04 345.11 CB6 CB7 0.02 102 12 0.012 341.04 349.02 0.79 0.03 0.00 342.04 0.00 350.02 0.00 0.00 350.02 350.02 0.00 0.00 0.00 350.02 354.83 VLT A1 CB15 0.39 31 12 0.012 289.21 312.67 0.79 0.50 0.00 299.02 0.00 313.67 0.00 0.00 313.68 313.67 0.00 0.00 0.00 313.67 317.65 CB15 CB16 0.30 101 12 0.012 312.67 323.03 0.79 0.38 0.00 313.67 0.01 324.03 0.00 0.00 324.03 324.03 0.00 0.00 0.00 324.03 325.13 CB15 CB17 0.20 101 12 0.012 312.67 332.34 0.79 0.25 0.00 324.03 0.00 333.34 0.00 0.00 333.34 333.34 0.00 0.00 0.00 333.34 334.47 CB17 CB18 0.11 106 12 0.012 332.34 337.59 0.79 0.14 0.00 333.34 0.00 338.59 0.00 0.00 338.59 338.59 0.00 0.00 0.00 338.59 341.06 CB18 CB4 0.09 55 12 0.012 337.59 337.92 0.79 0.12 0.00 324.03 0.00 338.92 0.00 0.00 338.92 338.92 0.00 0.00 0.00 338.92 340.59 VLT A2 CB1 0.30 33 12 0.012 288.98 302.54 0.79 0.38 0.00 299.02 0.00 303.54 0.00 0.00 303.54 303.54 0.00 0.00 0.00 303.54 307.04 CB1 CB2 0.30 14 12 0.012 302.54 304.50 0.79 0.38 0.00 303.54 0.00 305.50 0.00 0.00 305.50 305.50 0.00 0.00 0.00 305.50 307.00 CB2 CB3 0.26 12 12 0.012 304.50 306.00 0.79 0.33 0.00 305.50 0.00 307.00 0.00 0.00 307.00 307.00 0.00 0.00 0.00 307.00 308.85 VLT1 SFMH1 0.115 48 12 0.012 286.61 288.17 0.79 0.15 0.00 287.61 0.00 289.17 0.00 0.00 289.17 289.17 0.00 0.00 0.00 289.17 294.51 SFMH1 CB14 0.115 16 12 0.012 288.17 288.52 0.79 0.15 0.00 289.17 0.00 289.52 0.00 0.00 289.52 289.52 0.00 0.00 0.00 289.52 295.72 CB14 SDMH1 0.115 28 12 0.012 290.82 290.87 0.79 0.15 289.52 0.00 291.87 0.00 0.00 291.87 291.87 0.00 0.00 0.00 291.87 300.40 VLT1 CB14 1.575 48 12 0.012 286.61 288.37 0.79 0.15 0.00 287.61 0.00 289.37 0.00 0.00 289.37 289.37 0.00 0.00 0.00 289.40 294.51 CB14 SDMH1 1.575 34 12 0.012 288.37 295.37 0.79 0.15 0.00 289.40 0.00 296.57 0.00 0.00 296.57 296.57 0.00 0.00 0.00 296.69 297.70 Table 12: Backwater analysis calculation. 100 YR UNMITIGATED FLOW SEE SECTION 4.1 MAX WQ FACILITY FLOW SEE SECTION 5.1 FES Project no. 20069 Page 29 5.3 Grate Inlet Capacity Analysis To prove that no spills or the by-passes will happen to the Grant Ave from private road we’ve calculated grates inflow rates with following assumptions: 1. Per RSWDM 4.2.1.2 Installed vanity grates are assumed to be 95% open to account for possible debris accumulation. 2. Grates will accept the run-off from private road approximately 400 FL long, adjacent planters, sidewalk, and parking spaces. Roof runoff will be dispersed via splash block and sheet flow on the pavement. 3. Slopes are up to 15% on the road and up to 30% on the lawn. Cross slope is 2%/. 4. Linear drain will cut off all the remaining and by-passed runoff at the site entrance. 100-year storm flow was obtained with WWHM modeling for the backflow analysis on per catch basin basis and will be used as peak load. See WWHM report for individual catch basins in appendix D. In general, we can notice that the peak load will be on the CB-3 from the gutter flow along the south property line. And there is a possibility that some flow will bypass this grate. Peak 100-yr flow is: 𝑄=0.2603 𝑐𝑟𝑒 City of Renton Stormwater manual in section 4.2.1.2 [page 4-20] specifies Washington State Department of Transportation (WSDOT) Hydraulics Manual as a reference for the grate’s inflow capacity calculation. According to WSDOTHM Chapter 5-4.1 [page 5-7] grates on the slope need to be calculated as per Urban Drainage Desing by FHA [FHWA-HIF-24-006 or HES-22]. We’ll use FHWA-HIF-24-006 section 5.3.1 [HES-22, page 47] to calculate the standard city of Renton 12” concrete gutter capacity, figure 1. Figure 1: Gutter as per city of Renton standard details FES Project no. 20069 Page 30 As gutter slope is the same as pavement slope, we’ll utilize HES-22 equation 5.2 to calculate water spread capacity: 𝑄=(𝑄𝑛 𝐾𝑢𝑄𝑤1.67𝑄𝐿0.5) 0.375 =(0.2603 ⋅0.014 0.56 ⋅0.021.67 ⋅0.150.5) 0.375 =2.50 𝑒𝑟 (5.4) Where: 𝑛=0.014 – Manning’s n for the float finished concrete gutter as per HES-22 table 5.3 𝐾𝑢=0.56 – unit conversion constant for CU 𝑄𝑤=2%=0.02 – cross slope 𝑄𝐿=15%=0.15 – longitude slope Now we can calculate the flow speed at the gutter using HES-22 equation 5.3. 𝑉=2𝐾𝑢 𝑛𝑄𝑤0.67𝑄𝐿0.5𝑄0.67 =2 ⋅0.56 0.014 0.020.67 ⋅0.150.5 ⋅2.50.67 =4.17 𝑒𝑟 𝑟𝑒𝑐(5.5) City of Renton Standard detail 204.20 specifies vaned grate dimensions as 24” long and 20” wide for the cast iron detail to cover catch basin, figure 2. Figure 2: Vaned grate as per city of Renton standard details FES Project no. 20069 Page 31 We’ll use HES-22 section 7.2.1 [page 92] to estimate the 20”x24” cast iron vaned grate interception capacity. Let’s calculate frontal flow to total gutter ration as per equation 7.3: 𝐸0 =𝑄𝑤 𝑄=1 −(1 −(𝑉 𝑄) 2.67 )=1 −(1 −(1.66 2.50) 2.67 )=0.9453 (5.6) Where: 𝑉=1.66 𝑒𝑟 – grate inlet width perpendicular to the gutter as per standard detail. We can calculate the frontal flow efficiency with equation 7.5: 𝑄𝑑=1 −𝐾𝑢(𝑉−𝑉0)=1 −0.09(4.17 −6)=1.165 →𝑄𝑑=1 (5.7) Where: 𝑉=6 𝑒𝑟/𝑟 – splash-over velocity as per HES-22, figure 7.8, see figure 3. 𝐾𝑢=0.09 – unit conversion constant for CU Figure 3: Splash-over velocities as per HES-22 We can calculate the ratio of side flow intercepted with HES-22 equation 7.6: FES Project no. 20069 Page 32 𝑄𝑠=1 (1 +𝐾𝑢𝑉1.8 𝑄𝑤𝐾2.3 ) =1 (1 +0.15 ⋅4.171.8 0.02 ⋅22.3 ) =0.0333 (5.8) Total grate inlet efficiency is expressed as per HES-22 equation 7.7: 𝐸=𝑄𝑑𝐸0 +𝑄𝑠(1 −𝐸0)=1 ⋅0.9453 +0.0333(1 −0.9453)=0.9471 (5.9) Therefore, the flow that will by-pass CB-3 is: 𝑄𝑎𝑝=𝑄(1 −𝐸)=0.2603(1 −0.9471)=0.0138 𝑐𝑒𝑟(5.10) As per city of Renton standard detail 101.1, figure 4, there is a 1/2" recess around the inlet grate. “For locally depressed inlets, the quantity of flow reaching the inlet depends on the upstream gutter section geometry and not the locally depressed section geometry.” [HEC-22, Section 7.2, page 92] Figure 4: Grate and gutter relative positions By-pass flow will be added to CB-2 10 ft downstream of CB-3. 𝑄𝐵𝐵2 𝑑𝑢𝑘𝑘=𝑄𝐵𝐵2 +𝑄𝑎𝑝=0.0373 +0.0138 =0.0510 𝑐𝑒𝑟(5.11) Flow spread will be equal to: FES Project no. 20069 Page 33 𝑄=(𝑄𝑛 𝐾𝑢𝑄𝑤1.67𝑄𝐿0.5) 0.375 =(0.0510 ⋅0.014 0.56 ⋅0.021.67 ⋅0.150.5) 0.375 =1.359 𝑒𝑟<𝑉=1.66 𝑒𝑟(5.12) Flow speed will be equal to: 𝑉=2𝐾𝑢 𝑛𝑄𝑤0.67𝑄𝐿0.5𝑄0.67 =2 ⋅0.56 0.014 0.020.67 ⋅0.150.5 ⋅1.3590.67 =2.77 𝑒𝑟 𝑟𝑒𝑐<𝑉0 =6 𝑒𝑟 𝑟𝑒𝑐(5.13) Flow speed is lower than critical speed of 6 ft\sec. that equates to frontal interception efficiency of 𝑄𝑑=1. Therefore CB-2 grate won’t have splash over effect and will have enough capacity to intercept all the runoff and avoid flooding Grant AVE. Our proposal to mitigate the possibility of flooding Grant Ave can be describe as the following: 1. Install CB-3 at the southwestern corner of the parcel, at the gutter, edges of the structure to be no less than 10’ from ex. water main, 5’ from the edge of existing sewer pipe and with CB-4 390 LF upstream. CB-3 will serve as a main intake point for the sheet flow from the Southern part of the private Grant circle. The intake capacity of this single CB is enough to intercept 95% of the flow. 2. Install CB-2 at the curb, 10 FL downstream of CB-3. CB-2 grate has enough capacity to intercept flow that bypass CB-3. 3. Adjacent to CB-2 install 12” linear drain across Grant circle, 30 LF, perpendicular to the street alignment. The northern end of linear drain will be elevated higher, and the southern end will follow proposed slope of the street at 2% to CB-2. As the peak flow spread to CB- 2 is less than CD-2 grate width, such linear drain is utilized only to collect occasional runoff from the pavement upstream. Reticuline grate of 12” wide will have a splash over speed of 2 ft\sec (HES-22, fig.3). Even with a peak flow of 𝑄𝐵𝐵2 =0.0373 𝑐𝑒𝑟 distributed over the 30 FL of linear drain length, with peak speed of 2 ft\s, the resulting runoff water layer thickness will be: 𝑄=𝐻𝐾𝑉→𝐻=𝑄 𝐾𝑉=0.0373 30 ⋅2 =0.0006𝑒𝑟=0.00005=1 2000"≈0 (5.14) Therefore, the proposed linear drain has enough capacity to intercept the flow upstream as there is not enough flow to result substantial water layer at high speed to splash over the grate. 4. CB-1 remains at the existing location albeit rim elevation will be adjusted to the proposed grading. Due to location at local high point, it won’t intercept any flow. 5. CB-4 will be installed upstream and will be connected to the drainage system that runs at the middle of the parcel. FES Project no. 20069 Page 34 6.0 SPECIAL REPORTS AND STUDIES Geotechnical Engineering Evaluation prepared by Nelson Geotechnical Associates, dated June 10, 2005. Attached to this report as Appendix B. FES Project no. 20069 Page 35 7.0 OTHER PERMITS Development: PR23-000126 Land Use: LUA23-000283 Utility construction permit: U16004475 (for previous work, now expired) C23006099 Building (Multi-family) Building (retaining walls >4ft height) NPDES: WAR304993, expires 12/31/2025 FES Project no. 20069 Page 36 8.0 CSWPP ANALYSIS AND DESIGN A Stormwater Pollution and Prevention Plan (SWPPP) is submitted separately per the Department of Ecology. The requirements of the KCSWDM are satisfied as follows: 1. Clearing limits. Clearing limits are delineated on the Temporary Erosion and Sediment Control Plan and shall be marked onsite with high-visibility fencing. 2. Cover measures. Temporary and permanent cover measures shall be provided to protect disturbed areas, e.g., plastic covering, hydroseeding, etc. 3. Perimeter protection. Silt fencing shall be used to filter sediment downstream of disturbed areas. 4. Traffic area stabilization. A stabilized construction entrance has been constructed. 5. Sediment retention: The proposed vault is being used to collect sediment during construction. Silt fencing shall provide sediment retention at the perimeter of the site. 6. Surface water collection. The proposed vault shall be used to collect surface water. 7. Dewatering control. Dewatering is not anticipated as a part of this project. 8. Dust control. Dust control shall be provided by sprinkling, if required. 9. Flow control. Flow control shall be provided by the proposed vault. 10. Control pollutants: The following BMPs shall be employed to control pollutants, per KCSWDM D.2.2: • Concrete handling • Concrete washout area • Sawcutting and surfacing pollution prevention • Material delivery, storage, and containment • pH control for high pH water • Maintain protective BMPs • Manage the project 11. Protect existing and proposed flow control BMPs. This project does not include existing or proposed flow control BMPs requiring protection. 12. Maintain BMPs. Maintenance of BMPs shall be the responsibility of the Certified Erosion and Sediment Control Lead (CESCL), to be appointed by the contractor. 13. Manage the project. Coordination and timing of site development activities relative to ESC concerns shall be the responsibility of the CESCL. During the wet season (October 1 to April 30) any site with exposed soils shall be subject to the "Wet Season Requirements" contained in the ESC Standards. In addition to the ESC cover measures, these provisions include covering any newly-seeded areas with mulch and seeding as much disturbed area as possible during the first week of October to provide grass cover for the wet season. Prior to obtaining final construction approval, the site shall be stabilized, structural ESC measures (such as silt fences and sediment traps) shall be removed, and drainage facilities shall be cleaned as specified in the ESC Standards. FES Project no. 20069 Page 37 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Submitted separately. FES Project no. 20069 Page 38 10.0 OPERATIONS AND MAINTENANCE MANUAL FES Project no. 20069 Page 39 FES Project no. 20069 Page 40 FES Project no. 20069 Page 41 FES Project no. 20069 Page 42 FES Project no. 20069 Page 43 FES Project no. 20069 Page 44 FES Project no. 20069 Page 45 FES Project no. 20069 Page 46 FES Project no. 20069 Page 47 FES Project no. 20069 Page 48 FES Project no. 20069 Page 49 FES Project no. 20069 Page 50 FES Project no. 20069 Page 51 FES Project no. 20069 Page 52 FES Project no. 20069 Page 53 APPENDIX A: PACIFIC ENGINEERING DOWNSTREAM ANALYSIS FES Project no. 20069 Page 54 APPENDIX B: GEOTECHNICAL REPORT Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, Washington 98028 www.cobaltgeo.com (206) 331-1097 March 3, 2023 Satwant Singh pmvrsingh@gmail.com RE: Permit Renewal Proposed Townhomes 1600 Grant Avenue South Renton, Washington In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to discuss permit renewal. We note that much of the planned construction is nearly completed. It is our opinion that the construction can continue per plan. Based on our observations at the site and observations during periodic site visits during grading, we recommend routing runoff from impervious surfaces to the detention system. Infiltration systems are not feasible at this site due to several factors. These include the presence of glacial till soils which are nearly impermeable and act as an aquitard; location and elevations of new buildings (possible intrusion behind walls and into buildings); presence of shallow perched groundwater in many areas (zero to minimal clearance above groundwater); presence of newer structural fills over the native soils (not suitable to infiltrate into fills), and slope magnitudes generally in excess of 15 percent in most locations. We anticipate that final landscaping and any additional planned grading/construction will occur per the approved plans during the upcoming dry grading season. Sincerely, Cobalt Geosciences, LLC Phil Haberman, PE, LG, LEG 3/3/2023 Principal PH/sc FES Project no. 20069 Page 55 APPENDIX C: AS-BUILT SURVEY DRAWINGS TYEE SURVEYORS WWHM2012 PROJECT REPORT VAULT 20069 - exist. vault 3/19/2024 4:35:04 PM Page 2 General Model Information WWHM2012 Project Name:20069 - exist. vault Site Name:Grant Avenue Townhomes Site Address:1600 Grant Ave S City:Renton, WA Report Date:3/19/2024 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 20069 - exist. vault 3/19/2024 4:35:04 PM Page 3 Landuse Basin Data Predeveloped Land Use predeveloped Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.304 C, Forest, Flat 0.135 C, Forest, Steep 0.752 Pervious Total 2.191 Impervious Land Use acre Impervious Total 0 Basin Total 2.191 20069 - exist. vault 3/19/2024 4:35:04 PM Page 4 Basin 2 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.22 Pervious Total 0.22 Impervious Land Use acre Impervious Total 0 Basin Total 0.22 20069 - exist. vault 3/19/2024 4:35:04 PM Page 5 Mitigated Land Use ONSITE Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.06 C, Lawn, Mod 0.551 Pervious Total 0.611 Impervious Land Use acre ROADS MOD 0.536 ROOF TOPS FLAT 0.647 ROADS FLAT 0.056 SIDEWALKS MOD 0.222 Impervious Total 1.461 Basin Total 2.072 20069 - exist. vault 3/19/2024 4:35:04 PM Page 6 FRONTAGE Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.023 Pervious Total 0.023 Impervious Land Use acre ROADS FLAT 0.016 SIDEWALKS FLAT 0.019 Impervious Total 0.035 Basin Total 0.058 20069 - exist. vault 3/19/2024 4:35:04 PM Page 7 UPSTREAM Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.22 Pervious Total 0.22 Impervious Land Use acre Impervious Total 0 Basin Total 0.22 20069 - exist. vault 3/19/2024 4:35:04 PM Page 8 BYPASS Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.024 Pervious Total 0.024 Impervious Land Use acre ROADS MOD 0.03 SIDEWALKS MOD 0.009 Impervious Total 0.039 Basin Total 0.063 20069 - exist. vault 3/19/2024 4:35:04 PM Page 10 Mitigated Routing Vault 1 Width:40.8 ft. Length:90.06 ft. Depth:9.15 ft. Discharge Structure Riser Height:8.15 ft. Riser Diameter:18 in. Notch Type:Rectangular Notch Width:0.010 ft. Notch Height:1.900 ft. Orifice 1 Diameter:0.900 in.Elevation:0 ft. Orifice 2 Diameter:0.980 in.Elevation:4 ft. Element Flows To: Outlet 1 Outlet 2 Vault Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.084 0.000 0.000 0.000 0.1017 0.084 0.008 0.007 0.000 0.2033 0.084 0.017 0.009 0.000 0.3050 0.084 0.025 0.012 0.000 0.4067 0.084 0.034 0.014 0.000 0.5083 0.084 0.042 0.015 0.000 0.6100 0.084 0.051 0.017 0.000 0.7117 0.084 0.060 0.018 0.000 0.8133 0.084 0.068 0.019 0.000 0.9150 0.084 0.077 0.021 0.000 1.0167 0.084 0.085 0.022 0.000 1.1183 0.084 0.094 0.023 0.000 1.2200 0.084 0.102 0.024 0.000 1.3217 0.084 0.111 0.025 0.000 1.4233 0.084 0.120 0.026 0.000 1.5250 0.084 0.128 0.027 0.000 1.6267 0.084 0.137 0.028 0.000 1.7283 0.084 0.145 0.028 0.000 1.8300 0.084 0.154 0.029 0.000 1.9317 0.084 0.162 0.030 0.000 2.0333 0.084 0.171 0.031 0.000 2.1350 0.084 0.180 0.032 0.000 2.2367 0.084 0.188 0.032 0.000 2.3383 0.084 0.197 0.033 0.000 2.4400 0.084 0.205 0.034 0.000 2.5417 0.084 0.214 0.035 0.000 2.6433 0.084 0.223 0.035 0.000 2.7450 0.084 0.231 0.036 0.000 2.8467 0.084 0.240 0.037 0.000 2.9483 0.084 0.248 0.037 0.000 3.0500 0.084 0.257 0.038 0.000 3.1517 0.084 0.265 0.039 0.000 3.2533 0.084 0.274 0.039 0.000 3.3550 0.084 0.283 0.040 0.000 3.4567 0.084 0.291 0.040 0.000 3.5583 0.084 0.300 0.041 0.000 20069 - exist. vault 3/19/2024 4:35:04 PM Page 11 3.6600 0.084 0.308 0.042 0.000 3.7617 0.084 0.317 0.042 0.000 3.8633 0.084 0.325 0.043 0.000 3.9650 0.084 0.334 0.043 0.000 4.0667 0.084 0.343 0.051 0.000 4.1683 0.084 0.351 0.055 0.000 4.2700 0.084 0.360 0.059 0.000 4.3717 0.084 0.368 0.061 0.000 4.4733 0.084 0.377 0.064 0.000 4.5750 0.084 0.385 0.066 0.000 4.6767 0.084 0.394 0.069 0.000 4.7783 0.084 0.403 0.071 0.000 4.8800 0.084 0.411 0.073 0.000 4.9817 0.084 0.420 0.074 0.000 5.0833 0.084 0.428 0.076 0.000 5.1850 0.084 0.437 0.078 0.000 5.2867 0.084 0.445 0.080 0.000 5.3883 0.084 0.454 0.081 0.000 5.4900 0.084 0.463 0.083 0.000 5.5917 0.084 0.471 0.084 0.000 5.6933 0.084 0.480 0.086 0.000 5.7950 0.084 0.488 0.087 0.000 5.8967 0.084 0.497 0.089 0.000 5.9983 0.084 0.506 0.090 0.000 6.1000 0.084 0.514 0.092 0.000 6.2017 0.084 0.523 0.093 0.000 6.3033 0.084 0.531 0.095 0.000 6.4050 0.084 0.540 0.098 0.000 6.5067 0.084 0.548 0.101 0.000 6.6083 0.084 0.557 0.105 0.000 6.7100 0.084 0.566 0.109 0.000 6.8117 0.084 0.574 0.113 0.000 6.9133 0.084 0.583 0.117 0.000 7.0150 0.084 0.591 0.122 0.000 7.1167 0.084 0.600 0.126 0.000 7.2183 0.084 0.608 0.131 0.000 7.3200 0.084 0.617 0.136 0.000 7.4217 0.084 0.626 0.141 0.000 7.5233 0.084 0.634 0.147 0.000 7.6250 0.084 0.643 0.153 0.000 7.7267 0.084 0.651 0.174 0.000 7.8283 0.084 0.660 0.182 0.000 7.9300 0.084 0.668 0.190 0.000 8.0317 0.084 0.677 0.198 0.000 8.1333 0.084 0.686 0.206 0.000 8.2350 0.084 0.694 0.602 0.000 8.3367 0.084 0.703 1.479 0.000 8.4383 0.084 0.711 2.579 0.000 8.5400 0.084 0.720 3.734 0.000 8.6417 0.084 0.729 4.776 0.000 8.7433 0.084 0.737 5.573 0.000 8.8450 0.084 0.746 6.088 0.000 8.9467 0.084 0.754 6.541 0.000 9.0483 0.084 0.763 6.933 0.000 9.1500 0.084 0.771 7.304 0.000 9.2517 0.084 0.780 7.656 0.000 9.3533 0.000 0.000 7.993 0.000 20069 - exist. vault 3/19/2024 4:35:04 PM Page 13 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:2.411 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.878 Total Impervious Area:1.535 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.090822 5 year 0.151934 10 year 0.19652 25 year 0.256341 50 year 0.302924 100 year 0.350919 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.070413 5 year 0.09562 10 year 0.114486 25 year 0.140929 50 year 0.162608 100 year 0.186062 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.127 0.073 1950 0.140 0.074 1951 0.177 0.128 1952 0.060 0.049 1953 0.048 0.052 1954 0.068 0.052 1955 0.118 0.059 1956 0.097 0.086 1957 0.097 0.070 1958 0.083 0.056 20069 - exist. vault 3/19/2024 4:35:35 PM Page 14 1959 0.069 0.051 1960 0.137 0.117 1961 0.068 0.071 1962 0.046 0.046 1963 0.064 0.059 1964 0.093 0.058 1965 0.071 0.073 1966 0.055 0.052 1967 0.157 0.076 1968 0.086 0.072 1969 0.080 0.062 1970 0.067 0.059 1971 0.084 0.071 1972 0.141 0.097 1973 0.064 0.063 1974 0.081 0.065 1975 0.117 0.072 1976 0.080 0.061 1977 0.024 0.056 1978 0.066 0.061 1979 0.036 0.060 1980 0.198 0.099 1981 0.053 0.063 1982 0.149 0.129 1983 0.094 0.061 1984 0.059 0.050 1985 0.034 0.059 1986 0.148 0.090 1987 0.135 0.109 1988 0.054 0.050 1989 0.035 0.050 1990 0.355 0.137 1991 0.205 0.110 1992 0.077 0.059 1993 0.066 0.047 1994 0.025 0.044 1995 0.088 0.062 1996 0.224 0.128 1997 0.169 0.126 1998 0.060 0.065 1999 0.219 0.095 2000 0.067 0.062 2001 0.014 0.063 2002 0.087 0.094 2003 0.130 0.070 2004 0.144 0.134 2005 0.101 0.063 2006 0.103 0.068 2007 0.285 0.192 2008 0.305 0.152 2009 0.148 0.097 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.3554 0.1919 2 0.3048 0.1517 3 0.2848 0.1365 20069 - exist. vault 3/19/2024 4:35:35 PM Page 15 4 0.2244 0.1335 5 0.2193 0.1291 6 0.2047 0.1283 7 0.1978 0.1277 8 0.1774 0.1257 9 0.1687 0.1173 10 0.1572 0.1095 11 0.1490 0.1087 12 0.1479 0.0986 13 0.1476 0.0974 14 0.1441 0.0974 15 0.1410 0.0947 16 0.1402 0.0938 17 0.1372 0.0902 18 0.1354 0.0860 19 0.1302 0.0760 20 0.1270 0.0735 21 0.1180 0.0734 22 0.1169 0.0733 23 0.1034 0.0721 24 0.1013 0.0718 25 0.0974 0.0714 26 0.0966 0.0708 27 0.0944 0.0704 28 0.0926 0.0695 29 0.0880 0.0679 30 0.0867 0.0653 31 0.0859 0.0646 32 0.0844 0.0635 33 0.0830 0.0634 34 0.0814 0.0634 35 0.0804 0.0629 36 0.0803 0.0620 37 0.0769 0.0616 38 0.0705 0.0616 39 0.0693 0.0613 40 0.0684 0.0609 41 0.0679 0.0607 42 0.0671 0.0598 43 0.0668 0.0595 44 0.0660 0.0593 45 0.0659 0.0593 46 0.0641 0.0586 47 0.0637 0.0585 48 0.0605 0.0579 49 0.0604 0.0565 50 0.0586 0.0557 51 0.0546 0.0525 52 0.0538 0.0520 53 0.0526 0.0519 54 0.0477 0.0514 55 0.0458 0.0504 56 0.0356 0.0501 57 0.0347 0.0499 58 0.0336 0.0487 59 0.0249 0.0472 60 0.0237 0.0462 61 0.0135 0.0438 20069 - exist. vault 3/19/2024 4:35:35 PM Page 17 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0454 12820 11995 93 Pass 0.0480 11360 9794 86 Pass 0.0506 10029 8519 84 Pass 0.0532 8851 7649 86 Pass 0.0558 7880 6883 87 Pass 0.0584 7043 6254 88 Pass 0.0610 6286 5732 91 Pass 0.0636 5685 5272 92 Pass 0.0662 5093 4836 94 Pass 0.0688 4599 4402 95 Pass 0.0714 4156 4004 96 Pass 0.0740 3779 3625 95 Pass 0.0766 3433 3292 95 Pass 0.0792 3144 2954 93 Pass 0.0818 2868 2603 90 Pass 0.0844 2629 2224 84 Pass 0.0870 2368 1898 80 Pass 0.0896 2145 1602 74 Pass 0.0922 1931 1339 69 Pass 0.0948 1735 1085 62 Pass 0.0974 1567 878 56 Pass 0.1000 1418 730 51 Pass 0.1026 1259 627 49 Pass 0.1052 1128 531 47 Pass 0.1078 1052 466 44 Pass 0.1104 983 418 42 Pass 0.1130 918 377 41 Pass 0.1156 860 339 39 Pass 0.1182 800 296 37 Pass 0.1208 739 241 32 Pass 0.1234 668 201 30 Pass 0.1260 618 166 26 Pass 0.1286 559 128 22 Pass 0.1312 492 109 22 Pass 0.1338 439 84 19 Pass 0.1365 389 73 18 Pass 0.1391 340 64 18 Pass 0.1417 304 57 18 Pass 0.1443 259 52 20 Pass 0.1469 230 48 20 Pass 0.1495 197 45 22 Pass 0.1521 173 42 24 Pass 0.1547 149 39 26 Pass 0.1573 134 38 28 Pass 0.1599 116 32 27 Pass 0.1625 98 27 27 Pass 0.1651 87 26 29 Pass 0.1677 74 24 32 Pass 0.1703 64 22 34 Pass 0.1729 56 21 37 Pass 0.1755 48 18 37 Pass 0.1781 45 18 40 Pass 0.1807 41 17 41 Pass 20069 - exist. vault 3/19/2024 4:35:35 PM Page 18 0.1833 40 14 35 Pass 0.1859 36 11 30 Pass 0.1885 32 6 18 Pass 0.1911 30 2 6 Pass 0.1937 24 0 0 Pass 0.1963 23 0 0 Pass 0.1989 17 0 0 Pass 0.2015 14 0 0 Pass 0.2041 12 0 0 Pass 0.2067 9 0 0 Pass 0.2093 9 0 0 Pass 0.2119 9 0 0 Pass 0.2145 9 0 0 Pass 0.2171 8 0 0 Pass 0.2197 7 0 0 Pass 0.2223 7 0 0 Pass 0.2249 6 0 0 Pass 0.2275 6 0 0 Pass 0.2301 6 0 0 Pass 0.2327 6 0 0 Pass 0.2353 6 0 0 Pass 0.2379 6 0 0 Pass 0.2405 6 0 0 Pass 0.2431 5 0 0 Pass 0.2457 5 0 0 Pass 0.2483 5 0 0 Pass 0.2509 5 0 0 Pass 0.2535 5 0 0 Pass 0.2561 5 0 0 Pass 0.2587 5 0 0 Pass 0.2613 5 0 0 Pass 0.2639 4 0 0 Pass 0.2665 4 0 0 Pass 0.2691 4 0 0 Pass 0.2717 4 0 0 Pass 0.2743 4 0 0 Pass 0.2769 4 0 0 Pass 0.2795 4 0 0 Pass 0.2821 4 0 0 Pass 0.2847 4 0 0 Pass 0.2873 3 0 0 Pass 0.2899 3 0 0 Pass 0.2925 3 0 0 Pass 0.2951 2 0 0 Pass 0.2977 2 0 0 Pass 0.3003 2 0 0 Pass 0.3029 2 0 0 Pass 20069 - exist. vault 3/19/2024 4:35:35 PM Page 19 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.0795 acre-feet On-line facility target flow:0.0407 cfs. Adjusted for 15 min:0.0407 cfs. Off-line facility target flow:0.0266 cfs. Adjusted for 15 min:0.0266 cfs. 20069 - exist. vault 3/19/2024 4:35:44 PM Page 21 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. 20069 - exist. vault 3/19/2024 4:35:44 PM Page 22 Appendix Predeveloped Schematic 20069 - exist. vault 3/19/2024 4:35:45 PM Page 23 Mitigated Schematic WWHM2012 PROJECT REPORT INDIVIDUAL CB INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 2 General Model Information WWHM2012 Project Name:INDIVIDUAL-CB Site Name:Grant Place TH Site Address:1600 Grabt Ave S City:Renton Report Date:4/1/2024 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 POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year Low Flow Threshold for POC3:50 Percent of the 2 Year High Flow Threshold for POC3:50 Year Low Flow Threshold for POC4:50 Percent of the 2 Year High Flow Threshold for POC4:50 Year Low Flow Threshold for POC5:50 Percent of the 2 Year High Flow Threshold for POC5:50 Year Low Flow Threshold for POC6:50 Percent of the 2 Year High Flow Threshold for POC6:50 Year Low Flow Threshold for POC7:50 Percent of the 2 Year High Flow Threshold for POC7:50 Year Low Flow Threshold for POC8:50 Percent of the 2 Year High Flow Threshold for POC8:50 Year Low Flow Threshold for POC9:50 Percent of the 2 Year High Flow Threshold for POC9:50 Year Low Flow Threshold for POC10:50 Percent of the 2 Year High Flow Threshold for POC10:50 Year INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 3 Low Flow Threshold for POC11:50 Percent of the 2 Year High Flow Threshold for POC11:50 Year Low Flow Threshold for POC12:50 Percent of the 2 Year High Flow Threshold for POC12:50 Year Low Flow Threshold for POC13:50 Percent of the 2 Year High Flow Threshold for POC13:50 Year Low Flow Threshold for POC14:50 Percent of the 2 Year High Flow Threshold for POC14:50 Year Low Flow Threshold for POC15:50 Percent of the 2 Year High Flow Threshold for POC15:50 Year Low Flow Threshold for POC16:50 Percent of the 2 Year High Flow Threshold for POC16:50 Year INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 19 Mitigated Land Use CB2 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.023 Pervious Total 0.023 Impervious Land Use acre ROADS MOD 0.018 SIDEWALKS FLAT 0.017 Impervious Total 0.035 Basin Total 0.058 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 20 CB3 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.038 Pervious Total 0.038 Impervious Land Use acre ROADS FLAT 0.054 ROADS MOD 0.147 ROOF TOPS FLAT 0.09 SIDEWALKS FLAT 0.006 Impervious Total 0.297 Basin Total 0.335 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 21 CB4 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.121 Pervious Total 0.121 Impervious Land Use acre ROADS MOD 0.028 SIDEWALKS FLAT 0.028 Impervious Total 0.056 Basin Total 0.177 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 22 CB6 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.001 Pervious Total 0.001 Impervious Land Use acre ROADS MOD 0.062 ROOF TOPS FLAT 0.146 Impervious Total 0.208 Basin Total 0.209 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 23 CB18 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.025 Pervious Total 0.025 Impervious Land Use acre SIDEWALKS FLAT 0.008 Impervious Total 0.008 Basin Total 0.033 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 24 CB7 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.024 Pervious Total 0.024 Impervious Land Use acre ROADS MOD 0.002 SIDEWALKS FLAT 0.016 Impervious Total 0.018 Basin Total 0.042 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 25 CB8 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.021 Pervious Total 0.021 Impervious Land Use acre ROADS MOD 0.051 SIDEWALKS FLAT 0.013 Impervious Total 0.064 Basin Total 0.085 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 26 CB9 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.044 Pervious Total 0.044 Impervious Land Use acre ROADS MOD 0.045 ROOF TOPS FLAT 0.005 SIDEWALKS FLAT 0.002 Impervious Total 0.052 Basin Total 0.096 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 27 CB10 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.015 Pervious Total 0.015 Impervious Land Use acre ROADS MOD 0.053 ROOF TOPS FLAT 0.027 Impervious Total 0.08 Basin Total 0.095 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 28 CB11 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.016 Pervious Total 0.016 Impervious Land Use acre ROADS MOD 0.051 ROOF TOPS FLAT 0.027 Impervious Total 0.078 Basin Total 0.094 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 29 CB12 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.002 Pervious Total 0.002 Impervious Land Use acre ROADS MOD 0.021 SIDEWALKS FLAT 0.001 Impervious Total 0.022 Basin Total 0.024 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 30 CB13 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.062 Pervious Total 0.062 Impervious Land Use acre ROADS MOD 0.024 SIDEWALKS FLAT 0.035 Impervious Total 0.059 Basin Total 0.121 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 31 CB15 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.062 Pervious Total 0.062 Impervious Land Use acre ROOF TOPS FLAT 0.072 SIDEWALKS FLAT 0.03 Impervious Total 0.102 Basin Total 0.164 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 32 CB16 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.057 Pervious Total 0.057 Impervious Land Use acre ROOF TOPS FLAT 0.066 SIDEWALKS FLAT 0.035 Impervious Total 0.101 Basin Total 0.158 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 33 CB17 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.05 Pervious Total 0.05 Impervious Land Use acre ROOF TOPS FLAT 0.066 SIDEWALKS FLAT 0.028 Impervious Total 0.094 Basin Total 0.144 INDIVIDUAL-CB 4/1/2024 12:20:46 PM Page 37 POC 2 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #2 Total Pervious Area:0.058 Total Impervious Area:0 Mitigated Landuse Totals for POC #2 Total Pervious Area:0.023 Total Impervious Area:0.035 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #2 Return Period Flow(cfs) 2 year 0.001705 5 year 0.002678 10 year 0.00323 25 year 0.003814 50 year 0.004175 100 year 0.004483 Flow Frequency Return Periods for Mitigated. POC #2 Return Period Flow(cfs) 2 year 0.016085 5 year 0.021093 10 year 0.024668 25 year 0.029491 50 year 0.033312 100 year 0.037335 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #2 Year Predeveloped Mitigated 1949 0.002 0.023 1950 0.002 0.020 1951 0.004 0.014 1952 0.001 0.010 1953 0.001 0.012 1954 0.001 0.013 1955 0.002 0.015 1956 0.002 0.014 1957 0.002 0.017 1958 0.002 0.013 1959 0.001 0.013 INDIVIDUAL-CB 4/1/2024 12:21:17 PM Page 38 1960 0.003 0.015 1961 0.001 0.014 1962 0.001 0.011 1963 0.001 0.014 1964 0.002 0.013 1965 0.001 0.017 1966 0.001 0.011 1967 0.002 0.020 1968 0.001 0.024 1969 0.001 0.016 1970 0.001 0.015 1971 0.001 0.018 1972 0.003 0.020 1973 0.001 0.010 1974 0.001 0.018 1975 0.002 0.017 1976 0.001 0.014 1977 0.000 0.013 1978 0.001 0.017 1979 0.001 0.022 1980 0.003 0.026 1981 0.001 0.016 1982 0.002 0.024 1983 0.002 0.018 1984 0.001 0.011 1985 0.001 0.016 1986 0.003 0.014 1987 0.003 0.020 1988 0.001 0.012 1989 0.001 0.018 1990 0.005 0.034 1991 0.003 0.027 1992 0.001 0.012 1993 0.001 0.012 1994 0.000 0.011 1995 0.002 0.014 1996 0.004 0.019 1997 0.003 0.016 1998 0.001 0.015 1999 0.003 0.035 2000 0.001 0.016 2001 0.000 0.017 2002 0.001 0.021 2003 0.002 0.019 2004 0.002 0.033 2005 0.002 0.014 2006 0.002 0.013 2007 0.004 0.031 2008 0.005 0.025 2009 0.003 0.020 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #2 Rank Predeveloped Mitigated 1 0.0055 0.0347 2 0.0052 0.0337 3 0.0041 0.0326 4 0.0040 0.0310 INDIVIDUAL-CB 4/1/2024 12:21:17 PM Page 39 5 0.0038 0.0267 6 0.0033 0.0258 7 0.0033 0.0253 8 0.0031 0.0240 9 0.0030 0.0239 10 0.0028 0.0228 11 0.0027 0.0216 12 0.0026 0.0209 13 0.0026 0.0204 14 0.0025 0.0203 15 0.0024 0.0202 16 0.0023 0.0197 17 0.0023 0.0196 18 0.0021 0.0193 19 0.0020 0.0188 20 0.0020 0.0183 21 0.0019 0.0179 22 0.0019 0.0177 23 0.0019 0.0175 24 0.0018 0.0174 25 0.0018 0.0170 26 0.0017 0.0168 27 0.0017 0.0168 28 0.0017 0.0168 29 0.0016 0.0160 30 0.0015 0.0159 31 0.0015 0.0159 32 0.0015 0.0158 33 0.0014 0.0157 34 0.0014 0.0151 35 0.0014 0.0150 36 0.0014 0.0148 37 0.0014 0.0147 38 0.0014 0.0144 39 0.0013 0.0143 40 0.0013 0.0139 41 0.0013 0.0137 42 0.0013 0.0136 43 0.0012 0.0136 44 0.0012 0.0136 45 0.0012 0.0135 46 0.0012 0.0131 47 0.0012 0.0131 48 0.0012 0.0129 49 0.0011 0.0127 50 0.0011 0.0127 51 0.0011 0.0126 52 0.0010 0.0118 53 0.0010 0.0118 54 0.0009 0.0117 55 0.0008 0.0116 56 0.0007 0.0115 57 0.0007 0.0113 58 0.0007 0.0111 59 0.0004 0.0108 60 0.0002 0.0103 61 0.0002 0.0099 INDIVIDUAL-CB 4/1/2024 12:21:40 PM Page 45 POC 3 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #3 Total Pervious Area:0.335 Total Impervious Area:0 Mitigated Landuse Totals for POC #3 Total Pervious Area:0.038 Total Impervious Area:0.297 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #3 Return Period Flow(cfs) 2 year 0.009849 5 year 0.015469 10 year 0.018653 25 year 0.022027 50 year 0.024115 100 year 0.025891 Flow Frequency Return Periods for Mitigated. POC #3 Return Period Flow(cfs) 2 year 0.124521 5 year 0.158734 10 year 0.182143 25 year 0.212678 50 year 0.236162 100 year 0.260308 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #3 Year Predeveloped Mitigated 1949 0.010 0.164 1950 0.012 0.167 1951 0.022 0.099 1952 0.007 0.082 1953 0.006 0.096 1954 0.008 0.100 1955 0.014 0.118 1956 0.011 0.107 1957 0.009 0.124 1958 0.010 0.102 1959 0.008 0.107 INDIVIDUAL-CB 4/1/2024 12:22:10 PM Page 46 1960 0.015 0.108 1961 0.008 0.104 1962 0.005 0.092 1963 0.007 0.108 1964 0.009 0.105 1965 0.007 0.128 1966 0.006 0.087 1967 0.013 0.148 1968 0.008 0.184 1969 0.008 0.117 1970 0.007 0.116 1971 0.007 0.140 1972 0.016 0.138 1973 0.007 0.087 1974 0.008 0.130 1975 0.011 0.139 1976 0.008 0.102 1977 0.001 0.103 1978 0.007 0.140 1979 0.004 0.179 1980 0.015 0.179 1981 0.006 0.125 1982 0.012 0.179 1983 0.011 0.144 1984 0.007 0.089 1985 0.004 0.122 1986 0.017 0.107 1987 0.015 0.165 1988 0.006 0.100 1989 0.004 0.149 1990 0.032 0.221 1991 0.019 0.183 1992 0.007 0.089 1993 0.008 0.097 1994 0.003 0.091 1995 0.011 0.112 1996 0.023 0.135 1997 0.019 0.116 1998 0.004 0.118 1999 0.018 0.254 2000 0.008 0.120 2001 0.001 0.138 2002 0.008 0.151 2003 0.011 0.140 2004 0.014 0.241 2005 0.010 0.101 2006 0.012 0.093 2007 0.023 0.227 2008 0.030 0.174 2009 0.015 0.165 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #3 Rank Predeveloped Mitigated 1 0.0316 0.2537 2 0.0302 0.2413 3 0.0234 0.2271 4 0.0231 0.2210 INDIVIDUAL-CB 4/1/2024 12:22:10 PM Page 47 5 0.0217 0.1841 6 0.0193 0.1833 7 0.0190 0.1795 8 0.0181 0.1792 9 0.0171 0.1788 10 0.0162 0.1743 11 0.0153 0.1674 12 0.0151 0.1654 13 0.0148 0.1652 14 0.0147 0.1637 15 0.0138 0.1508 16 0.0135 0.1487 17 0.0134 0.1485 18 0.0121 0.1445 19 0.0118 0.1400 20 0.0117 0.1396 21 0.0110 0.1395 22 0.0108 0.1386 23 0.0108 0.1384 24 0.0106 0.1384 25 0.0105 0.1349 26 0.0099 0.1298 27 0.0098 0.1276 28 0.0097 0.1249 29 0.0093 0.1244 30 0.0087 0.1218 31 0.0085 0.1202 32 0.0084 0.1180 33 0.0084 0.1175 34 0.0083 0.1166 35 0.0083 0.1163 36 0.0082 0.1157 37 0.0080 0.1118 38 0.0078 0.1081 39 0.0076 0.1077 40 0.0076 0.1073 41 0.0073 0.1072 42 0.0073 0.1066 43 0.0072 0.1047 44 0.0071 0.1037 45 0.0068 0.1029 46 0.0068 0.1023 47 0.0067 0.1022 48 0.0067 0.1006 49 0.0065 0.1004 50 0.0064 0.1003 51 0.0061 0.0992 52 0.0060 0.0966 53 0.0055 0.0960 54 0.0051 0.0926 55 0.0044 0.0917 56 0.0041 0.0909 57 0.0039 0.0894 58 0.0039 0.0888 59 0.0026 0.0870 60 0.0014 0.0865 61 0.0009 0.0819 INDIVIDUAL-CB 4/1/2024 12:22:10 PM Page 53 POC 4 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #4 Total Pervious Area:0.177 Total Impervious Area:0 Mitigated Landuse Totals for POC #4 Total Pervious Area:0.121 Total Impervious Area:0.056 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #4 Return Period Flow(cfs) 2 year 0.005204 5 year 0.008173 10 year 0.009856 25 year 0.011638 50 year 0.012741 100 year 0.013679 Flow Frequency Return Periods for Mitigated. POC #4 Return Period Flow(cfs) 2 year 0.033077 5 year 0.046656 10 year 0.056696 25 year 0.07062 50 year 0.081917 100 year 0.094033 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #4 Year Predeveloped Mitigated 1949 0.005 0.052 1950 0.006 0.049 1951 0.011 0.030 1952 0.004 0.019 1953 0.003 0.020 1954 0.004 0.027 1955 0.007 0.029 1956 0.006 0.027 1957 0.005 0.037 1958 0.005 0.024 1959 0.004 0.020 INDIVIDUAL-CB 4/1/2024 12:22:40 PM Page 54 1960 0.008 0.033 1961 0.004 0.028 1962 0.003 0.020 1963 0.004 0.030 1964 0.005 0.026 1965 0.004 0.038 1966 0.003 0.022 1967 0.007 0.049 1968 0.004 0.048 1969 0.004 0.035 1970 0.004 0.031 1971 0.004 0.037 1972 0.009 0.046 1973 0.004 0.018 1974 0.004 0.038 1975 0.006 0.038 1976 0.004 0.029 1977 0.000 0.027 1978 0.004 0.033 1979 0.002 0.036 1980 0.008 0.062 1981 0.003 0.032 1982 0.006 0.055 1983 0.006 0.033 1984 0.003 0.023 1985 0.002 0.031 1986 0.009 0.030 1987 0.008 0.036 1988 0.003 0.019 1989 0.002 0.028 1990 0.017 0.089 1991 0.010 0.065 1992 0.004 0.025 1993 0.004 0.019 1994 0.001 0.017 1995 0.006 0.028 1996 0.012 0.046 1997 0.010 0.035 1998 0.002 0.030 1999 0.010 0.077 2000 0.004 0.033 2001 0.001 0.029 2002 0.004 0.048 2003 0.006 0.044 2004 0.007 0.070 2005 0.005 0.029 2006 0.006 0.029 2007 0.012 0.082 2008 0.016 0.062 2009 0.008 0.039 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #4 Rank Predeveloped Mitigated 1 0.0167 0.0888 2 0.0160 0.0819 3 0.0124 0.0770 4 0.0122 0.0703 INDIVIDUAL-CB 4/1/2024 12:22:40 PM Page 55 5 0.0115 0.0653 6 0.0102 0.0623 7 0.0100 0.0618 8 0.0096 0.0550 9 0.0090 0.0519 10 0.0085 0.0494 11 0.0081 0.0489 12 0.0080 0.0479 13 0.0078 0.0475 14 0.0077 0.0463 15 0.0073 0.0457 16 0.0072 0.0436 17 0.0071 0.0388 18 0.0064 0.0383 19 0.0062 0.0379 20 0.0062 0.0377 21 0.0058 0.0375 22 0.0057 0.0366 23 0.0057 0.0365 24 0.0056 0.0356 25 0.0056 0.0351 26 0.0052 0.0347 27 0.0052 0.0334 28 0.0051 0.0333 29 0.0049 0.0332 30 0.0046 0.0328 31 0.0045 0.0316 32 0.0044 0.0312 33 0.0044 0.0307 34 0.0044 0.0303 35 0.0044 0.0302 36 0.0043 0.0302 37 0.0042 0.0302 38 0.0041 0.0293 39 0.0040 0.0291 40 0.0040 0.0290 41 0.0039 0.0287 42 0.0039 0.0286 43 0.0038 0.0282 44 0.0037 0.0281 45 0.0036 0.0276 46 0.0036 0.0274 47 0.0036 0.0267 48 0.0035 0.0266 49 0.0034 0.0258 50 0.0034 0.0248 51 0.0032 0.0244 52 0.0031 0.0228 53 0.0029 0.0218 54 0.0027 0.0203 55 0.0023 0.0202 56 0.0022 0.0198 57 0.0021 0.0194 58 0.0020 0.0193 59 0.0014 0.0189 60 0.0007 0.0178 61 0.0005 0.0172 INDIVIDUAL-CB 4/1/2024 12:22:41 PM Page 61 POC 5 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #5 Total Pervious Area:0.209 Total Impervious Area:0 Mitigated Landuse Totals for POC #5 Total Pervious Area:0.001 Total Impervious Area:0.208 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #5 Return Period Flow(cfs) 2 year 0.006145 5 year 0.009651 10 year 0.011637 25 year 0.013742 50 year 0.015045 100 year 0.016153 Flow Frequency Return Periods for Mitigated. POC #5 Return Period Flow(cfs) 2 year 0.082829 5 year 0.104806 10 year 0.119757 25 year 0.139172 50 year 0.154046 100 year 0.169291 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #5 Year Predeveloped Mitigated 1949 0.006 0.107 1950 0.008 0.114 1951 0.014 0.066 1952 0.004 0.057 1953 0.003 0.065 1954 0.005 0.067 1955 0.008 0.078 1956 0.007 0.073 1957 0.005 0.083 1958 0.006 0.069 1959 0.005 0.072 INDIVIDUAL-CB 4/1/2024 12:23:11 PM Page 62 1960 0.009 0.070 1961 0.005 0.070 1962 0.003 0.062 1963 0.004 0.071 1964 0.006 0.070 1965 0.004 0.085 1966 0.004 0.057 1967 0.008 0.100 1968 0.005 0.120 1969 0.005 0.078 1970 0.004 0.077 1971 0.004 0.092 1972 0.010 0.092 1973 0.005 0.059 1974 0.005 0.085 1975 0.007 0.095 1976 0.005 0.067 1977 0.001 0.070 1978 0.004 0.092 1979 0.003 0.120 1980 0.010 0.111 1981 0.004 0.085 1982 0.007 0.120 1983 0.007 0.098 1984 0.004 0.061 1985 0.002 0.083 1986 0.011 0.073 1987 0.009 0.113 1988 0.004 0.069 1989 0.002 0.096 1990 0.020 0.143 1991 0.012 0.118 1992 0.005 0.061 1993 0.005 0.060 1994 0.002 0.060 1995 0.007 0.076 1996 0.014 0.086 1997 0.012 0.078 1998 0.003 0.080 1999 0.011 0.166 2000 0.005 0.080 2001 0.001 0.092 2002 0.005 0.101 2003 0.007 0.088 2004 0.009 0.157 2005 0.006 0.068 2006 0.007 0.061 2007 0.015 0.147 2008 0.019 0.114 2009 0.009 0.110 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #5 Rank Predeveloped Mitigated 1 0.0197 0.1658 2 0.0189 0.1571 3 0.0146 0.1472 4 0.0144 0.1432 INDIVIDUAL-CB 4/1/2024 12:23:11 PM Page 63 5 0.0135 0.1200 6 0.0120 0.1199 7 0.0119 0.1197 8 0.0113 0.1181 9 0.0107 0.1143 10 0.0101 0.1137 11 0.0095 0.1132 12 0.0094 0.1105 13 0.0093 0.1095 14 0.0091 0.1071 15 0.0086 0.1010 16 0.0084 0.0998 17 0.0084 0.0981 18 0.0075 0.0961 19 0.0073 0.0953 20 0.0073 0.0924 21 0.0068 0.0923 22 0.0067 0.0919 23 0.0067 0.0917 24 0.0066 0.0876 25 0.0066 0.0857 26 0.0062 0.0854 27 0.0061 0.0850 28 0.0060 0.0846 29 0.0058 0.0832 30 0.0054 0.0832 31 0.0053 0.0805 32 0.0052 0.0798 33 0.0052 0.0780 34 0.0052 0.0777 35 0.0052 0.0775 36 0.0051 0.0770 37 0.0050 0.0755 38 0.0049 0.0730 39 0.0048 0.0729 40 0.0048 0.0720 41 0.0046 0.0712 42 0.0046 0.0703 43 0.0045 0.0702 44 0.0044 0.0700 45 0.0043 0.0697 46 0.0043 0.0690 47 0.0042 0.0687 48 0.0042 0.0678 49 0.0041 0.0670 50 0.0040 0.0666 51 0.0038 0.0658 52 0.0037 0.0648 53 0.0034 0.0625 54 0.0032 0.0613 55 0.0027 0.0605 56 0.0026 0.0605 57 0.0024 0.0602 58 0.0024 0.0602 59 0.0016 0.0586 60 0.0009 0.0571 61 0.0006 0.0569 INDIVIDUAL-CB 4/1/2024 12:23:11 PM Page 69 POC 6 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #6 Total Pervious Area:0.33 Total Impervious Area:0 Mitigated Landuse Totals for POC #6 Total Pervious Area:0.025 Total Impervious Area:0.008 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #6 Return Period Flow(cfs) 2 year 0.009702 5 year 0.015238 10 year 0.018375 25 year 0.021698 50 year 0.023755 100 year 0.025504 Flow Frequency Return Periods for Mitigated. POC #6 Return Period Flow(cfs) 2 year 0.00518 5 year 0.007637 10 year 0.009475 25 year 0.012045 50 year 0.014142 100 year 0.0164 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #6 Year Predeveloped Mitigated 1949 0.010 0.009 1950 0.012 0.008 1951 0.021 0.005 1952 0.007 0.003 1953 0.005 0.003 1954 0.008 0.004 1955 0.013 0.004 1956 0.011 0.004 1957 0.009 0.006 1958 0.010 0.004 1959 0.008 0.003 INDIVIDUAL-CB 4/1/2024 12:23:41 PM Page 70 1960 0.014 0.005 1961 0.008 0.005 1962 0.005 0.003 1963 0.007 0.005 1964 0.009 0.004 1965 0.007 0.006 1966 0.006 0.003 1967 0.013 0.008 1968 0.008 0.007 1969 0.008 0.006 1970 0.007 0.005 1971 0.007 0.006 1972 0.016 0.008 1973 0.007 0.003 1974 0.008 0.006 1975 0.011 0.006 1976 0.008 0.004 1977 0.001 0.004 1978 0.007 0.005 1979 0.004 0.005 1980 0.015 0.010 1981 0.006 0.005 1982 0.012 0.009 1983 0.010 0.005 1984 0.006 0.004 1985 0.004 0.005 1986 0.017 0.005 1987 0.015 0.005 1988 0.006 0.003 1989 0.004 0.003 1990 0.031 0.016 1991 0.019 0.011 1992 0.007 0.004 1993 0.008 0.003 1994 0.003 0.002 1995 0.011 0.004 1996 0.023 0.008 1997 0.019 0.006 1998 0.004 0.005 1999 0.018 0.012 2000 0.008 0.005 2001 0.001 0.004 2002 0.008 0.008 2003 0.010 0.007 2004 0.014 0.011 2005 0.010 0.005 2006 0.011 0.005 2007 0.023 0.014 2008 0.030 0.011 2009 0.015 0.006 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #6 Rank Predeveloped Mitigated 1 0.0311 0.0158 2 0.0298 0.0145 3 0.0231 0.0125 4 0.0227 0.0111 INDIVIDUAL-CB 4/1/2024 12:23:41 PM Page 71 5 0.0214 0.0111 6 0.0190 0.0107 7 0.0187 0.0099 8 0.0178 0.0094 9 0.0168 0.0086 10 0.0159 0.0085 11 0.0151 0.0084 12 0.0149 0.0081 13 0.0146 0.0079 14 0.0144 0.0075 15 0.0136 0.0071 16 0.0133 0.0068 17 0.0132 0.0064 18 0.0119 0.0064 19 0.0116 0.0063 20 0.0115 0.0060 21 0.0108 0.0060 22 0.0106 0.0058 23 0.0106 0.0058 24 0.0105 0.0057 25 0.0104 0.0053 26 0.0097 0.0053 27 0.0096 0.0052 28 0.0095 0.0050 29 0.0092 0.0050 30 0.0086 0.0050 31 0.0084 0.0049 32 0.0083 0.0049 33 0.0082 0.0049 34 0.0082 0.0049 35 0.0082 0.0049 36 0.0081 0.0048 37 0.0078 0.0047 38 0.0077 0.0047 39 0.0075 0.0046 40 0.0075 0.0046 41 0.0072 0.0045 42 0.0072 0.0043 43 0.0071 0.0043 44 0.0070 0.0042 45 0.0067 0.0042 46 0.0067 0.0040 47 0.0066 0.0039 48 0.0066 0.0039 49 0.0064 0.0038 50 0.0063 0.0036 51 0.0060 0.0036 52 0.0059 0.0032 53 0.0054 0.0032 54 0.0051 0.0030 55 0.0043 0.0030 56 0.0041 0.0029 57 0.0038 0.0027 58 0.0038 0.0027 59 0.0025 0.0026 60 0.0013 0.0026 61 0.0009 0.0022 INDIVIDUAL-CB 4/1/2024 12:23:41 PM Page 77 POC 7 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #7 Total Pervious Area:0.042 Total Impervious Area:0 Mitigated Landuse Totals for POC #7 Total Pervious Area:0.024 Total Impervious Area:0.018 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #7 Return Period Flow(cfs) 2 year 0.001235 5 year 0.001939 10 year 0.002339 25 year 0.002762 50 year 0.003023 100 year 0.003246 Flow Frequency Return Periods for Mitigated. POC #7 Return Period Flow(cfs) 2 year 0.008919 5 year 0.012193 10 year 0.014557 25 year 0.017774 50 year 0.020342 100 year 0.02306 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #7 Year Predeveloped Mitigated 1949 0.001 0.013 1950 0.002 0.012 1951 0.003 0.008 1952 0.001 0.005 1953 0.001 0.006 1954 0.001 0.007 1955 0.002 0.008 1956 0.001 0.008 1957 0.001 0.010 1958 0.001 0.007 1959 0.001 0.006 INDIVIDUAL-CB 4/1/2024 12:24:12 PM Page 78 1960 0.002 0.008 1961 0.001 0.008 1962 0.001 0.006 1963 0.001 0.008 1964 0.001 0.007 1965 0.001 0.010 1966 0.001 0.006 1967 0.002 0.012 1968 0.001 0.013 1969 0.001 0.009 1970 0.001 0.008 1971 0.001 0.010 1972 0.002 0.012 1973 0.001 0.005 1974 0.001 0.010 1975 0.001 0.010 1976 0.001 0.008 1977 0.000 0.007 1978 0.001 0.009 1979 0.001 0.011 1980 0.002 0.015 1981 0.001 0.009 1982 0.001 0.015 1983 0.001 0.009 1984 0.001 0.006 1985 0.000 0.009 1986 0.002 0.008 1987 0.002 0.011 1988 0.001 0.006 1989 0.000 0.008 1990 0.004 0.022 1991 0.002 0.016 1992 0.001 0.006 1993 0.001 0.005 1994 0.000 0.005 1995 0.001 0.008 1996 0.003 0.011 1997 0.002 0.009 1998 0.001 0.008 1999 0.002 0.020 2000 0.001 0.009 2001 0.000 0.008 2002 0.001 0.013 2003 0.001 0.011 2004 0.002 0.018 2005 0.001 0.008 2006 0.001 0.008 2007 0.003 0.020 2008 0.004 0.016 2009 0.002 0.010 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #7 Rank Predeveloped Mitigated 1 0.0040 0.0222 2 0.0038 0.0202 3 0.0029 0.0200 4 0.0029 0.0183 INDIVIDUAL-CB 4/1/2024 12:24:12 PM Page 79 5 0.0027 0.0164 6 0.0024 0.0159 7 0.0024 0.0147 8 0.0023 0.0145 9 0.0021 0.0135 10 0.0020 0.0127 11 0.0019 0.0126 12 0.0019 0.0125 13 0.0019 0.0123 14 0.0018 0.0122 15 0.0017 0.0109 16 0.0017 0.0107 17 0.0017 0.0106 18 0.0015 0.0106 19 0.0015 0.0103 20 0.0015 0.0101 21 0.0014 0.0101 22 0.0014 0.0100 23 0.0014 0.0099 24 0.0013 0.0099 25 0.0013 0.0094 26 0.0012 0.0094 27 0.0012 0.0093 28 0.0012 0.0091 29 0.0012 0.0089 30 0.0011 0.0089 31 0.0011 0.0085 32 0.0011 0.0085 33 0.0010 0.0084 34 0.0010 0.0083 35 0.0010 0.0081 36 0.0010 0.0080 37 0.0010 0.0080 38 0.0010 0.0080 39 0.0010 0.0079 40 0.0010 0.0079 41 0.0009 0.0078 42 0.0009 0.0077 43 0.0009 0.0077 44 0.0009 0.0076 45 0.0009 0.0075 46 0.0009 0.0075 47 0.0008 0.0073 48 0.0008 0.0070 49 0.0008 0.0069 50 0.0008 0.0069 51 0.0008 0.0065 52 0.0007 0.0065 53 0.0007 0.0060 54 0.0006 0.0059 55 0.0005 0.0059 56 0.0005 0.0059 57 0.0005 0.0058 58 0.0005 0.0054 59 0.0003 0.0051 60 0.0002 0.0051 61 0.0001 0.0050 INDIVIDUAL-CB 4/1/2024 12:24:12 PM Page 85 POC 8 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #8 Total Pervious Area:0.085 Total Impervious Area:0 Mitigated Landuse Totals for POC #8 Total Pervious Area:0.021 Total Impervious Area:0.064 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #8 Return Period Flow(cfs) 2 year 0.002499 5 year 0.003925 10 year 0.004733 25 year 0.005589 50 year 0.006119 100 year 0.006569 Flow Frequency Return Periods for Mitigated. POC #8 Return Period Flow(cfs) 2 year 0.028928 5 year 0.037322 10 year 0.043237 25 year 0.051137 50 year 0.057341 100 year 0.063826 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #8 Year Predeveloped Mitigated 1949 0.002 0.039 1950 0.003 0.037 1951 0.006 0.023 1952 0.002 0.018 1953 0.001 0.022 1954 0.002 0.023 1955 0.003 0.028 1956 0.003 0.024 1957 0.002 0.029 1958 0.002 0.023 1959 0.002 0.025 INDIVIDUAL-CB 4/1/2024 12:24:42 PM Page 86 1960 0.004 0.026 1961 0.002 0.024 1962 0.001 0.021 1963 0.002 0.026 1964 0.002 0.024 1965 0.002 0.029 1966 0.002 0.020 1967 0.003 0.035 1968 0.002 0.044 1969 0.002 0.027 1970 0.002 0.027 1971 0.002 0.033 1972 0.004 0.033 1973 0.002 0.020 1974 0.002 0.031 1975 0.003 0.031 1976 0.002 0.024 1977 0.000 0.024 1978 0.002 0.033 1979 0.001 0.041 1980 0.004 0.046 1981 0.002 0.028 1982 0.003 0.042 1983 0.003 0.033 1984 0.002 0.021 1985 0.001 0.027 1986 0.004 0.024 1987 0.004 0.037 1988 0.002 0.023 1989 0.001 0.036 1990 0.008 0.053 1991 0.005 0.044 1992 0.002 0.021 1993 0.002 0.024 1994 0.001 0.022 1995 0.003 0.025 1996 0.006 0.033 1997 0.005 0.027 1998 0.001 0.027 1999 0.005 0.060 2000 0.002 0.028 2001 0.000 0.032 2002 0.002 0.035 2003 0.003 0.035 2004 0.003 0.058 2005 0.003 0.023 2006 0.003 0.022 2007 0.006 0.055 2008 0.008 0.042 2009 0.004 0.039 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #8 Rank Predeveloped Mitigated 1 0.0080 0.0605 2 0.0077 0.0578 3 0.0059 0.0547 4 0.0059 0.0534 INDIVIDUAL-CB 4/1/2024 12:24:42 PM Page 87 5 0.0055 0.0458 6 0.0049 0.0445 7 0.0048 0.0441 8 0.0046 0.0417 9 0.0043 0.0415 10 0.0041 0.0410 11 0.0039 0.0390 12 0.0038 0.0385 13 0.0038 0.0375 14 0.0037 0.0369 15 0.0035 0.0359 16 0.0034 0.0350 17 0.0034 0.0349 18 0.0031 0.0349 19 0.0030 0.0333 20 0.0030 0.0332 21 0.0028 0.0331 22 0.0027 0.0327 23 0.0027 0.0326 24 0.0027 0.0321 25 0.0027 0.0309 26 0.0025 0.0307 27 0.0025 0.0295 28 0.0025 0.0287 29 0.0024 0.0283 30 0.0022 0.0277 31 0.0022 0.0275 32 0.0021 0.0273 33 0.0021 0.0270 34 0.0021 0.0270 35 0.0021 0.0269 36 0.0021 0.0268 37 0.0020 0.0259 38 0.0020 0.0255 39 0.0019 0.0255 40 0.0019 0.0246 41 0.0019 0.0244 42 0.0019 0.0244 43 0.0018 0.0244 44 0.0018 0.0242 45 0.0017 0.0240 46 0.0017 0.0240 47 0.0017 0.0239 48 0.0017 0.0235 49 0.0017 0.0233 50 0.0016 0.0232 51 0.0016 0.0230 52 0.0015 0.0226 53 0.0014 0.0219 54 0.0013 0.0217 55 0.0011 0.0217 56 0.0010 0.0215 57 0.0010 0.0209 58 0.0010 0.0206 59 0.0007 0.0204 60 0.0003 0.0199 61 0.0002 0.0180 INDIVIDUAL-CB 4/1/2024 12:24:42 PM Page 93 POC 9 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #9 Total Pervious Area:0.096 Total Impervious Area:0 Mitigated Landuse Totals for POC #9 Total Pervious Area:0.044 Total Impervious Area:0.052 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #9 Return Period Flow(cfs) 2 year 0.002822 5 year 0.004433 10 year 0.005345 25 year 0.006312 50 year 0.006911 100 year 0.007419 Flow Frequency Return Periods for Mitigated. POC #9 Return Period Flow(cfs) 2 year 0.025912 5 year 0.034151 10 year 0.040054 25 year 0.048043 50 year 0.05439 100 year 0.061087 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #9 Year Predeveloped Mitigated 1949 0.003 0.037 1950 0.003 0.033 1951 0.006 0.022 1952 0.002 0.016 1953 0.002 0.018 1954 0.002 0.021 1955 0.004 0.024 1956 0.003 0.021 1957 0.002 0.027 1958 0.003 0.020 1959 0.002 0.020 INDIVIDUAL-CB 4/1/2024 12:25:14 PM Page 94 1960 0.004 0.024 1961 0.002 0.022 1962 0.001 0.018 1963 0.002 0.023 1964 0.003 0.020 1965 0.002 0.027 1966 0.002 0.018 1967 0.004 0.034 1968 0.002 0.039 1969 0.002 0.025 1970 0.002 0.024 1971 0.002 0.029 1972 0.005 0.031 1973 0.002 0.016 1974 0.002 0.028 1975 0.003 0.027 1976 0.002 0.022 1977 0.000 0.022 1978 0.002 0.028 1979 0.001 0.034 1980 0.004 0.045 1981 0.002 0.025 1982 0.003 0.038 1983 0.003 0.028 1984 0.002 0.019 1985 0.001 0.024 1986 0.005 0.022 1987 0.004 0.031 1988 0.002 0.019 1989 0.001 0.030 1990 0.009 0.055 1991 0.005 0.044 1992 0.002 0.020 1993 0.002 0.021 1994 0.001 0.018 1995 0.003 0.022 1996 0.007 0.032 1997 0.006 0.025 1998 0.001 0.024 1999 0.005 0.056 2000 0.002 0.025 2001 0.000 0.027 2002 0.002 0.033 2003 0.003 0.033 2004 0.004 0.053 2005 0.003 0.021 2006 0.003 0.020 2007 0.007 0.051 2008 0.009 0.041 2009 0.004 0.032 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #9 Rank Predeveloped Mitigated 1 0.0090 0.0565 2 0.0087 0.0546 3 0.0067 0.0533 4 0.0066 0.0510 INDIVIDUAL-CB 4/1/2024 12:25:14 PM Page 95 5 0.0062 0.0446 6 0.0055 0.0437 7 0.0054 0.0409 8 0.0052 0.0395 9 0.0049 0.0380 10 0.0046 0.0369 11 0.0044 0.0344 12 0.0043 0.0339 13 0.0043 0.0330 14 0.0042 0.0328 15 0.0040 0.0325 16 0.0039 0.0320 17 0.0038 0.0316 18 0.0035 0.0312 19 0.0034 0.0311 20 0.0033 0.0298 21 0.0031 0.0294 22 0.0031 0.0285 23 0.0031 0.0279 24 0.0031 0.0278 25 0.0030 0.0274 26 0.0028 0.0271 27 0.0028 0.0270 28 0.0028 0.0266 29 0.0027 0.0251 30 0.0025 0.0251 31 0.0024 0.0250 32 0.0024 0.0250 33 0.0024 0.0243 34 0.0024 0.0242 35 0.0024 0.0242 36 0.0023 0.0242 37 0.0023 0.0241 38 0.0022 0.0233 39 0.0022 0.0223 40 0.0022 0.0223 41 0.0021 0.0222 42 0.0021 0.0219 43 0.0021 0.0217 44 0.0020 0.0215 45 0.0020 0.0212 46 0.0020 0.0211 47 0.0019 0.0209 48 0.0019 0.0207 49 0.0019 0.0204 50 0.0018 0.0204 51 0.0018 0.0203 52 0.0017 0.0201 53 0.0016 0.0196 54 0.0015 0.0189 55 0.0013 0.0185 56 0.0012 0.0183 57 0.0011 0.0181 58 0.0011 0.0181 59 0.0007 0.0175 60 0.0004 0.0164 61 0.0003 0.0158 INDIVIDUAL-CB 4/1/2024 12:25:14 PM Page 101 POC 10 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #10 Total Pervious Area:0.095 Total Impervious Area:0 Mitigated Landuse Totals for POC #10 Total Pervious Area:0.015 Total Impervious Area:0.08 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #10 Return Period Flow(cfs) 2 year 0.002793 5 year 0.004387 10 year 0.00529 25 year 0.006246 50 year 0.006839 100 year 0.007342 Flow Frequency Return Periods for Mitigated. POC #10 Return Period Flow(cfs) 2 year 0.03458 5 year 0.044335 10 year 0.051178 25 year 0.06028 50 year 0.067403 100 year 0.07483 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #10 Year Predeveloped Mitigated 1949 0.003 0.046 1950 0.003 0.046 1951 0.006 0.028 1952 0.002 0.022 1953 0.002 0.027 1954 0.002 0.028 1955 0.004 0.033 1956 0.003 0.029 1957 0.002 0.034 1958 0.003 0.028 1959 0.002 0.030 INDIVIDUAL-CB 4/1/2024 12:25:45 PM Page 102 1960 0.004 0.030 1961 0.002 0.029 1962 0.001 0.025 1963 0.002 0.030 1964 0.003 0.029 1965 0.002 0.035 1966 0.002 0.024 1967 0.004 0.041 1968 0.002 0.052 1969 0.002 0.032 1970 0.002 0.032 1971 0.002 0.039 1972 0.005 0.039 1973 0.002 0.024 1974 0.002 0.036 1975 0.003 0.038 1976 0.002 0.029 1977 0.000 0.028 1978 0.002 0.040 1979 0.001 0.050 1980 0.004 0.052 1981 0.002 0.034 1982 0.003 0.050 1983 0.003 0.040 1984 0.002 0.025 1985 0.001 0.033 1986 0.005 0.029 1987 0.004 0.045 1988 0.002 0.027 1989 0.001 0.043 1990 0.009 0.062 1991 0.005 0.052 1992 0.002 0.025 1993 0.002 0.028 1994 0.001 0.026 1995 0.003 0.031 1996 0.007 0.039 1997 0.005 0.032 1998 0.001 0.033 1999 0.005 0.071 2000 0.002 0.033 2001 0.000 0.039 2002 0.002 0.041 2003 0.003 0.040 2004 0.004 0.068 2005 0.003 0.028 2006 0.003 0.026 2007 0.007 0.064 2008 0.009 0.049 2009 0.004 0.047 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #10 Rank Predeveloped Mitigated 1 0.0090 0.0713 2 0.0086 0.0681 3 0.0066 0.0642 4 0.0065 0.0618 INDIVIDUAL-CB 4/1/2024 12:25:45 PM Page 103 5 0.0062 0.0523 6 0.0055 0.0522 7 0.0054 0.0517 8 0.0051 0.0498 9 0.0048 0.0497 10 0.0046 0.0487 11 0.0043 0.0465 12 0.0043 0.0459 13 0.0042 0.0459 14 0.0042 0.0453 15 0.0039 0.0427 16 0.0038 0.0415 17 0.0038 0.0410 18 0.0034 0.0403 19 0.0033 0.0398 20 0.0033 0.0397 21 0.0031 0.0390 22 0.0031 0.0388 23 0.0031 0.0387 24 0.0030 0.0387 25 0.0030 0.0379 26 0.0028 0.0365 27 0.0028 0.0352 28 0.0027 0.0344 29 0.0026 0.0343 30 0.0025 0.0333 31 0.0024 0.0332 32 0.0024 0.0329 33 0.0024 0.0326 34 0.0024 0.0322 35 0.0023 0.0322 36 0.0023 0.0322 37 0.0023 0.0308 38 0.0022 0.0304 39 0.0022 0.0303 40 0.0022 0.0299 41 0.0021 0.0293 42 0.0021 0.0292 43 0.0020 0.0291 44 0.0020 0.0291 45 0.0019 0.0289 46 0.0019 0.0285 47 0.0019 0.0284 48 0.0019 0.0283 49 0.0018 0.0279 50 0.0018 0.0276 51 0.0017 0.0276 52 0.0017 0.0274 53 0.0016 0.0266 54 0.0015 0.0260 55 0.0012 0.0258 56 0.0012 0.0253 57 0.0011 0.0252 58 0.0011 0.0249 59 0.0007 0.0243 60 0.0004 0.0242 61 0.0003 0.0221 INDIVIDUAL-CB 4/1/2024 12:25:45 PM Page 109 POC 11 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #11 Total Pervious Area:0.094 Total Impervious Area:0 Mitigated Landuse Totals for POC #11 Total Pervious Area:0.016 Total Impervious Area:0.078 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #11 Return Period Flow(cfs) 2 year 0.002764 5 year 0.00434 10 year 0.005234 25 year 0.006181 50 year 0.006767 100 year 0.007265 Flow Frequency Return Periods for Mitigated. POC #11 Return Period Flow(cfs) 2 year 0.033777 5 year 0.043338 10 year 0.050048 25 year 0.058979 50 year 0.065971 100 year 0.073262 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #11 Year Predeveloped Mitigated 1949 0.003 0.045 1950 0.003 0.045 1951 0.006 0.027 1952 0.002 0.022 1953 0.002 0.026 1954 0.002 0.027 1955 0.004 0.032 1956 0.003 0.029 1957 0.002 0.034 1958 0.003 0.028 1959 0.002 0.029 INDIVIDUAL-CB 4/1/2024 12:26:17 PM Page 110 1960 0.004 0.030 1961 0.002 0.028 1962 0.001 0.025 1963 0.002 0.030 1964 0.003 0.028 1965 0.002 0.034 1966 0.002 0.024 1967 0.004 0.040 1968 0.002 0.051 1969 0.002 0.032 1970 0.002 0.031 1971 0.002 0.038 1972 0.005 0.038 1973 0.002 0.024 1974 0.002 0.036 1975 0.003 0.037 1976 0.002 0.028 1977 0.000 0.028 1978 0.002 0.039 1979 0.001 0.049 1980 0.004 0.051 1981 0.002 0.034 1982 0.003 0.049 1983 0.003 0.039 1984 0.002 0.024 1985 0.001 0.033 1986 0.005 0.028 1987 0.004 0.044 1988 0.002 0.027 1989 0.001 0.042 1990 0.009 0.061 1991 0.005 0.051 1992 0.002 0.025 1993 0.002 0.028 1994 0.001 0.025 1995 0.003 0.030 1996 0.006 0.038 1997 0.005 0.032 1998 0.001 0.032 1999 0.005 0.070 2000 0.002 0.033 2001 0.000 0.038 2002 0.002 0.041 2003 0.003 0.039 2004 0.004 0.067 2005 0.003 0.027 2006 0.003 0.025 2007 0.007 0.063 2008 0.008 0.048 2009 0.004 0.045 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #11 Rank Predeveloped Mitigated 1 0.0089 0.0698 2 0.0085 0.0666 3 0.0066 0.0628 4 0.0065 0.0608 INDIVIDUAL-CB 4/1/2024 12:26:17 PM Page 111 5 0.0061 0.0512 6 0.0054 0.0509 7 0.0053 0.0507 8 0.0051 0.0486 9 0.0048 0.0485 10 0.0045 0.0478 11 0.0043 0.0453 12 0.0042 0.0449 13 0.0042 0.0448 14 0.0041 0.0442 15 0.0039 0.0415 16 0.0038 0.0407 17 0.0038 0.0401 18 0.0034 0.0394 19 0.0033 0.0388 20 0.0033 0.0387 21 0.0031 0.0381 22 0.0030 0.0379 23 0.0030 0.0378 24 0.0030 0.0377 25 0.0030 0.0370 26 0.0028 0.0357 27 0.0027 0.0345 28 0.0027 0.0337 29 0.0026 0.0335 30 0.0024 0.0325 31 0.0024 0.0325 32 0.0024 0.0321 33 0.0023 0.0318 34 0.0023 0.0316 35 0.0023 0.0315 36 0.0023 0.0315 37 0.0022 0.0301 38 0.0022 0.0297 39 0.0021 0.0296 40 0.0021 0.0291 41 0.0021 0.0287 42 0.0021 0.0284 43 0.0020 0.0284 44 0.0020 0.0284 45 0.0019 0.0282 46 0.0019 0.0277 47 0.0019 0.0276 48 0.0019 0.0276 49 0.0018 0.0273 50 0.0018 0.0271 51 0.0017 0.0270 52 0.0017 0.0267 53 0.0016 0.0259 54 0.0014 0.0253 55 0.0012 0.0252 56 0.0012 0.0247 57 0.0011 0.0246 58 0.0011 0.0243 59 0.0007 0.0237 60 0.0004 0.0236 61 0.0003 0.0216 INDIVIDUAL-CB 4/1/2024 12:26:17 PM Page 117 POC 12 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #12 Total Pervious Area:0.024 Total Impervious Area:0 Mitigated Landuse Totals for POC #12 Total Pervious Area:0.002 Total Impervious Area:0.022 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #12 Return Period Flow(cfs) 2 year 0.000706 5 year 0.001108 10 year 0.001336 25 year 0.001578 50 year 0.001728 100 year 0.001855 Flow Frequency Return Periods for Mitigated. POC #12 Return Period Flow(cfs) 2 year 0.009797 5 year 0.012512 10 year 0.01441 25 year 0.01693 50 year 0.018898 100 year 0.020945 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #12 Year Predeveloped Mitigated 1949 0.001 0.013 1950 0.001 0.013 1951 0.002 0.008 1952 0.000 0.006 1953 0.000 0.008 1954 0.001 0.008 1955 0.001 0.009 1956 0.001 0.009 1957 0.001 0.009 1958 0.001 0.008 1959 0.001 0.009 INDIVIDUAL-CB 4/1/2024 12:26:49 PM Page 118 1960 0.001 0.009 1961 0.001 0.008 1962 0.000 0.007 1963 0.001 0.009 1964 0.001 0.008 1965 0.000 0.010 1966 0.000 0.007 1967 0.001 0.011 1968 0.001 0.015 1969 0.001 0.009 1970 0.000 0.009 1971 0.001 0.011 1972 0.001 0.011 1973 0.001 0.007 1974 0.001 0.010 1975 0.001 0.011 1976 0.001 0.008 1977 0.000 0.008 1978 0.000 0.012 1979 0.000 0.014 1980 0.001 0.015 1981 0.000 0.009 1982 0.001 0.014 1983 0.001 0.011 1984 0.000 0.007 1985 0.000 0.009 1986 0.001 0.008 1987 0.001 0.013 1988 0.000 0.008 1989 0.000 0.013 1990 0.002 0.016 1991 0.001 0.014 1992 0.001 0.007 1993 0.001 0.009 1994 0.000 0.008 1995 0.001 0.009 1996 0.002 0.011 1997 0.001 0.009 1998 0.000 0.009 1999 0.001 0.020 2000 0.001 0.009 2001 0.000 0.011 2002 0.001 0.012 2003 0.001 0.012 2004 0.001 0.019 2005 0.001 0.007 2006 0.001 0.007 2007 0.002 0.018 2008 0.002 0.013 2009 0.001 0.014 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #12 Rank Predeveloped Mitigated 1 0.0023 0.0199 2 0.0022 0.0193 3 0.0017 0.0181 4 0.0017 0.0163 INDIVIDUAL-CB 4/1/2024 12:26:49 PM Page 119 5 0.0016 0.0152 6 0.0014 0.0151 7 0.0014 0.0144 8 0.0013 0.0142 9 0.0012 0.0137 10 0.0012 0.0136 11 0.0011 0.0131 12 0.0011 0.0130 13 0.0011 0.0129 14 0.0011 0.0127 15 0.0010 0.0126 16 0.0010 0.0119 17 0.0010 0.0117 18 0.0009 0.0117 19 0.0008 0.0114 20 0.0008 0.0112 21 0.0008 0.0111 22 0.0008 0.0111 23 0.0008 0.0110 24 0.0008 0.0110 25 0.0008 0.0107 26 0.0007 0.0102 27 0.0007 0.0097 28 0.0007 0.0095 29 0.0007 0.0094 30 0.0006 0.0094 31 0.0006 0.0092 32 0.0006 0.0092 33 0.0006 0.0092 34 0.0006 0.0090 35 0.0006 0.0089 36 0.0006 0.0089 37 0.0006 0.0088 38 0.0006 0.0087 39 0.0005 0.0087 40 0.0005 0.0086 41 0.0005 0.0085 42 0.0005 0.0085 43 0.0005 0.0084 44 0.0005 0.0083 45 0.0005 0.0082 46 0.0005 0.0082 47 0.0005 0.0081 48 0.0005 0.0081 49 0.0005 0.0080 50 0.0005 0.0079 51 0.0004 0.0079 52 0.0004 0.0076 53 0.0004 0.0075 54 0.0004 0.0074 55 0.0003 0.0073 56 0.0003 0.0072 57 0.0003 0.0071 58 0.0003 0.0070 59 0.0002 0.0070 60 0.0001 0.0070 61 0.0001 0.0063 INDIVIDUAL-CB 4/1/2024 12:26:49 PM Page 125 POC 13 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #13 Total Pervious Area:0.121 Total Impervious Area:0 Mitigated Landuse Totals for POC #13 Total Pervious Area:0.062 Total Impervious Area:0.059 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #13 Return Period Flow(cfs) 2 year 0.003558 5 year 0.005587 10 year 0.006737 25 year 0.007956 50 year 0.00871 100 year 0.009352 Flow Frequency Return Periods for Mitigated. POC #13 Return Period Flow(cfs) 2 year 0.028813 5 year 0.038588 10 year 0.045535 25 year 0.054871 50 year 0.062242 100 year 0.069978 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #13 Year Predeveloped Mitigated 1949 0.003 0.042 1950 0.004 0.038 1951 0.008 0.025 1952 0.002 0.017 1953 0.002 0.020 1954 0.003 0.023 1955 0.005 0.026 1956 0.004 0.024 1957 0.003 0.031 1958 0.004 0.023 1959 0.003 0.021 INDIVIDUAL-CB 4/1/2024 12:27:19 PM Page 126 1960 0.005 0.027 1961 0.003 0.025 1962 0.002 0.019 1963 0.003 0.026 1964 0.003 0.022 1965 0.002 0.032 1966 0.002 0.019 1967 0.005 0.038 1968 0.003 0.042 1969 0.003 0.029 1970 0.002 0.027 1971 0.003 0.033 1972 0.006 0.037 1973 0.003 0.017 1974 0.003 0.032 1975 0.004 0.032 1976 0.003 0.024 1977 0.000 0.023 1978 0.002 0.029 1979 0.001 0.036 1980 0.006 0.048 1981 0.002 0.029 1982 0.004 0.045 1983 0.004 0.031 1984 0.002 0.021 1985 0.001 0.028 1986 0.006 0.025 1987 0.005 0.035 1988 0.002 0.020 1989 0.001 0.029 1990 0.011 0.066 1991 0.007 0.051 1992 0.003 0.021 1993 0.003 0.019 1994 0.001 0.018 1995 0.004 0.025 1996 0.008 0.035 1997 0.007 0.029 1998 0.002 0.026 1999 0.007 0.064 2000 0.003 0.029 2001 0.000 0.028 2002 0.003 0.039 2003 0.004 0.035 2004 0.005 0.059 2005 0.004 0.025 2006 0.004 0.024 2007 0.008 0.061 2008 0.011 0.048 2009 0.005 0.032 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #13 Rank Predeveloped Mitigated 1 0.0114 0.0663 2 0.0109 0.0636 3 0.0085 0.0606 4 0.0083 0.0590 INDIVIDUAL-CB 4/1/2024 12:27:19 PM Page 127 5 0.0078 0.0507 6 0.0070 0.0485 7 0.0069 0.0479 8 0.0065 0.0446 9 0.0062 0.0422 10 0.0058 0.0420 11 0.0055 0.0390 12 0.0055 0.0382 13 0.0054 0.0382 14 0.0053 0.0371 15 0.0050 0.0362 16 0.0049 0.0352 17 0.0048 0.0348 18 0.0044 0.0347 19 0.0042 0.0327 20 0.0042 0.0323 21 0.0040 0.0321 22 0.0039 0.0317 23 0.0039 0.0315 24 0.0038 0.0309 25 0.0038 0.0309 26 0.0036 0.0293 27 0.0035 0.0291 28 0.0035 0.0288 29 0.0034 0.0288 30 0.0031 0.0285 31 0.0031 0.0285 32 0.0030 0.0284 33 0.0030 0.0281 34 0.0030 0.0270 35 0.0030 0.0270 36 0.0030 0.0263 37 0.0029 0.0258 38 0.0028 0.0255 39 0.0028 0.0254 40 0.0028 0.0252 41 0.0026 0.0251 42 0.0026 0.0249 43 0.0026 0.0246 44 0.0026 0.0244 45 0.0025 0.0244 46 0.0025 0.0236 47 0.0024 0.0234 48 0.0024 0.0232 49 0.0024 0.0225 50 0.0023 0.0220 51 0.0022 0.0211 52 0.0022 0.0210 53 0.0020 0.0205 54 0.0019 0.0198 55 0.0016 0.0196 56 0.0015 0.0195 57 0.0014 0.0195 58 0.0014 0.0188 59 0.0009 0.0175 60 0.0005 0.0174 61 0.0003 0.0170 INDIVIDUAL-CB 4/1/2024 12:27:19 PM Page 133 POC 14 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #14 Total Pervious Area:0.164 Total Impervious Area:0 Mitigated Landuse Totals for POC #14 Total Pervious Area:0.062 Total Impervious Area:0.102 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #14 Return Period Flow(cfs) 2 year 0.004822 5 year 0.007573 10 year 0.009132 25 year 0.010783 50 year 0.011805 100 year 0.012675 Flow Frequency Return Periods for Mitigated. POC #14 Return Period Flow(cfs) 2 year 0.043696 5 year 0.057195 10 year 0.066622 25 year 0.079116 50 year 0.088862 100 year 0.098993 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #14 Year Predeveloped Mitigated 1949 0.005 0.062 1950 0.006 0.056 1951 0.011 0.038 1952 0.003 0.029 1953 0.003 0.031 1954 0.004 0.036 1955 0.007 0.040 1956 0.005 0.039 1957 0.004 0.047 1958 0.005 0.035 1959 0.004 0.033 INDIVIDUAL-CB 4/1/2024 12:27:50 PM Page 134 1960 0.007 0.039 1961 0.004 0.039 1962 0.003 0.031 1963 0.003 0.038 1964 0.005 0.035 1965 0.003 0.049 1966 0.003 0.030 1967 0.007 0.055 1968 0.004 0.061 1969 0.004 0.044 1970 0.003 0.041 1971 0.004 0.049 1972 0.008 0.056 1973 0.004 0.027 1974 0.004 0.047 1975 0.005 0.048 1976 0.004 0.036 1977 0.000 0.034 1978 0.003 0.042 1979 0.002 0.057 1980 0.007 0.063 1981 0.003 0.045 1982 0.006 0.067 1983 0.005 0.049 1984 0.003 0.033 1985 0.002 0.045 1986 0.008 0.038 1987 0.007 0.057 1988 0.003 0.033 1989 0.002 0.041 1990 0.015 0.095 1991 0.009 0.072 1992 0.004 0.032 1993 0.004 0.027 1994 0.001 0.027 1995 0.005 0.040 1996 0.011 0.048 1997 0.009 0.044 1998 0.002 0.040 1999 0.009 0.093 2000 0.004 0.044 2001 0.001 0.044 2002 0.004 0.060 2003 0.005 0.048 2004 0.007 0.086 2005 0.005 0.039 2006 0.006 0.035 2007 0.011 0.085 2008 0.015 0.070 2009 0.007 0.050 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #14 Rank Predeveloped Mitigated 1 0.0155 0.0950 2 0.0148 0.0931 3 0.0115 0.0857 4 0.0113 0.0852 INDIVIDUAL-CB 4/1/2024 12:27:50 PM Page 135 5 0.0106 0.0721 6 0.0094 0.0704 7 0.0093 0.0671 8 0.0089 0.0632 9 0.0084 0.0618 10 0.0079 0.0612 11 0.0075 0.0597 12 0.0074 0.0569 13 0.0073 0.0566 14 0.0072 0.0563 15 0.0067 0.0556 16 0.0066 0.0546 17 0.0066 0.0505 18 0.0059 0.0494 19 0.0058 0.0493 20 0.0057 0.0490 21 0.0054 0.0478 22 0.0053 0.0477 23 0.0053 0.0477 24 0.0052 0.0472 25 0.0052 0.0466 26 0.0048 0.0451 27 0.0048 0.0450 28 0.0047 0.0444 29 0.0046 0.0444 30 0.0043 0.0442 31 0.0042 0.0438 32 0.0041 0.0424 33 0.0041 0.0412 34 0.0041 0.0411 35 0.0041 0.0402 36 0.0040 0.0396 37 0.0039 0.0396 38 0.0038 0.0391 39 0.0037 0.0390 40 0.0037 0.0389 41 0.0036 0.0387 42 0.0036 0.0384 43 0.0035 0.0381 44 0.0035 0.0378 45 0.0034 0.0358 46 0.0033 0.0356 47 0.0033 0.0352 48 0.0033 0.0351 49 0.0032 0.0351 50 0.0031 0.0338 51 0.0030 0.0330 52 0.0029 0.0329 53 0.0027 0.0327 54 0.0025 0.0325 55 0.0021 0.0314 56 0.0020 0.0311 57 0.0019 0.0300 58 0.0019 0.0287 59 0.0013 0.0275 60 0.0007 0.0270 61 0.0005 0.0268 INDIVIDUAL-CB 4/1/2024 12:27:50 PM Page 141 POC 15 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #15 Total Pervious Area:0.158 Total Impervious Area:0 Mitigated Landuse Totals for POC #15 Total Pervious Area:0.057 Total Impervious Area:0.101 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #15 Return Period Flow(cfs) 2 year 0.004645 5 year 0.007296 10 year 0.008798 25 year 0.010389 50 year 0.011374 100 year 0.012211 Flow Frequency Return Periods for Mitigated. POC #15 Return Period Flow(cfs) 2 year 0.042907 5 year 0.056008 10 year 0.065137 25 year 0.077217 50 year 0.086625 100 year 0.096394 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #15 Year Predeveloped Mitigated 1949 0.005 0.060 1950 0.006 0.056 1951 0.010 0.037 1952 0.003 0.028 1953 0.003 0.031 1954 0.004 0.035 1955 0.006 0.039 1956 0.005 0.038 1957 0.004 0.046 1958 0.005 0.035 1959 0.004 0.033 INDIVIDUAL-CB 4/1/2024 12:28:21 PM Page 142 1960 0.007 0.038 1961 0.004 0.038 1962 0.002 0.031 1963 0.003 0.038 1964 0.004 0.034 1965 0.003 0.048 1966 0.003 0.030 1967 0.006 0.053 1968 0.004 0.060 1969 0.004 0.044 1970 0.003 0.040 1971 0.003 0.048 1972 0.008 0.054 1973 0.003 0.027 1974 0.004 0.046 1975 0.005 0.047 1976 0.004 0.035 1977 0.000 0.033 1978 0.003 0.042 1979 0.002 0.056 1980 0.007 0.062 1981 0.003 0.044 1982 0.006 0.066 1983 0.005 0.049 1984 0.003 0.032 1985 0.002 0.044 1986 0.008 0.037 1987 0.007 0.056 1988 0.003 0.033 1989 0.002 0.041 1990 0.015 0.092 1991 0.009 0.070 1992 0.003 0.032 1993 0.004 0.026 1994 0.001 0.027 1995 0.005 0.039 1996 0.011 0.047 1997 0.009 0.043 1998 0.002 0.040 1999 0.009 0.091 2000 0.004 0.043 2001 0.001 0.043 2002 0.004 0.058 2003 0.005 0.047 2004 0.007 0.084 2005 0.005 0.038 2006 0.006 0.034 2007 0.011 0.083 2008 0.014 0.069 2009 0.007 0.050 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #15 Rank Predeveloped Mitigated 1 0.0149 0.0922 2 0.0143 0.0910 3 0.0111 0.0840 4 0.0109 0.0827 INDIVIDUAL-CB 4/1/2024 12:28:21 PM Page 143 5 0.0102 0.0702 6 0.0091 0.0686 7 0.0090 0.0656 8 0.0085 0.0616 9 0.0081 0.0604 10 0.0076 0.0600 11 0.0072 0.0583 12 0.0071 0.0562 13 0.0070 0.0559 14 0.0069 0.0556 15 0.0065 0.0543 16 0.0064 0.0532 17 0.0063 0.0500 18 0.0057 0.0487 19 0.0055 0.0484 20 0.0055 0.0480 21 0.0052 0.0468 22 0.0051 0.0465 23 0.0051 0.0465 24 0.0050 0.0462 25 0.0050 0.0457 26 0.0047 0.0443 27 0.0046 0.0443 28 0.0046 0.0435 29 0.0044 0.0435 30 0.0041 0.0433 31 0.0040 0.0433 32 0.0040 0.0418 33 0.0039 0.0408 34 0.0039 0.0403 35 0.0039 0.0396 36 0.0039 0.0390 37 0.0038 0.0389 38 0.0037 0.0383 39 0.0036 0.0383 40 0.0036 0.0382 41 0.0035 0.0379 42 0.0035 0.0377 43 0.0034 0.0373 44 0.0033 0.0370 45 0.0032 0.0352 46 0.0032 0.0349 47 0.0032 0.0345 48 0.0031 0.0345 49 0.0031 0.0344 50 0.0030 0.0332 51 0.0029 0.0327 52 0.0028 0.0326 53 0.0026 0.0322 54 0.0024 0.0319 55 0.0021 0.0310 56 0.0020 0.0308 57 0.0018 0.0296 58 0.0018 0.0284 59 0.0012 0.0272 60 0.0006 0.0268 61 0.0004 0.0265 INDIVIDUAL-CB 4/1/2024 12:28:21 PM Page 149 POC 16 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #16 Total Pervious Area:0.144 Total Impervious Area:0 Mitigated Landuse Totals for POC #16 Total Pervious Area:0.05 Total Impervious Area:0.094 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #16 Return Period Flow(cfs) 2 year 0.004234 5 year 0.006649 10 year 0.008018 25 year 0.009468 50 year 0.010366 100 year 0.011129 Flow Frequency Return Periods for Mitigated. POC #16 Return Period Flow(cfs) 2 year 0.039683 5 year 0.051692 10 year 0.060048 25 year 0.071089 50 year 0.079679 100 year 0.088591 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #16 Year Predeveloped Mitigated 1949 0.004 0.056 1950 0.005 0.052 1951 0.009 0.034 1952 0.003 0.026 1953 0.002 0.029 1954 0.004 0.033 1955 0.006 0.036 1956 0.005 0.035 1957 0.004 0.043 1958 0.004 0.032 1959 0.004 0.030 INDIVIDUAL-CB 4/1/2024 12:28:52 PM Page 150 1960 0.006 0.035 1961 0.004 0.035 1962 0.002 0.029 1963 0.003 0.035 1964 0.004 0.032 1965 0.003 0.044 1966 0.003 0.027 1967 0.006 0.049 1968 0.004 0.056 1969 0.004 0.040 1970 0.003 0.037 1971 0.003 0.045 1972 0.007 0.050 1973 0.003 0.025 1974 0.003 0.042 1975 0.005 0.043 1976 0.003 0.032 1977 0.000 0.031 1978 0.003 0.039 1979 0.002 0.052 1980 0.007 0.057 1981 0.003 0.041 1982 0.005 0.060 1983 0.005 0.045 1984 0.003 0.030 1985 0.002 0.041 1986 0.007 0.034 1987 0.006 0.052 1988 0.003 0.030 1989 0.002 0.038 1990 0.014 0.085 1991 0.008 0.065 1992 0.003 0.030 1993 0.003 0.025 1994 0.001 0.025 1995 0.005 0.036 1996 0.010 0.043 1997 0.008 0.040 1998 0.002 0.037 1999 0.008 0.084 2000 0.003 0.040 2001 0.001 0.040 2002 0.004 0.054 2003 0.005 0.043 2004 0.006 0.077 2005 0.004 0.035 2006 0.005 0.032 2007 0.010 0.076 2008 0.013 0.063 2009 0.006 0.046 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #16 Rank Predeveloped Mitigated 1 0.0136 0.0846 2 0.0130 0.0840 3 0.0101 0.0775 4 0.0099 0.0758 INDIVIDUAL-CB 4/1/2024 12:28:52 PM Page 151 5 0.0093 0.0645 6 0.0083 0.0630 7 0.0082 0.0604 8 0.0078 0.0567 9 0.0073 0.0557 10 0.0069 0.0555 11 0.0066 0.0538 12 0.0065 0.0522 13 0.0064 0.0519 14 0.0063 0.0517 15 0.0059 0.0500 16 0.0058 0.0489 17 0.0058 0.0465 18 0.0052 0.0452 19 0.0051 0.0447 20 0.0050 0.0443 21 0.0047 0.0432 22 0.0046 0.0429 23 0.0046 0.0428 24 0.0046 0.0427 25 0.0045 0.0421 26 0.0043 0.0410 27 0.0042 0.0410 28 0.0042 0.0402 29 0.0040 0.0402 30 0.0037 0.0401 31 0.0036 0.0401 32 0.0036 0.0387 33 0.0036 0.0379 34 0.0036 0.0373 35 0.0036 0.0368 36 0.0035 0.0361 37 0.0034 0.0361 38 0.0034 0.0354 39 0.0033 0.0354 40 0.0033 0.0353 41 0.0032 0.0350 42 0.0032 0.0348 43 0.0031 0.0345 44 0.0030 0.0341 45 0.0029 0.0325 46 0.0029 0.0323 47 0.0029 0.0320 48 0.0029 0.0319 49 0.0028 0.0318 50 0.0028 0.0307 51 0.0026 0.0304 52 0.0026 0.0303 53 0.0024 0.0298 54 0.0022 0.0296 55 0.0019 0.0287 56 0.0018 0.0286 57 0.0017 0.0274 58 0.0017 0.0264 59 0.0011 0.0253 60 0.0006 0.0249 61 0.0004 0.0245 INDIVIDUAL-CB 4/1/2024 12:28:52 PM Page 157 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. INDIVIDUAL-CB 4/1/2024 12:28:52 PM Page 159 Mitigated Schematic INDIVIDUAL-CB 4/1/2024 12:28:53 PM Page 174 Mitigated HSPF Message File INDIVIDUAL-CB 4/1/2024 12:28:53 PM Page 175 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 20069 - exist. vault 3/19/2024 4:35:45 PM Page 37 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 FES Project no. 20069 Page 57 APPENDIX E: STORMFILTER DETAILS SFMH#1(W) 288.59LCPE12"(S) 290.82LCPE12"300.590.0167 CFS7 PSC18"0.0266 CFS0.1153 CFSZPG212"6" CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 1 April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter® With ZPG Media at 1 gpm/sq ft media surface area Ecology’s Decision: Based on the CONTECH Engineered Solutions’ (CONTECH) application submissions, Ecology hereby issues a General Use Level Designation (GULD) for the Stormwater Management StormFilter® (StormFilter): 1. As a basic stormwater treatment practice for total suspended solids (TSS) removal,  Using ZPG™ media (zeolite/perlite/granular activated carbon), with the size distribution described below,  Sized at a hydraulic loading rate of 1 gpm/ft2 of media surface area, per Table 1, and  Internal bypassing needs to be consistent with the design guidelines in CONTECH’s current product design manual. Table 1. StormFilter Design Flow Rates per Cartridge 2. Ecology approves StormFilter systems containing ZPG™ media for treatment at the hydraulic loading rates shown in Table 1, and sized based on the water quality design flow rate for an off-line system when using an external bypass vault or a treatment vault with an internal bypass. Contech designs their StormFilter systems to maintain treatment of the water quality design flow while routing excess flows around the treatment chamber during periods of peak bypass. The water quality design flow rates are calculated using the following procedures:  Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model. Effective Cartridge Height (inches) 12 18 27 Cartridge Flow Rate (gpm/cartridge) 5 7.5 11.3 CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 2  Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual.  Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. This designation has no expiration date, but Ecology may amend or revoke it. Ecology’s Conditions of Use: The StormFilter with ZPG media shall comply with the following conditions: 1. Design, install, operate, and maintain the StormFilter with ZPG media in accordance with applicable Contech Engineered Solutions manuals, documents, and the Ecology Decision. 2. Install StormFilter systems to bypass flows exceeding the water quality treatment rate. Additionally, high flows will not re-suspend captured sediments. Design StormFilter systems in accordance with the performance goals in Ecology's most recent Stormwater Manual and CONTECH’s Product Design Manual Version 4.1 (April 2006), or most current version, unless otherwise specified. 3. Owners must follow the design, pretreatment, land use application, and maintenance criteria in CONTECH’s Design Manual. 4. Pretreatment of TSS and oil and grease may be necessary, and designers shall provide pre-treatment in accordance with the most current versions of the CONTECH’s Product Design Manual (April 2006) or the applicable Ecology Stormwater Manual. Design pre-treatment using the performance criteria and pretreatment practices provided on Ecology’s “Evaluation of Emerging Stormwater Treatment Technologies” website. 5. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured filter treatment device.  Typically, CONTECH designs StormFilter systems for a target filter media replacement interval of 12 months. Maintenance includes removing accumulated sediment from the vault, and replacing spent cartridges with recharged cartridges. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 3  Indications of the need for maintenance include effluent flow decreasing to below the design flow rate, as indicated by the scumline above the shoulder of the cartridge.  Owners/operators must inspect StormFilter with ZPG media for a minimum of twelve months from the start of post-construction operation to determine site-specific maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections.  Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable of determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability.  When inspections are performed, the following findings typically serve as maintenance triggers:  Accumulated vault sediment depths exceed an average of 2 inches, or  Accumulated sediment depths on the tops of the cartridges exceed an average of 0.5 inches, or  Standing water remains in the vault between rain events, or  Bypass occurs during storms smaller than the design storm.  Note: If excessive floatables (trash and debris) are present, perform a minor maintenance consisting of gross solids removal, not cartridge replacement. 6. CONTECH shall maintain readily available reports listed under “Application Documents” (above) as public, as well as the documentation submitted with its previous conditional use designation application. CONTECH shall provide links to this information from its corporate website, and make this information available upon request, at no cost and in a timely manner. 7. ZPG™ media used shall conform with the following specifications:  Each cartridge contains a total of approximately 2.6 cubic feet of media. The ZPG™ cartridge consists of an outer layer of perlite that is approximately 1.3 cubic feet in volume and an inner layer, consisting of a mixture of 90% zeolite and 10% granular activated carbon, which is approximately 1.3 cubic feet in volume.  Perlite Media: Perlite media shall be made of natural siliceous volcanic rock free of any debris or foreign matter. The expanded perlite shall CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 4 have a bulk density ranging from 6.5 to 8.5 lbs per cubic foot and particle sizes ranging from 0.09” (#8 mesh) to 0.38” (3/8” mesh).  Zeolite Media: Zeolite media shall be made of naturally occurring clinoptilolite. The zeolite media shall have a bulk density ranging from 44 to 50 lbs per cubic foot and particle sizes ranging from 0.13” (#6 mesh) to 0.19” (#4 mesh). Additionally, the cation exchange capacity (CEC) of zeolite shall range from approximately 1.0 to 2.2 meq/g.  Granular Activated Carbon: Granular activated carbon (GAC) shall be made of lignite coal that has been steam-activated. The GAC media shall have a bulk density ranging from 28 to 31 lbs per cubic foot and particle sizes ranging from a 0.09” (#8 mesh) to 0.19” (#4 mesh). Approved Alternate Configurations Peak Diversion StormFilter 1. The Peak Diversion StormFilter allows for off-line bypass within the StormFilter structure. Design capture flows and peak flows enter the inlet bay which contains an internal weir. The internal weir allows design flows to enter the cartridge bay through a transfer hole located at the bottom of the inlet bay while the unit routs higher flows around the cartridge bay. 2. To select the size of the Peak Diversion StormFilter unit, the designer must determine the number of cartridges required and size of the standard StormFilter using the site- specific water quality design flow and the StormFilter Design Flow Rates per Cartridge as described above. 3. New owners may not install the Peak Diversion StormFilter at an elevation or in a location where backwatering may occur. Applicant: Contech Engineered Solutions Applicant’s Address: 11835 NE Glenn Widing Dr. Portland, OR 97220 Application Documents: The applicant’s master report, titled, “The Stormwater Management StormFilter Basic Treatment Application for General Use Level Designation in Washington”, Stormwater Management, Inc., November 1, 2004, includes the following reports:  (Public) Evaluation of the Stormwater Management StormFilter Treatment System: Data Validation Report and Summary of the Technical Evaluation Engineering Report (TEER) by Stormwater Management Inc., October 29, 2004 Ecology’s technology assessment protocol requires the applicant to hire an independent consultant to complete the following work: CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 5 1. Complete the data validation report. 2. Prepare a TEER summary, including a testing summary and conclusions compared with the supplier’s performance claims. 3. Provide a recommendation of the appropriate technology use level. 4. Work with Ecology to post recommend relevant information on Ecology’s website. 5. Provide additional testing recommendations, if needed.” 6. This report, authored by Dr. Gary Minton, Ph. D., P.E., Resource Planning Associates, satisfies the Ecology requirement.  (Public) “Performance of the Stormwater Management StormFilter Relative to the Washington State Department of Ecology Performance Goals for Basic Treatment,” is a summary of StormFilter performance that strictly adheres to the criteria listed in the Guidance for Evaluating Emerging Stormwater Treatment Technologies, Technology Assessment Protocol – Ecology (TAPE).  “Heritage Marketplace Field Evaluation: Stormwater Management StormFilter with ZPG™ Media,” is a report showing all of the information collected at Site A as stated in the SMI Quality Assurance Project Plan (QAPP). This document contains detailed information regarding each storm event collected at this site, and it provided a detailed overview of the data and project.  “Lake Stevens Field Evaluation: Stormwater Management StormFilter with ZPG™ Media,” is a report that corresponds to Site E as stated in the SMI QAPP. This document contains detailed information regarding each storm collected at this site, and includes a detailed overview of the data and project.  (Public) “Evaluation of the Stormwater Management StormFilter for the removal of SIL-CO-SIL 106, a standardized silica product: ZPG™ at 7.5 GPM” is a report that describes laboratory testing at full design flow.  “Factors Other Than Treatment Performance.”  “State of Washington Installations.”  “Peak Diversion StormFilter” is a technical document demonstrating the Peak Diversion StormFilter system complies with the Stormwater Management Manual for Western Washington Volume V Section 4.5.1. Above-listed documents noted as “public” are available by contacting CONTECH. Applicant's Use Level Request: That Ecology grant a General Use Level Designation for Basic Treatment for the StormFilter using ZPG™ media (zeolite/perlite/granular activated carbon) at a hydraulic loading rate of 1 gpm/ft2 of media surface area in accordance with Ecology's 2011 Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol – Ecology (TAPE). CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 6 Applicant's Performance Claim: The combined data from the two field sites reported in the TER (Heritage Marketplace and Lake Stevens) indicate that the performance of a StormFilter system configured for inline bypass with ZPG™ media and a hydraulic loading rate of 1 gpm/ft2 of media surface area meets Ecology performance goals for Basic Treatment. Ecology’s Recommendations: Based on the weight of the evidence and using its best professional judgment, Ecology finds that:  StormFilter, using ZPG™ media and operating at a hydraulic loading rate of no more than 1 gpm/ft2 of media surface area, is expected to provide effective stormwater treatment achieving Ecology’s Basic Treatment (TSS removal) performance goals. Contech demonstrated this is through field and laboratory testing performed in accordance with the approved protocol. StormFilter is deemed satisfactory with respect to factors other than treatment performance (e.g., maintenance; see the protocol’s Appendix B for complete list). Findings of Fact:  Influent TSS concentrations and particle size distributions were generally within the range of what Ecology considers “typical” for western Washington (silt-to-silt loam).  Contech sampled thirty-two (32) storm events at two sites for storms from April 2003 to March 2004, of which Contech deemed twenty-two (22) as “qualified” and were therefore included in the data analysis set.  Statistical analysis of these 22 storm events verifies the data set’s adequacy.  Analyzing all 22 qualifying events, the average influent and effluent concentrations and aggregate pollutant load reduction are 114 mg/L, 25 mg/L, and 82%, respectively.  Analyzing all 22 qualifying events based on the estimated average flow rate during the event (versus the measured peak flow rate), and more heavily weighting those events near the design rate (versus events either far above or well below the design rate) does not significantly affect the reported results.  For the 7 qualifying events with influent TSS concentrations greater than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 241 mg/L, 34 mg/L, and 89%, respectively. If we exclude the 2 of 7 events that exceed the maximum 300 mg/L specified in Ecology’s guidelines, the average influent and effluent concentrations and aggregate pollutant load reduction are 158 mg/L, 35 mg/L, and 78%, respectively.  For the 15 qualifying events with influent TSS concentrations less than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 55 mg/L, 20 mg/L, and 61%, respectively. If the 6 of 15 events that fall below the minimum 33 mg/L TSS specified in Ecology’s guidelines are excluded, the average CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 7 influent and effluent concentrations and aggregate pollutant load reduction are 78 mg/L, 26 mg/L, and 67%, respectively.  For the 8 qualifying events with peak discharge exceeding design flow (ranging from 120 to 257% of the design rate), results ranged from 52% to 96% TSS removal, with an average of 72%.  Due to the characteristics of the hydrographs, the field results generally reflect flows below (ranging between 20 and 60 percent of) the tested facilities’ design rate. During these sub-design flow rate periods, some of the cartridges operate at or near their individual full design flow rate (generally between 4 and 7.5 GPM for an 18” cartridge effective height) because their float valves have opened. Float valves remain closed on the remaining cartridges, which operate at their base “trickle” rate of 1 to 1.5 GPM.  Laboratory testing using U.S. Silica’s Sil-Co-Sil 106 fine silica product showed an average 87% TSS removal for testing at 7.5 GPM per cartridge (100% design flow rate).  Other relevant testing at I-5 Lake Union, Greenville Yards (New Jersey), and Ski Run Marina (Lake Tahoe) facilities shows consistent TSS removals in the 75 to 85% range. Note that the evaluators operated the I-5 Lake Union at 50%, 100%, and 125% of design flow.  SMI’s application included a satisfactory “Factors other than treatment performance” discussion. Note: Ecology’s 80% TSS removal goal applies to 100 mg/l and greater influent TSS. Below 100 mg/L influent TSS, the goal is 20 mg/L effluent TSS. Technology Description: The Stormwater Management StormFilter® (StormFilter), a flow-through stormwater filtration system, improves the quality of stormwater runoff from the urban environment by removing pollutants. The StormFilter can treat runoff from a wide variety of sites including, but not limited to: retail and commercial development, residential streets, urban roadways, freeways, and industrial sites such as shipyards, foundries, etc. Operation: The StormFilter is typically comprised of a vault that houses rechargeable, media-filled, filter cartridges. Various media may be used, but this designation covers only the zeolite- perlite-granulated activated carbon (ZPG™) medium. Stormwater from storm drains percolates through these media-filled cartridges, which trap particulates and may remove pollutants such as dissolved metals, nutrients, and hydrocarbons. During the filtering process, the StormFilter system also removes surface scum and floating oil and grease. Once filtered through the media, the treated stormwater is directed to a collection pipe or discharged to an open channel drainage way. This document includes a bypass schematic for flow rates exceeding the water quality design flow rate on page 8. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 8 StormFilter Configurations: Contech offers the StormFilter in multiple configurations: precast, high flow, catch basin, curb inlet, linear, volume, corrugated metal pipe, drywell, and CON/Span form. Most configurations use pre-manufactured units to ease the design and installation process. Systems may be either uncovered or covered underground units. The typical precast StormFilter unit is composed of three sections: the energy dissipater, the filtration bay, and the outlet sump. As Stormwater enters the inlet of the StormFilter vault through the inlet pipe, piping directs stormwater through the energy dissipater into the filtration bay where treatment will take place. Once in the filtration bay, the stormwater ponds and percolates horizontally through the media contained in the StormFilter cartridges. After passing through the media, the treated water in each cartridge collects in the cartridge’s center tube from where piping directs it into the outlet sump by a High Flow Conduit under-drain manifold. The treated water in the outlet sump discharges through the single outlet pipe to a collection pipe or to an open channel drainage way. In some applications where you anticipate heavy grit loads, pretreatment by settling may be necessary. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 9 Figure 1. Stormwater Management StormFilter Configuration with Bypass CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 10 Figure 2. The StormFilter Cartridge Cartridge Operation: As the water level in the filtration bay begins to rise, stormwater enters the StormFilter cartridge. Stormwater in the cartridge percolates horizontally through the filter media and passes into the cartridge’s center tube, where the float in the cartridge is in a closed (downward) position. As the water level in the filtration bay continues to rise, more water passes through the filter media and into the cartridge’s center tube. Water displaces the air in the cartridge and it purges from beneath the filter hood through the one-way check valve located in the cap. Once water fills the center tube there is enough buoyant force on the float to open the float valve and allow the treated water to flow into the under-drain manifold. As the treated water drains, it tries to pull in air behind it. This causes the check valve to close, initiating a siphon that draws polluted water throughout the full surface area and volume of the filter. Thus, water filters through the entire filter cartridge throughout the duration of the storm, regardless of the water surface elevation in the filtration bay. This continues until the water surface elevation drops to the elevation of the scrubbing regulators. At this point, the siphon begins to break and air quickly flows beneath the hood through the scrubbing regulators, causing energetic bubbling between the inner surface of the hood and the outer surface of the filter. This bubbling agitates and cleans the surface of the filter, releasing accumulated sediments on the surface, flushing them from beneath the hood, and allowing them to settle to the vault floor. Adjustable cartridge flow rate: Inherent to the design of the StormFilter is the ability to control the individual cartridge flow rate with an orifice-control disc placed at the base of the cartridge. Depending on the treatment requirements and on the pollutant characteristics of the influent stream as CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 11 specified in the CONTECH Product Design Manual, operators may adjust the flow rate through the filter cartridges. By decreasing the flow rate through the filter cartridges, the influent contact time with the media is increased and the water velocity through the system is decreased, thus increasing both the level of treatment and the solids removal efficiencies of the filters, respectively (de Ridder, 2002). Recommended research and development: Ecology encourages CONTECH to pursue continuous improvements to the StormFilter. To that end, CONTECH recommends the following actions:  Determine, through laboratory testing, the relationship between accumulated solids and flow rate through the cartridge containing the ZPG™ media. Completed 11/05.  Determine the system’s capabilities to meet Ecology’s enhanced, phosphorus, and oil treatment goals.  Develop easy-to-implement methods of determining that a StormFilter facility requires maintenance (cleaning and filter replacement). Contact Information: Applicant Contact: Jeremiah Lehman Contech Engineered Solutions 11835 NE Glenn Widing Drive Portland, OR, 97220 503-258-3136 jlehman@conteches.com Applicant Web link http://www.conteches.com/ CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 12 Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology Contact: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Revision History Date Revision Jan 2005 Original Use Level Designation Dec 2007 Revision May 2012 Maintenance requirements updated November 2012 Design Storm and Maintenance requirements updated January 2013 Updated format to match Ecology standard format September 2014 Added Peak Diversion StormFilter Alternate Configuration November 2016 Revised Contech contact information April 2017 Revised sizing language to note sizing based on Off-line calculations