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APPROVED STM RESUB 3 STORMWATER REPORT. 3.12.21
Approval of this project under BLD2019-1590 is based on promised mitigation upstream within the same drainage basin at Yost Park. Under separate permit, equivalent mitigation for the following surfaces must be provided per MR #7 (flow control) upstream of the project location: Minimum Impervious Surfacing: 80,150 SF (1.84 ac) Minimum Additional Surfacing: 144,619 SF (3.32 ac) Additional surfacing value may be pervious or impervious or any combination thereof. As shown in this report, because upstream areas may allow for infiltration of runoff, achieving flow control equivalence for these surfaces may require collecting surface amounts less than those listed above. Exemptions and thresholds, if still applicable, would need to consider the combined impacts and surfaces of both projects. Failure to complete such mitigation will void stormwater approval issued herein. Civic Center Playfield Stormwater Technical Information Report March 12, 2021 1 Permit Resubmittal iqConsulting Engineers APPLIES WITH APPLICABLE CITY STORMWATER CODE BLD2019-1590 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Stormwater Technical Information Report March 12, 2021 Prepared for: Walker Macy 1218 Third Avenue, Suite 1310 Seattle, WA 98101 Prepared by: KPFF Consulting Engineers 1601 Fifth Avenue, Suite 1600 Seattle, WA 98101 (206) 622-5822 KPFF Project No. 1700910 Puja Shaw, PE, Associate Dan Veldee, PE 03/12/2021 RESUB Civic Center Playfield — Walkd`d1MU 2021 CITY OF DMONDS DEVELOPM T SERVICES DEPARTMENT 1 EN KPFF Consulting Engineers Mar 25 2021 CITY OF EDMONDS H DEVELOPMENT SERVICES DEPARTMENT Table of Contents 1. Project Overview...........................................................................................................................................1 2. Minimum Requirements...............................................................................................................................2 Minimum Requirement No. 1: Preparation of Stormwater Site Plans......................................................2 Minimum Requirement No. 2: Construction Stormwater Pollution Prevention Plan (CSWPPP).............2 Minimum Requirement No. 3: Source Control of Pollution......................................................................2 Minimum Requirement No. 4: Preservation of Natural Drainage Systems and Outfalls ..........................2 Minimum Requirement No. 5: On -Site Stormwater Management............................................................2 Minimum Requirement No. 6: Runoff Treatment.....................................................................................4 Minimum Requirement No. 7: Flow Control.............................................................................................4 Minimum Requirement No. 8: Wetlands Protection.................................................................................4 Minimum Requirement No. 9: Operation and Maintenance.....................................................................4 3. Existing Conditions Summary.....................................................................................................................4 ExistingTopography.................................................................................................................................4 Groundwater.............................................................................................................................................4 SoilConditions..........................................................................................................................................4 NativeProtection Areas............................................................................................................................4 4. Off -Site Analysis...........................................................................................................................................4 5. Permanent Stormwater Control Plan..........................................................................................................5 Conveyance.............................................................................................................................................. 5 Buoyancy..................................................................................................................................................5 OSM.........................................................................................................................................................5 RunoffTreatment......................................................................................................................................5 FlowControl.............................................................................................................................................6 6. Construction Stormwater Pollution Prevention Plan (SWPPP)...............................................................8 7. Special Reports and Studies.......................................................................................................................8 8. Other Permits................................................................................................................................................8 9. Operation and Maintenance Manual...........................................................................................................8 List of Figures Figure1-1: Vicinity Map.........................................................................................................................................1 Figure5-1: Historic Marsh Image..........................................................................................................................7 List of Tables Table 5-1: Yost Park Detention Trade Area Summary.........................................................................................6 Table 5-2: Civic Center Playfield Detention Area Summary................................................................................8 RESUB Civic Center Playfield — WalWd1MU 2021 CITY DMONDS DEVELO T SERVICES DEPARTMENT Appendices Appendix A— Site Figures Appendix B — Calculations Appendix C — Construction Stormwater Pollution Prevention Plan Appendix D — Operation and Maintenance Manual Appendix E — Geotechnical Report Appendix F — Water Quality Vault Detail KPFF Consulting Engineers Mar 25 2021 CITY OF EDMONDS iv DEVELOPMENT SERVICES DEPARTMENT 1. Project Overview The project site is located at 310 Sixth Avenue North in downtown Edmonds, Washington. The approximate 8- acre park is bounded by Sixth Avenue North to the west, Seventh Avenue North to the east, and alleys to the north and south. Refer to Figure 1-1 for a vicinity map. The existing site consists of athletic fields, a playground, a skate park, tennis courts, and the Boys & Girls Club facilities. Proposed site improvements include a multi -use plaza, a new skate park, water feature, multi -use lawn and playfields, playground, petanque courts, multi -use courts, a shaded pavilion, walking/jogging paths, exercise stations, picnic area, youth climbing wall, lawn terraces, berms, planting, and street improvements up to back of curb on Sixth Avenue North. It is anticipated that minor sidewalk repair work will need to be done on Seventh Avenue North. The Boys & Girls Club facilities are not included in the project scope and will be designed as part of a separate project. Utility improvements include new water and sewer services to serve the restrooms and water feature and new storm drainage infrastructure, including facilities to provide detention and water quality. Currently stormwater runoff is collected by a limited number of yard drains and catch basins and is routed via piped connections to the 12-inch concrete storm main in Sixth Avenue North. While stormwater collection occurs on portions of the existing site, surface water ponds in other areas where drainage structures do not exist. A 12-inch concrete storm main also runs east -west through the south side of the site connecting the storm main in Sixth Avenue North to the storm main in Seventh Avenue North. BrJJUf is _ardirig Shure ine Sancludry. Brackett's Landirig North \1 ath d a� ryC 2 Aioh�vr�y Aloha St P ry�c Holy Rosary Church = Soundview Apartments O s Edmonds Center Q GI_ s, For the Arts a z Civic Center so`eDues� Playfield 7 Uniled States Postal Service Owl h >� -4-es st y r7 Dayton St Aloha St PROJECT SITE Ech,,aa n 19 City of Edmonds z Bell st Bell SI Rusty Pelican Cafe 4 _ s Z Frances Anderson Center Starbucks19 © A Main St 7 Edmonds Library - Sno-Isle Libraries Las Brisas 9 Figure 1-1: Vicinity Map Dayton St J 61ee st Daley SI n `m Z Sprague St Edmonds St I� Edmond Driftwood Player Dayton St RESUB Civic Center Playfield — Walkd`d abU 2021 CITY O DMONDS DEVELOPM NT SERVICES DEPARTMENT 2. Minimum Requirements The project site is subject to the Edmonds Community Development Code (ECDC) 18.30 — Stormwater Management Code, the Edmonds Stormwater Addendum, and the 2019 Stormwater Management Manual for Western Washington (SWMMWW). The development is considered a Category 2 project because it will create more than 5,000 square feet (SF) of new plus replaced hard surface area. Therefore, Minimum Requirements 1 through 9 apply. MINIMUM REQUIREMENT NO. 1: PREPARATION OF STORMWATER SITE PLANS This Stormwater Site Plan has been prepared according to Volume I, Chapter 3 of the SWMMWW, the Edmonds Stormwater Addendum, and ECDC 18.30. MINIMUM REQUIREMENT NO. 2: CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (CSWPPP) The project results in 2,000 SF or more of new plus replaced hard surface area; therefore, a CSWPPP is required. See Section 6 for additional details. See Appendix C for the CSWPPP. MINIMUM REQUIREMENT NO. 3: SOURCE CONTROL OF POLLUTION Source controls will be installed to prevent sediment from entering waterways. See Section 6 for additional details. MINIMUM REQUIREMENT NO. 4: PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS The site currently drains to a 12-inch storm main in Sixth Avenue North. The project will discharge to a different 12-inch storm main in Sprague Street that combines with the main in Sixth Avenue North approximately 950 feet downstream. Therefore, the existing outfall is maintained. See Section 4 for an off -site analysis of the downstream system. MINIMUM REQUIREMENT NO. 5: ON -SITE STORMWATER MANAGEMENT This project triggers Minimum Requirements 1-9 and discharges to the City's MS4; therefore, a feasibility study for the items in List No. 2 was performed. The results of this study are outlined below. Lawn and Landscaped Areas • Post -Construction Soil Quality and Depth in accordance with Best Management Practice (BMP) T5.13 in Chapter 11 of Volume V. o Feasible —All disturbed areas will be amended in accordance with BMP T5.13 in Chapter 11 of Volume V. Roofs • Full Dispersion in accordance with BMP T5.30 in Chapter 3 of Volume V. o Infeasible — The minimum forested or native vegetation flowpath length of 25 feet cannot be achieved. • Downspout Full Infiltration System in accordance with BMP T5.10A in Chapter 4 of Volume V. KPFF Consulting Engineers 2 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT o Infeasible — There is not at least 1 foot or more of permeable soil from the proposed bottom of infiltration system to the seasonal high groundwater table or other impermeable layer. 0 Bioretention in accordance with BMP T7.30 in Chapter 5 of Volume V. o Infeasible — There is not at least 1 foot or more of permeable soil from the proposed bottom of infiltration system to the seasonal high groundwater table or other impermeable layer. • Downspout Dispersion Systems in accordance with BMP T5.10B in Chapter 4 of Volume V. o Infeasible —A minimum vegetated flowpath of 50 feet for splashblocks and 25 feet for trenches cannot be provided. 0 Perforated Stub -out Connections in accordance with BMP T5.10C in Chapter 4 of Volume V. o Infeasible —A minimum vegetated flowpath of 50 feet for splashblocks and 25 feet for trenches cannot be provided. • Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum. o The detention requirement for Minimum Requirement No. 5 will be met by providing detention for Minimum Requirement No. 7. Other Hard Surfaces • Full Dispersion in accordance with BMP T5.30 in Chapter 3 of Volume V. o Infeasible — The minimum forested or native vegetation flowpath length of 25 feet cannot be achieved. • Permeable pavement in accordance with BMP T5.15 in Chapter 5 of Volume V. o Infeasible — Seasonal high groundwater would create saturated conditions within 1 foot of the bottom of the lowest gravel base course. • Bioretention in accordance with BMP T7.30 in Chapter 5 of Volume V. o Infeasible —A minimum vertical separation of 1 foot to the seasonal high groundwater would not be achieved below bioretention. • Sheet Flow Dispersion in accordance with BMP T5.12 in Chapter 3 of Volume V. o Infeasible — The required 10-foot-wide vegetated buffer downstream of and adjacent to the proposed hard surfaces cannot be achieved within the site boundary. • Concentrated Flow Dispersion in accordance with BMP T5.11 in Chapter 3 of Volume V. o Infeasible — The required 50-foot-long vegetated flowpath downstream of the storm drain collection system cannot be achieved within the site boundary. 0 Detention vaults or pipes in accordance with the Edmonds Stormwater Addendum. o The detention requirement for Minimum Requirement No. 5 will be met by providing detention for Minimum Requirement No. 7. The Boys & Girls Club will be part of a separate future project, and stormwater management will be addressed at that time. See Section 5 for BMP sizing information. RESUB Civic Center Playfield - WalkdWlabU 2021 CITYLOO DMONDS DEVE P T SERVICES DEPARTMENT MINIMUM REQUIREMENT NO. 6: RUNOFF TREATMENT The project is proposing more than 3/4 of an acre of pollution -generating pervious surfaces (PGPS); therefore, runoff treatment is required for all pollution -generating surfaces. Basic Treatment is required for this site. Water quality treatment is further described in Section 5 of this report. See Appendix A for basin areas. MINIMUM REQUIREMENT NO. 7: FLOW CONTROL The project discharges to Shell Creek and is proposing more than 10,000 square feet of new plus replaced hard surface; therefore, flow control is required. A portion of detention will be provided off -site on Yost Park via a detention trade, and the remainder of the detention will be provided on -site. Flow control is further described in Section 5 of this report. See Appendix A for basin areas. MINIMUM REQUIREMENT NO. 8: WETLANDS PROTECTION There are no wetlands within the project vicinity. MINIMUM REQUIREMENT NO. 9: OPERATION AND MAINTENANCE An Operation and Maintenance Manual is included in Appendix D. 3. Existing Conditions Summary EXISTING TOPOGRAPHY Elevation drops about 17 feet across the site from the southeast to northwest. In general, the site slopes down to the northwest corner, with low points and collection structures scattered across the site. GROUNDWATER Per the project Geotechnical Report, and supported by a supplemental summary of wet season groundwater monitoring completed in 2020, groundwater is assumed to be 2 feet below existing grade. See Appendix E for the project Geotechnical Report and supplemental groundwater monitoring memo. SOIL CONDITIONS See Appendix E for the project Geotechnical Report describing the existing soil conditions and recommendations for the proposed improvements. NATIVE PROTECTION AREAS There are no areas of native soil or vegetation that require protection; therefore, no protection is proposed. 4. Off -Site Analysis Site stormwater will connect to the 12-inch city system in Sprague Street. According to the City of Edmonds GIS, the 12-inch system flows east on Sprague Street for approximately 240 feet before turning southeast and connecting to the 12-inch system in Edmonds Street. The system continues northeast along Edmonds Street and then turns northwest on Third Avenue North. The system continues northeast on Third Avenue North and KPFF Consulting Engineers 4 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT upsizes to an 18-inch pipe. At Caspers Street the system turns east before discharging to Shell Creek near 342 Caspers Street. See Appendix A for the Downstream Analysis exhibit. 5. Permanent Stormwater Control Plan CONVEYANCE The project proposes to install new stormwater infrastructure including catch basins, manholes, conveyance swales, trench drains, french drains, underdrains, and gravel detention layers. The proposed storm drainage infrastructure will be designed to convey the 25-year storm event and to convey the 100-year storm event without overtopping. Conveyance calculations are included in Appendix B. The basin with the highest 25-year peak flow is Basin 1, which has a 25-year peak flow of 0.26 cfs. The pipe with the least capacity for the entire site is a 6-inch PVC pipe sloped at 0.5% with a full flow capacity of 0.52 cfs. The pipe with the least capacity can convey the 25-year peak flow from Basin 1. Therefore, all of stormwater infrastructure is adequately sized to convey the 25-year storm event. Additionally, the existing 25-year flow leaving the entire site is 2.09 cfs. The 25-year flow leaving the site will be reduced by the project to 1.87 cfs. Therefore, the downstream system should have capacity to accept runoff from the proposed site. BUOYANCY Buoyancy calculations were completed for all pipes, catch basins, and vaults encroaching into the high groundwater table, which is assumed to be 2 feet below existing grade per the project Geotechnical Report. Proposed pipe types for the project that encroach into the high groundwater table include 6-inch, 8-inch, and 12-inch PVC. Buoyancy calculations were run for all three pipe sizes assuming the inverts of the pipes were two feet below finished grade and fully submerged to the crown with unsaturated soil above the crown. All three scenarios passed with factors of safety above 5. Since no pipe encroaching into groundwater has an invert higher than two feet below finished grade, all pipes will have sufficient weight to resist the uplift due to groundwater. See Appendix B for Pipe Buoyancy Calculations. Proposed drainage structures that encroach into the high groundwater table include the water quality vault and Type 1 and Type 2 catch basins per City of Edmonds standard details. One Type 2 catch basin will require an extended base structure to achieve a factor of safety of 2. See Appendix B for Water Quality Vault and Catch Basin Buoyancy Calculations. OSM OSM will be achieved by providing detention for Minimum Requirement No. 7. Detention is further described in the Flow Control section below. RUNOFF TREATMENT Basic stormwater treatment facilities were selected in accordance with Chapter 3 of Volume I and Chapter 2 of Volume V of the SWMMWW. Basic treatment will be provided by Contech Stormfilters using PSORB Media RESUB Civic Center Playfield — Walkd`d1MU 2021 CITYLOO DMONDS DEVE P T SERVICES DEPARTMENT per the DOE General Use Level Designation (GULD). Areas mitigated for water quality are included in the Drainage Basin Map in Appendix A. Runoff treatment calculations and DOE GULD approval sheets are included in Appendix B. FLOW CONTROL A portion of flow control will be provided via a detention trade at Yost Park under a separate permit. Yost Park is located in the same drainage basin as the Civic Center Playfield site, discharges to an outfall that is located further upstream Shell Creek, and currently has no flow control facilities. Design at Yost Park is still in progress, but the objective is to provide flow control on both sites in order to meet the Standard Flow Control Requirement at a downstream point of connection from both sites. Civic Center Playfield will be modelled back to the pre -developed condition, and Yost Park will be modelled using the existing condition as the historic and proposed condition. Preliminary flow control calculations for the detention trade are included in Appendix B. See Appendix A for Yost Park Mitigated Area Map. See Table 5-1 for proposed detention trade areas. Table 5-1: Yost Park Detention Trade Area Summary Civic Center Playfield Mitigated On -site 57,499 SF (1.32 AC) 59,677 SF (1.37 AC) Civic Center Playfield Bypass 80,150 SF (1.84 AC) 144,619 SF (3.32 AC) Area Mitigated at Yost Park 75,025 SF (1.72 AC) 70,350 SF (1.62 AC) Surface types used in the Civic Center Playfield stormwater model are summarized below: • The pre -developed condition of Civic Center Playfield is modeled as wetland, based on an aerial photo from 1953 showing the site as a marsh (see Figure 5-1 below). • All proposed lawn and landscaped areas that are not directly above a gravel detention layer, with the exception of reinforced lawn areas, will meet the post -construction soil quality and depth requirement and will be modeled as pasture. Reinforced lawn areas will be modeled as lawn. The reinforcement system is set on an aggregate base and will be infilled with topsoil. This system will act similarly to a typical lawn surface from a stormwater perspective as the aggregate base will have a higher hydraulic conductivity rate than the lawn surface or the existing subgrade. Therefore stormwater infiltration and runoff will be dependent on the infiltration rate for the lawn surface, and will not be impacted by the aggregate base that supports the reinforced lawn. Any water that infiltrates through the lawn surface will infiltrate through the aggregate and into the subgrade as it would were a typical lawn. • The portion of the athletic fields directly above a gravel detention layer will be modeled 50% as lawn and 50% as impervious surface. The athletic fields include a minimum of 6-inches of topsoil above the gravel detention layer. The split between lawn surface and impervious surface is to acknowledge and model as accurately as possible the complexities of this system. The impervious half helps model the fact that the gravel detention layer acts effectively as an underdrain for the field which is only KPFF Consulting Engineers 6 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT separated from the surface by 6-inches of soil. The lawn half identifies the fact that the athletic fields are a grass surface and stormwater that falls on the field will not be immediately be routed to the detention system, and any stormwater that doesn't infiltrate into the soil will runoff the field with similar flow characteristics to a lawn, not an impervious surface. Figure 5-1: Historic Marsh Image The remainder of flow control will be provided on Civic Center Playfield by four separate gravel detention layer facilities. The facilities are located beneath the athletic courts in the northwest corner of the site and beneath the two athletic fields. Walls adjacent to gravel detention layers have been designed for full hydrostatic pressure and therefore have no wall drainage. The gravel detention layers are designed to have a stepped bottom to maximize the live storage while maintaining 6-inches of clearance from the assumed high groundwater table. Areas mitigated by each detention system are summarized in Table 5-3 below. See Appendix A for Gravel Detention Layer Extents. See Appendix B for Flow Control Calculations. RESUB Civic Center Playfield — Walkd`d abU 2021 CITYO DMONDS DEVELOP NT SERVICES DEPARTMENT Table 5-2: Civic Center Playfield Detention Area Summary . Detention SystemMFmperv.ous r►��reMitiga Area Mitigat Mitigated Gravel Detention Layer #1 � Gravel Detention Layer #2 7,405 SF (0.17 AC) 0 SF (0 AC) Gravel Detention Layer #3 9,148 SF (0.21 AC) 13,939 SF (0.32 AC) Gravel Detention Layer #4 28,750 SF (0.66 AC) 45,738 SF (1.05 AC) TOTAL 57,363 SF (1.32 AC) 59,677 SF (1.37 AC) 6. Construction Stormwater Pollution Prevention Plan (SWPPP) Stormwater Pollution Prevention Best Management Practices (BMPs) will be provided to minimize the risk of sediment -laden runoff entering the natural drainage systems. The following list of BMPs will be provided throughout construction and amended to meet site conditions, as necessary. See Appendix C for the SWPPP. • BMP C200: Interceptor Dike and Swale per plans • BMP C207: Check Dams per plans • BMP C220: Temporary Sediment Trap for Catch Basins per City of Edmonds Standard Detail ER-902 • BMP C233: Filter Fabric Fence per City of Edmonds Standard Detail ER-900 7. Special Reports and Studies Landau Associates prepared a Geotechnical Report for the project. The report is included in Appendix E. 8. Other Permits As the project is disturbing more than 1 acre, a National Pollutant Discharge Elimination System (NPDES) Permit is required. 9. Operation and Maintenance Manual An Operation and Maintenance Manual is included in Appendix D. KPFF Consulting Engineers 8 RESUB Mar 25 2021 CITV OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Appendix A Site Figures 1. Proposed Area Map 2. Downstream Analysis Map 3. Basin Map 4. Yost Park Mitigated Area Map 5. On -Site Conveyance Basin Map Civic Center Playfield — WalkEM&hU 2021 AppenadWo sERDCEs DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT EXISTING SITE AREA MAP LEGEND u HARD SURFACE LAWN/LANDSCAPE BASIN LAND USE AREAS LAND USE AREA (SF) AREA (AC) HARD SURFACE 86,282 1.98 LAWN/LANDSCAPE 266,609 6.12 TOTAL 352,891 8.10 o C T V O W N Llj Lu>H 2 W Q co = M 0 o v vo E 3� o p, N U Ln C L ej Y 03 om �c3 i N 3 I& - DEVELOPMENT SERVICES DEPARTMENT I — — — — — — — — — — — — — — — — — — — — I d I _ 9 — — — — — — — — — — — — — — — — — — — — I I I I �jI 11— _ - _ I I I -----—Mar 252021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT PROPOSED SITE AREA MAP LEGEND NEW/REPLACED HARD SURFACE LAWN/LANDSCAPE EXISTING HARD SURFACE TO REMAIN EDGE OF GRAVEL DETENTION LAYER BELOW FIELD BASIN LAND USE AREAS LAND USE AREA (SF) AREA (AC) NEW/REPLACED HARD 138,356 3.18 SURFACE LAWN MODELED AS 203,737 4.68 GRASS EXISTING HARD 10,789 0.25 SURFACE TO REMAIN TOTAL 352,882 8.10 FIELD OVER GRAVEL DETENTION LAYER MODELED AS 50% IMPERVIOUS AND 50% LAWN. THIS IS FOR MODELING PURPOSES ONLY. NOT FOR CONSTRUCTION. NORTH 0 50 100 200 1 inch = 100 feet T T T Cm a N T = U 2 c¢ O U W Co cc 0 w li g a o� w 0 U o� >z¢ U w Co Cd otZ0o 0 0 w M w u SYSTEM UPSIZES TO 18" - 0 a MILE DOWNSTREAM NORMAL CONVEYANCE PATH p q:l Cqb� SYSTEM UPSIZES TO 15" o ' 0 I - OElk [7 -4 �� ❑I }V/ I 0 Sp F j <,;� ❑I L =3i .dl 1 0 1% I_ I 1 111 D 8 RS❑ , T W'CASPE=RSm ST �� '- FINAL DISCHARGE TO Q -T-- SHELL CREEK cb *� JIFF pill — I• sr .I '� I � I �11�1�1 — SITE CONNECTION - 12" SYSTEM I_ I II '"-- SITE' 0 13 p - 'SS-��.• Mar 25 2021 1J� III � 1.-�-113 DOWNSTREAM ANALYSIS MAP LEGEND IN m m m m DOWNSTREAM FLOW PATH CITY OF EDMONDS GIS DATA NORTH (1 0 125 250 500 1 inch = 250 feet N Q H O 2 W Q Cocco 0 0 v N � (U O E a 3 ' c. t 1 �nj " 4 0 0 �c 3 Ln N DEVELOPMENT SERVICES DEPARTMENT iviar L5 zuzT CITY OF EDMONDS DEVELOPMENT SERVICES DRAINAGE BASIN MAP NOTES 1. ALL LAWN AND LANDSCAPE AREAS THAT ARE NOT DIRECTLY ABOVE GRAVEL DETENTION LAYERS WILL MEET THE REQUIREMENTS OF BMP T5.13: POST -CONSTRUCTION SOIL QUALITY AND DEPTH PER THE 2019 DOE SWMMWW. LEGEND APPROXIMATE LIMIT OF WORK DETENTION ONLY BASIN LINE WATER QUALITY ONLY BASIN LINE DETENTION AND WATER QUALITY BASIN LINE NEW AND REPLACED HARD SURFACE LAWN/LANDSCAPE MODELED AS 'TILL GRASS" LAWN/LANDSCAPE MODELED AS "TILL PASTURE" BYPASS POLLUTION GENERATING PERVIOUS SURFACE GRAVEL DETENTION AREA DRAINAGE BASIN AREAS IMPERVIOUS PERVIOUS TOTAL BASIN AREA (AC) AREA (AC) AREA (AC) BASIN NOTES t, 1) 0.28 0.00 0.28 GOES TO GRAVEL DETENTION LAYER J1. NO WQ TREATMENT REQURED. �� t, 1) 0.17 0.00 0.17 GOES TO GRAVEL DETENTION LAYER #2. NO WQ TREATMENT REQUIRED. 0.21 0.32 0.53 GOES TO GRAVEL DETENTION LAYER #3. WQ TREATMENT PROVIDED DOWNSTREAM OF DETENTION. ® 0.66 1.05 1.71 GOES TO GRAVEL DETENTION LAYER #4. WQ TREATMENT PROVIDED DOWNSTREAM OF DETENTION. t, �) 1.39 2.84 4.23 BYPASS ON -SITE DETENTION VIA TRADE WITH YOST PARK. GOES DIRECTLY WQ TREATMENT. © 0.45 0.48 0.93 BYPASS ON -SITE DETENTION VIA TRADE WITH YOST PARK. BYPASS WQ TREATMENT. TOTAL 3.16 4.69 7.84 0 50 100 200 1 inch = 100 feet V ru m ail Lu co w G 0 0 LID 1-4 ar vo E 0 Qa00 2 Ln a V1 N N �O �aj tN J w a w H Z w c� U > Z Q (> ui a o o oC� o W Co W Eq ww YOST PARK MITIGATED AREA MAP NOTES \ 1. IT IS ASSUMED ALL LANDCOVER WITHIN THE MITIGATED BASIN LINE IS PASTURE, GRASS, OR IMPERVIOUS. 2. IT IS ASSUMED THE POOL DRAINS TO SEWER AND IS NOT COUNTED FOR DETENTION CREDIT. LEGEND MITIGATED BASIN LINE MITIGATED IMPERVIOUS SURFACE MITIGATED PERVIOUS SURFACE POOL AREA (SEE NOTE 2) BASIN LAND USE AREAS LAND USE AREA (SF) AREA (AC) IMPERVIOUS 75,466 1.73 PERVIOUS 93,128 2.14 TOTAL 168,594 3.87 0 O Cu 60 E 0 N fV U >< 0w Ln a t ,y Y Y W v/i N o W LL d W W N U as NORTH v w 0 50 100 200 o a c R SUB Z=Z M r 25 2021 1 inch = 100 feet m m m 0 CITY OF EDMONDS inT m DEVELOPMENT SERVICES W @7 W Lo LEGEND ON -SITE CONVEYANCE BASIN MAP r CONVEYANCE BASIN LINE c$ TT i V IMPERVIOUS SURFACE Q Q " DRAINAGE BASIN AREAS BASIN IMPERVIOUS PERVIOUS TOTAL OOO23 ril /ylSPRAGUE ��kr.,J7 nFF----- .. . .............. ............................. o {.. < s .. asa pia Lp4 ............................... .. cHo or ixar �. GRAVEL DETENTION LAYER EXTENTS GRAVEL DETENTION LAYER AREAS .......................................................................... ............................................................................ .......................................................................... .::: } AYER::#1::.::.::.::::.....LAYER: #2::::::::::::LA�ER : #3 . . AREA (SF) DEPTH (FT) AREA (SF) DEPTH (FT) AREA (SF) DEPTH (FT) O552 3.5 4,590 3.0 — — O573 3.5 2,668 3.0 — — O4,854 2.5 11,533 1.5 2,313 1 O11,922 1.5 19,688 1.0 15,065 0.5 0 0 m J J rr LLI w O U Co CU rn NORTH � L 0 30 60 120 ®�Cd 1 inch = 60 feet 0 Lucwl:�w DEVELOPMENT SERVICES DEPARTMENT Appendix 6 Calculations 1. Conveyance Calculations 2. Pipe Buoyancy Calculations 3. Catch Basin Buoyancy Calculations 4. Water Quality Calculations 5. Detention Calculations Civic Center Playfield — WalkEMUhU 2021 Appenad.UP` ° sERD CEs DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT MGS FLOOD PROJECT REPORT Program Version: MGSFIood 4.50 Program License Number: 200410007 Project Simulation Performed on: 03/10/2020 12:58 PM Report Generation Date: 03/10/2020 12:58 PM Input File Name Project Name: Analysis Title: Comments: Conveyance Calculations.fld Edmonds Civic Playfield Conveyance Calculations PRECIPITATION INPUT Computational Time Step (Minutes): Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.378 0.276 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.378 0.276 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin Outwash Grass Impervious ------------------------- Subbasin Total Basin 18---------- ------- Area (Acres) 0.200 0.178 0.378 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin 1---------- ------- Area (Acres) Impervious 0.276 Subbasin Total 0.276 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Basin 18 56.504 Total: 56.504 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Basin 1 0.000 Total: $ 8 II Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Predeveloped: 0.358 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Basin 18 Scenario Postdeveloped Compliance Subbasin: Basin 1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------- 2-Year 8.103E-02 2-Year 0.122 5-Year 0.107 5-Year 0.166 10-Year 0.133 10-Year 0.203 25-Year 0.166 25-Year 0.257 Basin 1 50-Year 0.205 50-Year 0.318 100-Year 0.260 100-Year 0.403 200-Year 0.301 200-Year 0.467 500-Year 0.356 500-Year 0.551 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 316.0% FAIL Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 438.1% FAIL Maximum Excursion from Q2 to Q50 (Must be less than 10%): 99999.0% FAIL Percent Excursion from Q2 to Q50 (Must be less than 50%): 100.0% FAIL FLOW DURATION DESIGN CRITERIA: FAIL RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 6-inch PVC @ 0.5% Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.00500 ft/ft Normal Depth 0.50 ft Diameter 0.50 ft Discharge 0.52 ft3/s Results I Discharge 0.52 ft3/s > 0.26 ds OK Normal Depth 0.50 ft Flow Area 0.20 ft2 Wetted Perimeter 1.57 ft Hydraulic Radius 0.13 ft Top Width 0.00 ft Critical Depth 0.37 ft Percent Full 100.0 % Critical Slope 0.00636 ft/ft Velocity 2.63 ft/s Velocity Head 0.11 ft Specific Energy 0.61 ft Froude Number 0.00 Maximum Discharge 0.55 ft3/s Discharge Full 0.52 ft3/s Slope Full 0.00500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Bentley Systems, Inc. Haestad Methods SolReI*FitewMaster V8i (SELECTseries 1) [08.11.01.03] 12I5I2019 11:33:19 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 2 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 6-inch PVC @ 0.5% GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 0.50 ft Critical Depth 0.37 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00636 ft/ft Bentley Systems, Inc. Haestad Methods SolReI*FitewMaster V8i (SELECTseries 1) [08.11.01.03] 12I5I2019 11:33:19 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 2 of 2 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.50 Program License Number: 200410007 Project Simulation Performed on: 03/10/2020 10:38 AM Report Generation Date: 03/10/2020 10:38 AM Downstream Input File Name: Conveyance Check.fld Project Name: Edmonds Civic Playfield Analysis Title: 100% CD Detention Sizing Comments: PRECIPITATION INPUT Computational Time Step (Minutes): Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 8.100 8.100 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 8.100 8.100 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin Outwash Grass Impervious ------------------------- Subbasin Total Existing Civic ------ ------- Area (Acres) 6.120 1.980 8.100 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 5 ---------- Subbasin : Civic Detention Basin 1 -------Area (Acres) ------ Impervious 0.276 ---------------------------------------------- Subbasin Total 0.276 ---------- Subbasin : Civic Detention Basin 3 -------Area (Acres) ------ Outwash Pasture 0.094 Outwash Grass 0.429 Impervious 0.003 Subbasin Total 0.526 ---------- Subbasin : Civic Detention Basin 4 -------Area (Acres) ------ Outwash Pasture 0.461 Outwash Grass 1.194 Impervious 0.060 Subbasin Total 1.715 ---------- Subbasin : Civic Detention Basin 2 -------Area (Acres) ------ Impervious 0.174 ---------------------------------------------- Subbasin Total 0.174 ---------- Subbasin : Detention Bypass -------Area (Acres) Outwash Pasture 3.349 Outwash Grass 0.069 Impervious 1.991 Subbasin Total 5.409 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 Link Name: Downstream POC Link Type: Copy RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 5 Link Name: Civic Detention #1 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 75.08 0. 75.58 97. 76.08 997. 76.58 1896. 77.08 2796. 77.58 3696. 78.08 4596. 78.58 5496. 79.08 6396. 79.58 7295. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 78.58 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 75.08 Diameter (in) 0.50 Orientation : Horizontal Elbow : No Link Name: Downstream POC Link Type: Copy Downstream Link: None RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Link Name: Civic Detention #3 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 81.17 0. 81.67 850. 82.17 1699. 82.67 4567. 83.17 7839. 83.67 11112. 84.17 14384. 84.67 17657. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 83.67 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 81.17 Diameter (in) 1.00 Orientation : Horizontal Elbow : No Link Name: Civic Detention #4 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 82.10 0. 82.60 2086. 83.10 7618. 83.60 15786. 84.10 23954. 84.60 32123. RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 83.60 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 82.10 Diameter (in) 1.00 Orientation : Horizontal Elbow : No Link Name: Civic Detention #2 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 75.64 0. 76.14 100. 76.64 668. 77.14 1235. 77.64 1802. 78.14 2369. 78.64 2936. 79.14 3503. 79.64 4071. 80.14 4638. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 79.14 ft RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 75.64 Diameter (in) 0.50 Orientation : Horizontal Elbow : No **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 5 Number of Links: 5 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Existing Civic 1729.027 Link: Downstream POC 0.000 Total: 1729.027 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Civic Detention Basi 0.000 Subbasin: Civic Detention Basi 148.208 Subbasin: Civic Detention Basi 469.776 Subbasin: Civic Detention Basi 0.000 Subbasin: Detention Bypass 981.665 Link: Civic Detention #1 Not Computed Link: Downstream POC 0.000 Link: Civic Detention #3 Not Computed Link: Civic Detention #4 Not Computed Link: Civic Detention #2 Not Computed Total: 1599.648 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 10.943 ac-ft/year, Post Developed: 10.124 ac-ft/year RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: Downstream POC ********** Infiltration/Filtration Statistics -------------------- Inflow Volume (ac-ft): 784.69 Inflow Volume Including PPT-Evap (ac-ft): 784.69 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 784.69 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 5 ********** Link: Downstream POC ********** Infiltration/Filtration Statistics -------------------- Inflow Volume (ac-ft): 990.70 Inflow Volume Including PPT-Evap (ac-ft): 990.70 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 990.70 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: Downstream POC Scenario Postdeveloped Compliance Link: Downstream POC *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ------------------------------------------------------------------------------------------------------------ 2-Year 0.917 2-Year 0.916 5-Year 1.226 5-Year 1.214 10-Year 1.530 10-Year 1.483 25-Year 2.093 25-Year 1.870 50-Year 2.364 50-Year 2.306 100-Year 2.890 100-Year 2.920 200-Year 3.350 200-Year 3.380 500-Year 3.960 500-Year 3.990 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT (1) DESIGN YEAR STORM Appendix B Overtop Calculation (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (18) (19) (20) (21) (41) (42) (45) (47) (50) (51) (52) (55) (56) (72A) (75) (76) UP (YEAR) (#) PIPE WALL INC MANNINGS INPUT PAVEMENT THICKN JUNCT CATCH CATCH FULL FLOW CRIT TAIL TAIL FRICT ENTR EXIT BEND HEADW OVERTOP STRUCTURE RIM THICKNESS DIAM ESS INVERT ANGL n L S FLOW PVMT GRASS AREA TC FLOW CAPACITY VEL DEPTH WATER WATER LOSS HGL LOSS LOSS LOSS ATER CHECK DOWN UP DOWN UP DOWN UP DOWN UP UP UP UP UP UP DOWN DOWN UP UP DOWN UP UP UP (#) (FT) (FT) (IN) (IN) (IN) (IN) (FT) (FT) (DEG) (FT) % (CFS) (AC) (AC) (AC) (MIN) (CFS) (CFS) (FPS) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) 100 SDCB #25 SDCB #17 40 80.29 79.69 0.00 0.00 6 0.28 76.79 76.19 0.00 0.011 46 1.31% 0.00 0.067 0.033 0.100 5.00 0.27 0.76 1.37 0.26 76.71 76.71 0.08 77.29 0.01 0.03 0.00 77.33 OK 100 SDCB #7 SDCO #28 82.36 83.84 0.00 0.00 8 0.32 78.89 78.23 0.00 0.011 66 1.00% 0.00 0.147 0.167 0.314 5.00 0.70 1.43 2.00 0.39 78.76 0.16 79.56 0.03 0.06 0.00 79.65 OK 100 SDCO #28 SDCB #31 83.84 83.85 0.00 4.00 8 0.32 78.23 77.96 0.00 0.011 27 1.00% 0.00 0.000 0.027 0.027 5.00 0.71 1.43 2.03 0.40 78.49 0.07 78.90 0.03 0.06 0.00 78.93 OK 100 SDCB #31 SDCO #30 83.85 84.01 4.00 0.00 8 0.32 77.96 77.37 0.00 0.011 59 1.00% 0.00 0.000 0.000 0.000 5.00 0.70 1.43 2.00 0.39 78.04 0.14 78.63 0.03 0.06 0.00 78.66 OK 100 SDCO #30 SDCO #39 84.01 83.15 0.00 0.00 8 0.32 77.37 77.30 0.00 0.011 7 1 1.00% 0.00 0.000 0.031 0.031 5.00 1 0.73 1.43 2.10 0.40 77.84 0.02 78.04 0.03 0.07 0.00 78.14 OK 100 SDCO #39 SDCB #15 83.15 83.02 0.00 0.00 8 0.32 1 77.30 76.49 0.00 0.011 81 1.00% 0.00 0.050 0.000 0.050 5.00 0.83 1.43 2.37 0.43 77.66 0.27 77.97 0.04 0.09 0.00 78.04 OK 100 SDCB #15 SDCB #8 83.02 82.45 0.00 0.00 8 0.32 76.49 76.16 0.00 0.011 33 1.00% 0.00 0.178 0.200 0.378 5.00 1.57 1.42 4.51 0.58 76.78 0.40 77.19 0.16 0.32 0.00 77.66 OK 100 SDCB #8 SDCB #17 82.45 79.69 0.00 0.00 12 0.41 74.69 74.51 0.00 0.011 36 0.50% 0.33 0.000 0.000 0.000 5.00 1.88 2.97 2.39 0.58 76.50 0.07 76.58 0.04 0.09 0.01 76.71 OK 100 SDCB #17 SDCB #19 79.69 79.45 0.00 0.00 12 0.41 74.51 74.10 0.00 0.011 80 0.51% 0.27 0.071 0.053 0.124 5.00 2.40 3.01 3.06 0.66 76.10 0.26 76.36 0.07 0.14 0.00 76.50 OK 100 SDCB #19 SF0818 11 79.45 79.92 0.00 6.00 12 0.41 74.10 74.06 1 0.00 0.011 9 0.46% 1 0.00 0.050 1 0.101 0.151 1 5.00 2.60 2.85 3.31 0.69 75.96 75.96 0.03 75.99 0.08 0.17 0.00 76.10 OK 100 SDCB #1 SDCB #2 1 78.44 78.75 0.00 0.00 6 1 0.28 75.94 75.73 0.00 0.011 21 1.01% 0.00 0.000 0.138 0.138 5.00 0.16 0.67 1 0.80 0.20 1 76.52 0.01 76.54 0.00 0.01 0.00 76.55 OK 100 SDCB #2 SDCB #3 78.75 80.12 0.00 0.00 8 0.32 75.69 75.06 94.43 0.011 63 1.00% 0.00 0.075 0.206 0.281 5.00 0.64 1.43 1.84 0.38 76.31 0.13 76.44 0.03 0.05 0.01 76.52 OK 100 SDCB #3 SF0818 80.12 79.92 0.00 6.00 8 0.32 75.06 74.41 90.00 0.011 128 0.51% 0.00 0.000 0.000 0.000 5.00 0.64 1.02 1.84 0.38 75.96 75.96 0.26 76.22 0.03 0.05 0.07 76.31 OK 100 SDCB #26 SDCB #27 79.86 80.58 0.00 0.00 8 0.32 76.86 76.19 0.00 0.011 67 1.00% 0.00 0.120 0.181 0.301 5.00 0.62 1.43 1.78 0.37 76.93 0.13 77.53 0.02 0.05 0.00 77.60 OK 100 SDCB #27 SDCB #28 80.58 80.42 0.00 0.00 8 0.32 76.19 75.72 34.89 0.011 47 1.01% 0.00 0.037 0.011 0.048 5.00 0.74 1.43 2.12 0.41 76.69 0.12 76.86 0.03 0.07 0.01 76.93 OK 100 SDCB #28 SDCB #29 1 80.42 81.01 0.00 6.00 8 0.32 75.64 75.41 28.78 0.011 23 0.99% 0.00 0.053 0.115 0.168 5.00 1.02 1 1.42 2.93 0.48 76.42 76.42 0.12 76.54 0.07 0.13 0.01 76.69 OK 100 SDCB #21 SDCB #9 84.48 85.00 0.00 0.00 6 0.28 81.00 1 80.84 0.00 0.011 16 1 1.03% 0.00 0.070 0.214 0.284 5.00 0.49 0.67 2.47 0.36 81.43 0.08 81.51 0.05 0.09 0.00 81.65 OK 100 SDCB #9 SDCB #10 85.00 86.52 0.00 0.00 12 0.41 80.48 79.62 1 0.00 0.011 85 1.01% 0.10 0.038 0.070 0.108 5.00 0.79 4.22 1.01 0.37 80.63 0.03 81.48 0.01 0.02 0.00 81.43 OK 100 SDCB #10 SDCB #11 86.52 86.73 0.00 6.00 12 0.41 79.62 78.77 0.00 0.011 85 1.00% 0.00 0.000 0.000 0.000 5.00 0.79 4.20 1.01 0.37 1 79.80 0.03 80.62 0.01 0.02 0.00 80.63 OK 100 SDCB #11 SDCB #12 86.73 85.10 6.00 6.00 12 0.41 78.77 77.68 90.00 1 0.011 109 1.00% 0.00 0.000 0.000 1 0.000 5.00 0.79 4.22 1.01 0.37 78.75 0.04 79.77 0.01 0.02 0.02 79.80 OK 100 SDCB #12 SDCB #29 85.10 81.01 6.00 6.00 12 0.41 77.68 75.23 0.00 0.011 245 1.00% 0.71 0.000 0.000 0.000 5.00 1.45 4.21 1.84 0.51 76.42 0.29 78.68 0.03 0.05 0.00 78.75 OK 100 SDCB #29 SF0818 IF 81.01 79.92 6.00 6.00 12 0.41 75.23 74.08 0.00 0.011 77 1.50% 1.02 0.000 0.000 0.000 5.00 2.43 5.16 3.10 0.67 75.96 0.26 76.23 0.07 0.15 0.00 76.42 OK 100 SF0818 SDCB #18 IF79.92 78.85 6.00 3.00 12 0.41 72.02 71.71 0.00 0.011 16 2.00% 3.24 0.000 0.000 0.000 5.00 5.66 5.95 7.21 0.95 74.46 0.28 74.74 0.40 0.81 0.00 75.96 OK 100 SDCB #18 SDCB #13 78.85 79.26 3.00 6.00 12 0.41 71.71 70.99 0.00 0.011 36 2.00% 0.00 0.032 0.018 0.050 5.00 5.77 5.96 7.35 0.95 73.32 0.68 74.00 0.42 0.84 0.01 74.46 OK 100 SDCB #13 SDCB #14 79.26 75.97 6.00 1 5.50 12 0.41 70.99 69.48 26.45 0.011 76 2.00% 0.09 0.000 0.000 0.000 5.00 5.86 5.95 7.46 0.95 1 71.24 1.46 72.71 0.43 0.86 0.15 73.32 OK 100 SDCB #14 SDCB #33 75.97 75.62 5.50 6.00 12 0.41 69.48 69.22 0.00 0.011 13 2.00% 0.01 0.000 0.000 0.000 5.00 5.86 5.95 7.46 0.95 70.20 0.25 70.48 0.43 0.86 0.02 71.51 OK 100 SDCB #33 OUTFALL 75.62 73.45 6.00 6.00 1 12 0.41 69.22 67.03 0.00 0.011 110 2.00% 0.00 0.000 0.000 0.000 5.00 5.86 5.95 7.46 1 0.95 67.65 67.65 2.12 70.22 0.43 0.86 0.02 71.24 OK 100 SDCB #23 SDCB #24 82.37 79.94 0.00 0.00 6 0.28 78.87 76.44 0.00 0.011 70 3.48% 0.00 0.061 0.613 0.674 5.00 0.91 1.24 4.62 0.46 77.47 1.31 79.37 0.17 0.33 0.00 80.05 OK 100 SDCB #24 SDCB #29 79.94 81.01 0.00 6.00 8 0.32 76.44 76.30 94.30 0.011 14 0.98% 0.00 0.064 0.041 0.105 5.00 1.15 1.42 3.30 0.51 76.42 76.42 0.09 77.11 0.08 0.17 0.44 77.47 OK 100 SDCB #16 SDCB #8 40 78.48 82.45 0.00 1 0.00 6 0.28 75.53 74.93 0.00 0.011 120 0.50% 0.00 0.080 0.043 1 0.123 5.00 0.33 0.47 1.66 0.29 76.71 76.71 0.29 77.00 0.02 0.04 0.00 77.07 OK 100 SDCB #22 SDCB #12 82.25 85.10 0.00 6.00 8 0.32 79.04 77.68 0.00 0.011 136 1.00% 0.00 0.092 0.342 0.434 5.00 0.71 1.43 2.02 0.40 78.75 78.75 0.33 79.71 0.03 0.06 0.00 79.80 OK 100 SDCB #20 DIET #4 85.87 84.69 0.00 0.00 8 0.28 83.74 83.10 0.00 0.012 65 0.99% 0.00 0.026 0.040 0.066 5.00 0.14 1.30 0.39 0.17 1 82.33 82.33 0.01 84.41 0.00 0.00 0.00 84.41 OK 100 SDCB #4 SDCO #38 82.87 83.05 4.00 1 4.00 6 0.28 80.67 80.60 0.00 0.011 13 0.53% 0.00 0.117 0.000 1 0.117 5.00 0.40 0.48 2.06 0.32 81.32 0.05 81.37 0.03 0.07 0.00 81.47 OK 100 SDCO #38 TD POC 83.05 82.96 4.00 5.50 1 8 0.32 80.60 80.37 90.00 0.011 46 0.50% 0.00 0.000 0.000 0.000 5.00 0.40 1.01 1.16 0.30 81.08 0.04 81.27 0.01 0.02 0.09 81.32 OK 100 TD POC SDCO #33 83.28 83.31 5.50 5.50 8 0.32 80.37 80.15 0.00 0.011 43 0.51% 0.00 0.057 0.000 0.057 5.00 0.58 1.02 1.66 0.36 80.90 1 0.07 1 81.04 0.02 0.04 0.00 81.08 OK 100 SDCO #33 SDCB #6 83.31 83.25 5.50 5.50 8 0.32 80.15 79.70 90.00 0.011 91 0.50% 0.00 0.000 0.000 0.000 5.00 0.58 1.01 1.66 0.36 80.45 0.15 80.82 0.02 0.04 0.06 80.90 OK 100 SDCB #6 DIET #2 1 83.25 79.72 5.50 0.00 8 0.32 79.70 76.55 90.00 0.012 210 1.50% 0.00 0.000 0.000 0.000 5.00 0.58 1.60 1.66 0.36 1 77.54 77.54 0.41 80.37 0.02 0.04 0.06 80.45 OK RESUB Mar 25 2021 Z:\1700001-1700999\1700910 Edmonds City Center Playfield\RF Fs `�i 11MENTS\Storm Drainage\06 - Backwater Calculations\ECCP 100yr - Backwater CLEAN.Asm DEPARTMENT EDMONDS CIVIC CENTER PLAYFIELD - PIPE BUOYANCY CALCULATIONS The vertical hydrostatic upliftforce, U, due to the water table can easily be calculated from Equation 1 below: R , U =-D"&, (1) 4 where U = IWlinearft of pipe D = 0_D. of the pipe in question, ft_ S,,, = unit weight of water = 62.4 Ib/ft3 HYDROSTATIC UPLIFT FORCE Vertical Hydrostatic Vertical Hydrostatic Unit Weight of Water, O.D. of Pipe , D Uplift Force Fully Uplift Force Half Pipe Type yw (Ib/ft3) (ft) Submerged Pipe, U Submerged Pipe, U (Ib/LF of pipe) (Ib/LF of pipe) 6" PVC 62.4 0.55 24.8 7.4 8" PVC 62.4 0.72 25.4 12.7 12" PVC 62.4 1.06 55.1 27.5 This hydrostatic uplift force must be balanced by soil overburden and the weight of the pipe in order to ensure that the pipe will not float. Soil leads experienced by a pipe at varying water table depths (W,a) can be calculated from Equation 2. Figure 1 illustrates each of the three cases seen in field installations where buoyancy becomes a concern, and also clarifies all of the parameters contained within Equation 2_ W, j = 8�^ND + (5� S„,)(H�+ 0.1073D)D (2) where W_gI = weight of soil overburden, 16ilinear ft of pipe N,y = dry unit weight of the soil, lb/113 H,,,y = depth of dry soil, ft. Ha ,, = depth of submerged soil over top of pipe, ft_ S,ar = saturated unit weight of the soil, IbW b5 t - bw = submerged unit weight of the soil, Ib/ft3 Soil Type (I WO) 7sat (Ib/0) Sand. loose and uniform 90 113 Sand, dense and uniform 109 130 sand. loose and well graded 99 124 Sand.dense and well graded 116 135 glac ial clay, soft 76 110 glacial clay, stiff 106 125 WEIGHT OF SOIL OVERBURDEN Pipe Dry Unit Wei f Soil, O.D. ofPipe,D Depth of Dry Saturated Unit Unit Weight Depth of Submerged Soil Weight of Soil Scenario y,ry (Ib/ft3) Weight o Soil, H°ry (fit) Weight of Soil, ysa, of Water, yw Over Top of Pipe, H,,,b Overburden, W,.I (ft) (Ib/ft3) (lb/ft') (ft) (Ib/LF of pipe) 1 76 1.45 0.55 110 62.4 0 62.2 2 76 1.45 0.55 110 62.4 0 62.2 3 76 1.28 0.72 110 62.4 0 72.7 4 76 1.28 0.72 110 62.4 0 72.7 5 76 0.94 1.06 110 62.4 0 81.5 6 76 0.94 1.06 110 62.4 0 81.5 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT (a) Water table at pipe crown (b) Water table exceeds (c) Water table is at pipe crown elevation ground surface The minimum depth of cover (H) required to resist uplift can be calculated by equating the sum of the downward forces to the sum of the upward or buoyant forces_ While there are varying methods to account for soil load distribution on the pipe, for conservative minimum cover requirements, the soil load is assumed to be the soil column directly above the outside diameter of the pipe as illustrated in Figure 2(a)_ Therefore. minimum cover is calculated using Equations 3 and 4 below: t3 sW'—+W" (3) where Wm- = weight of the pipe, Ibllinear ft of pipe H = H�, + Hg, (4) Figure 2 Forces Affecting Flotation 112 (H—) (a) Sail Column Loading Conditions (b) Prism Loading Conditions WEIGHT OF PIPE Weight of Pipe, Wpipe Pipe Type (lb/LF of pipe) 6" PVC 3.53 8" PVC 5.39 12" PVC 10.01 Vertical Hydrostatic Sum of Downward Pipe Scenario Uplift Force of Pipe, U Forces, Wsoil + Wpipe Factor of Safety (lb/LF of pipe) (lb/LF of pipe) 1 7.4 5 65.7 8.9 2 7.4 <_ 65.7 8.9 3 14.8 5 76.2 5.1 4 14.8 <_ 76.2 5.1 5 14.8 5 85.0 5.7 6 14.8 <_ 85.0 5.7 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT PIPE SCENARIOS Scenario # Pipe O.D. (ft) Pipe Material Submerged State Pipe IE Depth (ft) Depth of Soil Above Crown (ft) Depth of Groundwater Above Crown (ft) Depth of Dry Soil Above Crown (ft) 1 0.55 PVC Half 2 1.45 0 1.45 2 0.55 PVC Full 2 1.45 0 1.45 3 0.72 PVC Half 2 1.28 0 1.28 4 0.72 PVC Full 2 1.28 0 1.28 5 1.06 PVC Half 2 0.94 0 0.94 6 1.06 PVC Full 2 0.94 0 0.94 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT EDMONDS CIVIC CENTER PLAYFIELD - SDCB TYPE 1 BUOYANCY CALCULATIONS STRUCTURE PARAMETERS Unit Inside Inside Dim. Inside Bottom of Wall Thickness of Outside Dim. Outside Dim. 2 Weight of Dim. 1 of 2 of Area of Thickness Outside Area Precast Thickness, Bottom 1 of of Structure, Rim Elev Lowest IE Elev GW Elev Riser Thickness Structure # Concrete, Structure, Structure, Structure, of Grate, is of Structure, Knockout tW Slab, tb Structure, D3 Da (ft) (ft) (ft) (in) Ai (ft) z (ft) Elev (lb/ft3) (ft) (ft) (ft') (ft) (ft) (ft) (ft) (ft) SDCB #1 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 78.44 75.94 76.28 4 75.86 SDCB #2 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 78.75 75.69 76.02 12 75.50 SDCB #4 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.98 80.67 80.57 6 80.23 SDCB #5 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.95 79.56 80.51 24 78.70 SDCB #7 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.34 78.89 81.49 16 78.76 SDCB #15 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 83.02 79.52 80.52 16 79.44 SDCB #16 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 78.48 75.53 76.94 4 75.90 SDCB #17 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 79.69 76.19 78.39 16 76.11 SDCB #18 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 78.96 75.46 76.96 16 75.38 SDCB #19 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 79.45 75.95 76.87 16 75.87 SDCB #20 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 85.87 83.74 84.35 12 82.62 SDCB #21 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 84.48 81 81.39 16 80.90 SDCB #22 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.25 79.04 81.31 12 79.00 SDCB #23 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.37 78.87 78.95 16 78.79 SDCB #24 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 79.94 76.44 77.5 16 76.36 SDCB #25 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 80.29 76.79 78.82 16 76.71 SDCB #26 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 79.86 76.86 79.2 12 76.61 SDCB #27 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 80.58 76.19 77.58 26 76.17 SDCB #28 150 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 80.42 75.64 77.26 32 75.51 SDCB #30 151 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.74 80.11 81.06 6 79.99 SDCB #34 152 2.17 1.83 3.97 0.33 0.33 0.33 2.83 2.50 7.08 82.96 79.76 80.51 12 79.71 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT FIND WEIGHT OF STRUCTURE SLIDING RESISTANCE BUOYANT FORCE FACTOR OF SAFETY Distance Total Between Distance Shearing Surface Sliding Weight of Weight of Height of Weight of Structure GW and Between Resistance Resistance Unit Weight Upward Buoyant Structure # Fill, H wall, Base, W top Weight, Bottom o Rim and o Soil to (downward), ( ) o Water, yW Force, B Factor of Safety, FS WwaTo Wb) (unitless) (ft) (Ib) W t Structure GW H � F� Wall F � s R i sliding ( 3) Ib/ft Ib ( ) (1b) (Ib) (Ib) (Ib) Hcw (ft) (Ib/ft) (Ib) (ft) SDCB #1 4.33 1,710 354 0 2,064 2.17 2.16 196 2,088 62.4 959 4.3 SDCB #2 5.00 2,021 354 0 2,375 2.27 2.73 268 2,856 62.4 1,002 5.2 SDCB #4 4.50 1,787 354 0 2,142 2.09 2.41 216 2,300 62.4 922 4.8 SDCB #5 6.00 2,487 354 0 2,842 3.56 2.44 353 3,766 62.4 1,572 4.2 SDCB #7 5.33 2,176 354 0 2,530 4.48 0.85 216 2,309 62.4 1,980 2.4 SDCB #15 5.33 2,176 354 0 2,530 2.83 2.5 291 3,107 62.4 1,251 4.5 SDCB #16 4.33 1,710 354 0 2,064 2.79 1.54 177 1,885 62.4 1,233 3.2 SDCB #17 5.33 2,176 354 0 2,530 4.03 1.3 240 2,562 62.4 1,781 2.9 SDCB #18 5.33 2,176 354 0 2,530 3.33 2 272 2,903 62.4 1,472 3.7 SDCB #19 5.33 2,176 354 0 2,530 2.75 2.58 294 3,136 62.4 1,216 4.7 SDCB #20 5.00 2,021 354 0 2,375 3.48 1.52 225 2,396 62.4 1,537 3.1 SDCB #21 5.33 2,176 354 0 2,530 2.24 3.09 310 3,305 62.4 990 5.9 SDCB #22 5.00 2,021 354 0 2,375 4.06 0.94 198 2,107 62.4 1,793 2.5 SDCB #23 5.33 2,176 354 0 2,530 1.91 3.42 318 3,395 62.4 844 7.0 SDCB #24 5.33 2,176 354 0 2,530 2.89 2.44 289 3,084 62.4 1,277 4.4 SDCB #25 5.33 2,176 354 0 2,530 3.86 1.47 249 2,651 62.4 1,706 3.0 SDCB #26 5.00 2,021 354 0 2,375 4.34 0.66 183 1,952 63.4 1,948 2.2 SDCB #27 6.16 2,565 354 0 2,919 3.16 3 394 4,201 64.4 1,443 4.9 SDCB #28 6.66 2,798 354 0 3,153 3.50 3.16 457 4,872 65.4 1,623 4.9 SDCB #30 4.50 1,799 357 1 2,157 2.82 1.68 193 2,063 66.4 1,325 3.2 SDCB #34 5.00 2,048 359 2 2,408 2.55 2.45 259 2,767 1 67.4 1,216 4.3 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT EDMONDS CIVIC CENTER PLAYFIELD - SDCB TYPE 2 BUOYANCY CALCULATIONS STRUCTURE PROPERTIES Inside Outside Unit Diameter Wall Thickness Thickness Diameter of Diameter of Weight of of Thickness, of Bottom of Top Rim Elev Lowest IE Elev Sump Depth GW Elev Structure # Cover D ` Structure Concrete, Structure, tW Slab, tb Slab, is (ft) (ft) (ft) (ft) Yc (Ib/ft3) Di (ft) (ft) (ft) (ft) Bd (ft) (ft) SDCB #3 150 4 0.33 0.5 0.5 2 4.66 80 75.06 2 75.35 SDCB #6 150 4 0.33 0.5 0.5 2 4.66 83.25 79.7 2 80.71 SDCB #8 150 4 0.33 0.5 0.5 2 4.66 82.38 74.69 2 81.01 SDCB #9 150 4 0.33 0.5 0.5 2 4.66 85 80.48 2 81.44 SDCB #10 150 4 0.33 0.5 0.5 2 4.66 86.44 79.62 2 82.3 SDCB #11 150 4 0.33 0.5 0.5 2 4.66 86.73 78.77 2 82.89 SDCB #12 150 4 0.33 0.5 0.5 2 4.66 85.1 77.68 2 81.69 SDCB #13 150 4 0.33 0.5 0.5 2 4.66 79.26 70.99 2 77.04 SDCB #14 150 4 0.33 0.5 0.5 2 4.66 75.97 69.48 2 76.87 SDCB #29 150 4 0.33 0.5 0.5 2 4.66 81.01 75.23 2 77.44 SDCB #31 150 4 0.33 0.5 0.5 2 4.66 83.85 77.96 2 81.21 SDCB #32 150 4 0.33 0.5 0.5 2 4.66 86.83 81.7 2 81.65 SDCB #33 150 4 0.33 0.5 0.5 2 4.66 75.62 69.22 2 73.63 FCMH #1 150 4 0.33 0.5 0.5 2 4.66 79.63 75.08 2 76.73 FCMH #2 150 4 0.33 0.5 0.5 2 4.66 79.72 75.64 2 76.99 FCMH #3 150 4 0.33 0.5 0.5 2 4.66 84.43 81.17 2 81.7 FCMH #4 150 4 0.33 0.5 0.5 2 4.66 84.69 81.14 2 81.57 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT FIND WEIGHT OF STRUCTURE SLIDING RESISTANCE BUOYANT FORCE FACTOR OF SAFETY Distance Total Between Distance Shearing Surface Sliding Height of Weight of Weight of Weight of Structure GW and Between Resistance Resistance Unit Weight Upward Buoyant Structure # Fill, H Wall, Base, Top, Wtop Weight, Bottom of Rim and of Soil to (downward), of Water, Yw Force, B Factor of Safety, FS (ft) Wwalls Wbase (Ib) Wt Structure, GW, HFG Wall, Fs Rsliding (Ib/ft3) (Ib) (unitless) (Ib) (Ib) HGw (ft) (Ib/ft) (Ib) (ft) SDCB #3 7.44 4,336 1,279 1,044 6,659 2.79 4.65 616 9,018 62.4 2,969 5.3 SDCB #6 6.05 3,400 1,279 1,044 5,723 3.51 2.54 363 5,312 62.4 3,736 3.0 SDCB #8 10.19 6,188 1,279 1,044 8,511 8.82 1.37 764 11,181 62.4 9,387 2.1 SDCB #9 7.02 4,054 1,279 1,044 6,376 3.46 3.56 517 7,571 62.4 3,682 3.8 SDCB #10 9.32 5,602 1,279 1,044 7,925 5.18 4.14 876 12,824 62.4 5,513 3.8 SDCB #11 10.46 6,370 1,279 1,044 8,693 6.62 3.84 1,041 15,243 62.4 7,045 3.4 SDCB #12 9.92 6,006 1,279 1,044 8,329 6.51 3.41 918 13,441 62.4 6,928 3.1 SDCB #13 10.77 6,579 1,279 1,044 8,901 10.77 2.22 1,306 19,116 62.4 11,462 2.4 SDCB #14 8.99 5,380 1,279 1,044 7,703 8.99 0 469 6,863 63.4 9,721 1.5 SDCB #29 8.28 4,902 1,279 1,044 7,225 4.71 3.57 685 10,031 64.4 5,173 3.3 SDCB #31 8.39 4,976 1,279 1,044 7,299 5.75 2.64 640 9,365 65.4 6,414 2.6 SDCB #32 7.63 4,464 1,279 1,044 6,787 2.45 5.18 661 9,683 66.4 2,775 5.9 SDCB #33 8.9 5,319 1,279 1,044 7,642 6.91 1.99 654 9,581 65.4 7,708 2.2 FCMH #1 7.05 4,074 1,279 1,044 6,396 4.15 2.9 490 7,168 62.4 4,417 3.1 FCMH #2 6.58 3,757 1,279 1,044 6,080 3.85 2.73 428 6,261 62.4 4,097 3.0 FCMH #3 5.76 3,205 1,279 1,044 5,528 3.03 2.73 341 4,995 62.4 3,225 3.3 FCMH #4 6.05 3,400 1,279 1,044 5,723 2.93 3.12 386 5,651 62.4 3,118 3.6 Stormfilter Vault 1.5 NA NA NA 79,230* 5.01 3.46 705 39,495 62.4 53,459 2.2 * Stormfilter vault weight per Contech + 1.5' dry soil weight above vault. EXTENDED BASE STRUCTURE SLIDING RESISTANCE BUOYANT FORCE FACTOR OF SAFETY Diameter Thickness Unit Height of Weight of Shearing Surface Sliding of Base, Of Weight of Fill of Base, Weight of Weight of Weight of Total Weight, Resistance Resistance Upward Buoyant Factor of Safety, FS Structure # Db Extended Dry Soil, Xs Extended Wbase Soil, Wsoil Top, Wtop Walls, Wwalls Wtotal of soil to (downward) , Force, B (unitless ) (ft) Base,tb(ext) 3 (Ib/ft) Base, Hz (Ib) (Ib) (Ib) (Ib) (Ib) Wall, Fsb Rsliding (Ib) (ft) (ft) (Ib/ft) (Ib) SDCB #14 6 0.5 58 0.5 2,121 5,524 1,044 6,579 15,267 703 10,294 11,812 2.2 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.50 Program License Number: 200410007 Project Simulation Performed on: 08/28/2020 2:00 PM Report Generation Date: 08/28/2020 2:01 PM Input File Name Project Name: Analysis Title: Comments: 100% CD WQ Sizing.fld Edmonds Civic Playfield 100% WQ Sizing Computational Time Step (Minutes): PRECIPITATION INPUT 15 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.000 6.956 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.000 6.956 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin ---------- ------- Area (Acres) Impervious 1.000 Subbasin Total 1.000 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 ---------- Subbasin : Civic Detention Basin 3 -------Area (Acres) ------ Outwash Pasture 0.094 Outwash Grass 0.429 Impervious 0.003 Subbasin Total 0.526 ---------- Subbasin : Civic Detention Basin 4 -------Area (Acres) ------ Outwash Pasture 0.460 Outwash Grass 1.194 Impervious 0.060 Subbasin Total 1.714 ---------- Subbasin: WQ Only Basin 5 - -------Area (Acres) Outwash Pasture 2.773 Outwash Grass 0.069 Impervious 1.394 Subbasin Total 4.236 ---------- Subbasin : Bypass Basin 6 --- -------Area (Acres) Outwash Pasture 0.480 Subbasin Total 0.480 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 3 Link Name: Downstream POC Link Type: Copy Downstream Link: None RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Link Name: Civic Detention #3 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 81.17 0. 81.67 850. 82.17 1699. 82.67 4567. 83.17 7839. 83.67 11112. 84.17 14384. 84.67 17657. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 83.67 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 81.17 Diameter (in) 0.50 Orientation : Horizontal Elbow : No Link Name: Civic Detention #4 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 82.10 0. 82.60 2086. 83.10 7618. 83.60 15786. 84.10 23954. 84.60 32123. RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 83.60 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 82.10 Diameter (in) 0.50 Orientation : Horizontal Elbow : No **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 Number of Links: 3 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Basin Total: Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Civic Detention Basi 148.625 Subbasin: Civic Detention Basi 470.796 Subbasin: WQ Only Basin 5 818.286 Subbasin: Bypass Basin 6 138.259 Link: Downstream POC 0.000 Link: Civic Detention #3 Not Computed RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Link: Civic Detention #4 Not Computed Total: 1575.966 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 9.974 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 3 ********** Link: Downstream POC Infiltration/Filtration Statistics -------------------- Inflow Volume (ac-ft): 576.40 Inflow Volume Including PPT-Evap (ac-ft): 576.40 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 576.40 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Basin Scenario Postdeveloped Compliance Link: Downstream POC *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position ********** Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.354 2-Year 0.498 223.5 gpm 5-Year 0.471 5-Year 0.659 10-Year 0.557 10-Year 0.777 25-Year 0.668 25-Year 0.934 50-Year 0.857 50-Year 1.196 100-Year 1.021 100-Year 1.425 200-Year 1.097 200-Year 1.534 500-Year 1.199 500-Year 1.679 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT WASH IN G T 0 N STATE 0 EPAGTME NT OF ECOLOGY April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) AND PHOSPHORUS TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter® with PhosphoSorb® media Ecology's Decision: 1. Based on Contech Engineered Solutions application, Ecology hereby issues the following use level designation for the Stormwater Management StormFilter® using PhosphoSorb® media cartridges: General Use Level Designation (GULD) for Basic Treatment (total suspended solids) and for Phosphorus (total phosphorus) treatment. o Sized at a hydraulic loading rate of no greater than 1.67 gallon per minute (gpm) per square foot (sq ft.) of media surface, per Table 1. o Using Contech's PhosphoSorb media. Specifications for the media shall match the specifications provided by the manufacturer and approved by Ecology. Table 1. StormFilter cartridge design flow rates for 18-inch diameter cartridges with PhosphoSorb media operating at 1.67 gpm/sq ft. Effective cartridge height (in) Cartridge flow rate (gpm/cartridge) 12 8.35 18 12.53 27 18.79 223.5 gpm/8.35 gpm = 27 cartridges min Page RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 2. Ecology approves StormFilter systems containing PhosphoSorb media for treatment at the cartridge flow rate shown in Table 1, and sized based on the water quality design flow rate for an off-line system. 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. Calculate the water quality design flow rates 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. • 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. The GULD designation has no expiration date but it may be amended or revoked by Ecology and is subject to the conditions specified below. Ecology's Conditions of Use: StormFilter systems containing PhosphoSorb media shall comply with these conditions: 1. Design, assemble, install, operate, and maintain StormFilter systems containing PhosphoSorb media in accordance with applicable Contech Engineered Solutions manuals, documents, and the Ecology Decision. 2. Use sediment loading capacity, in conjunction with the water quality design flow rate, to determine the target maintenance interval. 3. Owners shall install StormFilter systems in such a manner that bypass flows exceeding the water quality treatment rate or flows through the system will not re -suspend captured sediments. 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 Product Design Manual or the applicable Ecology Stormwater Manual. Design pre-treatment using the performance criteria and pretreatment practices provided in the Stormwater Management Manual for Western Washington (SWMMWW), the Stormwater Management Manual for Eastern Washington (SWMMEW), or 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 Page AESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT sediment from the vault, and replacing spent cartridges with recharged cartridges. • Indications of the need for maintenance include the 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 PhosphoSorb 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 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. Discharges from the StormFilter systems containing PhosphoSorb media shall not cause or contribute to water quality standards violations in receiving waters. Applicant: CONTECH Engineered Solutions Applicant's Address: 11835 NE Glenn Widing Dr. Portland, OR 97220 Page AESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Application Documents: ■ The Stormwater Management StormFilter, PhosphoSorb at a Specific Flow Rate of 1.67 gpm/ft2, Conditional Use Level Designation Application. August 2012. ■ Quality Assurance Project Plan The Stormwater Management StormFilter® PhosphoSorb® at a Specific Flow Rate of 1.67 gpm/ft2 Performance Evaluation. August 2012. ■ The Stormwater Management StormFilter® PhosphoSorb(V at a Specific Flow Rate of 1.67 gpm/ft2, General Use Level Designation, Technical Evaluation Report. October 2015. Applicant's Use Level Request: • General use level designation as a basic (TSS) and phosphorus (total phosphorus) treatment device in accordance with Table 2 of Ecology's 2011 Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol — Ecology (TAPE). Applicant's Performance Claims: Based on results from laboratory and field-testing, the applicant claims: • The Stormwater Management StormFilter® with PhosphoSorb® media operating at 1.67 gpm/ft2 is able to remove 80% of Total Suspended Solids (TSS) for influent concentrations greater than 100 mg/L, is able to remove greater than 80% TSS for influent concentrations greater than 200 mg/L, and achieve a 20 mg/L effluent for influent concentrations less than 100 mg/L. • The StormFilter with PhosphoSorb media is able to remove 50% or greater total phosphorus for influent concentrations between 0.1 to 0.5 mg/L. Recommendations: Ecology finds that: • CONTECH Engineered Solutions has shown Ecology, through laboratory and field testing, that the Stormwater Management StormFilter® with PhosphoSorb® media is capable of attaining Ecology's Basic and Total Phosphorus treatment goals. Findings of Fact: Laboratory testing • A Phosphosorb StormFilter cartridge test unit, operating at 28 L/min (equivalent to 1.0 gpm/ sq. ft.), and subject to SSC with a silt loam texture (25% sand, 65% silt, and 10% clay by mass) originating from SCS 106 provides a mean SSC removal efficiency of 88%; • A Phosphosorb StormFilter cartridge test unit, operating at 56 L/min (equivalent to 2.0 gpm/sq. ft.), and subject to SSC with a silt loam texture (25% sand, 65% silt, and 10% clay by mass) originating from SCS 106 provides a mean turbidity reduction of 82%; Page iRESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT • Laboratory testing of PhosphoSorb media in a Horizontal Flow Column (HFC; a 1/241h scale of a full cartridge) resulted in 50 percent dissolved phosphorus removal for the first 1,000 bed volumes. Granular activated carbon (GAC) tested under the same conditions resulted in 30 percent removal of dissolved phosphorus. Field testing • Contech conducted monitoring of a StormFilter® with PhosphoSorb® media at a site along Lolo Pass Road in Zigzag, Oregon between February 2012 and February 2015. The manufacturer collected flow -weighted influent and effluent composite samples during 17 separate storm events. The system treated approximately 96 percent of the flows recorded during the monitoring period. The applicant sized the system at 1.67 gpm/sq. ft. o Influent TSS concentrations for qualifying sampled storm events ranged from 40 to 780 mg/L. For influent concentrations less than 100 mg/L (n=2) the effluent concentration was less than 10 mg/L. For influent concentrations greater than 100 mg/L the bootstrap estimate of the lower 95 percent confidence limit (LCL95) of the mean TSS reduction was 85%. o Total phosphorus removal for 16 events with influent TP concentrations in the range of 0.1 to 0.5 mg/L averaged 75 percent. A bootstrap estimate of the lower 95 percent confidence limit (LCL95) of the mean total phosphorus reduction was 67 percent. Other StormFilter system with PhosphoSorb media items the Company should address: 1. Conduct testing to obtain information about maintenance requirements in order to come up with a maintenance cycle. 2. Conduct loading tests on the filter to determine maximum treatment life of the system. Technology Description: Download at: http://www.conteches.com/Products/Stonnwater- Management/Treatment/Stormwater-Management-StormFilter®.aspx Contact Information: Applicant: Jeremiah Lehman Contech Engineered Solutions 11815 NE Glenn Widing Drive Portland, OR, 97220 503-258-3136 j lehman(a,conteches. com Applicant website: www.conteches.com Page RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howiegecy.wa. gov Revision History Date Revision December 2012 Original use -level -designation document: CULD for basic and phosphorus treatment. January 2013 Revised document to match standard formatting August 2014 Revised TER and expiration dates November 2015 Approved GULD designation for Basic and Phosphorus treatment November 2016 Revised Contech contact information April 2017 Revised sizing language to note sizing based on Off-line calculations Page RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.52 Program License Number: 200410007 Project Simulation Performed on: 03/11/2021 8:46 PM Report Generation Date: 03/11/2021 8:47 PM Input File Name: Project Name: Analysis Title: Comments: Yost ROW Subbasin DRV Option 5.fld Edmonds Civic Playfield Yost ROW - DRV Option 5 Computational Time Step (Minutes): PRECIPITATION INPUT 15 Extended Precipitation Time Series Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 8.100 175.230 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 8.100 175.230 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 5 ---------- Subbasin : Civic Predeveloped Basin 1 -------Area (Acres) -------- Wetland 0.277 Subbasin Total 0.277 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ---------- Subbasin : Civic Predeveloped Basin 3 -------Area (Acres) -------- Wetland 0.526 ---------------------------------------------- Subbasin Total 0.526 ---------- Subbasin : Civic Predeveloped Basin 4 -------Area (Acres) -------- Wetland 1.714 ---------------------------------------------- Subbasin Total 1.714 ---------- Subbasin : Civic Predeveloped Basin 2 -------Area (Acres) -------- Wetland 0.174 ---------------------------------------------- Subbasin Total 0.174 ---------- Subbasin : Civic Bypass ---------- ------- Area (Acres) -------- Wetland 5.409 ---------------------------------------------- Subbasin Total 5.409 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 6 ---------- Subbasin : Civic Detention Basin 1 -------Area (Acres) ------ Impervious 0.277 ---------------------------------------------- Subbasin Total 0.277 ---------- Subbasin : Civic Detention Basin 3 -------Area (Acres) ------ Outwash Pasture 0.094 Outwash Grass 0.219 Impervious 0.213 61-91019T.7 MOM ---------- Subbasin : Civic Detention Basin 4 -------Area (Acres) ------ Outwash Pasture 0.460 Outwash Grass 0.534 Impervious 0.720 Subbasin Total 1.714 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ---------- Subbasin : Civic Detention Basin 2 -------Area (Acres) ------ Impervious 0.174 Subbasin Total 0.174 ---------- Subbasin : Civic Detention Bypass -------Area (Acres) ------ Outwash Pasture 3.350 Outwash Grass 0.068 Impervious 1.991 Subbasin Total 5.409 ---------- Subbasin : Yost ROW Subbasin -------Area (Acres) -- Outwash Grass 100.280 Impervious 66.850 Subbasin Total 167.130 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 Link Name: Downstream POC Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 9 Link Name: Civic Detention #1 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 75.08 0. 75.58 97. 76.08 997. 76.58 1896. 77.08 2796. RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 77.58 3696. 78.08 4596. 78.58 5496. 79.08 6396. 79.58 7295. Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 78.58 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 75.08 Diameter (in) 0.50 Orientation : Horizontal Elbow : No Link Name: Downstream POC Link Type: Copy Downstream Link: None Link Name: Civic Detention #3 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 81.17 0. 81.67 850. 82.17 1699. 82.67 4567. 83.17 7839. 83.67 11112. 84.17 14384. 84.67 17657. Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Maintenance Riser Geometry Riser Structure Type Riser Diameter (in) Common Length (ft) Riser Crest Elevation Hydraulic Structure Geometry Number of Devices: Average or Better Circular 12.00 0.000 83.67 ft ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 81.17 Diameter (in) 0.50 Orientation : Horizontal Elbow : No Link Name: Civic Detention #4 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 82.10 0. 82.60 2086. 83.10 7618. 83.60 15786. 84.10 23954. 84.60 32123. Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 83.60 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 82.10 Diameter (in) 0.50 Orientation : Horizontal Elbow : No RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Link Name: Civic Detention #2 Link Type: Structure Downstream Link Name: Downstream POC User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 75.64 0. 76.14 100. 76.64 668. 77.14 1235. 77.64 1802. 78.14 2369. 78.64 2936. 79.14 3503. 79.64 4071. 80.14 4638. Hydraulic Conductivity (in/hr) : 0.00 Massmann Regression Used to Estimate Hydralic Gradient Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 79.14 ft Hydraulic Structure Geometry Number of Devices: ---Device Number 1 --- Device Type Circular Orifice Control Elevation (ft) 75.64 Diameter (in) 0.50 Orientation : Horizontal Elbow : No Link Name: Yost ROW Infiltration <- Link Type: Structure Downstream Link Name: Downstream POC Prismatic Pond Option Used Pond Floor Elevation (ft) 100.00 Riser Crest Elevation (ft) Max Pond Elevation (ft) 106.00 Storage Depth (ft) 5.50 Pond Bottom Length (ft) 70.0 Pond Bottom Width (ft) 15.0 105.50 OFFSITE DETENTION MITIGATION. UNDER SEPARATE PERMIT. RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Pond Side Slopes (ft/ft) : L1= 0.00 Bottom Area (sq-ft) 1050. Area at Riser Crest El (sq-ft) 1,050. (acres) : 0.024 Volume at Riser Crest (cu-ft) 5,775. (ac-ft) 0.133 Area at Max Elevation (sq-ft) 1050. (acres) : 0.024 Vol at Max Elevation (cu-ft) 6,300. (ac-ft) 0.145 Constant Infiltration Option Used Infiltration Rate (in/hr): 1.72 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00 Common Length (ft) : 0.000 Riser Crest Elevation : 105.50 ft Hydraulic Structure Geometry Number of Devices: 0 Link Name: Yost ROW Flow Splitter Link Type: Flow Splitter L2= 0.00 W 1= 0.00 W 2= 0.00 Outflow 1 Connected to Link: Lnk9 - Dead Link Outflow 2 Connected to Link: Lnk8 - Yost ROW Bypass Splitter Rating Table Inflow Outflow 1 (cfs) (cfs) ---------------------------------------- 0.000 0.000 1.300 1.300 1.310 1.300 100.000 1.300 Link Name: Yost ROW Bypass Link Type: Copy Downstream Link: None Link Name: Dead Link Link Type: Copy Downstream Link: None Ouflow 2 (cfs) 0.000 0.000 0.010 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 5 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 6 Number of Links: 9 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Civic Predeveloped B 52.869 Subbasin: Civic Predeveloped B 100.395 Subbasin: Civic Predeveloped B 327.141 Subbasin: Civic Predeveloped B 33.210 Subbasin: Civic Bypass 1032.384 Link: Downstream POC 0.000 Total: 1546.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) Subbasin: Civic Detention Basi 0.000 Subbasin: Civic Detention Basi 89.125 Subbasin: Civic Detention Basi 283.797 Subbasin: Civic Detention Basi 0.000 Subbasin: Civic Detention Bypa 984.201 Subbasin: Yost ROW Subbasin 28412.460 Link: Civic Detention #1 Not Computed Link: Downstream POC 0.000 Link: Civic Detention #3 Not Computed Link: Civic Detention #4 Not Computed Link: Civic Detention #2 Not Computed Link: Yost ROW Infiltratio Not Computed Link: Yost ROW Flow Splitt Not Applicable Link: Yost ROW Bypass Not Applicable Link: Dead Link Not Applicable Total: 29769.590 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 9.785 ac-ft/year, Post Developed: 188.415 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT ********** Link: Downstream POC ********** Infiltration/Filtration Statistics -------------------- Inflow Volume (ac-ft): 323.73 Inflow Volume Including PPT-Evap (ac-ft): 323.73 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 323.73 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 9 ********** Link: Downstream POC ********** Infiltration/Filtration Statistics -------------------- Inflow Volume (ac-ft): 573.91 Inflow Volume Including PPT-Evap (ac-ft): 573.91 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 573.91 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: Downstream POC Scenario Postdeveloped Compliance Link: Downstream POC *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.194 2-Year 0.302 5-Year 0.441 5-Year 0.582 10-Year 0.711 10-Year 0.684 25-Year 1.146 25-Year 0.908 50-Year 1.271 50-Year 0.937 100-Year 1.418 100-Year 1.038 200-Year 1.437 200-Year 1.144 500-Year 1.458 500-Year 1.284 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -52.3% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -41.2% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): -5.9% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Detention Stage Storage Tables Detention Layer Area 1 (sf) Area 1 Live Storage Depth (ft) Area 2 (sf) Area 2 Live Storage Depth (ft) Area 3 (sf) Area 3 Live Storage Depth (ft) %Voids Gravel Detention Live Storage Volume (cf) 1 552 3.5 4,590 3.0 35 5,496 2 573 3.5 2,668 3.0 35 3,503 3 4,854 2.5 11,533 1.5 2,313 1.0 35 11,112 4 11,922 1.5 19,688 1.0 15,065 0.5 35 15,786 35,897 Detention Basin 1 Stage Storage Table Elev (ft) Surf Area (sf) Vol (cf) 75.08 552 0.00 75.58 5,142 96.60 76.08 5,142 996.45 76.58 5,142 1896.30 77.08 5,142 2796.15 77.58 5,142 3696.00 78.08 5,142 4595.85 78.58 5,142 5495.70 79.08 5,142 6395.55 79.58 5,142 7295.40 Detention Basin 3 Stage Storage Table Elev (ft) Surf Area (sf) Vol (cf) 81.17 4,854 0.00 81.67 4,854 849.45 82.17 16,387 1698.90 82.67 18,700 4566.63 83.17 18,700 7839.13 83.67 18,700 11111.63 84.17 18,700 14384.13 84.67 18,700 17656.63 Detention Basin 2 Stage Storage Table Elev (ft) Surf Area (sf) Vol (cf) 75.64 573 0.00 76.14 3,241 100.28 76.64 3,241 667.45 77.14 3,241 1234.63 77.64 3,241 1801.80 78.14 3,241 2368.98 78.64 3,241 2936.15 79.14 3,241 3503.33 79.64 3,241 4070.50 80.14 3,241 4637.68 Detention Basin 4 Stage Storage Table Elev (ft) Surf Area (sf) Vol (cf) 82.1 11,922 0.00 82.6 31,610 2086.35 83.1 46,675 7618.10 83.6 46,675 15786.23 84.1 46,675 23954.35 84.6 46,675 32122.48 Appendix C Construction Stormwater Pollution Prevention Plan Civic Center Playfield — WalkEMUhU 2021 AppenadW,V SEND CES DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT I I I I I I PORTABLE SEDIMENT TANK(S)t FIELD LOCATE —]----------------------------------——-—------—--------- CONSTRU:LOCATION STORMWATER I DISCHARGANDCOMPLIANMPLING POINT TOP OF LAYBACK SLOPE. „x SEE MASS EXCAVATION NOTE 3. FILTER FABRIC FENCE (TYP) i � jj FIELD LOCATE (TYP) ��,��\ R. BOTTOM OF LAYBACK SLOPE. Vr°P TEMPOR�ARY CH AINLINK p� ENTRANCE. FIELD LOCATE. (TYP) I'`' PROPERTY LINE (TYP) TEMPORARY SEDIMENT TRAP FOR CATCH BASIN FIELD LOCATE (TYP) RESUB (NOTE: This plan included with this report is for reference only and is not scalable. ForNiar252021 complete full-size set of plans, refer to the permit submittal) CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT SWPPP NOTES 1. INSTALL AND MAINTAIN ALL SWPP MEASURES ACCORDING TO APPROVED PLANS, CITY OF EDMONDS STANDARDS, AND ALL OTHERS MEASURES THAT MAY BE REQUIRED DURING CONSTRUCTION. 2. MINIMUM VOLUME OF SEDIMENT TANK LIVE STORAGE ASSUMES ALL SOILS WITHIN EXCAVATION ARE EXPOSED. F ROVDE CONSTRUCTION FENCING ON PRIVATE PROPERTY AS REQUIRED FOR SAFETY AND AS DIRECTED Y THE OWNER. CONSTRUCTION FENCING LIMITS SHOWN ARE SCHEMATIC IN NATURE. AS ONSTRUCTION PROGRESSES, UPDATE FENCING LIMITS TO MAINTAIN SITE SAFETY AND SECURITY WHILE LLOWING FOR CONTINUOUS PEDESTRIAN AND VEHICULAR ACCESS AROUND THE SITE, TO THE AXIMUM EXTENT PRACTICABLE. TOCKPILE MATERIAL STORED ON SITE MUST BE COVERED AT ALL TIMES. MASS EXCAVATION NOTES 1. THE APPROXIMATE BOTTOM OF EXCAVATION ELEVATIONS SHOWN ARE TO THE BOTTOM OF GRAVEL DETENTION LAYERS. SEE C300 SERIES FOR BOTTOM OF GRAVEL ELEVATIONS. 2. THIS PLAN DOES NOT SHOW OVEREXCAVATION REQUIRED TO REMOVE UNSUITABLE SOILS. SEE THE PROJECT GEOTECHNICAL REPORT BY LANDAU ASSOCIATES DATED OCTOBER 30,2019 FOR ANTICIPATED OVEREXCAVATION REQUIREMENTS AND COORDINATE EXTENTS OF EXCAVATION WITH THE OWNER'S GEOTECHNICAL REPRESENTATIVE IN THE FIELD. 3. THE LAYBACK SHOWN FOR GRAVEL DETENTION LAYER EXCAVATIONS TO SURROUNDING GRADES ASSUME CUT SLOPES OF 211:1V OR FLATTER. 4. THIS PLAN DOES NOT SHOW EXCAVATION FOR FOOTINGS. SEE STRUCTURAL FOR FOOTING ELEVATIONS. 1 ETHE ROJECT GEOTECHNICAL REPORT PREPARED BY LANDAU AND DATED OCTOBER 30, 2019, NDWATER ELEVATION IS ASSUMED TO BE 2 FEET BELOW EXISTING GRADE.GINEER OF RECORD IF GROUNDWATER IS ENCOUNTERED AT AN ELEVATION HIGHER THAN LEGEND APPROXIMATE LIMIT OF WORK - - PROPERTY LINE TEMPORARY CHAINLINK CONSTRUCTION FENCE e 5 cno FILTER FABRIC FENCE C111 TEMPORARY INTERCEPTOR DRAINAGE SWALE 2 C110 So— TEMPORARY Q �IZD �HAG RGE PIPE 1 E ® TEMPORARY SEDIMENT TRAP FOR e CATCH BASIN C111 © 55 GALLON DRUM WITH PUMP QC7310) — GEOTEXTILE ENCASED CHECK DAM 4 C110 7 g000�oO�oO �00 STABILIZED CONSTRUCTION ENTRANCE C111 ® PORTABLE SEDIMENT TANK TOP 77 LAYBACK SLOPE BOTTOM 0Call 811 two business days before you dig NORTH (5 0 20 40 80 1 inch = 40 feet APPROVED FOR CONSTRUCTION CITY OF EDMONDS DATE: BY: CITY ENGINEERING DIVISION CITY OF EDMONDS 700 MAIN STREET EDMONDS, WA 98020 425-771-0320 WALKER MACY 218 SND AVENUE, SUITE 1310 SEAT TLE, WA 98101 2D6-602-3874 16015th Avenue, Suite 1600 Seattle, WA 98101 206.622.5822 www.kplf.com CIVIC CENTER PLAYFIELD EDMONDS, WA "°�iNOMeE P3282.04 oam,9v. CM aE Ern"' KMK PERMIT SET 12/09/2019 IL REV-001 03/13/2020 SWPP & MASS EXCAVATION PLAN C100 Appendix D Operation and Maintenance Manual Civic Center Playfield — WalkEMUhU 2021 AppendiXPV SEND CES DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 11 /26/2019 BMP Maintenance Tables Maintenance Results Expected Component Defect Conditions When Maintenance Is Needed When Maintenance Is Performed See Table V-A.1: Rock Missing See Table V-A.1: Maintenance Standards - Detention Maintenance Ponds Standards - Emergency Detention Ponds Overflow Spillway See Table V-A.1: See Table V-A.1: Maintenance Standards - Detention Maintenance Erosion Standards - Ponds Detention Ponds Pre -settling Facility or sump Ponds and filled with Sediment 6" or designed sediment trap depth of sediment. Sediment is removed. Vaults and/or debris Table V-A.3: Maintenance Standards - aystP_ms (Tanks/Vaults) Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is Performed Plugged Air Vents One-half of the cross section of a vent is blocked at any Vents open and point or the vent is damaged. functioning. Accumulated sediment depth exceeds 10% of the diameter of the storage area for 1/2 length of storage vault or any point depth exceeds 15% of diameter. All sediment and Debris and Sediment debris removed from (Example: 72-inch storage tank would require cleaning storage area. when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Storage Area Any openings or voids allowing material to be Joints Between transported into facility. All joint between Tank/Pipe Section (Will require engineering analysis to determine tank/pipe sections are sealed. structural stability). Tank Pipe Bent Out of Any part of tank/pipe is bent out of shape more than Tank/pipe repaired Shape 10 /o of its design shape. (Review required by engineer or replaced to to determine structural stability). design. Cracks wider than 1/2-inch and any evidence of soil Vault replaced or Vault Structure particles entering the structure through the cracks, or repaired to design specifications and is Includes Cracks in maintenance/inspection personnel determines that the structurally sound. Wall, Bottom, Damage vault is not structurally sound. to Frame and/or Top Cracks wider than 1/2-inch at the joint of any inlet/outlet No cracks more than Slab pipe or any evidence of soil particles entering the vault 1/4-inch wide at the through the walls. joint of the inlet/outlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Any open Manhole is' FSAU manhole requires maintenance. Mar 25 202 OR I s % https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htmif P.RrME15/45 11 /26/2019 BMP Maintenance Tables Maintenance Results Expected Component Defect Conditions When Maintenance is Needed When Maintenance is Performed Mechanism cannot be opened by one maintenance Locking Mechanism person with proper tools. Bolts into frame have less Mechanism opens Not Working than 1/2 inch of thread (may not apply to self-locking with proper tools. lids). Cover can be Cover Difficult to One maintenance person cannot remove lid after removed and Remove applying normal lifting pressure. Intent is to keep cover reinstalled by one from sealing off access to maintenance. maintenance person. Ladder meets Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, misalignment, design standards. not securely attached to structure wall, rust, or cracks. Allows maintenance person safe access. See Table V-A.5: See Table V-A.5: Catch Basins Maintenance See Table V-A.5: Maintenance Standards - Catch Maintenance Basins Standards - Catch Standards - Catch Basins Basins Table V-A.4: Maintenance Standards - Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash and Debris (Includes Material exceeds 25% of sump Control structure orifice is not Sediment) depth or 1 foot below orifice blocked. All trash and debris plate. removed. Structure is not securely attached to manhole wall. Structure securely attached to wall General Structure is not in upright and outlet pipe. position (allow up to 10% from Structure in correct position. plumb). Structural Damage Connections to outlet pipe are Connections to outlet pipe are water tight; structure repaired or not watertight and show signs replaced and works as designed. of rust. Structure has no holes other than Any holes - other than designed designed holes. holes - in the structure. RESUB Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%/ F3F .RTME'6/45 11 /26/2019 BMP Maintenance Tables Maintenance Defect Condition When Maintenance Results Expected When Component is Needed Maintenance is Performed Cleanout gate is not watertight Gate is watertight and works as or is missing. designed. Gate cannot be moved up and Gate moves up and down easily down by one maintenance and is watertight. Cleanout Damaged or Missing person. Gate Chain/rod leading to gate is Chain is in place and works as missing or damaged. designed. Gate is rusted over 50% of its Gate is repaired or replaced to surface area. meet design standards. Control device is not working Plate is in place and works as Orifice Plate Damaged or Missing properly due to missing, out of designed. place, or bent orifice plate. Obstructions Any trash, debris, sediment, or Plate is free of all obstructions and vegetation blocking the plate. works as designed. Overflow Any trash or debris blocking (or Pipe is free of all obstructions and Pipe Obstructions having the potential of blocking) works as designed. the overflow pipe. See Table V-A.3: Maintenance See Table V-A.3: Maintenance See Table V-A.3: Maintenance Manhole Standards - Closed Detention Standards - Closed Detention Standards - Closed Detention Systems (Tanks/Vaults) Systems (Tanks/Vaults) Systems (Tanks/Vaults) Catch Basin See Table V-A.5: Maintenance See Table V-A.5: Maintenance See Table V-A.5: Maintenance Standards - Catch Basins Standards - Catch Basins Standards - Catch Basins Table V-A.5: Maintenance Standards - Catch Basins Maintenance Component Defect Conditions When Maintenance is Needed Results Expected When Maintenance is performed General Trash or debris which is located immediately in front of the catch No Trash or debris basin opening or is blocking inletting capacity of the basin by located immediately more than 10%. in front of catch Trash or debris (in the basin) that exceeds 60 percent of the basin or on grate sump depth as measured from the bottom of basin to invert of opening. the lowest pipe into or out of the basin, but in no case less than No trash or debris in Trash & a minimum of six inches clearance from the debris surface to the the catch basin. Debris invert of the lowest pipe. Inlet and outlet Trash or debris in any inlet or outlet pipe blocking more than 1/3 pipes free of trash of its height. or debris. Dead animals or vegetation that could generate odors that could No dead animals or cause complaints or dangerous gases (e.g., methane). vegetation present within the basin. Mar 25 202 CITY OF EDMONDS S https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%9€'.^.RTMEN7/45 11 /26/2019 BMP Maintenance Tables Results Expected Maintenance Defect Conditions When Maintenance is Needed When Component Maintenance is performed Sediment (in the basin) that exceeds 60 percent of the sump depth as measured from the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a Sediment minimum of 6 inches clearance from the sediment surface to the No sediment in the invert of the lowest pipe. catch basin catch Top slab has holes larger than 2 square inches or cracks wider Top slab is free of Structure than 1/4 inch. (Intent is to make sure no material is running into holes and cracks. Damage to basin). Frame is sitting Frame and/or Frame not sitting flush on top slab, i.e., separation of more than flush on the riser Top Slab 3/4 inch of the frame from the top slab. Frame not securely rings or top slab attached and firmly attached. Basin replaced or Fractures or Maintenance person judges that structure is unsound. repaired to design Cracks in Grout fillet has separated or cracked wider than 1/2 inch and standards. Basin Walls/ longer than 1 foot at the joint of any inlet/outlet pipe or any Pipe is regrouted Bottom evidence of soil particles entering catch basin through cracks. and secure at basin wall. Settlement/ If failure of basin has created a safety, function, or design Basin replaced or repaired to design Misalignment problem. standards. Vegetation growing across and blocking more than 10% of the No vegetation blocking opening to basin opening. basin. Vegetation Vegetation growing in inlet/outlet pipe joints that is more than six No vegetation or inches tall and less than six inches apart. root growth present. Contamination See Table V-A.1: Maintenance Standards - Detention Ponds No pollution and Pollution present. Cover/grate is in Cover Not in Cover is missing or only partially in place. Any open catch basin place, meets design Place requires maintenance. standards, and is secured Catch Basin LockingMechanism Mechanism cannot be opened by one maintenance person with Mechanism opens Cover Not Working proper tools. Bolts into frame have less than 1/2 inch of thread. with proper tools. One maintenance person cannot remove lid after applying Cover can be Cover Difficult normal lifting pressure. removed by one to Remove maintenance (Intent is keep cover from sealing off access to maintenance.) person. RESU Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%/ F3F .RTME'8/45 11 /26/2019 BMP Maintenance Tables Results Expected Maintenance Defect Conditions When Maintenance is Needed When Component Maintenance is performed Ladder meets Ladder Ladder Rungs Ladder is unsafe due to missing rungs, not securely attached to design standards and allows Unsafe basin wall, misalignment, rust, cracks, or sharp edges. maintenance person safe access. Grate opening Grate opening Unsafe Grate with opening wider than 7/8 inch. meets design standards. Trash and Trash and debris that is blocking more than 20% of grate surface Grate free of trash Metal GrateE Debris inletting capacity. and debris. (If Applicable) Grate is in place, meets the design Damaged or Grate missing or broken member(s) of the grate. standards, and is Missing. installed and aligned with the flow path. Table V-A.6: Maintenance Standards - Debris Barriers (e.g., Trash Racks) Maintenance Defect Condition When Maintenance is Needed Results Expected When Components Maintenance is Performed General Trash and Trash or debris that is plugging more than 20% Barrier cleared to design flow Debris of the openings in the barrier. capacity. Bars in place with no bends more Bars are bent out of shape more than 3 inches. than 3/4 inch. Damaged/ Bars are missing or entire barrier missing. Bars in place according to Missing Bars. design. Metal Bars are loose and rust is causing 50% deterioration to any part of barrier. Barrier replaced or repaired to design standards. Inlet/Outlet Pipe Debris barrier missing or not attached to pipe Barrier firmly attached to pipe Table V-A.7: Maintenance Standards - Energy Dissipators Results Maintenance Expected When Defect Conditions When Maintenance is Needed Components Maintenance is Performed External: RESUB Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%3F.^ TMEN3/45 11/26/2019 BMP Maintenance Tables Results Maintenance Defect Conditions When Maintenance is Needed Expected When Components Maintenance is Performed Missing or Only one layer of rock exists above native soil in area five Rock pad replaced to design Moved Rock square feet or larger, or any exposure of native soil. standards. Rock Pad Rock pad Erosion Soil erosion in or adjacent to rock pad. replaced to design standards. Pipe Pipe Plugged Accumulated sediment that exceeds 20% of the design cleaned/flushed with Sediment depth. so that it matches design. Not Discharging Visual evidence of water discharging at concentrated points "sheet Trench redesigned or Water Properly along trench (normal condition is a flow"❑ of water rebuilt to along trench). Intent is to prevent erosion damage. standards. Dispersion Trench Perforations Over 1/2 of perforations in pipe are plugged with debris and Perforated pipe Plugged. sediment. cleaned or replaced. Water Flows Maintenance person observes or receives credible report of Facility rebuilt or Out Top of water flowing out during any storm less than the design redesigned to Distributor storm or its causing or appears likely to cause damage. standards. Catch Basin. Receiving Area Water in receiving area is causing or has potential of No danger of Over -Saturated causing landslide problems. landslides. Internal: Worn or Damaged Post, Structure dissipating flow deteriorates to 1/2 of original size Structure replaced Baffles, Side of or any concentrated worn spot exceeding one square foot to design Manhole/Chamber Chamber which would make structure unsound. standards. See Table V-A.5: Other Defects See Table V-A.5: Maintenance Standards - Catch Basins Maintenance Standards - Catch Basins Table V-A.8: Maintenance Standards - Typical Biofiltration Svc, —'— Condition When Maintenance Defect or Maintenance is Recommended Maintenance to Correct Problem Component Problem Needed RESUB Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l 9SWM M WW/2019SWMMW W.htm#Topics/VolumeV/App_BM PMaintenanceTables.htm%3Ef^RTM4B/45 11/26/2019 BMP Maintenance Tables Maintenance Defect or Condition When Component Problem Maintenance is Recommended Maintenance to Correct Problem Needed General Remove sediment deposits on grass treatment area of Sediment Sediment depth exceeds the bio-swale. When finished, swale should be level from Accumulation on 2 inches. side to side and drain freely toward outlet. There should Grass be no areas of standing water once inflow has ceased. When water stands in Any of the following may apply: remove sediment or trash Standing Water the swale between blockages, improve grade from head to foot of swale, storms and does not remove clogged check dams, add underdrains or convert drain freely. to a wet biofiltration swale. Flow spreader uneven or clogged so that flows Level the spreader and clean so that flows are spread Flow spreader are not uniformly distributed through evenly over entire swale width. entire swale width. When small quantities of water continually flow through the swale, even Constant when it has been dry for Add a low -flow pea -gravel drain the length of the swale Baseflow weeks, and an eroded, or by-pass the baseflow around the swale. muddy channel has formed in the swale bottom. When grass is sparse or I Determine why grass growth is poor and correct that Poor Vegetation bare or eroded patches condition. Re -plant with plugs of grass from the upper Coverage occur in more than 10% slope: plant in the swale bottom at 8-inch intervals. Or re - of the swale bottom. seed into loosened, fertile soil. When the grass becomes excessively tall (greater than 10-inches); Mow vegetation or remove nuisance vegetation so that Vegetation when nuisance weeds flow not impeded. Grass should be mowed to a height of and other vegetation 3 to 4 inches. Remove grass clippings. starts to take over. Excessive Grass growth is poor because sunlight does If possible, trim back over -hanging limbs and remove Shading not reach swale. brushy vegetation on adjacent slopes. Inlet/outlet areas Remove material so that there is no clogging or blockage Inlet/Outlet clogged with sediment in the inlet and outlet area. and/or debris. Trash and Debris Trash and debris Accumulation accumulated in the bio- Remove trash and debris from bioswale. swale. RESUB Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%3Ef^RTMEK/45 11 /26/2019 BMP Maintenance Tables Maintenance Defect or Condition When Component Problem Maintenance is Recommended Maintenance to Correct Problem Needed For ruts or bare areas less than 12 inches wide, repair Eroded or scoured the damaged area by filling with crushed gravel. If bare swale bottom due to flow areas are large, generally greater than 12 inches wide, Erosion/Scouring channelization, or higher the swale should be re -graded and re -seeded. For flows. smaller bare areas, overseed when bare spots are evident, or take plugs of grass from the upper slope and plant in the swale bottom at 8-inch intervals. Table V-A.9: Maintenance Standards - Wet Biofiltration Swale Maintenance Defect or Condition When Maintenance Recommended Maintenance to Correct Component Problem is Needed Problem Sediment Sediment depth exceeds 2- Accumulation inches in 10% of the swale Remove sediment deposits in treatment area. treatment area. Water Depth Water not retained to a depth of Build up or repair outlet berm so that water is about 4 inches during the wet retained in the wet swale. season. Vegetation becomes sparse Determine cause of lack of vigor of vegetation and and does not provide adequate correct. Replant as needed. For excessive cattail Wetland filtration, OR vegetation is growth, cut cattail shoots back and compost off - Vegetation crowded out by very dense site. Note: normally wetland vegetation does not clumps of cattail, which do not need to be harvested unless die -back is causing General allow water to flow through the oxygen depletion in downstream waters. clumps. Inlet/Outlet Inlet/outlet area clogged with Remove clogging or blockage in the inlet and sediment and/or debris. outlet areas. Trash and Debris See Table V-A.1: Maintenance Remove trash and debris from wet swale. Accumulation Standards - Detention Ponds Check design flows to assure swale is large Swale has eroded or scoured enough to handle flows. By-pass excess flows or Erosion/Scouring due to flow channelization, or enlarge swale. Replant eroded areas with fibrous - higher flows. rooted plants such as Juncus effusus (soft rush) in wet areas or snowberry (Symphoricarpos albus) in dryer areas. Table V-A.10: Maintenance Standards - Filter Strips Condition When Maintenance Defect or Maintenance is Recommended Maintenance to Correct Problem Component Problem Needed General Sediment Accumulation on Sediment depth Remove sediment deposits, re -level so slope is e REMJ exceeds 2 inches. flows pass evenly through strip. Grass Mar 25 2021 DEVELUMEN s https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%3Ef^RTM�/45 11 /26/2019 BMP Maintenance Tables Maintenance Defect Condition When Maintenance is Results Expected When Component Needed Maintenance is Performed Cover cannot be opened, Access Cover corrosion/deformation of cover. Cover repaired to proper working Damaged/Not Working Maintenance person cannot remove specifications or replaced. cover using normal lifting pressure. Blocking material removed or cleared from ventilation area. A specified % of Ventilation Ventilation area blocked or plugged the vault surface area must provide ventilation to the vault interior (see design specifications). Cracks wider than 1/2-inch or evidence Vault Structure of soil particles entering the structure through the cracks, or Vault replaced or repairs made so that Damaged; Includes maintenance/inspection personnel vault meets design specifications and Cracks in Walls, determine that the vault is not is structurally sound. Bottom, Damage to structurally sound. Vault repaired so that no cracks exist Frame and/or Top Slab. Cracks wider than 1/2-inch at the joint of wider than 1/4-inch at the joint of the any inlet/outlet pipe or evidence of soil inlet/outlet pipe. particles entering through the cracks. Baffles or walls corroding, cracking, Baffles/Internal warping and/or showing signs of failure Baffles repaired or replaced to walls as determined by specifications. maintenance/inspection person. Ladder is corroded or deteriorated, not Ladder replaced repaired to Access Ladder functioning properly, not securely specifications, andd is safe to use as Damaged attached to structure wall, missing determined by inspection personnel. rungs, cracks, and misaligned. Table V-A.15: Maintenance Standards - Maintenance Defect I Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Below Sediment Ground Vault Accumulation on Sediment depth exceeds 0.25-inches Media. Sediment Sediment depth exceeds 6-inches in first Accumulation in chamber. Vault Trash/Debris I Trash and debris accumulated on compost filter Accumulation bed. Sediment in Drain When drain pipes, clean -outs, become full with Pipes/Clean-Outs I sediment and/or debris. No sediment deposits which would impede permeability of the compost media. No sediment deposits in vault bottom of first chamber. Trash and debris removed from the compost filter bed. Sediment and debris removed. Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%3EfnRTM2F/45 11 /26/2019 BMP Maintenance Tables Maintenance Defect Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Damaged Pipes Any part of the pipes that are crushed or Pipe repaired and/or damaged due to corrosion and/or settlement. replaced. Access Cover Cover cannot be opened; one person cannot Cover repaired to proper Damaged/Not open the cover using normal lifting pressure, working specifications or Working corrosion/deformation of cover. replaced. Cracks wider than 1/2-inch or evidence of soil Vault replaced or repairs Vault Structure particles entering the structure through the made so that vault meets design specifications and is Includes Cracks in cracks, or maintenance/inspection personnel structurally sound. Wall, Bottom, determine that the vault is not structurally sound. Damage to Frame Cracks wider than 1/2-inch at the joint of any Vault repaired so that no and/or Top Slab inlet/outlet pipe or evidence of soil particles cracks exist wider than 1/4- entering through the cracks. inch at the joint of the inlet/outlet pipe. Baffles corroding, cracking warping, and/or Baffles repaired or replaced Baffles showing signs of failure as determined by to specifications. maintenance/inspection person. Ladder is corroded or deteriorated, not Ladder replaced or repaired Access Ladder functioning properly, not securely attached to and meets specifications, and is safe to use as Damaged structure wall, missing rungs, cracks, and determined by inspection misaligned. personnel. Drawdown of water through the media takes Below Media longer than 1 hour, and/or overflow occurs Media cartridges replaced. Ground frequently. Cartridge Type Short Circuiting Flows do not properly enter filter cartridges. Filter cartridges replaced. Table V-A.16: Maintenance Standards - Baffle Oil/Water Separators (API Type) Maintenance Defect Condition When Maintenance is I Results Expected When Component Needed Maintenance is Performed General Monitoring Sediment Accumulation Trash and Debris Accumulation Inspection of discharge water for obvious signs of poor water quality. Sediment depth in bottom of vault exceeds 6-inches in depth. Effluent discharge from vault should be clear with out thick visible sheen. No sediment deposits on vault bottom that would impede flow through the vault and reduce separation efficiency. Trash and debris accumulation in vault, Trash and debris removed from or pipe inlet/outlet, floatables and non- In vault, and inlet/outlet I floatables. piping. g' RESUB Mar 25 2021 CITY OF EDMONDS https://fortress.wa.gov/ecy/ershare/wq/Permits/Flare/20l9SWMMWW/2019SWMMWW.htm#Topics/VolumeV/App_BMPMaintenanceTables.htm%3Ef^RTMq'8/45 Appendix E Geotechnical Report Civic Center Playfield — WalkEMUhU 2021 AppendiXPV SEND CES DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Geotechnical Engineering Report Civic Center Playfield Improvements Edmonds, Washington October 19, 2017 Revised October 30, 2019 Prepared for Walker Macy Seattle, Washington LANDAU ASSOCIATES 130 2nd Avenue AO Edmonds, WA UB (425) 778vORM 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Geotechnical Engineering Report Civic Center Playfield Improvements Edmonds, Washington This document was prepared by, or under the direct supervision of, the undersigned, whose seal is affixed below. Name: Steven R. Wright Date: October 30, 2019 Document prepared by: Project EIT 1o/301IQ Sean M. Gertz, EIT J J Document reviewed by:LSteven R. Wright, PE Y g Quality Reviewer Date! October 30, 2019 Project No.: 1548002 010.011 File path! P:\1548\002\FIIeRoom\R Project Coordinator: RGM LANDA U g ASSOCZ12021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates TABLE OF CONTENTS 1.0 INTRODUCTION..............................................................................................................................1-1 1.1 Project Description.............................................................................................................1-1 1.2 Scope of Services................................................................................................................1-1 2.0 SITE CONDITIONS...........................................................................................................................2-1 2.1 General Geologic Conditions..............................................................................................2-1 2.2 Surface Conditions..............................................................................................................2-1 2.3 Subsurface Soil Conditions.................................................................................................2-2 2.4 Groundwater Conditions....................................................................................................2-2 3.0 SEISMIC CONSIDERATIONS............................................................................................................3-1 3.1 Site Classification and Seismic Design Parameters............................................................3-1 3.2 Liquefaction Potential........................................................................................................3-1 4.0 CONCLUSIONS AND RECOMMENDATIONS....................................................................................4-1 4.1 Site Preparation and Earthwork.........................................................................................4-1 4.1.1 Site and Subgrade Preparation.......................................................................4-1 4.1.2 Engineered Fill Materials................................................................................4-3 4.1.3 Reuse of Site Soil............................................................................................4-4 4.1.4 Wet Weather Earthwork Considerations.........................................................4-4 4.1.5 Construction Dewatering................................................................................4-5 4.1.6 Temporary Excavation Slopes.........................................................................4-5 4.2 Stormwater Infiltration.......................................................................................................4-6 4.3 Foundations........................................................................................................................4-7 4.3.1 Shallow Foundation Support...........................................................................4-7 4.3.2 Foundation Settlement...................................................................................4-8 4.3.3 Concrete Slabs on Grade................................................................................4-8 4.3.4 Foundation and Site Drainage.........................................................................4-9 4.4 Retaining Walls...................................................................................................................4-9 4.5 Buoyancy Forces on Structures Below the Groundwater Table.......................................4-11 4.6 Pavement Design..............................................................................................................4-12 4.7 Light Pole Foundations.....................................................................................................4-13 4.7.1 Design Considerations..................................................................................4-13 4.7.2 Construction Considerations.........................................................................4-14 5.0 REVIEW OF DOCUMENTS AND CONSTRUCTION OBSERVATIONS.................................................5-1 6.0 USE OF THIS REPORT......................................................................................................................6-1 7.0 REFERENCES...................................................................................................................................7-1 Geotechnical Engineering Report 1548002.010.ORCSUB Civic Center Playfield Improvements October 30, 20 C i Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Figure Title 1 Vicinity Map 2 Site and Exploration Plan 3 Comparison of Existing, Proposed, and Bottom of Peat Grades TABLES Table Title 1 Depth to Groundwater Summary 2 Seismic Design Parameters 3 Comparison of Existing, Proposed, and Bottom of Peat Grades 4 Engineered Fill Materials 5 Recommended Soils Parameters for Design of Temporary Shoring 6 Recommended Pavement Sections 7 Recommended Parameters for Luminaire Foundation Design 8 Recommended Parameters for Luminaire Foundation Design Vicinity of Boring B-6 and Test Pit TP-1 APPENDICES Appendix Title A Field Explorations B Laboratory Soil Testing C Summary Logs of Previous Explorations Geotechnical Engineering Report 1548002.010.ORC c U B Civic Center Playfield Improvements October 30, 20 GJ ii Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates This page intentionally left blank. Geotechnical Engineering Report 1548002.010.ORCSUB Civic Center Playfield Improvements October 30, 20 G Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 1.0 INTRODUCTION This report presents the results of Landau Associates' (LAI) geotechnical engineering study that was conducted for the proposed Civic Center Playfield Improvements project in Edmonds, Washington. The general project location is shown on the Vicinity Map (Figure 1). A project base map and the locations of our explorations are shown on the Site and Exploration Plan (Figure 2). This report has been prepared based on LAI's discussions with Walker Macy, KPFF, and the City of Edmonds (City); conceptual site plans provided by Walker Macy; data collected during our field exploration and laboratory testing programs; our familiarity with geologic conditions within the vicinity of the project site; and our experience on similar projects. 1.1 Project Description The project includes the design of improvements for the Civic Center Playfield in Edmonds, Washington. The proposed improvements include a restroom and concession building, shade pavilion, sports courts and fields, a water feature, playground, skate park, scramble wall, view terraces, and walkways. It is our understanding that the restroom and concession building is currently planned as a pre-engineered building and that design of the building will be performed by the manufacturer. The proposed project also includes site grading activities, including constructing berms and terraces. Improvements related to the existing Boys & Girls Club building are not included in this phase of work. 1.2 Scope of Services Walker Macy retained LAI to provide geotechnical engineering services to support design of the proposed playfield improvements. Our services were provided in general accordance with the scope of services outlined in agreements between Walker Macy and LAI dated April 24, 2017 and October 9, 2019, and City of Edmonds Task Order 18-08. Our scope of services included the following specific tasks: • Reviewing readily available published geologic maps, geotechnical reports, and drawings for the project area and preparing a geotechnical work plan • Completing a geologic reconnaissance to collect information on the general nature and physical features of the project area • Obtaining public and private utility clearances prior to performing field explorations • Advancing three exploratory borings and seven exploratory test pits to characterize the nature of the subsurface soil and groundwater conditions at the project site • Advancing four additional exploratory borings in support of the associated Civic Center Sanitary Sewer project • Installing piezometers in six of the seven exploratory borings • Collecting representative soil samples at selected depth intervals Geotechnical Engineering Report 1548002.010.OftC c U B Civic Center Playfield Improvements October 30, 20 GJ 1 1 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates • Logging the exploratory borings and test pits and recording pertinent information, including soil sample depths, stratigraphy, soil engineering characteristics, and groundwater occurrence • Conducting a geotechnical laboratory testing program • Performing geotechnical engineering analyses and evaluating data derived from the subsurface investigation and laboratory testing program • Developing geotechnical engineering conclusions and recommendations to support design and construction of the proposed playfield improvements • Preparing and submitting this written report summarizing the results of our findings, conclusions, and recommendations for the project. This report includes: — A site plan showing pertinent existing site features and the approximate locations of the borings and test pits completed for this project. — Descriptive logs of the subsurface explorations and the results of the geotechnical laboratory testing program. — A site plan and boring logs from previous explorations by others in the vicinity of the project site. — A summary of observed surface and subsurface soil and groundwater conditions. — A figure that presents a comparison of the existing grades, proposed grades, and the elevation of the bottom of the peat that was observed at the location of each exploration completed by LAI and others in the vicinity of the site. — An evaluation of the feasibility of the proposed project with respect to geotechnical considerations. — Recommendations for earthwork and grading, including stripping depth, subgrade preparation, utility trench excavation, construction dewatering, the reuse of onsite materials and structural fill, and structural fill placement and compaction. — Seismic design parameters (i.e., site class and spectral acceleration coefficients) for the proposed structure using map -based methods in accordance with the 2015 International Building Code. — Recommendations for shallow foundation support of the proposed structure, along with allowable soil bearing capacity, minimum footing width and depth, lateral resistance criteria, and settlement estimates. — Recommendations regarding subgrade preparation and support for concrete slab on grade construction — Recommendations for the proposed scramble wall, including lateral earth pressures, allowable bearing resistance, and resistance to sliding. — Recommendations for resistance against buoyancy forces against buried structures. — Pavement recommendations for the proposed parking area. — Recommendations pertaining to design of the proposed light pole foundations. — Recommendations for geotechnical monitoring and consultation during construction. Geotechnical Engineering Report 1548002.010.ORC c U B Civic Center Playfield Improvements October 30, 20 GJ 1-2 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 2.0 SITE CONDITIONS This section discusses the general geologic setting of the project area and describes the surface and subsurface conditions observed at the project site at the time of our field investigation. Interpretations of the site conditions are based on the results of our review of available information, and the results of our site reconnaissance, subsurface explorations, and laboratory testing. 2.1 General Geologic Conditions The Edmonds area is part of the central Puget Lowland geographic region, which was repeatedly covered by ice sheets during the Pleistocene geologic epoch. According to information obtained from the Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington (Minard 1983), near -surface deposits in the vicinity of the project site consist primarily of deposits of the Whidbey Formation and transitional beds. The Whidbey Formation typically consists of bedded, compact, commonly oxidized, medium -to - coarse -grained sand. Contorted bedding is a common internal structural feature of this formation. Peat beds or organic -rich sand layers may be present locally in the upper part of this formation. Soil defined as transitional beds typically consists of mostly massive, thick or thin beds and laminae of medium to dark gray clay, silt, and fine to very fine sand. Some layers of peaty sand and gravel may be present in the lower part of this unit. Transitional beds were deposited in lakes and fluvial systems prior to the advance of a glacier. This unit typically exhibits low permeability. Additionally, the Preliminary Surficial Geologic Map of the Edmonds East and Edmonds West Quadrangles, Snohomish and King Counties, Washington (Smith 1975) identifies Vashon Till to be present in the vicinity of the project area. Soil defined as Vashon Till typically consists of a heterogeneous, non -sorted mixture of subrounded boulders, cobbles, gravel, and sand in a matrix of silt and clay. The heterogeneous nature of the till is a result of it being mixed and transported before being deposited, overridden, and compacted by the weight of an advancing glacier. This unit typically exhibits low permeability and high shear strength. Anecdotal information indicates that the site was historically occupied by a wetland, which was filled to create useable space. As a result of this, peat and fill soils should be anticipated at the site. 2.2 Surface Conditions The project site is located in Edmonds, Washington, at the existing Civic Center Playfield. Development in the vicinity of the project site is primarily residential in nature east of 61h Avenue North and is mixed commercial and residential to the west of 61h Avenue North. The project site is generally level, and existing site features include sports fields, basketball courts, tennis courts, and a building that is currently being used by the Boys & Girls Club. Geotechnical Engineering Report 1548002.010.OftC c U B Civic Center Playfield Improvements October 30, 20 GJ 2-1 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 2.3 Subsurface Soil Conditions Subsurface conditions at the project site were explored by advancing and sampling seven exploratory borings (B-1 through B-7) on July 18 and 19, 2017, two exploratory test pits (TP-1 and TP-2) on July 21, 2017, and five exploratory test pits (TP-1-18 through TP-5-18) on March 5, 2019. (The designations for TP-1-18 through TP-5-18 were defined in 2018 but these test pits were excavated in 2019. As a result, "-18" in the test pit designation does not indicate the year in which the test pit was excavated.) Exploratory borings B-1 through B-6 were each advanced to a depth of about 21.5 ft below the ground surface (bgs) and boring B-7 was advanced to a depth of about 11.5 ft bgs. The test pits were excavated to depths ranging from about 6 to 10 ft bgs. The approximate locations of the exploratory borings and test pits are shown on Figure 2. A discussion of field exploration procedures, together with edited logs of the exploratory borings and test pits, is presented in Appendix A. A discussion of laboratory test procedures and the laboratory test results are presented in Appendix B. Appendix C includes boring logs from previous explorations by others in the vicinity of the project site. Subsurface conditions in all explorations with the exception of B-1 and B-2 were observed to generally consist of very loose to dense transitional beds, consisting of sand with variable silt and gravel content that extends to the maximum depths explored. It should be noted that in borings B-4, B-6, and test pits TP-1, TP-2-18, TP-3-18, TP-4-18, and TP-5-18 very loose peat was encountered with thickness ranging from about 1% to 8 ft. Due to the sampling interval used in the exploratory borings, it is possible that thin peat lenses may exist at the locations of exploratory borings that did not appear to encounter peat. It should also be noted that hard silt was encountered in boring B-6 from 18 ft bgs extending to the maximum depth explored (21.5 ft). Subsurface conditions in borings B-1 and B-2 were observed to consist of about 5 to 7.5 ft of loose to dense fill, generally consisting of very silty sand to very sandy silt with gravel and wood, underlain by dense to very dense glacial till, consisting of silty to very sand with gravel that extends to the maximum depth explored (21.5 ft). 2.4 Groundwater Conditions At the time of our field investigation in July 2017, and March 2019, groundwater was observed in all of our borings and test pits with the exception of borings B-1 and B-7, and test pit TP-3-18. At the time of drilling, piezometers were installed in borings B-1 through B-6. The groundwater measurements that were recorded at the time of exploration are presented in the following table. Geotechnical Engineering Report Civic Center Playfield Improvements 2-2 1548002.010.0ft C S U B October 30, 20 G Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Table 1. Depth to Groundwater Summary Exploration Depth to Groundwater (ft bgs) Designation At Time of Exploration B-1 Not Observed B-2 4.5 B-3 2.5 B-4 3.8 B-5 3 B-6 3 B-7 Not Observed TP-1 3* TP-2 4* TP-1-18 4 TP-2-18 4 TP-3-18 Not Observed TP-4-18 4.5 TP-5-18 4 *While seepage was not evident in test pits TP-1 and TP-2 until depths of 5 and 8 ft respectively, the soil was observed to be wet at 3 and 4 ft bgs. Therefore we recommend using a depth to groundwater as reported in the table above. Wet season groundwater monitoring is currently ongoing, and therefore complete information as to the depth to wet season groundwater levels is not currently available. Until additional information becomes available, we recommend conservatively assuming a depth do groundwater of 2 ft for design purposes. The groundwater conditions reported herein are for the specific locations and dates indicated, and therefore, may not necessarily be indicative of other locations and/or times. Furthermore, it is anticipated that groundwater conditions at the project site will vary depending on local subsurface conditions, the weather, and other factors. It is likely that the highest groundwater levels will occur in the winter/spring months. Geotechnical Engineering Report 1548002.010.ORCSUB Civic Center Playfield Improvements October 30, 20 G 2-3 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 3.0 SEISMIC CONSIDERATIONS The Pacific Northwest is seismically active and the project site could be subject to ground shaking from a moderate to major earthquake. Consequently, moderate levels of earthquake shaking should be anticipated during the design life of the project, and the proposed improvements should be designed to resist earthquake loading using appropriate design methodology. 3.1 Site Classification and Seismic Design Parameters Seismic site class is used to estimate ground motion at a site during a design earthquake and dictates the level of design effort with respect to seismic design. We understand seismic design of the proposed structures might be in accordance with the 2015 International Building Code (IBC). Due to the presence of very loose peat in the vicinity of the proposed building, the site has been identified as site class F. However, if the peat is removed and replaced as recommended in subsequent sections of this report for site preparation and earthwork, site class D can be used to estimate ground motion at the site during a design earthquake. The seismic design parameters in Table 2 were obtained from US Geological Survey (USGS) seismic design maps for the IBC/ASCE 7 2,475-year (2 percent in 50-year exceedance probability) design earthquake and site class D. The design earthquake moment magnitude (M) was determined by selecting the earthquake magnitude with the largest hazard contribution as shown in the seismic hazard deaggregation performed by USGS. Table 2. Seismic Design Parameters Site Class M PGA (g) SS (g) Sl (g) Fa Fv FPGA TIL (s) D 7.11 0.515 1.272 0.498 1.000 1.502 1.000 6 Fa, Fv = acceleration (0.2-second period) and velocity (1.0-second period) site coefficients, respectively. FPGA = peak ground acceleration coefficient. M = design earthquake moment magnitude. PGA = peak ground acceleration. Ss, S, = 0.2-second and 1.0-second period spectral accelerations, respectively. TL = long period transition. 3.2 Liquefaction Potential Soil liquefaction is generally limited to granular soils or non -plastic silts located below the water table that are in a relatively loose, unconsolidated condition at the time of a large, nearby earthquake. Based on the available data and our experience on similar sites, we anticipate the soils at the site could experience soil liquefaction during a design earthquake and that liquefaction induced settlements could be on the order of 4 inches or more. In order to adequately assess liquefaction potential, one or more borings should be advanced through the zone of liquefiable soil if the zone Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 3-1 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates extends less than 80 ft bgs or to a depth of 80 bgs if the liquefiable soil extends beyond this depth. If necessary, LAI is available to provide liquefaction susceptibility analysis upon request. Geotechnical Engineering Report Civic Center Playfield Improvements 3-2 1548002.010.0b October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 4.0 CONCLUSIONS AND RECOMMENDATIONS Based upon evaluation of existing data and the data collected during this investigation, the project design faces certain challenges due to the presence of peaty soils and shallow groundwater conditions; however, it is our opinion that subsurface conditions at the site are suitable for the proposed project, provided the recommendations contained herein are incorporated into the project design. The following sections present conclusions and recommendations regarding site preparation and earthwork, reuse of onsite soils, wet weather earthwork, fill placement and compaction, retaining walls, luminaire foundations, uplift resistance of structures below the groundwater table, an assessment of the feasibility of infiltrating stormwater, and shallow foundation support for the proposed restroom and concession building. 4.1 Site Preparation and Earthwork Site preparation and earthwork will include excavating within the footprint of the proposed building, shade pavilion, scramble wall, skate park, walkways, view terraces, berms, and sports courts and fields. 4.1.1 Site and Subgrade Preparation As noted in previous sections of this report, much of the site in underlain by very loose peaty soils extending to depths ranging from to 2% to 13 ft bgs. Peaty soils are not anticipated to provide adequate support beneath any structures that are not tolerant to settlement and should therefore be removed where present. Because the peat is currently overlain by existing fill, it may not be immediately apparent if peat is present at the location of the proposed structures. Figure 3 presents a comparison of the existing grades, proposed grades, and the elevation of the bottom of the peat that was observed at the location of each exploration completed by LAI and others in the vicinity of the site. Additional information can be obtained at the location of settlement -tolerant structures by potholing after existing features have been removed. Information from Figure 3 is presented in tabular form, in Table 3 below. Geotechnical Engineering Report Civic Center Playfield Improvements 4-1 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Table 3. Comparison of Existing, Proposed, and Bottom of Peat Grades Existing Proposed Elevation Exploration Grade Grade of Bottom Designation Elevation Elevation of Peat (ft) (ft) (ft) t B-1 74.8 74.8 N/A B-2 81.4 81.4 N/A B-3 84.1 85.1 N/A B-4 87.7 87.7 74.7 B-5 84.2 85.0 N/A B-6 79.0 78.6 73.5 (Sports Courts) B-7 74.3 74.3 N/A TP-1 79.5 80.0 77.0 (Skate Park) TP-2 83.5 84.5 N/A TP-1-18 84.8 85.7 N/A TP-2-18 83.0 84.0 79.0 (Restroom Building) TP-3-18 81.3 82.5 76.8 (Skate Park) TP-4-18 78.5 79.6 76.0 (Sports Courts) TP-5-18 78.6 84.3 76.1 (Scramble Wall) B-1 (Geotest 2014) 88.0 88.0 N/A B-6 (Geotest 2014) 86.0 86.0 77.5 The purpose of removing the unsuitable peaty material is to provide uniform support for the proposed structures/improvements. The limits of the overexcavation beneath the proposed structures/improvements should extend laterally beyond the edges of the proposed structures/improvements a distance equal to one-half the depth of the excavation below the base of proposed structure/improvement. Alternatively, overexcavations could be backfilled to the design footing elevation with lean concrete or foundations could be extended to bear on medium dense to dense undisturbed native soil. If lean concrete is used to backfill the overexcavation, the limits of the overexcavation do not need to extend beyond the width of the proposed structure/improvement. Geotechnical Engineering Report 1548002.010.O�C��� Civic Center Playfield Improvements October 30, 20 G 4-2 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates All existing topsoil, organic and man-made debris, and other deleterious material should be cleared and stripped from all areas to be occupied by the proposed improvements. Prior to placement of any structural fill, the exposed subgrade under all areas to be occupied by soil -supported floor slabs, spread or continuous foundations, and paved areas should be compacted to a firm, dense, and unyielding condition. The subgrade should be sufficiently compacted such that the upper 12 inches of the subgrade is compacted to at least 95 percent of the maximum dry density (MDD) as determined using ASTM International (ASTM) test method D1557 (modified Proctor). The compacted surface should then be proof rolled with a fully -loaded dump truck, large self-propelled vibrating roller, or equivalent piece of equipment to identify possible loose or soft soil deposits. Proof rolling should be carefully observed by geotechnical personnel. Areas exhibiting significant deflection, pumping, or weaving that cannot be readily compacted should be overexcavated to firm soil. Overexcavated areas should be backfilled with compacted granular material, in accordance with subsequent recommendations for engineered fill materials that are presented in this report. 4.1.2 Engineered Fill Materials Table 4 outlines engineered fill materials recommended for this project. All engineered fill materials, except gravel backfill for pipe zone and bedding, should be placed and compacted in accordance with Section 2-03.3(14)C, Method C of the 2020 WSDOT Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Specifications). Gravel backfill for pipe zone bedding shall be placed and compacted in accordance with WSDOT Specifications 7-08.3(2)C and gravel backfill for pipe zone backfill should be placed in accordance with WSDOT Specifications 7-08.3(3). The maximum dry density and optimum moisture content may also be determined by the ASTM D 1557 test procedure (modified Proctor). Geotechnical Engineering Report Civic Center Playfield Improvements 4-3 1548002.010.0b October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Table 4. Engineered Fill Materials Engineered Fill Type Specification Application Granular Fill Gravel Borrow - WSDOT Specs . Within 6 inches of shallow 9-03.14(1) foundations Select Borrow - WSDSubOT Specs . Structural Fill grade overexcavation and 9-03.14(2) recompaction Gravel Backfill for Pipe Zone and • Pipe Zone Fill WSDOT Specs 9-03.12(3) Bedding • Pipe Bedding Bank Run Gravel for Trench Backfill WSDOT Specs 9-03.19 • Trench backfill above pipe zone Crushed Surfacing Base Course - Base Course • WSDOT Specs 9-03.9(3) Pavement base course Crushed Surfacing Top Course - Top Course WSDOT Specs 9-03.9(3) • Pavement top course 4.1.3 Reuse of Site Soil Soil generated from onsite cuts and/or excavations is expected to consist primarily of transitional bed deposits, peat, and sand with varying silt content. Some of the soils encountered at the project site are considered to be moisture sensitive due to their relatively high fines content; however, less silty material may be reused with proper moisture conditioning. Reuse of highly organic site soils is not recommended beneath footings or behind retaining walls. If the onsite soil generated from cuts and/or excavations at the project site are not suitable for use as fill, it should be disposed of at an offsite location or placed in landscaped areas of the site where several inches of post -construction settlement would be tolerable. Imported fill material, if needed, should meet the requirements of Granular Fill, as detailed in Section 4.1.2 of this report. 4.1.4 Wet Weather Earthwork Considerations As described above, some of the onsite soil is considered to be moisture sensitive. Earthwork during wet weather will be difficult and could result in excessive soil disturbance and subgrade damage. It should be the responsibility of the contractor to prevent excessive erosion and ground destabilization during all earthwork activities. If earthwork is performed during wet weather, the amount of fines allowed in structural fill should be reduced to 5 percent or less. The contractor may need to place Granular Fill during wet weather to provide a stable working platform. In addition, if fill is to be placed or earthwork is performed in wet weather or under wet conditions, the contractor should: • Perform earthwork in small sections • Slope excavated surfaces to promote runoff Geotechnical Engineering Report 1S48002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-4 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates • Limit construction traffic over unprotected soil • Limit the size and type of construction equipment used • Remove wet surficial soil prior to commencing fill placement each day • Seal the exposed level ground surface by rolling with a smooth drum compactor or rubber - tired roller at the end of each working day • Track -walk sloped ground at the end of each day so grouser marks are on -contour • Provide upgradient perimeter ditches or low earthen berms and use temporary sumps to collect runoff and prevent water from ponding and damaging exposed subgrades • Stabilize the soil with an additive (such as lime or cement kiln dust) to allow its use in wet weather. 4.1.5 Construction Dewatering In the past, the City attempted to install a sanitary sewer in the roadway adjacent to the east side of Civic Center Playfield. The City's attempt to install the sewer was unsuccessfully due to difficulty in maintaining the stability of trench excavations due to the presence of shallow groundwater and sandy soils. At the time of our field exploration program in mid -July, groundwater was observed at all locations explored with the exception of borings B-1 and B-7 at depths ranging from approximately 2.5 to 8 ft bgs. Should the proposed excavations extend significantly below the groundwater table in sandy soils, the designer and contractor should be prepared for a considerable dewatering effort. Open sump pumping from the excavation may be sufficient where excavation depths extend down to the groundwater table, assuming the excavation walls remain stable. Wells or well points may be necessary in portions of the project site where substantial pockets of groundwater are encountered and/or the excavation walls become unstable. Well points are a viable option to lower groundwater to a depth of about 17 ft below the pump elevation. The contractor should be responsible for the design, installation, monitoring, and maintenance of any required dewatering system(s). If wells or well points are necessary, the contractor should be required to submit a dewatering plan prepared by a registered professional engineer or hydrogeologist for review by the City's design team prior to implementation. 4.1.6 Temporary Excavation Slopes It is anticipated that temporary excavations for the proposed improvements will be generally in very loose to dense transitional bed deposits, peat, or sand with varying silt content. A heavy-duty, hydraulic excavator with sufficient reach should be able to excavate trenches to the depths planned. While not encountered in our explorations, boulders, large wood pieces, and other debris may be present at the project site and the contractor should be prepared to handle and dispose of such oversized or unsuitable material if encountered. Geotechnical Engineering Report Civic Center Playfield Improvements 4-5 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Given the nature of the onsite soils and the shallow groundwater conditions at the project site, care must be taken during construction to maintain stability of open excavations. Stability of excavations and safety of workers are responsibilities of the contractor. The onsite soils should not be expected to support unbraced vertical excavations. Excavation sidewalls may either be laid back by sloping or benching or braced. Trench excavation should conform to the requirements of Section 7-08.3(1)A of the 2020 Washington State Department of Transportation (WSDOT) Standard Specifications for Road, Bridge and Municipal Construction (WSDOT 2020). Temporary excavations in excess of 4 ft deep should either be shored or sloped in accordance with Safety Standards for Construction Work, Part N, located in Chapter 296-155 of the Washington Administrative Code (WAC). In the absence of groundwater seepage, the near surface soils at the project site generally classify as Type C soil per Chapter 296-155 of the WAC. The prescriptive maximum allowable excavation slope for Type C soils is 1%H:1V (horizontal to vertical). If groundwater seepage is present, flatter slopes, temporary shoring, and/or dewatering may be required. While trench boxes may provide adequate worker safety, use for this project may result in unacceptable displacements of adjacent soils and damage to adjacent pavement or structures. In areas where displacement of adjacent soils and damage to adjacent pavement or structures is unacceptable, a temporary shoring system should be used to reduce potential adjacent soil displacements. The temporary shoring system should be designed by a structural engineer licensed in the state of Washington. The parameters provided in the following table can be utilized for design of temporary shoring installed above the water table. The temporary shoring design should be submitted to the City's design team for review prior to construction. Table 5. Recommended Soils Parameters for Design of Temporary Shoring Moist Unit Weight Cohesion Internal Angle of Friction (pcf) (psf) (degrees) 125 0 32 pcf = Pounds per cubic foot psf = Pounds per square foot 4.2 Stormwater Infiltration While wet -season groundwater monitoring is ongoing, current data indicates that the depth to seasonal high groundwater is approximately 2 ft below existing grade. Because of the observed shallow groundwater at the site, it is our opinion that it will not be possible to maintain adequate separation from the groundwater table, and therefore, stormwater infiltration is considered to be infeasible at this site even though the limited amount of soil above the groundwater table is generally suitable for infiltration. Geotechnical Engineering Report Civic Center Playfield Improvements 4-6 1548002.010.0b October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 4.3 Foundations The following sections provide recommendations for foundation design. 4.3.1 Shallow Foundation Support Foundation support for the proposed restroom and concession building may be provided by continuous or isolated spread footings that are founded on medium dense to dense undisturbed native soil, well -compacted Structural Fill, or lean concrete extending to undisturbed native soil. Our explorations in the vicinity of the proposed building encountered fill underlain by very loose peat extending to approximately elevation 79 ft (4.5 ft below existing grade). Peaty soils in the vicinity of the proposed building should be removed and replaced in accordance with the recommendations in Section 4.1.1 of this report. Bearing soil disturbed during foundation excavation should either be properly recompacted or removed. All soil directly below footings should be compacted to at least 95 percent of maximum dry density (ASTM D1557) prior to placement of forms, reinforcing steel, and concrete. All continuous and isolated spread footings should have minimum widths of 18 and 24 inches, respectively, and should be founded a minimum of 18 inches below the lowest adjacent final grade. Assuming the above foundation support criteria are satisfied, continuous or isolated spread footings founded directly on medium dense to dense undisturbed native soil or properly compacted structural fill extending down to medium dense to dense undisturbed native soil, may be proportioned using a maximum net allowable soil bearing pressure of 2,000 pounds per square ft (psf). The term "net allowable bearing pressure" refers to the pressure that can be imposed on the soil at foundation level resulting from the total of all dead plus live loads, exclusive of the weight of the footing or any backfill placed above the footing. The net allowable bearing pressures may be increased by one-third for transient wind or seismic loads. Passive earth pressures that develop against the sides of the building foundations, in conjunction with friction developed between the base of the footings and the supporting subgrade, will resist lateral loads transmitted from the structure to its foundation. For design purposes, the passive resistance of well -compacted fill placed against walls or the sides of foundations may be considered equivalent to a fluid with a density of 345 pounds per cubic ft. The recommended value includes a safety factor of about 1.5 and is based on the assumption that the ground surface adjacent to the structure is level in the direction of movement for a distance equal to or greater than twice the embedment depth. The recommended value also assumes drained conditions that will prevent the buildup of hydrostatic pressure in the compacted fill. In design computations, the upper 12 inches of passive resistance should be neglected if the soil is not covered by floor slabs or pavement. If future plans call for the removal of the soil providing resistance, the passive resistance should not be considered. Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-7 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates An allowable coefficient of friction between concrete and soil of 0.35, applied to vertical dead loads only, may be used to calculate the resistance to sliding at the base of the foundation elements bearing on undisturbed native soil or well -compacted Structural Fill. However, if passive and frictional resistance are considered together, one-half of the recommended passive soil resistance value should be used because larger strains are required to mobilize the passive soil resistance as compared to frictional resistance. A safety factor of about 1.5 is included in the base friction design value. We do not recommend increasing the coefficient of friction to resist seismic or wind loads. 4.3.2 Foundation Settlement Settlement of shallow foundations depends on foundation size and bearing pressure, as well as the strength and compressibility characteristics of the underlying soil. Assuming construction is accomplished as previously recommended and for the maximum allowable soil bearing pressure recommended above, we estimate the total settlement of foundations should be less than about 1 inch and differential settlement between two adjacent load -bearing components supported on competent soil should be less than about % inch. The soil response to applied stresses caused by structural and other loads is expected to be predominately elastic in nature, with most of the settlement occurring during construction as loads are applied. This settlement estimate assumes that any peat present beneath foundations has been properly removed and replaced with well -compacted Structural Fill as recommended herein. 4.3.3 Concrete Slabs on Grade Conventional slab -on -grade floor construction is considered feasible for the proposed construction. The floor slab may be supported on medium dense to dense undisturbed native soil or properly placed and compacted Structural Fill that is placed on top of the medium dense to dense undisturbed native soil provided: 1) the slab subgrade is proof rolled in the presence of a qualified geotechnical engineer and areas exhibiting significant deflection, pumping, or weaving that cannot be readily compacted are overexcavated to firm soil and the overexcavated areas are backfilled with properly compacted Structural Fill as described in Section 4.1.2 and 2) the proof rolled slab subgrade is compacted to a firm, dense, and unyielding surface. Prior to slab construction, prepared slab subgrade should be checked by a qualified geotechnical engineer for any loose and/or disturbed areas. If detected, these areas should be overexcavated and compacted as recommended above. A minimum of 4 inches of Crushed Surfacing Base Course as described in Section 4.1.2 should be placed beneath slab -on -grade floors to act as a capillary break layer. A condensation barrier, such as visqueen or a membrane, should be placed beneath slab -on -grade floors to prevent condensation of water vapor on the bottom of the floor slab and wicking up through the floor slab. The condensation barrier should consist of a minimum 10-mil membrane with tape -sealed joints. The American Concrete Institute (ACI) guidelines recommend that 4 inches of compacted granular material, such as Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-8 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Crushed Surfacing Top Course as described in Section 4.1.2 be placed over the barrier to facilitate curing of the concrete floor slab and to protect the vapor barrier. The ACI no longer recommends sand for the protection layer. If moisture control within the building is critical, we recommend an inspection of the condensation barrier to verify that all openings have been properly sealed. Exterior concrete slabs -on -grade, such as sidewalks, may be supported directly on medium dense to dense undisturbed native soil or properly placed and compacted Structural Fill; however, long-term performance will be enhanced if exterior slabs are placed on a layer of clean, durable, free -draining granular material. 4.3.4 Foundation and Site Drainage To reduce the potential for groundwater to seep into interior spaces and prevent the buildup of hydrostatic pressure against subterranean walls, we recommend that an exterior footing drain system be constructed around the perimeter of the building foundation. The drain should consist of a minimum 4-inch diameter perforated pipe, surrounded by a minimum 12 inches of filtering media and sloped to carry water to a suitable collection and discharge system. The filtering media may consist of open -graded drain rock wrapped by a non -woven geotextile fabric (such as Mirafi 140N, Synthetic Industries 351, or equivalent). The drainage backfill should contain less than 3 percent by weight passing the US Standard No. 200 sieve, based on a wet sieve analysis of that portion passing the US Standard No. 4 sieve. The invert of the footing drain pipe should be placed at approximately the same elevation as the bottom of the footing or 12 inches below the adjacent floor slab grade, whichever is deeper, so that water will not accumulate behind walls or seep through walls or floor slabs. The footing drain should discharge to an approved drain system and include cleanouts to allow periodic maintenance and inspection. Positive surface gradients should be provided adjacent to the proposed structures to direct surface water away from the foundation and toward suitable discharge facilities. Roof drainage should not be introduced into the perimeter footing drains, but should be discharged directly to the stormwater collection system or other appropriate outlet. Pavement and sidewalk areas should be sloped and drainage gradients should be maintained to carry all surface water away from the building towards the local stormwater collection system. Surface water should not be allowed to pond and soak into the ground surface near the building during or after construction. 4.4 Retaining Walls Provided all of the unsuitable material beneath the proposed retaining walls is removed and replaced in accordance with the recommendations in Section 4.1.1, retaining walls at the site can be designed for a maximum net allowable bearing pressure of 2,000 psf. The net allowable bearing pressures may be increased by one-third for transient wind or seismic loads. Geotechnical Engineering Report 1S48002.010.O�C��� Civic Center Playfield Improvements October 30, 20 G 4-9 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates For design purposes, the passive resistance of well -compacted fill placed against walls may be considered equivalent to a fluid with a density of 345 pounds per cubic ft. The recommended value includes a safety factor of about 1.5 and is based on the assumption that the ground surface adjacent to the wall is level in the direction of movement for a distance equal to or greater than twice the embedment depth. The recommended value also assumes drained conditions that will prevent the buildup of hydrostatic pressure in the compacted fill. In design computations, the upper 12 inches of passive resistance should be neglected if the soil is not covered by pavement. If future plans call for the removal of the soil providing resistance, the passive resistance should not be considered. An allowable coefficient of friction between concrete and soil of 0.35, applied to vertical dead loads only, may be used to calculate the resistance to sliding at the base of the retaining wall foundation elements bearing on undisturbed native soil or well -compacted Structural Fill. However, if passive and frictional resistance are considered together, one-half of the recommended passive soil resistance value should be used because larger strains are required to mobilize the passive soil resistance as compared to frictional resistance. A safety factor of about 1.5 is included in the base friction design value. We do not recommend increasing the coefficient of friction to resist seismic or wind loads. Assuming retaining wall footings are designed as described above total settlement of foundations should be less than about 1 inch and differential settlement between two adjacent load -bearing components supported on competent soil should be less than about % inch. The soil response to applied stresses caused by structural and other loads is expected to be predominately elastic in nature, with most of the settlement occurring during construction as loads are applied. The magnitude of lateral earth pressures that develop against retaining walls will depend upon the inclination of any adjacent slopes, type of backfill, degree of wall restraint, method of backfill placement, degree of backfill compaction, drainage provisions, magnitude and location of any adjacent surcharge loads, and the degree to which the wall can yield laterally during or after placement of backfill. When a wall is restrained against lateral movement or tilting, the soil pressure exerted is the at -rest soil pressure. Such wall restraint may develop if a rigid structural network is constructed prior to backfilling or if the wall is inherently stiff or is otherwise restrained from rotation. In contrast, active soil pressure will be exerted on a subsurface structure or wall if its top is allowed to rotate or yield a distance of approximately 0.001 times its height or greater. We recommend that non -restrained (yielding) walls with level backfill under drained conditions be designed for an equivalent fluid density of 35 pounds per cubic ft (pcf) for active soil conditions. Nonyielding (restrained at the top) walls with level backfill under drained conditions should be designed for an equivalent fluid density of 55 pcf for at -rest conditions. For undrained conditions, yielding walls with level backfill should be designed to resist an equivalent fluid density of 80 pcf. Nonyielding walls with level backfill under undrained conditions should be designed for an equivalent fluid density of 90 pcf. The equivalent fluid densities recommended for use under undrained conditions include hydrostatic pressure. Geotechnical Engineering Report Civic Center Playfield Improvements 4-10 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates The above recommendations regarding active and at -rest earth pressures assume that the backfill placed against the retaining walls will consist of properly compacted structural fill, and no adjacent surcharge loads. If the retaining walls will be subjected to the influence of surcharge loading within a horizontal distance equal to or less than the height of the walls, the walls should be designed for the additional horizontal pressure. For rigid walls, a uniformly distributed lateral pressure of 0.43 times the surcharge pressure should be included. For walls free to rotate during loading, a uniformly distributed lateral pressure of 0.27 times the surcharge pressure should be included. Dynamic lateral earth pressures should be included in the design of retaining walls. A uniform lateral pressure distribution of 11H (where H is the vertical height of the wall in feet) should be added to the static lateral earth pressures for all non -restrained (yielding) walls with a level backslope. The recommended lateral earth pressure assumes that the wall will be free to rotate and translate a small amount during a strong motion earthquake. The earthquake -induced lateral earth pressure described in this section is based upon the Mononobe-Okabe simplified method described in ASCE 7, which is referenced in 2015 International Building Code. LAI should be contacted for additional recommendations if the project will include a yielding wall with a non -level backslope, or if the project will include restrained wall. 4.5 Buoyancy Forces on Structures Below the Groundwater Table As described in previous sections of this report, for the purposes of design we recommend an assumed depth to groundwater of approximately 2 ft bgs. Buried tank -like structures (such as underground utility vaults) will experience an upward buoyant force when the groundwater level around the outside of the structure is higher than the fluid level inside the structure. These upward forces may potentially damage the bottom of the structure if it is not properly designed to resist such forces. The weight of the structure, the weight of soil directly above the extended base of the structure (if any), and the soil friction on the walls of a structure without an extended base will act to resist uplift forces due to hydrostatic pressure acting on the base of the structure. Extending the bases of the lift station and grease separator foundations beyond the outside of their perimeters would increase the uplift resistance of these structures. If the structure does not have an extended base and it is backfilled with properly compacted granular fill, the uplift resistance provided by the soil friction on the walls of the structure can be estimated using the following formula: FS = 0.0121-112 + 0.024HiH2+ 0.0061-122 Where: FS = shearing resistance of soil to wall (in kips per foot of wall) H1 = distance between ground surface and top of groundwater table (in feet) H2 = distance between top of groundwater table and bottom of structure (in feet). Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-11 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates To compute the resisting force provided by properly compacted granular backfill material surrounding a structure with an extended base, the weight of the soil directly above the extended base can be added directly to the shearing resistance of the soil. Soil unit weights of 120 pcf and 58 pcf should be assumed above and below the groundwater elevation, respectively. The uplift resistance provided by the shearing resistance of the soil can be estimated using the following formula: Fsb = 0.0181-112 + 0.036H1H2+ 0.0091-122 Where: Fsb = shearing resistance of soil (in kips per foot of wall) H1 = distance between ground surface and top of groundwater table (in feet) H2 = distance between top of groundwater table and bottom of structure (in feet). 4.6 Pavement Design Based on the results of our subsurface investigation and our experience on sites with similar subgrade soil, it is our opinion that flexible pavements constructed near the site on a subgrade that has been compacted to a dense and unyielding condition and is free of soft soils (or peat), or on properly compacted structural fill placed directly on a subgrade that has been compacted to a dense and unyielding condition, could be designed using a California Bearing Ratio (CBR) of about 10 percent. Pavement sections should be constructed on a subgrade that has been scarified to a depth of 1 ft and recompacted to at least 95 percent of the MDD. Our subsurface investigation encountered peat in borings B-4, B-6, and test pits TP-1, TP-2-18, TP-3-18, TP-4-18, and TP-5-18 with thickness ranging from about 1% to 8 ft. This material is not anticipated to provide adequate support for the proposed paved areas and should be removed and replaced as described in Section 4.1.1. In areas where unsuitable soil is encountered during construction, pavement subgrade should be overexcavated and replaced with a minimum 1 ft of uniform, firm, and unyielding Structural Fill as described in Section 4.1.2. The pavement section recommendations provided in Table 6 assume a 20-year design life and an assumed maximum equivalent single -axle load (ESAL) of 50,000 for the light duty section and 500,000 for the heavy-duty section. The rigid pavement recommendation assumes a 20-year design life, and that the pavement will consist of jointed plain concrete pavement (JPCP) without load transfer devices and concrete with a 28-day compressive strength of 5,000 psi. Geotechnical Engineering Report Civic Center Playfield Improvements 4-12 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Table 6. Recommended Pavement Sections Pavement Section Type Pavement Thickness Crushed Surfacing Thickness Light duty 3 inches AC 6 inches Heavy duty 4 inches AC 8 inches Rigid Pavement 5 inches PCC 4 inches AC = Asphaltic Concrete PCC = Portland Cement Concrete Asphalt concrete should be Class B aggregate material or hot -mix asphalt class % inch, PG64-22 conforming to Section 5-04 of the 2020 WSDOT Standard Specifications. The asphalt should be compacted to at least 91 percent of the Rice density. Base Course material, as described in Section 4.1.2 should be compacted to at least 95 percent of the MDD (ASTM D1557). The upper 2 inches of crushed surfacing should consist of Top Course, as described in Section 4.1.2 in order to facilitate fine grading of the surface. Prevention of road base saturation is essential for pavement durability; thus, efforts should be made to limit the amount of water entering the base course. 4.7 Light Pole Foundations We understand that light poles are planned along the proposed vehicular path that will run east to west across the northern portion of the site. Design and construction considerations related to the proposed light pole foundations are presented in the following report sections. 4.7.1 Design Considerations We developed the foundation design parameters presented in Table 7 for the soils encountered along the alignment of the proposed path. In boring B-6 and test pit TP-1, peat was encountered to depths ranging from 1.5 to 5 ft bgs. To reflect this difference in subsurface conditions, we have provided additional parameters for luminaire design (see Table 8) for use in the vicinity of the locations where peat was encountered. It should be recognized that there could be some variation in subsurface soil and groundwater conditions between the explorations. Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-13 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates Table 7. Recommended Parameters for Luminaire Foundation Design Allowable Depth Effective Unit Friction Angle Undrained Shear Lateral Bearing (ft) Soil Type Weight' (pcf) (degrees) Strength (psf) Pressure' (psf) 0 to 3 SAND 108 30 NA 1,000 3 to 5 SAND 45 30 NA 1,000 5 to Silty SAND 52 30 NA 1,400 7.5 7.5 to SAND 63 18 35 NA 3,500 18 to Gravelly SAND 72 40 NA 4,500 21.5 Notes: 1) Effective unit weights are based on a groundwater depth of 3 ft bgs. 2) Allowable lateral bearing pressures were developed as recommended in the WSDOT Geotechnical Design Manual (WSDOT 2019). Table 8. Recommended Parameters for Luminaire Foundation Design Vicinity of Boring B-6 and Test Pit TP-1 Allowable Effective Undrained Lateral Unit Friction Shear Bearing Depth Weight' Angle Strength Pressure' (ft) Soil Type (pcf) (degrees) (psf) (psf) 0 to 3 PEAT 75 10 50 500 3to PEAT 12 10 50 500 5.5 5.5 to Silty SAND 57 32 NA 2,500 7.5 7.5 to SAND 65 36 NA 4,200 18 18 to SILT 72 NA 4,000 4,500 21.5 Notes: 1) See Figure 2 for the locations of B-6 and TP-1. 2) Effective unit weights are based on a groundwater depth of 3 ft bgs. 3) Allowable lateral bearing pressures were developed as recommended in the WSDOT Geotechnical Design Manual (WSDOT 2019). 4.7.2 Construction Considerations Standard construction methods for luminaire foundations typically involve drilling a vertical shaft with a single -flight auger rig, placing a steel reinforcing cage into the hole, and filling the hole with concrete. Groundwater should be anticipated at shallow depths during construction. In addition, the saturated, loose to medium dense sand could potentially become unstable and slough into the drilled shaft. Therefore, temporary casing will likely be required to maintain a stable shaft and the contractor should be prepared to install temporary casing when constructing the drilled shaft. If the casing is pulled as concrete is placed, a sufficient head of concrete should be maintained inside the casing to Geotechnical Engineering Report 1548002.010.0b c Civic Center Playfield Improvements October 30, 20 GJ UB 4-14 Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates prevent caving and sloughing of the hole. Alternatively, the casing could be pulled immediately after placement of concrete, provided the hole is topped off after the casing has been removed. A qualified geotechnical engineer should observe the drilled shaft excavation and concrete placement. This will allow the opportunity to confirm conditions indicated by our exploration and/or provide corrective recommendations adapted to conditions revealed during construction. Geotechnical Engineering Report Civic Center Playfield Improvements 4-15 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 5.0 REVIEW OF DOCUMENTS AND CONSTRUCTION OBSERVATIONS We recommend that LAI be retained to review the geotechnical-related portions of the project plans and specifications to determine if they are consistent with the recommendations presented in this report. We also recommend that monitoring, testing, and consultation be provided during construction to confirm that the conditions encountered are consistent with those indicated by our explorations, to provide recommendations should conditions be revealed during construction that differ from those anticipated, and to evaluate whether geotechnical-related construction activities comply with project plans/specifications and the recommendations contained in this report. We would be pleased to provide these services for you. Geotechnical Engineering Report Civic Center Playfield Improvements 5-1 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 6.0 USE OF THIS REPORT LAI prepared this report for the exclusive use of Walker Macy and the City of Edmonds for specific application to the design of the proposed Civic Center Playfield Improvements project in Edmonds, Washington. Use of this report by others or for other projects is at the user's sole risk. Within the limitations of scope, schedule, and budget, our services have been conducted in accordance with generally accepted practices of the geotechnical engineering profession; no other warranty, express or implied, is made as to the professional advice included in this report. The conclusions and recommendations contained in this report are based in part upon the subsurface data obtained from the explorations completed for this study. There may be some variation in subsurface soil and groundwater conditions at the project site, and the nature and extent of the variations may not become evident until construction. Accordingly, a contingency for unanticipated conditions should be included in the construction budget and schedule. If variations in subsurface conditions are encountered during construction, LAI should be notified for review of the recommendations in this report, and revision of such if necessary. If there is a substantial lapse of time between submission of this report and the start of construction, or if conditions change due to construction operations at or adjacent to the project site, we recommend that we review this report to determine the applicability of the conclusions and recommendations contained herein. We appreciate the opportunity to provide geotechnical services on this project and look forward to assisting you during the construction phase of the project. If you have any questions or comments regarding the information contained in this report, or if we may be of further service, please call. Geotechnical Engineering Report Civic Center Playfield Improvements 6-1 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Landau Associates 7.0 REFERENCES Smith, M. 1975. Preliminary Surficial Geologic Map of the Edmonds East and Edmonds West Quadrangles, Snohomish and King Counties, Washington. Geologic Map GM-14. Washington State Department of Natural Resources. WSDOT. 2019. M46-03.11: Geotechnical Design Manual. Washington State Department of Transportation. WSDOT. 2020. M 41-10: Standard: Standard Specifications for Road, Bridge, and Municipal Construction 2016. Washington State Department of Transportation. Geotechnical Engineering Report Civic Center Playfield Improvements 7-1 1548002.010.0b C October 30, 20 G SUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Puget Sound 4- Project Location II II II eta �rF r. II > rr City.. Aim F- \ �I u6.i , �r = ���■ �� sperance Deep Creek N 0 0.5 1 Miles Data Source: Esri 2012 Civic Center LANDAU Playfield Improvements ASSOCIATES Edmonds, Washington to Seattle Spokane Tacoma Ilympia Washington Vicinity Map Figure REIS U Mar 25 20 1 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 0 a \\ � I I I , I I I I — — — _ Daley — 4 — — — i I I I � I �- Q I I Legend B1 Boring Location and Designation TP-1 I9 Test pit Location and Designation 0 a -g LANDAU ASSOCIATES map source: KPFF Land Surve) Civic Center Playfield Improvements Edmonds, Washington — Bell — —# 0 150 300 Scale in Feet ber 2017 Figure Site & Exploration Plan RaU CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 11 P B-7 (Not Observed) S° w B-1 (Not Observed) TP-2 (Not Observed)o� N 84 ` -1/g5 D B-5 1 94— (Not Observed) r TP-3-18 �ti .5(76.83') f (774') �� D ® V B-1 1 -1tK'(Not Observed) t�S 4✓ (78.99') B-3 g J � 87 l \ lo r _ (Not Observed) t\`888 J /75) c B 2 \III�►1 > (Not Observed) TP-1-18 tp p (Not Observed) Ln 85 B-4 J (74.69') 86 89� — J 0 r 19y TP-5-18� I10, �. , � TP-4-18 (75.98')�` I � II ti (73.47')J—I\ ` TP-1 00 — (77.00') Do Legend B-4 74.69' Boring Location and Designation Elevation of Bottom of Peat (feet-NAVD88) TP-4-18 75.98' Test pit Location and Designation Elevation of Bottom of Peat (feet-NAVD88) B-1 75.98 ® Boring Location and Designation (Geotest, 2014) Elevation of Bottom of Peat (feet-NAVD88) LANDAU 14 ASSOCIATES Sources: Walker IMacv, 2019; KPFF Land 0 150 300 Scale in Feet ber 2017; Geotest Services, Inc., 2014 Civic Center Figure Playfield Improvements Comparison of Existing, Proposed, RE3U Edmonds, Washington and Bottom of Peat Grades Mar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX A Field Explorations RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX A FIELD EXPLORATIONS Subsurface conditions at the project site were explored between July 18 and 21, 2017 and on March 5, 2019. The exploration program consisted of advancing and sampling seven exploratory borings (B-1 through B 7) and seven exploratory test pits (TP-1 and TP-2, TP-1-18 through TP-5-18) at the approximate locations illustrated on the Site and Exploration Plan (Figure 2 of this report). (The designations for TP-1-18 through TP-5-18 were defined in 2018 but these test pits were excavated in 2019. As a result, "-18" in the test pit designation does not indicate the year in which the test pit was excavated.) The borings were advanced to depths ranging from about 11% to 21% ft below the existing ground surface (BGS) using the hollow -stem auger exploration technique and the test pits were excavated to depths of about 6 and 10 ft bgs. Under subcontract to Landau Associates, Holocene Drilling, Inc. of Puyallup, Washington advanced the hollow -stem auger borings, test pits TP-1 and TP-2 were excavated by Northwest Excavating and Trucking Company, Inc. of Snohomish, Washington, and test pits TP-1-18 through TP-5-18 were excavated by the City of Edmonds. The locations of the exploratory borings and test pits were located approximately in the field using a handheld GPS unit. The ground surface elevations at the exploration locations were determined based off of a site survey prepared by KPFF. The field exploration program was coordinated and monitored by Landau Associates personnel who also obtained representative soil samples, maintained a detailed record of the observed subsurface soil and groundwater conditions, and described the soil encountered by visual and textural examination. Each representative soil type observed in our exploratory borings and test pits was described using the soil classification system shown on Figure A-1, in general accordance with ASTM International (ASTM) D 2488, Standard Recommended Practice for Description of Soils (Visual -Manual Procedure). Logs of the exploratory borings are presented on Figures A-2 through A-8. Logs of the exploratory test pits are presented on Figures A-9 through A-12. These logs represent our interpretation of subsurface conditions identified during the field exploration program. The stratigraphic contacts shown on the summary logs represent the approximate boundaries between soil types; actual transitions may be more gradual. The soil and groundwater conditions depicted are only for the specific dates and locations reported and, therefore, are not necessarily representative of other locations and times. A further discussion of the soil and groundwater conditions observed is contained in the text portion of this report. Representative grab samples of the soil encountered in the exploratory test pits were obtained as the test pits were excavated. Disturbed samples of the soil encountered in the exploratory borings were obtained at selected intervals using a 1.5-inch inside -diameter split spoon sampler. The sampler was driven up to 18 inches into the undisturbed soil ahead of the drill bit with a 140-lb hammer falling a distance of approximately 30 inches. The number of blows required to drive the sampler for the final A-1 BESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 12 inches of soil penetration, or part thereof, is noted on the boring logs, adjacent to the appropriate sample notation. Samples collected in this manner were taken to our laboratory for further examination and testing. A discussion of laboratory test procedures and the laboratory test results are presented in Appendix B. Upon completion of excavating and sampling, the test pits were backfilled and compacted in lifts with the excavated material. Upon completion of drilling and sampling, piezometers were installed in borings B-1 through B-6 in general accordance with the requirements of Washington Administrative Code (WAC) 173-160 and boring B-7 was decommissioned in general accordance with this same WAC. A-2 BESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT MAJOR DIVISIONS Soil Classification System USCS GRAPHIC LETTER SYMBOL SYMBOL' TYPICAL DESCRIPTIONS 12)(3) GRAVEL AND CLEAN GRAVEL p p p o GW Well -graded gravel; gravel/sand mixture(s); little or no fines J N GRAVELLY SOIL (Little or no fines) Poorly graded ravel; ravel/sand mixtures little or no fines Y9 9 9 O; o O o. q o GP GRAVEL WITH FINES GM p (More than 50% of Silty gravel; gravel/sand/silt mixture(s) Lu E 'w coarse fraction retained (Appreciable amount of Qo N on No. 4 sieve) fines) GC Clayey gravel; gravel/sand/clay mixture(s) �� O LO z° SAND AND CLEAN SAND SW Well -graded sand; gravelly sand; little or no fines ul ca to rC,SP SANDY SOIL (Little or no fines) Poorly graded sand; gravelly sand; little or no fines SAND WITH FINES SM Q o OU 2 (More than 50% of fraction Silty sand; sand/silt mixture(s) g coarse passed (Appreciable amount of SC through No. 4 sieve) fines) Clayey sand; sand/clay mixture(s) ML Inorganic silt and very fine sand; rock flour; silty or clayey fine sand or clayey silt with slight w r �, o ^ N SILT AND CLAY plasticity Inorganic clay of low to medium plasticity, gravelly clay; sandy CL a`) N w � (Liquid limit less than 50) clay; silty clay; lean clay > Z E a) OIL Organic silt; organic, silty clay of low plasticity L •— o MH Inorganic silt; micaceous or diatomaceous fine sand U, o m w SILT AND CLAY CH w g z Inorganic clay of high plasticity, fat clay Z E LL (Liquid limit greater than 50) OH Organic clay of medium to high plasticity; organic silt HIGHLY ORGANIC SOIL PT Peat; humus; swamp soil with high organic content GRAPHIC LETTER OTHER MATERIALS SYMBOL SYMBOL TYPICAL DESCRIPTIONS PAVEMENT '•':: AC Or PC Asphalt concrete pavement or Portland cement pavement ROCK RK Rock (See Rock Classification) WOOD WD Wood, lumber, wood chips DEBRIS O O O DB Construction debris, garbage Notes: 1. USCS letter symbols correspond to symbols used by the Unified Soil Classification System and ASTM classification methods. Dual letter symbols (e.g., SP-SM for sand or gravel) indicate soil with an estimated 5-15% fines. Multiple letter symbols (e.g., ML/CL) indicate borderline or multiple soil classifications. 2. Soil descriptions are based on the general approach presented in the Standard Practice for Description and Identification of Soils (Visual -Manual Procedure), outlined in ASTM D 2488. Where laboratory index testing has been conducted, soil classifications are based on the Standard Test Method for Classification of Soils for Engineering Purposes, as outlined in ASTM D 2487. 3. Soil description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each soil type and is defined as follows: Primary Constituent: > 50% - "GRAVEL," "SAND," "SILT," "CLAY," etc. Secondary Constituents: > 30% and < 50% - "very gravelly," "very sandy," "very silty," etc. > 15% and < 30% - "gravelly," "sandy," "silty," etc. Additional Constituents: > 5% and < 15% - "with gravel," "with sand," "with silt," etc. < 5% - "with trace gravel," "with trace sand," "with trace silt," etc., or not noted. 4. Soil density or consistency descriptions are based on judgement using a combination of sampler penetration blow counts, drilling or excavating conditions, field tests, and laboratory tests, as appropriate. Drilling and Sampling Key Field and Lab Test Data SAMPLER TYPE SAMPLE NUMBER & INTERVAL Code Description Code Description a 3.25-inch O.D., 2.42-inch I.D. Split Spoon PP = 1.0 Pocket Penetrometer, tsf b 2.00-inch O.D., 1.50-inch I.D. Split Spoon Sample Identification Number TV = 0.5 Torvane, tsf c Shelby Tube PID = 100 Photoionization Detector VOC screening, ppm d Grab Sample Recovery Depth Interval W = 10 Moisture Content, % e Single -Tube Core Barrel 1 Sample Depth Interval D = 120 Dry Density, pcf f Double -Tube Core Barrel -200 = 60 Material smaller than No. 200 sieve, % g 2.50-inch O.D., 2.00-inch I.D. WSDOT Portion of Sample Retained GS Grain Size - See separate figure for data h 3.00-inch O.D., 2.375-inch I.D. Mod. California for Archive or Analysis AL Atterberg Limits - See separate figure for data i Other - See text if applicable GT Other Geotechnical Testing 1 300-lb Hammer, 30-inch Drop CA Chemical Analysis 2 140-lb Hammer, 30-inch Drop Groundwater 3 4 Pushed Vibrocore (Rotosonic/Geoprobe) Approximate water level at time of drilling (ATD) 5 Other - See text if applicable 1 Approximate water level at time after drilling/excavation/well Civic Center L re LANDAU Playfield Improvements Soil Classification System and Key NiE ASSOCIATES Edmonds, Washington I' 202' CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT z 5 10 15 a of 0 M 0 0 z 20 0 m J_ 0 0 0 N O 0 25 N O O O V 'a 0 Y N W H 130 m B-1 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO LiLO mit �� Limit 20 40 60 80 a� o 5 DrillingMethod: Hollow -Stem Auger W Y A SPT N-Value A a� a T E Ground Elevation ft : 74.8 () C C° 0 Non -Standard N-Value 0 z — m 0 m >. J w 20 40 60 80 CL aa) CL N o a (n Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X m m ° m `� Logged By: SMG Date: 07/19/17 v w cn o6 rn m c9 20 40 60 80 AC Asphalt Pavement (3 inch thickness) SM (ASPHALT) Brown, very silty SAND with gravel (medium dense, moist) S-1 b2 27 (FILL) a c 70 7 o SM Gray, silty SAND with gravel (dense to very w. .:............................. S-2 b2 50 W = 13 dense, moist) o • ; A (GLACIAL TI LL) Z m m S 3 b2 79 A CD 65 :............. W = 8 becomes gravelly ...... S-4 b2 70 GS • X - 60 50/ W = 6 1. S-5 b2 1 55 501 S 6 b2 6" 6.. Boring Completed 07/19/17 Total Depth of Boring = 21.5 ft. 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center Figure LANDAU Playfield Improvements Log of Boring B-1 �C{] 14 ASSOCIATES Edmonds, Washington J�'L ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT z 5 10 15 a Of c7 0 0 J c� 20 z 0 m J_ 0 a 0 N O 0 25 N O O O V 0 0 Y N W H 30 m B-2 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO LiLO mit �� Limit 20 40 60 80 a� o 5 DrillingMethod: Hollow -Stem Auger W Y A SPT N-Value A a� a T E Ground Elevation ft : 81.4 () C C° 0 Non -Standard N-Value 0 z — m 0 m >. J w 20 40 60 80 CL aa) CL N o a (n Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X m m ° m `� Logged By: SMG Date: 07/19/17 v w cn o6 rn m (D n 20 40 60 80 AC Asphalt Pavement (3 inch thickness) \ (ASPHALT) / 80 _MJ SM \\ Brown sandy SILT W _ 10 \------ (FILL)--------/ S-1IF b2 7 Gray, very silty SAND with gravel and wood Q (loose to medium dense, moist) ................................. S-2 b2 12 W = 11 L 75 SM Gray, very silty SAND with gravel (medium S-3 b2 26 dense to very dense, moist to wet) : A (GLACIAL TILL) WGS11 ....: .......:......:.......:...... S-4 b2 47 • X� 70 .............:......:.......:...... S-5 b2 84 W = 10 • :A 65 ............: ..- .�.......:...... nn S-6� b2 50 Boring Completed 07/19/17 Total Depth of Boring = 21.5 ft. 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center Figure LANDAU Playfield Improvements Log of Boring B-2 �C{� 14 ASSOCIATES Edmonds, Washington �7 ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT z 5 10 15 a Of c7 0 0 J c� 20 z 0 co J_ 0 a 0 N O 0 25 N O O O V 0 0 Y N W !J H 30 m B-3 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO LiLO mit �� Limit 20 40 60 80 a� a� o o DrillingMethod: Hollow -Stem Auger W Y A SPT N-Value A a T E Ground Elevation ft : 84.1 () C C° 0 Non -Standard N-Value 0 z — m o m >. J w 20 40 60 80 CL aa) CL N o a (n Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X m m ° m `� Logged By: SMG Date: 07/18/17 v w cn o6 cn m c0 20 40 60 80 SP Gray, fine to medium SAND with trace silt (loose to medium dense, moist to wet) o (TRANSITIONAL BEDS) 4 a W = 17 « S-1 b2 7 - 80 W = 21 color changes to brown .....:............................. S-2 b2 11 - S 3� b2 17 W = 21 color changes to gray GSAi 75 ..............:...... S-4 b2 28 A 70 :...............:.............. S-5 b2 22 W = 20 65 color changes to brown ...._.............._.............. S-6 it b2 7 A Boring Completed 07/18/17 Total Depth of Boring = 21.5 ft. 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center Figure LANDAU Playfield Improvements Log of Boring B-3 �lCyj 14 ASSOCIATES Edmonds, Washington J�'T' ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT z 5 10 15 a of 0 M 0 0 J c� 20 z 0 co 0 0 N O 0 25 N O O O V 0 0 Y N W H 30 m B-4 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO LiLO mit �� Limit 20 40 60 80 a� o 5 DrillingMethod: Hollow -Stem Auger W Y A SPT N-Value A a� a T E Ground Elevation ft : 87.7 () C C° 0 Non -Standard N-Value 0 z — m 0 m >. J w 20 40 60 80 CL aa) CL N o a (n Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X m m ° m `� Logged By: SMG Date: 07/19/17 v w cn o6 rn m c9 20 40 60 80 SP Brown, fine to medium SAND (very loose, moist) (TRANSITIONAL BEDS) s5 = W 9 0 a • S-1 � b2 3 -7 PT Brown PEAT (very loose, wet) — — — — — — — — S-2 b2 2 SO W = 171 17 S-3 b2 0 S-4 b2 0 ^^^ .................................. 75 — -------------------- SP Brown, fine to medium SAND with trace silt (loose, wet) S-5 b2 10 W - 21 �J GS 70 S-6 b2 10 W = 22 Boring Completed 07/19/17 Total Depth of Boring = 21.5 ft. A A lip 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center Rd LANDAU Playfield Improvements Log of Boring B-4 14 ASSOCIATES Edmonds, Washington CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-5 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO Limit Limit 20 40 60 80 a� a� o 5 DrillingMethod: Hollow -Stem Auger LO W Y A SPT N-Value A a T E Ground Elevation ft : 84.2 () C C° 0 Non -Standard N-Value 0 z 0 m >. Cn J w 20 40 60 80 CL aa) o N o L a Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X o w in in m Logged By: SMG Date: 07/18/17 v xs 20 40 60 80 0 SIP Brown, fine to coarse SAND with trace <o gravel (very loose, moist) a (TRANSITIONAL BEDS) 4 o a S-1 -7 b2 4 - 80 5 SM Gray, sir lty SAND (loose, moist to wet) .....:.......:.............. :...... 10 15 a of M 0 0 J z 20 0 co J_ 0 0 0 0 25 N O O O V CL 0 Y N W !J H 30 m S-2 b2 9 A SP Gray,, r e to medium SAND (medium S 3 b2 15 dense, wet) A: 75 S-4 J] b2 23 W = 25 r 70 S-5 b2 25 SP- Gray, gravelly SAND with silt (very dense, 65 SM wet) S-6 b2 50/ W = 14 2" GS Boring Completed 07/18/17 Total Depth of Boring = 21.5 ft. 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center 14 LANDAU Playfield Improvements Log of Boring B-5 ASSOCIATES Edmonds, Washington :A Figure 'Fe® ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT a of M 0 0 J 0 Z 0 m J_ 0 m m B-6 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE J Moisture Content (%) Plastic Liquid Q LO Limit Limit 20 40 60 80 a� o 5 DrillingMethod: Hollow -Stem Auger LO W Y A SPT N-Value A a� a T E Ground Elevation ft : 79.0 () C C° 0 Non -Standard N-Value 0 z 0 m >. Cn J w 20 40 60 80 CL aa) o N o L a Drilled By: Holocene Drilling Inc. W p X Fines Content (%) X o w in in m Logged By: SMG Date: 07/18/17 v xs 20 40 60 80 0 AC Asphalt Pavement (4.5 inch thickness) GP (ASPHALT) 4 a PC PT Brown, sandy GRAVEL Q W - 228 (FILL) _ 22 S-1 b2 3 Portland Cement Concrete (4.5 inch 75 thickness) (PORTLAND CEMENT CONCRETE) 5 S 2 b2 15 W = 23 SM Brown PEAT (soft, wet) /— ........................... - �_ — — (TRANSITIONAL BEDS) ----� Gray, silty SAND (medium dense, wet) S-3 b2 27 W = 24 SP- SM Gray, fine SAND with silt (medium dense to dense, wet) 70 10 WGS 2 ........... .................... S-4� b2 31 X 15 S-5 b2 22 ------------- ML Gray SILT (hard, moist) 60 20 S-6 b2 35 Boring Completed 07/18/17 Total Depth of Boring = 21.5 ft. — 25 — 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center 14 LANDAU Playfield Improvements Log of Boring B-6 ASSOCIATES Edmonds, Washington A pFigure ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-7 LAI Project No: 1548002.010 SAMPLE DATA SOIL PROFILE Moisture Content (%) Plastic Liquid Limit Limit 20 40 60 80 a� (v o 5 Drilling Method: Hollow -Stem Auger A SPT N-Value A E CL 16 E > �0 E Ground Elevation () : 74.3 ft 0 Non -Standard N-Value 0 C Z 0 m cn > � 3 20 40 60 80 X Fines Content (%) X °— °' i� CL a) T a �` n f6 o `—' a cn Holocene Drilling Inc. Drilled By: g a m m ° m `� Logged ed By: SMG Date: 07/19/17 2 o w cn o6 rn m c9 c9 20 40 60 80 0 AC Asphalt Pavement (3 inch thickness) SM (ASPHALT) Brown, very silty, gravelly SAND (medium dense to dense, moist) S-1 b2 22 (TRANSITIONAL BEDS) it 70 o 5 W = 10 color changes to gray w S-2 b2 25 GS o • ; uC z m S-317 2 b2 43 65 CD 10 S-411, b2 21 Boring Completed 07/19/17 Total Depth of Boring = 11.5 ft. 15 x a 0 0 0 J c� 20 Z O m J_ O 0 0 0 0 25 N O O O V 0 0 Y N W !J H 30 m 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessaryfor a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center 14 LANDAU Playfield Improvements Log of Boring B-7 ASSOCIATES Edmonds, Washington Figure ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Z 0 LU w 0 0 a w m SAMPLE DATA (D E a ~ _ Z Co 0 � as o c a a) E c 0. E n o o6 a>i w in in � 0 78 2 S-1 1[ d W= 277 S-2 d W = 27 76 GS 4 S-3= d WGS 3 74 6 �-8 �_10 �-12 o. aD 0 2 4 6 8 10 12 Test Pit Completed 07/21/17 Total Depth of Test Pit = 7.0 ft. SAMPLE DATA a� aD E CL Z as (D (D 0 > E c E u aD w in o6 in F_ 80 S-1 = d GS 5 S-2 d W = 8 S-3 d GS 78 76 74 S-4 —M [ d I W = 19 Test Pit Comple e Total Depth of Test Pit = 10.0 ft. TP-1 SOIL PROFILE 0 o Excavation Method: Tracked Excavator cn >, Ground Elevation (ft): 79.5 `—' a Cn cn Northwest Excavating and Truckin I Excavated By: g g� Logged By: SMG SM Brown, very silty SAND with gravel (very loose, moist) PT (TOPSOIL) Brown PEAT (very loose, wet) _ SM — — — — (TRANSITIONAL BEDS) — ----J Gray, silty SAND with trace gravel (medium _ SP- dense, wet) SM------------------J Gray, iron -stained, fine to medium SAND with silt (medium dense, wet) color changes to brown ilrb� SOIL PROFILE 0 o Excavation Method: Tracked Excavator cn >, Ground Elevation (ft): 83.5 `—' a cn Northwest Excavating and Truckin I Excavated By: g g� Logged By: SMG SM Brown, silty SAND with organics (very loose, moist) gp_ SM (TOPSOIL) Brown, fine to medium SAND with silt and trace gravel and cobbles (loose, moist) GP — — — (TRANSITIONAL BEDS) — — , — o S Brown, very sandy GRAVEL with trace silt � (loose, wet) SM ------------------J Gray, fine to medium SAND with silt (medium dense, wet) GROUNDWATER Moderate Seepage groundwater seepage encountered at 5.0 ft. GROUNDWATER Slow Seepage groundwater seepage encountered at 8.0 ft. Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center Figure LANDAU Playfield Improvements Log of Test Pits plQ 14 ASSOCIATES Edmonds, Washington 1T.7 ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT TP-1-18 SAMPLE DATA SOIL PROFILE GROUNDWATER (D o Excavation Method: Rubber -tired Backhoe ' Z a m E '' (n 75 E T Ground Elevation (ft): 84.8 0 N m a (D 0. N U a (n (D °�' m m U Logged By: SMG 0 W (n o6 (n H U n 0 SM Dark brown, very silty SAND with organics 84 (loose, moist) gp (TOPSOIL) 2 Light brown, fine to medium SAND, trace silt 82 (medium dense, moist to wet) 4 (TRANSITIONAL BEDS) Slow Seepage groundwater seepage encountered at 4.0 ft. 80 6 78 8 176 110 Test Pit Completed 03/05/19 Total Depth of Test Pit = 9.0 ft. �-12 TP-2-18 SAMPLE DATA SOIL PROFILE GROUNDWATER au o Rubber -tired Backhoe .0 (D E 75 Excavation Method: 0 ' '' E Ground Elevation (ft): 83.0 Z m T o (D m (n °>' a�i (5 Logged By: SMG 0 W (n o6 (n H (D 0 UL SM Dark brown, very silty SAND with organics 82 P J 1 (loose, moist) / SP 1 (TOPSOIL) / 2 — PT 11 Brown PEAT (very loose, moist) 80 111 (TRANSITIONAL BEDS) 4 1 Gray, fine to medium SAND, trace silt / / Slow Seepage groundwater _ SP \ (medium dense, moist) 1/ seepage encountered at 4.0 ft. 78 \ 1------------------1/ \ Brown PEAT (very loose, moist) / 6 ------------------ Gray, fine to medium SAND, trace silt 76 (medium dense, wet) 8 Test Pit Completed 03/05/19 Total Depth of Test Pit = 8.0 ft. 10 — 12 — Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center F25 LANDAU Playfield Improvements Log of Test Pits 14 ASSOCIATES Edmonds, Washington CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT o. a� 0 2 4 6 8 10 12 0 aD 0 2 4 6 8 10 12 TP-3-18 SAMPLE DATA SOIL PROFILE au .0 (D o Excavation Method: Rubber -tired Backhoe ' � Z � a � E ' � 75 E T Ground Elevation (ft): 81.3 O N Z6 'a❑ 65 U Q (n (n (Dm m m (5 Logged By: SMG W (n o6 (n H U` n SM Dark brown, very silty SAND with organics 11 (loose, moist) 80 (TOPSOIL) SPJ \ Gray, fine to medium SAND, trace silt (loose, ' PT \ moist) 78 \_ — — — (TRANSITIONAL BEDS)— ----) SP NN Brown PEAT (very loose, moist) 76 11------------------ Gray, fine to medium SAND, trace silt (medium dense, moist to wet) Test Pit Completed 03/05/19 Total Depth of Test Pit = 6.5 ft. TP-4-18 SAMPLE DATA SOIL PROFILE au .0 (D o Excavation Method: Rubber -tired Backhoe ' Z 0 c6 E ' (n 75 E >, Ground Elevation (ft): 78.5 . O (Dc6 ❑ U a (n (n °>' m `� � Logged By: SMG W (n o6 (n H (D 78 SM Dark brown, very silty SAND with organics (loose, moist) PT (TOPSOIL) Brown PEAT with gravel (very loose, moist) � 76 SP (TRANSITIONAL BEDS) �— — — — — ----J Gray, fine to medium SAND, trace gravel 74 (medium dense, moist to wet) 72 Test Pit Completed 03/05/19 Total Depth of Test Pit = 7.0 ft. GROUNDWATER Groundwater not encountered. GROUNDWATER S7 Slow Seepage groundwater seepage encountered at 4.5 ft. Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center jar gure LANDAU Playfield Improvements Log of Test Pits 14 ASSOCIATES Edmonds, Washington 5 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT z 0 w J W 0 J F- a F- w F- L Q a� 0 2 4 6 8 10 12 SAMPLE DATA .0 aD E a Z co co (D > E c E u aD w x) in i n F__ 78 76 74 Test Pit Completed 03/05/19 Total Depth of Test Pit = 6.0 ft. TP-5-18 SOIL PROFILE o Excavation Method: Rubber -tired Backhoe cn >, Ground Elevation (ft): 78.6 U V) Q � Logged By: SMG SM Dark brown, very silty SAND with organics (loose, moist) PT (TOPSOIL) Brown PEAT (very loose, moist) SP �(TRANSITIONAL BEDS) �— — — — — ----J Gray, fine to medium SAND, trace silt (medium dense, moist to wet) GROUNDWATER S7 Slow Seepage groundwater seepage encountered at 4.0 ft. Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Civic Center jar gure LANDAU Playfield Improvements Log of Test Pits 14 ASSOCIATES Edmonds, Washington 5 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX B Laboratory Soil Testing RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX B LABORATORY SOIL TESTING Soil samples obtained from the exploratory borings and test pits were taken to our laboratory for further examination and testing. Laboratory tests were performed on representative soil samples to characterize certain engineering and index properties of the soils at the project site. The laboratory testing program, which was performed in general accordance with the ASTM International (ASTM) standard test procedures noted below, was limited to visual inspection to confirm our field soil descriptions, and determination of natural moisture content and grain size distribution. A brief description of the testing performed is presented below. Natural Moisture Content The natural moisture contents of selected soil samples obtained from the exploratory borings and test pits were determined in general accordance with ASTM D 2216 test procedures. The results from the moisture content determinations are indicated adjacent to the corresponding samples on the summary logs presented in Appendix A. Grain Size Analysis Sieve and combined sieve and hydrometer analyses were conducted on selected soil samples obtained from the exploratory borings and test pits in general accordance with ASTM D 422 test procedures. Samples selected for grain size analysis are designated with a "GS" in the column labeled "Test Data" on the summary boring and test pit logs. The test results are presented in the form of grain size distribution curves on Figure B-1 through B-3. The U.S. Department of Agriculture (USDA) textural classifications based on the results of the combined sieve and hydrometer analyses are presented on Figure B-4. B-1 BESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 1548002.01 10/13/17 N:\PROJECTS\1548002.010.012.GPJ GRAIN SIZE FIGURE STRAIGHT LINE 100 U.S. Sieve Opening in Inches 6 4 3 2 1.5 1 1/2 3/8 3 4 U.S. Sieve Numbers Hydrometer 6 8 10 14 16 20 30 40 5060 100 140 200 90 80 70 t 60 LL 50 a� a 40 30 20 10 0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters Sample LANDAU ASSOCIATES Civic Center Playfield Improvements Edmonds, Washington Grain Size Distribution Figure -B Cobbles Gravel Sand Silt or Clay Coarse Fine Coarse Medium Fine Symbol Exploration Number Depth Natural Moisture(%) Soil Description 1548002.01 10/13/17 N:\PROJECTS\1548002.010.011.GPJ GRAIN SIZE FIGURE STRAIGHT LINE 100 U.S. Sieve Opening in Inches 6 4 3 2 1.5 1 3 4 1 /2 3/8 3 L U.S. Sieve Numbers Hydrometer 6 810 14 16 20 30 40 5060 100 140 200 90 80 70 t 60 50 a� a 40 30 20 10 0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters Sample LANDAU ASSOCIATES Civic Center Playfield Improvements Edmonds, Washington Grain Size Distribution Figure -2 B Cobbles Gravel Sand Silt or Clay Coarse Fine Coarse Medium Fine Symbol Exploration Number Depth Natural Moisture(%) Soil Description 1548002.01 10/13/17 N:\PROJECTS\1548002.010.011.GPJ GRAIN SIZE FIGURE STRAIGHT LINE 100 U.S. Sieve Opening in Inches 6 4 3 1.5 1 3 4 1 /2 3/8 3 4 U.S. Sieve Numbers Hydrometer 6 8 10 14 16 20 30 40 5060 100 140 200 90 80 70 60 LL 50 2 aD a 40 30 20 10 0 100 10 1 0.1 0.01 0.001 Grain Size in Millimeters Sample LANDAU ASSOCIATES Civic Center Playfield Improvements Edmonds, Washington Grain Size Distribution Figure -3 B Cobbles Gravel Sand Silt or Clay Coarse Fine Coarse Medium Fine Symbol Exploration Number Depth Natural Moisture(%) Soil Description 0 100^ Ell PERCENT SAND Exploration Number Sample Number Depth (ft) Natural Moisture (%) USDA Textural Classification USCS Classification • TP-1 S-3 4.5 23 SAND SP-SM m TP-2 S-1 3.0 5 SAND SP-SM Civic Center LANDAU Playfield Improvements ASSOCIATES Edmonds, Washington Figure USDA Textural Classification Chart Dcvr ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT APPENDIX C Summary Logs of Previous Explorations RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT %,r , �g 5� - g-� R g-6jce — ; t _ i , •I _. NORTH - 100 feet Z2� i� B- # = Boring Exploration Location Date: 9-7-14 By: JB Scale: As Shown Project GEOTEST SERVICES, INC. SITE AND EXPLORATION PLAN 14-0471 741 Marine Drive Bellingham, WA 98225 ANNUAL SEWER REPLACEMENT PROJECT - SITE 4 Figure phone: (360) 733-7318 DALEY STREET AND 7TH AVENUE N fax: (360) 733-7418 EDMONDS, WASHINGTON RE UI Mar 25 20, MAJOR DIVISIONS Soil Classification System Uscs GRAPHIC LETTER SYMBOL SYMBOL TYPICAL DESCRIPTIONS(')(�) GRAVEL AND CLEAN GRAVEL ° o o °o; o GW Well -graded gravel; graveVsand mixture(s); little or no fines 016 o �? o GP �_ w GRAVELLY SOIL (Little or no fines) Poorly graded gravel; graveVsand mixture(s); little or no fines O ~ 0 ° . GRAVEL WITH FINES GM .� m (More than 50% of coarse fraction retained Silty gravel; graveVsand/silt mixture(s) ZE c o on No. 4 sieve) (Appreciable amount of fines) Clayey GC Q N gravel; gravel/sand/clay mixture(s) 0 0 (D O � SAND AND CLEAN SAND SW Well -graded sand; gravelly sand; little or no fines U) : t QSP SANDY SOIL (Little or no fines) Poorly graded sand; gravelly sand; little or no fines SAND WITH FINES SM O 2 U V @ (More than 50% of coarse fraction passed Silty sand; sand/silt mixture(s) $C through No. 4 sieve) (Appreciable amount of fines) Clayey sand; sand/clay mixture(s) ML Inorganic silt and very fine sand; rock flour; silty or clayey fine f6 �', SILT AND CLAY sand or clayey silt with slight plasticity CL O' .N Inorganic clay of low to medium plasticity; gravelly clay; sandy E N (Liquid limit less than 50) clay; silty clay; lean clay QL W 66 z o z Organic silt; organic, silty clay of low plasticity Q N M N MH Inorganic silt; micaceous or diatomaceous fine sand t:F; SILT AND CLAY CH z E Inorganic clay of high plasticity; fat clay o (Liquid limit greater than 50) OH Organic clay of medium to high plasticity; organic silt HIGHLY ORGANIC SOIL PT Peat; humus; swamp soil with high organic content GRAPHIC LETTER OTHER MATERIALS SYMBOL SYMBOL TYPICAL DESCRIPTIONS PAVEMENT AC Or PC Asphalt concrete pavement or Portland cement pavement ROCK RK Rock (See Rock Classification) WOOD WD Wood, lumber, wood chips DEBRIS O O O DB Construction debris, garbage Notes: 1. Soil descriptions are based on the general approach presented in the Standard Practice for Description and Identification of Soils (Visual -Manual Procedure), as outlined in ASTM D 2488. Where laboratory index testing has been conducted, soil classifications are based on the Standard Test Method for Classification of Soils for Engineering Purposes, as outlined in ASTM D 2487. 2. Soil description terminology is based on visual estimates (in the absence of laboratory test data) of the percentages of each soil type and is defined as follows: Primary Constituent: > 50% - "GRAVEL," "SAND," "SILT," "CLAY," etc. Secondary Constituents: > 30% and < 50% - "very gravelly," "very sandy," "very silty," etc. > 12% and < 30% - "gravelly," "sandy," "silty," etc. Additional Constituents: > 5% and < 12% -"slightly gravelly," "slightly sandy," "slightly silty," etc. < 5% - "trace gravel," "trace sand," "trace silt," etc., or not noted. Drilling and Sampling Key Field and Lab Test Data SAMPLE NUMBER & INTERVAL SAMPLER TYPE Code Description Code Description Sample Identification Number a 3.25-inch O.D., 2.42-inch I.D. Split Spoon PP = 1.0 Pocket Penetrometer, tsf b 2.00-inch O.D., 1.50-inch I.D. Split Spoon TV = 0.5 Torvane, tsf Recovery Depth Interval c Shelby Tube PID = 100 Photoionization Detector VOC screening, ppm 1�14-- Sample Depth Interval d Grab Sample W = 10 Moisture Content, % J e Other - See text if applicable D = 120 Dry Density, pcf Portion of Sample Retained 1 300-lb Hammer, 30-inch Drop -200 = 60 Material smaller than No. 200 sieve, % for Archive or Analysis 2 140-lb Hammer, 30-inch Drop GS Grain Size - See separate figure for data 3 Pushed AL Atterberg Limits - See separate figure for data 4 Other - See text if applicable GT CA Other Geotechnical Testing Chemical Analysis Groundwater L7 Approximate water elevation at time of drilling (ATD) or on date noted. Groundwater ATD levels can fluctuate due to precipitation, seasonal conditions, and other factors. OeoTe5T CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-1 SAMPLE DATA SOIL PROFILE -0 a) -0 a Drilling Method: Hollow -stem Auger c j z m T ~ oo a T E T Ground Elevation (ft). 88 U a o N E c E LL o (6 ) U � U Drilled By: Environmental Drilling, Inc. J 0 w in 06 cn m H c7 Z co � 0 AC Asphalt Pavement (± 4 inches) SM Loose to medium dense, tan to tan grey, dry SM to damp, trace to slightly silty, trace to slightly gravelly, fine to medium SAND 85 1 ][ b2 6 W = 10 5 2 b2 12 W - 7 GS 80 3 b2 10 W = 21 10 4 b2 12 W = 25 75 5 b2 19 W = 19 15 6 b2 37 W - 19 GS 70 7 b2 54 W = 26 20 811 b2 52 W = 26 65 - 25 9, I b2 I 48 I W=13 Boring Completed 09/05/14 Total Depth of Boring = 26.5 ft. - 30 (Advance Outwash) Distinct red to orange mottled soils from 6 to 10 feet BGS Becoming medium dense to very dense and saturated below 12.5 feet BGS SM/ Dense to very dense, grey, wet to saturated, Sc gravelly, very silty/clayey, SAND (Probable Transitional Beds) a ATD 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key' figure for explanation of graphics and symbols. Annual Sewer Replecement OG'OTG'ST Project - Site 4 Log of B-1 Daley Street and 7th Avenue N Edmonds, Washington GROUNDWATER Figure ;EV ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-2 SAMPLE DATA SOIL PROFILE GROUNDWATER -0 a) -0 a Drilling Method: Hollow -stem Auger c j z m T ~ °o a T E T Ground Elevation (ft)- 91.5 U U N L.L (6 U C/) J a E c E o ) U Drilled By: Environmental Drilling, Inc. 0 w in 06 (n m H c7 Z co � 0 AC Asphalt Pavement (± 4 inches) SP- Loose to medium dense, tan to tan grey, dry 90 SM to damp, trace to slightly silty, trace to slightly gravelly, fine to medium SAND (Advance Outwash) 10 b2 14 W = 4 5 11 b2 7 W=6 85 W - 5 12 b2 12 GS 10 13 b2 13 W = 6 80 14 b2 13 W=19 15 ATD W = 25 Distinct red to orange mottled soils at 15 15 b2 14 GS feet BGS 75 Becoming medium dense to very dense with 16 b2 33 W = 26 trace silty, SAND lenses below 17.5 feet BGS 20 17 b2 28 W = 25 70 18 b2 78/10" W = 24 25 191 b2 1 45 1 W = 24 Boring Completed 09/05/14 Total Depth of Boring = 26.5 ft. 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key' figure for explanation of graphics and symbols. Annual Sewer Replecement C�G'OTG'ST Project - Site 4 Log of B-2 Daley Street and 7th Avenue N E Edmonds, Washington CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-3 SAMPLE DATA SOIL PROFILE GROUNDWATER -0 a) -0 a Drilling Method: Hollow -stem Auger c j z m T ~ °o a T E T Ground Elevation (ft). 88.5 U a U N E c E LL o (6 ) U � U Drilled By: Environmental Drilling, Inc. J o w in 06 (n m 1 c� Z co 0 AC Asphalt Pavement (± 4.5 inches) SP- Loose to medium dense, orange tan, trace SM to slightly silty, fine to medium SAND SP- (Weathered Advance Outwash) SM Loose to medium dense, tan to tan grey, dry 85 20 b2 10 to damp, trace to slightly silty, trace to slightly gravelly, fine to coarse SAND (Advance Outwash) 5 21 b2 12 80 22� b2 17 GS4 10 23 b2 12 W = 21 SZ ATD SP- Medium dense to very dense, blue grey, SM slightly silty, fine to coarse SAND (Advance 75 24 b2 16 W = 23 Outwash) with scattered tan, slightly gravelly, SAND layers 15 25 b2 29 70 26 b2 36 20 65 27 b2 65/11" 25 Boring Completed 09/05/14 Total Depth of Boring = 24.0 ft. 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols. Annual Sewer Replecement Figure C�G'OTG'ST Project - Site 4 Log of B-3 Daley Street and 7th Avenue N EAU Edmonds, Washington ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-4 SAMPLE DATA SOIL PROFILE GROUNDWATER -0 a) -0 a Drilling Method: Hollow -stem Auger w o j Z m T ~ T E Ground Elevation (ft). 82 J a E c E io o ) U Drilled By: Environmental Drilling, Inc. o w in 06 (n m 1 c� Z co 0 AC Asphalt Pavement (± 4 inches) SP- --------------------------------------- Loose to medium dense, tan to tan grey, SM damp, trace to slightly silty, trace to slightly 80 gravelly, fine to coarse SAND (Advance Outwash) 28 b2 20 Rock partially obstructing sampler tip, blow counts may be slightly elevated 5 Rock partially obstructing sampler tip, blow 29 b2 24 counts may be slightly elevated 75 30 b2 17 W = 4 10 Distinct red to orange mottled soils from 10 31 b2 14 W = 20 to 14 feet BGS 70 ATD Becoming saturated below 12.5 feet BGS 32 b2 14 W = 26 15 65 33 b2 25 SM/ Medium dense/very stiff, grey, wet to ML saturated, gravelly, very silty, SAND to very 20 sandy, SILT (Transitional Beds) 60 34 b2 25 25 Boring Completed 09/05/14 Total Depth of Boring = 24.0 ft. 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key' figure for explanation of graphics and symbols. Annual Sewer Replecement Figure OG'OTG'ST Project - Site 4 Log of B-4 Daley Street and 7th Avenue N EFU Edmonds, Washington ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-5 SAMPLE DATA SOIL PROFILE GROUNDWATER -0 a) -U a Drilling Method: Hollow -stem Auger c j z m T ~ °o a T E T Ground Elevation (ft). 75 U a U N� E c 2 E L.L o (6 ) U U Drilled By: Environmental Drilling, Inc. J 0 w in 06 cn m H c7 Z co � 0 75 AC Asphalt Pavement (± 3.5 inches) SM/ Loose, blue grey, moist, silty/clayey, SAND SC (Probable Fill) with scattered wood debris 35 b2 6 SZ ATD ML/ Stiff to very stiff, blue grey, wet to saturated, 5 70 W = 27 CL very sandy, SILT/CLAY (Transitional Beds) 36 b2 10 GS SZ ATD Slightly mottled tan, saturated, SAND lens at 37 b2 27 7.5 to 8 feet BGS 10 65 SM Loose to very dense, grey, saturated, silty to 38 b2 26 very silty, gravelly, fine to coarse SAND (Transitional Beds) W - 13 39 b2 10 GS 15 60 40 b2 53 20 Boring Completed 09/05/14 Total Depth of Boring = 19.0 ft. 25 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key' figure for explanation of graphics and symbols. Annual Sewer Replecement Figure OG'OTG'ST Project - Site 4 Log of B-5 Daley Street and 7th Avenue N E$U Edmonds, Washington ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT B-6 SAMPLE DATA SOIL PROFILE GROUNDWATER -0 a) -U a Drilling Method: Hollow -stem Auger c jT° z o TE Ground Elevation (f). 86 Uv a U E c E o ) �N U Drilled BBoretec Inc. J o w in 06 (n m � 2 c� Eny: co 0 AC Asphalt Pavement (± 5 inches) SP- Medium dense, tan, damp, slightly silty, 85 SM slightly gravelly, SAND (Probable Import Fill) 41 b2 3 W = 79 PT Very soft, dark brown, moist to wet, silty, sandy, ORGANICS (Peat) 5 80 42 b2 1 W = 366 431[ b2 1 W = 229 Q ATD SM Loose, dark brown, saturated, organic, silty, 44 b2 W = 72 SAND (Transitional Peat Deposit) SM Medium dense, grey, saturated, slightly silty 10 45� b2 19 WGS 2 to silty, gravelly, fine to coarse SAND 75 (Advance Outwash) 46 b2 19 15 Becoming tan below 15 feet BGS 70 47 b2 22 W = 23 48 b2 46 20 65 49 b2 30 50 b2 26 25 Boring Completed 09/11/14 Total Depth of Boring = 24.0 ft. 30 35 Notes: 1. Stratigraphic contacts are based on field interpretations and are approximate. 2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions. 3. Refer to "Soil Classification System and Key' figure for explanation of graphics and symbols. Annual Sewer Replecement Figure OG'OTG'ST Project - Site 4 Log of B-6 Daley Street and 7th Avenue N EqU Edmonds, Washington ar 25 202 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT LANDAU AssociATl s September 4, 2020 Walker Macy 111 SW Oak St, Suite 200 Portland, OR 97204 Attn: Ms. Andrea Kuns, ASLA, Senior Associate Transmitted via email to: akuns@WalkerMacy.com Re: Summary of Wet Season Groundwater Monitoring Civic Center Playfield Improvements Edmonds, Washington LAI Project No. 1548002.010.011 Dear Ms. Kuns: This memorandum summarizes the results of groundwater monitoring completed by Landau Associates, Inc. (LAI) in support of the Civic Center Playfield Improvements project, located at 598 Edmonds Street in Edmonds, Washington (site; Figure 1). Project Understanding LAI's project understanding is based on information provided by the City of Edmonds (City; project owner) and Walker Macy (project architect). The City plans to improve the existing Civic Center Playfield by adding a restroom and concession building, a shade pavilion, athletic courts and field, a water feature, a playground, a skate park, a scramble wall, view terraces, walkways, and stormwater infiltration facilities. To facilitate design of the proposed stormwater management systems, LAI monitored groundwater elevations at the site during the 2018-2020 wet seasons. Services were provided in accordance with the scope outlined in the Standard Form of Agreement between Architect (Walker Macy) and Consultant (LAI), dated April 24, 2017. Groundwater Observations During an earlier phase of the project, LAI installed monitoring wells in borings B-5 and B-6. The approximate locations of the borings are shown on Figure 2. LAI installed Solinst° leveloggers in both monitoring wells to measure and log semi -continuous groundwater levels at the site. Additionally, a Solinst barologger was installed in a dry, sheltered area of the site to measure and log changes in atmospheric pressure. Barologger data were used to compensate the water and ESUB 130 2nd Avenue South • Edmonds, Washington 98020 • (425) 778-0907 • www.landauinc.com Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Civic Center Playfield Improvements Landau Associates atmospheric pressure measurements recorded by the leveloggers. The compensated water pressure measurements were then converted to water level -equivalent measurements. Site groundwater levels were initially logged between October 24, 2018 and March 19, 2019. Subsequently, groundwater levels were logged between September 30, 2019 and May 4, 2020. An equipment malfunction during the 2018-2019 wet season resulted in an incomplete set of groundwater data. LAI replaced the leveloggers and barologger before the 2019-2020 wet season. During the 2019-2020 wet season, the leveloggers measured and logged groundwater levels at 2- hour intervals. Between late September 2019 and early May 2020, LAI personnel manually measured groundwater levels on or around the first of each month. LAI's manual water -level measurements for the 2019-2020 wet season are presented in the following table. The compensated water levels are presented on Figure 3 along with precipitation data from the National Oceanic and Atmospheric Administration Weather Forecast Office Seattle Station. Depth to Groundwater (ft bgs) Location of Manual 9/30/2019 11/1/2019 12/2/2019 1/2/2020 2/3/2020 3/3/2020 3/31/2020 5/4/2020 Reading B-5 4.2 4 3.8 3 3 2.9 3.1 3.36 B-6 2.8 3.75 2.8 2.5 2.75 3 3 3.09 bgs = below ground surface ft = feet Use of This Memorandum Landau Associates has prepared this wet season groundwater monitoring memorandum for the exclusive use of Walker Macy and the City of Edmonds for specific application to the Civic Center Playfield Improvements project in Edmonds, Washington. No other party is entitled to rely on the information, conclusions, and recommendations included in this document without the express written consent of Landau Associates. Reuse of the information, conclusions, and recommendations provided herein for extensions of the project or for any other project, without review and authorization by Landau Associates, shall be at the user's sole risk. Landau Associates warrants that, within the limitations of scope, schedule, and budget, its services have been provided in a manner consistent with that level of care and skil I ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions as this project. Landau Associates makes no other warranty, either express or implied. September 4, 2020 BESUB Isar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Civic Center Playfield Improvements Landau Associates Closing If you have questions, or if additional information is required, please contact the undersigned at (425) 329-0251. LANDAU ASSOCIATES, INC. Sean M. Gertz, PE Senior Project Engineer SY"- LL�4 Steven R. Wright, PE Principal BCS/SMG/SZW/mcs [P:\1548\002\R\GROUNDWATER MONITORING MEMO\EDMONDS CIVIC CENTER GROUNDWATER MONITORING MEMORANDUM 9.4.2020.DOCX] Attachments: Figure 1. Vicinity Map Figure 2. Site and Exploration Plan Figure 3. Groundwater Level Readings: September 2019—May 2020 September 4, 2020 -RESUB Isar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Puget Sound 4- Project Location II II II eta �rF r. II > rr City.. Aim F- \ �I u6.i , �r = ���■ �� sperance Deep Creek N 0 0.5 1 Miles Data Source: Esri 2012 Civic Center LANDAU Playfield Improvements ASSOCIATES Edmonds, Washington to Seattle Spokane Tacoma Ilympia Washington Vicinity Map Figure REIS U Mar 25 20 1 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 0 a \\ � I I I , I I � I 4 — — — _ Daley — — — — i I I I � I �- Q I o I Legend B1 Boring Location and Designation TP-1 I9 Test Pit Location and Designation 0 a LANDAU ASSOCIATES map source: KPFF Land Surve) Civic Center Playfield Improvements Edmonds, Washington 0 150 300 Scale in Feet rs September 2017 Figure Site & Exploration Plan RaU CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT 9/4/20 \\edmdata01\projects\1548\002\R\Groundwater Monitoring Memo\F03 2019 - 2020 GW data.docx F� F" F" F� F- F- F� F� F- l0 F-+ O O O F- F- F_� F_� F- F- IV IV IV F� F� F� rV rV rV W W W A A A \ O \ \ \ F" \ \ \ rV rV \ \ \ F� \ \ \ ti \ \ \ W W \ \ \ A \ \ \ W W \ F� rj Nj \ F� PQ \ \ N) W \ F� �j 11j \ FA FA 11j \ \ FA ti W \ F-` ti ti \ O V A F� 00 A F� 00 L 1 ry l0 Ol W O Ol W O V W O V A N) l0 O W O O W O V A \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O lD l0 l0 l0 l0 lD l0 lD lD lD lD l0 l0 l0 O O O O O O O O O O O O O O O O O O 0.0 6 5.5 2.0 5 4.5 4.0 4 3.5 i C: 6.0 3 D N O 2.5 i p 8.0 2 1.5 Q Q 10.0 1 0.5 12.0 0 13-5 Water Level B-6 Water Level Rainfall Notes 1) Water level data were collected from monitoring wells installed in borings B-5 and B-6 and have been converted to depth -to - water, relative to ground surface. 2) Precipitation data are from the National Oceanic and Atmospheric Administration Weather Forecast Office Seattle Station. Civic Center Playfield Improvements Groundwater Level Readings: Figure LANDAU Edmonds, Washington September 2019—May 2020 3 ASSOCIATES r � Appendix F Water Quality Vault Detail Civic Center Playfield — WalkV&bU 2021 Ape n dI°ANT SERDV CES DEPARTMENT RESUB Mar 25 2021 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT PLAN VIEW FLOW KIT NOT SHOWN CONTRACTOR TO GROUT TO FINISHED GRADE co CONTECH TO PROVIDE GRADE RING/RISERS uL---------_L� -------------------- L� A � N 1 OVERFLOW ASSEMBLY - LOW DROP k STEP STORMFILTER CARTRIDGE INLET PIPE 1 p (016 RNA - m, INLET INLET 2 PIPE FLOW KIT DISSIPATOR 08" PVC INLET 3 PIPE (012" OPG.) 012" PVC (016" OPG.) ELEVATION VIEW 1/2" 2" PVC SLIP PLUG STORMFILTER CARTRIDGE 90, 1 90` SECTION A -A MATERIAL LIST - PROVIDED BY CONTECH INLET DISSIPATOR COUNT DESCRIPTION INSTALLED BY 32 LOW DROP, PHOSPHOSORB CARTRIDGE CONTECH 46 8.35 GPM, RESTRICTOR DISK (YLW) CONTECH 14 2" PVC SLIP PLUG CONTECH 1 FLOW KIT 13A CONTECH 3 INLET DISSIPATOR ASSEMBLY CONTECH 1 OVERFLOW ASSEMBLY - LOW DROP CONTECH 1 JOINT SEALANT CONTRACTOR 2 PLACES GRADE RINGS/RISERS CONTRACTOR 1 30" X 4" EJ 41600484 FRAME AND COVER CONTRACTOR 1 36" x 48" HATCH, DHT3648AL CONTRACTOR 5 STEPS, P10CTS, BY LANE LADDER, OR EQUIV. CONTECH INLET DISSIPATOR OUTLET SUMP OVERFLOW ASSEMBLY - LOW DROP SITE DESIGN DATA WATER QUALITY FLOW RATE 0.505 CFS PEAK FLOW 1.43 CFS RATE RETURN PERIOD 100 YRS OF PEAK FLOW FILTER MEDIA TYPE PHOSPHOSORB PERFORMANCE SPECIFICATION FILTER CARTRIDGES SHALL BE MEDIA -FILLED, PASSIVE, SIPHON ACTUATED, RADIAL FLOW, AND SELF CLEANING. RADIAL RIM ELEV. = 79.92+/- MEDIA DEPTH SHALL BE 7-INCHES. FILTER MEDIA CONTACT TIME SHALL BE AT LEAST 38 SECONDS. 7 \7 SPECIFIC FLOW RATE SHALL BE 1.67 GPM/SF (MAXIMUM). SPECIFIC FLOW RATE IS THE MEASURE OF THE FLOW (GPM) DIVIDED BY THE MEDIA SURFACE CONTACT AREA (SF). MEDIA VOLUMETRIC FLOW RATE SHALL BE 6 GPM/CF OF MEDIA (MAXIMUM). OUTSIDE TOP ELEV. 78.62 GENERAL NOTES 1. CONTECH TO PROVIDE ALL MATERIALS UNLESS NOTED OTHERWISE. A 2. FOR FABRICATION DRAWINGS WITH DETAILED STRUCTURE DIMENSIONS AND WEIGHT, PLEASE CONTACT YOUR CONTECH REPRESENTATIVE. www.ContechES.com c 3. STORMFILTER WATER QUALITY STRUCTURE SHALL BE IN ACCORDANCE WITH ALL DESIGN DATA AND INLET 2 INFORMATION CONTAINED IN THIS DRAWING. CONTRACTOR TO CONFIRM STRUCTURE MEETS REQUIREMENTS OF INV. ELEV. = 74.41 PROJECT. INLET 3 4. STRUCTURE SHALL MEET AASHTO HS-20, ASSUMING EARTH COVER OF 0' - 5', AND GROUNDWATER ELEVATION AT, INV FLFV = 74 06 OR BELOW, THE OUTLET PIPE INVERT ELEVATION. ENGINEER OF RECORD TO CONFIRM ACTUAL GROUNDWATER ZINLET 1 ELEVATION. CASTINGS SHALL MEET AASHTO M306 LOAD RATING AND BE CAST WITH THE CONTECH LOGO. . ELEV. = 73.99 5. STORMFILTER STRUCTURE SHALL BE PRECAST CONCRETE CONFORMING TO ASTM C-857 AND AASHTO OUTLET LOAD FACTOR DESIGN METHOD. INV. ELEV. = 72.02 INSTALLATION NOTES OUTSIDE BOTTOM A. ANY SUB -BASE, BACKFILL DEPTH, AND/OR ANTI -FLOTATION PROVISIONS ARE SITE -SPECIFIC DESIGN ELEV. = 71.52 CONSIDERATIONS AND SHALL BE SPECIFIED BY ENGINEER OF RECORD. B. CONTRACTOR TO PROVIDE EQUIPMENT WITH SUFFICIENT LIFTING AND REACH CAPACITY TO LIFT AND OUTLET PIPE SET THE STORMFILTER STRUCTURE (LIFTING CLUTCHES PROVIDED). 012" PVC C. CONTRACTOR TO INSTALL JOINT SEALANT BETWEEN ALL STRUCTURE SECTIONS AND ASSEMBLE STRUCTURE. (016" OPG.) D. CONTRACTOR TO PROVIDE, INSTALL, AND GROUT INLET PIPES. MATCH OUTLET PIPE INVERT WITH OUTLET BAY FLOOR. E. CONTRACTOR TO TAKE APPROPRIATE MEASURES TO PROTECT CARTRIDGES FROM CONSTRUCTION -RELATED EROSION RUNOFF. RESU B CONTECH STRUCTURE WEIGHT Mar 25 2021 APPROXIMATE HEAVIEST PICK = 36500 LBS CONTRACT OF 3 PIECES CITYOF EDMONDS DEVELOPMENT SERVICES MAX FOOTPRINT = 9' x 19' DRAWING 8 & wv °m�Ec� m ' was E�m&D a° vEn9 vo�n�."c _ E" uo 8 sH-o g o o22 mn _moo�o „a °E3 E ovo a'2E'o 'Le _ °o o= °s=ave„W ��3�aa� E!t Hom o-11— 0 .e m"HHE l_" c Eo_E o�<oao EE otv@vy" �nu_E� .. Eo R`_°s z O H a U U W z O rn J Lu W O � lo� Lu O W Q o OC) U _J LL rn > W LL z 000 W J � � 0 00 O Z �W co 2 0 U7 W U) i O w _j N Z w_ N. W® J N m o gw N t - 3 I..LC ZWUN EL6 W W DATE: SCALE: 3/11/2021 NONE DESIGNED: DRAWN: JMD MLC CUz LAYOUT 7 SHEET: CLASS 600 598802 1 OF 1 1610 B4 V1600-4 Assembly CUSTOM LOGO 1/2" SAN SERIF BOLD FLAT FACE LETTERS BLANK TAG AREA 7/8" DIA HANDLING HOLE �(2) CLOSED PICKHOLES 1 1/2" 6) 7/8" DIA VENT HOLES UCIDA SANS IE LETTERING 31 7/8" DIA 1 3/8" 3/4" 1„ 3" 26 9/16" DIA COVER SECTION ,AWft\ a ICI / �►�► =1 Product Number 41600484 Design Features -Materials Cover Gray Iron (CL35B) Frame Gray Iron (CL35B) -Design Load Heavy Duty -Open Area n/a -Coating Undipped -✓Designates Machined Surface Certification ASTM A48 -Country of Origin: USA Major Components 00180783 41600419 33 1 /8" DIA 1 3/8" 32 1 /8" DIA - � 4,� Drawing Revision 11/19/2007 Designer: DEW 1/2" 6/20/2017 Revised By: DAE f f Disclaimer 1 3/8" Weights (Ibs./kg) dimensions (inches/mm) and drawings provided for your guidance. We reserve the right to modify specifications without 30" DIA prior notice. CONFIDENTIAL: This drawing is the property 32 1 /8" DIA of EJ GROUP, Inc., and embodies confidential information, registered marks, patents, trade secret information, and/or know how that is the property of EJ GROUP, Inc. Copyright© 2012 EJ GROUP, Inc. 42" DIA — All rights reserved. FRAME SECTION Contact 800 626 4653 ejco.com 41— Prod.\Recessed Lock H20\DHT3648AL H2O (6in.) w-Rec. Lock Box 071618 Lockbox Plan View 3/8 x 4 S.S. Flat bares (to be welded to sides of pocket) j^ 2x2x1/4J Gusset Detail Extruded Angle Frame 3 d dQ E $ 1 1/2 x 2 x 1/4 Angle (channel support) — Beam Por`4-+ doles tror 112" S.S. Bolts 6 places) -1/4" Aluminum Tread Plate Cover 3" Channel Detail Alum. Channel Bracing Stainless Steel Compression Springs Stainless Steel Lockbar w/Handle Neoprene Extruded Aluminum Trough Frame Gasket w/Continous Anchor Flange Extruded Trough Frame - I I I I I I l 1 6" �_----_i Frame Height m, /4 r4 Plastic Debris Plug Stainless Steel Slamlock w/Plastic Debris Plug 4' Tread Plate Covers Trough Frame w/ Continuous Anchor Flange See Note "A" for Pocket Requirements NOTE "A" Beam Support Pockets Must be Secured with 1/2" Dia. Concrete Inserts or Anchor Bolts to Maintain Load Requirements. Failure to do so will cause Load Failure and Void Manufacturers Warranty. Channel I See Note "A" for Pocket Requirements Skirt I \1-1/4" Stainless Steel Beam Pocket — L11-2 Gusset 1/4" Aluminum Tread Plate Cover \-6" Beam Frame and Pocket Detail 1 m T � E C = o .6 m o3m��� m H o c¢ N 2 Zo a C 0 N U O Z N cli v n 10 00 •' p1 � I x V U n 04 t 0s b d � a � rn C'2 a"i E x �0 A d N ° m D E U M K W � ® m o m 4) ° j5 a"'xw ° oM V N OD 0 a Y m - n o Q m w Lo a Date: 02-13-20