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Home My WebLink AboutSWP272266(15) i 1 Final Report 1 1 Design Report g p 1 for the 1 NE 10th Street/Anacortes Avenue NE Detention Pond and Storm System Improvement Project 1 Prepared for 1 � ! V 0 City of Renton E-f 6 P T �1�Y;;R 1 1 0� Gf � H June 2004 1 ! 1 1 FILE Copy 1 CH2MHILL CH2M HILL P.O. Box 91500 1 Bellevue,WA 98009-2050 1 Final Report Design Report for the NE 10th Street/Anacortes Avenue NE Detention Pond and Storm System Improvement Project N Submitted to City of Renton Y O� A�oF wAsy�ti O June 2004 � 3957 6� ExwAts 4/25/ 66 r CH2MHILL Contents 1.0 Introduction.............................................................................................................................1 1.1 Project Description and Objective...........................................................................1 1.2 Project Limits .............................................................................................................1 1.3 Project History...........................................................................................................2 2.0 Existing Conditions................................................................................................................6 2.1 Conveyance System..................................................................................................6 2.2 Hydrologic and Hydraulic Analysis.......................................................................6 3.0 Proposed Conveyance and Detention System.................................................................10 3.1 Detention Pond Description..................................................................................10 3.2 Conveyance Description and Hydraulic Modeling Results..............................13 3.3 City Maintenance Improvements..........................................................................19 3.4 Utility Conflicts........................................................................................................22 4.0 Conclusions and Recommendations..................................................................................23 4.1 Conclusions..............................................................................................................23 4.2 Recommendations...................................................................................................24 5.0 References..............................................................................................................................25 Appendices A Technical Memorandum No. 1 B XP SWMM Hydrologic and Hydraulic Modeling Data-Input Data and Results Tables 2-1 Existing Conditions-XP-SWMM Model Pipe Nodes,Segments, and Descriptions....7 2-2 Existing Conditions-XP-SWMM Model Results ..............................................................8 3-1 Detention Pond Control Structure and Overflow Elevations........................................11 3-2 Proposed Design-Detention Pond and Upsized Conveyance System(18-inch and 30-inch Pipes) XP-SWMM Model Results.................................................................15 3-3 Proposed Design-Detention Pond,Upsized Conveyance System, and City Maintenance Improvements XP-SWMM Model Results................................................19 3-4 XP-SWMM Hydraulic Output Summary Results: 2-,10-, 25-, 100-year Storm Events,Final Design Considerations.................................................................................20 4-1 Summary of Existing and Proposed Conditions with City Improvements for the Design Storm Events XP-SWMM Model Results.............................................................25 Figures 1-1 Project Location Map.............................................................................................................2 1-2 Drainage Basins and Existing Conveyance System...........................................................4 3-1 Detention Pond Surface Water Elevations........................................................................12 3-2 Detention Pond Stage-Storage Curve................................................................................12 SEA3100928236.DOC/041660002 iii FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 3-3 Detention Pond Stage-Discharge Curve............................................................................13 3-4 Proposed conveyance System.............................................................................................16 3-5 XP-SWMM Model Schematic Proposed Pond and Conveyance System.....................18 3-6 Hydraulic Grade Line Elevations for Node N3-25-Year Storm Event........................21 3-7 Hydraulic Grade Line Elevations for Node N7-25-Year Storm Event........................21 SEA3100928236.DOCI041660002 IV 1.0 Introduction 1.1 Project Description and Objective This report summarizes the results of Phase 5 of the NE 10th Street/Anacortes Court NE Storm System Improvement Project located in Renton,Washington.The project analyzes the proposed improvements to the storm water drainage system in the NE 10th Street and Anacortes Court NE area and determines the reduction of flooding frequencies for the area. ' The project includes construction of a detention pond on the property purchased by the CITY(the Vuong property),and upgrades to a portion of the storm water drainage system in the street. The project also includes the following maintenance improvements to the existing storm water drainage system designed by City staff as part of the City's effort to upgrade the overall system: • Replacing 260 LF of the existing 18-inch drainage pipe from the NE 11th Street and Whitman Court NE intersection north with new 30-inch pipe. • Replacing the existing siphon in Whitman Court NE with a new 30-inch pipe. The objective of this project is to design a system of detention and conveyance improvements so that the proposed system will reduce the flooding frequency in NE 10th Street,Anacortes Court NE,and Anacortes Avenue NE for design events up to the 25-year return period storm event. In addition to reducing flooding,the proposed system improvements should not increase the peak flow rates to Honey Creek. This report will include the following information: • Description of the layout and design of the proposed detention pond and stormwater drainage system improvements • Documentation of the level of protection and quantification of the amount of flooding that can be reduced by the improvements. • Hydrologic and hydraulic modeling results and calculations • Recommendations of the project effectiveness and feasibility. 1.2 Project Limits The project area is located in the northeast corner of Renton,WA and is roughly bounded on the north by Sunset Boulevard,on the east by 138th Avenue SE, on the south by NE 10th Street,and on the west by Union Avenue NE (see Figure 1). The proposed detention and storm water system improvements will occur along: NE 10th Street from Anacortes Court NE to approximately 300 feet east of the intersection with Anacortes Avenue NE;Anacortes Avenue NE from NE 10th Street to NE 11th Street,and NE 11th Street from Anacortes Avenue NE to Whitman Court NE. The drainage area for the system is approximately 63 acres, and contains approximately 22 percent multi-family residential,50 percent single-family residential (4 units/acre), and 28 percent open space and low density residential. SEA3100928236.DOCl041660002 1 FINAL DESIGN REPORT FOR THE NE LOTH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT FIGURE 1-1 Project Location Map Final Design Report K, - — B HE H 1. - O 7k111 lmi str+ 1�Newca iee ilk 1_ M 3,U f ...P�.. y rf%„d9 4 Se 128t Re _OI tit- _ _ '•q--' —e• 1�,tery oad— laple00 d eight ark.. aL pte z, ,tE I i1o,ft ` 'v 01999 Mapquest.00m,Inc.;01999 Navpation Tech nobgiq QQ) (e 1.3 Project History The location of the existing storm water drainage system and the basins evaluated for this project is shown in Figure 1-2. The storm water drainage system begins at NE 10th Street and 138th Avenue SE (Duvall Avenue NE), and discharges to a culverted segment of Honey Creek south of the intersection of Sunset Boulevard and Whitman Court NE. The culverted section of Honey Creek outfalls to the open stream channel northwest of the intersection of NE Union Avenue and Sunset Boulevard. Recurring flooding problems have occurred in Anacortes Court NE,and in NE 10th St from its intersection with Anacortes Court NE to its intersection with Anacortes Avenue NE. The topography is such that some of the properties in Anacortes Court NE are at lower elevations than the street and curb.When flooding has occurred,water has inundated Anacortes Court NE,and has flooded homes at the low point in the Court by overflowing the sidewalk and/or through direct hydraulic connections to existing yard drainage systems on the residents'property. The City's Surface Water Utility Section and the Maintenance Division have collected data and inspected the drainage systems to determine probable causes of the flooding. The evaluation indicated that the majority of the existing storm water drain system appeared to be undersized for current conditions,and may need to be replaced with larger conveyance pipes to meet current City design standards. CH2M HILL was initially contracted by the City of Renton in April 1995 to perform Phase I ' of the study. In a report entitled "Drainage Improvement Plan—NE loth Street/Anacortes S EA3100928236.DOC/041660002 2 FINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT Court NE Storm System Improvement Project" (CH2M HILL, 1996) (hereinafter referred to as the DIP),8 conceptual solutions were evaluated to reduce the frequency of flooding in Anacortes Court NE and NE 10th Street. The preferred solution selected by the City was a series of pipe size upgrades and replacement of the existing siphon at the northern end of the project. In October 1996,CH2M HILL was contracted to proceed with final PS&E of the selected design(Phase 2). In May 1997,shortly after the 75 percent design submittal, the Washington ' State Department of Fish and Wildlife (Fisheries) refused to issue a Hydraulic Project Approval for the project due to potential impacts to fish in Honey Creek and May Creek from the increased flow rates from the upsized storm system. After numerous discussions with Fisheries,the City decided to revise the project to include construction of a detention pond so the peak flow rates to Honey Creek would not be increased by the storm system improvements. In the fall of 2000,the City negotiated with a private property owner (Vuong) to purchase the detention pond property contingent on its suitability for use as a detention pond. The City contracted with CH2M HILL to perform Phases 3 and 4 of the project. Phase 3 included flow monitoring,calibration,and verification of the hydrologic analysis conducted as part of the DIP. Phase 4 included.a property boundary survey,wetland investigation and delineation,and geotechnical investigations for the detention pond site. The Final Wetlands and Geotechnical Reports were delivered to the City on October 25,2001. In December 2001, the City executed the Purchase and Sale agreement for the detention pond property. In August 2001,the City executed a contract with CH2M HILL for Phase 5 of the project to complete PS&E of the revised design to include the detention pond. The following CH2M HILL reports supplement this design report and should be referred to for more detailed information: Drainage Improvement Plan—NE 10th Street/Anacortes Court NE Storm System Improvement Project,"March 1995. 0 "Flow Monitoring Report for the NE 10th Street/Anacortes Avenue NE Storm System Improvement Project," May 2001. • "Wetland Delineation and Classification Report for the NE 10th Street/Anacortes Avenue NE Storm System Improvement Project," October 2001 r • "Geotechnical Report for the NE 10th Street/Anacortes Avenue NE Storm System Improvement Project,"October 2001. r r SEA3100928236.DOC/041660002 3 CONTROL DATE:10:54:04 25-AUG-19% O1AO1.DLV 9,87-5 9,67-4 L1.j u-" 9.D8-16 I 8.17-CUL9,138 �--1 1 7-13 9.F7-6 9-,IB7 5A -5 Of 9,C8-16 9,D7-6 A97 8 9,137 58 -9.138-4 9,C8-17 9.07-3 8,H 9.C8-13 D7-9 1, 9. 988-7 9.D8-12 I F7-5 19-77 14 9.E8-6 C8-4 B8-3 9 9,F8-3 A 9 D8- _j 'D8-15 8- 9.8f 9. Lai 81 3-CUL D8-7 9.E8 a 9.C8-4 88 8 -6 19,C8-26-' 9.C8-22 %E8 4 w 9.C8-20A F- C> A Z 8-5 9,D8-1 818-1 988-1,31 i W'CULV4� 9.C8-3 i 9.D8-8 9,C -201B 9,D8-1 f 4 9.E8-3 0- i 9.1`8-2 '1D 9.c8-2 9 1 i ' I - 0 9,88- 9,F8-11 A C� 9 C L 10 9.D8-2 0. 0 9,D8-5 iD8 C-,J 9 -4 9D8-3 9.D8-10 13,H2-3 9UP-18A: 0.19 8 8 C8,Ll Z--- 9.C8-1 r ------- _"j 9 9,D8-14 13.12-i t AREA: 2.39 Ac . ........ I'i F2- AREA: 4.36 Ac 6 14.F2-3 i4.C2-1 2 14,C2-3 -8 7 LIC -- 14.C2-4 Ld 14,132-4 14,C2 2 T- 2 AREA: 2.54 Ac 4,F2-2 4,132-2 -3 14,12 H '1C T 7 14.C2-6 4.C2-7 14 w CITY OF 13.1-13-5frl AREA: 2.19 Ac AREA: 2.38 Ac 14,F2-1 2- J 11 B < 14,C3-,l* 14,C3-7 KIN� '71 1(r, RENTON KING 3- COUNIY 6 01 EA: 6.t3 Ac A 6' COUNTY *14,D3- 14,F3-1 13,13-1 3 If C -- \ I 14, TO;tAL BAS IN I -12T' 3-101 ! 1 1 %LLI- AREA: 63.27 Ac if % 14,F3-2 . _ D Lu 14,F3-3 14,B�_2, 74 C 9 '•y € 6. Ac 1 3-1 ........... 8 14 ARE 3. Ac I 14,C3-3 13-4'1 f 5 14.C3-4 14,C3- F3-5 *14,D3- 14 NE ITC3-1", AREA T 14,F3-6f 146 AC, 4-7 f AREA. 12.78 Ac 14.1`3-7f E-, lei L 14.84-5 14.D4-3 14.F3-8 13,H4-6 _J L C4-3 -------ZT- 11.14 1 L---L4�Lji SE % N A 14,F4-5 ST LL1 14,C4-li 13 F AREA: TRPCTURE ........... EA: 15 Ac 15 SWALE *14,C4 AREA: 4.96; AC 2 1�H4-4 f 14,F4-2 4.6-� 2 ILI Ljj I 147B74-T-'jt---j I k -T.4 T MLKCHURCH 31 Arlindole 11PIdt 14,E4- j C Il Y OF M R N1014 14,E4-10 14,F4-3 % KING 14.E4-1 % COUNTY 14,F4-41 %--- 'F 7 14.E4-2 S 14 E4-8 14,E4-6 LEGEND E 4-1 j ------- DRAINAGE BASIN BOUNDARY S T 14 F 14,E4-5 SUBBASIN BOUNDARY 14.E4-3 4,F5- u? 1 3 10 ........................ SUBBASIN DESIGNATION f Lij D"-9 9� 9.F8- 3 94D 8-9 P.D7-9 ! _'5 D8 E. D8_8 F8 2 9. 9 8_ 9D 6 F 1 D8-5 D8 F 3131, I- 1�1 I I 1 95 NODE LOCATION & NUMBER 14.F5-2 O 150 300 450 @14.64-2 CITY OF RENTON MANHOLE I.D. NUMBER SCALE V=300' CITYW OF RENTON, FIGURE 1-2 EXISTING FACILITIES NOT FOUND IN FIELD ASHINGTON Drainage Basins and Existing Conveyance System A N.E. LOTH STREETNACORTES COURT STORM SYSTEM IMPROVEMENT PROJECT Final Design Report FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 2.0 Existing Conditions 2.1 Conveyance System The existing storm water drainage system in the project area consists of street inlets connected to the main storm water line as shown in Figure 1-2.The storm system main pipes range from 12-inches to 18 inches in diameter.There is a siphon in the system in Whitman Court NE,about 100 feet before the storm system connects to a 58"x 36"CMP arch pipe through which Honey Creek runs. In most locations,street inlets are connected to the storm main with 6-inch diameter pipes. A private open channel system is located in the southeast section of the drainage basin at the Martin Luther King Church.A flow control ditch captures stormwater runoff from the Church development(located at the far west side of subarea 15),as well as the other uphill sections of subarea 15(see Figure 1-2).A flow control manhole provides limited detention of the surface water runoff flows from the Church property prior to discharging into the 12-inch storm pipe in NE 10th Street. A complete description of the existing drainage system with profiles can be found in the DIP.As described in the DIP,the storm system pipes are undersized for the drainage areas, and also have shallow inverts along NE 10th Street.Flows from subareas 13, 14, 15 and 12 converge at Node N3 at the intersection of NE 10th Street and Anacortes Court NE. At Node N3 the manhole is relatively shallow,and during peak flows the hydraulic grade line will exceed the ground elevation,potentially leading to flooding of the street and several adjacent lots in Anacortes Court. During the final design of the project,several pipe size discrepancies were discovered in the existing basemap.After reviewing the existing as-built drawings and other survey information,the discrepancies were verified and corrected in the final version of the drawings,as well as in the computer model.A description of the hydrologic and hydraulic modeling analysis and results are described in the following section. 2.2 Hydrologic and Hydraulic Analysis Rainfall/Runoff computer modeling was performed using the XP-SWMM 2000 model for the existing and proposed stormwater system with the calibrated hydrologic parameters developed in Phase 3 of the project.The Stormshed/Waterworks model was used during the original DIP and during calibration under Phase 3;however,this model is limited because it does not accurately predict a backwater profile. The XP-SWMM 2000 model is a dynamic model that can predict backwater profiles and surcharging in the system,and is better suited for the alternatives analysis. XP-SWMM 2000 also uses the Santa Barbara Urban Hydrograph Method which is consistent with the CITY requirements. The existing storm water drainage system was modeled as part of the DIP,and calibrated and verified as part of Phase 3. The original storm drain system(nodes and pipes)as set up ' during the DIP(Phase 1) and calibrated hydrologic parameters obtained during Phase 3 were set up in the XP-SWMM model,and served as the basis for all Hydraulic and Hydrologic calculations for this design report. Preliminary modeling results were summarized in Technical Memorandum No. 1,which is included in Appendix A. In that SEA3100926236.DOC/041660002 6 FINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT report,a series of detention and conveyance improvements that would reduce flooding are described,as well as the model development. Figure 1-2 shows the existing model layout. The locations and nomenclature of the pipes,nodes,and subbasin areas are identical to those described in the March 1996 DIP prepared by CH2M HILL. Stormwater runoff from the 2-, 10-,25-and 100-year recurrence interval,24-hour design storm events was routed through the existing stormwater drainage system using the XP- SWMM model,and the resulting frequency and locations of flooding as well as peak flow ' rates discharged to Honey Creek were recorded. The effectiveness of constructing a detention pond along NE 10th Street and upsizing portions of the storm drain system was determined by altering the calibrated model to reflect these changes and routing design storm events through the proposed storm water system improvements. Since the original modeling was conducted as part of Technical Memorandum No. 1,the current model has been updated with correct pipe sizes (as described in the previous section),the addition of a new node at a low point along NE 10th Street(Node N2A),and the addition of the MLK Church flow control ditch for drainage subarea 15. As-built drawings of the Church and flow control structure,as well as recent survey information, ' were used to model the Church swale system. Table 1 lists the nodes and pipe segments for the updated pipe network. TABLE 2-1 Existing Conditions-XP-SWMM Model Pipe Nodes,Segments,and Descriptions Pipe Upstream Downstream Pipe Size Length Node Node Pipe ID (inches) (feet) Description Upstream segment beginning at Duvall Avenue N1 N2 P1 12 590 and ending at the junction catch basin at NE10th and the MLK Church SW_Up SW_Dn Swale' - 250 Church swale SW Dn N2 SW CntrlStr' 25 2C is the flow control structure N2 N2A P2 12 230 Church to Anacortes Ave. NE and NE 10th N2A N3 P2A 12 230 NE 10th Street,from Anacortes Ave. NE to Anacortes Court NE N3 N4 P31 12 275 Between homes from NE 10th Street to NE 10th Place(shown as 18"on the original basemap) N4 N5 P41 15 220 Along NE 10th Place(shown as 18"on the original basemap) N5 N6 P5 18 410 Between homes and in cul-de-sac from NE 10th Place to Whitman Court and NE 11th Street Along Whitman Court from NE 11th Street, N6 N7 P6' 18 285 north,adjacent to the apartments(originally 250' long) Along the Whitman Court right of way north N7 N8 P7' 15 128 adjacent to the apartments(shown as an 18"on the original basemap) SEA3100928236.DOC1041660002 7 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT TABLE 2-1 Existing Conditions-XP-SWMM Model Pipe Nodes,Segments,and Descriptions Pipe Upstream Downstream Pipe Size Length Node Node Pipe ID (inches) (feet) Description N8 N9 P8' 15 170 Along the north end of Whitman Court(shown as an 240 feet of 18"on the original basemap) 1 N9 N10 P9 18 60 Along the north end of Whitman Court N10 N11 Siphon (2) 12 30 Siphon ' N11 N12 P11' 18 94 From the siphon to the discharge culverts (shown as a 24"on the original basemap) Note: 'Updated and/or added pipe segments from the model used in Technical Memorandum 1 The existing conditions storm drain system was modeled for the 2-,10-, 25-, and 100-year ' storm events. Table 2-2 shows the results of the model runs and includes predicted peak flow rates from the storm drain system reaching Honey Creek (Node N12) and the locations that flooded during each rainfall event(noted by model node number, see Figure 1-2). The modeling results show that flooding occurs at Nodes N2,N2A,N3,N7,and N8 (see Figure 1-2). Node N2A is the manhole in the intersection of NE 10th Street and Anacortes Avenue NE,Node N2 is the manhole 200 feet east of the intersection of NE 10th Street and Anacortes Avenue NE (in front of the MLK Church driveway),and Node N3 is the manhole at the intersection of NE 10th Street and Anacortes Court NE. Flooding historically occurs at Nodes N2,N2A,and N3,but has not been observed at Nodes N7 and N8. Nodes N7 and N8 are further downstream in the system,in Whitman Court adjacent to an apartment complex. TABLE 2-2 Existing Conditions-XP-SWMM Model Results Est. Est. Duration Duration of of Flooding at Flooding at Flood Peak Flow Flood Node N3 and Nodes N7 Volume to Honey Rainfall Locations Node N2A and N8 at N8 Creek Rainfall Event (inches) Storm Type (Node#) (hrs) (hrs) (ft3) (cfs) 2-Yr,24-Hour 2.0 SCS Type 1A N3 1 - 0 13.9 10-Yr,24-Hour 2.9 SCS Type 1A N2, N2A, 6 1 10,500 14.8 N3, N7, N8 25-Yr,24-Hour 3.4 SCS Type 1A N2, N2A, 12 2 30,300 15.3 ' N3, N7, N8 100-Yr,24-Hour 3.9 SCS Type 1A N2, N2A, 17 3 44,500 15.8 N3, N7, N8 SEA3100928236.DOC/041660002 8 r FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT The Peak Flows to Honey Creek shown in Table 2-2 are the target maximum flow rates for the flows resulting from any improvements made to the storm drain system.In addition to Nodes N2,N2A,and N3,the calibrated model shows Node N7 and N8 flooding during events greater than or equal to the 10-year,24-hour rainfall event.In reality,flooding has not been reported or observed by the City at Nodes N7 and N8.Without conclusive evidence of flooding,it was decided that there was no need to include the elimination of flooding at Nodes N7 and N8 as a design consideration. However,as a secondary goal,the model results should show that any changes to the storm drainage system will not increase ' flooding at any node locations. r i r r i i 1 1 i SEA3100928236.DOC/041660002 9 FINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 3.0 Proposed Conveyance and Detention System 3.1 Detention Pond Description ' In December 2001,the City purchased the western half of the Vuong property to construct a detention pond.The property is located on the north side of NE 10th Street and consists of approximately 1.14 acres of gently rolling terrain with one isolated wetland in the center- south section.There is also an offsite wetland within 50 feet of the northwest corner. Refer to the CH2M HILL October 2001 Wetlands and Geotechnical reports for additional information about the site. The detention pond has been designed and sized to maximize the space available at the site, while maintaining geographical constraints of the drainage area.Based on a topographical analysis of the pond site and preliminary review of the hydraulic conditions of the system, the stormwater flows from subbasin areas 12 and 15(See Figure 1-2) can be routed into the pond for detention. It was not feasible to route flows from the areas west of the pond site (subbasin areas 13 and 14)because the areas are lower in elevation than the pond site and the potential depth of the inlet pipes would exceed the anticipated elevation of the pond bottom and outlet pipes. The pond design follows the design guidelines and requirements for a detention pond design as set forth in the King County Surface Water Design Manual(King County,1998). The existing catch basin in NE 10th Street(Node N2) located at the southeast corner of the site will serve as the junction structure to route stormwater flows from subbasin 15 (the MLK Church area) into the proposed pond.A new pipe will convey storm flows from Node N2 north to the pond.To convey flows from the east(subbasin 12),a new catch basin (Node N1A)will be constructed over the existing 12-inch pipe just east of Node N2,and a new pipe will convey storm flows from the catch basin north into the pond. On the MLK Church property there is a private system consisting of a ditch and flow control structure which is designed to reduce stormwater flows from the Church parking lot and building roof drains.Since the ditch is the lowest area of the property and connected hydraulically to the storm drain system(via Node N2),the proposed detention pond maximum water surface elevations were designed to take the ditch berm elevations into account and not cause overtopping in the ditch due to backwater conditions in the pond. The lowest elevation of the westernmost berm of the ditch is elevation 412.8,as identified during surveys performed by CH2M HILL in 2003. It should be noted,however, that according the MLK Church design drawings,the maximum water surface elevation in the berm was set to the approximate elevation of 413.8,which is incidentally higher than the low point in the side berm. The MLK Church ditch elevations are one of the primary controlling factors in the pond design. A pond design water surface elevation of 411.5 and bottom elevation of 406 with 3:1 side slopes was determined to be sufficient to contain the 25-year storm,and would not cause overtopping of the Church ditch.The computer model shows that the pond can contain the runoff volume from the peak flow for the 25-year storm,but will start to spill into the overflow riser pipe at storms greater than the 25-year storm volume. SEA3100928236.DOCI041660002 10 FINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT From elevation 406 to elevation 411.5,the pond has an active detention volume of approximately 1.7 ac-ft.The flow control structure will be the standard CB Type II ' (54-inches in diameter),with two orifices: a bottom orifice 1.5 inches in diameter;and a second orifice 4 inches in diameter at elevation 410.5.Two orifices were used so that the pond would detain more runoff volume from smaller storms (2-to 25-year),and release ' flows at a higher rate during the more extreme events.Therefore, overflow is expected to occur during the 100-year storm event. The top of the 18-inch riser pipe will be set at elevation 411.5.The proposed outlet from the flow control structure and pond to the ' downstream system will be an 18-inch pipe. There will be two additional emergency overflow spillways for the pond. Because NE 10th Street is higher than the pond,it is not possible to provide an overflow spillway to the street. The primary emergency overflow structure will be a birdcage manhole structure (CB Type II,48-inches in diameter).The structure will be connected to the new 18-inch outlet pipe, downstream of the flow control structure. The second emergency overflow structure will be a spillway constructed at the northwest corner of the pond,and set to overflow only if both the riser pipe and primary overflow structure are unable to provide flow relief. The spillway will be designed to pass the peak flow rate from the 100-year storm, and it will convey flows to a low area and intermittent stream channel north of the pond site. Table 3-1 summarizes the flow control and spillway elevations,and Figure 3-1 displays the pond water surface elevations during each of the four storm events. Figure 3-2 shows the pond stage versus storage volume for the proposed pond,and Figure 3-3 shows the pond stage versus discharge rates. Figures 3-2 and 3-3 show that at an elevation of 411.5 (just before overflow) the pond has a storage capacity of 82,600 cubic feet(1.9 ac-ft) with a maximum discharge of 0.6 cfs,respectively. ' TABLE 3-1 Detention Pond Control Structure and Overflow Elevations ' Description Elevation(ft) Top of Pond Berm 413.5 Maximum Water Surface 412.5 Secondary Emergency Overflow Spillway 412.2 Primary Emergency Overflow Structure(Birdcage) 411.5 Top of Flow Control Riser 411.5 Design Water Surface Elevation of Second Orifice 410.5 (4"diameter) Invert of Pond(bottom of detention) 406.0 Elevation of First Orifice(1.5"diameter) U9 = 1. �C SEA3100928236.DOC/041660002 11 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT FIGURE 3-1 Detention Pond Surface Water Elevations ' Final Design Report 412 Overflow Elevation-411.51 I 1 I I I I t I 1 I 411 ----r--------r---r----,----r- -r--- --r---r---�-- - ---- 1 I I I I I I I I 1 1 I 1 I I 1 I I I 1 I I I 1 I I I 1 I 1 1 1 1 I I I I 1 I I I I 1 I I 1 I 1 I I i 1 I I I I I 1 1 I 1 I I I I 1 I I I 1 I I I I i 1 I 1 I I 1 I 1 1 I I I I W I I I I I I I I I I I 1 1 I I I I I 1 i I I I 1 407 ---1--------1-- -- -I----I----�'---�----I---- ----I----1----L --- ----I I I I I I I ' __._. —100-yr �25-yr —10-yr —2-yr I I I , I I I I I I I I I I I I I I I I I I I I I I I 405 0: i I 1 I I i I I I 1 I I 00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 Time ' FIGURE 3-2 Detention Pond Stage-Storage Curve ' Final Design Report 140000 1 I I 120000 --- r,- -r r- tI --------rI - --7i-------- 1 I I I I I tPond 1 I I i I I I I I I E ' 80000 > -------- -------- --------p --------+--------+-- -----4----- I I i I i --- , I 1 60000 _!______-__>_- _-L_ _--___1____-___�__ _ 1 I I I I I i I I I i i I I I I 1 40000 - ---___L__-_____L____-___ 1-_______ I I I I I I I 1 1 I I i I I I I I I I 1 I 1 20000 ----__L____ L________1_-___-__1_____--_1________1________ I I I I I I I I I I I I i 406 407 408 409 410 411 412 413 Elevation SEA3100928236.DOC1041660002 12 ' FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT FIGURE 3-3 Detention Pond Stage-Discharge Curve ' Final Design Report 2.00 1 I I I 1 I I I I I I I I I 1.80 - ---------------- - ---------------------------------------1-------- ----- I I I 1 I I I I I I I I i I I 1.60 - ------------'----- ' -------'-------------'-------------'------- ----- —i—Pond I I I I 1 I I I I I I I I 1 I __I_____________I______- __--- 1 I 1 I I I 1 I I I w i I 1 1 I V 1 O LL I I I I I t 1 1 0.80 ------------------------------------------I-------------I------------------- ------ 1 I I I 1 I I I I I I 0.60 ----- ------- ------------'-------------'--------------------------'------ ------ 1 I I I I I I I I I I I I I 1 I 1 I I 0.20 --- - -------L------_. ------------I------- ----I------------- 1 I 1 0.00 406 407 408 409 410 _ 411 412 ' Elevation ' 3.2 Conveyance Description and Hydraulic Modeling Results In Technical Memorandum No. 1,the hydraulic modeling results for the detention pond ' only option indicated that the flooding frequency at Node N3 (NE 10th St and Anacortes Court NE)would be reduced for the 2-year,24-hour event,but flooding would still occur at the 10-year and higher rainfall events.The storm system downstream from the pond would still need to be upsized to reduce flooding at Node N3. The proposed project design is shown in Figure 3-4. The design includes upsizing the storm system from Node N3 to Node N2A to an 18-inch pipe,and installing a new 30-inch pipe from Node N2A to Node N4A to Node N6 (in Anacortes Avenue NE and NE 11th Street). The existing stormwater system from Node N3 to Node N6 would remain in service.At Node N3,the new 18-inch storm pipe would be installed at a lower elevation than the existing 12-inch pipe to the north(from Nodes N3 to N4),and would slope to the east to the new 30-inch pipe. This will allow the existing 12-inch pipe at Node N3 to convey flows only when the 18-inch pipe becomes surcharged,and will help increase overall flow capacity of the drainage system. The new 18-inch pipe in NE 10th Street from Node N3 to Node N2A was likely to conflict with two side sanitary sewers along the north side of the street. To avoid potential conflicts, the elevation of the 18-inch pipe was raised slightly higher than originally modeled so new side sewers could be reconstructed below the new storm pipe if a conflict occurred. SEA3100928236.DOCI041660002 13 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT The proposed project design is similar to the design previously completed by the CH2M HILL DIP.However,the proposed system connects into the existing system at Node N6,instead of upgrading the entire pipe system to the discharge point,as was part of the original design under Phase 2. Connecting into the existing invert elevation at Node N6 allows for construction of the new pipe system at an average slope of approximately 0.25 percent,which is slightly greater than the minimum recommended slope of 0.2 percent. Existing inlets along NE 10th Street,Anacortes Avenue NE and NE 11th Street will be ' replaced with new catch basins and connected to the new storm trunk line via 12-inch pipes. Where there are potential conflicts,or the cover over the new pipe is less than 2 feet,it may be necessary to use 8-inch pipes instead of 12-inch pipes. Most of the existing inlets use only ' 6-inch pipes to connect to the existing storm main. The XP-SWMM model schematic for the proposed project design is shown in Figure 3-5. Two additional nodes (N4A and N4B)were added to the model to represent the new 30-inch pipe along Anacortes Avenue NE and NE 11th Street. Node NO is at a low spot along Anacortes Avenue NE,and is used in the model to determine if flooding occurs at this critical location during peak rainfall events.The XP-SWMM modeling results for this design are shown in Table 3-2. Table 3-2 shows that the detention pond and conveyance upgrades significantly reduce the frequency and duration of flooding. The model predicts that Nodes N3 and NO will only flood slightly during the 25-year 24-hour rainfall event,and somewhat more so during the 100-year,24-hour rainfall event.The increase in pipe size,along with installation of the ' detention pond,will reduce the hydraulic grade line along the shallow areas around Node N2A and N3(NE 10th Street and Anacortes Court NE).The model indicates that Nodes N7 and N8 still flood during all storm events;however,the volume of water leaving the system ' at these nodes is slightly less than existing conditions. This shows that the detention pond is contributing to a reduction in flow rates.The upsized conveyance system helps to further reduce peak flow rates to Honey Creek,which is one of criteria for the new design. Reduction in peak flows rates to Honey Creek are estimated to be between 0.5 to 3.0 cfs. Table 3-2 indicates that larger reductions can be expected for the smaller,more frequent storm events. SEA3100928236.DOC/041660002 14 1 ' FINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT TABLE 3-2 Proposed Design—Detention Pond and Upsized Conveyance System(18-inch and 30-inch Pipes) ' XP-SWMM Model Results Est. Duration of Flooding at Est. Duration Flood ' Node N3 and of Flooding at Volume at Peak Flow Maximum Flood Node N413 Node N7 and Node N8 to Honey Pond Rainfall Event Locations (hrs) N8 (hrs) (ft3) Creek(cfs) Elevation(ft) ' 2-Yr,24-Hour N7,N8 0 <1 <100 11.8 408.8 10-Yr,24-Hour N7,N8 0 1.5 14,000 14.4 410.8 ' 25-Yr,24-Hour N3,N4B,N7, <1 2.5 30,200 15.0 411.5 N8 100-Yr,24-Hour N3, N46, 2 3 43,000 15.6 411.7 ' N7, N8 (overflows into the riser pipe) SEA3100928236.DOC/041660002 15 CONTROL DATE:10:54:04 25-AUG-1995 OIA01-DLV T 9,67-5 'D' 9.C8- 9,67-4 8,17-CU 1�16r - jj �9,E7-1� '9.68-5 -6 9.07-8 3.H8 ,9:87-5A 9,D7 9,147-3 9.C8-17 9,137-5B -9,88-4 7-5 8.148-2 9,D8-121 9.F 9,C8-131 D7 7 9,88-7 Oy 9,C8-14 9,E8-6 9.F8-3, �Lj -3 -j I %D8-15 9,D8-9 Fl ► 9,1318 9,B8-CUL < 9,D8-7 < 9,E8-5 q- yF 9,E8-4 9.C8-26' -9.131 -6 9,C8-22 9,C8-20A 9,C8-5 9,D8-1 Z-58"X3 9,C8-3 9,D8-8 9.FB-2 8,18-1 6'CULV: 9,C8-20B q.D8-1I 0 9,88-131 9,E8-3 0 9,F8-11 9,C8!21 9. -2 9,D8 0 9,88-15 9"C&.-I 0 9.C8-1 9,D8-5 -4 9,.08-3 13,H2-3 9 D8 18 0 9,08-1011 q C ---------- --- 13.H2-4 9.08-1 1312-1.. AREA: 2.39 Ac 14.F2- 4 14,F2- L.LJ 13.H3-"- 14,F2-3 13,1 AREA: 4.36 Ac 14,C2-3 14,C2-1 P U 0 14,F2-2 1 14,C2-4 2 AREA: 2.54 Ac LLJ I 14,B2-4 14,C2- 14,C2 4.1312-2 14,82-3 14(p w 4 14,C2-7 7 14,F2-1 ,.jH 'C T 1: CITY OF (D I i — I AREA: 2.19 Ac AREA: 2.38 A: 13,H3-5 - < M 2- 14,C3-7 KIN- Cc i RENTON rnm- i i - 0, Z COUN;!,1Y cn KING 0 COUNTY 7) Sj-1—JITH' A: 6,13 Ac A 14,F3-1 *14,D3-11 TO AL BASIN 13,13-1 AR A: 63.27 Ac I C -12 14. 3-10 14,8 -3 1 t.--- 14,F3-J 13-3'1 k 4,83-21 14,F3-3 C) 10 LLj 14.0 6.40 B3-11 I E �c 14,173-4, P�.......... 8 9 C C, *14,D3- 14.F3-5 -J C3 14,C3 4,C3- 43-4,,, r-7-5 14,C&';- L r POND 14,F3-61, • NE 4REM 1.4� A -7, AREA: 12.78 Ac ♦ ♦ 14,1`3-T!4 F 14,F3 14. �41 13, 4-6 1 14,84-5 -11 SE % 14,F4-5 I C4- 3 116TIHI.--.- ST ♦FLOW Ct / ,STRUCTURE AREA: .15 Ac F-i 5 4.C4-",, R 4. 14 F4 2 E� 14,F4- L i�.1l __;ST� ISWALEI �J4 A-H -SE1 4 B4-2. MLK CH1.M14' �14.B, 3 13,H4-31 14,E4-9 Arlindole 0101t CITY OF 4-10 1-F4-3 f...... �RENTON 14.E4 KING T 14,F4-4 COUNTY 14,F .7 14,E4-2,, 14,E4-8 14"' SEII 14,E4-4 118 LEGEND S T --------- DRAINAGE BASIN BOUNDARY L 4,E4-5 14,E4-3 LJ I 114,F5-3 SUBBASIN BOUNDARY C/) SUBBASIN DESIGNATION Lu 11.1`5-2 F8--3 4 9C8 4 �C191-5 9 'C8-3 1� �.I`8-2 9 .C8- F8_11 A, 05 NODE LOCATION & NUMBER 0 150 300 450 014.134-2 CITY OF RENTON MANHOLE SCALE 1"=300' CITY OF RENTON. FIGURE 3-4 I.D. NUMBER WASHINGTON Proposed Conveyance System -------- EXISTING FACILITIES NOT FOUND IN FIELD N.E. 10TH STREETANACORTES COURT Final Design Report :1 *14,C4-4 STORM SYSTEM IMPROVEMENT PROJECT tFINAL DESIGN REPORT FOR THE NE 10TH STREETIANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT FIGURE 3-5 XP-SWMM Model Schematic of Proposed Pond and Conveyance System Final Design Report N12 ' of I I N11 Siphon ' I N10 O 19 ' ,N9 G I ' P8 NS �t P7 N7 New 30" Pine 1 8 ' IN6 N4A 04 PN4A Na �,; ' 3 P14 -N4A New 18" Pine ' 4 N4 N48 o4—P4—t, Pond 1 � r ' 3 PN2A-N48 Pnd CntrSt N2 and N1A_Pond N3 I N2A Pnd_On I N1A PN3-N21 0— 04—P 0- N3 N1 04 Pt 0 a SW_CntrRtr � oUU-Dn 0 New 18" Pine Swale ' I SW—Up ' S c✓ P— MA'% SEA3100928236.DOC/041660002 18 ' FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 3.3 City Maintenance Improvements— Final Design As discussed in the first section,the City has incorporated several maintenance improvements into the design drawings.During the project design the City found substantial root intrusion problems in the existing storm water system between Node N6 ' and Node N7.The City Surface Water Utility decided to eliminate the root problem by replacing the existing concrete pipe between Node N6 and N7 with a new 30-inch pipe.The City also decided to remove the existing siphon in Whitman Court NE between Node N10 ' and N11 and replace it with a 30-inch pipe.The plans for the pipe improvements in these two areas were designed by the City of Renton Surface Water Utility,and were incorporated into the final plans and specifications for the project. ' CH2M HILL added the City's changes to the proposed computer model and ran it for the four peak storm events.The results of the analyses show that increasing the pipe size from Node N6 to Node N7 significantly reduced the hydraulic grade line along all the upstream ' pipe segments,and eliminated flooding at Node N3 for the 100-year storm event.The City improvements did not cause an increase in peak flows to Honey Creek. The model showed that the improvements slightly increase flooding at Nodes N7 and N8 due to the increase in ' flow rates through the pipe segment from 6 to 7;however,flooding has not been observed at these locations as described previously.The XP-SWMM modeling results for the final design with City maintenance improvements are shown in Table 3-3. ' Table 3-4 summarizes the peak flow and water surface elevations at each pipe node for the four peak storm events for the final design conditions. ' The results of the modeling runs for the three conditions: existing;proposed;and proposed with City maintenance improvements are shown in Figures 3-6 and 3-7. The Figures show the hydraulic grade lines at Nodes N3 and N7,respectively,for the 25-year storm event. ' TABLE 3-3 Proposed Design—Detention Pond,Upsized Conveyance System,and City Maintenance Improvements ' XP-SWMM Model Results Est. Duration Flood ' Est. Duration of Flooding at Volume at Peak Flow Flood of Flooding at Node N7 and Node N8 to Honey Maximum Pond Rainfall Event Locations Node N3 N8(hrs) (ft3) Creek(cfs) Elevation(ft) ' 2-Yr,24-Hour None 0 0 0 12.0 409.0 10-Yr,24-Hour N7,N8 0 1 13,600 14.6 411.0 ' 25-Yr,24-Hour N7,N8 0 1.5 24,000 14.8 411.6(overflows into the riser pipe) 100-Yr,24-Hour N7, N8 0 2.5 33,000 15.2 411.7(overflows ' into the riser pipe) Sl(6/y SEA3100928236.DOC/041660002 19 1 TABLE 3-4 ' XP-SWMM Hydraulic Output Summary Results:2-, 10-,25-,100-year Storm Events, Final Design Considerations Upstream Upstream 3 3 � Upstream Downstream s Peak Flow Upstream Water Peak Flow Upstream Water Peak Flow Upstream Water Peak Flow Conduit Name Node Node Ground Elev. Water Surface(ft) (cfs) Surface(ft) (cfs) Surface(ft) (cfs) Surface(ft) (cfs) Storm Event: 2-yr Storm Event: 10-yr Storm Event: 25-yr Storm Event: 100-yr Pi N 1 N 1 A 437.82 426.54 2.19 426.69 3.96 426.77 5.04 429.61 6.11 N1A Pond N1A Pond 419.90 411.32 2.18 411.88 3.90 412.75 5.02 413.85 6.11 Swale SW-Up SW-Dn 416.20 413.58 0.82 413.78 1.83 413.85 2.35 413.90 2.84 ORF# 3 SW-Dn N2 416.00 413.58 0.17 413.78 0.18 413.84 0.18 413.90 0.18 ORF# 4 SW-Dn N2 416.00 413.58 0.17 413.78 0.18 413.84 0.18 413.90 0.19 N2-Pond N2 Pond 414.22 409.01 0.56 411.64 2.10 411.65 2.31 411.69 2.73 ORF# 1 Pond Pnd_Dn 413.00 409.01 0.11 411.03 0.15 411.63 0.16 411.67 0.16 ORF# 2 Pond Pnd_Dn 413.00 406.17 0.00 411.03 0.23 411.63 0.40 411.67 0.40 P2 Pnd Dn N2A 413.50 406.17 0.11 406.31 0.38 406.56 1.24 407.10 1.59 PN3-N2A N3 N2A 410.38 406.96 1.98 407.18 3.08 407.40 4.19 407.74 5.75 PN2A-N4B N2A N413 410.55 405.78 2.01 405.90 3.13 406.39 3.84 407.08 5.27 PN4B-N4A N413 N4A 409.44 405.15 3.56 405.71 6.15 406.34 6.49 407.02 9.01 PN4A-N6 N4A N6 415.69 403.84 4.00 405.61 5.52 406.20 6.54 406.73 9.04 P3 N3 N4 410.38 406.96 0.86 407.18 1.89 407.40 2.22 407.74 2.13 P4 N4 N5 412.23 404.79 0.86 406.24 1.71 406.87 1.72 407.39 1.68 P5 N5 N6 413.58 404.09 2.39 406.04 3.92 406.72 4.59 407.30 4.84 P6 N6 N7 411.92 402.87 7.60 405.53 11.98 406.05 15.49 406.43 19.31 P7 N7 N8 405.50 402.78 8.92 405.27 11.30 405.50 11.55 405.50 11.55 P8 N8 N9 402.00 399.82 11.02 399.89 11.17 399.91 11.17 399.91 11.15 roadP8 N8 N9 402.00 399.82 0.00 399.89 10.09 399.91 8.49 399.91 10.04 ' P9 N9 N10 398.00 393.45 12.04 395.84 16.40 396.19 17.12 396.54 17.82 Siphon N10 N11 395.06 391.77 12.02 392.99 16.55 393.15 17.30 393.29 18.04 ' P 11 N 11 N 12 394.85 391.62 12.00 392.75 14.63 392.87 14.83 393.04 15.14 NOTE: ' ORF#1 and#2 are the lower and upper orifices, respectively,for the MLK Church swale flow control structure. ' ORF#3 and#4 are the lower and upper orifices, respectively,for the detention pond flow control structure. Road P8 is the street above pipe P8,which is modeled as a trapezoidal channel. 2 Indicates storage nodes. Modeled ground elevations are higher than actual ground elevations.Actual ground elevations: N3-409.8; N413-409.2; N7-404.8. 3 For the 25-, 100-yr Storms, Flow in P2 exceeds orifice flow due to overflow from the pond (pond water surface rises above El.411.5). SEA3100928236.DOC/041660002 20 i 1 FIGURE 3-6 Hydraulic Grade Line Elevations for Node N3—25-year Storm Event 412 ' Existing Proposed with City Maintenance I I I I I I I Proposed I 411 --___L_____1_____J__-___I __ _____L__ __________________ I 1 I I i I I I I I I I 1 I 1 I I I I I I I I I I I I I I I I 1 I 1 I i I I 1 I 410 -y��'feY�t14 4Qy�_ 1 I 1 I 1 I 1 i I I I I I I 1 I 1 i I I 1 1 I I 1 I I I I O 1 I I 1 I 1 1 I I I > 409 ___-_1___-_1_____J___ _ 1-_--__-_____L_____1_____J______I_____ I______L W 1 I 1 I I I 1 I 1 I I I I I 1 I I I 1 I I I 1 I 1 1 I I 1 I I 1 I I I I I I 1 I I I 406 ----__r_____Y_____�__ __ I__ ___r_____r_____Y_____�I______I_____ r_____ 1 I 1 I 1 1 1 I I I I I I 1 I 1 I 1 I I I I I I 1 I I 1 1 I I I I I I I I 1 1 I I I I 407 -_____ I I 1 _I _ _I______1 _____1_____ ______I-___-_L__ 1 I I I 1 1 I I I 1 I I 1 I I I 1 I I I 1 I 1 I I 1 I 1 1 I I I I I 1 I I 1 I I I I I I I I 1 I I I I 406 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time FIGURE 3-7 Hydraulic Grade Line Elevations for Node N7—25-year Storm Event 40s , Existing —Proposed with City Maintenance 405 1 —Proposed I I I I I I I I I I I Ground Elevation-404.8 1 I 1 I I I I I I I I 404 I I I I I I 1 I I I 1 __--_T ,___-__I_____ r __ __T_____i______I__--_-r_____T_____ ______i___ I I I I I I I I I I I I I I I I I I I I I I I 1 I I i I I I I I I 403 -----T-----I------1---- - ----- ------I------F -----T----- I i I 1 I I I 1 I r , I_______ I I I I C I I I 1 I I I 1 1 I I p I 11 1 I I 1 I I I I ~ ------ ----- ----'-1---- -�-- - ------------------ ----- ----- ------I--- > 402- I I 1 I I I I 1 N I I 1 I I I W I I I 1 I 1 I 1 I I 1 401 ----------------�---- -�--- ----- ------I------�----- ----- ------�--- i I I I I I i I I i I 1 I i 1 1 I I I I 1 I I I I i I I 1 I I I I I I 1 1 I I I 400 -----i------------1--- ----- ------ ---I------ ----- ----- ------I--- I I I 1 I I I I I 1 I 1 1 I I I I 1 I I 1 I I I I I I I i I I I 399 ..... _____i______�____-_I i I I I I I I I F I I I I I I I I I I I I I I I I I I i I I i I i I I I I I I 398 I I I I I I I I I I 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time SEA3100928236.DOC/041660002 21 FINAL DESIGN REPORT FOR THE NE LOTH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 3.4 Utility Conflicts As expected with a storm system in residential city streets,there are numerous locations where existing subsurface utilities may conflict with the new storm system design. Existing storm system pipe inverts (upstream and downstream) control the depths of the new storm system main line. Existing sewer mains paralleling the storm system in NE 10th Street and Anacortes Avenue NE also limit the depths of the new storm system. In NE 10th Street,and at the NW corner of NE 10th Street and Anacortes Avenue NE, there are three to four locations where the sanitary sewer laterals(side sewers)may need to be rebuilt under the new storm system.The storm system in these sections will have to be adjusted during the final design(i.e.,elevated)so that side sewers can be rebuilt under the storm sewer pipe(if necessary).One problem is that raising the new storm system means increasing the potential for overflows. However,with the City's maintenance improvements,the hydraulic grade line for the proposed conditions was significantly ' lowered and overflows were eliminated. There are also be a few unavoidable instances where existing water mains and gas lines will have to rebuilt over/under the new storm system. SEA3100928236.DOC/041660002 22 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 4.0 Conclusions and Recommendations 1 4.1 Conclusions Construction of the detention pond on the Vuong property provides a significant amount of flooding relief.However,the model analysis shows that the pond alone will not be sufficient to reduce flooding at Node N3 for the target 25-year design storm. Although the pond is able to reduce flows and flooding during the smaller storm events (2-year or less),the existing storm drainage system from Node N3 downstream is not sufficient to convey the remaining storm flows from the drainage basin,and the pipes become surcharged. Node N3 and Node N2A are at low points, and are where the hydraulic grade lines increase to elevations above the ground surface, and flooding occurs.Therefore,in order to lower the hydraulic grade lines,the outlet pipe from Node N3 will have to be upsized. In order to meet the goals of the project,and reduce flooding up to the 25-year design storm event,the proposed design includes upsizing a portion of the existing storm drain system and constructing a detention pond.The proposed design also helps to further reduce peak flow rates to Honey Creek. The addition of the City maintenance improvements also helps to reduce flooding during the 100-year storm event in NE loth Street and Anacortes Court NE, Table 4-1 shows a summary of the alternatives for the 100-,25-, 10-, and 2-year recurrence interval storm events. TABLE 4-1 Summary of Existing and Proposed Conditions with City Improvements for the Design Storm Events XP-SWMM Model Results Est. Duration Peak Flow to Flood of Flooding at Flood Volume Honey Creek Rainfall Event Condition Locations Node N3 (hrs) at Node N8 (ft3) (cfs) 2-Yr,24-Hour Existing N3, N7, N8 0 0 13.9 2-Yr,24-Hour Proposed N7, N8 0 <100 11.8 10-Yr,24-Hour Existing N2,N2A,N3,N7, 1.5 10,000 14.8 N8 10-Yr,24-Hour Proposed N7, N8 0 14,000 14.4 25-Yr,24-Hour Existing N2,N2A,N3,N7, 12 30,300 15.3 N8 25-Yr,24-Hour Proposed N7, N8 0 30,500 14.9 100-Yr,24-Hour Existing N2,N2A,N3,N7, 16.5 44,500 15.8 N8 100-Yr,24-Hour Proposed N7, N8 0 43,500 15.4 SEA3100928236.DOC1041660002 23 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 4.2 Recommendations 1 We recommend completing the proposed design,which includes construction of a detention pond,re-routing and upsizing the storm system main line from Node N3 to Node N6 along Anacortes Avenue NE and NE 11th Street,and construction of the City maintenance improvements. i t SEA3100926236.DOC/041660002 24 FINAL DESIGN REPORT FOR THE NE 10TH STREET/ANACORTES AVENUE NE STORMWATER SYSTEM IMPROVEMENT PROJECT 5.0 References CH2M HILL. 1996. Drainage Improvement Plan,NE 10th Street/Anacortes Court NE Storm System Improvement Project. Prepared for City of Renton,Renton,WA. March, 1996. King County Department of Natural Resources and Parks. Surface Water Design Manual. September, 1998. t 1 1 t t SEA3100928236.DOC/041660002 25 APPENDIX A Technical Memorandum No. 1 1 1 TECHNICAL MEMORANDUM 1 CH2MHILL City of Renton - Hydrologic and Hydraulic Analysis NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater System Improvement Project PREPARED FOR: Dan Carey,P.E. Ron Straka PREPARED BY: Reid Adams COPIES: Jerry Scheller Teresa Platin DATE: November 14,2001 Introduction The purpose of this project is to design and construct a detention pond on the property proposed for purchase by the CITY(the Vuong property) that will reduce the flooding frequency in the NE 10th Street,Anacortes Court NE,and Anacortes Avenue NE area. This memorandum summarizes the results of the Hydrologic and Hydraulic analysis (Task 2.1) that was performed to determine the feasibility of constructing a detention pond and meeting the project goals,and will help the CITY make a decision on purchase of the property and closing the sale. Rainfall/Runoff computer modeling was performed using the XP-SWMM 2000 model for the existing and proposed stormwater system with the calibrated hydrologic parameters developed in Phase 3 of the project. The Stormshed model was used during Phase 3, however this model is limited because is does not accurately predict a backwater profile. The XP-SWMM 2000 model can predict backwater profiles and surcharging in the system, and is better suited for the alternatives analysis. XP-SWMM 2000 also uses the Santa Barbara Urban Hydrograph Method which is consistent with the CITY requirements. Five storm system networks were modeled-one with the existing storm system and four with various improvements to the storm system. The five analyses included: 1. Existing System 2. Pond design(Alternative 1) 3. Pond design with upsized conveyance system(Alternative 2) 4. Pond design with upsized conveyance system(Alternative 3) 5. Upsized conveyance system only(Alternative 4) SEA3100928237.DOC/041660003 1 Objective The primary objective of this task was to determine what type of improvements to the existing stormwater system should be designed so that the proposed system will eliminate flooding in NE 10th Street and Anacortes CT for design events up to the 25-year return period storm event.In addition to reducing flooding,the proposed system should not increase the peak flow rates to Honey Creek. Model Development The existing storm drain system(nodes and pipes)and calibrated hydrologic parameters were set up in the XP-SWMM model, and served as the starting point for the computer model runs. Figure 1 shows the existing model layout. The locations and nomenclature of the pipes,nodes,and subbasin areas are identical to those described in the March 1996 Drainage Improvement Plan prepared by CH2M HILL(See Figure 3-1 Drainage Basin Boundary Map,attached).Stormwater runoff from the 2,10,25 and 100-year recurrence interval,24hour design storm events were routed through the system and the resulting frequency and locations of flooding as well as peak flow rates discharged to Honey Creek were recorded. The effectiveness of constructing a detention pond along NE 10+h Street and upsizing portions of the storm drain system was determined by altering the calibrated ' model to reflect these changes and routing design storm events through the proposed system improvements. In addition to the four design storms,the July 3,2000 storm event (used to calibrate the model as part of Phase 3)was modeled under existing and proposed conditions to determine how the system reacts to a higher intensity,shorter duration storm event(in contrast to the design storms)during which flooding actually occurred. Existing System The existing conditions of the storm drain system were modeled for the five storm events. Table 1 shows the results of these model runs and includes predicted peak flowrates from the storm drain system reaching Honey Creek and the locations(noted by model schematic node number) that flooded during each rainfall event. The XP-SWMM model schematic is shown in Figure 1. The model shows that flooding occurs at Nodes 2,3,and 8. (See Figure 3-1.) Node 2 is the manhole just east of the intersection of NE 10th Street and Anacortes Avenue NE and Node 3 is the manhole at the intersection of NE 10th Street and Anacortes Ct.NE. Flooding historically occurs at both of these locations. Node 8 is the manhole at the end of Whitman Ct. NE,further downstream in the system. The flows to Honey Creek shown in Table 1 are the target maximum flowrates for the flows resulting from any improvements made to the storm drain system. In addition to Nodes 2 and 3,the calibrated model shows Node 8 flooding during events greater than or equal to the 10-year,24hour rainfall event. Options to eliminate flooding at this location have not been considered,but as a secondary goal,any changes to the storm drainage system should not increase flooding at this location and were considered as part of the analysis. SEA/SEA3100928237.DOC/041660003 2 TABLE 1 Existing Conditions-XP SWMM Model Results Rainfall Event Rainfall Storm Type Flood Est. Duration Flood Peak Flow (inches) Locations of Flooding at Volume at to Honey Node 3 (hrs) N8(ft3) Creek(cfs) July 3,2000 0.87 Recorded N3 .8 0 13.6 Rainfall Event 2-Yr,24-Hour 2 SCS Type 1A N3 1 0 15 10-Yr,24-Hour 2.9 SCS Type 1A N2, N3, N8 6.3 7,800 18.1 25-Yr,24-Hour 3.4 SCS Type 1A N2, N3, N8 11 16,000 18.9 100-Yr,24-Hour 3.9 SCS Type 1A N2, N3, N8 16.5 26,600 19.7 Alternatives Analysis Design Alternative 1 — Detention Pond Description of Alternative A detention pond was preliminarily sized to maximize the space available at the Vuong property,while maintaining geographical constraints of the drainage area. Based on a topographical analysis of the pond site and preliminary review of the hydraulic conditions of the system, the stormwater flows from subbasin areas 12 and 15 (See Figure 3-1)could be routed into the pond for detention. It would not be practical or feasible to route flows from the areas west of the pond site (subbasin areas 13 and 14)because these areas are much lower than the pond site and the depth of the inlet pipes would require a very deep pond excavation. The existing inlet in NE 10th Street located at the southeast corner of the site served and the junction structure to route all the stormwater flows from subbasins 12 and 15 into the proposed pond. On the south side of NE 10f Street, there is an existing swale and flow control structure located within the Church property which is designed to reduce stormwater flows from the Church parking lot and building roof drains. Since this swale is the lowest area of the property and connected hydraulically to the storm drain system,the proposed pond maximum water surface elevations were designed to take the swale elevations into account and not cause overtopping due to backwater conditions. A design water surface elevation of 412 and bottom elevation of 407 with 3:1 side slopes was determined to be sufficient to contain the 100-year storm, and would not cause overtopping of the swale in the Church area. The proposed pond outlet connected to flow control structure to the existing manhole along NE 10f Place (Node 4)via an 18-inch pipe. The 1 remainder of the existing storm system would be unchanged. Pond design Alternative 1 is schematically shown in Figure 2,and is similar to the proposed design alternative as described in the preliminary analysis provided by the City (internal memorandum from Dan Carey to Ron Straka,November 28,2000). S ENS EA3100928237DOC/041660003 3 Results Summary The results of the analysis of Design Alternative 1 are shown in Table 2.The table indicates that the flooding frequency is reduced for the 2-year,24-hour event,but flooding will still occur at the 10-year and higher rainfall events. The amount of flooding,however,is significantly reduced,as shown by the reductions of estimated duration of flooding at Node I3. Also,flooding at Node 2 was eliminated due to the detention pond. The detention pond reduces flows reaching Honey Creek during events less than or equal to the 2-year rainfall event. However, the pond has little effect on reducing peak flowrates to Honey Creek during the 10-,25-,and 100-year,24-hour rainfall events,and in fact,the model shows a slight increase in the peak flowrates for these events compared with existing conditions. The increase is very slight,and appears to be the result of improved hydraulics in the system due to the detention pond and less surcharged conditions in the downstream system. TABLE 2 Design Alternative 1 —Detention Pond XP-SWMM Model Results Rainfall Event Flood Est.Duration of Flood Volume at Peak Flow to Maximum Locations Flooding at Node 3 Node 8(ft3) Honey Creek Pond (hrs) (cfs) Elevation (ft) July 3,2000 None - 0 11.9 407.6 2-Yr,24-Hour None - 0 14.4 408.5 10-Yr,24-Hour N3, N8 0.5 5,400 18.2 409.8 25-Yr,24-Hour N3, N8 1.3 13,000 19.2 410.7 100-Yr,24-Hour N3, N8 2 24,000 20.1 411.7 Design Alternative 2 — Detention Pond with Conveyance System Improvements 9 Y Y P Description of Alternative This conveyance design alternative includes the pond design as described under Alternative 1,and re-routing and upsizing the conveyance system from Node 3 to Node 5. The conveyance design includes upsizing the storm system to a 24-inch pipe from Node 3 to Node 2A (at the intersection of Anacortes Avenue and NE 10th Street),and a 30-inch pipe from Node 2A to Node 5,along Anacortes Avenue and then along NE 10th Place. Due to the existing grades and minimum pipe cover considerations, the 24-inch storm drains would only be able to be constructed with the minimum slope of 0.2%. The existing stormdrain system downstream from Node 5 would remain,and the existing 12-inch pipe from Node 3 to Node 4 would also remain. The outlet from the pond would connect to a new manhole at the intersection of NE 10th Street and Anacortes Avenue (Node 2A)via an 18-inch pipe. The XP-SWMM model schematic for Alternative 2 is shown in Figure 3. SENSEA3100928237.DOCl041660003 4 Results Summary The results of the model runs for Alternative 2 are shown in Table 4. TABLE 3 Design Alternative 2-Pond with Upsized Conveyance System XP-SWMM Model Results rRainfall Event Flood Locations Est. Duration Flood Peak Flow to Maximum Pond of Flooding at Volume at Honey Creek Elevation (ft) Node 3(hrs) Node 8(ft3) (cfs) July 3,2000 None - 0 11.8 407.6 2-Yr,24-Hour None - 0 14.3 408.6 10-Yr, 24-Hour N8 4,500 18 409.9 25-Yr,24-Hour N8 - 13,600 19.1 410.7 100-Yr,24-Hour N3, N8 0.5 27,600 20.1 411.9 Table 4 shows that this alternative further reduces the frequency and durations of flooding at Node 3. Node 3 only floods during the 100-year,24-hour rainfall event. The increase in pipe size along with the detention pond allows the hydraulic grade lines to be reduced ' along the shallow areas around Node 2A and 3(NE 10th Street). The model indicates that Node 8 still floods during storm events equal to or greater than the 10-year event,however the volume of water leaving the system at this node is slightly less than existing conditions and Alternative 1,with the exception of the 100-year storm. This shows that the pond is contributing to a reduction in flowrates. The upsized conveyance system helps to further reduce peak flow rates to Honey Creek in comparison to Alternative 1,especially for the smaller more frequent storm events. During the larger storm events, there is relatively little difference in peak flow rates to Honey Creek relative to existing conditions. The model does indicate a slight increase during the 25-year and larger recurrence interval storm events,but only by approximately 0.2 to 0.4 cfs. Again, the reason the peak flowrates are slightly higher than under existing conditions is likely a result of the storm drain hydraulics improving if a pond is constructed. It is important to note that in order to convey the stormwater from Node 3 to Node 5 along the road right-of-way and connect to the existing invert elevation at Node 5,the pipe slopes will barely meet minimum requirements,and there would not be much room for possible adjustments due to other utility conflicts. SEA/SEA3100928237.DOC/041660003 5 Design Alternative 3- Detention Pond with Conveyance System Improvements Description of Alternative Conveyance design alternative 3 includes the pond design as described under Alternative 1, and re-routing and upsizing the conveyance system from Node 3 to Node 6. The conveyance design is similar to Alternative 2,however the new system would connect to the existing system further downstream at Node 6.The design includes upsizing the storm system to a 24-inch pipe from Node 3 to Node 2A(the intersection of Anacortes Ave.NE and NE 10th Street),and then constructing a 30-inch pipe along Anacortes Avenue NE and then along NE 11th Street. The new system would be similar to the design that was previously completed by CH2M HILL(Drainage Improvement Plan,NE 10th Street/Anacortes Avenue NE,Storm System Improvement Project,March 1996),however, the new system would connect into the existing system at Node 6. Connecting into the existing invert elevation at Node 6 would allow a constructing the new pipe system at a slope of approximately 0.25%. The existing stormdrain system downstream from Node 6 would remain(18-inch pipes),and the existing 12-inch pipe from Node 3 to Node 4 would also remain. The outlet from the pond would connect to a new manhole at the intersection of NE 10th Street and Anacortes Avenue (Node 2A)via an 18-inch pipe. The XP-SWMM model schematic for Alternative 3 is shown in Figure 4. Results Summary Table 4 shows that this alternative is successful in reducing the frequency of flooding at Node 3 for every storm event except for the 100-year,24-hour event.Similar to Alternative 2,Node 8 still floods during the 10-year and above design storm events,however the computed volume of water leaving the system at this node is reduced in comparison to the existing conditions for all storm events with the exception of the 100-year storm.The upsized pipe system is more efficient at moving stormwater away from Node 3 and thus reduced the flooding frequency and volumes. Design alternative 3 significantly helps to reduce peak flowrates to Honey Creek during the smaller storm events,(events less than or equal to the 2-year rainfall event). The analysis shows that during the 10-year and 25-year design events the flows reaching Honey Creek are approximately equal to existing conditions. Only during the 100-year storm event was there a slight increase in peak flowrates(20.5 cfs compared with 19.7 under existing conditions). . Under Alternative 3,the goals of the project can be met,with only a slight increase in flows to Honey Creek during the largest storm event,which would also have occurred under Alternative 1 where only the pond would be constructed. With a larger drop in elevation from the upstream invert at Node 3 to connect to the existing invert at Node 6,there is a potential for greater pipe slopes and more opportunities for possible grade adjustments due to other utility conflicts. SEAISEA3100928237.DOCI041660003 6 TABLE 4 Design Alternative 3 Pond with Upsized Conveyance System XP-SWMM Model Results Rainfall Event Flood Locations Est. Duration Flood Peak Flow to Maximum Pond of Flooding at Volume at Honey Creek Elevation (ft) Node 3(hrs) Node 8(ft3) (cfs) July 3,2000 None 0 11.9 407.6 2-Yr,24-Hour None - 0 14.3 408.6 10-Yr,24-Hour N8 4,680 18 409.9 25-Yr,24-Hour N8 - 14,600 19 410.7 100-Yr,24-Hour N3, N8 0.3 31,800 20.5 411.7 Design Alternative 4— Conveyance System Improvements with No Pond Description of Alternative This alternative is essentially identical to Alternative 3 with the exception that there would be no pond. Stormwater flows from subbasin areas 12 and 15 would flow into the upgraded conveyance system undetained. The design includes upsizing the storm system to a 24-inch pipe from Node 3 to Node 2A(the intersection of Anacortes Ave. and NE 10th Street),and then constructing a 30-inch pipe along Anacortes Avenue and then along NE 11th Street. The new system would be similar to the design that was previously completed by CH2M HILL(Drainage Improvement Plan,NE 10f Street/Anacortes Avenue NE,Storm System Improvement Project,March 1996),however, the new system would connect into the existing system at Node 6. The existing stormdrain system downstream from Node 6 would remain (18-inch pipes),and the existing 12-inch pipe from Node 3 to Node 4 would also remain. ' This alternative was analyzed to determine the benefit of constructing a detention pond along with an upsized conveyance system. Results Summary The results if this analysis are shown in Table 5. The analysis indicates that this design alternative is not as effective of reducing the frequency and duration of flooding at Node 3 as with Alternatives 2 and 3,and the peak flowrates to Honey Creek increase under each storm event as well. This design also significantly increases the flooding volumes at Node 8 as shown by the table,demonstrating that the construction of the detention pond has a substantial impact in reducing the level of flooding while also reducing peak flowrates in the storm system. SEAISEA3100928237.DOC/041660003 7 TABLE 5 Design Alternative 4-Upsized Conveyance System with No Pond XP-SWMM Model Results Rainfall Event Flood Locations Est. Duration Flood Peak Flow to Maximum Pond of Flooding at Volume at Honey Creek Elevation (ft) Node 3(hrs) Node 8(ft3) (cfs) July 3,2000 None 0 14.2 NA 2-Yr,24-Hour None - 0 16.1 NA 10-Yr,24-Hour N8 _ 15,800 19.1 NA 25-Yr,24-Hour N3,N8 1 41,600 20.4 NA 100-Yr,24-Hour N3, N8 1.5 75,000 21.2 NA Conclusions Construction of the pond on the Vuong property is feasible,and would provide a significant amount of flooding relief. The pond would be moderately effective at reducing flows to Honey Creek for the 10-year,24-hour recurrence interval storm events and smaller. In addition, the flow to Honey Creek from an event similar to our prototype, the July 03,2000 storm event,would be lower if the pond were constructed. The model analysis shows that the pond alone will not be sufficient to reduce flooding at the target 25-year design storm. Although the pond is able to reduce flows and flooding during the smaller storm events (2-year or less), the existing storm drain system from Node 3 downstream is not sufficient to convey the remaining storm flows from the drainage basin, and the pipes become surcharged. Node 3 is a low spot,and is where the hydraulic grade lines increase to elevations above the ground surface, and flooding occurs. Therefore,in order to lower the hydraulic grade lines, the outlet pipe from Node 3 will have to be upsized. Design Alternatives 2 and 3 were assessed in conjunction with the pond design, and these included upsizing the storm drain outlet from Node 3, and routing the flows along Anacortes Avenue and NE 10th Place and NE 11th Street. In order to meet the goals of the project,however,and reduce flooding up to the 25-year design storm event,the best option for reducing flooding into the NE 10th Street and Anacortes Ct. NE area of the City of Renton is to upsize a portion of the existing storm drain system and construct a detention pond as described under design Alternatives 2 and 3. These designs also help to further reduce peak flowrates to Honey Creek for the smaller, more frequent storm events. However,the model does indicate a slight increase in flowrates during the 100-year storm event compared with existing conditions. Table 6 shows a summary of the alternatives for the 100-year,25-year and 10-year recurrence interval storm events. ' SEA/SEA3100928237.DOC/041660003 8 1 TABLE 6 Summary of Design Alternatives for the 100-year,25-year,and 10-year Design Storm Events XP-SWMM Model Results Rainfall Event Design Flood Est. Duration Flood Volume Peak Flow to Alternative Locations of Flooding at at Node 8(ft3) Honey Creek Node 3 (hrs) (cfs) 100-Yr,24-Hour Existing N2,N3,N8 16.5 26,600 19.7 100-Yr,24-Hour Alt. 1 N3,N8 2 24,000 20.1 100-Yr,24-Hour Alt..2 N3,N8 0.5 27,600 20.1 100-Yr,24-Hour Alt.3 N3,N8 0.3 31,800 20.5 100-Yr,24-Hour Alt.4 N3,N8 1.5 75,000 21.2 25-Yr,24-Hour Existing N2,N3,N8 11 16,000 18.9 25-Yr, 24-Hour Alt. 1 N3,N8 1.3 13,000 19.2 25-Yr,24-Hour Alt..2 N8 0 13,600 19.1 25-Yr, 24-Hour Alt.3 N8 0 14,600 19 25-Yr,24-Hour Alt.4 N8 0 41,600 20.4 10-Yr, 24-Hour Existing N2,N3,N8 6.3 7,800 18.1 10-Yr,24-Hour Alt. 1 N3,N8 0.5 5,400 18.2 10-Yr,24-Hour Alt..2 N8 0 4,500 18 ' 10-Yr,24-Hour Alt.3 N8 0 4,680 18 10-Yr,24-Hour Alt.4 N8 0 15,800 19.1 ' Table 6 shows that Alternative 3 appears to be the most successful at meeting the objectives of the Project. To further demonstrate this point,a graph of water surface elevations calculated at Node 3 for the 100-year and 25-year storm events is shown in Figures 5 and 6, respectively. Existing conditions water surface elevations were plotted in comparison to Design Alternatives 1,3 and 4. (Alternative 2 was very similar to Alternative 3,but is less feasible to construct,therefore it was not shown on the graphs). These figures graphically depict how effective Alternative 3 is at reducing the volume of flooding at Node 2. SEA/SEA3100928237.DOC/041660003 9 Recommendations We recommend design of Alternative 3,which would include construction of a detention pond,and re-routing and upsizing the storm drain trunk line from Node 3 to Node 6 along Anacortes Avenue and NE 11th Street. If the CITY were amenable to upsizing the storm drain line from Node 3 to Node 6 along the existing route (with 24-and 30-inch diameter pipes,similar to Alternative 3),which would involve removing and replacing the existing 12 and 18-inch pipes along some private property right-of-ways,costs savings may be realized by the reduced length of pipe required. Also,there may be less obstructions with existing utilities. i i 1 1 1 i i 1 1 1 1 SEA/SEA3100928237.DOC/041660003 10 to 12 1 I N11 0 4 N10 0 f ,_J rag N3 ' 0 1 1N 0 L• f IN6 t NC Nt L N3 NI N 1 0 P2-04�._P L-v FIGURE 1 ' XP-SWMM Model Schematic-Existing Conditions SEA3100928237.DOC/041660003 11 hi 12 1 to 11 t 1 N1❑ 0 1 9 I N9 i IN3 1 `� 7 I raj 0 tar, New 18" Pipe ta` to POW 14A Contrr i Str Ppond tad 1 �aL.N. ,ta28 ta2 tJ 1 FIGURE 2 ' XP-SWMM Model Schematic—Pond with Conveyance System Design Alternative 1 SEA/SEA3100928237.DOC/041660003 12 tra 1 ' 1 I to 11 � tlor r � ra 1MJ 0 ray 1 NF. Ira 6 rar, New 30 Pipe New 18 Pipe Pore New 24" Pipe P4A CorftrolStiPpond hark rat NJ � �r��e ray FIGURE 3 XP-SWMM Model Schematic—Pond with Conveyance System Design Alternative 2 S ENS EA3100928237.DOCl041660003 13 ' to 12 0 1 1 I N11 0 4 G�kOk N1O 3 I hag 0 NS t INS 0 New 30" Pipe Iha 6' ha CO.,P4 0 New 18 Pipe NS Nt AA POW 04.P IL_0 New 24' Pipe Carrtnaltand N3 _ Cap . 04 _ ha 1 1� FIGURE 4 XP-SWMM Model Schematic—Pond with Conveyance System Design Alternative 3 S ENS EA3100928237.DOC/041 660003 14 100 year Storm Event Water surface elevations at Node 3 412 411 410 — — - - -- - - - - - - - - - - - - - - - - 409 c I R 408 _ m w 407 - - - 406 405 - 404 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time Existing Conditions Pond Design — — Manhole elevation (409.9) —Pond Design Alt 3 Conveyance -Alt4 (No Pond) FIGURE 5 Water surface elevations at node 3 for the 100-year storm event S EA3100928237.DOC/041660003 15 25 year Storm Event Water surface elevations at Node 3' 412 i i 411 410 -- 409 c 0 408 m w 407 — ----- 406 405 --- — 404 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time Existing Conditions Pond Design —Pond Design Alt 3 9 Conveyance -Alt4 (No Pond) — — Manhole elevation (409.9) FIGURE 6 Water surface elevations at node 3 for the 25-year storm event SEA/SEA3100928237.DOC/041660003 16 APPENDIX B 1 XPSWMM Hydrologic and Hydraulic Modeling � Data - Input Data and Results 1 1 1 Table 1 XP-SWMM Hydrologic Input Parameters-Existing and Final Design Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project Percent Input Node ID' Sub-basin # CN2 Tc3 (min) Width (ft) Subcatchent Area (ac) Total Area (ac) Impervious Slope N 1 12 84.2 41.2 500 10.22 0 0.01 N 1 12 98 5.0 500 2.56 12.78 100 0.01 SW Up 15 86.6 36.1 500 3.57 0 0.01 SW_Up 15 98 5.0 500 1.39 4.96 100 0.01 N3 13 86 16.9 500 5.05 0 0.01 N3 13 98 5.0 500 3.10 8.15 100 0.01 N3 14 86 17.1 500 0.63 0 0.01 N3 14 98 5.0 500 0.53 1.16 100 0.01 N4 10 86 25.9 500 4.80 0 0.01 N4 10 98 5.0 500 1.69 6.48 100 0.01 N5 8 86 24.1 500 2.95 0 0.01 N5 8 98 5.0 500 1.04 3.98 100 0.01 N5 9 86 19.4 500 1.08 0 0.01 N5 9 98 5.0 500 0.38 1.46 100 0.01 N6 6 86 21.1 500 4.54 0 0.01 N6 6 98 5.0 500 1.59 6.13 100 0.01 N6 7 86 24.9 500 2.96 0 0.01 N6 7 98 5.0 500 1.04 4 100 0.01 N7 4 86.3 14.0 500 0.33 0 0.01 N7 4 98 5.0 500 1.86 2.191 100 0.01 N7 5 87 14.0 500 0.24 0 0.01 N7 5 98 5.0 500 2.14 2.38 100 0.01 N8 2 89 14.3 500 0.44 0 0.01 N8 2 98 5.0 500 3.92 4.36 100 0.01 N8 3 87 15.8 500 0.51 0 0.01 N8 3 98 5.0 500 2.03 2.54 100 0.01 N9 1 86 23.4 500 0.48 0 0.01 N9 1 98 5.0 500 1.91 2.39 100 0.01 N 10 0 81 67.8 500 0.30 0 0.01 N 10 0 98 5.0 500 0.08 0.38 100 0.01 Notes Input Node ID numbers are identical for existing and final design except Node 4 where the final design Input Node ID is designated 'N413" 2 Pervious Curve Number(CN) is a weighted average based on the various pervious land covers in each sub-basin 3 Time of concentration is defined for flow in the sub-basin to the collected node Table 2 XP-SWMM Hydraulic Input Parameters-Existing Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project NODE INFORMATION CONDUIT INFORMATION Upstream Downstream Exit Entrance Ground Invert Elev Length Diameter Upstream Node Invert Downstream Node Invert Conduit Loss Loss Node ID Elev(ft) (ft) Pipe ID (ft) Roughness (ft) �Slope(%J Node ID Elev. Node ID Elev. Type Coeff Coeff N1 437.82 426.11 P1 590 0.013 1 2.79 N1 426.11 N2 409.65 Circular 0.3 1 SW_Up 416.2 412.48 SWALE 250 0.025 3.5 0.524 SWUP 412.48 SW_Dn 411.17 Trapezoidal - - SW Dn 416 411.1 SW_CntrStr - - - - SW_Dn - N2 - N2 415.22 409.65 P2 - - - - N2 - N2A - - N2A' 413.22 407.86 Pipe 230 0.013 1 0.667 409.65 407.99 Circular 0.3 1 N3' 411.5 406.56 Road 100 0.014 1 2.22 414.22 - 412.22 Trapezoidal - - N4 412.23 404.4 P2A 230 0.013 1 0.667 N2A 407.86 N3 406.58 Circular 0.3 1 N5 413.58 403.45 P3 275 0.013 1 0.607 N3 406.56 N4 404.89 Circular 0.3 1 N6 411.92 401.62 P4 220 0.013 1.25 0.4 N4 404.4 N5 403.52 Circular 0.3 1 N7' 405.5 398.74 P5 410 0.013 1.5 0.395 N5 403.45 N6 401.83 Circular 0.3 1 N8 402 394.78 P6 285 0.013 1.5 0.947 N6 401.62 N7 398.92 Circular 0.3 1 N9 398 390.05 P7 128 0.013 1.25 3.094 N7 398.74 N8 394.78 Circular 0.3 1 N10 395.06 385.78 P8 - - - - N8 - N9 - - N11 394.85 385.08 Pipe 170 0.013 1.25 2.782 394.78 390.05 Circular 0.3 1 N12 395 388.08 Road 170 0.014 2 2.494 - 399.82 395.58 Trapezoidal - P9 60 0.013 1.5 1.3 N9 390.05 N10 389.27 Circular Siphon - - - - N10 - N11 - #1 30 0.013 1 0 - 386 386 Circular - #2 30 0.013 1 0 - 386 386 Circular - P11 97 0.013 1.5 1.155 N11 389.2 N12 388.08 Circular 0.3 1 Note: ' Storage nodes:ground elevations are set higher than actual to allow for ponding of surface water Table 3 XP-SWMM Hydraulic Input Parameters-Final Design Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project NODE INFORMATION CONDUIT INFORMATION Upstream Downstream Exit Entrance Ground Invert Elev Length Diameter Upstream Node Invert Downstream Node Invert Conduit Loss Loss Node ID Elev(ft) (ft) Pipe ID (ft) Roughness (ft) Slope(%) Node ID Elev. Node ID Elev. Type Coeff Coeff N1 437.82 426.11 P1 510 0.013 1 2.98 N1 426.11 N1A 410.9 Circular 0.3 1 WA 419.9 410.7 SWALE 250 0.025 3.5 0.524 SW-Up 412.48 SW_Dn 411.17 Trapezoidal - - SW-Up 416.2 412.48 SW_CntrStr - - - - SW_Dn - N2 - - - SW-Dn 416 411.1 WA-Pond 80 0.013 1 1.5 NIA 410.7 Pond 409.5 Circular 0.3 1 Pnd_Dn 413.5 406 N2 Pond 60 0.013 1 1.7 N2 408 Pond 407 Circular 0.3 1 Pond 413 406 Pnd CntrSt - - - - Pond - Pnd_Dn - - - - N2 414.22 408 P2 295 0.013 1.5 0.237 Pnd_Dn 406 N2A 405.3 Circular - N2A 410.55 405.3 PN3-N2A 220 0.013 1.5 0.3 N3 406.26 N2A 405.6 Circular 0.3 1 N3' 410.38 406.26 P3 275 0.013 1 0.607 N3 406.56 N4 404.89 Circular 0.3 1 N4 412.23 404.4 P4 220 0.013 1.25 0.4 N4 404.4 N5 403.52 Circular 0.3 1 N4A 415.69 403.1 P5 410 0.013 1.5 0.395 N5 403.45 N6 401.83 Circular 0.3 1 N413' 409.44 404.45 PN2A-N4B 220 0.013 2.5 0.364 N2A 405.3 N413 404.5 Circular 0.3 1 N5 413.58 403.45 PN4B-N4A 460 0.013 2.5 0.287 N413 404.45 N4A 403.12 Circular 0.3 1 N6 411.92 401.5 PN4A-N6 500 0.013 2.5 0.28 N4A 403.1 N6 401.7 Circular 0.3 1 N7' 405.5 398.74 P6 285 0.013 2.5 0.905 1 N6 401.5 N7 398.92 Circular 0.3 1 N8 402 394.78 P7 128 0.013 1.25 3.094 N7 398.74 N8 394.78 Circular 0.3 1 N9 398 390.05 P8 - - - - N8 - N9 - - - N10 395.06 389.25 Pipe 170 0.013 1.25 2.782 - 394.78 - 390.05 Circular 0.3 1 N11 394.85 389.2 Road 170 0.014 2 2.494 - 399.82 - 395.58 Trapezoidal - - N12 395 388.08 P9 60 0.013 1.5 1.3 N9 390.05 N10 389.27 Circular 0.3 1 Siphon 29 0.013 2.5 0.172 N10 389.25 N11 389.2 P11 97 0.013 1.5 1.155 N11 389.2 N12 388.08 Circular 1 0.3 1 Note: ' Storage nodes:ground elevations are set higher than actual to allow for ponding of surface water Table 4 ' XP-SWMM Hydrologic Output: 2-, 10-,25-, 100-yr Storm Events, Final Design Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project Subcatchment Area/Node N1#1 N1#2 SW_Up#1 SW_Up#2 N3#1 N3#2 N3#3 N3#4 N413#1 N413#2 N5#1 N5#2 N5#3 N5#4 N6#1 N6#2 N6#3 N6#4 fSTORM EVENT: 2 YR Area (acres) 10.22 2.56 3.57 1.39 5.05 3.10 0.63 0.53 4.80 1.69 2.95 1.04 1.08 0.38 4.54 1.59 2.96 1.04 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 Total Rainfall (in) 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Max Intensity(in/hr) 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 Total Runoff Depth (in) 0.73 1.77 0.86 1.77 0.84 1.77 0.84 1.77 0.83 1.77 0.83 1.77 0.84 1.77 0.84 1.77 0.83 1.77 Peak Runoff Rate (cfs) 0.93 1.45 0.45 0.79 0.82 1.75 0.10 0.30 0.65 0.95 0.41 0.59 0.17 0.22 0.67 0.90 0.41 0.59 Unit Runoff(in/hr) 0.09 0.57 0.13 0.57 0.16 0.57 0.16 0.57 0.14 0.57 0.14 0.57 0.15 0.57 0.15 0.57 0.14 0.57 STORM EVENT: 10 YR Area (acres) 10.22 2.56 3.57 1.39 5.051 3.10 0.63 0.53 4.80 1.691 2.95 1.04 1.08 0.381 4.54 1.591 2.96 1.04 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.001 0.00 100.00 0.00 100.00 ' Total Rainfall (in) 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.901 2.90 2.90 2.90 2.90 Max Intensity(in/hr) 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.941 0.94 0.94 0.94 0.94 Total Runoff Depth (in)l 2.66 1.58 2.66 1.56 2.66 1.56 2.66 1.55 2.66 1.55 2.66 1.56 2.661 1.56 2.66 1.55 2.66 Peak Runoff Rate (cfs) 2.12 2.15 0.93 1.17 1.72 2.60 0.21 0.45 1.37 1.42 0.87 0.87 0.35 0.321 1.42 1.34 0.86 0.87 Unit Runoff(in/hr) 0.21 0.84 0.26 0.84 0.341 0.84 0.341 0.84 0.29 0.841 0.30 0.841 0.321 0.841 0.31 0.841 0.29 0.84 ' STORM EVENT: 25 YR Area (acres) 10.22 2.56 3.57 1.39 5.051 3.10 0.63 0.53 4.80 1.691 2.95 1.04 1.08 0.381 4.54 1.591 2.96 1.04 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00i 0.00 100.00 0.00 100.00 Total Rainfall (in) 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.401 3.40 3.40 3.40 3.40 ' Max Intensity(in/hr) 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.101 1.10 1.10 1.10 1.10 Total Runoff Depth (in) 1.82 3.16 2.01 3.16 1.99 3.16 1.99 3.16 1.98 3.16 1.98 3.16 1.99 3161 1.98 3.16 1.98 3.16 Peak Runoff Rate (cfs) 2.85 2.53 1.22 1.38 2.26 3.07 0.28 0.53 1.81 1.67 1.15 1.03 0.46 0.381 1.87 1.58 1.14 1.03 Unit Runoff(in/hr) 0.28 0.99 0.34 0.99 0.451 0.99 0.45 0.99 0.381 0.99 0.39 0.99 0.42 0.991 0.41 0.99 0.38 0.99 STORM EVENT: 100 YR Area(acres) 0.63 0.53 5.05 3.10 10.22 2.56 3.57 1.39 4.80 1.69 2.95 1.04 1.08 0.38' 4.54 1.59 2.96 1.04 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00i 0.00 100.00 0.00 100.00 Total Rainfall (in) 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.901 3.90 3.90 3.90 3.90 ' Max Intensity(in/hr) 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 Total Runoff Depth (in) 2.43 3.66 2.43 3.66 2.24 3.66 2.46 3.66 2.42 3.66 2.42 3.66 2.43 3.66 2.42 3.66 2.42 3.66 Peak Runoff Rate (cfs) 0.35 0.61 2.82 3.54 3.62 2.92 1.51 1.59 2.27 1.92 1.44 1.18 0.57 0.431 2.34 1.82 1.42 1.19 ' Unit Runoff(in/hr) 0.56 1.14 0.56 1.14 0.351 1.14 0.42 1.14 0.47 1.14 0.49 1.14 0.53 1.141 0.51 1.14 0.48 1.14 Table 4 XP-SWMM Hydrologic Output: 2-, 10-,25-, 100-yr Storm Events, Final Design Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project Subcatchment Area/Node N7#1 N7#2 N7#3 N7#4 N8#1 N8#2 N8#3 N8#4 N9#1 N9#2 N10#1 N10#2 STORM EVENT: 2 YR Area (acres 0.33 1.86 0.24 2.14 0.44 3.92 0.51 2.03 0.48 1.91 0.30 0.08 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 Total Rainfall (in) 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Max Intensity(in/hr) 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 Total Runoff Depth (in) 0.86 1.77 0.90 1.77 1.02 1.77 0.90 1.77 0.83 1.77 0.57 1.77 Peak Runoff Rate (cfs) 0.06 1.05 0.05 1.21 0.10 2.22 0.09 1.15 0.07 1.08 0.01 0.04 Unit Runoff(in/hr) 0.18 0.57 0.19 0.57 0.23 0.57 0.18 0.57 0.14 0.57 0.05 0.57 ' STORM EVENT: 10 YR Area (acres) 0.331 1.86 0.24 2.14 0.44 3.921 0.51 2.03 0.48 1.91 0.30 0.08 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.001 0.00 100.00 0.00 100.00 0.00 100.00 Total Rainfall (in) 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 2.90 Max Intensity(in/hr) 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 Total Runoff Depth (in)l 1.58 2.66 1.64 2.66 1.79 2.66 1.63 2.66 1.55 2.66 1.18 2.66 Peak Runoff Rate (cfs)JJ 0.12 1.56 0.09 1.80 0.19 3.30 0.19 1.71 0.14 1.61 0.04 0.06 1 Unit Runoff(in/hr)l 0.37 0.84 0.39 0.84 0.43 0.84 0.37 0.84 0.30 0.84 0.12 0.84 STORM EVENT: 25 YR Area (acres) 0.33 1.86 0.24 2.14 0.44 3.921 0.51 2.03 0.48 1.91 0.301 0.08 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 Total Rainfall (in) 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 Max Intensity(in/hr) 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 Total Runoff Depth (in) 2.021 3.16 2.07 3.16 2.25 3.16 2.07 3.16 1.98 3.16 1.55 3.16 Peak Runoff Rate (cfs) 0.161 1.85 0.12 2.12 0.24 3.89 0.25 2.01 0.19 1.90 0.05 0.08 Unit Runoff(inlhr) 0.481 0.99 0.50 0.99 0.55 0.99 0.48 0.991 0.40 0.991 0.181 0.99 STORM EVENT: 100 YR Area(acres) 0.33 1.86 0.24 2.14 0.44 3.92 0.51 2.03 0.48 1.91 0.30 0.08 Percent Impervious 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 Total Rainfall (in) 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90 Max Intensity(in/hr) 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 1.26 Total Runoff Depth (in) 2.46 3.66 2.52 3.66 2.71 3.66 2.52 3.66 2.42 3.66 1.95 3.66 Peak Runoff Rate (cfs) 0.20 2.13 0.15 2.45 0.29 4.48 0.30 2.32 0.24 2.18 0.07 0.09 ' Unit Runoff(in/hr) 0.60 1.14 0.62 1.14 0.67 1.14 0.60 1.14 0.49 1.14 0.23 1.14 Table 5 XP-SWMM Hydraulic Output: 2-,10-,25-,100-yr Storm Events,Final Design Conditions ' NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project Conduit Maximum Maximum Ratio of Maximum Depth at Pipe ends ' Conduit Name/Storm Design Design Vertical Computed Computed Max.to Upstream Downstream Head Friction Critical Normal Upstream Downstream IE Up IE Dn Water Water Event Flow Velocity Depth Flow Velocity Design Loss Loss Depth Depth Node Node Surface Surface (cfs) (ft/s) (in) (cfs) (ft/s) Flow (ft) (ft) (ft) (ft) Up Dn Storm Event: 2yr Siphon 16.862 3.435 30.000 12.016 3.035 0.713 391.769 391.621 0.122 0.024 1.162 1.560 N10 N11 389.250 389.200 391.769 391.621 P1 6.153 7.834 12.000 2.195 6.999 0.357 426.536 411.319 1.000 14.209 0.633 0.412 N1 N1A 426.110 410.900 426.536 411.319 P2 5.117 2.896 18.000 0.111 1.165 0.022 406.169 405.781 0.026 0.664 0.122 0.150 Pnd_Dn N2A 406.000 405.300 406.169 405.781 ' PN3-N2A 5.753 3.256 18.000 1.978 2.829 0.344 406.964 406.130 0.192 0.592 0.530 0.606 N3 N2A 406.260 405.600 406.964 406.130 P4 4.086 3.329 15.000 0.859 2.093 0.210 404.789 404.094 0.069 0.431 0.363 0.389 N4 N5 404.400 403.520 404.789 404.094 P5 6.603 3.737 18.000 2.394 3.204 0.363 404.093 402.874 0.195 1.339 0.585 0.624 N5 N6 403.450 401.830 404.093 402.874 P6 39.026 7.950 30.000 7.601 5.170 0.195 402.874 402.779 0.106 0.342 0.912 0.744 N6 N7 401.500 398.920 402.874 402.779 ' P7 11.362 9.259 15.000 8.924 7.892 0.785 402.779 399.820 1.038 2.378 1.152 0.834 N7 N8 398.740 394.780 402.779 399.820 P9 12.011 6.797 18.000 12.040 6.772 1.002 393.453 391.768 0.925 0.773 1.315 1.233 N9 N10 390.050 389.270 393.453 391.768 P11 11.230 6.355 18.000 12.004 7.004 1.069 391.621 389.394 1.025 1.210 1.314 1.365 N11 N12 389.200 388.080 391.621 389.394 N2-Pond 4.613 5.873 12.000 0.559 3.582 0.121 409.013 409.007 0.281 0.749 0.310 0.235 N2 Pond 408.000 407.000 409.013 409.007 P3 2.776 3.535 12.000 0.861 2.992 0.310 406.964 405.272 0.187 1.490 0.388 0.382 N3 N4 406.560 404.890 406.964 405.272 -PN2A-N4B 24.734 5.039 30.000 2.005 2.443 0.081 405.781 405.152 0.102 0.437 0.459 0.480 N2A N413 405.300 404.500 405.781 405.152 PN4A-N6 21.704 4.422 30.000 4.003 3.101 0.184 403.839 402.874 0.180 1.112 0.656 0.726 N4A N6 403.100 401.700 403.839 402.874 PN4B-N4A 22.055 4.493 30.000 3.559 3.113 0.161 405.152 403.839 0.192 1.125 0.618 0.678 N4B N4A 404.450 403.120 405.152 403.839 Swale 199.400 6.330 42.000 0.817 0.538 0.004 413.584 413.584 0.000 0.002 0.159 0.225 SW-Up SW-Dn 412.480 411.170 413.584 413.584 NIA-Pond 4.375 5.571 12.000 2.180 4.773 0.498 411.319 409.999 0.518 0.805 0.631 0.499 N1A Pond 410.700 409.500 411.319 409.999 P8 10.762 8.770 15.000 11.023 8.845 1.024 399.821 393.453 1.584 4.811 1.250 1.055 N8 N9 394.780 390.050 399.821 393.453 ' roadP8 2086.200 3.180 24.000 0.003 0.158 0.000 399.821 395.580 . 0.000 5.692 0.000 0.000 N8 N9 399.820 395.580 399.821 395.580 ORF# 1 0.022 0.498 1.500 0.111 8.365 5.143 409,007 406,169 0.000 2.827 2.999 0.125 Pond Pnd_Dn 406,000 405,990 409,007 406,169 ORF# 2 0.250 0.498 3.999 0.000 0.000 0.000 406.169 406.169 0.000 0.000 0.000 0.000 Pond Pnd_Dn 410.500 410.490 406.169 406.169 ORF# 3 0.043 0.482 1.999 0.168 7.329 3.911 413.584 411.257 0.000 2.317 2.483 0.167 SW-Dn N2 411.100 411.090 413.584 411.257 ' ORF# 4 0.066 0.482 2.374 0.165 5.259 2.507 413.584 412.388 0.000 1.193 2.483 0.198 SW-Dn N2 412.200 412.190 413.584 412.388 ' Storm Event: 10yr Siphon 16.862 3.4351 30 16.5462 3.3454 0.9813 392.9879 392.7544 0.224 0.047 1.373 2.007 N10 N11 389.25 389.2 392.9879 392.7544 P1 6.153 7.834 12 3.9643 7.3638 0.6443 426.6943 411.8796 0.778 9.355 0.844 0.584 N1 N1A 426.11 410.9 426.6943 411.8796 P2 5.117 2.8956 18 0.3781 1.6747 0.0739 406.309 405.9003 0.067 0.682 0.226 0.274 Pnd_Dn N2A 406 405.3 406.309 405.9003 ' PN3-N2A 5.753 32558 18 3.0794 3.1811 0.5352 407.1822 406.2673 0.246 0.603 0.667 0.781 N3 N2A 406.26 405.6 407.1822 406.2673 P4 4.086 3.3292 15 1.7051 2.4699 0.4173 406.2393 406.0413 0.039 0.152 0.518 0.563 N4 N5 404.4 403.52 406.2393 406.0413 P5 6.603 3.7365 18 3.9201 3.2974 0.5937 406.0384 405.5345 0.097 0.561 0.756 0.831 N5 N6 403.45 401.83 406.0384 405.5345 P6 39.026 7.9503 30 11.9783 5.269 0.3069 405.5345 405.2664 0.118 0.239 1.159 0.949 N6 N7 401.5 398.92 405.5345 405.2664 P7 11.362 9.2587 15 11.3045 8.9994 0.9949 405.2664 399.8927 1.64 3.741 6.526 1.02 N7 N8 398.74 394.78 405.2664 399.8927 P9 12.011 6.7969 18 16.4021 9.1594 1.3656 395.838 392.9914 1.702 1.416 1.428 1.5 N9 N10 390.05 389.27 395.838 392.9914 P11 11.23 6.3547 18 14.6344 8.3632 1.3032 392.7474 389.4756 1.438 1.76 1.393 1.5 N11 N12 389.2 388.08 392.7474 389.4756 N2-Pond 4.613 5.8732 12 2.0955 4.5961 0.4543 411.6364 411.0292 0.716 0.706 0.617 0.472 N2 Pond 408 407 411.6364 411.0292 P3 2.776 3.535 12 1.894 3.5016 0.6822 407.1822 406.2398 0.2 1.216 0.586 0.606 N3 N4 406.56 404.89 407.1822 406.2398 PN2A-N4B 24.734 5.0388 30 3.1267 2.7581 0.1264 405.9003 405.7093 0.13 0.431 0.578 0.6 N2A N4B 405.3 404.5 405.9003 405.7093 PN4A-N6 21.704 4.4215 30 5.5177 3.0864 0.2542 405.6113 405.5358 0.029 0.099 0.774 0.857 N4A N6 403.1 401.7 405.6113 405.5358 ' PN4B-N4A 22.055 4.4931 30 6.1526 3.42 0.279 405.7093 405.6113 0.209 0.941 0.82 0.902 N46 N4A 404.45 403.12 405.7093 405.6113 Swale 199.4 6.3302 42 1.8328 0.6143 0.0092 413.7816 413.7812 0 0.002 0.267 0.361 SW-Up SW-Dn 412.48 411.17 413.7816 413.7812 N1A-Pond 4.375 5.5707 12 3.9025 5.346 0.892 411.8796 411.0292 0.656 0.984 0.839 0.737 N1A Pond 410.7 409.5 411.8796 411.0292 P8 10.762 8.7697 15 11.1739 8.97 1.0383 399.8926 395.8379 1.629 4.945 5.041 1.075 N8 N9 394.78 390.05 399.8926 395.8379 ' roadP8 2086.2 23.1796 24 10.0916 4.1706 0.0048 399.8926 395.8379 0 0.876 0.102 0.063 N8 N9 399.82 395.58 399.8926 395.8379 ORF# 1 0.0216 0.4976 1.4999 0.1511 10.791 6.9999 411,0292 406.309 0 4.704 5.029 0.125 Pond Pnd_Dn 406 405.99 411.0292 406,309 ORF# 2 0.2504 0.4976 3.9985 0.2271 2.772 0.9068 411.0292 410.7578 0 0.274 0.268 0.333 Pond Pnd_Dn 410.5 410.49 411.0292 410.7578 ORF# 3 0.0428 0.4815 1.9992 0.175 10.7026 4.0849 413.7812 411.6372 0 2.508 2.676 0.167 SW-Dn N2 411.1 411.09 413.7812 411.6372 ' ORF# 4 0.0659 0.4815 2.3744 0.1788 5.6752 2.7145 413.7812 412.3879 0 1.389 2.68 0.198 SW-Dn N2 412.2 412.19 413.7812 412.3879 Table 5 XP-SWMM Hydraulic Output: 2-,10-,25-,100-yr Storm Events,Final Design Conditions NE 10th Street/Anacortes Avenue NE Detention Pond and Stormwater Improvement Project Conduit Maximum Maximum Ratio of Maximum Depth at Pipe ends Conduit Name/Storm Design Design Vertical Computed Computed Max.to Upstream Downstream Head Friction Critical Normal Upstream Downstream IE Up IE Dn Water Water Event Flow Velocity Depth Flow Velocity Design Loss Loss Depth Depth Node Node Surface Surface (cfs) (ft/s) (in) (cfs) (ft/s) Flow (ft) (ft) (ft) (ft) Up Dn Storm Event: 25yr Siphon 16.862 3.435 30.000 17.300 3.500 1.026 393.145 392.873 0.246 0.052 1.407 2.115 N10 N11 389.250 389.200 393.145 392.873 P1 6.153 7.834 12.000 5.037 7.709 0.819 426.773 412.746 1.037 13.054 0.918 0.688 N1 N1A 426.110 410.900 426.773 412.746 P2 5.117 2.896 18.000 1.242 2.313 0.243 406.558 406.387 0.113 0.623 0.417 0.503 Pnd_Dn N2A 406.000 405.300 406.558 406.387 ' PN3-N2A 5.753 3.256 18.000 4.188 3.461 0.728 407.396 406.387 0.295 0.636 0.784 0.950 N3 N2A 406.260 405.600 407.396 406.387 P4 4.086 3.329 15.000 1.718 2.434 0.421 406.866 406.723 0.039 0.154 0.520 0.565 N4 N5 404.400 403.520 406.866 406.723 P5 6.603 3.737 18.000 4.588 3.273 0.695 406.723 406.045 0.134 0.770 0.822 0.921 N5 N6 403.450 401.830 406.723 406.045 P6 39.026 7.950 30.000 15.491 5.324 0.397 406,045 405.500 0.198 0.400 1.327 1.095 N6 N7 401.500 398.920 406.045 405.500 ' P7 11.362 9.259 15.000 11.551 9.189 1.017 405.500 399.910 1.711 3.901 6.760 1.045 N7 N8 398.740 394.780 405.500 399.910 P9 12.011 6.797 18.000 17.123 9.554 1.426 396.191 393.141 1.848 1.538 1.452 1.500 N9 N10 390.050 389.270 396.191 393.141 P11 11.230 6.355 18.000 14.826 8.464 1.320 392.867 389.481 1.472 1.806 1.397 1.500 N11 N12 389.200 388.080 392.867 389.481 N2-Pond 4.613 5.873 12.000 2.306 4.874 0.500 411.647 411.633 0.557 0.611 0.649 0.500 N2 Pond 408.000 407.000 411.647 411.633 ' P3 2.776 3.535 12.000 2.224 3.550 0.801 407.396 406.866 0.193 1.284 0.637 0.676 N3 N4 406.560 404.890 407.396 406.866 PN2A-N4B 24.734 5.039 30.000 3.842 2.807 0.155 406.387 406.341 0.084 0.229 0.641 0.663 N2A N413 405.300 404.500 406.387 406.341 PN4A-N6 21.704 4.422 30.000 6.537 3.084 0.301 406.203 406.045 0.035 0.124 0.845 0.940 N4A N6 403.100 401.700 406.203 406.045 PN4B-N4A 22.055 4.493 30.000 6.492 3.415 0.294 406.341 406.203 0.039 0.123 0.842 0.928 N46 N4A 404.450 403.120 406.341 406.203 Swale 199.400 6.330 42.000 2.354 0.619 0.012 413.846 413.845 0.000 0.002 0.310 0.421 SW-Up SW-Dn 412.480 411.170 413.846 413.845 N1A-Pond 4.375 5.571 12.000 5.021 6.485 1.148 412.746 411.633 0.867 1.466 0.917 1.000 N1A Pond 410.700 409.500 412.746 411.633 P8 10.762 8.770 15.000 11.171 8.968 1.038 399.910 396.191 1.630 4.946 5.039 1.076 N8 N9 394.780 390.050 399.910 396.191 ' roadP8 2086.200 23.180 24.000 8.490 3.116 0.004 399.910 396.191 0.000 0.226 0.118 0.078 N8 N9 399.820 395.580 399.910 396.191 ORF# 1 0.022 0.498 1.500 0.160 11.264 7.408 411,633 406,558 0.000 5.118 5.547 0.125 Pond Pnd_Dn 406.000 405.990 411.633 406.558 ORF# 2 0.250 0.498 3.999 0.401 4.570 1.600 411.633 410.817 0.000 0.815 0.327 0.333 Pond Pnd_Dn 410.500 410.490 411.633 410.817 ORF# 3 0.043 0.482 1.999 0.178 10.662 4.145 413.845 411.648 0.000 2.576 2.744 0.167 SW-Dn N2 411.100 411.090 413.845 411.648 ORF# 4 0.066 0.482 2.374 0.183 5.804 2.779 413.845 412.388 0.000 1.453 2.744 0.198 SW-Dn N2 412.200 412.190 413.845 412.388 ' Storm Event: 100yr Siphon 16.862 3.4351 30 18.0424 3.6559 1.07 393.2925 393.0476 0.265 0.056 1.437 2.279 N10 N11 389.25 389.2 393.2925 393.0476 P1 6.153 7.834 12 6.1084 7.6683 0.9928 429.6103 413.8461 1.189 14.568 0.957 0.814 N1 N1A 426.11 410.9 429.6103 413.8461 P2 5.117 2.8956 18 1.5857 2.4496 0.3099 407.103 407.0768 0.132 0.627 0.472 0.573 Pnd_Dn N2A 406 405.3 407.103 407.0768 ' PN3-N2A 5.753 3.2558 18 5.7533 3.7428 1 407.7406 407.0768 0.28 0.655 0.925 1.23 N3 N2A 406.26 405.6 407.7406 407.0768 P4 4.086 3.3292 15 1.6807 2.3116 0.4114 407.3858 407.2957 0.037 0.147 0.514 0.559 N4 N5 404.4 403.52 407.3858 407.2957 P5 6.603 3.7365 18 4.8424 3.2054 0.7334 407.2955 406.4294 0.148 0.854 0.846 0.955 N5 N6 403.45 401.83 407.2955 406.4294 P6 39.026 7.9503 30 19.3078 5.3336 0.4947 406,4294 405.5 0.307 0.621 1.49 1.242 N6 N7 401.5 398.92 406.4294 405.5 P7 11.362 9.2587 15 11.5502 9.1891 1.0165 405.5 399.9079 1.711 3.901 6.76 1.045 N7 N8 398.74 394.78 405.5 399.9079 P9 12.011 6.7969 18 17.8232 9.9367 1.4839 396.5412 393.2876 2.005 1.667 6.472 1.5 N9 N10 390.05 389.27 396.5412 393.2876 P11 11.23 6.3547 18 15.1442 8.6321 1.3486 393.042 389.4877 1.53 1.883 1.403 1.5 N11 N12 389.2 388.08 393.042 389.4877 N2-Pond 4.613 5.8732 12 2.7324 4.5093 0.5923 411.6942 411.6737 0.324 0.437 0.708 0.554 N2 Pond 408 407 411.6942 411.6737 P3 2.776 3.535 12 2.1331 3.5059 0.7683 407.7406 407.3862 0.182 1.246 0.624 0.657 N3 N4 406.56 404.89 407.7406 407.3862 PN2A-N4B 24.734 5.0388 30 5.2744 2.895 0.2132 407.0767 407.0166 0.027 0.042 0.755 0.782 N2A N413 405.3 404.5 407.0767 407.0166 PN4A-N6 21.704 4.4215 30 9.0396 3.108 0.4165 406.7324 406.4292 0.068 0.24 1.001 1.124 N4A N6 403.1 401.7 406.7324 406.4292 ' PN4B-N4A 22.055 4.4931 30 9.0147 3.3603 0.4087 407.0166 406.7331 0.067 0.219 1 1.113 N4B N4A 404.45 403.12 407.0166 406.7331 Swale 199.4 6.3302 42 2.8381 0.658 0.0142 413.9007 413.899 0 0.003 0.345 0.462 SW-Up SW-Dn 412.48 411.17 413.9007 413.899 NIA-Pond 4.375 5.5707 12 6.1074 7.7704 1.3959 413.8461 411.6737 1.234 2.158 0.957 1 N1A Pond 410.7 409.5 413.8461 411.6737 P8 10.762 8.7697 15 11.149 8.9499 1.036 399.9079 396.5411 1.624 4.926 5.039 1.072 N8 N9 394.78 390.05 399.9079 396.5411 ' roadP8 2086.2 23.1796 24 10.0421 3.9747 0.0048 399.9079 396.5411 0 0.082 0.133 0.085 N8 N9 399.82 395.58 399.9079 396.5411 ORF# 1 0.0216 0.4976 1.4999 0.16 11,2761 7.4128 411,6737 407.1026 0 5.135 5.531 0.125 Pond Pnd_Dn 406 405.99 411.6737 407.1026 ORF# 2 0.2504 0.4976 3.9985 0.4041 4.5943 1.6135 411.6737 410.8228 0 0.85 0.333 0.333 Pond Pnd_Dn 410.5 410.49 411.6737 410.8228 ORF# 3 0.0428 0.4815 1.9992 0.1796 9.8626 4.1925 413.899 411.6945 0 2.629 2.798 0.167 SW-Dn N2 411.1 411.09 413.899 411.6945 ' ORF# 4 0.0659 0.4815 2.3744 0.1866 5.9104 2.8328 413.899 412.3879 0 1.507 2.798 0.198 SW-Dn N2 412.2 412.19 413.899 412.3879 Notes: ' ORF#1 and#2 are the lower and upper orifices,respectively,for the MLK Church swale flow control structure. ORF#3 and#4 are the lower and upper orifices, respectively,for the detention pond flow control structure. Road P8 is the street above pipe P8,which is modeled as a trapezoidal channel. i i i i i i i i i