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DRAINAGE STUDY.pdfRECEIVED .4 NOV 19 2015 Seaview Elementary School DEE111PMENT SERVICES Mayfield Subsurface Drainage Improvements Api E!� 1411 j APPLICABLE CODE (I Playfield Drainage Study I June 2015 LUpdated _November 201_511 Drainage Impact Study w'n Olig rrqeqs'ry' xntlm'l ml"tc'd permitting, the rendisting illegal, nomonformiro ,, or yf w)errnitted building, strueftire or Site Mndulc« 'M'001 if; 0,11taide the HWPe of the, rrmit, appi io: ui,�rt. , r' �,ms of whether Buch 11ildirig" at« W�,,turda it -,'i! tion is shown on the site rh"%ii or w)Uflding,Btrudmreor 0 'i unchtwn +"Tr"'v 'k -,"j:et of a separatti MIN siA.Anq Engineers RO, i I It"A" FET) k)", y 5 17 A1,11t.) IMNAAG'��',, P ENGINEERING PlE Ww' Y' Seaview Elementary Playfield 'Drainage Study June 2015,(Uodated No em er 201 Prepared for: Edmonds School District #15 Nick Chou, Design and Construction Manager 2042068 th Avenue West Lynnwood, WA 98036 (425) 431-7161 Prepared by: Thaddeus J. Egging, PE, LEEP AP BD+C KPFF Consulting Engineers 1601 5th Avenue, Suite 1600 Seattle, WA 98101 (206) 622-5822 Seaview Elementary Playfield Drainage Study — Edmonds School District #15 I Seaview Elementary Playfield Drainage Study — Edmonds School District #15 1. Overview This study looks at the drainage impacts associated with the addition of an underdrain system to the Seaview Elementary School Playfield located at 8426 188th Street SW, Edmonds, WA 98026. The existing and proposed conditions were modeled using the Santa Barbara Urban Hydrograph method in StormShed2G. 2. Existing Conditions In the existing condition, stormwater runoff from the field sheet flows away from the grade break that runs north - south through the center of the field. The runoff then sheet flows into swales on the east and west sides of the field where it is collected in a series of catch basins and conveyed to the northwest corner of the field (see Figure 1: Existing Conditions in appendix A). For this study, the existing playfield was divided into two drainage basins (east and west) with a single point of compliance at the existing catch basin in the northwest corner of the field (see Figure 1). The times of concentration (Tc) for the existing basins were taken from the highpoint at the south end of the field following the flow lines down to the swales on the east and west sides of the field, into the nearest downstream catch basin, through the drain pipe system and ending at the catch basin in the northwest corner of the field. When run through StormShed, the model for the existing conditions produced a total peak flow of 0.733 cfs at 8.17 hours for the 25 -year event at the point of compliance catch basin (see Table 2-1). See StormShed calculations report in Appendix C. Table 2-1: Existing Conditions Results' 3. Proposed Conditions Proposed improvements to the playfield consist of an underdrain system to collect runoff from the field. For the proposed condition, the playfield was divided into three drainage basins (central, east, and west) with the same point of compliance as the existing condition at the catch basin in the northwest corner of the field (see Figure 2: Proposed Conditions in Appendix A). The first drainage basin is the central portion of the field that contributes to the proposed underdrain system. The other two basins are the east and west portions of the playfield that do not contribute to the underdrain system. The Tc for the east and west basins were taken from the highpoint at the Seaview Elementary Playfield Drainage Study — Edmonds School District #15 1 24-hour East Basin West Basin Total Weighted Event Precip. (in) Peak Q (cfs) Peak T (hrs) Peak Q (cfs) Peak T (hrs) Peak Q (cfs) Peak T (hrs) 2 -year 1.6 0.098 8.17 0.090 8.17 0.188 8.17 10 -year 2.5 0.272 8.17 0.251 8.17 0.522 8.17 25 -year 3.0 0.381 8.17 0.352 8.17 0.733 8.17 50 -year 3.2 0.426 8.17 0.394 8.17 0.820 8.17 100 -year 3.6 0.518 8.17 0.480 8.17 0.998 8.17 Table LjMdated November 2015 for H drolo is Soil Grout C 3. Proposed Conditions Proposed improvements to the playfield consist of an underdrain system to collect runoff from the field. For the proposed condition, the playfield was divided into three drainage basins (central, east, and west) with the same point of compliance as the existing condition at the catch basin in the northwest corner of the field (see Figure 2: Proposed Conditions in Appendix A). The first drainage basin is the central portion of the field that contributes to the proposed underdrain system. The other two basins are the east and west portions of the playfield that do not contribute to the underdrain system. The Tc for the east and west basins were taken from the highpoint at the Seaview Elementary Playfield Drainage Study — Edmonds School District #15 1 south end of each basin, similar to the existing condition. For the central basin, the To was taken along the flow line between the longitudinal underdrain pipes, and then downstream through the longest path of the underdrain system ending at the point of compliance. When run through StormShed, the model for the proposed conditions produced a total peak flow of . 0.927 cfs at 8.05 hours for the 25 -year event at the point of compliance catch basin (see Table 3-1). See StormShed calculations report in Appendix C. Table 3-1: Proposed Conditions Results' °Table u, dated November 2915 fr.)r iy cL,gjU bra 4. Model Inputs and Assumptions • Project Precipitation Values (in inches) taken from WSDOT 24-hour Isopluvial Map • Existing drain pipe slope of 2.0% • Proposed underdrain slope of 1.0% • Existing impervious pathway around field perimeter is excluded from model • See attached StormShed reports for specific basin model inputs • ul ori tydirlgglc Soul Grow 5. Downstream of the Point -of -Compliance From the point of compliance catch basin, stormwater flows through a 12 -inch pipe sloped at 2 -percent to an existing drainage feature located along the north edge of the school site. The drainage feature surface flows at 1 percent slope to a 12 -inch pipe sloped at 2 -percent that discharges to the City drainage system. The drainage feature consists of a trapezoidal Swale with a 2 -foot wide bottom, 1:5 side slopes, f#ow defath-witl444 of n d_a,total de th of 1'-4". The feature is broken into "North Portion" and "South Portion" (see Drainage Report for Seaview Elementary prepared by SVR, June 20 1996, in Appendix B). The play field is tributary to the "south portion". Additionally, a portion of the existing parking lot also discharges to the "south portion" drainage feature. Per the SVR Drainage Report (Appendix B) the drainage feature is designed to convey the 100 -year storm event. F1gwever,_1! g.. -fl Via„ " er kt ... VR...fg:olt is o"I w 4ich or 25 eroent of the s�walo tl ....As fl yi�gpg event i ni this c�e is the i ygan_gt rrl w w d ave 9 :jl�lt c, 1@( ty I sod �°� th Swale (lo il� t , r eit( taNIN or 12inches dee -1 Nuf� y�alg_wg ooit o 2 C�(�. �tss ;oµ f�gr°y i E 1 he ooh kart"g..loL o��arrtrw ��to a of and the d v lop d fief contrlb t m1 2w6wcfstper Table 1 ,fora total flow o 1.54 cfs rh outh-Portlm)" 4,eature has Seaview Elementary Playfield Drainage Study - Edmonds School District #15 2 24-hour Central Basin East Basin West Basin Total Weighted Event lPrecip.(in) Peak Q (cfs) Peak T (hrs) Peak Q (cfs) Peak T (hrs) Peak Q (cfs) Peak T (hrs) Peak Q (cfs) Peak T (hrs) 2 -year 1.6 0.174 8.00 0.041 8.17 0.031 8.17 0.246 8.05 10 -year 2.5 0.467 8.00 0.111 8.17 0.086 8.17 0.665 8.05 25 -year 3.0 1 0.650 1 8.00 0.156 8.17 0.121 8.17 0.927 8.05 50 -year 3.2 0.725 8.00 1 0.174 8.17 0.135 8.17 1.035 8.05 100 -year 1 3.6 0.880 8.00 1 0.212 8.17 0.165 8.17 1.256 8.05 °Table u, dated November 2915 fr.)r iy cL,gjU bra 4. Model Inputs and Assumptions • Project Precipitation Values (in inches) taken from WSDOT 24-hour Isopluvial Map • Existing drain pipe slope of 2.0% • Proposed underdrain slope of 1.0% • Existing impervious pathway around field perimeter is excluded from model • See attached StormShed reports for specific basin model inputs • ul ori tydirlgglc Soul Grow 5. Downstream of the Point -of -Compliance From the point of compliance catch basin, stormwater flows through a 12 -inch pipe sloped at 2 -percent to an existing drainage feature located along the north edge of the school site. The drainage feature surface flows at 1 percent slope to a 12 -inch pipe sloped at 2 -percent that discharges to the City drainage system. The drainage feature consists of a trapezoidal Swale with a 2 -foot wide bottom, 1:5 side slopes, f#ow defath-witl444 of n d_a,total de th of 1'-4". The feature is broken into "North Portion" and "South Portion" (see Drainage Report for Seaview Elementary prepared by SVR, June 20 1996, in Appendix B). The play field is tributary to the "south portion". Additionally, a portion of the existing parking lot also discharges to the "south portion" drainage feature. Per the SVR Drainage Report (Appendix B) the drainage feature is designed to convey the 100 -year storm event. F1gwever,_1! g.. -fl Via„ " er kt ... VR...fg:olt is o"I w 4ich or 25 eroent of the s�walo tl ....As fl yi�gpg event i ni this c�e is the i ygan_gt rrl w w d ave 9 :jl�lt c, 1@( ty I sod �°� th Swale (lo il� t , r eit( taNIN or 12inches dee -1 Nuf� y�alg_wg ooit o 2 C�(�. �tss ;oµ f�gr°y i E 1 he ooh kart"g..loL o��arrtrw ��to a of and the d v lop d fief contrlb t m1 2w6wcfstper Table 1 ,fora total flow o 1.54 cfs rh outh-Portlm)" 4,eature has Seaview Elementary Playfield Drainage Study - Edmonds School District #15 2 a.i-apacify.��f ��...�smw�fh 2«fe�sditd�ta the--pa�'k�,n._4i nod 1.�fsedi�iedtathe�.ay,f�e�d...s $00-year-flow frorn4he-pfGpossd favid i& 0 -.404.256-06,- Additionally, 12 -inch pipes sloped at 2 -percent slope have a 6.55 cfs capacity. Well in excess of anticipated flows at this site. A downstream analysis has been performed to verify increased flows from the site do not adversely impact City of Edmonds infrastructure. Refer to the Technical Memorandum in Appendix D for detailed information. At City of Edmonds direction, the point of compliance for the analysis is the existing catch basin in 88th Avenue West. The analysis showed that the increase in flows are minimal and will not adversely impact existing infrastructure. 6. Summary While the addition of the underdrain system does increase peak flow from the playfield the downstream infrastructure has adequate capacity for this flow. As such, no adverse impacts are expected with this project. Edmonds School District will continue to maintain the existing drainage features as well as clean the inlet out outlet pipes so as to maintain continued function. Seaview Elementary Playfield Drainage Study — Edmonds School District #15 3 Seaview Elementary Playfield Drainage Study — Edmonds School District #15 Appendix A Site Plans Seaview Elementary Playfield Drainage Study — Edmonds School District #15 Appendix A Seaview Elementary Playfield Drainage Study — Edmonds School District #15 Appendix A J J (WD NZ q }C] Q 2 q rnQ p0 Ip-;� Z Z m JCCZUO Q � w< xF- O 00 of cc0<5;;= C, Cr of ~�o U FUw FaIz Ol< o W=W=LL0 min w fnM WmOp�Om(w7 LLLL _ o r� a0 OOw _ d U O r x O N r 7[ O z} Z Z U p U W 0> Z rU Z� Wtll W QZ- w -W ZF- wUm O� W U rdr Uacna,jQZ O �nw4 ZLLU 2%Rwzow !- <aw g� zpo zd �� woavz¢ w --o qw w P. z ooari ¢wZz�Ux 5 a0, W-4 O Pin O ZZZ wwgQUga O Qpm Z� 05 Cq 4Q0 �? W CC c9` Z FO U ��°w a wSw Oz P: 15 I cc<U 3d w Z, 1% > Up �crnrx- ¢>F°'¢¢., Q Z8Z W4 >,: W QO 4 y WOO 65EEZZE F- px0 rw5 w ¢fin¢ ¢ F- m— c -U -"Dgz U o QOy UQr Z CC�w R Uro OZ Lu 'n 0zF4- a w}Z Oma O woo w O Wwz 0� )-M¢oQo Woo' a_'sZ = oro 3 ��p ww<wZZww xw QCL} Y m [L WWZ W J ¢aq ww[L (L m� OCC TW LL wwzwmw W lV fq o OU .- W N Z t7 d' *-'i > Vf U !- `2 Q w 0 W.... _. t6 LL' W QLJ wct7 Fw- O 0 cwaz4 w sn -¢FO wpCi O CC a X wZU+a Zt%Qtn QoIS [L WLL! dUZZ p= Fd2w W-ZF= F.R. Qm Z¢ opaU LL 't, m Q W Q w x mw d Q, W c7� x�W r-p zdp> w o Oz aOw¢ O?E x z w q W Op F m �qSi = r � is Z 0 Q J JJJ d OC]z J NCC JZNO a Q m N m O in O Q N F Z �O Wo<< UFF moo o a . >Mcn Cl) W $ Qto m w (� w 3 O z Q w m atS z z 6 a O o = U Q FILTER FABRIC SECURED TO 2' X 2' 14 GA, WIRE FABRIC EQUAL 2' X 2' WOOD OR � I o EQUIVALENT I 8'— 12' 1 41 8' PLACE 3/4'-1.5' WASHED GRAVEL IN THE TRENCH AND ON BOTH SIDES OF FILTER FABRIC FENCE ON THE SURFACE. 0 I oj Figure 3A: COE E1.1 Filter Fabric Fence Detail FILTER FABRIC MATERIAL IN C❑NTIN❑US ROLLS, USE STAPLES OR WIRE RINGS TO ATTACH FABRIC TO WIRE, IV II I WIRE MESH SUPPORT FEN�E I TO SUPPORT FILTER FAIMIC, II I� ffUW ,,I I 17W 1 BURY BOTTOM OF FILTER d N MATERIAL 8' TO 12' Via' MAX. I L1\, 2 X 2 WOOD POSTS OR EQUIVALENT ONTRACT❑R/DEVELOPER SHALL MAINTAIN AND REPLACE STRAW BALES TO INSURE PROPER EROSI❑N CONTROL, CITY INSPECTI❑N REQUIRED ON ALL EROSI❑N CONTROL METHODS BEFORE OTHER WORK CAN BEGIN, `IT » . 0 L) S,.,. -E, D M. 11 R Vo IONS STANDARD DETAIL MU 7/24/01 1 SCALE NTS I 0 No' E1.1 Figure 3B: COE E1.3 Inlet/Catch Basin Protection .GRATE •� CATCH BASIN CITY INSPECTI❑N REQUIRED ON ALL ER❑SI❑N CONTROL MEASURES BEFORE WORK CAN BEGIN, THIS APPLICATI❑N SHALL BE MAINTAINED AT ALL TIMES DURING C❑NSTRUCTI❑N PERI❑D. SEDIMENT SHALL BE REMOVED ON A REGULAR BASIS TO MAINTAIN FILTRATI❑N EFFECTIVENESS, REVISIONS STANDARD DETAIL ROVED r gar D. GEBERT 10/06/03 TEMPORARY SEDIMENT TRAP FOR CATCH BASINS D, GEBERT 05/19/05 D, GEBERT 05/05/06 uarE scams JDWG No. R. ENGLISH 11/01/13 7/24/01 NTS E1.3 14 A4 Figure 3B: COE E1.3 Inlet/Catch Basin Protection .GRATE •� CATCH BASIN CITY INSPECTI❑N REQUIRED ON ALL ER❑SI❑N CONTROL MEASURES BEFORE WORK CAN BEGIN, THIS APPLICATI❑N SHALL BE MAINTAINED AT ALL TIMES DURING C❑NSTRUCTI❑N PERI❑D. SEDIMENT SHALL BE REMOVED ON A REGULAR BASIS TO MAINTAIN FILTRATI❑N EFFECTIVENESS, REVISIONS STANDARD DETAIL ROVED r gar D. GEBERT 10/06/03 TEMPORARY SEDIMENT TRAP FOR CATCH BASINS D, GEBERT 05/19/05 D, GEBERT 05/05/06 uarE scams JDWG No. R. ENGLISH 11/01/13 7/24/01 NTS E1.3 lov, i 111 fa, j", im id ai � 111's 5 w 14 IS16 M MS ; is H1881 i g R, i TH- co co V �v LU ilv -M s I 1w V �v Appendix Drainage Report for Seaview Elementary SVR Design June 20, 1996 Seaview Elementary Playfield Drainage Study — Edmonds School District #15 Appendix B Seaview Elementary Playfield Drainage Study — Edmonds School District #15 Appendix B D E S I G N C 0 M P A N Y C 1 V i I E n g i n e e r i n g Drainage Report For Seaview Elementary Edmonds, Washington PERMIT SUBMITTAL June 20, 1996 Prepared for: Edmonds School District #15 Prepared by: SvR Design Company Address: 1008 Western Ave. #301 Seattle, WA 98104 Phone: (206) 223-0326 SvR #94015 P I a n n i n g L a n d s c i p e A i ( h i i e c c u r e S v R D E 5 1 G N C 0 PI P A N Y C I, u I L n 1; h in . r i o g M a n n a of 41 TABLE OF CONTENTS �,.. r,1 , . v la , ,A, i chi u c ¢ u� r . Page # I. Drainage Review 7 Overview .,. _....... .„w .......... 3 Existing Conditions .......................... . . , ............ 3 Proposed Conditions ... , ........ „ .. . ......... . ... . ..... . . . 3,4 Offsite Analysis .... , .... „ ........ . ...... „ .... , .. . , . , .... 4 Temporary Erosion/Sedimentation Control . ...... . ....... 4,5 II.. Figures Figure 1 - Vicinity Map ...... , . . .......... . ... . . . „ ...... . 7 Figure 2 - Topographical Map .... , . „ „ .......... . . ........ . . .. 8 Figure 3 - Soils Map ...... , ... ........... 9 Figure 4 - Existing Site Plan ........... , „ ..... „ . , .. „ .......... 10 Figure 5 - Proposed Site Plan ................. . . . „ .......... . 11 Figure 6 - Temporary Erosion/Sedimentation Control Plan , , , , , , , , , , ,,, , 12 Figure 7 - Impervious Vehicular Load Areas .... .. . ... . ..... « . , . „ .. 13 Figure 8 - Pervious/Impervious Areas ........ „ ........ „ ......... 14 III. Appendix June 20, 1996 i Seaview Elementary - Drainage Report. Page 2 of 43 1 a r[ ui i m„ L or d. c i c I i r 11 i..¢ o[ i . Drainage Review June 20, 1996 2 Seaview Elementary - Drains,, e;, Report. Page 3 �J3 V_ D E S I G N C O M P A N Y G:: r `r I fr. n„ rG c ,. u 1 111 1 a r[ ui i m„ L or d. c i c I i r 11 i..¢ o[ i . Drainage Review June 20, 1996 2 Seaview Elementary - Drains,, e;, Report. Page 3 �J3 S v R D E S I G NC O M P A N Y C i v i I E n g i n e e r i n g P I a n n n g L a n d s c a p e A c h i t e c t u r e Overview° Edmonds School District is proposing modifications to the existing Seaview Elementary school site. These modifications include building additions, parking and circulation changes, addition of landscape areas, court yard changes, rerouting of utilities, and adding an educational drainage feature. These improvements result in a net decrease in the amount of site impervious surface. Based on the City of Edmonds Storm Water Management Ordinance, the storm drainage erosion control, storm drainage detention, and water quality requirements do not apply to this site. See Figure 1 for Vicinity Map. The following drainage report discusses the existing site and storm drainage system, outlines the proposed site and storm drainage system, gives an offsite analysis, and discuses the proposed temporary sedimentation and erosion control. Storm drainage calculations are shown in the Appendix. Existing Conditions SITE The existing site consists of two buildings, a north parking lot, a east bus drop-off, a west and south play area, and a fire lane. The existing site is shown in Figure 4. DRAINAGE The existing bus drop-off sheet flows to the east into a series of catch basins located in a ditch at the east edge of the pavement. From here the storm water in is conveyed through lines running northwest across the north parking lot to the existing storm drainage system which runs east to west along 188th Street SW. The north parking lot sheet flows into catch basins that are part of the system that crosses the parking lot. A small offsite area to the east of the east property line also drains into this system. The existing west and south play areas sheet flow to the storm drainage system that runs east to west along the south side of the existing buildings. This system connects to the storm drainage system along 86th Pl. W. which connects to the storm drainage system along 188th Street SW. The existing site improvement area includes a total pervious area of 0.52 acre, a total impervious area of 3.69 acres. Proposed Conditions SITE Edmonds School district proposes an addition to the north and south of the existing buildings, adding a new gymnasium south, re -paving and modifying the north parking lot / east bus drop-off / fire lane / west and south play area /and court yard, addition of landscape areas, rerouting of utilities, and adding an educational drainage feature. The proposed site is shown in Figure 5. June 20, 1996 3 svmview Element �ary Drama qe Report, Pa c 43 S v R D E 5 1 G N C 0 M P A N Y C i v i I E n g i n e e r i n g P l a n n i n g L a n d s c a p e A i c h i t e c t u r e DRAINAGE Proposed site drainage will discharge to the existing locations. New catch basins and storm lines are proposed in some locations to accommodate the site improvements. The west play area, a portion of the south play area, and the west roof downspouts will drain to the educational drainage feature before discharging into the existing storm drainage system that runs east to west along the south side of the existing buildings. The proposed site improvement area includes a total pervious area of 0.88 acre and a total impervious area of 3.33 acres. The existing and proposed areas are summarized below. The City of Edmonds Storm Water Management Ordinance specifes that neither detention nor biofiltration are required for this site since there is less than 2,000 SF of new impervious area. Offsite Analysis Sources of background information for the off site analysis include the following: • A field visit was made on September 12, 1995. The downstream system was determined by field investigation and using City of Edmonds Storm Water System as -built drawings. UPSTREAM TRIBUTARY AREA A small area east of the north parking lot sheet flows to the lot (approx. 0.25 acre). A small area east of the bus drop-off sheet flows into the catch basins along the east edge of pavement (approx. 0.10 acre). An area to the east of the south play area flows to this area (approx. .5 acre). DOWN STREAM ANALYSIS June 20. 1996 4 seaviewle"IWIt" irange Rel'xowl I ago 5 of 4,3 Vehicular Non -Vehicular Total Impervious Pervious Area Impervious Impervious Area Area (acres) (acres) Area (acres) (acres) Existing 1.06 2.63 3.69 0.52 Proposed 1.00 2.33 3.33 0.88 New Impervious/ -0.06 -0.30 -0.36 0.36 New Pervious The City of Edmonds Storm Water Management Ordinance specifes that neither detention nor biofiltration are required for this site since there is less than 2,000 SF of new impervious area. Offsite Analysis Sources of background information for the off site analysis include the following: • A field visit was made on September 12, 1995. The downstream system was determined by field investigation and using City of Edmonds Storm Water System as -built drawings. UPSTREAM TRIBUTARY AREA A small area east of the north parking lot sheet flows to the lot (approx. 0.25 acre). A small area east of the bus drop-off sheet flows into the catch basins along the east edge of pavement (approx. 0.10 acre). An area to the east of the south play area flows to this area (approx. .5 acre). DOWN STREAM ANALYSIS June 20. 1996 4 seaviewle"IWIt" irange Rel'xowl I ago 5 of 4,3 From the site the existing storm drainage system drains to the west along 188th St. SW through a closed drainage system to 88th Ave W, and eventually flows into the Puget Sound, The 1/4 mile down stream investigations showed no major existing problems. A few of the catch basins need to be cleaned of debris. Temporary Erosion/Sedimentation Control A combination of Best Management Practices (BMPS) will be used to limit erosion and sediment runoff during construction. Preservation of natural vegetation, limiting area of construction impact, and efforts to limit the site construction to the dry season, will be used in combination with erosion and sediment control facilities. Temporary seeding will be used for erosion control in areas that would remain bare for more than 15 days. Areas exposed at any given time will be limited to the minimum as is practical. Permanent seeding will be established as rapidly as possible. BMPS include catch basin protection, silt fence and construction entrance, see Figure b for recommended layout. June 20, 1996 5 Seaview Elemenuuyage 6 n0af 49C'0 V D E 5 1 G N C 0 M P A N Y v I V'. i'r p; o n ¢s c; r ro (; A d'° A a ru n o �� w « L. �. iu d .. ,. p : A u[ In c i, q o ,•< From the site the existing storm drainage system drains to the west along 188th St. SW through a closed drainage system to 88th Ave W, and eventually flows into the Puget Sound, The 1/4 mile down stream investigations showed no major existing problems. A few of the catch basins need to be cleaned of debris. Temporary Erosion/Sedimentation Control A combination of Best Management Practices (BMPS) will be used to limit erosion and sediment runoff during construction. Preservation of natural vegetation, limiting area of construction impact, and efforts to limit the site construction to the dry season, will be used in combination with erosion and sediment control facilities. Temporary seeding will be used for erosion control in areas that would remain bare for more than 15 days. Areas exposed at any given time will be limited to the minimum as is practical. Permanent seeding will be established as rapidly as possible. BMPS include catch basin protection, silt fence and construction entrance, see Figure b for recommended layout. June 20, 1996 5 Seaview Elemenuuyage 6 n0af 49C'0 S v R D E S I G N C 0 M P A N Y C i v i I'.i. rr ro r: i., r' �n p; P V a n iri fi in g . Figures June 20, 1996 6 Seaview Elementary - Drainage Report. Page 7 of 43 June 20, 1996 (; v I [- g i m I= c r i n y, 1 11 o n n u I I K I v ii d s f, a p o A r , h e c l i i i FIGURE 1 - VICININY MAP LUX PAM iil 7 Seaview Elementary - Drainage Report, Page, 3 of 43 V R D E S I G N C 0 M P A N Y June 20, 1996 (; v I [- g i m I= c r i n y, 1 11 o n n u I I K I v ii d s f, a p o A r , h e c l i i i FIGURE 1 - VICININY MAP LUX PAM iil 7 Seaview Elementary - Drainage Report, Page, 3 of 43 A" v R D F S I G N C 0 M P A N Y FIGURE 2 - TOPOGRAPHICAL MAP June 20, 1996 8 Seaview Elemel.ghb- eport. S v R D E S I G N C 0 M P A N Y C 1 V V I ff n ?, i n, e r i n Y I I" I n '1 1! u (I G Q a iti d ( a p FIGURE 3 - SOILS MAP USDA Soil Survey for Snohomish County Area classifies the soils in the vicinity of the site as Alderwood- Urban land complex, with 2 to 8 percent slopes on the southeastern portion of the site and 8 to 15 percent slopes on the northwestern portion of the site. 71ZY June 20, 1996 9 Seaview Eleme�Df6noa 11 -Mg , fe4ffo"' IS 'v R D E S I G IN C 0 M P A N Y June 20, 1996 d P ( 3 1, e! A r c 4 f i'v c L u r" FIGURE 4 - EXISTING SITE PLAN to Seaview Eleineota pjai0nfg4&eport. a56 ire .410 Ban 16 i A lit pm=m h Nato Fuspulamp f . . . . . . . . . . . . . . T. to ........... S v R D E 5 1 G N C 0 M P A N Y v 4_ a ,, I n g it 1 M P, v II w n n I n f, L.. , of d �., i ', p e /'1 i r,;. Iv FIGURE 5 - PROPOSED SITE PLAN June 20, 1996 11 Seaview Elem9gw ?T�mjleporl, "'Zoo all, I Vill Q i 19, Cl) 'IT IL IL 00 BRA I I Ng I I I` I I — I — In! 5 MP, v l' k�o li a I all,a Rl Sd 8 § 8 hT, —TMG7 00 In! 5 MP, v l' k�o 00 S v R D E S I G N C O M P A N Y % �; rn r u Vu FIGURE 6 - TEMPORARY EII.OSION/SLI)Im[ENTATION COMMOL PLAN June 20, 1996 12 Seaview Elem fye TpJaiBfip SOPO` ID m 0 A W ..� .. D E S I G N C O M P A N Y :, I. �� V II G �r� it a Ni uw V M t� L a is d u, r �;� p wu^, v R A a �¢ In V i'�, � t FIGURE 7 - TMPDD VIOUS Vlr4,IHCUI,AR LOAD AREAS June 20, 1996 13 Seaview Elemp-11�,t�Ro4tReporl. S v, R, v D E S I G N C 0 M P A N Y I li ro y„ k ri ¢ w, u d m i„ . P, V a n d in p 11V. 'n or j r u I c A f, Q June 20, 1996 14 Seaview EIemP*- f 4.&evo t. S v R D E S I G N C 0 M P A N Y (,' d u 1 1: o K 1 n c i" r i n g 0 1 a n 1u o n g u d , a ", r c h i(v� i, au I III. APPENDIX June 20, 1996 15 Seaview Elenipt ye 2ja1fgg teport. Civil Engineering R S Planning ® Landscape Architecture v R D E S I G N C 0 M P A N Y C 6 v I I Eir''gineoring D E S I G IN C 0 m P Sheet of Job # F Project , 1' Planning L Peqigpeq by P1 A N Y Checked by Date e_' 4�' / .,/ I , .J 'u. Z"', Civil Engineering 10, S R '•Planning V R Landscape Architecture D E S I G N C 0 M P A N Y C i V E i n o, (,, r i n 8 D E S I G N (1 0 m P �P� Sheet Of Job # 2, - Project n Y L A N Y Checked by Date 1 1 -t7 11 La rc UL yq ha 777 C5 UL yq ha 777 1/17/96 11:32:22 am SvR Design Company page 1 ---------- BASIN SUMMARY BASIN ID: field100 NAME: field runoff, prop,100yr, 24hr SBUH METHODOLOGY TOTAL AREA.......: 4.59 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPElA PERV' IMP PRECIPITATION — — : 3.00 inches AREA..: 4.07 Acres 0.52 Acres TIME INTERVAL....: 10.00 min CN....:. 86.00 90.00 TC..... 62.77 min 62.77 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 150.00 ns:0.1500 p2yr: 1.50 s:0.3400 TcReach - Sheet L: 270.00 ns:0.1500 p2yr: 1.50 s:0.0200 TcReach - Sheet L: 198.00 ns:0.1500 p2yr: 1.50 s:0.0200 PEAK RATE: 0.92 cfs VOL: 0.65 Ac -ft TIME: 490 min S v H D E S I G IN t.w II Ellyllluul Illy Planning Landscape Architecture C 0 m P A N Y 'S A ko -Ar Y, 4�S 0 fp allt!"It --lryro - Job # Project Designed by Date Chocked by Date 1/17/96 1:51:14 pm SvR Design Company page 1 ---------- BASIN SUMMARY BASIN ID: cb13100p NAME: near cbl3, 100yr, 24hr SBUH METHODOLOGY TOTAL AREA.......: 0.25 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPElA PERV IMP PRECIPITATION....: 3.00 inches AREA,.: 0.10 Acres 0.15 Acres TIME INTERVAL....: 10.00 min CN..,.: 86.00 90.00 TC..... 5.00 min 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 18.00 ns:0.1500 p2yr: 1.50 s:0.1600 PEAK RATE: 0.11 cfs VOL: 0.04 Ac -ft TIME: 480 min BASIN ID: swwrf100 NAME: runoff sw of wbldg, prop,100yr SBUH METHODOLOGY TOTAL AREA.......: 0.15 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPElA PERV IMP PRECIPITATION....: 3.00 inches AREA..: 0.00 Acres 0.15 Acres TIME INTERVAL....: 10.00 min CN....: 86.00 90.00 TC..... 0.19 min 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 34.00 ns:0.0110 p2yr: 1.50 s:0.6000 PEAK RATE: 0.07 cfs VOL: 0.02 Ac -ft TIME: 480 min 0 co cli 0 cj 0 v 6/20/96 6:31:33 am SvR Design Company page 1 BASIN SUMMARY BASIN ID: nwwrf100 NAME: runoff nw of wbldg, prop,100yr SCS METHODOLOGY TOTAL AREA.......: 0.07 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPEIA PERV IMP PRECIPITATION....: 3.00 inches AREA..: 0.00 Acres 0.07 Acres TIME INTERVAL....: 10.00 min CN....: 86.00 90.00 TC..... 0.19 min 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 34.00 ns:0.0110 p2yr: 1.50 s:0.6000 PEAK RATE: 0.03 cfs VOL: 0.01 Ac -ft TIME: 500 min S v H D E S I G N • Liva trigineering • Planning LandscapeArchimmure C 0 m p A N Y -ineat at Jab # Project :?AV)�W EhfrY7 Designed by Datd—/�--7)• Checked by Date _ % Page 30 of 43 0 77= M, 1/17/96 2:37:50 pm SvR Design Company page 1 BASIN SUMMARY BASIN ID: crt100 NAME: courtyard, 100yr, 24hr SBUH METHODOLOGY TOTAL AREA.......; 0.74 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPEIA PERV IMP PRECIPITATION....; 3.00 inches AREA..: 0.11 Acres 0,63 Acres TIME INTERVAL....: 10.00 min CN....: 86.00 98.00 TC..... 5.00 min 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 47.00 ns:0.0110 p2yr: 1.50 s:0.2500 TcReach - Channel L: 230.00 kc:21.00 s:0.0200 PEAK RATE: 0.43 cfs VOL: 0.16 Ac -ft TIME: 480 min hKV Z) U�Wll uiyurom my Planning Landscape Architecture C 0 m P, A N Y -" ;?r' -out —1t.— Job # 7" Project Designed by Checked by Date V ti D E S I G N hKV Z) U�Wll uiyurom my Planning Landscape Architecture C 0 m P, A N Y -" ;?r' -out —1t.— Job # 7" Project Designed by Checked by Date 1/17/96 3:1:38 pm SvR Design Company page 1 ------------ BASIN SUMMARY BASIN ID: npkg100 SBUH METHODOLOGY TOTAL AREA.......: RAINFALL TYPE....: PRECIPITATION....: TIME INTERVAL....: NAME: n of n pkglot, 100yr, 24hr 0.20 Acres TYPEIA 3.00 inches 10.00 min BASEFLOWS: AREA..: CN.... TC.... 0.00 cfs PERV 0.02 Acres 86.00 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 30.00 ns:0.0110 p2yr: 1.50 s:0.0440 TcReach - Channel L: 40.00 kc:42.00 s:0.0170 TcReach - Sheet L: 80.00 ns:0.0110 p2yr: 1.50 s:0.0440 TcReach - Channel L: 70.00 kc:42.00 s:0.0440 impTcReach - Sheet L: 143.00 ns:0.0110 p2yr: 1.50 s:0.0440 PEAK RATE: 0.09 cfs VOL: 0.03 Ac -ft TIME: 480 min BASIN ID: spkg100 SBUH METHODOLOGY TOTAL AREA.......: RAINFALL TYPE....; PRECIPITATION....: TIME INTERVAL..... NAME: s of n pkglot, 100yr, 24hr 0.13 Acres TYPEIA 3.00 inches 10.00 min BASEFLOWS: AREA... CN.... TC.... 0.00 cfs PERV 0.00 Acres 86.00 5.00 min IMP 0.18 Acres 90.00 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 18.00 ns:0.1500 p2yr: 1.50 s:0.1600 impTcReach - Sheet L: 143.00 ns:0.0110 p2yr: 1.50 s:0.0440 PEAK RATE: 0.06 cfs VOL: 0.02 Ac -ft TIME: 480 min IMP 0.13 Acres 90.00 5.00 min Page 34 of 43 1/18/96 3:21:58 pm SvR Design Company page 1 BASIN SUMMARY BASIN ID: park100p NAME: n parking area, 100yr, 24hr SBUH METHODOLOGY TOTAL AREA.......: 1.40 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPEIA PERV PRECIPITATION....: 3.00 inches AREA — : 0.38 Acres TIME INTERVAL....: 10.00 min CN.... 86.00 TC...., 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 45.00 ns:0.1500 p2yr: 1.50 s:0.5000 TcReach - Sheet L: 155.00 ns:0.0110 p2yr: 1.50 s:0.0440 TcReach - Channel L: 193.00 kc:42.00 s:0.0100 PEAK RATE: 0.77 cfs VOL: 0.29 Ac -ft TIME: 480 min IMP 1.02 Acres 98.00 5.00 min 2 C3 . .... .. .. .. ... . .............. Ui W < it 0 to til 3: co ti c . ..... no .................... >_ Of V) fi ID Cl) ®r . ......... ... . ......... D_ F7 ter r' 15 P CL Z Ir o < ui CV 01 . L) o Y ill bo yr 4 Q ag .9 2 C3 . .... .. .. .. ... . .............. Ui W < cr to til 3: ti c . ..... no .................... >_ Of V) fi ®r . ......... ... . ......... F7 ter r' CL Z Ir o < ui CV 01 . L) o Y ill bo Q ag .9 61, 0cn T(o r..3 l b00 Li 0 < c) 3: 3NVI SIl S ON.� /_A0 r. Lid , -: ui I L e UJI L z L) Ui LLI Wo� Llj:� Cb LY LZ Avr_ < IV STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN Figure III -2.1 - Nomograph for Sizing Circular Drains Flowing Full 1000 900 800 .0001 700 2.0 600 .000,2 500 Minimum 0003 Allowable 400 ,00040001 Velocity 300 .0�� (Flowing 3.0 120 .0008 J5-.0002 Full ) 108 p .001 c x,0003 200 96 a 0004 90 c .002-4--.0005-4.0 84 0006 �'+x 78 p .003- 0008 72 w 66 w 005.001 5.0 CA. 60 .006 �- 90 `54 —100 O .008 x,002 o p 80 48 .01 � �i w 6.0 70 w , 003' W.42 vi 60U ,0 00'5 p w 7.0 LL: Z 36 006 w a. 50 - U Z 33 M 03' .008 a w 8.0 Z -30 a 27 . '�" r05 � � ... w 40 w 04 010 w w �, � Z 9.0 Q p 2 ' " ,,, 06 .08 020 >- 10.0 x 30 U Cr ,• .030 U 18 20 1 .040. w - w g 050 > 080 .. .100 9 SAMPLE USE 8 7 8 24" dia. CMP @ 2% slope yields --20.0 6 17cfs @ 5.2 FPS velocity (n = 0.024) 6 6 4 Values per Mannings Equation Q= (1.49 ) AR :h s 3 n 0 30.0 's This table can be converted ✓ to other "n" values by applying 2 formula: f'40.0 01 ni 02 � n2 1 1 III -2-8 FEBRUARY, 1992 Page 37 of 43 r u h 4 S 11 p wvn tngoneenng Planning bneer of V n Job — — Landscape Architecture �� I Project ZZLI1,11 Designed by CJs + Date_ °.. D E S I G N C 0 M P A N Y Checked by Date,. f) I"✓I..,m +,•„�,N' N.•°u' F" �.° "a a' ,md , ,.P ' II'r �na" �' �Ara+"d 9: (» t % r4-1� �.+...» mx" .�.r m� ..•�''�Y ��, � � '�"a. � e ary •,,,� � �'"7 t rn p�""u.Y�d°' .e'P°8� i.,y rt• 4mw.+x W �, x� 9w,x .gym °.r+ .» °.r'" ,d �. .M e r Page 38 f 43 Seaview Elementary - North side of Drainage Feature SvR #94015 Date: 06/20/96 Page Designed by JMG Checked by _ Q for the six month - 24 hour storm was determined using the hydrograph method and Water Works software. Q = 0.52 cfs Determine slope. S = 0.5% Assume vegetation will be a grass -legume mixture. Establish the height of vegetation during the winter and the design depth or flow (Design flow depth must be at least two inches less than winter grass height. Winter grass height = 6 in--_ Design flow depth (y) = 3.1 in �- a ; ", / Determine mannings n. n = 0.07 Select Swale shape. Use trapezoidal shape. Z = 5 :1 side slopes Calculate bottom width (b). b = Qn/(1.486y^1.667sA0.5) - Zy b = 2.02 ft Calculate the top width (t). t=b+2yZ ` t = 4.60 ft Calculate the cross sectional area (A), A = by + Zy^2 A= 0.85 sq ft S V l vq Engineering Sheet of m, mm,mm — — — •Planning Landscape Architecture Jeb # Project �YN ' ° •— 'r,.� Designed by !� Dale JZ ", „ 9 D E S I G N C O M P A N Y Checked by Date._ 22, asci 's3 +w a Alt #1 Play Fields (south " "1/2 of Asphalt Pkg Area" k E r^ Note says "1.4ft", should actually be y 1' 4" 1 Nr �Wd, 2. Swale is designed to convey the 100 -year stor event. Q(100) from parking lot is 0.23cfs; Q(100) from developed field is 1.26 cfs (per Table 3-1) for a total flow of 1.54 cfs. Swale capacity is 2.05 cfs (see appendix E) �� Seaview Elementary - South side of Drainage Feature SvR #94015 Date: 06/20/96 Page Designed by JMG Checked by _ Q for the six month - 24 hour storm was determined using the hydrograph method and Water Works software. Q = 1.19 cfs Determine slope. S = 1.0% Assume vegetation will be a grass-legume mixture. Establish the height of vegetation during the winter and the design depth or flow (Design flow depth must be at least two inches less than winter grass height. Winter grass height = 6 in Design flow depth (y) = 4 in Determine mannings n. n = 0.07 Select Swale shape. Use trapezoidal shape. Z = 5 :1 side slopes Calculate bottom width (b). b = Qn/(1.486y^1.667s^0.5) - Zy b = 1.83 ft Calculate the top width (t). t=b+2yZ t = 5.17 ft Calculate the cross sectional area (A). A = by + Zy^2 A = 1.17 sq ft 6/19/96 2:47:37 pm SvR Design Company page 1 BASIN SUMMARY BASIN ID: nplay10 NAME: north side of AC play area SCS METHODOLOGY TOTAL AREA.......: 0.66 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE....: TYPEIA PERV IMP PRECIPITATION....: 3.00 inches AREA..: 0.42 Acres 0.24 Acres TIME INTERVAL....: 10.00 min ICN....: 86.00 97.00 TC..... 5.00 min 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 18.00 ns:0.1500 p2yr: 1.50 s:0.1600 PEAK RATE: 0.31 cfs VOL: 0.11 Ac -ft TIME: 490 min BASIN ID: splay100 SCS METHODOLOGY TOTAL AREA.......: RAINFALL TYPE....: PRECIPITATION....: TIME INTERVAL....: NAME: south side of AC play area 0.59 Acres BASEFLOWS: 0.00 cfs TYPEIA PERV 3.00 inches AREA..: 0.36 Acres 10.00 min CN....: 86.00 TC..... 5.00 min ABSTRACTION COEFF: 0.20 TcReach - Sheet L: 18.00 ns:0.1500 p2yr: 1.50 s:0.1600 PEAK RATE: 0.28 cfs VOL: 0.10 Ac -ft TIME: 490 min IMP 0.23 Acres 97.00 5.00 min ❑ 111111D❑❑❑❑❑ ❑ mLUE=®1111m®1111 E® ®EUDHIMITUTIT1,1,11,1f®=11®®0® 11 Appended on: 08:11:38 Wednesday, November 11, 2015 Existing (East) Event Summary Event Peak Q (cfs) Peak T (firs),Ilyd Vol (acft) Area (ac) [Method,Raintype 2 year 0.0982 8.17 I 0.0616 1.3200 SBUH TYPEIA 10 year 0.2716 8.17 0.1368 1.3200 SBUH TYPEIA 25 year 0.3805 8.17 0.1829 1.3200 SBUH TYPE1A 50 year 0.4256 8.17 0.2019 11.3200 1 SBUH TYPEIA 100 year 0.5178 8.17 0.2406 1.3200 SBUH TYPEIA Record Id: Existing (East) IDesign Method SBUH Rainfall type TYPEIA jd Intv 1 10.00 min (Peaking Factor 484.00 Pervious Composited CN (AMC 2) Abstraction Coeff 0.20 IPervious Area (AMC 2) 1.32 ac DCIA 0.00 ac IPervious CN 86.00 IDC CN 0.00 Pervious ,r 23.52 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass) I 1.32 ac 86.00 Pervious Composited CN (AMC 2) 86.00 Pervious TC Calc Type Description Length Fslope [coeff Imisc I f T Short prairie grass and lawns.: 186.00 1.50% U500 2.00 22.84 �Sheet 10.15ft:in min Channel Other streams, man-made 461.00 100% 0M00 O�67 (cont) channels and pipe ft min 23.52 Pervious TC min Licensed to: KPFF Inc. Appended on: 08:26:34 Wednesday, November 11, 2015 Existing (West) Event Summary Event IPeak Q (cfs) IPeak T (hrs) jHyd Vol (acft) (Area (ac) IMethod Raintype 2 year 0.0895 ! 8.17 0.0602 11.2900 1 SBUH TYPElA 10 year 0.2506 8.17 0.1337 1.2900 SBUH TYPElA 25 year 0.3522 8.17 0.1787 1.2900 SBUH TYPElA 50 year 0.3943 8.17 0.1973 1.2900 SBUH ;TYPElA 100 year 0.4804 8.17 0.2351 1.2900 SBUH TYPEIA Record Id: Existing (West) Design Method SBUH IRainfall type TYPElA Hyd Intv 10.00 min IPeaking Factor 484.00 Abstraction Coeff 0.20 Pervious Area (AMC 2) 1.29 ac i CIA 0.00 ac (Pervious CN 86.00 IDC CN 0.00 Pervious TC 28.11 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Open spaces; lawns,parks (>75% grass) 1.29 ac 86.00 Pervious Composited CN (AMC 2) 86.00 Pervious TC Calc Type Description I Length Slope Coeff [ Misc TT Short prairie grass and lawns.: 238.00 2000 27.82 1Sheet 1.50% X0.1500 0.15 n mill Cl anne]Other strcanis, man-made 1.97.00 2.00% 0.29 .0.0100 (cont) channels and pipe 1t inir Pervious TC 28.11 min Licensed to: KPFF Inc. Appended on: 08:26:57 Wednesday, November 11, 2015 Proposed (Central) Event Summary Event Peak Q (cfs) Peak T (hers) flyd Vol (acft) Area (ac) Method 11aintype 2 year I 0.1736 8.00 1 0.0774 1.6600 SBUH TYPElA 10 year 0.4668 8.00 0.1720 1.6600 SBUH TYPElA 25 year I 0.6498 I 8.00 0.2300 1.6600 SBUH TYPElA 50 year 0.7253 8.00 0.2538 1.6600 SBUH TYPElA 100 year 0.8795 8.00 0.3025 1.6600 SBUH TYPElA Record Id: Proposed (Central) Design Method jHyd Intv (Pervious Area (AMC 2) Pervious CN (Pervious TC Type Sheet (Channel (cont) Channel (cont) SBUH Rainfall type 10.00 min IPeaking Factor Calc (Abstraction Coeff 1.66 ac IDCIA 86.00 IDC CN 4.85 min IDC TC Pervious CN Calc TYPElA 484.00 0.20 0.00 ac 0.00 0.00 min Description SubArea Sub cn Open spaces, lawns,parks (>75% grass) 1.66 ac 86.00 Pervious Composited CN (AMC 2) 86.00 Pervious TC Licensed to: KPFF Inc. TT 31.84 rain 0.86 rni.n 0,15 min 4.85 min Pervious TC Calc Description Length Slope Coeff Misc Short prairie grass and lawns.: 20,.00 ft 1.50% 0.1500 2.00 0.15 to IOther streams, man-made 417.00 1.00%0.0100 chajmels aiid pipe 11 Other streams, man-made 1.04.00 2,00%n 0.0100 channels and pipe fl Pervious TC Licensed to: KPFF Inc. TT 31.84 rain 0.86 rni.n 0,15 min 4.85 min Appended on: 08:27:16 Wednesday, November 11, 2015 Proposed (East) Event Summary Event Peak Q (cfs),Peak T (tars) 144yd Vol (acft) Area (ac) Method, �Raintype 2 year 0.0407 8.17 0.0242 0.5200 SBUH TYPEIA 10 year 0.1114 8.17 0.0539 10.5200 SBUH TYPElA 25 year 0.1557 8.17 0.0720 10.5200 1 SBUH TYPElA 50 year 0.1741 8.17 0.0795 0.5200 SBUH TYPEIA 100 year 0.2115 8.17 0.0948 0.5200 SBUH TYPElA Record Id: Proposed (East) (Design Method jHyd Intv IPervious Area (AMC 2) IPervious CN IPervious TC Type �Sheet Clutimel (cont SBUH IRainfall type 10.00 min (Peaking Factor (Abstraction Coeff 0.52 ac DCIA 86.00 DC CN 20.21 min 'DC TC Pervious CN Calc SubArea Sub en 0.52 ac 86.00 86.00 TYPE lA 484.00 0.20 0.00 ac 0.00 0.00 min Description Open spaces, lawns,parks (>75% grass) Pervious Composited CN (AMC 2) Pervious TC Calc Description Length[Slope[Coeff [c TT (0.15 Short prairie grass and lawns.: 153.00 1 00"_ 0 ' ] 19.54 .5 7o . 1500 1 17t I ' �2.06 Jn jmn Other streams, man-made 46:1.00 2,00% 0,0100 0.67 channels and pipe ft min Pervious TC 20.21 min Licensed to: KPFF Inc. Appended on: 08:13:30 Wednesday, November 11, 2015 Proposed (West) Event Summary f j Event Peak Q (els) Peak T (hrs) 'Hyd Vol (aeft) Area (ac) Method Raintype 2 year 0.0312 I 8.17 0.0196 0.4200 SBUH 'TYPE 1A 10 year 0.0864 I 8.17 0.0435 0.4200 [SBUH ITYPEIA 25 year 0.1211 8.17 I 0.0582 0.4200 SBUH TYPEIA 50 year 0.1354 8.17 0.0642 0.4200 SBUH 'TYPEIA 100 year 0.1647 8.17 0.0765 0.4200 SBUH TYPElA Record Id: Proposed (West) IDesign Method SBUH IRainfall type jHyd Intv 10.00 min IPeaking Factor IPervious Area (AMC 2) (Pervious CN (Pervious TC (Abstraction Coeff 0.42 ac JDCIA 86.00 IDC CN 1 23.52 min IDC TC Pervious CN Calc TYPE lA 484.00 0.20 0.00 ac 0.00 0.00 min Description SubArea Sub en Open spaces, lawns,parks (>75% grass) 0.42 ac 86.00 Pervious Composited CN (AMC 2) 86.00 Pervious TC Calc Type Description Length Fs -lope Fc-oeff Fm-isc I _TT Sheet Short prairie grass and lawns.: 190,00 �1.50% OJ500 2.00 23,24 0.15 ft in inin Cliaiiiiel Other streanis, man-made 897.00 2.010% 0.0100 019 (cont) Ieliannels and pipe ft 111111 Pervious TC 23.52 min Licensed to: KPFF Inc. Table 1: Existing Conditions Resultsl Ligkjga ted l c ens gr 2015 for F_Iyo Proposed Conditions SRI Precipitation Volume: Edmonds, WA 2 -yr, 24 -hr 1.60 in 10 -yr, 24 -hr 2.50 in 25 -yr, 24 -hr 3.00 in 100 -yr, 24 -hr 3.60 in The proposed improvements to the playfield include the addition of an underdrain system to collect runoff from the field. These improvements, as described in the Seaview Playfield Drainage Study, cause the peak flow from the playfield to increase by 04-3:70.194 cfs (from 0-4:760.733 cfs in the existing condition to Q-4-1-30,927 cfs, in the proposed condition) for the 25- year event.- The proposed improvements are limited to the playfield. Therefore, all of the other sub -basins remain the same as the existing conditions. When run through StormShed, the model for the proposed conditions produced a total peak flow of 2-4623.522 cfs for the 25 -year event (Table 2). This flow would have a normal depth of 0-690.78 feet, or less than WY2-inch deeper than the existing flow, in the 15 -inch CMP just upstream of the point of compliance structure CB 5-417. TWINAMIN-111IT11 Table 2: Proposed Conditions Results' - T ble jpd ted! orarnbt - 0 Qr 1091 LO—U , Sao Precipitation Volume: Edmonds, WA 2 -yr, 24 -hr 1.60 in 10 -yr, 24 -hr 2.50 in 25 -yr, 24 -hr 3.00 in 100 -yr, 24 -hr 3.60 in Model Inputs and Assumptions • Project Precipitation Values (in inches) taken from WSDOT 24-hour Isopluvial Map • Existing drain pipe slope of 2.00/6 A dote o 440/0 vtqs calculated for the e istio 15-ingLi i MC uusi method described ,herr Shuster in the review,�a comrn�l kt stl of 2% was used to be c nser at v ) • Proposed underdrain slope of 1.0% • Residential areas modeled as: "Residential districts —1 /3 acre" • Soils are Hydrologic Soil Group • See StormShed reports (Attachment 3) for specific basin model inputs Summary The addition of the underdrain system at the playfield increased the 25 -year peak flow approximately 5. 1.555 percent, from 2-.42-553.328 cfs to 2.2623.522 cfs. Proposed peak flow of 2.262152.2 cfs is much less than the 5.32 cfs capacity of the existing 15 -inch CMP upstream of the point of compliance structure (CS 5-417). Additionally, proposed flows will run at 0.73 feet In the 15 -inch CMP, or te-tn'ust over half full. As such, the City storm system has adequate capacity to handle the increased runoff resulting from the proposed playfield improvements. Attachment 2 Seaview Elem. Playfield Basin Analysis Friction Method Solve For lf:st0 Capacity of 15" CMP Manning Formula Full Flow Capacity Roughness Coefficient 0.024 ft/s Channel Slope 0.02000 ft/ft Normal Depth 1.25 ft Diameter 1.25 ft Discharge 4.95 ft3/s Discharge 4.95 ft/s Normal Depth 1.25 ft Flow Area 1.23 ft' Wetted Perimeter 3.93 ft Hydraulic Radius 0.31 ft Top Width 0.00 ft Critical Depth 0.90 ft Percent Full 100.0 % Critical Slope 0.02638 ft/ft Velocity 4.03 ft/s Velocity Head 0.25 ft Specific Energy 1.50 ft Froude Number 0.00 Maximum Discharge 5.32 ft"/scf Discharge Full 4.95 ft3/s Slope Full 0.02000 ft/ft Flow Type SubCritical `%�',` ,lni'%ut',, , Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Bentley Systems, Inc. Haestad Methods SolBdafld�P4wMaster V81 (SELECTseries 1) [08.11.01.03] 8/14/2015 10:48:26 AM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 2 Capacity of 15" CMP WPO W_ Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.25 ft Critical Depth 0.90 ft Channel Slope 0.02000 ft/ft Critical Slope 0.02638 ft/ft Bentley Systems, Inc. Haestad Methods SOIBdatl Master V81 (SELECTseries 1) [08.11.01.03] 8/14/201510:48:26 AM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 2 of 2 Appended on: 08:14:13 Wednesday, November 11, 2015 Basin A Event Summary _ ___--------- .., Attachment 3 Seaview Elem. Playfield Basin Analysis Event IPeak Q (cfs) IPeak T (hrs) jHyd Vol (acft) Area (ac) Method Raintype 2 year 0.0333 8.17 0.0294 0.9600 SBUH TYPEIA 10 year 0.1429 8.17 0.0754 1 0.9600 SBUH TYPElA 25 year 0.2185 8.00 0.1051 10.9600 SBUH TYPElA 100 year, 0.3201 8.00 0.1432 0.9600 SBUH TYPEIA Record Id: Basin A Design Method SBUH (Rainfall type TYPElA jHyd Intv 10.00 min IPeaking Factor 484.00 Pervious TC Calc Abstraction Coeff 0.20 Pervious Area (AMC 2) 0.96 ac IDCIA 0.00 ac Pervious CN 81.00 DC CN 0.00 Pervious TC 15.19 min DC TC 0.00 min Pervious CN Calc Sinooth Surfaces.: 0.011 Type Sheet Sheet Channel (interin) Description SubArea Sub cn Residential districts - 1/3 acre 0.96 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Description Length Slope Coeff Misc TT (Short prairie grass and 110.00 ft 5.00% 0.1500 [1.60 10.37 lawns.: 0.15 n ni in Sinooth Surfaces.: 0.011 95.00 ft 4.00%0.0110 1.60 1.25 min Concrete pipe (n=0.012) f1.00 [2.00,7t290 0.0120 3.58 min Pervious TC Licensed to: KPFF Inc. 15.19 min Appended on: 08:14:50 Wednesday, November 11, 2015 Basin B Event Summary Event IPeak Q (cfs) (Peak T (hrs) IHyd Vol (acft) (Area (ac) method Raintype 2 year 0.0291 9.17 0.0319 1.0400 SBUH TYPElA 10 vear 0.1091 8.50 0.0817 1.0400 SBUH TYPE 1 A =25year 0.1666 8.17 0.1138 1.0400 'SBUH TYPElA 100 year 0.2459 8.17 0.1551 1.0400 SBUH TYPElA Record Id: Basin B (Design Method SBUH (Rainfall type TYPElA jHyd Intv 10.00 min (Peaking Factor 484.00 Abstraction Coeff 0.20 Pervious Area (AMC 2) 1.04 ac JDCIA 0.00 ac Pervious CN 81.00 DC CN 0.00 (Pervious TC 42.32 min DC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1/3 acre 1.04 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Short prairie grass and 110.00 1 60 14.95 Sheet lawns.: 0.15 ft .00500 2 % 0.1 in min Short prairie grass and 330.00 0/.00 [5- 1.60 2496 Sheet (lawns.: 0.15 't; 0.1500 in rvr v n Channel Conca-cte pipe (n=0.012) 865.00 2.00%0.01211 140 min (interni) It Pervious TC 42.32 min Licensed to: KPFF Inc. Appended on: 08:17:41 Wednesday, November 11, 2015 FIELD Event Summary Event jPeak Q (cfs) jPeak T (hrs) jHyd Vol (acft) Area (ac) Method Raintype 2 year 0.1878 8.17 0.1212 2.6000 SBUH TYPE 1 A 10 e4'0.5222 8.17 0.2694 2.6000 SBUH TYPElA F2 5 year 0.7327 8.17 0.3602 2.6000 SBUH TYPElA 100 year 0.9980 8.17 0.4738 2.6000 SBUH TYPEIA Record Id: FIELD (Design Method SBUH lRainfall type TYPElA (Hyd Intv 10.00 min (Peaking Factor 484.00 Abstraction Coeff 0.20 (Pervious Area (AMC 2) 1 2.60 ac JDCIA 0.00 ac Pervious CN 86.00 JDC CN 0.00 Pervious TC 25.44 min [DC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass) I 2.60 ac 86.00 Pervious Composited CN (AMC 2) 86.00 Pervious TC Calc Type Description Length Slope Coeff [Misc TT Carmel Other streams, man-made 460.00 _F2_ 00% 0.0100 0.67 cant channels and pipe ft I min Sheet Short Prairie grass and lawns.: 179.00 1.50 % 0.1500 1.60 24.77 11.15 ft m min Pervious TC 25.44 min Licensed to: KPFF Inc. Appended on: 08:15:07 Wednesday, November 11, 2015 Basin C Event Summary Event IPeak Q (cfs) IPeak T (hrs) Hyd Vol (acft) Area (ac) IMethod Raintype 2 year 0.5431 8.00 0.1815 1.5800 SBUH TYPElA 10 year 0.8817 8.00 0.2989 1.5800 SBUH 1TYPEIA L25 year 1.0680 8.00 0.3645 1.5800 SBUH ITYPEIA 100 year 1.2905 8.00 0.4432 1.5800 SBUH 'TYPElA Record Id: Basin C (Design Method ISBUH (Rainfall type TYPElA (Hyd Intv 1 10.00 min (Peaking Factor I 484.00 Abstraction Coeff 0.20 Pervious Area (AMC 2) 1.58 ac JDCIA 0.00 ac Pervious CN 98.00 IDC CN 0.00 Pervious TC 6.20 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc) I 1.58 ac 98.00 Pervious Composited CN (AMC 2) 98.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT (Sheet Stnoot h Surfaces.: 0.011 1200.00 ft 2.00% 0.0110 1.60 in 2.98 min (Channel (interm) IGrassed (n=0.030) 175.00 ft 1.00% 0.0300 F 1.72 min Channel (interm) Concrete pipe (ii=0,01.2) 542.00 ft 2.00% 0.0120 F 1.50 min Pervious TC 6.20 min Licensed to: KPFF Inc. Appended on: 08:15:22 Wednesday, November 11, 2015 Basin D Event Summate Event IPeak Q (cfs) IPeak T (hrs) jHyd Vol (acft) Area (ac) Method Raintype 2 year 0.0080 8.00 0.0055 0.1800 SBUH ' TYPE 1 A 10 year 0.0337 8.00 0.0141 0.1800 SBUH TYPEIA 25 year 0.0509 8.00 0.0197 0.1800 SBUH i TYPE 1 A 100 year 0.1732 8.00 0.0269 0.1800 SBUH TYPEIA Record Id: Basin D (Design Method I SBUH (Rainfall type TYPElA (Hyd Intv I 10.00 min (Peaking Factor 484.00 lawns.: 0.15 (Abstraction Coeff 0.20 Pervious Area (AMC 2) 0.18 ac JDCIA 0.00 ac Pervious CN 1 81.00 IDC CN 0.00 (Pervious TC I 4.05 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1/3 acre 0.18 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Type Description I Length Slope Coeff Misc F TT Sheet Short prairie grass and F5O.00 ft 25.00% 0.1500 1.60 2.90 lawns.: 0.15 do nein Channel 415.00 1.15 Concrete pipe (n=0.012) ft [2.000/ [0.0120 min intern 4.05 Pervious TC min Licensed to: KPFF Inc. Appended on: 08:15:50 Wednesday, November 11, 2015 Basin E Event Summary Event IPeak Q (cfs)'Peak T (hrs)'Hyd Vol (acft) (Area (ac) Method'Raintype 2 year 0.0143 8.17 0.0126 0.4100 SBUH ;TYPE 1 A 10 year 0.0611 8.17 0.0322 0.4100 'SBUH TYPElA 25 year 0.0935 8.00 0.0449 0.4100 SBUH TYPElA 100 year ` 0.1370 8.00 0.0611 0.4100 SBUH TYPEIA Record Id: Basin E (Design Method SBUH IRainfall type TYPElA IHyd Intv 10.00 min IPeaking Factor 484.00 Abstraction Coeff 0.20 (Pervious Area (AMC 2) 0.41 ac IDCIA 0.00 ac (Pervious CN I 81.00 IDC CN 0.00 (Pervious TC 15.09 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1/3 acre 0.41 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Type I Description I Length Slope FCoeff FNfisc TT S deet (Short prairie grass and 180.00 6.00% �� 0.1500 1.60 14.29 lawns.: 0.15 ft in niia Channel Channel 290.00 (intermPervious (Concrete pipe (n=0.012) ft 2.00% 0.0120 0.80 min TC 15.09 min Licensed to: KPFF Inc. Appended on: 08:16:03 Wednesday, November 11, 2015 Basin F Event Summary Event IPeak Q (cfs) (Peak T (hrs) Hyd Vol (acft) jArea (ac) (Method Raintype 2 year 0.0096 8.17 0.0077 0.2500 SBUH TYPE I A 10 year 0.0412 8.00 0.0196 0.2500 SBUH TYPEIA 25 year 0.0633 8.00 0.0274 0.2500 SBUH TYPElA 100 year 0.0922 8.00 0.0373 0.2500 [SBUH �TYPElA Record Id: Basin F Design Method IHyd Intv Pervious Area (AMC 2) Pervious CN Pervious TC SBUH [Rainfall type 10.00 min IPeaking Factor Sheet (Abstraction Coeff 0.25 ac IDCIA 81.00 IDC CN 10.34 min IDC TC Pervious CN Calc Description SubArea Residential districts - 1/3 acre 0.25 ac Pervious Composited CN (AMC 2) Pervious TC Calc TYPE 1A 484.00 0.20 _ 0.00 ac 0.00 0.00 min Sub cn 81.00 81.00 Type Description I Length Slope Coeff rMisc TT Sheet Short pra irte grass and lawns.: (D 15 120.00 [7.000, 0.15001.60 ftin 9.71 min Channel Charm) Concrete pipe (n=0.012) 225.00 2 12.00% 0.0120 0.62 min (interPervious 10.34 TC min Licensed to: KPFF Inc. Appended on: 08:16:15 Wednesday, November 11, 2015 Basin G Event Summary Event IPeak Q (cfs) IPeak T (hrs) Hyd Vol (acft) Area (ac) Method Raintype 2 year 0.0265 8.50 0.0245 0.8000 SBUH TYPElA 10year 0.1147 8.17 0.0628 0.8000 I SBUH TYPEIA L-T5year�0.747 8.17 0.0876 0.8000 SBUH TYPElA 100 year 0.2530 8.17 0.1193 0.8000 SBUH TYPEIA Record Id: Basin G Design Method SBUH IRainfall type TYPElA Hyd Intv 10.00 min IPeaking Factor 484.00 Abstraction Coeff 0.20 Pervious Area (AMC 2) I 0.80 ac IDCIA 0.00 ac Pervious CN 81.00 IDC CN 0.00 Pervious TC 18.03 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1/3 acre 0.80 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Short prairie grass and 265 [7509,,, [in.0060 17.81 Sheet lawns.: 0.15 0.1500 ft ruin Channel (intern) Concrete pipe (n=0.012) 80.00 ft 2.00% 0.0120 0.22 min Pervious TC 18.03 min Licensed to: KPFF Inc. Appended on: 08:16:57 Wednesday, November 11, 2015 Basin H Event Summary Event IPeak Q (cfs) IPeak T (hrs) jHyd Vol (acft) Area (ac) Method FRaintype 2 year I 0.0959 I 10.17 1 0.1243 4.8700 SBUH TYPElA 10 year 0.4045 8.67 0.3398 4.8700 SBUH TYPElA 25 year 0.6410 8.50 0.4823 4.8700 SBUH TYPElA ;100 year 0.9604 8.50 0.6672 4.8700 SBUH TYPElA Record Id: Basin H Design Method IHyd Intv Pervious Area (AMC 2) Pervious CN Pervious TC Type (Sheet Cliari el, (i r� terr�n) SBUH Rainfall type TYPElA 10.00 min Factor 484.00 Abstraction Coeff 0.20 4.87 ac IDCIA 0.00 ac 79.00 IDC CN 0.00 46.85 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1 acre 4.87 ac 79.00 Pervious Composited CN (AMC 2) 79.00 Pervious TC Calc Description LengthSlope Coeff Misc TT Short prairie grass and 710.00 5.00% [0- .15001.60 46.08 lawns.: 0.15 ft �in arnin Concrete pipe (n=0.0 12) 280.00 2.00% 0.0120 � OM78 min Pervious TC 46.85 min Licensed to: KPFF Inc. Appended on: 08:17:09 Wednesday, November 11, 2015 Basin I Event Summary Event IPeak Q (cfs) (Peak T (hrs) ,Hyd Vol (acft) Area (ac) I ethod `Raintype 2 year 0.0182 8.17 0.0162 0.5300 SBUH ;TYPEIA' 10 year , 0.0783 8.17 0.0416 0.5300 SBUH ;TYPEIA 25 year 0.1192 L 8.00 0.0580 0.5300 SBUH TYPEIA 100 year 0.1747 8.00 0.0790 0.5300 1 SBUH ITYPEIA Record Id: Basin I Design Method SBUH Rainfall type TYPEIA Hyd Intv 10.00 min Peaking Factor 484.00 (Abstraction Coeff 0.20 Pervious Area (AMC 2) I 0.53 ac IDCIA 0.00 ac IPervious CN 81.00 IDC CN 0.00 IPervious TC 15.75 min IDC TC 0.00 min Pervious CN Calc Description SubArea Sub cn Residential districts - 1/3 acre 0.53 ac 81.00 Pervious Composited CN (AMC 2) 81.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet sliort praiHe grass, and lawns.: 0.15 166.00 ft 4.00°Io 0.1500 1.60 in 15.75 min Pervious TC 15.75 min Licensed to: KPFF Inc. H ["'l L]L- i HI IIJ HHI I Il H'.flu' 14"'T'If i oil 0 mill 1 111 III■ ■'■111111111 III■1111111111 ■I■111■■■111111.■■111111 0■W■0■111 ■■■■11111111111111111000 ■■■■■■111111■ x n ❑ ❑❑®❑ ® ® ODM® BEIRDH® IM0❑❑® ® m ❑L= m❑❑®®❑m ❑ ❑❑❑❑❑❑ HIM ❑ Seaview Playf e d - Exiist na Swale Friction Method Manning Formula Solve For Discharge Ihptot Data . Roughness Coefficient 0.350 Channel Slope 0.01000 ft/ft Normal Depth 1.00 ft Left Side Slope 5.00 ft/ft (H:V) Right Side Slope 5.00 ft/ft (H:V) Bottom Width 2.00 ft f1tesiults Discharge 2.05 ft'/s Flow Area 7.00 ftz Wetted Perimeter 12.20 ft Hydraulic Radius 0.57 ft Top Width 12.00 ft Critical Depth 0.26 ft Critical Slope 3.18308 ft/ft Velocity 0.29 ft/s Velocity Head 0.00 ft Specific Energy 1.00 ft Froude Number 0.07 Flow Type Subcritical Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.00 ft Critical Depth 0.26 ft Channel Slope 0.01000 ft/ft Bentley Systems, Inc. Haestad Methods SoIB8addp~Master V81(SELECTseries 1) [08.11.01.03] 11/16/2015 5:4:26 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 2 Seaview Playfl'eld - Existing Swale VF, Ut,Dstal Critical Slope 3.18308 ft/ft Bentley Systems, Inc. Haestad Methods Sol lloO Master V81(SELECTserles 1) [08.11.01.03] 1111612015 5:44:26 PM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 2 of 2