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APPROVED ENG BLD2023-0686+Storm_Drainage_Report+6.2.2023_9.53.58_AM+3583786RECEIVED Jun 08 2023 Bracket's Reserve BLD2023-0686 COMPLIES WITH APPLICABLE CITY STORM CODE 11-Lot Plat 03/07/2023 9105 240t" Street SW Edmonds, WA 98026 Stormwater Site Plan Report Prepared for: Pacific Ridge Homes Date: June 11, 2021 Revision #2: February 2, 2022 d 0 O 36508 9 AV �GISTER� � \` IONAI , / 2/ 2/ 2 022 Prepared by: Rob Long, PE RAM Enqineerinq, Inc. 16531 13t" Ave W, Suite A108, Lynnwood WA 98037 (425) 678-6960 RAMengineeringinc.corn Job No. 20-024 Bracket's Reserve 11-Lot Plat Introduction: This summary report provides site design information for a single family 11-lot plat by Pacific Ridge Homes. This report includes storm drainage analysis to support permit review and approval. The property is located on the north side of 2401" St SW and west Edmonds Way (SR 104), in the southeast 1/4 of Section 31, T 27 N, R 4 E, W.M. Applicant: Pacific Ridge Homes 17921 Bothell -Everett Highway Bothell, WA 98012 Site Address: 9105/9109/9125 240th Street, SW. Edmonds, WA 98026 Tax Parcel Numbers: 00463301300301, 00463301300303, 00463301300400, and 00463301200403 TABLE OF CONTENTS SECTION PAGES A. Project Overview.............................................................................................................................. 5 B. Existing Conditions Summary........................................................................................................... 3 C. Developed Site Hydrology.............................................................................................................. 30 D. Additional Reports and Studies........................................................................................................ 1 E. Construction SWPPPP Requirements................................................................................................ 2 F. Operation and Maintenance Guidelines.......................................................................................... 14 RAM -noineering, Inc. Bracket's Reserve RAM No. 20-024 Stormwater Site Plan Report A. PROJECT OVERVIEW: This report provides engineering information for the proposed construction of a 11-lot single family residence plat on a 107,474 sf (2.467 ac) parcel; the project is located on the north side of 240t" St SW west of Edmonds Way (SR 104) in the City of Edmonds. The applicant, Pacific Ridge Homes proposes to remove the three existing residences and all existing hard surface to construct the 11-lot plat on the project site. This report provides the evaluation for the 11-lot proposed single-family residence development. Summary of Minimum Requirements for Category 2 Project: Minimum Requirement #1 —Preparation of Storm water Site Plan. The proposed site development consists of developing about one acre of land and creating/replacing about 50,050 sf of hard surface area. Thus, the project is classified as a Category 2 project per the City's classification system. Per ECDC 18.30, Category 2 projects must comply with Minimum Requirements No. 1 through No. 9. The civil site development plans and this report have been prepared to address the projects impacts. Minimum Requirement #2 — Construction Stormwater Pollution Prevention (SWPPP). A construction Stormwater Pollution Prevention Plan (SWPPP) has be incorporated into the site development plans. A summary of the site's erosion control measures that evaluates the typical 13 elements of a SWPPP are included in section E. The total site disturbance area of the project will exceed one acre, thus a formal Notice of Intent application for NPDES coverage will be made to the Department of Ecology prior to the start of construction. Minimum Requirement #3 —Source Control of Pollution. Specific source controls are not required for single family residential sites. General requirements for these sites include preventing the discharge of pollutants to the City's storm drainage system per Edmonds City Code Chapter 7.200 (Illicit Discharges). This includes common household items such as pesticides, herbicides, fertilizers, detergents and fluids from vehicle maintenance. Single family residences shall incorporate DOE's S411 BMPs for landscape and lawn vegetation management. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls. The project site is located on a knoll that slopes off in nearly every direction. Generally, the site is made up of two site sub - basins. A north sub -basin that includes the site areas that slope off to the north and west ultimately flow to the west to a depressional wet land area located on the adjacent Madrona School property. And a south RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page A-1 site sub -basin that includes the runoff that flows east and south from the site which is routed to the existing stormwater pipe system along 2401h St SW. The city's municipal separate storm sewer system (MS4) along 240th St SW flows west along the project's frontage and then turns and continues south along the east side of 92"d Ave W (private road). The wetland area on the Madrona School site west of the project site in the north site sub -basin is a depressional wetland that has an overflow connected to the 2401h St SW MS4 located about 85 feet west of the site; therefore, the project's runoff flows are in the same threshold discharge area in accordance with the City's drainage manual (DOE 2014) definition. The developed site will maintain north and south site sub -basins. The north site sub -basin will continue to have runoff from the undeveloped tree retention/preservation Tract 999. The south site sub -basin will include the developed street and lot areas of the project. A stormwater detention vault will be constructed in the south site sub -basin to provide flow control (MR #7) for the project. Release flows from the stormwater detention vault will discharge to the existing stormwater pipe system along 2401h St SW that flows westerly as described above. Therefore, the developed site will maintain the natural drainage systems and outfalls. See additional discussion of the site drainage basin and downstream systems included in Section C of this report. Minimum Requirement #5 — Onsite Stormwater Management. A site -specific geotechnical evaluation of the site's soils demonstrates that infiltration is a not a viable option for stormwater management onsite due to the underlying glacial till soils and significant grading that will be required of the project. Additionally, adequate flow length/slope paths will not be available for the individual building lots for any dispersion type BMP. Thus, only post construction soil amendment is proposed for onsite stormwater BMP. See civil site development plans and Section C for additional stormwater BMP evaluation and construction details. 5.6 Minimum Requirement #6 — Runoff Treatment. The project will create/replace about 17,200 sf of pollution -generation hard (impervious) surface (PGHS) onsite with the proposed plat road, frontage improvements and driveways of the project. Thus, due to the fact the project will create more than 5,000 sf PGHS, the project will install basic water quality treatment stormwater filters with the proposed site development. The stormwater treatment catch basin filters will be placed downstream of the proposed detention pipe located along the southerly boundary of the site. A full summary and design of the stormwater treatment filters are included in Section C. 5.7 Minimum Requirement#7— Flow Control. An onsite stormwater detention vault system located in the site's southern site sub -basin will provide flow control to mitigate the proposed development. The detention vault system has been designed to meet the flow control standards of a Category 2 project in a creek or lake basin (restrict the stormwater discharge duration for half the 2-year to 50-year storm events using a continuous storm event model) due to the fact the downstream path enters natural fresh water systems prior to discharge to the Puget Sound (see additional decision below in MR#8). The detention vault has been sized using WWHM software; a full overview of the project's stormwater flow control measures are provided in Section C below. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page A-2 5.8 Minimum Requirement #8 — Wetland Protection. There are no known wetlands on -site. However, there is a documented existing wetland area west of the site and appears to potentially be an existing wetland area south of the site on private property. The westerly wetland is located on the Madrona School site and has been documented as a Category III depressional wetland with a 60-foot buffer. The westerly wetland is about 75 to 100 feet away and thus the 60-foot buffer does not extend to the project. The potential southerly wetland area is located on private property south of 240t" St SW and east of 92nd Ave W. Wetland Resources Environmental Consulting has estimated that the southerly wetland to be a type III or IV wetland. The buffer from a wetland on the south side of 240t" St SW would be interrupted by the 240t" St SW improvements and would not extend to the project site (per ECDC 23.40.220.C.4.). See additional offsite wetland discussion include in the project's Critical Area Reconnaissance Report prepared by Wetland Resources Environmental Consulting. Site stormwater runoff will indirectly discharge to both the west and south wetland areas. The release stormwater flows will meet the required runoff treatment (MR#6) and flow control (MR#7) as listed above. The project will not construct stormwater treatment or flow control facilities in the wetlands or the associated wetland buffers. Due to the fact the project indirectly discharges to the adjacent wetland areas, the project will meet the wetland protection guideline criteria of the Stormwater Manual Appendix I-D, Guide Sheet 1-3. Guide Sheet 1 is not applicable due to the fact the adjacent wetlands are not Category I or II. Guide Sheet 2 is not applicable due to the fact the project is not utilizing the adjacent wetlands for stormwater treatment or flow control BMP/facility. Guideline Sheet 3 is not applicable due to the fact the adjacent wetlands category is not a I or II (Guide Sheet 1 listed) and the wetlands are no being modified to meet stormwater requirements. 5.9 Minimum Requirement #9 —Operation and Maintenance. An operation and maintenance summary is provided in section F. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page A-3 Parcel (Vicinity) Map: QUARTER SECTION TOWNSHIP N.W.6, L. RANGE E.W.M. SW 31 27 4 E Centerline ----- Lot Sloch — Section ---- City Limits Gw Lot —••• Subdiv — ROW — Quarter --- Tax Acct Major Water Other Lot ------ Vac ROW ----• 16th ---- Easement ............. Ap.uducr Jrhe Aares.,arSOce .u,n p.odsom oAnp.h xx. xez® Snohomish Conniy, wnshixgon Minor Water Other Subdiv — Vao Lot ----- NW-31-27-04 '}—"S 1-11/ — I Uo w N aIa' ""^ 2 C `J f Y, a 1-119 fi s 0 2 W m 01""- p 02 rii 01 2-088 "' -09i� N:1:..w .niN,.: 2-047 BLA- ,,B.s2� «,"• a 2 ,z2 ,•" i z ,»,,,, 2a z-o67: 2-D5432-054 A 09 u0 E r03 -oeo "^•2#080 .,,,,,�,w w:."�..:.2„ 7W... z-Deals-Des zoaq 08 -,2o-t-lzt' 1-116~ 01 1l 1 ,», 2-059 wv„. �z-D79 # -0 0 z t ,z,"„..;,..." j B ".....w: ,�.:, z,I 1115 02 10'" a t 2-065 , '`j - Roo K w..' .N. . a:.:,a.:: t - 02 �0105 04 s -o89a + 2-088 o '- o 2_072 F`f CONDO I 2-049 LLA LN2018 236TH ST SW ------ Ct1Y--OF EDMONDS-- N 754 m s a 1 Do roo 1 01 01 02 Da _ F 1 70 DELO E 2 �FRUITLAN ACRES TC !r- Oz 01 a 2� A co 0 „ 02.: 02 E f IO2^ }01 5 4 3 2 , 00 y 2 43 2"i' 4 3 S. 2 1 :04. .:,,,:g 01 :, L' 0$ , i102,,• 00 03 03 ,, e a x a„, 1004 3 i,,..�."„ t 3 4 ¢ 02 04 2 FQ 0 rn 05 03 03 ' 2> 01 01 02 01 01 01 'O 4 ro j 0 LL2002-301 (45 3 a �__ ]7""`1�. •..03so :.:OZ.. 02" 01 2 OAP F� °1 00 iAd CONDO PLACE AT 5 fi 392 v2.. 04 2 2 5�, 00 03 53 2 ::. "''f'I € 5 4 - , VILLA ROYALE CONDO(6887 ( EDMONDS 5 01 3 µtr ••02„ �,,naMe 3 ,s ,� 9 a ^.:......:. [ 3 z 00; S,R. 3 OS CONDO 0N4 �g qoa (10722) 100 a�n 00: 00 = 01 o a 03 : r i toy 100 #01 e 7 1 PH4 { 4 1 d ms 3 SITE v 9 fi 2 m C NMN,, OND SUMMERLIN i CONDOMINIUM ' 1 03 5 4 3 PH 2 PH 1 (5530) ,.Z R 139 (Co Dol lea ) 1 ye N 03 89C 161 SP 3 03 r 00 3 2 4 214 x'' j v i.2 0 11, � I ---- r---------238TH-ST 3YV------- w 1 d't3ri6 2 3 5 4 RSON ADD 01 '- 5 02` 01 i vorioo��aa10) n l\ 04 2' 01 i 03 3 074 , 06 01 s'a t15 P 02, 01 02 Z 01 03 DO 04 9 ;111 „aT, 01 12 k 00 13 i 5 R 00 14 is W -_.w N "2.. ' I� mom, 2 „•„ 02 1 01 U a C CONDO(11468) 0$ eEDMONDS2 µ� v, 2309ePH2Os , GREENERY (7002) it7y 03 00 n 84-035 -.02� 01 Ol 5 4 4 004 1, w 02 ¢ q 03 04 f 03 2 1 i' - 0-` 3 05 L°A 21 ..,.03, fi 3v 3 2 03 c04 "w�2P 01 Ol "' GALLED + _ 4 0 , 07 5 4 2� 7 2 O t 02z,p»,,., m 1 .»., w , 03 CONoo (6695� d z b7 m02 I� rl242ND-ST-SW V1 00 �01 00 - 02 B a , F r°�01,µ NYy, A03 ? 00" '¢'t 3 AMEHDI 82 4¢0 242ND- TOSW - D3011 jjz 4 I d # I 00 00 .:, �,;, "°2 T' 00 00 s-____.-_._ a 9.._ a - '02 §I: 01 ' �� 01 EDMOND 1�4,p..,z3 _ "2 2 w 7 10 F 15 s+02 t, �^02 02 3 VILLAGE FZ wU 4-049 {}""`t 2 Agl,�°"+�4-03D �N �,:: :LV '-fi `r'. �„2 02 ?111B " , 3 ,7 ' 14 07 WmoSt 03 03 ,Nd,.�a CONDO Na i ___-SR`-FOd... 2 i ,.- 02" 01 0_ rn s01 01 a 5 t2 t30 z a,,,,„„, a 03 z " � 02 3 m 04 03..' .i14 (6781) z O— NON gS"~4-028 02 02 L. 3 3 03 Z 3 4 Y'S A NO 5 s T 5117) 4 OLYM 4 n C CO 5 T 01 2, 4 _ X ❑� 4-027 �:::«."»,w".�:.:: 4-029 03 ,., 5y '4 _" 02 5 v1 Id rn 3 fi a 3 4 02 W OD PLA2 170082 9 3 a 4Q O30 1 S 7 MT.2 3u, :,�..:4 Q 2 2 1 3 4-033 x K - s c` Ot 1 7 2l - 2 * B 9 53 Z NOGREST CONDO = 09 ; 0$ �. : +z a s = m rn 1 l 6 (C,59) 1 04 UJIOV (8454) oo �� LAKE MCALE 1 .-�.4APFFi^81•�-•-N�BSTMh9Fr�+-�-.�-.-��.-��---- RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page A-4 Site Development Plan: 9LOCK 12 HAND VIEW TRACTS OUTFAll I LOT 5� �V"N I LOT 4 E_I216226.37 i II _ C-1266296.25 l l�� II �� \\\•�`•� \ \ VILLAGER I d l ; i t/ ,i 1, Il +`� t \ � - - REC. NO 8112285001 M177GA770K ARYi M TRACT 999 �j,� (CROSS -HATCHED ARCAX j,' I \ \ .. , ` — — I \ - 1 TRACT 998 �- �'I,1iI'II\I ROLLED Rs 6RA7E _ 34830, 12.22-R7 rl}`\�``\, l��`� •. RIXL®LTIR@ _ - ._I _ - RN 4522,8444a49FRAME WT- I 3M.�0q 12.21' L7 006 \ 6'!E 44fl49 (WT-E AM! 152.64 - �'$ f2' IE 44&34 ON-E) I II a . \ �.` ` ` \\ ,` \ 6' ✓E 44634 (M-w) 72' u (OUT-5) II t1 - k eI I AA Ox Lo �Vi nfa ri---- ICe 4 ', 8 8y I i I WRO I i - I i \\ EDMUNDS 11 l l I 1 i FRAME s GRA E 11 I HIGHLANDS 2+4C.04 iz22' LT _ REC. NO. hTN 4ax55,- 20040411514 l a I i i I i 12'I IE 445.05 r—) 2i (WT Rp1FL 1 i ; k i ;6'�r�j 4{wAs (°ur-ln �`kxAME s An, g\ 3 IN0 " 111 RM 449.55 `, anTM I�. i ; / 'I I 1 ' 6 ;!F M5.20 ON-E) 2,K4A420(Wr--w)rA 001509 p ces R.YLED CfiRB I I i l f - FRAME & R22 1 \ 1 Cli2 --- rl�I Rhw4fa 1222' Li 12 M78 F4IFR , 11 A' - j -' • t2' 444X N-289751. id _ rz" IE 436.00 (M N),� I i j I i E�I2662J755 -.-_ �1 f2' IE 438.OD, (M E) . a. I 4a2.71 f2- IF 427 so (M7 17 I i '1 I I iI r2" 1E 42S ]0 //0{/j�5) -�i 0.95X -12' W 3A' ---- Ih'RI!-L& F' ¢ . `'� _ IN57ALLED FRAME LRAIE I i IN f00A1 _ 1 1+36.0a 11.54' RT l 1 432.15 AD a UST TO NEW EC I 1 I iN VAULT _ RF7♦' 44014 I 1 IiE IY3.74 (C� NEW VEO __ 1 1 t t _ i -... 6• X.436. 1� (!N-f? fE 426.00 ((NN NEW 1 '� \ - 6- 12' 5 411.65.T 1,7' IE dJ6.73 (d/T++l�'.5".A IE 42374 _ f2" IE 'N LIU M 5WIN M FALC \ �� ._ _ '�` 6• St, - FLONiME OF NEW LERIICAL ��':' -^ram - O AX MIN - F� SD STZ EV57MC ME -- T - \ �o ' 240TH ST SW 11 \ 59NH IOIfH J `----------- — — — — — — — — — — — — — — CHB aI� 63230 6' CONC IE 44 OF EX D LOCATMMU f B' CQNC IE 44 i O< E! DRY UMIilES 30U0 54LoOrAw K861 LT SSMN I0019 RIM 94 C. 12- 441 600 6' IE 416.76 (E) B * 6. ' 44360 ON-E) 6" IE 41& 76 (S) 7YAE d-46 6' 1E !4A ID (M-N) 6+722.% 1378' LT 12- IF 4U20 (Our -iv RN 4J7. f0 12: fE 42d00 (M-E) 12' 1E 425.J1 (M-N) 12' fE 423 3M (OUT-) RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page A-5 B. EXISTING CONDITIONS SUMMARY Existing Conditions. The total site consists of about 107,474 sf (2.467 acres) and is currently occupied by three existing single-family residence and detached garage with access driveways off 2401" Street SW. The existing houses are surrounded by grass lawn, garden, and landscape areas with several large mature trees throughout the site. The site is surrounded by single family residences to the east and north; Madrona K-8 School to the west; and 2401" St SW to the south (see attached aerial photo). Soils: In accordance with the project's site -specific geotechnical engineering study by Earth Solutions NW, LLC the on -site soils consist of silty sand (USCS: SM) glacial till deposits. The subject site is underlain by glacial till deposits (Qvt, Vashon till soils). Full soils description is included in the project's site specific geotechnical engineering study by Earth Solutions NW, LLC. The site is located on a knoll and slopes off in nearly all directions. Slopes range greatly with the side slopes of the knoll reaching slopes up to 66% grade. The knoll creates a drainage basin ridgeline that bisects the site into two sub -basins, a south sub -basin and a north sub -basin. The north sub -basin generally drains north and west and ultimate drains to the offsite wetland area west of the site on the Madrona School property. The south site sub -basin generally drains south towards 240t" Street SE and east to the neighboring plat of Edmunds Highlands. The Edmunds Highland plat collects stormwater runoff from the project site in addition to the site development areas of the Edmunds Highlands plat. The Edmunds Highland system has a discharge conveyance system the directs stormwater to 240t" Street SE and west combining with the southerly runoff from the project site. As discussed above, off -site to the west on the Madrona School property there is a wetland area that collects/receives the stormwater runoff from the site. Additionally, there appears to be an offsite wetland area on private property south of the site on the south side of 240t" Street SW. No wetlands or known prescribed City buffers extend onto the subject site. See additional offsite wetland discussion include in the project's Critical Area Reconnaissance Report prepared by Wetland Resources Environmental Consulting. For reference an aerial photo and basin map are provided below. Additional discussion of the local drainage basin and downstream path is discussed in Section C of this report. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page B-1 Aerial Photo (City of Edmonds GIS, 2017 photo): RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report 4 Page B-2 Existing Site Basin Map: BLOCK 12 HA ND VIEW TRACTS V.7 / PG.2O LOT 5-, LOT4 p60g A I TTZA. 9 I V I I Illlll ttt..r`` \ \T 3 ` \` _ FWND i/2' REBAR 1 / / lie, re%:. - �Zre$ r'.\rP•c `` �1 �\ \ 0. 1'E. OF LOT CORNER. I / II Iy v \ II (1110712020) NW-CORNER.¢NCE-rs I ikp p, '- f = - T`� -4 k• - `\„ �\ i<�\\ - _440- 12W. ' OF LOT LINE / I I _� \:�,•/ \4 �(`� -�, �•. \ \I FENCE CROSSES / LOT LINE 55 8'N. / OF LOT CORNER. r T 4\ NW CORNER �fEE��IICE IS VILLAGER \�.2'WOFI.dTUNE� s'cLFNc REC.N0.8112285001 S`� �,,/�, �,7�• `_�\ FENCE CROSSES _ _ FENCE CROSSES LOT LINE B.SN. OF S INE 98pNgK�EOF LOT CORNER. I..2cc� tS Z�D'IrN FENCE IN TERSE�',�Q('I \Z 4E LOT LIFif\ Y G IS 64CLFNC LOT GATE II36 I I \...1Y 1.-�p'NEv, L, ��T rro'il E SND FENCE ri ISO T LINE. ' NORTH BASIN ENE - ; r` s — — — FOUND 1/Y REBAR a 1.262 Ac. -p�Y 19T END SW FEN�YE CORNE/j AND SMASHED CAP 05N�05E. 0. 1N. OF LOT CORNER its (1110612020) II -W - .y., %-,'q°°!`" >♦�`'ti�r�r .yll TRACT 998 24a�� T t 1�0(Lj ••Y� A�`- `=`�.F- i ♦ �. H0�55T, Ml}}£ ..-. �_l i I \ FOUND 1/2- REBAR �� I♦♦♦� / /,yil \ it AND CAP "LSA 22969' CHICKEN y-p'` O� I I 0.7'N.xO. i E OF LOT 7 ,ifs FENCE ♦♦ 1, � II FI 41 CORNER (1110612020) 'IdAn ��', ) \I� x'1 I -a " I I ENCE INTERSECTION l\;.w �� . �i I` �~\4 I I IS 05E OF LOT LINE. p�T SITE lip E EDGE GRAVEL 15 SITE � >o�\\/� \\ do\\\�` � III\ 1.5W. OF LOT LINE. 2.467 Ac. -''�` \ \\\\ {� 4 ' �\ ._`A ♦♦♦♦ I TT rl \`.� \`Ili \I `�` �C� - FOUND 1/2" REBAR A�T� 5�*c]p`� \ -�, _ I♦ I I I _ AND CAP 'LSA 22969' `; �,✓ �/ I '� \"� PO II UTILITY - J i AT LOT CORNER. IIII = f1_P17NO SIGNAL 4' I �- \ lJ 06TzaT — — NOS II I - n? II E. EDGE OF ASPHALT IOL \ I �t - �T ` III i CROSSES LOT LINE 72'S. 01 I t Ta'1 r" e 0 1 '11-p4G,nT QyYI 1 \ \ T 'I FOUND REBAR AND GAP. :T 15 I` �\ �I �\ �gtsv� �' ,$y� 1 Y` ;T I�--• o ��}7 EDMUNDS HIGH, r1 Pq>HQ R ' I -�`�. Y� .b.- / -,'I ='N'' 7-i. - _'� _7 � REC. NO. 200404 Z 4, �� _ �, rI III J o \ _ T\`II I I X`I�TI es�tt�N" �' ��, SOUTH BASIN ruNO1/z"REBAR I I i rro�d 6rclIFPoG,N I11 J lrT III e.. , 1.205 AC. ,AND CAP LSA 22969" ��--G --yy AT LOT CORNER. - I � Ii II i 1 III , I I% ♦ CONC. BLOCKFENCE IN> ERSE 1. I a i AC �4 ,,,,`�� . / 4' r P+ ✓y 'Y� r FEN D 6/ET OF LOT LINE. / Iy�`!C 'r'' - _ "7}•ry� IY'�" I Ty FENCE INTERS£C AON M1 / 1� __ F1J 1 T `� h11 �• IS 06E OF LOT LINE. 2 srzs zoo sr sw �' 1 5 STO WOOD ' .31P9 2447F_I_ST .4w4/ III I , ' FOUND 7/2' REBAR F ` �� FRAM�FIOUSE m : 'i STO11Y W000`ERA � III 7 I ); \ �x AND CAP L5A 22969" )� {-s� -+IBHSE W/&ASSANr \ j. } T _J i 0.1 £ OF LOT CORNER. (1110612020) �` 'x ✓ ` Y _N > J` c jt FENCE INTERSECTION I �('� ))pqJT t ��O.fiE OF LOT LINE. CK I' -! ` IY>� E! L�Y�4•q -j pTASPHALT k�,�,,Y J 1 Irw 11 ��/oT�� yl ' \ 6BFNC E. OF LOT I I. �, y �� r _ TMr` �F `�cF J �I ('v��/I� cI SW FENC£ 1 T. 1 'gsx�'i-, ' ti , �LaI `__'>(,, I +.`.'I \y1 'I! 1f I �� -i CORNER IS E. �/ l O [�. s♦. L A 1 I OF LOT LINE. E EDGE ASPHALT ` W SRy,`/�ez ` I \ IS 3 5'W OF LOT OL _ CORNER. FOUND 1/2- REBAR AND CAP 'LSA 22969' 1 -- v+ W- Wes- yy x LL f CAP _ _ Y />R _ SS — SS— —SS— —SS .�ea+sea6S'z.+-�'— —SS SS— G _ __ " IM/TEO SiGH.DISTANCE _ I+--G ——G—=—<fj4----Scgc��--G T .J T - \ yBOX ADDRESS ON \. I / 5llOSK "NO PARKINGr ELE✓.=455.40' __ _— --. ---- EASF-BF-+IERE— SDMH 1004J i Q3 S REST 8M A' RIM 432.15 FOUND :Y' IN 1 . ELEY.=429.50' 12' CONC lE 42742 (E) SSMH 10118 DISK /N 4"X4' C `` 12" CONC lE 4T3.74 (W) FOUND 'X /N 1 3/4' RIM 452.30 MONUMENT DOWT RNN i BRASS DISK /N 4'X4' 6" CONC lE 445.85 (N) (1110612020) CONCRETE MONUMENT 8" CONC lE 444.77 (W) DOWN 0.3' IN CASE. 0110612020) RAMEngineering, Inc. Bracket's Reserve RAM No. 20-024 Stormwater Site Plan Report Page B-3 C. DEVELOPED SITE HYDROLOGY. Developed Conditions. The proposed project includes the construction of 11 single-family residences and associated frontage improvements, driveways, and utilities. All existing structures and impervious surface onsite will be removed/replaced with the site development; landscaping and grass lawn around the new residence will stabilize the site upon building construction. The project proposes to create and/or replace 50,050 sf of hard surface with the complete site development, all existing onsite hard surface will be removed with the project site development. All of the new/replace hard surface will be routed to the stormwater treatment (filters) and flow control (detention vault) facilities in the site's south sub -basin. The following is a summary of the proposed new/replaced hard surface and pervious areas: Site South Basin South By-pass South Offsite Run-on Site North Basin Road = 11,160 sf 1,640 sf 1,960 sf 0 sf Building Rooftop = 24,200 sf 0 sf 0 sf 0 sf Driveways = 4,400 sf 0 sf 600 sf 0 sf Sidewalks = 6,680 sf 970 sf 430 sf 0 sf Miscellaneous = 1,000 sf 0 sf 0 sf 0 sf Total = 47,440 sf 2,610 sf 2,990 sf 0 sf Total Hard Surface = 1.089 ac 0.060 ac 0.069 ac 0.000 ac Site South Basin South By-pass South Offsite Run-on Site North Basin Lawn/Landscape = 27,830 sf 2,860 sf 1,860 sf 0 sf Forest = 0 sf 0 sf 0 sf 30,464 sf Total = 27,830 sf 2,860 sf 1,860 sf 30,464 sf Total Pervious Surface = 0.639 ac 0.066 ac 0.042 ac 0.699 ac Total = 1.728 ac 0.126 ac 0.111 ac 0.699 ac The below development site basin map delineates the site south basin, south by-pass, south offsite run-on and site north basin areas. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-1 Developed Site Basin Map: BLOCK 12 MANSUR" SOUND VIEW TRACTS V.71PG.20 LOT 4 N-2WV�.� I - OUTFALL LOT45 E-1�62� RIM 441.63 1�, 6 Rhw �?j - f AE 441.00 (OUr 8 -W) VILLAGER I'� fJ i�i `\OT REC. NO. 8112285001 5 TREE RE7VV77 j Site North Basin U170M 77GA7 0.699 ac TRACT.999 (CROSS -HATCHED AK4 I HV, TRACT 998 6 7 RE r C85 I ANF W X-A. .118AW, M221' RT, RW 452.84 2' Ir oa� CRA 7E Ir 3+83,00,12.22'LT RW 452.64 f2- E 448J4 ON-E) 5' AE 448.34 (N-W) 12"IF 448.34 (OUr-S) A�DX L�RM UnUpE Site South Basin EDMUNDS FRAME— !Al�,�N HIGHLANDS LT REC. NO, �2 1.728 ac 200404125344 CH f 44105 (Wr S) Raav PuRe 3 FRAME&IM'. 2.40.M R#,f 449.55 DIRT 6- hE 44&20,mV-E) mox Ik CURB A 2 BY L 1227L 1 2 HL�R 11 -,-- 'R" W� r4-4 It "Y 02- IF 436.� (IN-V) �62JZM ". , �Z J 442, 02- X 436LOO (IN E) I j If 4�77140 (N-W) 21'12' SO 12 x �6.m (our-W) — — — — — — — — - , t",) 0 OA�x ff 42� L. ;2, CE 3A 12' ff 42750 FRAME & CRATECRATEWN7RM SE INSTALLED 10 A VEMNPO✓4401r 07,5*'RT `i —1. RIM 440,14 ,2IE 42742 (5)0 .6'Ot 4J6.15 (W-NE) 12 E 42,174 e-12'SD & .659 �6.;5 (�F-W) f "M . EWTW 12- fE 42A74 ------ (�W LID M SWN TO FALL .0 FLI)KiNE OF KE� �FRnCAL 08� - — — — — — — — — f.02% 94-r2' SD 161IN Demo J South By-pass T South Offsite Basin 240TH ST SW Run-on Basin 0.126 ac - - — — — — — — — — — APFROX L—OCA — - — — — — — Cm T/aY 0.111 ac or EX Owy U71urfs SOLIO L"m Lo 10.66.54. 16.86'LT 11. 42 91 RN 44800 a�219 44160 ON E) g: JIZ7e E 4416eY62 �CS� a+72.2a 1378'LT 6" 6 4" FO (IN-N) RN 437 �0 1,7- IF "120 (WT-4) 72: L- 42900 C (W-HW-E) 12 12. LF 42aJ1 (OUT-0 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-2 Offsite Analysis. The site is located within the City of Edmonds, Edmonds Way watershed basin. The Edmonds Way basin is a centralized urban basin that collects stormwater runoff from residential areas and a commercial corridor along Edmonds Way in the City Edmonds. The watershed ultimately discharges flows northwesterly to Puget Sound (see attached watershed map). The project site is located on a knoll that slopes off in nearly every direction. Generally, the site is made up of two site sub -basins. A north sub -basin that includes the site areas that slope off to the north and west ultimately flows west to a depressional wetland area located on the adjacent Madrona School property; and a south site sub -basin that includes the runoff that flows east and south from the site which is routed to the existing stormwater pipe system along 240th St SW. The city's municipal separate storm sewer system (MS4) along 240th St SW flows west along the project's frontage and then turns and continues south in an open ditch along the east side of 92nd Ave W (private road). The wetland area on the Madrona School site west of the project site in the north site sub -basin is a depressional wetland that has an overflow connected to the 240th St SW MS4 located about 85 feet west of the site; therefore, the project's runoff flows are in the same threshold discharge area in accordance with the City's drainage manual (DOE 2014) definition. The open ditch along the east side of 92nd Ave W flows south through residential private property in a collection of culverts and open channels. The stormwater system bends westerly and continues westerly through the Bracket Apartment Homes complex and enters the City's MS4 system along Firdale Ave near 243rd PI SW (about 2,800 feet from the project site). The stormwater system in Firdale Ave bends back north along 100t" Ave W and combines with the Edmonds Way main trunk stormwater system (about 1.4 miles from the project site). The Edmonds Way stormwater system continues northwesterly and eventually discharges to the Puget Sound about 3.4 miles from the site. See attached watershed and downstream drainage facility map for the local downstream path. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-3 Watershed Basin Map City of Edmonds Washington ewer Q Eppd epee rood Malls rm see eme —"7■ i N m Hmdl, Z, yt Pond Pipad 1h.11A Zv.. P—, '—d 1-d it �SITE 74 llp5V 1 W., 1-1, 580 -t 9501 March 201E Edmonds Watersheds RAM Fngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-4 Downstream Drainage Facility Map (City of Edmonds GIS) +C 3 -1 1 V PD15�i2 � _ North Basin discharges and flows to Madrona 4 �, a f i! School wetland 0 00 _ area west of site. 7• O0 0 00 0 e I oil - wit Madrona School og ago — Wetland overflow ° y SITE = to 240th St SW Storm System. PD15-21 PDVS-60 South Basin ,• �' �,�' � CL discharges and r flows south along { do i I r ,`` •i! _ dw92nd Ave W s (private road). ► 0 4 - _ Pi 0 c R.4MEngineering, Inc. Bracket's Reserve RAM No. 20-024 Stormwater Site Plan Report Page C-5 Stormwater Modeling. As discussed above the site is comprised of two drainage sub -basins within the Edmonds Way Basin; the two site basins include a south basin and a north basin. An underground detention vault installed along in the lower southwest of the project site will provide stormwater flow control for the project. A vault 76 feet long, 33 ft wide (two 16.5 ft cells) and 12.5 feet deep will provide approximately 31,350 cf of storage to mitigates the project's new and replaced hard surface and converted pervious surfaces. Attached is the stormwater analysis documentation output from the Washington State Department of Ecology's WWHM2012 stormwater modeling software for both the south and north basins of the project. A summary of the stormwater modeling pre-existing and post -development conditions are provided below. Flow Control Summary Table: Drainage Basin Information South Basin North Basin 1.402 Acres (52.6%) 1.262 Acres (47.4%) Site Basin Area Pre -Developed = Developed = 1.965 Acres (73.8%) 0.699 Acres (26.2%) None Type of Storage Proposed Detention Vault Approx. Live Storage Volume (cf) 31,350 cf None (76' x 33' x 12.5' ) Alderwood Gravelly Sandy Alderwood Gravelly Soil Type(s) (NRCS) Loam (Till Soils) Sandy Loam (Till Soils) Pre -developed Runoff Rates Q (cfs.) 2 yr. 0.036 cfs 0.021 cfs 10 yr. 0.066 cfs 0.040 cfs 50 yr. 0.101 cfs 0.050 cfs Post -development Runoff Rates (unmitigated, without quantity controls) Q (cfs.) 2 yr. 0.367 cfs 0.012 cfs 10 yr. 0.594 cfs 0.022 cfs 50 yr. 0.842 cfs 0.028 cfs Post -development Runoff Rates (mitigated, with quantity controls) Q (cfs.) 2 yr. 0.029 cfs - 10 yr. 0.047 cfs - 50 yr. 0.069 cfs - Offsite Upstream Area 0.111 ac. None (Offsite "Run-on") Q (cfs.) 100-year Pre -developed = 0.119 cfs 0.053 cfs 100-year Developed = 0.962 cfs 0.030 cfs 100-year Developed Mitigated Release = 0.079 cfs - RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-6 South Basin WWHM Input/output Data: WWHM2012 PROJECT REPORT Project Name: 20-024 Brackets Reserve- vault Site Name: Brackets Reserve Site Address: 20-024 City Report Date: 10/1/2021 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1- Site Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod 1.165 Pervious Total 1.165 Impervious Land Use acre Impervious Total 0 Basin Total 1.165 Element Flows To: Surface Interflow Groundwater Name : Basin 2- Upstream Bypass: No Groundwater: No Pervious Land Use acre C, Lawn, Mod .042 Pervious Total 0.042 Impervious Land Use acre ROADS MOD 0.045 DRIVEWAYS MOD 0.014 DRIVEWAYS STEEP 0.01 Impervious Total 0.069 Basin Total 0.111 Element Flows To: Surface Interflow Groundwater RAMEngineering, Inc. Bracket's Reserve RAM No. 20-024 Stormwater Site Plan Report Page C-7 Name: Basin 3- By -Pass Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .126 Pervious Total 0.126 Impervious Land Use acre Impervious Total 0 Basin Total 0.126 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1- Site Bypass: No Groundwater: No Pervious Land Use acre C, Pasture, Mod .639 Pervious Total 0.639 Impervious Land Use acre ROADS MOD 0.256 ROOF TOPS FLAT 0.556 DRIVEWAYS MOD 0.101 SIDEWALKS MOD 0.176 Impervious Total 1.089 Basin Total 1.728 Groundwater Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 Name : Basin 2- Upstream Bypass: No Groundwater: No Pervious Land Use acre C, Lawn, Mod .042 Pervious Total 0.042 Impervious Land Use acre ROADS MOD 0.045 DRIVEWAYS MOD 0.014 DRIVEWAYS STEEP 0.01 Impervious Total 0.069 Basin Total 0.111 Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 RAMEngineering, Inc. Bracket's Reserve RAM No. 20-024 Stormwater Site Plan Report Page C-8 Name : Basin 3- By-pass Bypass: Yes Groundwater: No Pervious Land Use acre C, Pasture, Mod .066 Pervious Total 0.066 Impervious Land Use acre ROADS MOD 0.038 SIDEWALKS MOD 0.022 Impervious Total 0.06 Basin Total 0.126 Element Flows To: Surface Interflow Groundwater Name Vault 1 Width 33 ft. Length 76 ft. Depth: 12.5 ft. Discharge Structure Riser Height: 12 ft. Riser Diameter: 12 in. Orifice 1 Diameter: 0.433 in. Elevation: 0 ft. Orifice 2 Diameter: 0.433 in. Elevation: 9 ft. Orifice 3 Diameter: 1.181 in. Elevation: 10.8 ft. Element Flows To: Outlet 1 Outlet 2 Vault Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) 0.0000 0.057 0.000 0.000 0.000 0.1389 0.057 0.008 0.001 0.000 0.2778 0.057 0.016 0.002 0.000 0.4167 0.057 0.024 0.003 0.000 0.5556 0.057 0.032 0.003 0.000 0.6944 0.057 0.040 0.004 0.000 0.8333 0.057 0.048 0.004 0.000 0.9722 0.057 0.056 0.005 0.000 1.1111 0.057 0.064 0.005 0.000 1.2500 0.057 0.072 0.005 0.000 1.3889 0.057 0.080 0.006 0.000 1.5278 0.057 0.088 0.006 0.000 1.6667 0.057 0.096 0.006 0.000 1.8056 0.057 0.104 0.006 0.000 1.9444 0.057 0.112 0.007 0.000 2.0833 0.057 0.119 0.007 0.000 2.2222 0.057 0.127 0.007 0.000 2.3611 0.057 0.135 0.007 0.000 2.5000 0.057 0.143 0.008 0.000 2.6389 0.057 0.151 0.008 0.000 2.7778 0.057 0.159 0.008 0.000 2.9167 0.057 0.167 0.008 0.000 3.0556 0.057 0.175 0.008 0.000 3.1944 0.057 0.183 0.009 0.000 3.3333 0.057 0.191 0.009 0.000 3.4722 0.057 0.199 0.009 0.000 RAM Engineering, Inc. RAM No. 20-024 Infilt(cfs) Bracket's Reserve Stormwater Site Plan Report Page C-9 3.6111 0.057 0.207 0.009 0.000 3.7500 0.057 0.215 0.009 0.000 3.8889 0.057 0.223 0.010 0.000 4.0278 0.057 0.231 0.010 0.000 4.1667 0.057 0.239 0.010 0.000 4.3056 0.057 0.247 0.010 0.000 4.4444 0.057 0.255 0.010 0.000 4.5833 0.057 0.263 0.010 0.000 4.7222 0.057 0.271 0.011 0.000 4.8611 0.057 0.279 0.011 0.000 5.0000 0.057 0.287 0.011 0.000 5.1389 0.057 0.295 0.011 0.000 5.2778 0.057 0.303 0.011 0.000 5.4167 0.057 0.311 0.011 0.000 5.5556 0.057 0.319 0.012 0.000 5.6944 0.057 0.327 0.012 0.000 5.8333 0.057 0.335 0.012 0.000 5.9722 0.057 0.343 0.012 0.000 6.1111 0.057 0.351 0.012 0.000 6.2500 0.057 0.359 0.012 0.000 6.3889 0.057 0.367 0.012 0.000 6.5278 0.057 0.375 0.013 0.000 6.6667 0.057 0.383 0.013 0.000 6.8056 0.057 0.391 0.013 0.000 6.9444 0.057 0.399 0.013 0.000 7.0833 0.057 0.407 0.013 0.000 7.2222 0.057 0.415 0.013 0.000 7.3611 0.057 0.423 0.013 0.000 7.5000 0.057 0.431 0.013 0.000 7.6389 0.057 0.439 0.014 0.000 7.7778 0.057 0.447 0.014 0.000 7.9167 0.057 0.455 0.014 0.000 8.0556 0.057 0.463 0.014 0.000 8.1944 0.057 0.471 0.014 0.000 8.3333 0.057 0.479 0.014 0.000 8.4722 0.057 0.487 0.014 0.000 8.6111 0.057 0.495 0.014 0.000 8.7500 0.057 0.503 0.015 0.000 8.8889 0.057 0.511 0.015 0.000 9.0278 0.057 0.519 0.016 0.000 9.1667 0.057 0.527 0.017 0.000 9.3056 0.057 0.535 0.018 0.000 9.4444 0.057 0.543 0.019 0.000 9.5833 0.057 0.551 0.019 0.000 9.7222 0.057 0.559 0.020 0.000 9.8611 0.057 0.567 0.020 0.000 10.000 0.057 0.575 0.021 0.000 10.139 0.057 0.583 0.021 0.000 10.278 0.057 0.591 0.022 0.000 10.417 0.057 0.599 0.022 0.000 10.556 0.057 0.607 0.022 0.000 10.694 0.057 0.615 0.023 0.000 10.833 0.057 0.623 0.030 0.000 10.972 0.057 0.631 0.039 0.000 11.111 0.057 0.639 0.045 0.000 11.250 0.057 0.647 0.050 0.000 11.389 0.057 0.655 0.054 0.000 11.528 0.057 0.663 0.057 0.000 11.667 0.057 0.671 0.060 0.000 11.806 0.057 0.679 0.064 0.000 11.944 0.057 0.687 0.066 0.000 12.083 0.057 0.695 0.323 0.000 12.222 0.057 0.703 1.118 0.000 12.361 0.057 0.711 1.885 0.000 12.500 0.057 0.719 2.304 0.000 12.639 0.058 0.713 2.596 0.000 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-10 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.333 Total Impervious Area:0.069 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.747 Total Impervious Area:1.218 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.035471 5 year 0.052343 10 year 0.065532 25 year 0.084677 50 year 0.100859 100 year 0.118791 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.028839 5 year 0.039122 10 year 0.047127 25 year 0.058702 50 year 0.068463 100 year 0.079265 0.01 Cumulative Probability 1 10.0 x xxxx 1.0 r x r x r...x;::1-:z;rr:-z:,:: + 501 0.5 1 2 5 10 20 30 50 70 80 90 95 98 9999.5 0.01 Stream Protection Duration I LID Duration Flow Frequency L Water Quality I Hydrograph I Wetland Input Volumes LID Report Recharge Duration I Recharge Redeveloped I Recharge Mitigated Analyze datasets CompactWDM I Delete Selected i- MonthlyFF F �-:] 501 •� redPOC 1 Pevelo ed flow r 7n1 Wk. to P0C 1 Mitigated :1 •1 802 POC 2 Mitigated fbw 1004 Vault 1 ALL OUTLETS Mitigated All Dalasets Flow Stage Precip Evap POC 1 POC 2 I Flood Frequency Method �' Log Pearson Type III 17B Weibull Cunnane Gringoden RAMEngineering, Inc. RAM No. 20-024 MM Flow Frequency A Flow(cfs) 0501 15m 0701 15m 0801 15m 2 Year = 0.0355 0.3671 0.0288 5 Year = 0.0523 0.4972 0.0391 10 Year = 0.0655 0.5944 0.0471 25 Year = 0.0847 0.7304 0.0587 50 Year = 0.1009 0.8417 0.0685 100 Year = 0.1108 0.9620 0.0793 Annual Peaks 1902 0.0426 0.4197 0.0272 1903 0.0286 0.4565 0.0304 1904 0.0545 0.5176 0.0355 1905 0.0210 0.2558 0.0237 1906 0.0199 0.2903 0.0223 1907 0.0493 0.3435 0.0288 1908 0.0312 0.3027 0.0248 1909 0.0338 0.3776 0.0256 1910 0.0579 0.3441 0.0289 1911 0.0302 0.3933 0.0278 1912 0.1176 0.7212 0.0514 1913 0.0420 0.2885 0.0243 1914 0.0763 1.0543 0.0611 1915 0.0237 0.2385 0.0227 1916 0.0295 0.4548 0.0315 1917 0.0184 0.2199 0.0176 1918 0.0320 0.3536 0.0251 1919 0.0229 0.2145 0.0205 1920 0.0362 0.3183 0.0266 1921 0.0322 0.2460 0.0260 1922 0.0390 0.3646 0.0286 1923 0.0339 0.3039 0.0260 1924 0.0316 0.5016 0.0310 1925 0.0200 0.2232 0.0190 1926 0.0347 0.4482 0.0277 1927 0.0347 0.3505 0.0235 1928 0.0301 0.2803 0.0260 1929 0.0540 0.4782 0.0323 Bracket's Reserve Stormwater Site Plan Report Page C-II Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1902 0.043 0.027 1903 0.029 0.030 1904 0.054 0.036 1905 0.021 0.024 1906 0.020 0.022 1907 0.049 0.029 1908 0.031 0.025 1909 0.034 0.026 1910 0.058 0.029 1911 0.030 0.028 1912 0.118 0.051 1913 0.042 0.024 1914 0.076 0.061 1915 0.024 0.023 1916 0.030 0.031 1917 0.018 0.018 1918 0.032 0.025 1919 0.023 0.020 1920 0.036 0.027 1921 0.032 0.026 1922 0.039 0.029 1923 0.034 0.026 1924 0.032 0.031 1925 0.020 0.019 1926 0.035 0.028 1927 0.033 0.023 1928 0.030 0.026 1929 0.054 0.032 1930 0.037 0.037 1931 0.032 0.025 1932 0.029 0.022 1933 0.034 0.026 1934 0.074 0.107 1935 0.028 0.022 1936 0.038 0.028 1937 0.050 0.033 1938 0.033 0.023 1939 0.020 0.026 1940 0.037 0.037 1941 0.037 0.037 1942 0.044 0.054 1943 0.027 0.029 1944 0.060 0.043 1945 0.031 0.029 1946 0.039 0.028 1947 0.023 0.020 1948 0.059 0.028 1949 0.054 0.038 1950 0.029 0.022 1951 0.037 0.033 1952 0.096 0.045 1953 0.083 0.044 1954 0.030 0.025 1955 0.025 0.023 1956 0.019 0.020 1957 0.033 0.025 1958 0.079 0.063 1959 0.056 0.061 1960 0.026 0.022 1961 0.061 0.051 1962 0.033 0.026 1963 0.016 0.018 1964 0.075 0.050 1965 0.060 0.051 1966 0.020 0.022 1967 0.040 0.029 1968 0.034 0.025 1969 0.029 0.024 1970 0.047 0.028 RAM Engineering, Inc. RAM No. 20-024 POC #1 Bracket's Reserve Stormwater Site Plan Report Page C-12 1971 0.062 0.031 1972 0.112 0.078 1973 0.055 0.044 1974 0.045 0.034 1975 0.076 0.043 1976 0.048 0.036 1977 0.021 0.020 1978 0.059 0.059 1979 0.025 0.026 1980 0.037 0.032 1981 0.031 0.032 1982 0.024 0.023 1983 0.049 0.033 1984 0.025 0.029 1985 0.037 0.032 1986 0.028 0.022 1987 0.058 0.035 1988 0.036 0.023 1989 0.030 0.021 1990 0.035 0.024 1991 0.029 0.031 1992 0.040 0.033 1993 0.034 0.031 1994 0.056 0.026 1995 0.018 0.022 1996 0.068 0.059 1997 0.034 0.024 1998 0.036 0.028 1999 0.027 0.026 2000 0.030 0.028 2001 0.028 0.027 2002 0.070 0.041 2003 0.036 0.027 2004 0.042 0.029 2005 0.067 0.054 2006 0.027 0.024 2007 0.030 0.031 2008 0.032 0.027 2009 0.026 0.024 2010 0.024 0.027 2011 0.024 0.023 2012 0.036 0.026 2013 0.029 0.026 2014 0.025 0.021 2015 0.101 0.051 2016 0.019 0.023 2017 0.052 0.037 2018 0.084 0.098 2019 0.104 0.054 2020 0.047 0.032 2021 0.047 0.033 2022 0.033 0.031 2023 0.038 0.038 2024 0.108 0.050 2025 0.031 0.030 2026 0.047 0.031 2027 0.030 0.032 2028 0.013 0.016 2029 0.034 0.026 2030 0.064 0.035 2031 0.021 0.016 2032 0.023 0.023 2033 0.020 0.021 2034 0.025 0.019 2035 0.066 0.066 2036 0.046 0.028 2037 0.025 0.028 2038 0.050 0.028 2039 0.041 0.041 2040 0.023 0.024 2041 0.022 0.024 2042 0.081 0.050 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-13 2043 0.040 0.030 2044 0.041 0.031 2045 0.033 0.024 2046 0.036 0.047 2047 0.027 0.023 2048 0.029 0.022 2049 0.037 0.031 2050 0.027 0.023 2051 0.042 0.035 2052 0.022 0.025 2053 0.034 0.033 2054 0.075 0.042 2055 0.024 0.024 2056 0.031 0.031 2057 0.021 0.021 2058 0.027 0.028 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1176 0.1066 2 0.1122 0.0976 3 0.1076 0.0779 4 0.1040 0.0655 5 0.1010 0.0632 6 0.0964 0.0611 7 0.0836 0.0608 8 0.0833 0.0592 9 0.0812 0.0585 10 0.0791 0.0544 11 0.0763 0.0542 12 0.0762 0.0537 13 0.0753 0.0514 14 0.0745 0.0513 15 0.0741 0.0511 16 0.0700 0.0509 17 0.0675 0.0503 18 0.0666 0.0500 19 0.0658 0.0500 20 0.0643 0.0471 21 0.0618 0.0454 22 0.0606 0.0439 23 0.0601 0.0436 24 0.0599 0.0432 25 0.0591 0.0425 26 0.0590 0.0418 27 0.0579 0.0412 28 0.0578 0.0409 29 0.0559 0.0384 30 0.0557 0.0378 31 0.0546 0.0373 32 0.0545 0.0373 33 0.0540 0.0371 34 0.0536 0.0366 35 0.0520 0.0364 36 0.0504 0.0355 37 0.0501 0.0354 38 0.0494 0.0353 39 0.0493 0.0348 40 0.0477 0.0336 41 0.0472 0.0335 42 0.0470 0.0334 43 0.0470 0.0331 44 0.0469 0.0330 45 0.0459 0.0330 46 0.0446 0.0327 47 0.0436 0.0323 48 0.0426 0.0322 49 0.0423 0.0319 50 0.0421 0.0319 51 0.0420 0.0318 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-14 52 0.0412 0.0315 53 0.0411 0.0315 54 0.0403 0.0314 55 0.0402 0.0312 56 0.0402 0.0311 57 0.0390 0.0310 58 0.0385 0.0309 59 0.0379 0.0308 60 0.0377 0.0308 61 0.0375 0.0308 62 0.0375 0.0307 63 0.0373 0.0305 64 0.0372 0.0304 65 0.0370 0.0302 66 0.0368 0.0298 67 0.0365 0.0295 68 0.0364 0.0293 69 0.0364 0.0289 70 0.0364 0.0289 71 0.0362 0.0288 72 0.0362 0.0286 73 0.0356 0.0286 74 0.0355 0.0285 75 0.0347 0.0284 76 0.0347 0.0284 77 0.0344 0.0283 78 0.0341 0.0283 79 0.0340 0.0282 80 0.0339 0.0280 81 0.0338 0.0280 82 0.0338 0.0278 83 0.0337 0.0278 84 0.0336 0.0278 85 0.0335 0.0277 86 0.0334 0.0275 87 0.0330 0.0272 88 0.0328 0.0272 89 0.0327 0.0271 90 0.0325 0.0270 91 0.0322 0.0268 92 0.0320 0.0266 93 0.0318 0.0265 94 0.0316 0.0263 95 0.0312 0.0263 96 0.0311 0.0261 97 0.0307 0.0260 98 0.0306 0.0260 99 0.0306 0.0260 100 0.0305 0.0260 101 0.0302 0.0258 102 0.0301 0.0258 103 0.0300 0.0257 104 0.0297 0.0256 105 0.0296 0.0256 106 0.0295 0.0252 107 0.0295 0.0251 108 0.0294 0.0251 109 0.0292 0.0251 110 0.0292 0.0250 111 0.0289 0.0250 112 0.0288 0.0248 113 0.0286 0.0245 114 0.0285 0.0243 115 0.0283 0.0242 116 0.0281 0.0241 117 0.0278 0.0239 118 0.0273 0.0238 119 0.0272 0.0237 120 0.0269 0.0237 121 0.0268 0.0237 122 0.0266 0.0236 123 0.0265 0.0236 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-15 124 0.0262 0.0235 125 0.0260 0.0233 126 0.0254 0.0232 127 0.0250 0.0231 128 0.0249 0.0231 129 0.0249 0.0230 130 0.0249 0.0230 131 0.0246 0.0229 132 0.0244 0.0227 133 0.0240 0.0227 134 0.0238 0.0226 135 0.0237 0.0225 136 0.0236 0.0225 137 0.0232 0.0224 138 0.0230 0.0223 139 0.0229 0.0222 140 0.0225 0.0221 141 0.0224 0.0219 142 0.0223 0.0219 143 0.0211 0.0218 144 0.0210 0.0215 145 0.0208 0.0214 146 0.0208 0.0212 147 0.0204 0.0205 148 0.0204 0.0205 149 0.0200 0.0198 150 0.0199 0.0197 151 0.0196 0.0196 152 0.0195 0.0192 153 0.0185 0.0190 154 0.0184 0.0180 155 0.0183 0.0176 156 0.0160 0.0161 157 0.0127 0.0158 Stream Protection Duration POC #1 The Facility PASSED Analys 61 10 501 POC 1 Redeveloped litigated flow n m U 0.08 V 0.06 0 0.04 0.02 1 CE-5 1 CE-4 10E-3 1 CE-2 10E-1 9 1 10 100 Percent Time E--li"o Sheam Protection Duration LID Duiation_j Flow Frequency I Water Quality I Hydrogiaph Welland Input VolurneTj LID Report I Recharge Duration I Recharge Predeveloped I Recharge Mitigated Analyzedatasets Compact WDM I Delete Selected r Monthly FF F:-:1 i Predeveloped flowMili ate flow Evap POC 1 POC 2 Flood Frequency Method All Dalasets Fbw Slag, Precip (- Log Pearson Type III 17B J. r Weibull (" Cunnane r Gringoden RAM Engineering, Inc. RAM No. 20-024 Facility PASSED lor(cfs) Predev Mit Percentage Pass/Pail .0177 27888 27283 97 Pass .0186 24574 22532 91 Pass .0194 21701 18860 86 Pass .0203 19224 15722 81 Pass .0211 17033 13008 76 Pass .0219 15139 10542 69 Pass .0228 13515 8511 62 Pass .0236 12084 6567 54 Pass .0245 10878 5015 46 Pass .0253 9843 4322 43 Pass .0261 8880 3837 43 Pass .0270 8043 3480 43 Pass .0278 7305 3159 43 Pass .0287 6650 2881 43 Pass .0295 6094 2662 43 Pass .0303 5615 2484 44 Pass . 0312 5130 2316 45 Pass . 0320 4666 2138 45 Pass .0328 4261 1995 46 Pass .0337 3924 1898 48 Pass .0345 3622 1786 49 Pass .0354 3382 1679 49 Pass .0362 3146 1591 50 Pass .0370 2942 1503 51 Pass .0379 2717 1443 53 Pass .0387 2548 1388 54 Pass .0396 2368 1335 56 Pass .0404 2203 1277 57 Pass .0412 2059 1230 59 Pass .0421 1880 1162 61 Pass .0429 1738 1086 62 Pass .0438 1605 1018 63 Pass .0446 1505 957 63 Pass .0454 1401 887 63 Pass Bracket's Reserve Stormwater Site Plan Report Page C-16 The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0177 27888 27283 97 Pass 0.0186 24574 22532 91 Pass 0.0194 21701 18860 86 Pass 0.0203 19224 15722 81 Pass 0.0211 17033 13008 76 Pass 0.0219 15139 10542 69 Pass 0.0228 13515 8511 62 Pass 0.0236 12084 6567 54 Pass 0.0245 10878 5015 46 Pass 0.0253 9843 4322 43 Pass 0.0261 8880 3837 43 Pass 0.0270 8043 3480 43 Pass 0.0278 7305 3159 43 Pass 0.0287 6650 2881 43 Pass 0.0295 6094 2662 43 Pass 0.0303 5615 2484 44 Pass 0.0312 5130 2316 45 Pass 0.0320 4666 2138 45 Pass 0.0328 4261 1995 46 Pass 0.0337 3924 1898 48 Pass 0.0345 3622 1786 49 Pass 0.0354 3382 1679 49 Pass 0.0362 3146 1591 50 Pass 0.0370 2942 1503 51 Pass 0.0379 2717 1443 53 Pass 0.0387 2548 1388 54 Pass 0.0396 2368 1335 56 Pass 0.0404 2203 1277 57 Pass 0.0412 2059 1230 59 Pass 0.0421 1880 1162 61 Pass 0.0429 1738 1086 62 Pass 0.0438 1605 1018 63 Pass 0.0446 1505 957 63 Pass 0.0454 1401 887 63 Pass 0.0463 1299 817 62 Pass 0.0471 1201 751 62 Pass 0.0480 1111 688 61 Pass 0.0488 1039 639 61 Pass 0.0496 949 594 62 Pass 0.0505 870 550 63 Pass 0.0513 814 517 63 Pass 0.0522 735 479 65 Pass 0.0530 666 452 67 Pass 0.0538 600 421 70 Pass 0.0547 535 370 69 Pass 0.0555 486 330 67 Pass 0.0564 436 293 67 Pass 0.0572 388 251 64 Pass 0.0580 358 215 60 Pass 0.0589 318 189 59 Pass 0.0597 280 170 60 Pass 0.0606 260 158 60 Pass 0.0614 235 143 60 Pass 0.0622 214 133 62 Pass 0.0631 195 121 62 Pass 0.0639 177 112 63 Pass 0.0648 161 104 64 Pass 0.0656 138 97 70 Pass 0.0664 125 93 74 Pass 0.0673 113 86 76 Pass 0.0681 102 80 78 Pass 0.0690 95 75 78 Pass 0.0698 90 70 77 Pass 0.0706 81 62 76 Pass 0.0715 73 44 60 Pass 0.0723 70 35 50 Pass 0.0732 63 31 49 Pass 0.0740 59 29 49 Pass 0.0748 54 28 51 Pass RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-17 0.0757 50 25 50 Pass 0.0765 47 21 44 Pass 0.0773 42 20 47 Pass 0.0782 41 19 46 Pass 0.0790 41 19 46 Pass 0.0799 37 18 48 Pass 0.0807 36 16 44 Pass 0.0815 34 16 47 Pass 0.0824 34 16 47 Pass 0.0832 33 16 48 Pass 0.0841 29 16 55 Pass 0.0849 27 15 55 Pass 0.0857 24 15 62 Pass 0.0866 21 15 71 Pass 0.0874 19 14 73 Pass 0.0883 15 14 93 Pass 0.0891 14 13 92 Pass 0.0899 13 13 100 Pass 0.0908 13 11 84 Pass 0.0916 13 11 84 Pass 0.0925 13 10 76 Pass 0.0933 13 10 76 Pass 0.0941 13 10 76 Pass 0.0950 11 10 90 Pass 0.0958 11 9 81 Pass 0.0967 9 6 66 Pass 0.0975 9 5 55 Pass 0.0983 7 4 57 Pass 0.0992 5 3 60 Pass 0.1000 5 3 60 Pass 0.1009 5 3 60 Pass Water Quality 3MP Flow and Volume for POC #1 On-line facility volume: 0.0258 acre-feet On-line facility target flow: 0.0133 cfs. Adjusted for 15 min: 0.0133 cfs. Off-line facility target flow: 0.0089 cfs. Adjusted for 15 min: 0.0089 cfs. LID Report LS • LID Repoit POC 1 LID Technique Usedfor Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Vault 1 POC ❑ 461.28 13 0.00 Total Volume Infiltrated 461.28 0.00 0.00 0.00 0.00 0% No Treat Credit Duration Compliance with LID Analysis Standard 8% of 2-yr to 50% of Result= 2 yr Failed No changes have been made. This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-18 South Basin Water Quality. The proposed developments project will create about 50,050 sf of impervious surface, of which approximately 17,200 sf will be pollution generation impervious/hard surfaces; road and driveway areas all in the south basin. Due to the fact the pollution generation hard surfaces exceed 5,000 sf, basic water quality will be provided. A water quality treatment media filter catch basin installed downstream of the onsite detention system to provide the required basic water quality treatment (MR #6). Below are the design sizing calculations for each treatment facility. Media Filter Catch Basins: An Oldcastle Stormwater Solutions Perk FilterT"" located online and downstream of the detention vault will provide basic water quality treatment for the project. The Perk FilterT"' system has Washington State DOE approval as a general use level designation (GULD) for basic water quality. The sizing (number of treatment cartridges) of the filter system is based on the peak 2-year mitigated flow rate due to the fact the filter system is placed downstream of the detention system. The below manufacture sizing criteria indicates that a two (2)— 12" cartridge system within in a 60" manhole Perk Filter has a treatment capacity of 0.03 cfs and will adequately treat the 2-year mitigated release rate of online design rate of 0.029 cfs (see South Basin WWHM calculations above). RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-19 Q 0 T? 75 LL a_ y INL 018.00" Mi PIPE SI: SEE NOTE IN THIS VIEW FOR CLARITY. FIELD POURED CONCRETE COLLAR - REQUIRED, BY OTHERS. SEE NOTE 2. INLET, 018.00" MAX. PIPE SIZE. SEE NOTE 3. DRAIN DOWN TUBE. j- 33' [4.00'I J Washington GULD* �1 TLET, 8.00" MAX. 'E SIZE. E NOTE 3. 036.00" BOLTED & GASKETED ACCESS COVER. FIELD POURED CONCRETE COLLAR REQUIRED, BY OTHERS. 05.00' [60.00' - SECTION A -A MINIMUM DEPTH OUTLET, 018.00" MAX. PIPE SIZE. SEE NOTE 3. Minimum Depth PIPE SIZE 06.00" 08.00" 010.001, 012.00" 015.001, 018.00" CARTRIDGE TYPE MINIMUM DEPTH RIM TO OUTLET MINIMUM DEPTH RIM TO OUTLET MINIMUM DEPTH RIM TO OUTLET MINIMUM DEPTH RIM TO OUTLET MINIMUM DEPTH RIM TO OUTLET MINIMUM DEPTH RIM TO OUTLET 12" 4.08' [49.001 4.08' [49.001 4.33' [62.00-1 4.58' [55.009 4.83' [58.00"] 5.08' [61.001 18" 4.83'[58.001 4.83'[58.001 5.08'[61.00'1 5.33'[64.001 5.58'[67.001 5.83'[70.001 12" + 12" 5.58' [67.00'1 5.83' [70.001 6.08' [73.00'1 6.33' [76.001 6.58' [79.00"] 6.83' [82.00"] 12" + 18" 6.08'[73.00'1 6.33'[76.00"] 6.58'[79.00'1 6.83'[82.00"] 7.08'[85.001 7.33'[88.00"] TREATME 060.00" PERK FILTER MANHOLE FLOW RATES, TOTAL FLOW CAPACITIES & MAXIMUM HEAD LOSS CARTRIDGE STACK QUANTITY CARTRIDGE STACK CONFIGURATION 12" 18" 12" & 12" 12" & 18" TREATMENT FLOW RATE (GPM / CFS) TOTAL FLOW CAPACITY (CFS) TREATMENT FLOW RATE (GPM / CFS) TOTAL FLOW CAPACITY (CFS) TREATMENT FLOW RATE (GPM / CFS) TOTALFLOW CAPACITY (CFS) TREATMENT FLOW RATE (GPM / CFS) TOTALFLOW CAPACITY (CFS) 1 BA10015 247 10.2/ 0.022 3.05 13.6 / 0.03 3.45 17 / 0.037 3.62 2 13.6 / 0.03 2.47 0.4 / 0.045 3.05 27.2 / 0.06 3A5 34 / 0.075 3.62 3 20.4 / 0.045 . 7 30.6 / 0.068 3.05 40.8 / 0.09 3.45 51 / 0.113 3.62 MAXIMUM HEAD LOSS 1.7 FEET 2.3 FEET 2.9 FEET 3.5 FEET Perk FilterTM 060.00" Manhole (- ® Washington State GULD Media One to Three Cartridges / Stacks Filtration RAM Engineering, Inc. RAM No. 20-024 `Oldcastle® Stormwater Solutions 7921 Southpark Plaza, Suite 200 1 Littleton, CO 180120 1 Ph: 800.579.8819 1 oldcastlestormwater.com HIS DOCUMENT IS THE PROPERTY OF OLOCASTLE PRECAST, INC. IT IS SUBMITTED FOR REFERENCE PURPOSES ONLY ANDSHALL NOT BE ANY WAY INJURIOUS TO THE INTERESTS OF SAIDCOMPANY. COPYRII OLDCASTLE PRECAST, INC. ALL RIGHTS RESERVED. DRAWING N0. RE" EC0 ECO-013215 DATE PF-MH-60-WA NR ISM 4 27 ISM 4/27/15 SHEET 2 OF 2 Bracket's Reserve Stormwater Site Plan Report Page C-20 North Basin WWHM Input/output Data: Project Name: 20-024 Brackets Reserve- north Site Name: Brackets Reserve Site Address: 20-024 City Report Date: 10/1/2021 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2019/09/13 Version : 4.2.17 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod 1.262 Pervious Total 1.262 Impervious Land Use acre Impervious Total 0 Basin Total 1.262 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No Groundwater: No Pervious Land Use acre C, Forest, Mod .699 Pervious Total 0.699 Impervious Land Use acre Impervious Total 0 Basin Total 0.699 Element Flows To: Surface Interflow RAM Engineering, Inc. RAM No. 20-024 Groundwater Groundwater Bracket's Reserve Stormwater Site Plan Report Page C-21 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.262 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.699 Total Impervious Area:O Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.021414 5 year 0.033234 10 year 0.039647 25 year 0.046168 50 year 0.050041 100 year 0.053225 Flow Frequency Return Periods for Mitigated Return Period Flow(cfs) 2 year 0.011861 5 year 0.018408 10 year 0.02196 25 year 0.025572 50 year 0.027717 100 year 0.02948 Analysis ® 0.1 001 'o LL 0.001 0.0001 POC #1 Cumulative Probability 0.1 �xxxxxx x x SAW �{ 0.01 + x F5001 +x 0.0001 0.5 1 2 5 10 20 30 50 70 80 90 95 98 9999.51 Stream Protection Duration I LID Duration Flow Frequency L Water Quality I Hydrograph Wetland Input Volumes I LID Report Recharge Duration I Recharge Predeveloped I Recharge Mitigated Analyze datasets Com r MonthlyFF pact WDM � Delete Selected 501 POC 1 Redeveloped flow 801 POC 1 Mitigated flow ANDatasets I Flow Stage Precip Evap POC1 Flood Frequency Method F Log Pearson Type III 178 f Weibull l Cunnane l' Gringorten RAM Engineering, Inc. RAM No. 20-024 L Flov Frequency Flov(efs) Predeveloped Mitigated 2 Year = 0.0214 0.0119 5 Year = 0.0332 0.0184 10 Year = 0.0396 0.0220 25 Year = 0.0462 0.0256 50 Year = 0.0500 0.0277 100 Year = 0.0532 0.0295 Annual Peaks 1902 0.0299 0.0165 1903 0.0104 0.0058 1904 0.0192 0.0106 1905 0.0121 0.0067 1906 0.0049 0.0027 1907 0.0334 0.0185 1908 0.0212 0.0117 1909 0.0230 0.0128 1910 0.0365 0.0202 1911 0.0190 0.0106 1912 0.0646 0.0358 1913 0.0320 0.0177 1914 0.0075 0.0042 1915 0.0109 0.0060 1916 0.0174 0.0096 1917 0.0084 0.0047 1918 0.0205 0.0113 1919 0.0152 0.0084 1920 0.0196 0.0109 1921 0.0208 0.0115 1922 0.0235 0.0130 1923 0.0153 0.0085 1924 0.0103 0.0057 1925 0.0104 0.0057 1926 0.0186 0.0103 1927 0.0240 0.0133 1928 0.0158 0.0087 1929 0.0338 0.0187 Bracket's Reserve Stormwater Site Plan Report Page C-22 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1902 0.030 0.017 1903 0.010 0.006 1904 0.019 0.011 1905 0.012 0.007 1906 0.005 0.003 1907 0.033 0.018 1908 0.021 0.012 1909 0.023 0.013 1910 0.036 0.020 1911 0.019 0.011 1912 0.065 0.036 1913 0.032 0.018 1914 0.007 0.004 1915 0.011 0.006 1916 0.017 0.010 1917 0.008 0.005 1918 0.020 0.011 1919 0.015 0.008 1920 0.020 0.011 1921 0.021 0.012 1922 0.023 0.013 1923 0.015 0.009 1924 0.010 0.006 1925 0.010 0.006 1926 0.019 0.010 1927 0.024 0.013 1928 0.016 0.009 1929 0.034 0.019 1930 0.020 0.011 1931 0.020 0.011 1932 0.014 0.008 1933 0.018 0.010 1934 0.047 0.026 1935 0.017 0.010 1936 0.028 0.015 1937 0.023 0.013 1938 0.023 0.013 1939 0.001 0.001 1940 0.019 0.010 1941 0.019 0.010 1942 0.028 0.015 1943 0.009 0.005 1944 0.024 0.013 1945 0.021 0.011 1946 0.018 0.010 1947 0.013 0.007 1948 0.044 0.024 1949 0.036 0.020 1950 0.019 0.011 1951 0.023 0.013 1952 0.063 0.035 1953 0.056 0.031 1954 0.017 0.010 1955 0.015 0.008 1956 0.010 0.006 1957 0.025 0.014 1958 0.059 0.033 1959 0.036 0.020 1960 0.013 0.007 1961 0.037 0.020 1962 0.019 0.010 1963 0.009 0.005 1964 0.017 0.009 1965 0.043 0.024 RAM Engineering, Inc. RAM No. 20-024 POC #1 Bracket's Reserve Stormwater Site Plan Report Page C-23 1966 0.008 0.004 1967 0.017 0.009 1968 0.023 0.013 1969 0.015 0.009 1970 0.024 0.013 1971 0.046 0.025 1972 0.030 0.017 1973 0.034 0.019 1974 0.019 0.011 1975 0.049 0.027 1976 0.022 0.012 1977 0.014 0.008 1978 0.042 0.023 1979 0.011 0.006 1980 0.021 0.012 1981 0.021 0.012 1982 0.014 0.008 1983 0.034 0.019 1984 0.009 0.005 1985 0.021 0.011 1986 0.016 0.009 1987 0.035 0.019 1988 0.026 0.014 1989 0.020 0.011 1990 0.026 0.015 1991 0.019 0.011 1992 0.030 0.017 1993 0.025 0.014 1994 0.044 0.024 1995 0.010 0.006 1996 0.049 0.027 1997 0.023 0.013 1998 0.022 0.012 1999 0.001 0.001 2000 0.016 0.009 2001 0.012 0.006 2002 0.030 0.017 2003 0.023 0.013 2004 0.024 0.013 2005 0.029 0.016 2006 0.015 0.008 2007 0.017 0.009 2008 0.022 0.012 2009 0.014 0.008 2010 0.011 0.006 2011 0.014 0.008 2012 0.019 0.011 2013 0.016 0.009 2014 0.011 0.006 2015 0.042 0.023 2016 0.006 0.003 2017 0.035 0.019 2018 0.059 0.033 2019 0.065 0.036 2020 0.019 0.010 2021 0.029 0.016 2022 0.010 0.006 2023 0.023 0.013 2024 0.050 0.028 2025 0.019 0.010 2026 0.033 0.018 2027 0.015 0.008 2028 0.007 0.004 2029 0.024 0.013 2030 0.046 0.026 2031 0.013 0.007 2032 0.010 0.006 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-24 2033 0.012 0.006 2034 0.013 0.007 2035 0.052 0.029 2036 0.027 0.015 2037 0.005 0.003 2038 0.027 0.015 2039 0.002 0.001 2040 0.010 0.005 2041 0.015 0.008 2042 0.054 0.030 2043 0.024 0.013 2044 0.033 0.018 2045 0.021 0.011 2046 0.024 0.014 2047 0.015 0.008 2048 0.021 0.012 2049 0.019 0.011 2050 0.013 0.007 2051 0.021 0.012 2052 0.012 0.007 2053 0.022 0.012 2054 0.029 0.016 2055 0.009 0.005 2056 0.008 0.005 2057 0.014 0.008 2058 0.017 0.009 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0648 0.0359 2 0.0646 0.0358 3 0.0629 0.0348 4 0.0594 0.0329 5 0.0587 0.0325 6 0.0557 0.0309 7 0.0541 0.0300 8 0.0520 0.0288 9 0.0503 0.0279 10 0.0491 0.0272 11 0.0485 0.0269 12 0.0471 0.0261 13 0.0463 0.0256 14 0.0459 0.0254 15 0.0438 0.0242 16 0.0437 0.0242 17 0.0432 0.0239 18 0.0424 0.0235 19 0.0423 0.0235 20 0.0366 0.0203 21 0.0365 0.0202 22 0.0360 0.0199 23 0.0357 0.0198 24 0.0348 0.0193 25 0.0346 0.0192 26 0.0344 0.0191 27 0.0342 0.0190 28 0.0338 0.0187 29 0.0334 0.0185 30 0.0330 0.0183 31 0.0329 0.0182 32 0.0320 0.0177 33 0.0302 0.0167 34 0.0300 0.0166 35 0.0299 0.0165 36 0.0298 0.0165 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-25 37 0.0295 0.0163 38 0.0289 0.0160 39 0.0288 0.0160 40 0.0279 0.0155 41 0.0279 0.0154 42 0.0270 0.0149 43 0.0269 0.0149 44 0.0263 0.0145 45 0.0258 0.0143 46 0.0248 0.0138 47 0.0246 0.0136 48 0.0244 0.0135 49 0.0243 0.0135 50 0.0241 0.0133 51 0.0240 0.0133 52 0.0237 0.0131 53 0.0237 0.0131 54 0.0235 0.0130 55 0.0235 0.0130 56 0.0233 0.0129 57 0.0233 0.0129 58 0.0232 0.0128 59 0.0230 0.0128 60 0.0230 0.0127 61 0.0230 0.0127 62 0.0227 0.0126 63 0.0226 0.0125 64 0.0220 0.0122 65 0.0218 0.0121 66 0.0217 0.0120 67 0.0216 0.0120 68 0.0214 0.0119 69 0.0212 0.0117 70 0.0211 0.0117 71 0.0208 0.0115 72 0.0208 0.0115 73 0.0208 0.0115 74 0.0207 0.0115 75 0.0206 0.0114 76 0.0205 0.0114 77 0.0205 0.0113 78 0.0203 0.0112 79 0.0202 0.0112 80 0.0200 0.0111 81 0.0196 0.0109 82 0.0195 0.0108 83 0.0195 0.0108 84 0.0195 0.0108 85 0.0193 0.0107 86 0.0193 0.0107 87 0.0192 0.0106 88 0.0190 0.0106 89 0.0189 0.0105 90 0.0189 0.0105 91 0.0188 0.0104 92 0.0187 0.0103 93 0.0186 0.0103 94 0.0186 0.0103 95 0.0184 0.0102 96 0.0176 0.0097 97 0.0174 0.0096 98 0.0174 0.0096 99 0.0173 0.0096 100 0.0170 0.0094 101 0.0170 0.0094 102 0.0169 0.0093 103 0.0168 0.0093 RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-26 104 0.0163 0.0090 105 0.0161 0.0089 106 0.0160 0.0089 107 0.0158 0.0087 108 0.0154 0.0086 109 0.0153 0.0085 110 0.0153 0.0085 ill 0.0152 0.0084 112 0.0152 0.0084 113 0.0151 0.0083 114 0.0149 0.0083 115 0.0145 0.0080 116 0.0143 0.0079 117 0.0143 0.0079 118 0.0143 0.0079 119 0.0140 0.0077 120 0.0140 0.0077 121 0.0136 0.0076 122 0.0131 0.0073 123 0.0129 0.0072 124 0.0129 0.0071 125 0.0129 0.0071 126 0.0126 0.0070 127 0.0124 0.0069 128 0.0121 0.0067 129 0.0117 0.0065 130 0.0115 0.0064 131 0.0114 0.0063 132 0.0111 0.0062 133 0.0109 0.0060 134 0.0107 0.0060 135 0.0104 0.0058 136 0.0104 0.0058 137 0.0104 0.0057 138 0.0103 0.0057 139 0.0103 0.0057 140 0.0103 0.0057 141 0.0099 0.0055 142 0.0098 0.0054 143 0.0094 0.0052 144 0.0091 0.0050 145 0.0089 0.0049 146 0.0087 0.0048 147 0.0084 0.0047 148 0.0083 0.0046 149 0.0077 0.0043 150 0.0075 0.0042 151 0.0071 0.0040 152 0.0059 0.0033 153 0.0052 0.0029 154 0.0049 0.0027 155 0.0024 0.0013 156 0.0014 0.0008 157 0.0011 0.0006 Stream Protection Duration POC #1 The Facility PASSED RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-27 ® 0.01 n p 0.01 U v 0.01 0 J 0.00 0.00 1 Percent Time E--e 1i-O Stream Protection Duration I LID Duration I Flow Frequency I Water Analyze datasets Compact WDM Delete Selected I r Mon1Wy FF 501 POC 801 POC All Datasets I Flow j Stage J_E!!Ripj Evap POC 1 Flood Frequency Method F Log Pearson Type III 17B r' Weibull r' Cunnane r Gringorlen The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0107 53344 11274 21 Pass 0.0111 49061 10118 20 Pass 0.0115 45147 9171 20 Pass 0.0119 41838 8247 19 Pass 0.0123 38678 7432 19 Pass 0.0127 35827 6771 18 Pass 0.0131 33234 6166 18 Pass 0.0135 30949 5670 18 Pass 0.0139 28885 5186 17 Pass 0.0143 26947 4773 17 Pass 0.0147 25163 4389 17 Pass 0.0151 23457 4013 17 Pass 0.0155 21882 3714 16 Pass 0.0159 20336 3470 17 Pass 0.0163 18948 3261 17 Pass 0.0167 17682 3074 17 Pass 0.0171 16510 2914 17 Pass 0.0175 15464 2743 17 Pass 0.0179 14478 2564 17 Pass 0.0183 13509 2391 17 Pass 0.0187 12607 2200 17 Pass 0.0191 11792 2023 17 Pass 0.0194 11071 1903 17 Pass 0.0198 10427 1777 17 Pass 0.0202 9837 1663 16 Pass 0.0206 9326 1549 16 Pass 0.0210 8792 1444 16 Pass 0.0214 8296 1334 16 Pass RAM Engineering, Inc. RAM No. 20-024 Facility PASSED low(cfs) Predev Mit Percentage Pass/Fail .0017 584634 360359 61 Pass .0018 563714 342688 60 Pass .0019 544172 325952 59 Pass .0020 525565 310318 59 Pass .0021 508004 295510 58 Pass .0022 491213 281747 57 Pass .0023 475359 268810 56 Pass .0023 460330 256479 SS Pa9s .0024 446072 244919 54 Pass .0025 432420 234019 54 Pass .0026 419538 223834 53 Pass .0027 407262 213925 52 Pass .0028 395316 204622 51 Pass .0029 383865 195814 51 Pass .0030 372965 187666 50 Pass .0031 362396 179794 49 Pass .0032 352266 172197 48 Pass .0033 342523 165096 48 Pass .0033 333054 158269 47 Pa 99 .0034 324081 151774 46 Pass .0035 315383 145773 46 Pass .0036 307015 139883 45 Pass .0037 298813 134157 44 Pass .0038 290885 128818 44 Pass .0039 283344 123753 43 Pass .0040 276077 118964 43 Pass .0041 268975 114229 42 Pass .0042 262094 109880 41 Pass .0043 255378 105696 41 Pass .0043 248827 101623 40 Pass .0044 242551 97714 40 Pass .0045 236496 93971 39 Pass .0046 230716 90448 39 Pass .0047 225100 87034 38 Pass Bracket's Reserve Stormwater Site Plan Report Page C-28 0.0218 7850 1222 15 Pass 0.0222 7404 1144 15 Pass 0.0226 7041 1052 14 Pass 0.0230 6667 967 14 Pass 0.0234 6342 900 14 Pass 0.0238 6045 820 13 Pass 0.0242 5747 750 13 Pass 0.0246 5474 674 12 Pass 0.0250 5217 601 11 Pass 0.0254 4991 531 10 Pass 0.0258 4759 448 9 Pass 0.0262 4538 387 8 Pass 0.0266 4337 339 7 Pass 0.0270 4125 291 7 Pass 0.0274 3940 254 6 Pass 0.0278 3772 226 5 Pass 0.0282 3631 203 5 Pass 0.0286 3493 173 4 Pass 0.0290 3368 143 4 Pass 0.0294 3255 119 3 Pass 0.0298 3146 99 3 Pass 0.0302 3054 85 2 Pass 0.0306 2965 75 2 Pass 0.0310 2877 64 2 Pass 0.0314 2781 54 1 Pass 0.0318 2681 43 1 Pass 0.0322 2586 33 1 Pass 0.0326 2493 18 0 Pass 0.0330 2391 13 0 Pass 0.0334 2278 10 0 Pass 0.0338 2181 6 0 Pass 0.0341 2080 3 0 Pass 0.0345 1997 3 0 Pass 0.0349 1928 2 0 Pass 0.0353 1864 2 0 Pass 0.0357 1790 2 0 Pass 0.0361 1718 0 0 Pass 0.0365 1664 0 0 Pass 0.0369 1596 0 0 Pass 0.0373 1537 0 0 Pass 0.0377 1480 0 0 Pass 0.0381 1417 0 0 Pass 0.0385 1361 0 0 Pass 0.0389 1298 0 0 Pass 0.0393 1242 0 0 Pass 0.0397 1188 0 0 Pass 0.0401 1147 0 0 Pass 0.0405 1100 0 0 Pass 0.0409 1045 0 0 Pass 0.0413 1000 0 0 Pass 0.0417 954 0 0 Pass 0.0421 916 0 0 Pass 0.0425 877 0 0 Pass 0.0429 832 0 0 Pass 0.0433 788 0 0 Pass 0.0437 754 0 0 Pass 0.0441 710 0 0 Pass 0.0445 666 0 0 Pass 0.0449 627 0 0 Pass 0.0453 595 0 0 Pass 0.0457 554 0 0 Pass 0.0461 516 0 0 Pass 0.0465 461 0 0 Pass 0.0469 421 0 0 Pass 0.0473 392 0 0 Pass 0.0477 360 0 0 Pass 0.0481 334 0 0 Pass RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-29 0.0485 306 0 0 Pass 0.0488 286 0 0 Pass 0.0492 264 0 0 Pass 0.0496 247 0 0 Pass 0.0500 233 0 0 Pass Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.0329 acre-feet On-line facility target flow: 0.0184 cfs. Adjusted for 15 min: 0.0184 cfs. Off-line facility target flow: 0.0102 cfs. Adjusted for 15 min: 0.0102 cfs. LID Report i.POC.1^ I LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Total Volume Infiltrated 0.00 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Duration Standard 8% of 2-yr to 50% of Analysis 2-yr Result = Passed Perind and Impind Changes No changes have been made. This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. RAM Engineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page C-30 D. Additional Reports and Studies : Geotechnical Engineering Report Prepared by: Earth Solutions NW, LLC Update: June 2021 (Provided under separate cover) Critical Area Reconnaissance Report Prepared by: Wetland Resources Environmental Consulting Update: October 11, 2021 (Provided under separate cover) RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page D-1 E. CONSTRUCTION SWPPP REQUIREMENTS: The project will require grading to construct the proposed building and utilities (including the stormwater control facilities). Standard erosion control measures are proposed to be used during construction. The primary erosion and sediment control BMP during construction will be proper soil stabilization methods. Exposed soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrops, flowing water, and wind. Applicable practices include, but not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics, matting, the early application of gravel base on areas to be paved, and dust control. The contractor shall select a soil stabilization method best suited for the particular situation. Stock piles must be stabilized and protected with sediment trapping measures. In addition, site containment of exposed soils shall be sustained by using silt fence barriers along the down -slope boundaries of the site's disturbance areas. See the site development plan for details. Construction Stormwater Pollution Prevention Plan (SWPPP): The following is a summary of the site's erosion control measures that evaluates the typical DOE 13 elements of a SWPPP: Element 1: Mark Clearing Limits: Clearing limits have been delineated on the engineering site development plans. Element 2: Establish Construction Access: A construction access has been delineated on the engineering site development plans. Element 3: Control Flow Rates: During construction silt fencing will provide attenuation of site runoff and upon project completion and stabilization (established lawns and landscape of exposed soils). Element 4: Install Sediment Controls: Filter fabric fence has been delineated and detailed on the engineering site development plans. At a minimum, silt fence will be installed along the down gradient perimeter of the disturbed area that will receive sediment -laden runoff. Element 5: Stabilize Soils: Soils will be stabilized per the TESC notes listed on the engineering site development plans. Element 6: Protect Slopes: Exposed slopes shall be stabilized per the TESC notes listed on the engineering site development plans. Element 7: Protect Drain Inlets: Drain inlet protection will be installed on all catch basins that will receive sediment -laden runoff. See the engineering site development plans for locations and detail. Element 8: Stabilize Channels and Outlets: This element is not applicable since there are no temporary channels or outlets proposed. Element 9: Control Pollutants: Pollutants shall be managed as described in the TESC notes listed on the engineering site development plans. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page E-1 Element 10: Control De -Watering: Highly turbid or contaminated de -watering water shall be handled separately from stormwater. The water from all de -watering systems for trenches and foundations shall be treated or disposed prior to discharging from the site. Element 11: Maintain BMPs: BMPs shall be maintained and removed at the end of the project as follows: i. All temporary and permanent erosion and sediment control BMPs shall be inspected, maintained and repaired in accordance with the Drainage Manual or as approved or required by the City to assure continued performance of their intended function in accordance with BMP specifications. ii. The applicant may remove temporary BMPs when they are no longer needed. iii. All temporary erosion and sediment control BMPs shall be removed within 30 days after construction is completed and the City has determined that the site is stabilized. Element 12: Manage the Project: The owner of the site is responsible for managing the installation and maintenance of the site BMPs. Element 13. Protect Low Impact Development BMPs: No LID stormwater BMPs are proposed. Conclusion: The total site disturbance area of the project is greater than one acre, thus a formal Notice of Intent construction stormwater application for NPDES coverage will be made to the Department of Ecology prior to the start of construction. The final site development construction plans will include specific grading and drainage improvement notes and details. With proper installation, maintenance and inspections of the proposed construction the project should have minimal impact to the surrounding environment. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page E-2 F. OPERATION AND MAINTENANCE GUIDELINES: These guidelines are intended to provide operation and maintenance instructions for the project's storm drainage control facilities. The owner is responsible for maintenance of storm drainage facilities within the property (private property owner system); the owner is not responsible for maintenance within the public right-of-way (City system). Private Property Owners: Private property owners are responsible for properly maintaining the stormwater infrastructure on their property to ensure it operates as designed. The City has developed an inspection program to ensure private property owners are properly maintaining their stormwater systems. City System: City crews perform maintenance activities on the entire storm drainage system, including inspection and cleaning of catch basins, street sweeping, emergency flooding response, creek maintenance, inspection and monitoring of private stormwater detention systems. Operation and Maintenance Requirements for private property owner system: This manual is not comprehensive; although it explains the intended operation of the various components of the drainage system, and suggests a routine of inspection and maintenance, it cannot anticipate every problem. Once a historical record of maintenance is established, it may be prudent to alter the routine. It is recommended that maintenance records be kept, and that the records be reviewed periodically. Concept of Operation: The drainage design is shown and described in the site development engineering plans and report. The approved site development plans and report should be retained by the owner and used as a reference to identify stormwater BMP facilities outlined in this section. Conveyance Systems. The design objective of the storm system is to convey the large storm events without the water surface exceeding the ground elevation. Frequent overtopping of the pipe system in an area might indicate a downstream blockage. Overtopping of the drain systems at the catch -basins is an indication that maintenance is required. Along the northerly boundary of the project, a culvert has been installed under the fill embankment of the cul-de-sac to prevent stormwater from ponding uphill (east) of the cul-de-sac. This culvert will need to be maintained by the homeowners of Brackets Reserve. This culvert shall be inspected regularly to make sure there are blockages, siltation and/or scouring at the intake or outlet of the culvert. The following pages outline standard general maintenance criteria for the project's drainage facilities For additional and updated maintenance information visit the Washington State Department of Ecology's web -site at: http://www.ecy.wa.gov/programs/wq/wghome.html MAINTENANCE REQUIREMENTS ECDC Section 18.30.090 requires privately -owned stormwater management facilities, such as LID BMPs be properly maintained. The owner of the property is the responsible party for such maintenance. The system must be kept in good working order. The entire system should be inspected once per year. An improperly maintained BMP may cause private property or street flooding. RAMEngineering, Inc. RAM No. 20-024 Contact the City Engineering Division for maintenance information. The City may make periodic inspections of BMPs to ensure they are operating properly. ECDC Section 18.30.100 contains the enforcement provisions the City can use to ensure the system is properly maintained. Bracket's Reserve Stormwater Site Plan Report Page F-1 No. 3 —Closed Detention Systems (Tan kslVauIts) Maintenance Defect Conditions When Maintenance is Needed Results Expected Component When Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is Vents open and blocked at any point or the vent is damaged. functioning. Debris and Sediment Accumulated sediment depth exceeds 10% All sediment and of the diameter of the storage area for 1/2 debris removed from length of storage vault or any point depth storage area. exceeds 15% of diameter. (Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) Joints Between Any openings or voids allowing material to All joint between Tank/Pipe Section be transported into facility. tank/pipe sections (Will require engineering analysis to are sealed. determine structural stability). Tank Pipe Bent Out Any part of tank/pipe is bent out of shape Tank/pipe repaired or of Shape more than 10% of its design shape. (Review replaced to design. required by engineer to determine structural stability). Vault Structure Cracks wider than 1/2-inch and any Vault replaced or Includes Cracks in evidence of soil particles entering the repaired to design Wall, Bottom, structure through the cracks, or specifications and is Damage to Frame maintenance/inspection personnel structurally sound. andlor Top Slab determines that the vault is not structurally sound. Cracks wider than 1/2-inch at the joint of any No cracks more than inlet/outlet pipe or any evidence of soil 1/4-inch vAde at the particles entering the vault through the walls. joint of the inlet/outlet pipe. Manhole Cover Not in Place Cover is missing or only partially in place. Manhole is closed. Any open manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens Not Working maintenance person with proper tools. Bolts with proper tools. into frame have less than 1/2 inch of thread (may not apply to self-locking lids). Cover Difficult to One maintenance person cannot remove lid Cover can be Remove after applying normal lifting pressure. Intent removed and is to keep cover from sealing off access to reinstalled by one maintenance. maintenance person. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design misalignment, not securely attached to standards. Allows structure wall, rust, or cracks. maintenance person safe access. Catch Basins See "Catch Basins" See "Catch Basins" (No. 5). See "Catch Basins" (No. 5) (No. 5). RAM ngineering, Inc. RAM No. 20-024 Volume V — Runoff Treatment BMPs December 2014 4-36 Bracket's Reserve Stormwater Site Plan Report Page F-2 No. 4 — Control Structure/Flow Restrictor Maintenance Defect Condition When Maintenance is Needed Results Expected Component When Maintenance is Performed General Trash and Debris Material exceeds 25% of sump depth or 1 Control structure (Includes Sediment) foot below orifice plate. orifice is not blocked. All trash and debris removed. Structural Damage Structure is not securely attached to Structure securely manhole wall. attached to wall and outlet pipe. Structure is not in upright position (allow up Structure in correct to 10% from plumb). position. Connections to outlet pipe are not watertight Connections to outlet and show signs of rust. pipe are water tight; structure repaired or replaced and works as designed. Any holes --other than designed holes --in the Structure has no structure. holes other than designed holes. Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as designed. Gate cannot be moved up and down by one Gate moves up and maintenance person. down easily and is watertight. Chain/rod leading to gate is missing or Chain is in place and damaged. works as designed. Gate is rusted over 50% of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and missing, out of place, or bent orifice plate. works as designed. Obstructions Any trash, debris, sediment, or vegetation Plate is free of all blocking the plate. obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the Pipe is free of all potential of blocking) the overflow pipe. obstructions and works as designed. Manhole See "Closed See "Closed Detention Systems' (No. 3). See "Closed Detention Systems" Detention Systems' (No. 3). (No. 3). [C�hsin See "Catch Basins' See "Catch Basins' (No. 5). See "Catch Basins' (No. 5). (No. 5). RAM 'Engineering, Inc. RAM No. 20-024 Volume V — Runoff Treatment BMPs December 2014 4-37 Bracket's Reserve Stormwater Site Plan Report Page F-3 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash & Trash or debris which is located immediately No Trash or debris located Debris in front of the catch basin opening or is immediately in front of blocking inletting capacity of the basin by catch basin or on grate more than 10%. opening. Trash or debris (in the basin) that exceeds 60 No trash or debris in the percent of the sump depth as measured from catch basin. the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of six inches clearance from the debris surface to the invert of the lowest pipe. Trash or debris in any inlet or outlet pipe Inlet and outlet pipes free blocking more than 1/3 of its height. of trash or debris. Dead animals or vegetation that could No dead animals or generate odors that could cause complaints vegetation present within or dangerous gases (e.g., methane). the catch basin. Sediment Sediment (in the basin) that exceeds 60 No sediment in the catch percent of the sump depth as measured from basin the bottom of basin to invert of the lowest pipe into or out of the basin, but in no case less than a minimum of 6 inches clearance from the sediment surface to the invert of the lowest pipe. Structure Top slab has holes larger than 2 square Top slab is free of holes Damage to inches or cracks wider than 1/4 inch and cracks. Frame and/or Top Slab (Intent is to make sure no material is running into basin). Frame not sitting flush on top slab, i.e., Frame is sitting flush on separation of more than 3/4 inch of the frame the riser rings or top slab from the top slab. Frame not securely and firmly attached. attached Fractures or Maintenance person judges that structure is Basin replaced or repaired Cracks in unsound. to design standards. Basin Walls/ Bottom Grout fillet has separated or cracked wider Pipe is regrouted and than 1/2 inch and longer than 1 foot at the secure at basin wall. joint of any inlettoutlet pipe or any evidence of soil particles entering catch basin through cracks. Settlement/ If failure of basin has created a safety, Basin replaced or repaired Misalignment function, or design problem. to design standards. Vegetation Vegetation growing across and blocking more No vegetation blocking than 10% of the basin opening. opening to basin. Vegetation growing in inlettoutlet pipe joints No vegetation or root that is more than six inches tall and less than growth present. six inches apart. Contamination See "Detention Ponds" (No. 1). No pollution present. and Pollution RAM Engineering, Inc. RAM No. 20-024 Volume V Runoff TreotmentBMPsDecember 2014 4- 38 Bracket's Reserve Stormwater Site Plan Report Page F-4 No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed Catch Basin Cover Not in Cover is missing or only partially in place. Catch basin cover is Cover Place Any open catch basin requires maintenance. closed Locking Mechanism cannot be opened by one Mechanism opens with Mechanism maintenance person with proper tools. Bolts proper tools. Not Working into frame have less than V2 inch of thread. Cover Difficult One maintenance person cannot remove lid Cover can be removed by to Remove after applying normal lifting pressure. one maintenance person. (Intent is keep cover from sealing off access to maintenance.) Ladder Ladder Rungs Ladder is unsafe due to missing rungs, not Ladder meets design Unsafe securely attached to basin wall, standards and allows misalignment, rust, cracks, or sharp edges. maintenance person safe access. Metal Grates Grate opening Grate with opening wider than 7/8 inch. Grate opening meets (If Applicable) Unsafe design standards. Trash and Trash and debris that is blocking more than Grate free of trash and Debris 20% of grate surface inletting capacity. debris. Damaged or Grate missing or broken member(s) of the Grate is in place and Missing. grate. meets design standards. No. 6 — Debris Barriers (e.g., Trash Racks) Maintenance Defect Condition When Maintenance is Results Expected When Components Needed Maintenance is Performed General Trash and Trash or debris that is plugging more Barrier cleared to design flow Debris than 20% of the openings in the barrier. capacity. Metal Damaged/ Bars are bent out of shape more than 3 Bars in place with no bends more Missing inches. than 3/4 inch. Bars. Bars are missing or entire barrier Bars in place according to design. missing. Bars are loose and rust is causing 50% Barrier replaced or repaired to deterioration to any part of barrier. design standards. Inlet/Outlet Debris barrier missing or not attached to Barrier firmly attached to pipe Pipe pipe RAM ngineering, Inc. RAM No. 20-024 Volume V— Runoff Treatment BMPs December2014 4- 39 Bracket's Reserve Stormwater Site Plan Report Page F-5 ` Oldcastle Infrastructure" A CRH COMPANY � a 4 hol, N 91494 hal nspection and Maintenance Guide RAM 7gineering, Inc. RAM No. 20-024 0 0 Water Bracket's Reserve Stormwater Site Plan Report Page F-6 PerkFilter"' Media Filtration System Description The PerkFilter is a stormwater treatment device used to remove pollutants from urban runoff. Impervious surfaces and other urban and suburban landscapes generate a variety of contaminants that can enter stormwater and pollute downstream receiving waters. The PerkFilter is a media -filled cartridge filtration device designed to capture and retain sediment, gross solids, metals, nutrients, hydrocarbons, and trash and debris. As with any stormwater treatment system, the PerkFilter requires periodic maintenance to sustain optimum system performance. Function The PerkFilter is a water quality treatment system consisting of three chambers: an inlet chamber, a filter cartridge treatment chamber, and an outlet chamber (Figure 1). Stormwater runoff enters the inlet chamber through an inlet pipe, curb opening, or grated inlet. Gross solids are settled out, and floating trash and debris are trapped in the inlet chamber. Pretreated flow is then directed to the treatment chamber through an opening in the baffle wall between the inlet chamber and treatment chamber. The treatment chamber contains media -filled filter cartridges (Figure 2) that use physical and chemical processes to remove pollutants. During a storm event, runoff pools in the treatment chamber before passing radially through the cylindrical cartridges from the outside surface, through the media for treatment, and into the center of the cartridge. At the center of the cartridge is a center tube assembly designed to distribute the hydraulic load evenly across the surface of the filter cartridge and control the treatment flow rate. The center tube assembly discharges treated flow through the false floor and into the outlet chamber. A draindown feature built into each cartridge allows the treatment chamber to dewater between storm events. Precast concrete vault Inlet chamber Inlet pipe Bypass assembly Filter cartridge treatment chamber Concrete false floor Figure 1. Schematic of the PerkFilter system. RAMEngineering, Inc. RAM No. 20-024 ccess covers Outlet hood Outlet pipe Outlet chamber Bracket's Reserve Stormwater Site Plan Report Page F-7 All PerkFilter systems include a high -flow bypass assembly to divert flow exceeding the treatment capacity of the filter cartridges around the treatment chamber. The bypass assembly routes peak flow from the inlet chamber directly to the outlet chamber, bypassing the treatment chamber to prevent sediment and other captured pollutants from being scoured and re -entrained by high flow. Treated flow and bypass flow merge in the outlet chamber for discharge by a single outlet pipe. Vent tube Outer media to Center tube assembly Inner media la Outer screen Connection to outlet chamber (with draindown) Figure 2. Schematic of PerkFilter cartridge. Configuration The PerkFilter structure may consist of a vault, manhole, or catch basin configuration. Catch basin units may be fabricated from concrete or steel. Internal components including the PerkFilter cartridges are manufactured from durable plastic and stainless steel components and hardware. All cartridges are 18 inches in diameter and are available in two heights: 12-inch and 18-inch. Cartridges may be used alone or may be stacked (Figure 3) to provide 24-inch and 30-inch combinations. The capacity of each cartridge or cartridge combination is dictated by the allowable operating rate of the media and the outer surface area of the cartridge. Thus, taller cartridges have greater treatment capacity than shorter cartridges, but they also require more hydraulic drop across the system. Cartridges may be filled with a wide variety of media but the standard mix is composed of zeolite, perlite and carbon (ZPC). Access to an installed PerkFilter system is typically provided by ductile iron castings or hatch covers. The location and number of access appurtenances is dependent on the size and configuration of the system. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-8 Vent tube (4"dia.) Top stacked cartridge inner interconnector coupling (2" dia.) Outer interconnector coupling (4" dia.) or bottom stacked cartridge ?ne bottom cap Slip coupler (2" dia.) Figure 3. Schematic of stacked cartridges and connector components. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-9 Maintenance Overview State and local regulations require all stormwater management systems to be inspected on a periodic basis and maintained as necessary to ensure performance and protect downstream receiving waters. Maintenance prevents excessive pollutant buildup that can limit system performance by reducing the operating capacity and increasing the potential for scouring of pollutants during periods of high flow. Inspection and Maintenance Frequency The PerkFilter should be inspected on a periodic basis, typically twice per year, and maintained as required. Initially, inspections of a new system should be conducted more frequently to help establish an appropriate site - specific inspection frequency. The maintenance frequency will be driven by the amount of runoff and pollutant loading encountered by a given system. In most cases, the optimum maintenance interval will be one to three years. Inspection and maintenance activities should be performed only during dry weather periods. Inspection Equipment The following equipment is helpful when conducting PerkFilter inspections: • Recording device (pen and paper form, voice recorder, Pad, etc.) • Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.) • Traffic control equipment (cones, barricades, signage, flagging, etc.) • Socket and wrench for bolt -down access covers • Manhole hook or pry bar • Flashlight • Tape measure • Measuring stick or sludge sampler • Long -handled net (optional) Inspection Procedures PerkFilter inspections are visual and may be conducted from the ground surface without entering the unit. To complete an inspection, safety measures including traffic control should be deployed before the access covers are removed. Once the covers have been removed, the following items should be checked and recorded (see form provided at the end of this document) to determine whether maintenance is required: • Inspect the internal components and note whether there are any broken or missing parts. In the unlikely event that internal parts are broken or missing, contact Oldcastle Infrastructure at (800) 579-8819 to determine appropriate corrective action. • Note whether the inlet pipe is blocked or obstructed. The outlet pipe is covered by a removable outlet hood and cannot be observed without entering the unit. • Observe, quantify and record the accumulation of floating trash and debris in the inlet chamber. The significance of accumulated floating trash and debris is a matter of judgment. A long -handled net may be used to retrieve the bulk of trash and debris at the time of inspection if full maintenance due to accumulation of floating oils or settled sediment is not yet warranted. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-10 • Observe, quantify and record the accumulation of oils in the inlet chamber. The significance of accumulated floating oils is a matter of judgment. However, if there is evidence of an oil or fuel spill, immediate maintenance by appropriate certified personnel is warranted. • Observe, quantify and record the average accumulation of sediment in the inlet chamber and treatment chamber. A calibrated dipstick, tape measure, or sludge sampler may be used to determine the amount of accumulated sediment in each chamber. The depth of sediment may be determined by calculating the difference between the measurement from the rim of the PerkFilter to the top of the accumulated sediment, and the measurement from the rim of the PerkFilter to the bottom of the PerkFilter structure. Finding the top of the accumulated sediment below standing watertakes some practice and a light touch, but increased resistance as the measuring device is lowered toward the bottom of the unit indicates the top of the accumulated sediment. • Finally, observe, quantify and record the amount of standing water in the treatment chamber around the cartridges. If standing water is present, do not include the depth of sediment that may have settled out below the standing water in the measurement. Maintenance Triggers Maintenance should be scheduled if any of the following conditions are identified during the inspection • Internal components are broken or missing. • Inlet piping is obstructed. • The accumulation of floating trash and debris that cannot be retrieved with a net and/or oil in the inlet chamber is significant. • There is more than 6" of accumulated sediment in the inlet chamber. • There is more than 4" of accumulated sediment in the treatment chamber. • There is more than 4" of standing water in the treatment chamber more than 24 hours after end of rain event. • A hazardous material release (e.g. automotive fluids) is observed or reported. • The system has not been maintained for 3 years (wet climates) to 5 years (dry climates). Maintenance Equipment The following equipment is helpful when conducting PerkFilter maintenance: • Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.) • Traffic control equipment (cones, barricades, signage, flagging, etc.) • Socket and wrench for bolt -down access covers • Manhole hook or pry bar • Confined space entry equipment, if needed • Flashlight • Tape measure • 9/16" socket and wrench to remove hold-down struts and filter cartridge tops • Replacement filter cartridges • Vacuum truck with water supply and water jet Contact Oldcastle Infrastructure at (800) 579-8819 for replacement filter cartridges. A lead time of four weeks is recommended. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-II Maintenance Procedures Maintenance should be conducted during dry weather when no flow is entering the system. Confined space entry is necessary to maintain vault and manhole PerkFilter configurations. Only personnel that are OSHA Confined Space Entry trained and certified may enter underground structures. Confined space entry is not required for catch basin PerkFilter configurations. Once safety measures such as traffic control are deployed, the access covers may be removed and the following activities may be conducted to complete maintenance: • Remove floating trash, debris and oils from the water surface in the inlet chamber using the extension nozzle on the end of the boom hose of the vacuum truck. Continue using the vacuum truck to completely dewater the inlet chamber and evacuate all accumulated sediment from the inlet chamber. Some jetting may be required to fully remove sediment. The inlet chamber does not need to be refilled with water after maintenance is complete. The system will fill with water when the next storm event occurs. • Remove the hold-down strut from each row of filter cartridges and then remove the top of each cartridge (the top is held on by four 9/16" bolts) and use the vacuum truck to evacuate the spent media. When empty, the spent cartridges may be easily lifted off their slip couplers and removed from the vault. The couplers may be left inserted into couplings cast into the false floor to prevent sediment and debris from being washed into the outlet chamber during washdown. • Once all the spent cartridges have been removed from the structure, the vacuum truck may be used to evacuate all accumulated sediment from the treatment chamber. Some jetting may be required to fully remove sediment. Take care not to wash sediment and debris through the openings in the false floor and into the outlet chamber. All material removed from the PerkFilter during maintenance including the spent media must be disposed of in accordance with local, state, and/or federal regulations. In most cases, the material may be handled in the same manner as disposal of material removed from sumped catch basins or manholes. • Place a fresh cartridge in each cartridge position using the existing slip couplers and urethane bottom caps. If the vault is equipped with stacked cartridges, the existing outer and inner interconnector couplers must be used between the stacked cartridges to provide hydraulic connection. Transfer the existing vent tubes from the spent cartridges to the fresh cartridges. Finally, refit the struts to hold the fresh cartridges in place. • Securely replace access covers, as appropriate. • Make arrangements to return the empty spent cartridges to Oldcastle Infrastructure. RAMEngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-12 PerkFilter Inspection and Maintenance Log Location Structure Configuration and Size: Inspection Date ❑ Vault feet x feet ❑ Manhole feet diameter ❑ Catch Basin feet x feet Number and Height of Cartridge Stacks: Media Type: Count each ❑l2" ❑ 18" ❑ 24" ❑ 30" ❑ ZPC ❑ Perlite ❑ Other Condition of Internal Components Notes: ❑ Good ❑ Damaged ❑ Missing Inlet or Outlet Blockage or Obstruction Notes: ❑ Yes ❑ No Floating Trash and Debris Notes: ❑ Significant ❑ Not Significant Floating Oils Notes: ❑ Significant ❑ Not Significant ❑ Spill Sediment Depth in Inlet Chamber Notes: ❑ Inches of Sediment: Sediment Depth in Treatment Chamber Notes: ❑ Inches of Sediment: Standing Water in Treatment Chamber Notes: ❑ Inches of Standing Water: Maintenance Required ❑ Yes - Schedule Maintenance ❑ No - Inspect Again in Months RAM ngineering, Inc. RAM No. 20-024 Bracket's Reserve Stormwater Site Plan Report Page F-13 PERKFILTER TM OUR MARKETS BUILDING COMMUNICATIONS STRUCTURES WATER 0. Oldcastle Infrastructure 800-57 dcast leinfrastructure.com A CA COMPANY 00-579-8819 RAMEngineering, Inc. RAM No. 20-024 ENERGY TRANSPORTATION Owater February 2019 v.1 Bracket's Reserve Stormwater Site Plan Report Page F-14 ENGINEERING, INC. Civil Engineering /Land Planning