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Drainage Report.pdf184th Street Short Pllat Drainage Report 86$y 18,1 Street SW, Edmonds, WA 98026 SDA Project #291-016-16 May 24, 2017 COMPLIES WITH APPLICABLE UTY "R CODE Date.�� w� �1 —7 Prepared for: Lee Johnson 2410 W Park Drive E Seattle, WA 98112 MAY 2 6 2017 ENGINEERING DIVISION CIVIL ENGINEERING l PROJECT MANAGEMENT I PLANNING 1724 W Marine View Drive, Suite 140, Everett, WA 98201 425.486.6533 www.sdaengineers co .....,,m r` r% xi'm 184t" Street Short P'lat Preliminary Drainage Report Prepared For: Lee Johnson 2410 W Park Drive E Seattle, WA 98112 Pre Rared @y: SDA Engineers 1724 West Marine View Drive, Ste 140 Everett, WA 98201 (425) 486-6533 05-24-17 I by I M)rly I Ioai q oil 7 1 �' \1 11 1 (1 ("(� I o I -I I-] so I))\010, 1G (I d I I I ki)\ I rc I-) I lrl� I'\ I �'opni 1 05- 05 f)1 ll I "" q c kqpofl docim 184"' Street Short Plat Drainage Report TABLE OF CONTENTS EXECUTIVE SUMMARY . Executive Summary • Vicinity Map SECTION 1 — PREPARATION OF STORMWATER SITE PLANS . Stormwater Site Plan Preparation Tasks • Appendix 1A — Existing Condition Summary Documents Appendix 1B — Geotechnical Engineer's Report Appendix 1 C — Downstream Flowpath Analysis SECTION 2 — STORMWATER POLLUTION PREVENTION PLAN (SWPPP) Stormwater Pollution Prevention Plan • Appendix 2A — Site Plan with BMP Measures • Appendix 2B — SWPPP Project Summary • Appendix 2C — Alternative BMPs Appendix 2D — General Permit Appendix 2E — Site Log & Inspection Forms SECTION 3 — SOURCE CONTROL OF POLLUTION *Source Control of Pollution SECTION 4 — PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS • Natural Drainage Course Description SECTION 5 - ON-SITE STORMWATER MANAGEMENT Existing Site Hydrology Developed Site Hydrology • Performance Standards • Appendix 5A — Basin Mapping SECTION 6 — RUNOFF TREATMENT • Runoff Treatment Appendix 6A — Water Quality Design Calculations SECTION 7 — FLOW CONTROL Flow Control Performance Standards Appendix 7A — Flow Control Design Calculations SECTION 8 — WETLANDS PROTECTION SECTION 9 — OPERATIONS AND MAINTENANCE SECTION 10 — OFFSIET ANALYSIS AND MITIGATION SECTION 11 — FINANCIAL LIABILITY 184`h Street Short Plat Drainage Report SECTION 1 PROJECT OVERVIEW 1841h Street Short Plat Drainage Report EXECUTIVE SUMMARY The 180' Street Short Flat project proposes the construction of 8 single family residential building lots on approximately 0. 86 acre parcel, located on 8682 180 Street SW, Edmonds, Washington. The protect will clear, grade and construct a neighborhood residential roadway, utility extensions, and stormwater infrastructure The project is located In a portion of the NW quarter of Section 18, TWIG 27N, RGE 4E„ W.M. in the City of Edmonds. The existing Snohomish County tax parcel is 004 4600001006, A vicinity map has been included as Figure 1 of this document. The existing site is an undeveloped forested lot with a relatively constant mild slope towards the north. The elevation of the property drops from 386 feet along the southern border to 828 along the north border adjacent to 184`h Street SW. The project site will be entirely cleared in preparation for the project. The project is subject to the provisions of Chapter 18.80 of the City of Edmonds Stormwater Code Supplement to Edmonds Community Develop Code, which is supplemented to the Washington State Department of Ecology Stormwater Management Manual for Western Washington (2006 edition),. The project will add more than 6,000 square feet of new impervious surface, thus minimum requirements 1-11 apply to this project, including both flow control and water quality requirements, Since the entire parcel falls consistently to the north, the project site occupies a single threshold discharge area (TDA), The project is required to utilize on-site stormwater management techniques„ and is proposing to detain roof runoff with the use of bioretention facilities to meet this requirement. In addition permeable pavement will be used for the access road and each lot's associated driveway. For the frontage, it is not feasible to detain and/or treat all of this area. Therefore the runoff from the bypass basin will flow west into the existing storm drainage system along 1841h Street SW and will ultimately discharge into Puget Sound. 184"' Street Short Plat Drainage Report VICINITY MAP 7 1" <) Ix7�,,> Li lll� X" 7A . ................ A, . .... . ..... .......... ----------- Dr, Ld PROJECT x — — — --------- LOCATION U� 00 00 c2> ...... V) a- :>Lli LZ U) p........... CD U) 0 0 E T 196TH > c 0 U) C N.T.S. 1 0 TPH Design IvIlEngineedng 184TH ST. SHORT PLAT NTS C,4 TPH Project management Planning Drawn wow cScale a) 11/08/2016 1724 W. Marine Mew Dive, sure 140: Evereti, WashIngton 98201 00 — — ------ — VICINITY u 0Date Office: 425,486.6533 F-42SA866593 —A.engTneencom ol > 291-16-16 MAP Figure No. 0 Project �No. z 61 SECTION 1 MINIMUM REQUIREMENT #1 PREPARATION OF STORMWATER SITE PLANS 180' Street Short Plat Drainage Report PREPARATION OF STORMWATER SITE PLANS The project is subject to the drainage regulations outlined in Volume I from the Department of Ecology's 2005 Stormwater Management Manual for Western Washington (SWMMWW). This report, along with the accompanying plans, is intended to satisfy the drainage manual's site plan preparation requirements. The manual also requires completion, of the following four tasks as part of the site plan preparation process: Task 1: Define and map the study area The project site consists of I parcel totaling approximately 0.86 acres. The site is undeveloped with no existing structures or driveways. The applicant is proposing to subdivide the existing parcels into 3 lots, The project study area includes the project site itself, and a downstream flowpath for a distance of one mile. Task 2: Review all available information on the study area FEMA identifies the project site on Flood Insurance Rate Map (FIRM) Panel #53061 C1 305E, included in Appendix 11A. The project site is not expected to be within a flood hazard area. The MRCS Web Soil Survey classifies the underlying soil at the project site as Alderwood-Urban Land Complex. Alderwood soils are generally described as a glacially consolidated till, with a hardpan layer. Both soil types are typically considered to have moderate runoff rates with little capacity for infiltration. The MRCS Web Soil Survey is included in Appendix 11A. A geotechnical study of the site has confirmed the presence of till soils above much of the site. However, it also indicates that an outwash layer, high permeability, lies above a till layer. The test pits for the project also suggest that sandy and outwash soil varieties are exposed throughout the site. With this in mind, bioretention appears to be feasible on the site, so long as the infiltration facilities are placed in the areas of the outwash soils. The geotechnical report has been provided in Appendix 1i3 of this report, and provides recommended infiltration rates for the disposal of stormwater runoff. Task 3: Field inspect the study area A field visit of the study area was conducted on November 1, 2016, The conditions at the time of the visit were cloudy and dry, with recent rainfall having occurred. The site generally falls toward the north, and the road immediately to the north contains a stormwater management system Surface runoff from the project site generally flows toward the north, toward 184`" Street SW'. 1841" Street SW' currently has a crowned roadway section,, so runoff is expected to be contained along the south side. Runoff from this structure ultimately discharges to Puget Sound, as discussed in Task 4 below. Task 4: Describe the drainage system, and its existing and predicted problems A downstream flowpath map was taken from the City of Edmonds Stormwater Inventory website, and indicates the known stormwater features near the site. The downstream fiowpath map has been provided in Appendix 1C. As mentioned above, the existing site topography falls to the north toward 180 Street SW, and is collected on the south edge of the roadway. There is a well-defined existing storm ditch along the south side of 184"' Street SW where the coilected runoff will head east and ultimately discharged into Puget Sound. The last quarter mile of the downstream was inaccessible due to the conveyance system within fenced areas on private property. 180 Street Short Plat Drainage Report SECTION 1A EXISTING CONDITION SUMMARY DOCUMENTS 784`h Street Short Plat Drainage Report 47° 49'56'N 47° 49'52'N Soil Map—Snohomish County Area, Washington 3 548540 548550 548560 548570 548550 548590 548600 3 Map Scale: 1:633 if printed on A portrait (8.S' x 11") sheet Meters 0 5 10 20 30.� . , r:" ..... ......... Wil" 0 30 60 120 180 Map projection: eon: Web Mer ^ �.. 30 for Comer coordinates: WCLS&} Edge tib: IJTM Zone lON WGS84 USDA Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey S4tIb1U YWbLV 47" 49'56" N ry 47° 49'52" N ut xzswu 3 N 10/31/2016 Page 1 of 3 Z O O LL Z Ca C 0 Z 'W V W J a a) C � C O O N N N a3 7 U 16 C a) C U 0 U .p N O CDUN N cu a) Q N N p p m U z6 -D N O U E f6 A2 o E o m' N E CL i6 N d Ca N E 3 m ... O O C > NO 9 : .p O N O 0>,,o C C C a)O a) N L L E m ooft = m > m E E L o -0(D22 o c MC B U) a) ` U O) E a)a) f0 E 2), E w �p 7 N f6 N N WE n U)i U Cl) O O N N M N O N r d a) 7 U I a) (9 0 C) O CI >O O j Co N N O { N N �_ N CO o CL a) d LL U O) Z O L N 7 0 N N 7 C c 0` E 0 NcD in 7� L N N E a) O) C N N O N —E V N —O O` Lo C a) L�� 0 L c9 n _ N.0 O N lC C M .5 Q O N N 7 U) U >O >� E ' L .r N N N U' O N 21.0 N Z Co N O J m `ry V E N o �a CD -0 0— N Q ¢� 3 ami ` E N W U O C p 7 O CL d � C a O Ca L a N 3 N C` N N d L N p N C N a1 7 p N O Q aJ 2 N U 3 a3 V C O g 0 w U r U p N-0 N O E m C 0 O a) Dag p C a7 > . m 3 Eo N E N L a a) a) E o a) .0 a) � N U p Z 2,5 o N ¢ N 0 >, aL E mL o ao n ---0 _ o a) > m a) I J U) N C C O N U) .0 U L p C LD pw�a ZE E mi na" ° CO - rnm m o) CU o� Y na) > m 2 X05 X0`0M 0 -0 o •c p N 2:1E co U) w 3 i -p T O C L aL L —0 N N w '� O '� C E C O Q O D O a) p .� p N a) Z Q 7 0_ N On.0 7 L y N (n-0 N O C` (O a N U p E �' _ N 0 O O- a) p cam 7(D 0.0 ate:° 0 U N > — Z — � ='� a) E'M E a E co> U dOQ U H w U)U) U) O ON H U.- O U Cl) O O N N M N O N r d a) 7 U I o CL a) d LL U t L U N O N Ol O L N 0. ¢` CO ~O in a J m `ry N E N .0. 'o O o C U a1 N U U > () U U C (6 O c U O W 0J N ¢ 1"0 N LLCL t O ) 7 Q A C L v� F m O N C 00 w a Cf) 0)) O O C O o N a d a Y a w E ? N N a N U) n a1 3 o a) p o- Oa fa 7 > a a a) a1 > .. y 3 w a o a) 0 .. a U > _ 3 o L 0 a `O c " E U Q o co °a U W >. m O O n U 0 LL 3 3 II LL l O A N > Y N 'O U U Cl) O 'Q m ca L) J J (L U U U U U U a c a O m v /ts T �p 'Oi! q� h"� pp 'Mii' e� d' a Ao0 H a iCi 4 ` '0 N Q N U Cl) O O N N M N O N r d a) 7 U I Soil Map—Snohomish County Area, Washington "lap Unit Legend Snohomish County Area, Washington (WA661) _.... Map Unit Symbol Map Unit Name Acres in AOI ....... _ ... _ _ ....mm. Mderwood-Urban land complex, 2 to 6 percent slopes Totals for Area of Interest Percent of AOI 1.2 100.0% 1.2 100.0% .m _.__........ _......._. USDA Natural Resources Web Soil Survey 10/31/2016 Conservation Service National Cooperative Soil Survey Page 3 of 3 0 Q 0 vC4 W C 7 O O N C N 10 r 4U9 �,..�....�� .,........w..,.—.......�._..........�.�.�.,..... .....m .............. .... .......gym.... ....��....,... E U o O CD 0 CD Lu Lj CD 2 OC d d Ln as F-- o Cr W W Lu � m a m cTw m �j 93 ~ ¢a ' O Z LL ... O a C W �` N N] (� f� d Q m O z 4 oc O A z� m� u W n cc W W w J N z ri E a� W Q q E 9 Q o REE LL x O z N N N U o U)E4 ^o d d E`oQ _ C � o 0oJ C/� "� mw o�� ego nvv�� Lu I.L Z F-1 I"�"1 O u t,f N C C D -, W u LL OHN p Zooq W cm�v z o �+xp �a z 0xcmL° o O z U W a LL - cc U6 U) k o` CL J � �� .1 L ._...,.::.._mm ..., O o � C Y c 0 U E � �E 41 oma w a �a as rw cn W�W Z H19/ vxi 1S3M O a O P: �7M1.��1 -1--� Id H18L wn a O 1S]M Z Z Id MAI Kl M cn z 1S3M 3nN3AV 1108 p Q ►� zra 1S3M 3nN3AV O w �i cc w w �..i .1IIN3AV lAA00NV z (� 4 0 1S3M 3nv aaEB / O u 3nN3nv f� rOt/9�� A,� e ri a is un.r f' uj w 17 t W cru O H r-- � oz O ��r /rr irr rJiry ,° ti N w /�%/� i��✓�� V Cdr � � i ¢ %l'i 1st " m u i rr�l� Nva iii r� �'�rnNIAV 1S3M x 3 H188 fi/rlrQf` 1��t';�ir m rra��r�/i1✓� �"rpt /�� y y rr �i�v y�i�f � �� At!m 13s ns I�9l,�rJir i,5,cgr�rr� r�l✓r�� ^�/�/ir l�li�irill��ll ,�i�%i��Xr��i� /i/�� /ir✓i'�A%ti�ui ,r "w /5��1%/rr � �rrr�%/i�/�� /� �y%! �r1�4!w%/rrt%i%r%" X111✓ �r� irk%rI �r "�� , 3bii iJ fA�i rGY/ ➢ l l / l i ✓� a .._ „ ...,, 3nN3AV SECTION 1 B GEOTECHNICAL ENGINEER'S REPORT 180 Street Short Plat Drainage Report LIU & ASS C Ar ES, INC. Geotechnical Engineering Engineering Geology November 3, 2016 Mr. Andrew Reaves Site Development Associates, LLC 1724 West Marine View Drive, Suite 140 Everett, WA 98006 Dear Mr. Reaves: Subject: Infiltration Tests 3 -Lot Plat 87xx - 184th Street SW Edmonds, Washington L&A Job No. 16-121A INTRODUCTION Earth Science We understand the development of a 3 -lot plat residential project is proposed for the property located at the above address in Edmonds, Washington, and that a new single- family residence is to be constructed on each of the three lots. We also understand that onsite stormwater disposal by infiltration is being considered for this project. At your request, we have completed a geotechnical investigation to explore subsurface conditions of the project site and conducted three in-situ infiltration tests to determine subgrade soil infiltration rates to be used for design of onsite stormwater disposal facilities. Presented in this report are our findings of project site conditions, results of our infiltration tests, and our recommendations for onsite stormwater disposal. SCOPE OF SERVICES To achieve the above, we propose a scope of services comprising specifically the following: 19213 Kenlake Place NE - Kenmore, Washington 98028 Phone (425) 483-9134 - Fax (425) 486-2746 November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121 A Page 2 1. Review geologic and soil conditions at the project site based on a published geologic map. 2. Excavate test pits to explore subsurface conditions of the site up to the maximum depth capable by the backhoe used in test pit excavation. 3. Perform three in-situ infiltration tests, one on each lot, in a targeted soil layer. The tests will be conducted in accordance with the requirements and procedure outlined in 2012S to'n' p tiler �rla��a�cn git Manual for Western Washing_�e p by Washington State Department of Ecology. 4. Prepare a written report to present our findings of subsurface conditions of the site, infiltration test results, and our recommendations for design and construction of stormwater disposal facilities. SITE CONDITIONS Surface Condition The general location of the project site is shown on Plate 1 - Vicinity Map. The site is situated on a gentle northwesterly -descending plain. The ground within the site generally slopes down gently northward with a very -gentle cross slope down to the west. The site is bounded by 184th Street SW to the north and adjoined by residential development to the south, east and west. The site is currently undeveloped and is dotted by tall, mature, evergreen and deciduous trees with thick underbrush. The lots are to be accessed by a paved driveway traversing the west side of the site. LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121A Page 3 Geologic Setting The ie l )ga 1 1 of the Edmonds 1 ass and Part, of the1,dniopd West_Q11Ldrangl " 'a hjRMq, by James P. Minard, published by U. S. Geological Survey in 1983, was referenced for the geologic and soil conditions at the residence site. According to this publication, the surficial soil unit at and in the vicinity of the project site is mapped as Vashon Till (Qvt) deposits. The geology of the Puget Sound Lowland has been modified by the advance and retreat of several glaciers in the past one million years or so and the subsequent deposits and erosions. The latest glacier advanced to the Puget Sound Lowland is referred to as the Vashon Stade of the Fraser Glaciation which had occurred during the later stages of the Pleistocene Epoch, and retreated from the region some 12,500 years ago. The deposits of the Vashon till soil unit were plowed directly under glacial ice during the most recent glacial period as the glacier advanced over an eroded, irregular surface of older formations and sediments. This soil unit is composed of a mixture of unsorted clay, silt, sand, gravel, and scattered cobbles and boulders. The Vashon till soil over the top two to four feet is normally weathered to a medium -dense state, and is moderately permeable and compressible. The underlying fresh till soil, commonly referred to as "hard pan", is very -dense and weakly -cemented. The fresh till soil possesses a compressive strength comparable to that of low-grade concrete and can remain stable on steep natural slopes or man -make cuts for a long period. The fresh till deposits can LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121 A Page 4 provide excellent foundation support with little or no settlement, but are of extremely low permeability. Soil Condition Subsurface conditions of the project site were explored with four test pits. These test pits were excavated on August 22, 2016, with a rubber -tracked backhoe, to depths from 8.0 to 10.0 feet deep. The approximate locations of the test pits are shown on Plate 1 - Site and Exploration Location Plan. The test pits were located with visual reference to existing topographic features in the field and on the topographic survey map, and their locations should be considered as only accurate to the measuring method used. A geotechnical engineer from our office was onsite to monitor subsurface exploration, examine the soil and geologic conditions of each soil layer encountered, and keep logs of the test pits. Soil samples obtained from each soil layer in the test pits were visually classified in general accordance with United Soil Classification System, a copy of which is presented on Plate 3. Detailed descriptions of soil layers encountered during site exploration are presented in test pit log on Plates 4 and 5. The test pits encountered a layer of loose organic topsoil about 11 to 14 inches thick mantling the project site. The topsoil is underlain by a layer of weathered soil consisting of light -brown, loose to medium -dense, silty fine sand with trace gravel, from about 1.9 to 3.5 feet thick. Underlying this weathered soil layer to the depths explored is a glacial till LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121 A Page 5 deposit of light -gray, very -dense, cemented, gravelly, silty, fine sand with occasional cobble. Groundwater Condition Groundwater seepage was not encountered by the four test pits excavated on the project site. The light -gray, very -dense, cemented glacial till deposit underlying the site at shallow depth is of extremely low permeability and would perch stormwater infiltrating into the surficial more permeable soils. The amount of and the depth to the near -surface perched groundwater would fluctuate seasonally, depending on precipitation, surface runoff, ground vegetation cover, site utilization, and other factors. The perched groundwater would accumulate and rise in the wet winter months and may dry up completely during the dryer summer months. IN-SITU INFILTRATION TESTS Stormwater Management Manual Three in-situ infiltration tests, one for each lot, have been completed for the proposed development project. The tests were conducted in accordance with the requirements and procedure of Small -Scale Pilot Infiltration Test procedure outlined in Volume III of the 2012 Storniwater.....[ rl t' 11 a t mm 1 ual _...._ itr �e t Ml.... _%M' rg c r , published by Washington State Department of Ecology to determine infiltration rates of the weathered soil of light -brown, loose to medium, light -brown, silty fine sand with trace gravel, underlying the project site at shallow depth. EIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121A Page 6 Test Pits and Subsurface Condition Three in-situ infiltration tests were completed on August 22, 2016. The locations of the infiltration tests, IT -1, IT -2, and IT -3, are shown on Plate 2. Dimensions of the test pits and soil condition at bottom of the pit are presented in the table below: TEST PIT DIMENSIONS AND SOIL CONDITION Infiltration Test Procedure The infiltration test pits were filled with water to about 18 to 24 inches deep for hours to soak the soils underneath the pits. Clear tap water was used in the tests. Infiltration tests were then conducted in the pit by falling head method with the initial water level at about 18 to 24 inches deep. A steel bar was placed across the top of the pits and water levels from the steel bar were measured in the beginning and at the end of a one-hour period. The initial infiltration rates, Ksat lnitiab in inches per hour (iph), were thus determined. The results of the infiltration tests are presented in the table below: LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121 A Page 7 INFILTRATION TEST RESULTS Test _ Water Level ..._..... Elapsed Infiltration Infiltration Begin End Rate, Ksat initw Rate, b Ksat o• .. Time, Hr. In./Hr. In./Hr. IT -1 20..1/4 ��...... 24-1/2 �� _ ...1.. 4.25 _....i - 1.23 IT -2 ---....20-1/4 ��_ 25-1/8 ��.1 --_....m_.�.�,. �....—............- 4.875 __ .... 1.41 IT -3 23-1 F- 25-1 /8 " 1 1.875 0.54 -- a cross of pit Measured from a steel T -bar placed atop . . . . ....... . . ............ b Ksat = CFT x Ksat initial , Where CFT = CF, x CFt x CFR, Design Infiltration Rates As shown in the equation above, the Ksat initial values determined by the infiltration tests are to be modified by correction factors to obtain the design infiltration rate, Ksat- The correction factors include: site variability and number of locations tested (CFS,), uncertainty of test method (CFt), and degree of influent control to prevent siltation and bio -buildup (CFR,). According Table 3.3.1 of the DOE Manual, CF,, = 0.33 to 1.0, CFt = 0.5 for small scale test, and CF,,, = 0.9. Use a middle value 0.65 for CF.,. thus. CR, = (0.65) (0.5) (0.9) = 0.29. The K,at values for the infiltration tests were thus calculated and are shown in the table above to be used for design of infiltration facilities to be constructed on respective lots. LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-12 IA Page 8 Infiltration Facility Construction Infiltration facilities (infiltration trenches or rain gardens) should be set back at least 5 feet from property lines and 10 feet from nearby building foundations or utility trenches. To minimize potential foundation damage to the proposed new residences, the building foundations should be constructed on or into very -dense cemented glacial till soil. The bottom of infiltration facility trenches or pits should be cut at least one foot into the targeted weathered soil layer of light -brown, loose to medium -dense, silty fine sand with trace gravel. The soil condition at bottom of infiltration facility trenches or pits should be verified by a geotechnical engineer. Stability of cut banks of infiltration facility trenches or pits more than 4 feet deep should also be verified by a geotechnical engineer during excavation. The side walls (but not the bottom) of infiltration facility trenches or pits should be lined by a layer of non -woven filter fabric (Miraf. 140NS). The trenches or pits are then filled with clean, 3/4 to 1-1/2 inch washed gravel or crushed rock to within about 12 inches of the finish grade. Gravel or crushed rock coated with mud should not be used. Installation of filter fabric lining and backfilling trenches or pits should be carried out carefully to prevent fine-grained soils from falling into and sealing off bottom of the trenches or pits. For infiltration trenches or galleries, the dispersion pipes, consisting of 4 -inch, perforated PVC pipes, spaced at no more than 4 feet on centers, should be embedded in the gravel or crushed rock fill at about 1.5 to 2 feet below top of trenches or pits. The top of the gravel or crushed rock fill should then be covered with the same filter fabric and the remaining LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121A Page 9 trenches or pits may be filled with compacted onsite clean sandy soil. Gravel or crushed rock fill under driveways and parking areas should be placed in 10 -inch lifts with each lift densified to a non -yielding state with a vibratory mechanical compactor. Compaction and densification of trench fill is critical if it is to support driveways or parking areas. Stormwater captured over paved driveways or parking areas should be routed into a catch basin equipped with an oil -water separator before being released into the infiltration facilities. For rain gardens, the sloped banks should be no steeper than 2-1/2H: IV for cut banks and no steeper than 3H:1 V for fill embankinents. Footprints of fill embankments should be cleared and thoroughly grubbed and surficial topsoil and weathered soils completely stripped down to medium -dense weathered soil. Fill embankments should be constructed of clean, fine-grained, fine -sandy to clayey silt or clay soil, free of organics and other deleterious substances, with the following gradation requirements: ��o 1' � singi, U S. t mmndard ieve No. 100 10 65-90 20 50-75 40 40-70 60 35-60 100 30-50 200 Fill embankments should be placed in lifts no more than 8 -inch thick in loose state and compacted to at least 95% of the maximum dry density determined by ASTM D1557 LIU & ASSOCIATES, INC. November 3, 2016 Infiltration Tests - 3 -Lot Plat L&A Job No. 16-121 A Page 13 Five plates attached Yours very truly, LIU & ASSOCIATES, INC. J. S. (Julian) Liu, Ph.D., P.E. Principal LIU & ASSOCIATES, INC. _._.P. SNOBQNISH COUNTY r l?944 P1" ,; PARK 1 , ryf I j prSYy�. 3, i. PROJECT �/ ,+ PK � � j dA e Ti . �, a d a i d L HUTF "I ert,owreluBPdllp,nT ,i l'�db1ld53 SW�ms�drr�rP a.+} T'IW �,✓' dd�Akd S^d YAP I�, GNdii°Rtd SW.m.._ ,b9 M k J1i um rtl t r Iwos �yl $µp _ _ ....m.......... _ es d �a -—RRA w err e •.,.� yw rsa� ro _„!5,.' r” wY� ✓4 raw o errs ��T roar . e"q,F1` lT.�w ax f�xtlru.�ui �badw`,: r. d9da1'dd; Sl.. A'+LP ��TW q r MELODY, �. r �."M .,. LN 1 w< `� P6Sbu�'dm, E � &!&idf?R�Y � dk �S&I 1d 1, I �b� m � LL PA� �O i ��iY Ow� � .0 � ,91CNPA1tl�d;9hNlr 'i � '�^. 4}, !dTYI r ,A, 2t 'k,' ^wM�'v w, 2t u 1k ST q 1FidurW, .., wd ex �,,,,,_`at''a4Y,u�f�'dUY9B.�„�,..��..�..,:_� w, , r a cw «' rs :� wi, ,,,r uws�w Mrr w r <arm Tnda...""Q ,l BRACKETTS rdr „r xi11mck, Wv V MO LANDING �” fd�dR x ( �V SIERRA � � �F fw d dd 11�k y f a kr °9T 16P 2rleG '"•�av� sr u BEACH N gni da ttiRtpV tiYxF.VM �a {T't'M trmnttut r` 57pyel AVXw '� vaP d C p ? ANM"xd �dwi�p SPRAGUE fpy° ? roI !"dd>WNV6Tk y� �i✓RUo&aa j Mw iii 6n ' P&7 S"p IW0. 1^i3 8' 6R P W ' T ,.,d. m f r i a � K�" RI ra n e PK OPxPII $artriw9''R ..! !° na�P �edrdLw ri! 'r "° r f qAY 9FA ,y✓�'„�awWeo".s �ew � y ^n� YDST FI' �"p � hd�ry ,,..a"' aehrnr, ra n4 yr en¢k ^ ',.w.......-.�+�Y:M6pt ,'P' .epi Pd L al n n :I '� MMRIAL 8R yti .........,._., i. PARK ,_ P, UNION m ,,. .._. "�'.... . WAI.NOT,,. ..... ., a� ,�y�4�fit' OIL 1..., MARSH 9 NdkLl ,rpt as �d�Tii��,�� -^.� dAr °rca�s��6rPmc��`r�� 'I��"��86I� 5T�l �.�q.{�., l azarrsi s r sW d'w ,ryi9rt w ilsio 5+P . f sw �rlrtsD� "�C K15uNq� ^,r rd5r90 �v .�. .I PG�WC arard yr P 5 w Ru 1IF4k ., fiP 4k V !rom rl,_ P �N7�drr � T x .....e �mmm 4.... i.°....._ ,w .., .,.., ''dwr` „° .. VICINITY MAP LIU & ASSOCIATES, INC. 3 -LOT PLAT 87xx - 184TH STREET SW Geotechnical Engineering • Engineering Geology • Earth Science EDMONDS, WASHINGTON CONNECTION TO WATER MAIN, APPROXIMATE PROPOSED WATER METERS• CONNECT SEWER SERVICE--•- , Sb30h57,8. TH �.,. N ,8.....— 101+W __...,..._ ,.... SW RT)T� _ ST _ 1( L1N EXI IIN+� �.W Ir 184 Ik -_ w' 184TH ST W Q.._ 1 n Ex. 12- ET �EC2T§�'T" / c 5a3� 45 DEDICATION p.. STA 100+33.19 20'," DRAIpE (1.1.79 RT) �. EAgFMFw ' I ..:... cR 02 -M 8E1RkTNTdON 5Tp 1Tri0140 95 I POND 1 1717 In ...�_.�..�.. IPoor OOWN+OU1 I 12" CLEANOUL TYP PNE1TION ST4+5d.R7 O Q0,90 1) 10,472 SF —t TRACT 999...mw" 4.028 SF u1 E " SEWER SERVICE, 1"tP I ' C IT -.-Roo, 1 mA' :._Roo, DOWNSPOUT A CLEANOUT, TYP 1 LlI��RE'1EN'TYOrt� f 2 r" POND -.. f i T1sD�L I I I O k ® al 1q.088 SF —I ao I/j I� I I SEWER CLEANOUT. TTP— I _....777, ,.. �....'. .J.- J —7— 0M0REVENI ON ROOF 1YOWNiSPOUT POND CLEANOUT, TYP l ® u I 10,805 SF I I I 121' SITE AND EXPLORATION PLAN LIU & ASSOCIATES, INC. 3 -LOT PLAT 87xx - 184TH STREET SW Geotechnical Engineering • Engineering Geology • Earth Science EDMONDS, WASHINGTON JOB CSO, 16-121A DATE 10/30120161 UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP GROUP NAME SYMBOL GRAVEL CLEAN GW WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL COARSE- MORE THAN 50% OF GRAVEL GP 7POORLY-GRADED GRAVEL GRAINED COARSE FRACTION GRAVEL WITH GM SILTY GRAVEL SOILS RETAINED ON NO. 4 SIEVE FINES GC CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND MORE THAN 50% MORE THAN 50% OF SAND SP POORLY -GRADED SAND RETAINED ON THE COARSE FRACTION SAND WITH SM SILTY SAND NO. 200 SIEVE PASSING NO.4 SIEVE FINES SC CLAYEY SAND FINE- SILT AND CLAY INORGANIC ML SILT GRAINED�... LIQUID LIMIT CL CLAY SOILS LESS THAN 50% ORGANIC OL ORGANIC SILT, ORGANIC CLAY MORE THAN 50% SILTY AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT PASSING ON THE LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FAT CLAY NO. 200 SIEVE 50% OR MORE ORGANIC OH ORGANIC SILT, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT AND OTHER HIGHLY ORGANIC SOILS NOTES: SOIL MOI'STI I E MODIFIERS: 1. FIELD CLASSIFICATION IS BASED ON VISUAL EXAMINATION DRY - ABSENCE OF MOISTURE, DUSTY, DRY TO OF SOIL IN GENERAL ACCORDANCE WITH ASTM D2488-83. THE TOUCH 2. SOIL CLASSIFICATION USING LABORATORY TESTS IS BASED SLIGHTLY MOIST - TRACE MOISTURE, NOT DUSTY ON ASTM D2487-83. MOIST - DAMP, BUT NO VISIBLE WATER 3. DESCRIPTIONS OF SOIL DENSITY OR CONSISTENCY ARE VERY MOIST - VERY DAMP, MOISTURE FELT TO THE TOUCH BASED ON INTERPRETATION OF BLOW -COUNT DATA, VISUAL WET - VISIBLE FREE WATER OR SATURATED, APPEARANCE OF SOILS, AND/OR TEST DATA. USUALLY SOIL IS OBTAINED FROM BELOW WATER TABLE --SIU & ASSOC'[A,r S, INC. UNIFIED SOIL CLASSIFICATION SYSTEM Geotechnical Engineering , Engineering Geology - Earth Science PLATE 3 TEST PIT NO. 1 Logged By: JSL Date: 8/22/2016 Ground EI. f Depth USCS i Sample W Other ft. CLASS. Soil Description No, % Test OL Dark -brown, loose, organic, silty fine SAND, moist SM Light -brown, loose to medium -dense, silt fine SAN—, y D, trace to 2 some gravel, dry SM _Light -gray, very -dense, gravelly, silty, fine SAND, cemented, 4 slightly -moist (GLACIAL TILL) 5 6 7 SM Gray, dense, silty fine SAND, slightly -moist 9 (ADVANCE OUTWASH?) 10 11Test pit, terminated at 10.0 ft; groundwater not encountered. TEST PIT NO. 2 Logged By: JSL Date: 8/22/2016 Ground EI. t Depth LSCS Sample W Other ft, CLASS. Soil Description No. % Test _ OL Dark -brown, loose, organic, silty fine SAND, moist 1 2 SM I Light -brown, loose to medium -dense, silty fine SAND, trace gravel, dry 3 _ — SM Light -gray, very -dense, gravelly, silty, fine SAND, cemented, 4 slightly -moist (GLACIAL TILL) 5 — 6 7 8 9 10 I"est ifi terminated at 9.0 ft; groundwater not encountered. TEST PIT LOGS LIU & ASSOCIATES, INC. 3 -LOT PLAT 8710 - 184TH STREET SW Geotechnical Engineering • Engineering Geology - Earth Science EDMONDS, WASHINGTON SOB N0. 16-121 1 DATE 10/20/2016 1 PLATE 4 TEST PIT NO. 3 Logged By: JSL Date: 8/22/2016 Ground EI. t Depth us Sample W Other ft. CLASS. Soil Description No. % Test OL Dark -brown, loose, organic, silty fine SAND, dry (TOPSOIL) _ - SM - Light -brown, loose to medium -den, s. .. §- mmvseilty fine SAND, trace gravel, I 2 dry 3 4 _ SM _ Light -gray, very -dense, gravelly, silty, fine SAND, cemented, slightly -moist (GLACIAL TILL) 5 6 7 18 9 Test pit terminated at 8.0 ft; groundwater not encountered. 10 TEST PIT NO. 4 Logged By: JSL Date: 8/22/2016 Ground EI. ± Depth USCS Sample W Other tt CLASS. Soil Description No, % Test OL Dark -brown, loose, organic, silty fine SAND, dry SM _ Light-brown,,loose to medium -dense, silty fine SAND, trace gravel, 2 dry 3 4 5 SM Light -gray, very -dense, gravelly, silty, fine SAND, occasional ccasional ®� p cobble, cemented, slightly -moist (GLACIAL TILL) 6 7 8 9 10 11 1 Test pit terminated at 10.0 ft; groundwater not encountered. TEST PIT LOGS LIU & ASSOCIATES, INC. 3 -LOT PLAT 87xx -184TH STREET SW Geotechnical Engineering • Engineering Geology - Earth Science EDMONDS, WASHINGTON JOB NO. 16-121A DATE 10/20/2016 1 PLATE 5 SECTION 1C DOWNSTREAM FLOWPATH PHOTOGRAPHS 184`h Street Short Plat Drainage Report City of Edmonds,Property WGS 1984_ We b_ Mercator_AuxiliarySphere This ma p is a user gen-0 static —P— an rneu�ne� 1-111-1---•'v. reference only. Data layers that appear on this map nary ar nnaM nak. be accurate,,. current.3r J)t Genwi#'e rreinGle. THIS MAP IS NOT TO BE USED FOR DESIGN OR CONSTRUCTION egend ' Storm Catch Basins P Storm Manholes I Detention Facilities Culvert i. Facility Feature _ Creeks Storm Line Facility Lines Storm Ditch 1:4,514 Notes Downstream Analysis along 184"' Street SW, 71 -Vi ew looking west on the northeast corner Project Site and 184th Street SW. Runoff via sheet flow heads into an existing ditch along the north border of the project site. Due to the high vegetation, access onto the property was inaccessible. 784"' Street Short Plat Drainage Report ;h 1841h Street Short Plat Drainage Report 184"' Street Short Plat Drainage Report 1841h Street Short Plat Drainage Report 184'h Street Short Plat Drainage Report ..................... View looking southwest at the intersection of Olympic View Drive and Talbot Rd, northwest of Project Site. Stormwater enters a catch basin along the edge of Olympic View Drive and heads west into another catch basin on the shoulder of the road. View looking east at the intersection of Olympic View Drive and Talbot Rd, northwest of Project Site. Close-up view of catch basin as it heads southwest into a manhole off the shoulder of Olympic View Drive. View looking west on Olympic View Drive, northwest of Project Site. After exiting the manhole, the stormwater crosses Olympic View Drive and heads north. Due to thick vegetation and overgrowth, the manhole was not able to be identified along eastbound shoulder of Olympic View Drive. Note: The manhole does not connect into the catch basin shown, and is verified from the City of Edmonds Stormwater Inventory Map. 184"' Street Short Plat Drainage Report View looking east on Olympic View Drive, northwest of Project Site. Once the stormwater crosses Olympic View Drive, it enters another manhole located on this residential parcel (No. 27041800202400) that is adjacent to Talbot Road. Then the stormwater heads west to another manhole located on the same residential parcel. Due to thick vegetation and overgrowth, the both manholes were not able to be identified on both residential parcels, but are identified from the City of Edmonds Stormwater Inventory Map. View looking north on Olympic View Drive, northwest of Project Site. Stormwater continues into the residential parcel (No. 27041800202400) where it flows between Place SW, northwest of Project Site. two residential buildings before entering a manhole abutting the northwest corner of the After the stormwater exists the manhole from south building. Next the stormwater is routed ---� north to another manhole located on another the aforementioned residential parcel (No. residential parcel (No. 27041800202600), and keep continues north. 2741800202600), it enters a catch basin at the Due to thick vegetation and overgrowth, the ,, , both manholes were not able to be identified on start of the cul-de-sac on 179th Place SW. Next both residential parcels, but are identified from the City of Edmonds Stormwater Inventory Map. View looking west facing a cul-de-sac on 179°"' Place SW, northwest of Project Site. After the stormwater exists the manhole from ---� the aforementioned residential parcel (No. 2741800202600), it enters a catch basin at the ,, , start of the cul-de-sac on 179th Place SW. Next the stormwater enters a nearby manhole, and then heads northwest into a catch basin. K! pllr,l% 184th Street Short Plat Drainage Report P 184`h Street Short Plat Drainage Report V-��. View looking west facing acul-de-sac on 179 Place SW„ northwest of Project Site. The stormwater enters the catch basin and is routed north to a manhole located at the northwest corner of a residential parcel (No. 00459000000400). View looking south on 178 Place SW, northwest of Project Site. After the stormwater exits the manhole from the aforementioned residential parcel (No. 00459000000400)„ it heads north to another manhole located on 178`x' Place SW in front of a residential driveway. View looking west on 178' Place SW, northwest of Project Site. Then the stormwater is then routed northwest through a series of more manholes where it finally discharges into Puget Sound. Note: The remaining manholes are identified from the City of Edmonds Stormwater Inventory Map. SECTION 2 MINIMUM REQUIREMENT #2 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN 1841' Street Short Plat Drainage Report CSWPPP AnlNilsii1s�and De�s This section, along with the Temporary Erosion and Sediment Control (TESC) Plan contained in the engineering drawings, is intended to serve as the construction Stormwater Pollution Prevention Plan (SWPPP) for the project, The SWPPP is outlined in conformance with the 2005 edition of the it Manual for Western WaShin Washington State Department of olog Ecy's (DOE Manual). 1.0 —INTRODUCTION An introductory overview of the project has been provided in the Executive Summary of this report. 2.0 —SITE DESCRIPTION A general site description has been provided in the Executive Summary of this report. Additional detailed information is provided through the rest of this report. 3.0 — CONSTRUCTION STORMWATER BMPs 3.1 —12 BMP ELEMENTS Element #1— Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land -disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans, In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible, The BMPs relevant to marking the clearing limits are identified in Appendix 2B. Alternate BMPs for marking clearing limits are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPIDES Permit (Appendix 2D), To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing, Element #2 — Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points Shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. All wash wastewater shall be controlled on site. The specific BMPs related to establishing construction access that will be used on this project are identified in Appendix 2B. Alternate construction access BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 2D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and, Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. 184"' Street Short Plat Drainage Report Element #3 - Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project are identified in Appendix 2B. Alternate flow control BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth to the General NPDES Permit. To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Storrnwater permit„ the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. In general, discharge rates of stormwater from the site will be controlled where increases in impervious ,area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements (e.g, discharge to combined sewer systems). Element #4 - Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged to an infiltration facility. The specific BMPs to be used for controlling sediment on this project are identified in Appendix 2B. Alternate sediment control BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 2D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified 'Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs at the first sign that existing BMPs are ineffective or failing. In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize wash off of sediments from adjacent streets in runoff. Whenever possible, sediment laden water shall be discharged into onsite, relatively level, vegetated areas (BMP C240 paragraph 4, Volume II page 116). In some cases, sediment discharge in concentrated runoff can be controlled using permanent stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment loads can limit the effectiveness of some permanent stormwater BMPs, such as those used for infiltration or biofiltration; however, those BMPs designed to remove solids by settling (wet ponds or detention ponds) can be used during the construction phase. When permanent stormwater BMPs will be used to control sediment discharge during construction, the structure will be protected from excessive sedimentation with adequate erosion and sediment control BMPs. Any accumulated sediment shall be removed after construction is complete and the permanent stormwater BMP will be restabilized with vegetation per applicable design requirements once the remainder of the site has been stabilized. 184`h Street Short Plat Drainage Report Element #5 - Stabilize Soils Exposed and unworked soil's shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project are identified in Appendix 2B. Seeding will be used on disturbed areas that have reached final grade or that will remain unworked for more than thirty days. Plastic Covering will be used on the temporary stock pile areas and elsewhere on the site as needed. Gust control will be implemented as needed, to prevent it being required all roadways and driveways to be paved will receive early application of gravel base. Alternate soil stabilization BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 2D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and unworked for more than 7 days during the dry season (May 1 to September 0) and 2 days during the wet season (October I to April ), Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting, All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. Element #6 - Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes erosion. The specific BMPs that will be used to protect slopes for this project are identified in Appendix 2B. Alternate slope protection BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 2D), To avoid potential erosion and sediment control issues that may cause a violation of the NPDiES Construction Stormwater permit, the Certified Erosion and Sediment Control bead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. Element #7 - Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment -laden runoff on and near the project site. The inlet protection measures to be applied on this project are identified in Appendix 2B. 184"' Street Short Plat Drainage Report If the primary BMP options are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPI ES Permit (Appendix 2D), or if no BMPs are listed above but deemed necessary during construction, the Certified Erosion and Sediment Control Lead shall implement one or more of the alternative BMP inlet protection options. Element #8 - Stabilize Channels and Outlets Where site runoff is to be conveyed in channels, or discharged to a Stream or some other natural drainage point, efforts will be taken, to prevent downstream erosion. The specific BMPs, for channel and outlet stabilization that shall be used on this project are identified in Appendix 2B. Alternate channel and outlet stabilization BMPs are included in Appendix 2C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPIDES Permit (Appendix 2D), To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest, As such, all temporary on- site conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the expected peak 10 minute velocity of flow from a Type 1A, 1g -year, 24-hour recurrence interval storm for the developed condition. Alternatively, the 10 -year, 1 -hour peak flow rate indicated by an approved continuous runoff simulation model, increased by a factor of 1.S„ shall be used, Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches shall be provided at the outlets of all conveyance systems, Element #9 - Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well -organized, and free of debris. Any required BMPs to be implemented to control specific sources of pollutants are identified in Appendix 2B. The contractor shall implement the following measures as much as is practicable, in order to mitigate pollutant impacts from vehicles, construction equipment, and/or petroleum product storage/dispensing: • All vehicles, equipment, and petroleum product storage/dispensing, areas will be inspected regularly to detect any leaks or spills, and, to identify maintenance needs to prevent leaks or spills. • On-site fueling tanks and petroleum product storage containers shall include secondary containment. • Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment. • In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle. 184" Street Short Plat Drainage Report • Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. • The contractor shall implement the following concrete and grout pollution control measures: • Process water and slurry resulting from concrete work will be prevented from entering the waters of the State by implementing Concrete Handling measures (BMP C151). The contractor shall implement the following Solid Waste pollution control measures: • Solid waste will be stored in secure, clearly marked containers. Element #10 - Control Dewatering Foundation, vault, and trench de -watering water, which shall have similar characteristics to stormwater runoff at the site, shall be discharged into a controlled conveyance system prior to discharge to a sediment trap, pond, or other specified facility. Channels must be stabilized as specified in Element #8. Clean, non -turbid de -watering water, such as well -point groundwater, can be discharged to systems tributary to state surface waters, provided the de -watering flow does not cause erosion or flooding of receiving waters. These clean waters should not be routed through stormwater sediment ponds. Highly turbid or contaminated dewatering water shall be handled separately from stormwater. Element #11- Maintain BMPs All BMPs should be monitored and maintained regularly to ensure adequate operation. A TESC supervisor shall be identified at the beginning of the project to provide monitoring and direct the appropriate maintenance activity. As site conditions change, all BMPs shall be updated as necessary to maintain compliance with local regulations. Temporary BMPs can be removed when they are no longer needed. All temporary erosion and sediment control BMPs shall be removed within 30 days after construction is completed and the site is stabilized. Element #12 - Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles: • Design the project to fit the existing topography, soils, and drainage patterns. • Emphasize erosion control rather than sediment control • Minimize the extent and duration of the area exposed. • Keep runoff velocities low. • Retain sediment on site. • Thoroughly monitor site and maintain all ESC measures 184"' Street Short Plat Drainage Report • Schedule major earthwork during the dry season As this project site is located west of the Cascade Mountain Crest, the project will be managed according to the following key project components: Phasin of Construction • The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible, the transport of sediment from the site during construction. • Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities during each phase of construction, per the Scheduling BMP (C 162). Seasonal Work Limitations • From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt - laden runoff will be prevented from leaving the site through a combination of the following: o Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and o Limitations on activities and the extent of disturbed areas; and o Proposed erosion and sediment control measures. Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The following activities are exempt from the seasonal clearing and grading limitations: o Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and o Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. Coordination with Utilities and Other Jurisdictions • Care has been taken to coordinate with utilities, other construction projects, and the local jurisdiction in preparing this SWPPP and scheduling the construction work. Inspection and. Monitoring All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: o Assess the site conditions and construction activities that could impact the quality of stormwater, and o Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. 780' Street Short Plat Drainage Report • A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times. • Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. 1116TOUTTIT904TAINTIN :22 • This SWPPP shall be retained on-site or within reasonable access to the site • The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. • The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. 3.2 — SITE SPECIFIC BMPs Site specific BMPs are shown on the TESC plan sheet(s) in Appendix 2A, 4.0 — CONSTRUCTION PHASING AND BMP IMPLEMENTATION The BMP implementation schedule will be driven by the construction schedule. The list below provides an estimate of the anticipated construction schedule. The project site is located west of the Cascade Mountain Crest. As such, the dry season is considered to be from May 1 to September 30, and the wet season is considered to be from October 1 to April 30. 5.0 — POLLUTION PREVENTION TEAM 5.1 ROLES AND RESPONSIBILITIES The pollution prevention team consists of personnel responsible for implementation of the SWPPP, including the following: • Certified Erosion and Sediment Control Lead (CESCL) — primary contractor contact, responsible for site inspections (BMPs, visual monitoring, sampling, etc.); to be called upon in case of failure of any ESC measures. • Resident Engineer — For projects with engineered structures only (sediment ponds/traps, sand filters, etc.): Site representative for the owner that is the project's supervising engineer responsible for inspections and issuing instructions and drawings to the contractor's site supervisor or representative. • Emergency Ecology Contact — Individual to be contacted at Ecology in case of emergency. • Emergency Owner Contact — Individual that is the site owner or representative of the site owner to be contacted in the case of an emergency. • Non -Emergency Ecology Contact — Individual that is the site owner or representative of the site owner that can be contacted if required. 184'h Street Short Plat Drainage Report • Monitoring Personnel — Personnel responsible for conducting water quality monitoring; for most sites this person is also the CESCL. 5.2 TEAM MEMBERS Names and contact information for those identified as members of the pollution prevention team are provided in the project summary in Appendix 213. 6.0 — SITE INSPECTIONS AND MONITORING Monitoring includes visual inspection, monitoring for water quality parameters of concern, and documentation of the inspection and monitoring findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements; • Site inspections; and, • Stormwater quality monitoring. For convenience, the inspection forma and water quality monitoring forms included in Appendix 2E of this report include the required information for the site log book. This SWPPP may function as the site log book, if desired, or the forms may be separated and included in a separate site log book. However, if separated, the site log book must be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 6.1 SITE INSPECTION All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead (CESCL) per BMP C160. The name and contact information for the CESCL is provided in Section 5 of this SWPPP. Site inspection will occur in all areas disturbed by construction activities and at all stormwater discharge points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be documented in the site log book or forms provided in this document. All new BMPs or design changes will be documented in the SWPPP as soon as possible. 6.1.1 Site Inspection Frequency Site inspections will be conducted at least once a week and within 24 hours following any rainfall event which causes a discharge of stormwater from the site. For sites with temporary stabilization measures, the site inspection frequency can be reduced to once every month. 6.1.2 Site Inspection Documentation The site inspector will record each site inspection using the site log inspection forms provided in Appendix 2E. The site inspection log forms may be separated from this SWPPP document, but will be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 184'h Street Short Plat Drainage Report 6.2 Stormwater Quality Monitoring 6.2.1 Turbidity Sampling Monitoring requirements for the proposed project will include turbidity sampling to monitor site discharges for water quality compliance with the 2010 Snohomish County Drainage manual and Snohomish County Code Title 30,63A NPDES Construction Stormwater General Permit (Appendix 2D). Sampling will be conducted at all site discharge points at least once per calendar week. Turbidity monitoring will follow the analytical methodologies described in Section S4 of the 2005 Construction Stormwater General Permit (Appendix 2D), The key benchmark values that require action include 25 NTU and 250 NTU for turbidity. If the 25 NTU benchmark for turbidity is exceeded, the following steps will be conducted: 1. Ensure all BMPs specified in this SWPPP are installed and functioning as intended. 2. Assess whether additional BMPs should be implemented and make revisions to the SWPPP as necessary. 3. Sample the discharge location daily until the analysis results are less than 25 NTU (turbidity) or 32 cm (transparency). If the turbidity is greater than 25 NTU but less than 250 NTU for more than 3 days, additional treatment BMPs will be implemented within 24 hours of the third consecutive sample that exceeded the benchmark value, Additional treatment BMPs will include, but are not limited to, off-site treatment, infiltration, filtration and chemical treatment. If the 250 NTU benchmark for turbidity is exceeded at any time, the following steps will be conducted: 1. Notify Ecology by phone within 24 hours of analysis. 2. Continue daily sampling until the turbidity is less than 25 NTU. 3. Initiate additional treatment BMPs such as off-site treatment, infiltration, filtration and chemical treatment within 24 hours of the first 250 NTU exceedance. 4, Implement additional treatment BMPs as soon as possible, but within 7 days of the first 250 NTU exceedance. 5. Describe inspection results and remedial actions that are taken in the site log book and in monthly discharge monitoring reports. 6.2.2 pH Sampling Stormwater runoff will be monitored for pH starting on the first day of any activity that includes more than 40 yards of poured or recycled concrete, or after the application of "Engineered Soils" such as, Portland cement treated base, cement kiln dust, or fly ash. This does not include fertilizers. For concrete work, pH monitoring will start the first day concrete is poured and continue until 3 weeks after the last pour. For engineered soils, the pH monitoring period begins when engineered soils are first exposed to precipitation and continue until the area is fully stabilized. 184`" Street Short Plat Drainage Report Stormwater samples will be collected daily from all points of discharge from the site and measured for pH using a calibrated pH meter, pH test kit, or wide range pH indicator paper. If the measured pH is 8.5 or greater, the following steps will be conducted: 1. Prevent the high pH water from entering storm drains or surface water. 2. Adjust or neutralize the high pH water if necessary using appropriate technology such as CO2 sparging (liquid or dry ice). 3. Contact Ecology if chemical treatment other than CO2 sparging is planned. 7.0 — REPORTING AND RECORDKEEPING 7.1 RECORDKEEPING 7.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements; • Site inspections; and, • Stormwater quality monitoring For convenience, the inspection form and water quality monitoring forms included in Appendix 2E of this report include the required information for the site log book. 7.1.2 Records Retention Records of all monitoring information (site log book, inspection reports/checklists, etc.), this Stormwater Pollution Prevention Plan, and any other documentation of compliance with permit requirements will be retained during the life of the construction project and for a minimum of three years following the termination of permit coverage in accordance with permit condition S5.C. 7.1.3 Access to Plans and Records The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be retained on site or within reasonable access to the site and will be made immediately available upon request to Ecology or the local jurisdiction. A copy of this SWPPP will be provided to Ecology within 14 days of receipt of a written request for the SWPPP from Ecology. Any other information requested by Ecology will be submitted within a reasonable time. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with permit condition S5.G. 7.1.4 Updating the SWPPP In accordance with Conditions S3, S4.6, and S9.6.3 of the General Permit, this SWPPP will be modified if the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site or there has been a change in design, construction, operation, or maintenance at the site that has a significant effect on the discharge, or potential for discharge, of pollutants to the waters of the State. The SWPPP will be modified within seven days of determination based on inspection(s) that 1841' Street Short Plat Drainage Report additional or modified BMPs are necessary to correct problems identified, and an updated timeline for BMP implementation will be prepared. 7.2 REPORTING 7.2.1 Discharge Monitoring Reports Discharge Monitoring Report (DMR) forms will not be submitted to Ecology because water quality sampling is not being conducted at the site. 7.2.2 Notification of Noncompliance If any of the terms and conditions of the permit are not met, and it causes a threat to human health of the environment, the following steps will be taken in accordance with permit section S5.F: 1. Ecology will be immediately notified of the failure to comply. 2. Immediate action will be taken to control the noncompliance issue and to correct the problem. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. In accordance with permit condition S2.A, a complete application form will be submitted to Ecology and the appropriate local jurisdiction (if applicable) to be covered by the General Permit. 184"' Street Short Plat Drainage Report APPENDIX 2A SITE PLAN WITH BMP MEASURES 184`h Street Short Plat Drainage Report no Z 0 184TH STSHORT PLAT cn.ne %DaE G geiee"tp �,W 4�,� ° aos m aswsio"s . . E. A98i13 '� S G N ... Plan �Mon�smenf rruw manse vow om.. wne l+o ew�n. wa:n'ngron vezoi m� " m.. ear n ,Y O T.E.S.G. GRADING 8 TREE RETENTION PLAN f .....,.,..„.. ” _ aA ay sua rwluA.a_ 77 . dtl3. Nm, I' p U- MI f .".. woswuo ..— meow N V'983L6:eyO S" IV 30 V S3 ON ... ova a3w CV9 S © tOZ86 uolBuiycoM'Nalay pyt ak�S uq x. Ja?AW'M 6211 ...... �,, �.' ooaz xte (sozl .....woo l�od �„ awdMa,u�s lbld 12i0HS'1S HIM _ w a do rxva MUL> ....— ... nu M.. a�le�l o•- c c e �rc^ 1q' w 3 f vm- y m 1 1 a 4 a i n Y 'v of o 11 z Lu OIL � W z im 6 AU oo n n s a q� e o iF,esu a e lnN w ora�7s a %�a �w o a u s oa 2_ s o _ U i. b "G ua z 's a Rag g m 3 I— s 10 1 o c m wy ` �4 m �+ ' zk �% �" rn w iZ6 .z- gg a � In-sao l s � a - ` ass s s � ayd 3 HE X 02 'zi_ 3� c s s HER 9i 99 H T & s 4 921 1s$ Q =gar ps w 69 � a m<, s �a € e s e �' a ZO aAlW 3P'i K�a4 x 21, ss XS. Ro Qo �� s�2 4 E<om < ��_� ��mo „ .:A..4 HvAg &p MEN. ��w G� $ Meg V2. �ma! � N N m ry n < n m r m w - Buouyig :Rd Vaim5 15>, WY£Z:OI — LtilZ 'bL auy, APPENDIX 2B SWPPP PROJECT SUMMARY 184`h Street Short Plat Drainage Report MONITORING 'IiE�R dNNEL TO BE ASSIGNED AT THE PRE -CONSTRUCTION MEETING AND ADDED TO THE TABLE ABOVE lmll6za q,', • Construction Start Date TBD • Install ESC Measures TBD • Construction End Date TBD • High Visibility Plastic or Metal Fence (BMP C103) • Silt Fence (BMP C233) • Storm Drain Inlet Protection (BMP C220) • Detention Pond Or Vault • Plastic Covering (BMP C123) • Topsoiling (BMP C125) • Dust Control (BMP C10) • Early application of gravel base on areas to be paved • Temporary and Permanent Seeding (BMP C120) • Interceptor Dike and Swale (BMP C2�00) • Materials on Hand (BMP C150) may also be applicable • Grass -Lined Channels (BMP C201) • Check Dams (BMP C207) • Straw Wattles (BMP C235) 184'h Street Short Plat Drainage Report APPENDIX 2C ALTERNATIVE BMPs 184`" Street Short Plat Drainage Report The following includes a list of possible alternative BMPs for each of the 12 elements not described in the main SWPPP text. This list can be referenced in the event a BMP for a specific element is not functioning as designed and an alternative BMP needs to be implemented. Element #1 - Mark Clearing Limits • High Visibility Plastic or Metal Fence (BMP C103) Element #2 - Establish Construction Access • Wheel Wash (BMP C106) Element #3 - Control Flow Rates • (none) Element #4 - Install Sediment Controls • Straw Bale Barrier (BMP C230) • Vegetated Strip (BMP C234) • Materials on Hand (BMP C150) Element #5 - Stabilize Soils • Dust Control (BMP C140) • Topsoiling (BMP C125) • Sodding (BMP C124) Element #6 - Protect Slopes • Straw Wattles (BMP C235) • Grass -Lined Channels (BMP C201) Element #7 - Protect Drain Inlets • (none) Element #8 - Stabilize Channels and Outlets • Level Spreader (BMP C206) Element #10 - Control Dewatering • (none) 184th Street Short Plat Drainage Report APPENDIX 2D GENERAL PERMIT 184"' Street Short Plat Drainage Report Element 3: Control Flowrates BMP: Location Inspected Functioning -[ problem/Corrective Action 1--T—Y-FN71—YTN-1 NIP BMP: Location Inspected Functioning problem/Corrective Action Y N Y N NIP Element 4: Install Sediment Controls BMP: Location Inspected �Fu��—c—t�iojjnii:n:pi Problem/Corrective Action Y N NI BMP: Location Inspected FFunctioning problem/Corrective Action Y N N NIP Element 5: Stabilize Soils DRAD• Location Inspected Y N Functioning Problem/Corrective Action -T—N NIP BMP:. Location Inspected Fun�Nl problem/Corrective Action Y N Yj .............. 184`h Street Short Plat Drainage Report Element 6: Protect Slopes BMP: Inez Location � r BMP: Functionin Problem/Corrective Action Y 1 N NIP1 inspected Functinoin Location Problem/Corrective Action Y N Y N Element 7: Protect Drain Inlets BMP: Ins ected Functionin Problem/Corrective Action Location v N Y N NIP BMP: Inspected Functioning problem/Corrective Action Location Y N 7—N NIP Element 8: Stabilize Channels and Outlets BMP:. Ins acted FuWN n Problem/Corrective Action Location v N Y IP BMP: P71ns fte Functionin Problem/Corrective Action Location Y N NIP 184"' Street Short Plat Drainage Report Element 9: Control Pollutants BMP: BMP: In ected Functionin Problem/Corrective Action Location Y N Y N NIP Element 10: Control Dewatering BMP: Ins eted. Functionin' Problem/Corrective Action Location v N Y N NIP BMP: TMProblem/Corrective Action Location 184" Street Short Plat Drainage Report Water Qualit Monitorin Was any water quality monitoring conducted? ❑ Yes ❑ No If water quality monitoring was conducted„ record results here: If water quality monitoring indicated turbidity 250 NTU or greater; or transparency 6 cm or less„ was Ecology notified by phone within 24 hrs? ❑ Yes ❑ No If Ecology was notified, indicate the date, time, contact name and phone number below: Date: Time: Contact Name: Phone #: General Comments and Notes Include BMP repairs, maintenance, or installations made as a result of the ins ection, Were Photos Taken? ❑ Yes ❑ No If�aken, describe hotos below: 184`" Street Short Plat Drainage Report SECTION 3 MINIMUM REQUIREMENT #3 SOURCE CONTROL OF POLLUTION 18e Street Short Plat Drainage Report Source orttrol off Pollution The project is not classified as a high -use site, and no hazardous materials requiring source control BMPs are proposed to be stored on-site. 184"' Street Short Plat Drainage Report SECTION 4 MINIMUM REQUIREMENT #4 PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS 784"' Street Short Plat Drainage Report PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS The existing site topography falls towards north towards 184th Street SW, and the runoff is collected in a shallow ditch heading west. Once intersecting with 88th Ave SW, the runoff enters an underground conveyance system and heads north where it ultimately discharges into Puget Sound. The project is proposing the use of bioretention facilities that will detain and treat the majority of runoff before infiltrating into the native soil below. The remaining runoff will bypass detention and will be collected into the proposed conveyance system along 184th Street SW where it will connect with the existing flowpath. This project is not expected to adversely impact drainage features further downstream. 184th Street Short Plat Drainage Report SECTION 5 MINIMUM REQUIREMENT #5 ON-SITE STORMWATER MANAGEMENT 184`h Street Short Plat Drainage Report Existing Site Hydrology The project site is an undeveloped lot occupying approximately 0.86 acres and contains native vegetation. The underlying topography falls moderately to the north, and surface runoff can be expected to drain northernly via sheet flow towards the existing roadside ditch along the south side of 184th Street SE. For stormwater modeling purposes, the site is considered to be fully forested in the existing condition. Developed Site Hydrology The project proposes the construction of 3 single family residential lots, and aims to maintain similar drainage patterns to those that currently exist. The project is proposing a permeable road on the west edge of the project allowing vehicle access for each single family home with the use of permeable driveways. Roof and driveway runoff will be detained in a bioretention facility. Any overflow from the bioretention facilities will be routed north where it will be collected into the proposed conveyance system along 184th Street SW. It is not feasible to collect all of the proposed impervious area along the frontage due to grade. Per Department of Ecology's flow control requirements, the remaining runoff will bypass detention and will flow west away from the project site along 184th Street SW where it will ultimately discharge into Puget Sound. Performance Standards The project is subject to the provisions of Chapter 18.30 of the City of Edmonds' Stormwater Code Supplement to Edmonds Community Develop Code, which is supplemented from the Washington State Department of Ecology's (DOE) 2005 Stormwater Manual for Western Washington (SMMWW). Hydrologic modeling calculations for flow control and water quality treatment design were performed using MGS Flood and WWHM2012. MGS Flood is a general, continuous, rainfall -runoff computer model developed specifically for stormwater facility design in Western Washington. MGS Flood evaluates several decades of hydrologic data to derive peak flowrate and duration information. WWHM2012 is a locally calibrated continuous runoff simulation model developed in accordance with the Washington State Department of Ecology's regulations for stormwater facility design in Western Washington, which evaluates several decades of hydrologic data to derive peak flow rate and duration information. Low Impact Development (LID) Evaluation The City of Edmonds' Stormwater Code Supplement requires the evaluation of low -impact stormwater management solutions as part of the stormwater management design. Infiltration is the preferred low - impact stormwater management solution. It was evaluated that a bioretention facility is feasible on the project site and a geotechnical report provided acceptable infiltration rates greater than 0.5 in/hr. Rainwater harvesting is not generally thought to be a feasible stormwater management option for plat projects, because of the storage volume that is required to be collected during the prolonged wet -season in the Pacific Northwest. 784th Street Short Plat Drainage Report u� 99+00 100+00 1O1f00_ HYDROLOGIC MODELING . . . ~~.^~~._~~~=.~, .°.~,~~~~~.,.~~� � III BASIN 'B' SUMMARY IMPERVIOUS ROOF AND DRIVEWAY AREA = 0.07 AC TOTAL BASIN 'B' AREA = 0.09 AC BASIN 'C' SUMMARY � IMPERVIOUS ROOF AND DRIVEWAY AREA = 0.07 AC �| TOTAL BASIN 'C' AREA = OOQ AC REMAINING LANDSCAPE/LAWN = O4O AC , ]O�' O 100'{)' - ' 1 = - BYPASS: Scale Feet ID ROADS/SIDEWALKS = 0.05 AC LAWN = 0.03 AC 0 TOTAL BYPASS BASIN AREA �U TOTAL PROJECT AREA = 0.19 f 0.09 f 0.09 f 0.45 f 0.08 AC = 0.91 AC DETAINED: BASIN 'A' SUMMARY Design TPH Civil Englneedng Project Management OL IMPERVIOUS ROOF = 0.07 AC � PERMEABLE DRIVEWAY = 0.02 AC 05/17/17 ffa—te PERMEABLE ACCESS ROAD 0.10 AC 'd TOTAL BASIN 'A' AREA 0.19 AC 02 Project No. � III BASIN 'B' SUMMARY IMPERVIOUS ROOF AND DRIVEWAY AREA = 0.07 AC TOTAL BASIN 'B' AREA = 0.09 AC BASIN 'C' SUMMARY � IMPERVIOUS ROOF AND DRIVEWAY AREA = 0.07 AC �| TOTAL BASIN 'C' AREA = OOQ AC REMAINING LANDSCAPE/LAWN = O4O AC , ]O�' O 100'{)' - ' 1 = - BYPASS: Scale Feet ID ROADS/SIDEWALKS = 0.05 AC LAWN = 0.03 AC 0 TOTAL BYPASS BASIN AREA �U TOTAL PROJECT AREA = 0.19 f 0.09 f 0.09 f 0.45 f 0.08 AC = 0.91 AC TPH Design TPH Civil Englneedng Project Management 184TH ST. SHORT PLAT 1" = 100' Scale -u' Drawn Planning 05/17/17 ffa—te 1724 W. Marine Mew Drive, Suite 140; Evereti, Washington 96201 DEVELOPED 291-016-16 Office: 425,486,6533 F= 425.486,65Y3 w— sdoengineem com FIGURE 02 Project No. Figure No. SECTION 6 MINIMUM REQUIREMENT #6 RUNOFF TREATMENT 180 Street Short Plat Drainage Report Runoff Treatment The project is subject to Basic Treatment requirements, as outlined by Minimum Requirement #6 in the DOE°s SWMMWW'. The project is proposing the use of bioretention facilities that will detain and treat the majority of runoff before infiltrating into the native soil beneath ground level, The bioretention facility design was referenced from the LID Manual per the City of Edmonds Stormwater Code 'Supplement and the Low Impact Development: Technical Guidance Manual for Puget Sound. Permeable pavement is proposed for the access road and driveways on the project site, and is considered a pollution generating pervious surface (PGPS), However per Section 16.36.666 from the City of Edmonds' Stormwater code, permeable pavements do not require the construction of stormwater treatment facilities. For the bioretention facility, a layer of the bioretention soil will be the main mechanism that will treat stormwater before infiltrating into the subsurface soil. A saturated hydraulic conductivity of 6 inches per hour was used to model the bioretention soil. From the geotechnical study, it was recommended that the estimated infiltrated rate for Lot 1, 2, and 3 is approximately 1.23, 1,41, and 0.54 respectively where it would incorporated in the runoff analysis. The water quality flow rates for each bioretention facility have been calculated using MGS Flood, and was used to determine the appropriate size for each basin area. Each lot will have a bioretention facility that will capture and treat any roof and driveway runoff respected to that area. Portions of the access road will be routed to the bioretention facility located on Lot 1 while the remaining will bypass the project site. The water quality flow rates for each area have been calculated using MGS Flood and are provided in Appendix 6A. Overall basin figures have been provided in Appendix 5A of this report. 180 Street Short Plat Drainage Report Basin B Water Quality Design Calculations (MISS Flood documentation in Appendix 7A) Water Quality Data Compute Water Quality Treatment Volume for Link Computed Basic Wet Pond Volume, 91% Exceedance (cu -ft): V f of srmp rked ..,��... m uted Computed Large Wet Pond Volume (Phosphorous Control),1.5'Basic Volume (cu -ft): Not Co..P Time to Infiltrate 91 % Treatment Volume, [Applies to Infiltration Facilities] Not Computed optrationJFiltration Statistics Btics 67Total Runoff Volume acl Percent Treated 100 40� (Infiltrate dreatered)lTotal ____.... -u ..... Total Runoff Infiltrated 28 67 ac -ft 100 00 a Total Runoff Filtered --...V.�O..a° ft�0.00 0.4.. Compute 2 -yr Discharge Rate for Link Outflow (cfs) 0.000 0 Compute Water Quality 15 -Minute Design Discharge for Link Inflow On -Line Facility Design Discharge Rate [cfs]: Off -Line Facility Design Discharge Rate (cfs): p 0.005 Close 184`h Street Short Plat Drainage Report Basin C Water Quality Design Calculations (MGS Flood documentation in Appendix 7A) ...n -_.....a.._......... ............ ..� �..-..._._. Water QualityData Compute Water Quality Treatment Volume for Link Computed Basic Wet Pond Volume, 91% Exceedance (cu -ft): Not Computed Computed Large Wet Pond Volume (Phosphorous Control), 1,5'BasicVolume (cu -ft): Not Computed a l.._...apaaga#, Time to Infiltrate 91 %Treatment Volume, (Applies to Infiltration Facilities] Clot CK Compute Statistics D Total RunoffVolume3d p1 -a-CM Percent Treated Filtered]1Tokal . Total Runoff Infiltrated 3q X11 ac -ft . 7 ChCf BSD Total Runoff Filtered BD ac ft 0 ��D 0 Compute 2 -yr Discharge Rate for Link Outflow (cfs) J Compute Water Quality 15 -Minute Design Discharge for Link Inflow On -Line Facility Design Discharge Rate (cfs)tf f99 Off -Line Facility Design Discharge Rate (cfs): .,,,..11--._B ""1 Close 1841' Street Short Plat Drainage Report SECTION 7 MINIMUM REQUIREMENT #7 FLOW CONTROL 184`h Street Short Plat Drainage Report Flow Control System Flow control for this project will be provided with the use of a total of 3 bioretention facilities located on the property. The bioretention facility will collect and infiltrate the roof runoff underground to meet flow control requirements. The bioretention facilities will be sized to ensure that the develop rates match the predeveloped rates. From the geotechnical report, it states that the property is mantled by 3-4' thick of outwash soil underlain by with till soil. A ponding depth of 6in and a bioretention soil mix thickness of 18in were modeled in our calculations to accommodate with the constraints in soil depth. The bioretention facilities were modeled in MGSFIood and the calculations have been provided in Appendix 7A of this report. Permeable pavement will be used for the access road and driveways and will infiltrate into the subgrade native soil. The permeable pavement was designed by referencing the City of Edmonds' Stormwater code and the 2012 Low Impact Development Technical Guidance Manual for Puget Sound. The permeable pavement was modeled in WWHM 2012 to ensure that the amount of area was capable of infiltrating 100% of the runoff. Based from the location of the permeable pavement, an infiltration rate of 1.23 inches per hour was selected as it would be a conservative rate per the geotechnical report. The WWHM 2012 calculations are provided in Appendix 7A of this report. It is not feasible to collect and treat all the access road and the impervious area along the frontage due to grade. However, the SMMWW provides an exception to this requirement if the 100 -yr peak runoff from the project's target surfaces does not increase by more than 0.4-cfs as a result of the proposed development. It was calculated that the 100 -peak discharge from the bypass area is less than 0.1 cfs. Therefore the runoff will bypass the facility and connect with the existing conveyance system along 184tH Street SW. Basin mapping that depicts the existing and proposed hydrologic conditions are provided in Appendix 5A. The MGS Flood and WWHM2012 calculations are provided in Appendix 7A. 184th Street Short Plat Drainage Report MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.40 Program License Number: 201110001 Project Simulation Performed on: 05/17/2017 10:51 AM Report Generation Date: 05/17/2017 10:51 AM Input File Name: 2017-05-16 Rain Garden Lot 2.fld Project Name: Edmonds Plat Analysis Title: Rain Garden Analysis Comments: Basin 2, hydrolic connectivity as 6in/hr PRECIPITATION INPUT Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 0 Full Period of Record Available used for Routing Precipitation Station : 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default Default HSPF Parameters Used (Not Modified by User) ********************** WATERSHED DEFINITION *****«««««««««««««««««« Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.070 0.070 Area of Links that Include Precip/Evap (acres) 0,000 0.003 Total (acres) 0.070 0.073 ------------ --•-•SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin B ---------- ------- Area (Acres) -------- Till Forest 0.070 ------- ---- Subbasin Total 0.070 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin B ---------- ------- Area (Acres) -------- Impervious 0.070 ---------------------------------- Subbasin Total 0.070 ***R*************#**#*k#* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 *************R********#*# LINK DATA ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 184"' Street Short Plat Drainage Report Link Name: Rain Garden Link Type: Bioretention Facility Downstream Link: None Base Elevation (ft) 100.00 Riser Crest Elevation (ft) 100.50 Storage Depth (ft) 0.50 Bottom Length (ft) 30.0 Bottom Width (ft) 4.0 Side Slopes (ft/ft) „ L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq -ft) : 120. Area at Riser Crest EI (sq -ft) : 231. (acres) 0.005 Volume at Riser Crest (cu -ft) : 159. (ac -ft) 0.004 Infiltration on Bottom and Sideslopes Selected Soil Properties 1.50 Biosoil Thickness (ft) Biosoil Saturated Hydraulic Conductivity (in/hr) 6.00 Biosoil Porosity (Percent) 40.00 Maximum Elevation of Bioretention Soil : 101.50 Native Soil Hydraulic Conductivity (in/hr) 1.41 Riser Geometry Riser Structure Type Circular Riser Diameter (in) : 6.00 Common Length (ft) 0.000 Riser Crest Elevation 100.50 ft Hydraulic Structure Geometry Number of Devices: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ..................... SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 **Groundwater Recharge Summary Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge Dearing Simulation Model Element Recharge Amount (ac -ft) Subbasin: Basin B 10.698 Total: _ 10.698 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac -fl) Subbasin: Basin B___. 0.000 Link: Rain Garden 28.667 Total: 28.667 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.068 ac-ft/year, Post Developed: 0.181 ac-ft/year 184"' Street Short Plat Drainage Report -**-*******Water Quality Facility Data ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 Link: Rain Garden ......... Infiltration/Filtration Statistics -------------------- Inflow Volume (ac -ft): 27.60 Inflow Volume Including PPT-Evap (ac -ft): 28.67 Total Runoff Infiltrated (ac -ft): 28.67, 100.00% Total Runoff Filtered (ac -ft): 0.00, 0.00% Primary outflow To Downstream System (ac -ft). 0.00 Secondary Outflow To Downstream System (ac -ft): 0.00 Percent Treated (Infiltrated,+Rltered)[Total Volume: 100-00% .*.******.*Compliance Point Results Scenario Predeveloped Compliance Subbasin: Basin B Scenario Posideveloped Compliance Link: Rain Garden *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) ....... Discharge (cfs) ------------------------ --------- --- I ----------------- 2 -Year 1,147E-03 2 -Year 2.328E-10 :5 -Year 1.955E-03 5 -Year 2.328E-10 10 -Year 2.681E-03 10 -Year Z328E-10 25 -Year 1586E-03 25 -Year 2.328E-10 50 -Year 4.807E-03 50 -Year 2144IF-07 1 O0 -Ye a r 5,259E.03 100 -Year 1.329E-.06 200 -Year 7.906E-03 200 -Year 1,753E.06 Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than 0%): 0,0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS MEETS ALL LID DURATION DESIGN CRITERIA: PASS 184`h Street Short Plat Drainage Report Flow Duration Plot Pond B Dimensions Required Bottom Area = 120 sqft Design Bottom Area = 122 sgft 184'h Street Short Plat Drainage Report IIID! Rl 1NNI'I IIIgIII�Nlllll�lll ��u!�Illpfl1llll„NII111110II1VI _ Pond B Dimensions Required Bottom Area = 120 sqft Design Bottom Area = 122 sgft 184'h Street Short Plat Drainage Report Basin C Flood Control Calculations o r• • 184`h Street Short Plat Drainage Report MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.40 Program License Number: 201110001 Project. Simulation Performed on: 05117/2017 10:53 AM Report Generation Date: 051171201710:54 ANI Input File Name: 2017-05-16 Rain Garden Lot 3.fid Project Name: Edmonds Plat Analysis Title: Rain Gardens Lot 3 Comments: hydraulic connectivity of 6in/hr PRECIPITATION INPUT Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 0 Full Period of Record Available used for Routing Precipitation Station: 96003605 Puget East 36 in_5min 10/01/1939-10/01/2097 Evaporation Station 961036 Puget East 36 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default «*««***««« Default HSPF Parameters Used (Not Modified by User) *««*«**«««««*«* ********************** WATERSHED DEFINITION ****************«***««* Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.070 0.070 Area; of Links that Include Precip/Evap (acres) 0.000 0.006 Total (acres) 0.070 0.076 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin C ---------- ------- Area (Acres) -------- Till Forest 0.070 ............. ------------ Subbasin Total 0.070 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Basin C ---------- ------- Area (Acres) -------- Impervious 0.070 _ Subbasin Total 0.070 LINK DATA A.*,**,,, 0 ***..•.*.****«"** ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 LINK DATA ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 184'h Street Short Plat Drainage Report Link Name: Rain Garden Link Type: Bioretention Facility Downstream Link: None Base Elevation (ft) 100.00 Riser Crest Elevation (ft) 100.50 Storage Depth (ft) 0.50 Bottom Length (ft) 80.0 Bottom Width (ft) 3.0 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq -ft) 240. Area at Riser Crest EI (sq -ft) 498. (acres) 0.011 Volume at Riser Crest (cu -ft) : 328. (ac -ft) 0.008 Infiltration on Bottom and Sideslopes Selected Soil Properties Biosoil Thickness (ft) 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) 6.00 Biosoil Porosity (Percent) 40.00 Maximum Elevation of Bioretention Soil : 101,50 Native Soil Hydraulic Conductivity (in/hr) 0.54 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) 6.00 Common Length (ft) :0.000 Riser Crest Elevation : 100.50 ft Hydraulic Structure Geometry Number of Devices: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ****.... 4"Groundwater Recharge Summary Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac -ft) __., .,____. WW_-_.______. ..m_—. Subbasin: Basin C 10.698 Total: 10.698 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac -ft) Subbasin: Basin C 0.000 Link: Rain Garden 29.785 Total: 29.785 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.068 ac-ft/year, Post Developed: 0.189 ac-ft/year 180 Street Short Plat Drainage Report ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 *********« Link: Rain Garden *"«"'"""""* Infiltration/Filtration Statistics -------------------- Inflow Volume (ac -ft): 27.60 Inflow Volume Including PPT-Evap (ac -ft): 29.78 Total Runoff Infiltrated (ac -ft): 29,78, 100.00% Total Runoff Filtered (ac -ft): 0.00, 0.00% Primary Outflow To Downstream System (ac -ft): 0.00 Secondary Outflow To Downstream System (ac -ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Basin C Scenario Postdeveloped Compliance Link: Rain Garden *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) , Discharge (cfs) -------- ........... _..___---.._---- _.m..,.. ______-_------------------------- ___1 ----_-_.___---------- --l— 2-Year 1.147E-03 2 -Year 2 -Year 2.328E-10 5 -Year 1.955E-03 5 -Year 2.328E-10 10 -Year 2.681E-03 10 -Year 2.328E-10 25 -Year 3.586E-03 25 -Year 2.328E-10 50 -Year 4,807E-03 50 -Year 2.328E-10 100 -Year 5.259E-03 100 -Year 2.328E-10 200 -Year 7.906E-03 200 -Year 2.328E-10 «« Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 50%Q2 to Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS **** LID Duration Performance **** Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 0.0% PASS Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 0.0% PASS MEETS ALL LID DURATION DESIGN CRITERIA: PASS 184'h Street Short Plat Drainage Report Flow Duration Plot 001.3 a),Ir �a P�rt 11 Excursion Excursion at frvn: : 0.0% PASS Excursion 54'l.Q2 to Q2: 0.44t PAS oon E s r , r to CK , °. PASS Pos Excursion L�2 to Q_�D: O.�J'�. I��lI � ii �011� 1111 �'�lIIIII � �!lI�I Pond C Dimensions Required Bottom Area = 240 sqft Design Bottom Area = 240 sqft 184'h Street Short Plat Drainage Report Permeable Parrarnant Flood Control Calculations WWHM2012 PROJECT REPORT Project Name: 2017-05-17 Pervious Pavement .Access Road Site Name: 3 -Lot Edmonds Site Address: 184th Street City : Edmonds Report Date: 5/17/2017 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 0.80 Version Date: 2015/11/13 Version : 4.2.11 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, Flat •1 Pervious Total 0.1 Im ervious fund Use acre Impervious Total 0 Basin Total 0.1 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name : Permeable Pavement 1 Pavement Area: 0.1019 ft. Pavement Length: 222.00 ft. Pavement Width: 20.00 ft. Pavement slope 1: 0.02 To 1 Pavement thickness: 0.5 Pour Space of Pavement: 0.2 Material thickness of second layer: 0.17 Pour Space of material for second layer: 0.2 Material thickness of third layer: 1 184th Street Short Plat Drainage Report Pour Space of material for third layer: 0.32 Infiltration On Infiltration rate: 1.23 Infiltration safety factor: 0.5 Total Volume Infiltrated (ac -ft.): 10.956 Total Volume Through Riser (ac -ft.): 0 Total Volume Through Facility (ac -ft.): 10.956 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap, From Facility: 1.05 Element Flows To: Outlet 1 Outlet 2 184!h Street Short Plat Drainage Report Permeable Pavement Hydraulic Table ac -,ft. Discharcetcfs) 0.0000 0.101 0.000 0.000 0.000 0.0186 0.101 0.000 0.000 0.063 0.0371 0.101 0.001 0.000 0.063 0.0557 0.101 0.001 0.000 0.063 0.0742 0.101 0.002 0.000 0.063 0.0928 0.101 0.003 0.000 0.063 0.1113 0.101 0.003 0.000 0.063 0.1299 0.101 0.004 0.000 0.063 0.1484 0.101 0.004 0.000 0.063 0.1670 0.101 0.005 0.000 0.063 0.1856 0.101 0.006 0.000 0.063 0.2041 0.101 0.006 0.000 0.063 0.2227 0.101 0.007 0.000 0.063 0.2412 0.101 0.007 0.000 0.063 0.2598 0.101 0.008 0.000 0.063 0.2783 0.101 0.009 0.000 0.063 0.2969 0.101 0.009 0.000 0.063 0.3154 0.101 0.010 0.000 0.063 0.3340 0.101 0.010 0.000 0.063 0.3526 0.101 0.011 0.000 0.063 0.3711 0.101 0.012 0.000 0.063 0.3897 0.101 0.012 0.000 0.063 0.4082 0.101 0.013 0.000 0.063 0.4268 0.101 0.013 0.000 0.063 0.4453 0.101 0.014 0.000 0.063 0.4639 0.101 0.015 0.000 0.063 0.4824 0.101 0.015 0.000 0.063 0.5010 0.101 0.016 0.000 0.063 0.5196 0.101 0.016 0.000 0.063 0.5381 0.101 0.017 0.000 0.063 0.5567 0.101 0.018 0.000 0.063 0.5752 0.101 0.018 0.000 0.063 0.5938 0.101 0.019 0.000 0.063 0.6123 0.101 0.020 0.000 0.063 0.6309 0.101 0.020 0.000 0.063 0.6494 0.101 0.021 0.000 0.063 0.6680 0.101 0.021 0.000 0.063 0.6866 0.101 0.022 0.000 0.063 0.7051 0.101 0.023 0.000 0.063 0.7237 0.101 0.023 0.000 0.063 0.7422 0.101 0.024 0.000 0.063 0.7608 0.101 0.024 0.000 0.063 0.7793 0.101 0.025 0.000 0.063 0.7979 0.101 0.026 0.000 0.063 0.8164 0.101 0.026 0.000 0.063 0.8350 0.101 0.027 0.000 0.063 184!h Street Short Plat Drainage Report 0.8536 0.101 0.027 0.000 0.063 0.e72I 0.101 0.028 0.000 0.063 0.8e07 0.101 0.029 0.000 0.063 0.9092 0.101 0.029 0.000 0.063 0.9278 0.01 0.038 0.000 0.063 8.e463 0.01 0.030 0.000 0.863 0.964e 0.01 0.031 0.00U 0.063 0.9834 0.01 0.032 0.000 0.063 1.0020 0.101 0.032 0.000 0.863 1.0206 0.101 0.032 0.000 0.063 1.0391 0.101 0.033 0.000 0.063 1.0577 0.101 0.033 0.008 0.063 1.0762 0.101 0.034 0.000 0.063 1.0948 8.101 0.034 0.800 8.063 1.1133 0.101 0.034 0.800 0.063 1.1319 0.101 0.035 0.000 0.863 1.1504 0.101 0.035 0.008 0.063 1.16e0 0.101 0.035 0.000 0.063 1.1876 0.102 0.036 0.000 0.063 1.2061 0.102 0.036 0.000 0.063 1.2247 0.102 0.037 0.000 0.063 1.2432 8.102 0.037 0.000 0.062 1.2618 0.102 0.037 0.000 0.063 1.2e03 0.102 0.038 0.000 0.063 1,2e89 0.102 0.038 0.000 0.063 1.3174 0.102 0.038 8.000 0.063 1.3360 0.102 8.039 0.000 0.063 1.35:6 0.102 0.039 0.000 0.063 1.3731 0.102 0.040 0.000 0.063 1.3e17 0.102 0.040 0.008 0.063 1.4102 0.102 0.040 0.000 0.063 1.42e8 0.102 0.041 0.000 0.063 1.4473 0.102 0.041 0.000 0.063 1.4659 0.102 0.041 0.000 0.063 1.4e44 0.102 0.042 0.000 0.063 1.5030 0.102 0.042 0.000 0.063 1.5216 0.102 0.043 0.000 0.063 1.5401 0.102 0.043 0.000 0.063 1.5587 0.102 0.043 0.000 0.063 1.5772 0,102 0.0*4 0.000 0.063 1.5958 0.102 0.044 0.000 0.063 1.6143 0.102 0.044 0.000 0.063 1.632e 0.102 0.045 0.000 0.063 1.6514 0.102 0.045 0.000 0.063 Name a^aiu z Bypass: No ornnudm^tez. No Pervious Land Use acre Pervious Total o ImEervious Land Use acre ROADS FLAT 0.1 Impervious Total 0.1 Basin Total 0.1 1o4t^Street Short Plat Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.1 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:O Total Impervious Area:0.101928 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 inn year 0 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0 5 year 0 10 year 0 25 year 0 50 year 0 100 year 0 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated,. POC #1 Year Predeveloped, Mit ated Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 184'h Street Short Plat Drainage Report 0.0000 0 Q eaao 0.0000 O 0 raoa 0.0000 0 0 0 eaoa 0.0000 u 0 raoo 0.0000 V O 0 eaaa 0.0000 O 0 0 eaoa 0.0800 8 0 u raoo 0.0000 0, O n eaoa 0.0000 0 0 0 eaoa 0.0800 U 8 0 raaa 0.0000 A O 0 eaaa 0.0000 U 0 0 eaoa 0.0000 0 O 0 raaa 8.0000 Q W V Pass 0.0008 C) 0 eaao 0.0000 0 eaaa 0.0000 0 U 0 eaao 0.0000 Q Q O eaua 0.0000 8 0 V Pass 0.0000 0 0 Q eaaa 0.0000 Q O O Pass 8.0000 O eaao 0.0000 0 V O eaaa 0.0000 Q u 8 eaao 0.0000 0 0 0 eaou 0.0000 0 0 O Pass 0.0000 0 0 0 eaao 0.0008 0 O 0 eaaa 0.0000 u 0 Pass 0,0000 Q 0 0 raaa 0.0000 A 0 0 raoo 0.0000 O O O eaaa 0.0008 0 n O Pass 8.0000 0 0 0 eaaa 0.0000 O $ 0 eaoa 0.0000 0 eaua 0.0000 0 0 eaau 0.0000 U 0 0 eaoo 0.0000 0 a 0 eaoa 0.0000 0 0 W raoa 0.0000 0 g 0 Pass 0.0000 0 V raaa 0.0000 Q O 0 Fla oa 0.0000 8 O 0 Pass 0.0000 0 d Q Pass 0.0000 0 Q N eaaa 0.0000 0 0 P Pass 0.0000 0 Q 0 eaaa 0.0000 0 O O Pass 0.0000 0 0 Q eaau 0.0000 0 O 0 eaoa 0.0000 O & U Pass 0.0000 0 u O raao 0.0000 0 0 u Pass 0.0000 n 0 Pass 0.0000 0 8 Q raaa 8.0000 0 * Q Pass 0.0000 O 01 0 eaaa 0.0000 Q 0 Q Pass 0.8000 0 V M Pass 0.0000 Q 0 0 eaoa 0.0000 O 0 0 Pass 0.0000 0 8 raao 18�h Street Short Plat 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass 0.0000 0 0 0 Pass Flow and Volume for POC #1 on-line facility volume: 0 acre-feet on-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. LID Report LID Techniqtie Jo,"'i for fotal, V'rNmirl Vol"'Jour lrifilAnhl-�1)11 r'orRut_01Vn Porcont W,0 or Q11ali.ty Percent 11hro(Iqll Vol 119M Vn I (olml Vo Djton Treatm,mi? Non,js w,jtf3r Quaiit:.y t f j, f t i on ra tncJ Treal-ed I N 99,81 �4 0.00 99.81 0,00 Total vojrlmo 99 0.00 01t NO ylrnal , C:Y',zdlt wi,Uh MD "l-amdard H Uunit,ioil ivmlysfs flvTsull_ flaofgnci Per1nd and imp1nd Change ' a No changes have been made. Thiruoqram ,md i�� provirtmJ witDoW_ w,rr,jy�ty of y Jot 'rho ��riliro �,�tld tbls ir, �)y Ore io,r, c�l.,�,a (�tnok '�otulic)W,�, INC, da.gi�sul '�irlls a � 'I wFiry ont o it r' ex!PreS',M�d 0�, IMP) a efl, i I ud i ri,q I' r (I PI I ot i J al i tm7 i n -1 mp I I ("d W,arraill f(m, of pra,fqrj,lm and ,W1,,HRP,o,1Yinq jf� 1�u r,vnt (�Ynok, SolWfore ��, Inc. ly,� fiahf,or alry draiaqc,r; WhFA1,r1U('V'aY WiH'Lrwt limit,w ii'm to rjamlqv�s fyla buoinno"3 inmof bLmlmos., illforr[lalAor, ba."Orviss ,"vj the az,[�Artq GUtq; 'a'r()y ]ri ,1jj I j q, t, ,, 9T,,gyaro( r!voi) if Cinar Creek sulul Inc, ha, odvined r,,f the 10"Y (,f o�J,�h 1841h Street Short Plat Drainage Report Bypass Arse Flood Control Calculations PROJECT REPORT Project Name: Bypass Area (100 year calc) Site Name: Site Address: City Report Date: 2/16/2017 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 0.80 Version Date: 2015/11/13 Version : 4.2.11 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, Flat .08 Pervious Total 0.08 Impervious Land Use acre Impervious Total 0 Basin Total 0.08 Element Flows To: Surface Interflow MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Flat .03 Pervious Total 0.03 Impervious Land Use acre ROADS FLAT 0.05 Impervious Total 0.05 Basin Total 0.08 780' Street Short Plat Drainage Report Groundwater Element Flows To: Surface Interflow Groundwater ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.08 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.03 Total Impervious Area:0.05 Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.000968 5 year 0.001502 10 year 0.001833 25 year 0.002217 50 year 0.002478 100 year 0.002719 Flow Frequency Return Periods for Mitigated. POC #1 Return 'Period F1ow1cfs) 2 year 0,02 9355 5 year 0.040327 10 year 0.048445 25 year 0.059717 50 year 0.068878 100 year 0.07872 This program and accr,ntpanying documentation are provided With,DUt warrr s n1:y Of "'my H n"J. Gds ?sisr s r 3 s a. flk regarding the performance and results of this program irs w utgruaw9 bG End V e ( 1 quaw ar r k, 5ric and the governmental lic nfoee or sublicensees disclaim all wor:'apA oter, P'D ba v rxprt c:¢d "Ir fvarul iei'J in" s.ua-inlj lmt not limited to implied warranties of program and accompany�nq far no e;"av r B alro,.aa I c li iasr k t.u.."uk Solutions Inc. be li.aWe for any damages whatsoever w5'Ltia+.aul Ilii l a"sv of business profits, loss of business information, business �"Jnd tho Like) Auy tdrrg a,Rab rrG B:;w it a sn',f, or inability to use this program even if Clear Creek Soa itN r+t17Y; 4 ss ur` e h R x Garr IEua t r w""� s Is..a°' d u�tist 'r."xu Bs�r+r¢u been advised of the possibility of such damages. Softw,,rvp rq�,yrighJ:. 0 by : +"=Ae,r, i.er;r='a •s'aGv,L:r srs"a, ,fr'a Ffdrw=r 2016; All Rights Reserved. 184"' Street Short Plat Drainage Report SECTION 8 MINIMUM REQUIREMENT #8 WETLANDS PROTECTION 184"' Street Short Plat Drainage Report Wetlands Irotectlon There are no existing wetlands on-site or immediately downstream; therefore wetland hydroperiod calculations are not required for this project. 1841h Street Short Plat Drainage Report SECTION 9 MINIMUM REQUIREMENT #9 OPEARTIONS AND MAINTENANCE MANUAL 1841h Street Short Plat Drainage Report •ar- � � Stormwater facilities and BMPs shall be inspected, operated and maintained in accordance with the City of Edmonds Stormwater Code Supplement, as well as the LID manual. Additional maintenance recommendations can be found in Volume V, Chapter 4 of the 2005 Department of Ecology Stormwater Management Manual for Western Washington, including the recommendations contained on the following pages: 184`h Street Short Plat Drainage Report No. 2 — Infiltration Facilities Maintenance Defect Conditions When Maintenance Is Needed Results Expected When Component Maintenance Is Performed General Trash & Debris Function of facility is impaired by or likely to Trash and debris is be impaired by trash and debris. removed. Vegetation Function of facility is impaired by vegetation Vegetation is removed or managed to restore proper function of facility. Use of herbicides shall be in accordance with an Integrated Pest Management Plan. Contaminants and Any evidence of oil, gasoline, contaminants or Contaminants or pollutants Pollution other pollutants are removed Note: Coordinate removal/cleanup with local and/or state water quality response agency. Erosion Eroded daona'!e over 2 inches deep where cause Slopes are stabilized using of damage is still present or where there is aappropriale erosion control potential for continued erosion. measure(s); e.g., rock reinforcement, planting of grass, compaction. Storage Area Sediment Water ponding in inliltr'ration pond atler rainfall Sediment is removed and/or ceases and appropriater'time allowed (br facility is cleaned so that infiltration. infiltration system works (A percolation test pit or test of'faacility according to design. indicates tiac.ility is only waorking 411 90% of its designed capabilities. if two inches or more sediment is present„ remove). Filter Bags (if Sediment and Debris Sediment and debris fill bag more than 1/2 full. Filter bag is replaced or applicable) system is redesigned. Rock Filters Sediment and Debris By visual inspection, little or no %N atter flows Gravel in rock filter is through falter during heavy rain storms. replaced. Side Slopes of Pond Erosion See "Detention Ponds" (No. l). See "Detention Ponds" (No. 1). Berms Settling Any part of a bet -in which has settled at least 4 Berm is repaired and inches lower than the design eleval ion. restored to the design If settlement is apparent, measure berm to elevation. determine amount of settlement. *fettling can be an indication of"'nion severe p�roblems with the berm or oulle:t xorks, Note: A hcensed civil engincct` araay lie needed to determine the cause of the settlement. Erosion Any erosion observed on a compacted structural Slopes should be stabilized berm embankment. using appropriate erosion Note: A licensed civil engineer may be needed control measure(s); e.g., rock reinforcement, planting to inspect, evaluate and recommend a repair of grass, compaction. plan. 1841' Street Short Plat Drainage Report No. 3 — Underground Detention Pipes/Tanks Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Storage Area Plugged Air Vents One-half of the cross section of a vent is blocked Vents open and at any point or the vent is damaged. functioning. Debris and Sediment The average sediment depth me sured tit All sediment, debris, multiple locations exceeds 10%ofthc detention and organic matter pipe diameter Cor the depth ofthe storage area) removed from storage or the sediment depth nicasured at any single area. point exceeds 15% of the pipe diameter. (I'xample: "'l'1re sediment depth in a 60 -each diameter detention pipe is measured at three locations„ `l`kic sediment would need tobe removed if the aaveraagc depth of the three measurements is al least h inches or ifthe depth of any single measurement is at least 9 inches. Joints Between Section Any openings or voids at section joint allowing mater i;a1 to seep into or water to leak rtut of All joints between tank/pipe sections are Tank/Pipe facility. sealed. Note: This may need an engineering analysis to assess the structural stability. Tank or Pipe Bent Out Any part oftank/pilte is bent out of shape more Tank/pipe section is of Shape than 10%of i,ts design shaft. repaired or replaced to Note: This may need an engineering analysis to design. assess the structural stability. Tank/Pipe Material Any visible holes or cracks wider than a quarter Tank/pipe is repaired or o'fan inch or evidence of material seeping into or replaced to design Nvat:er leaking, out of pipe wall, or qualified specifications and is maintenance or inspecl:'ion personnel determine I structurally sound. that tank/pipe is not structurally sound. Access Hole Cover Not in Place Cover is missing or only partially in place. Any Manhole is closed. open manhole requires maintenance. Locking Mechanism Locking mechanism cannot be opened or lock Mechanism or lock Not Working bolts cannot be removed by one maintenance bolts open with proper person with proper hand tools. hand tools. Cover Difficult to One maintenance person cannot remove lid after Cover can be removed Remove applying normal lifting pressure with proper and reinstalled by one hand tools. Intern is to keep cover from scaling maintenance person off access to maintenance. with proper hand tools. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design cracked/broken rungs, misalignment, rungs not standards and allows securely attached to structure wall, rust, or maintenance person cracks. safe access. Catch Basins See match Basinsll See match Basinsll (No. 5). See match Basinsll (No. 5) (No. 5). Standpipe, I Obstructions, Damaged, See control Structure/Flow Restrictorsll (No. 4) See -Control Cleanout Gate, or Missing Structure/Flow Restrictorsll (No. 4) Orifice Plate 184"' Street Short Plat Drainage Report No. 4 — Control Structure/Flow Restrictors Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Standpipe Obstructions Any material blocking (or having the potential of blocking) the pipe overflow. Pipe is free of all obstructions and works as designed. Structural Damage Structure is not securely attached to manhole wall. Structure is securely attached to wall and outlet pipe. Structure is not in upright position (allow up to Structure is in correct 10% from plumb). position. Connections to outlet pipe are not watertight and show signs of rust. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes other than designed holes in the structure. Structure has no 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 maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and 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 missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Access Hole Cover Not in Place Cover is missing or only partially in place. Any Manhole is closed. open manhole requires maintenance. Locking Mechanism Not Working Locking mechanism cannot be opened or lock bolts cannot be removed by one maintenance person with proper hand tools. Mechanism or lock bolts open with proper hand tools. Cover Difficult to Remove One maintenance person cannot remove lid after applying normal lifting pressure with pamper hand tools. Intent is to keep cover from scaling off access to maintenance. Cover can be removed and reinstalled by one maintenance person with proper hand tools. Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, cracked/broken rungs, misalignment, rungs not Ladder meets design standards and allows securely attached to structure wall, rust, or cracks. maintenance person safe access. 784"' Street Short Plat Drainage Report No. 4 — Control Structure/Flow Restrictors Maintenance Defect Condition When Maintenance is Needed Results Expected When Maintenance is Component Performed Catch Basin See -Catch Basinsll See match Basinsll (No. 5). See match Basinsll (No. 5). (No. 5). Sediment & Debris Sediraaent, trash, vegetation, and/or otlacr debris Control structure orifice material exceeds 25% ol'the catch basin sump is not blocked. All depth or is 1 foot below the orifice plate. sediment and debris removed. 1841h Street Short Plat Drainage Report No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed General Sediment & Debris Sediment, trash, and/or otherdcba is material is located immediately in firont of the catch basin No sediment or debris is located immediately in front opening or is ])looking inletting vivacity ol` the of catch basin or on grate basin by more than 10%p. opening. Scdinneaat, l�rash„ other debris mawrial No sediment or debris is in (located in the catch basita) exceeds 60 percent of the catch basin. the rsnnp depth as measured lrotaa the bottoan of basin to invert anfthe lowvestOpe into or oast ofthe basin,, but in no case less than a minimann of six inches clearance from the debris srarfiace to tlae invert of the lowest pipe. Sediment, trash, and/or other debris material Inlet and outlet pipes are free located in any inlet or ontict pipe is bhwking more of sediment and debris. than 1/3 of its height. Dead animals or vegetation that impair catch basin No dead animals or funelion or that could generate odors that could vegetation are present within cause complaints or dangerous gases (e.g., the catch basin. methane). Structure Top slab has holes larger than 2 square inches or Top slab is free of holes and Damage to cracks wider than 1/4 inch cracks. Frame and/or (Intent is to make sure no material is seeping into No water and/or soil is Top Slab the catch basin). seeping into the catch basin Frame not sitting flush on top slab, i.e., s,eptaraation Frame is sitting flush on the of more than 3/4 inch of the frame from the tamp riser rings or top slab and slab. Frame not securely attached I firmly attached. Fractures or Cracks wider than 1/2 inch or evidence of soil Catch basin is replaced or Cracks in Basin particles entering, the structure through the cracks, repaired to design standards. Walls/ Bottom or qualified tnaintesiance or inspection persolaaael. determine that tlae vault is not structurally somid, Grout Millet has ;wparated or cracked ^aider lban Pipe is regrouted and secure 1/2 iaac,h and longer than 1 Pitot at the loan of -any at basin wall. inlet/outlet pipe or any evidence ofsoil particles entering catch basin through cracks, Settlement/ Misalignment Settlement of misalignment of the catch basin causes a safety, function, or design problem. Catch basin is replaced or repaired to design standards. Contaminants Any evidence of oil, gasoline, contaminants or Contaminants or pollutants and Pollution other pollutants are removed. Note: Coordinate removal/cleanup with local and/or state water quality response agency. Access Hole Cover Cover Not in Cover is missing or only partially in place. Any Catch basin cover is fully in Place open catch basin requires maintenance. place Locking Locking mechanism cannot be opened or lock Mechanism or lock bolts Mechanism Not bolts cannot be .removed by one maintenance open with proper hand tools. Working person with proper hand tools. Cover Difficult (:)aae anaintenance person cannot re novc lid after Cover can be removed and to Remove applying normal 1i11ing pressure with proper hand reinstalled by one tools, Intent is keep cower Roan scaling offaaccess maintenance person with to maintenance. proper hand tools. 184"' Street Short Plat Drainage Report No. 5 — Catch Basins Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Trash and Trash or debris that is plugging more than Maintenance is performed Ladder Ladder Rungs Ladder is unsafe due to missing rungs, Ladder meets design Metal Unsafe cracked/broken rungs, rungs not securely attached standards and allows to basin wall, misalignment, rust, cracks, or sharp maintenance person safe Bars are loose and rust is causing 50% Barrier replaced or repaired to design edges. access. Metal Grates Trash and Trash and debris that is blocking more than 20% Grate free of trash and (If Applicable) Debris of grate surface inletting capacity. debris. Damaged or Grate missing or broken member(s) of the grate. Grate is in place and meets Missing. design standards. No. 6 — Debris Barriers (e.g., Trash Racks) Maintenance Components Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed General Trash and Trash or debris that is plugging more than Barrier cleared to design flow Debris 20% of the openings in the barrier. capacity. Metal Damaged/ Missing Bars. Bars are bent out of shape more than 3 inches. Bars in place with no bends more than 3/4 inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50% Barrier replaced or repaired to design deterioration to any part of barrier. standards. Inlet/Outlet Debris barrier missing or not attached to pipe Barrier firmly attached to pipe Pipe 180' Street Short Plat Drainage Report No. 7 — Energy Dissipaters Maintenance Defect Conditions When Maintenance is Needed Results Expected When Components Maintenance is Performed Rock Pad Missing or Only one layer of rock exists above native Rock pad replaced to design Moved Rock soil in area five square feet or larger, or any standards. exposure of native soil where pad was originally installed. Erosion Soil erosion in or adjacent to rock pad. Rock pad replaced to design standards. Rock Gabion Wire basket Deterioration determined to be near to Rewire area of concern or replace Structures matrix breaking. Broken wire results in hole large basket and/or rocks as necessary deteriorated enough to allow rocks to protrude out of or broken basket Wire basket Baskets have shifted and no longer providing Realign or relocate as necessary to misaligned full energy dissipations or may be prone to meet design intent tipping or collapse Dispersion Trench Perforated Accumulated sediment that exceeds 20% of Pipe cleaned/flushed so that it Pipe Plugged the design depth or over 1/3 of perforations matches design. with in pipe are plugged. Sediment Not Water is discharging at a few concentrated Trench redesigned or rebuilt to Discharging points along, the top of (lie trench rather than standards. Water Ilowing uniformly along; the eniire length of Properly trench lip. -4)istributorll Water is observed or reported to be flowing Facility rebuilt or redesigned to Catch Basin out of top of basin during any storm less than standards. Overflows the design storm. Receiving Water in receiving area is causing or has No danger of landslides. Area Over- potential of causing landslide problems. Saturated Catch Basins Other Defects See -Catch Basinsll (No. 5). See -Catch Basinsll (No. 5). 184th Street Short Plat Drainage Report No. 15 — Stormfilteem Maintenance Component Below Ground Vault Below Ground Cartridge Type Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed Sediment Sediment depth exceeds 1/4 inch. No sediment deposits which would Accumulation on impede permeability of the Media. compost media. Sediment Sediment depth exceeds 6 inches in first No sediment deposits in vault Accumulation in chamber. bottom of first chamber. Vault Trash/Debris Trash and debris accumulated on compost Trash and debris removed from the Accumulation filter bed. compost filter bed. Sediment/Debris in Sediment, trash, and/or other debris material Sediment and debris removed. Drain located in any inlet, outlet, or cleanout pipe is Pipes/Cleanouts blocking more than 1/3 of its height. Damaged Pipes Any pert ofthc pipes that are crushed or Pipe repaired and/or replaced. damaged dtae to corrosion and/or settlement. Access Hole Cover One maintenance person cannot remove lid Cover can be removed and Damaged/Not after applying normal lifting pressure with reinstalled by one maintenance Working proper hand tools. person with proper hand tools. Vault Structure Cracks wider than 1/2 inch or evidence of Vault replaced or repairs made so Includes Cracks in soil particles entering the structure through that vault meets design Wall, Bottom, the cracks, or qualified maintenance or specifications and is structurally Damage to Frame inspection personncl determine that the vault sound. and/or Top Slab is not structurally sound. Cracks wider than 1/2 inch at the joint of any Vault repaired so than no cracks inlet/outlet pipe or evidence of soil particles exist wirier than 1/4 inch at the entering through the cracks. joint of the inlet/outlet pipe. Baffles Baffles corroding, cracking warping, and/or Baffles repaired or replaced to showing, signs of failure as determined by specifications. rlualaCaed maintenance or inspection personnel. Access Ladder Ladder is corroded or deteriorated, not Ladder replaced or repaired and Damaged functioning properly, not securely attached to meets specifications, and is safe to structure wall, missing rungs, has use as determined by inspection cracked/broken rungs, and/or is misaligned. personnel. Media clogged Drawdown of water through the media takes Media cartridges replaced. longer than 1 hour, and/or overflow occurs frequently. Flow short Flows do not properly enter filter cartridges. Filter cartridges replaced. Circuited Check manufacturer's operation and maintenance manual for complete maintenance instructions. 184th Street Short Plat Drainage Report No. 16 — API Baffle Oil/Water Separators Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed General Discharged Water Not Clean Water discharged from facility has obvious signs of poor water quality, Treated stormwater discharged from vault should be clear without thick visible sheen. Sediment Accumulation Sediment depth in bottom of vault exceeds 6 inches in depth. No sediment deposits on vault bottom that would impede flow through the vault and reduce separation efficiency. Trash and Debris Accumulation Trash and debris accumulation in vault, or pipe inlet/outlet, floatables Trash and debris removed from vault, and inlet/outlet piping. and non-floatables. Oil Accumulation Oil accumulations that exceed I inch, at the surface of the water. Extract oil from vault by vactoring. Disposal in accordance with state and local regulations. Damaged Pipes Inlet or outlet pipes damaged or Pipes repaired or replaced. broken and in need of repair. Access Hole Cover Damaged/Not Working One maintenance person cannot remove lid after applying normal lifting pressure with proper hand Cover can be removed and reinstalled by one maintenance person with proper hand tools. tools. Vault Structure Damage - Includes Cracks in Walls Cracks wider than 1/2 inch or evidence of soil particles entering the structure through the cracks, or Vault replaced or repairs made so that vault meets design specifications and is structurally sound. Bottom, Damage to Frame and/or Top Slab qualified maintenance or inspection personnel deteranine that the vault is not structurally sound. Cracks wider than 1/2 inch at the joint of any inlet/outlet pipe or evidence of soil particles entering Vault repaired so that no cracks exist wider than 1/4 inch at the Joint of the inlet/outlet pipe. through the cracks. Baffles Baffles corroding, cracking, warping and/or showing signs of failure as Baffles repaired or replaced to specifications. determined by qualified maintenance or inspection personnel. Access Ladder Damaged Ladder is corroded or deteriorated, not functioning properly, not securely attached to structure wall, missing Ladder replaced or repaired and meets sp>ecil`acalions, and, is safe to use as determined by inspection personnel. rungs, has cracked/broken rungs, and/or is misaligned. 180' Street Short Plat Drainage Report No. 18 — Catchbasin Inserts Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed General Sediment When sediment forms a cap over the insert No sediment cap on the insert Accumulation media of the insert and/or unit. media and its unit. Trash and Debris Trash and debris accumulates on insert unit Trash and debris removed from Accumulation creating a blockage/restriction. insert unit. Runoff freely flows into catch basin. Media Insert Not Effluent water from media insert has a visible Effluent water from media insert Removing Oil sheen. is free of oils and has no visible sheen. Media Insert Catch basin insert is saturated with water and Remove and replace media insert Water Saturated no longer has the capacity to absorb. Media Insert -Oil Media oil saturated due to petroleum spill Remove and replace media insert. Saturated that drains into catch basin. Media Insert Use Media has been used beyond the typical Remove and replace media at Beyond Normal average life of media insert product. regular intervals, depending on Product Life insert product. 184`h Street Short Plat Drainage Report no. LL - iracm visciiair a roinis Condition When Maintenance is Drainage System Potential Conditions When Maintenance Is Results Expected When Maintenance Feature Defect Needed Is Performed Or Not Needed Monitoring Inspection of Sheen, obvious oil or other Identify and eliminate pollution source Gate and locking mechanism are fully Discharge Water contaminants present. AND report discharge to Snohomish functional for access purposes. for Obvious Damaged or County Surface Water Management working Signs of Poor missing Division. Hinges intact and lobed. Gate is Water Quality. components maintenance person. freely. Damaged or Effluent discharge from facility should be missing clear. Gate is aligned and vertical (plumb). Receiving Area Water in receiving area is causing Receiving area sound, Saturated substrate to become saturated and unstable. Missing stretcher bands, and ties. General Rock Pad - Only one layer of rock exists above Rock pad replaced to design standards. Missing or native soil in area five square feet or Moved Rock larger, or any exposure of native soil where pad was originally installed. Rock Pad - Soil erosion in or adjacent to rock pad. Rock pad replaced to design standards. Erosion Obstructions, Roots or debris enters pipe or deforms Use mechanical methods to remove root Including Roots pipe, reducing flow if possible. Use of chemicals to remove roots shall be done in accordance with Integrated Pest Management plan. If necessary, remove the vegetation over the line Pipe Rusted or Any part of the pipe that is broken, Pipe repaired or replaced. Deteriorated crushed or deformed more than 20% or any other failure to the piping No. 23 — Access Gates Maintenance Defect Condition When Maintenance is Maintenance Action and Expected Component Needed Results General Damaged or Gate and/or locking mechanism missing condition is such that access is Gate and locking mechanism are fully components impeded. functional for access purposes. Damaged or Broken or missing hinges such that gate working missing cannot be easily opened and closed by a Hinges intact and lobed. Gate is components maintenance person. freely. Damaged or Gate is out of plumb more than 6 inches missing and more than 1 foot out of design Gate is aligned and vertical (plumb). components alignment. Damaged or missing Missing stretcher bands, and ties. Stretcher bar, bands, and ties in place. components 180' Street Short Plat Drainage Report No. 24 — Access Roads Maintenance Defect Condition When Maintenance is Maintenance Action and Expected Component Needed Results General Road Surface Condition of road_ surface may lead Road repaired. to erosion of the facility or limit access. Erosion of Noticeable rills are seen in Causes of erosion are identified and Ground landscaped areas. steps taken to slow down/spread out Surface the water. Eroded areas are filled, contoured, and seeded. If needed, ret'acle affected areas. Vegetation I°eget do of road is impaired by Vegctation is removed or managed to vegetation resWc proper hinction of facility, Use of herbicides shall be in accordance with an Integrated Pest Management Plan. Tree Growth Tree growth does not allow Trees do not hntder maintenance maintenance access or interferes with activities. maintenance activity (i.e., slope mowing, silt removal, vactoring, or equipment movements). If trees are not interfering with access or Inain.tenanee, do not remove. Trees or shrubs that trees or shrubs removed from �havelen overroad. �Fallen 184'' Street Short Plat Drainage Report SECTION 10 MINIMUM REQUIREMENT #10 OFFSITE ANALYSIS AND MITIGATION 184'" Street Short Plat Drainage Report SECTION 11 MINIMUM REQUIREMENT#11 FINANCIAL LIABILITY 1841h Street Short Plat Drainage Report Wr The project site is not located within any critical areas nor does the project involve 7,000 square feet or more of land disturbing activity. Therefore a performance bond is not required for this project. 18,eh Street Short Plat Drainage Report