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HomeMy WebLinkAbout03320 - Technical Information Report - Drainage i `\ � m m C� � � - . e � � Site Development Associates, LLC . � .: :•_ - ---�— - �o�s Project Location: 290B Ilwaco Averue NE Renton, WA Prepared For: � Offe Engineers 13932 SE 159'h Place Renton, WA 98058-7832 Prepared by: Site Development Associates, LLC Bill Helstey, P.E. 18322 Bothell Way NE Bothell. WA 98011 Date: October 11, 20Q6 Project Number: 107-412-05 -:.d N `.e'_-' Y r�" '� g_k ,� (� . _r � "`c L �4 -..n r '.S 1��. x, �� _'�.,�" . .. � �� ar�� � � �, � e M�� �S r �t�,�;�+ :> ` �t -t�`L'1°at �� '3 'i'�w ..er <� i - . s� Si�t# xp ,z.v }£t��+,�,h .,,I.KaG'3� ,t� ` '�' . �,� 'j2 �t +� A � . - 't � � �� .- . � x„+� . ��-� . , .pc. � ..4�x .ti"r .. � . . .r.�•-r' �a'� , ;� �' .���.,. � � t �3.. x � . .e _ '#: 'rt3 g' �.,_ .. i,'��� � .. _ �� ��� . 3'� . . . .�' ��� }' . . _ � ..� .. ��? �.. ` r � 'c� � ��.f..�. 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J ''�_� n�. y i.e:+'.�'n �Ct''. ` 3320 October 11,2006 LANGLEYRIDGE Final Stom Drainage Report Project Location: 2906 Iiwaco Avenue NE Renton, WA Prepared For: OfFe Engineers 13932 SE 159t''Place Renton, WA 98058-7832 Prepared by: Site Development Associates, LLC Bill Helsley, P.E. 18322 Bothell W ay N E 6othell, WA 98011 Date: October 11, 2006 Project Number: 107-012-05 A. � �'(�.. ...� S G •'' i �,����. %,f. . � . : �' 39 7 ' ° c� T � S�ONAL� �'a� �b- li- bL EXPIRES 6/9/2007 LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report October 11,2006 TABLE OF CONTENTS Project Description 1 Core Requirement No. 1 1 Core Requirement No. 2 1 Core Requirement No. 3 4 Core Requirement No. 4 4 Core Requirement No. 5 4 Core Requirement No. 6 4 Core Requirement No. 7 4 Core Requirement No. 8 4 Special Requirement No. 1 4 Special Requirement No. 2 4 Special Requirement No. 3 5 Special Requirement No. 4 5 Special Requirement No. 5 5 Appendix A—Figures Appendix B—Downstream Analysis Appendix C—Calculations Appendix D—Operations and Maintenance Manual LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report _ _ October 11,2006 Project Description The purpose of this report is to present a final storm drainage analysis for the Langleyridge Subdivision in accordance with City of Renton requirements. The proposed project will subdivide the site into 34 lots. One of the lots will remain as a lot used for a small business, and three of the fots will remain with the existing single family homes (one residence is currently being constructed). The remaining 30 lots will be newiy constructed single-family residences. In addition to the roadways, the proposed project wiii include storm water facilities necessary to accommodate the new lots. Water quality treatment wili be provided on- site in a lined water quality pre-settling pond. Overflow from the pond will drain into the adjacent infiltratian pond. This report addresses the storm drainage issues associated with the subdivision of the property, and construction of the new homes and access roads. The design standards addressed for this report are contained in King County Code and the 2005 King County Surface Water Design Manual. Review of the 8 Core Requirements and 5 Special Requirements of the 2005 King County Surface Water Design Manual SDA has reviewed the Core and Special Requirements in Chapter 1 of the King County Surface Water Design Manual, and addresses each of the requirements as follows: Core Requirement No. 1 — Discharge at Natural Location Currently, the storm water runoff on the project site flows narth and easi by means of overland flow. This flow follows the natural steep contours of the land mostly through forested undeveloped land on the project site. The flow discharges directty into May Creek, which is located on the northern part of the project site. On the northeast portion of the site, the flow currently makes its way around the existing single family residence and then into May Creek. Runoff from the two existing lots and the 27 proposed single family residences on the soufhern plateau of the project site will be collected via a tight-line system. The conveyance system will route the water east first and then flow to the north along the eastern portion of the project site. This runoff will discharge into the water quality pond and then flow into the adjacent infiltration pond. The infiltrated storm water will make its way north about 500 feet into May Creek. Runoff from the three lots on the eastern portion of the site will be conveyed via a tight-line system running to the west and directly outletting into the water quality pond. Runoff from the two lots located adjacent to May Creek will continue to directly deposit into the creek. Core Requirement No. 2 — Offsite Analysis Task 1: Define and Map Study Area This project consists of seven parcels and is located in the City of Renton in King County, between approximately SE 100"' Place and SE May Valley Road. The property information for the seven project parcels are as follows. Pro ert Address Tax Parcel Number Area acres 2906 Ilwaco Avenue NE 0323059073 8.54 2533 Ilwaco Avenue NE 0323059247 6.17 3018 Ilwaco Avenue NE 3424059076 0.65 No address listed 3424059Q63 123 No address listed 0323059071 8.48 No address listed 03230590Q2 6.33 No address listed 0323059111 1.62 Tctal Project Area = 33.02 acres LANGLEYRIDGE SUBDIVISION � Final Storm Drainage Report October 11,2006 Table 1: Project Prope�ty lnformation The total project area is 33.02 acres and will be subdivided into 34 lots, 30 of which wiil contain newly constructed single family residences. Of the remaining four lots, two wiil contain existing singie family homes, one will contain a home that is currently under construction, and one (ot will contain the existing business and associated building. All of the 29 lots on the south portion of the site wiN gain access from a newiy constructed public road that runs east-west through the subdivision. This road will be located just no�th of and paraliel to SE 100`h Place. On the east, 143`d Avenue SE will connect the new road to SE 100'h Place. To the west, the new road wiil connect to the intersection of SE 100`h Street and SE 100t�' Place. The three lots on the east po�tion of the project site will gain access by a newly constructed public/private road off of Lyons Avenue NE. The two existing lots on the northeastern portion of the project site will continue to gain access by 143rd A�enue SE off of SE May Valley Road. The project site is zoned R-1 and the properties to the west are alsa zoned R-1. The analysis of the basin boundary indicates that the project is in the May Creek Drainage Basin. See Figure 1 for a vicinity map of the project and Figure 2 in {both in Appendix A}for an existing site survey of the project. Figure 3 in Appendix A shows the proposed site plan for the development. Task 2: Review all Available Information on the Study Area Critical Drainaqe Area Map • May Creek Drainage Basin • Cedar River/Lake Washington Watershed • Cedar-Sammamish WRIA(8) Flaod plainlfloodwav(FEMA) Maps • There are no mapped floodplains in the immediate area per the available FEMA map. The site is located in Zone X per the Flood Insurance Rate Map (FIRM) map number 53033C0991 F. See Figure 5 in Appendix A for �copy of the FIRM map. Sensitive Areas • Wetlands—There is a small wetland located to the west of the Wetpond for the site. • Streams and 100 Year Flood Plains—There are no streams or flood plains mapped on site. • Erosion Hazard Areas—The project site is located in an erosion hazard area. See Core Requirement#5 for a detailed explanation of the measures of prevention that will be taken. • Landslide Hazard Areas—There are no landslide hazard areas mapped in this area. • Seismic Hazard Areas—This site is not within in a mapped seismic hazard area. • Coal Mine Hazard Areas—None mapped in #his area. U.S. Department of Agriculture, King County Soils Survev • The soil on the site is classified as Alderwo�d gravelly sandy loam, 15 to 30 percent slopes (AgD) in the US Geological Survey of King County Area, Washingfon. Alderwood is characterized as moderately well drained soils. The surface layer and subsoil are gravelly, sandy loam extending to a depth of 27 inches. The substratum is weakly to strongly consolidated giacial till that extends to a depth of 60 inches or more. Figure 4 in Appendix A presents the soil sur�ey for the project area. Flo��v Con±rol Applications Map • The site is located in a Level 2 area of Flow Control. �^Jater Quality Applications Map • Tne site is !�cated in a B�s;c '�^��'a'er t�uaGt,�T�ea'mert Area. LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report 2 October 11,2006 � Landslide Hazard Drainaqe Area Map • The site is not located in a landslide hazard drainage area. Task 3: Field Inspect the Study Area Representatives of Site Development Associates, LLC (SDA) made a site visit to the property on March 6`�', 2006. The weather conditions were dry, 65 degrees and partly cloudy. The fieid investigation covered approximately'/<mile downstream of the site. Task 4: Describe the Drainage System, and its Existing and Predicted Problems Upstream Drainaqe Analysis: The southem portion of the site is located near the top of a hill as the hill starts to gently slope northeast. The runoff from the adjacent properties to the south of the project are collected by the existing conveyance system and routed away from the site along SE 100'h Place. There may be a small amount of runoff that would enter the project site from the back of the lots located on SE 1Q0`h Plaec. However, this amount of runoff is insignificant and will not have an effect on the drainage analysis of this project_ On-Site Drainaqe Analvsis: The project area is 33.02 acres in size, 16.35 acres of which is de�elopable mainly on the southern portion of the site. The southern portion of the site is a plateau that slopes gently to moderately to the northeast at approximately an 11 percent slope. Moving north to about the middie of the property, the siope changes to a steeper grade. The slope on the western half of the site changes direction to the north and is greater than 40% at some locations. The eastern half of the site continues to s{ope to the northeast and the grade increases to approximately 22%, with a few locations exceeding a 40% slope. The cover on the site is mainly dense forest conditions with undergrowth,with the exception of the landscaping around the existing structures. Please reference Figure 2 for the existing site survey of the properties and Figure 3 for proposed site layout of the development. Downstream Drainaqe Analysis: Currently, the flow on the Langleyridge proposed site flows by way of o�erland fiow down the slope and into May Creek. h9ay Creek then trave(s west to the limits of the downstream analysis. The proposed conveyance system will collect the storm water runoff from the southern plateau and route it down the hill, along the east side of the project, �ia an enclosed drainage piping system. The conveyance system will outlet into the lined water quality pre-settling pond and then into the infiitration pond. The detained storm water wiii make its way to May Creek�ia infiltration and ground water recharge. The flow will then folfow the existing downstream drainage course. Task 5: Addressing Mitigation of Existing and Potential Problems The development of this project is not expected to have an adverse impact to the downstream drainage system. Drainage for the 34 lot subdivision will meet City of Renton requirements for detention, infiltration; and water quaiity. Core Requirement No. 3 - Flow Control The proposed project is located in a Level 2 Flow Control Area. The Level 2 Flow Control requires the developed flow rates discharge to the prede�eloped flow rates ranging from 50°10 of the 2-year peak flow up to the full 50-year peak flow. See AE�pendix C for infi�tration calculations. Core Requirement No. 4- Conveyance System The ��roposed co�;ve�,�a�ce system �vi!I incluce cu�b, catch basins. ancf a p;�:e ner�r�er4 for coilection and routing of ihe Sf0 rIl '.V"c3tE( 'Ur,<� ` C'�R� t"�2 (�2'.�. :�'`S_ F'COC�t C�Oa�.`iS�CUIS :'�'I�! JF'. fOi�i@ij lO iflt� COf".8,��'�CP 5 j���t"11 Vla ',ICIh' �I"�P 5,,'titBRl LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report 3 October 11,2006 The storm drainage system wiil convey the peak flow from 25-year storm event. The conveyance system can handie the 100-year storm event and this storm wifl not crea#e or aggravate a"severe flooding problem". See Appendix C for conveyance caiculations. Core Requirement No. 5 — Erosion and Sediment Control , In order to protect the downstream conditions from sediments, several erosion control Best Management Practices II (BMP's)from the King County Suriace Water Design Manual wili be utilized. During and after grading, and during house construction, the site will be stabilized with appropriate BMP's consisting of silt fencing, mulching and hydroseeding. A temporary construction entrance wili be installed for construction related traffic. Filter fabric will be placed over catch basin grates. All yard areas wiii be landscaped. Additionally, limiting earthwork and utility construction activities to dry weather conditions, minimizing area and duration of soil exposure, construction of temporary storage basins and protective dikes to control storm runoff, and stockpiling and sheathing of strippings, will further reduce the potential for silt-laden runoff. Interim measures to be employed during construction will inciude the canstruction of sediment basins, the installation of silt fences along the low side o#the areas to be cleared and graded, and mulching and hydroseeding of exposed soils after attainment of final grade. Stockpiles will be covered with polyethylene sheathing. Additional erosion control measures by individual builders are recommended during construction of houses. These should include installation of a silt fence at the roadside, placing a bed of builder's sand between the house and the street, and covering stockpiles. Purpose of Plan The Temporary Erosion and Sediment Control (TESC) Plan describes the temporary BMPs selected for storm water detention and water quality treatment during construction of this project. A BMP is a physical, structural, andlor managerial practice that prevents or reduces the pollution of water. The goal of the TESC Plan is to prevent turbid discharges and sediments from leaving the site and to meet Water Quality Standards as defined in WAC 173-201A. Should field conditions during construction require additional temporary BMPs or if a change in placement of temporary BMPs is needed, this plan shall be modified by the developer. The objectives of this TESC Plan are to: • Implement BMPs to minimize erosion and sedimentation from rainfall at construction sites, and to identify, reduce, eliminate, or prevent the pollution of storm water. • Prevent violations of surface water quality, ground wa#er quality, or sediment management standards. • Prevent, during the construction phase, adverse water quality impacts including impacts on beneficial uses of the receiving water by control(ing peak rates and volumes of storm water runoff at outfalls and downstream of the outfalls. Erosion and Sediment Control Minimum Requirements Minimum requirements of the 2005 King County Surface Water Design Manual for erosion and sediment control wi!I be , implemented during the design and construction of this project. These requirements include the following: Stablization and Sediment Trappinq All exposed and unworked soils shall be stabilized according to the following criteria: From October 1 to April 30, no exposed and unworked soils shall remain unstabilized (exposed}for more than two days. Non-erodible, clean, granular base materials shall be applied to stabilize all trafficked areas. From May 1 to September 3Q, no exposed and unworked soils on slopes shali remain unstabilized (exposed)for more than seven days. Delineate Clearinq and Easement Limits All existing vegetation (trees, bushes, shrubs, grasses)shall be preserved when not required for the construction of the project. The Contractor is required to survey, stake, and flag the clearing limits shown in the Plans and(or areas not to LANGLEYRIDGE SUBDIVISION 4 Final Storm Drainage Report October 11,2006 be disturbed including easements, setbacks, sensiti�e and critical areas and associated buffers, and buffers for drainage courses before any clearing or grubbing can begin. Proiection of Adiacent Properties Properties adjacent to the project site shall be fully protected from sediment deposition. Suitable sediment traps shall be installed on the project site to prevent sediment runoff. Timinq of Sediment Trappinq Measures Sediment ponds and traps, perimeter dikes, sedirnent barriers, and other BMPs intended to trap sediment on site shall be constructed as a first step prior to any land disturbing activities. These BMPs shall be functional before land disturbing activities take place. Ea�then structures such as dams, dikes, and diversions shall be seeded and mulched, or otherwise stabilized, according to the timing and dates indicated above. Cut and Fill Slopes Cut and fill slopes shall be constructed in a manner that will minimize erosion. Cut and fill slopes shall have erosion control BMPs installed for slope protection as needed. During construction, exposed slopes shall have seed, fertilizer, and mulch applied. When seeding and mulching are not possible, piastic covering or other suitable cover shall be applied. Finished slopes shall have permanent seeding applied between March 1 and May 15 or August 15 and October , 1. Outside these specified application periods, temporary cover shall be applied. Storm Drain Inlet Protection All storm drain inlets used to discharge runoff from the construction site shall be protected so that storm water runoff shall not enter the conveyance system without first being filtered or otherwise treated to remove sediment. Underqround Utility Construction No more than 500 feet of storm drain or utility trench shall be opened at one time. Where consistent with safety and space considerations, excavated material shall be placed on the uphill side of the trench. All de-watering devices shal! discharge into a sediment trap or sediment pond. Construction Access Routes Where�er construction vehicle access routes intersect paved roads, provisions must be made to minimize the transport of sediment and mud onto the paved roads. If sediment is transported onto a road surface, the road shall be cleaned thoroughly at the end of each day. Sediment shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Removal of Temporarv BPM's All temporary erosion and sediment control BMP's shall be removed within 30 days after final site stabilization is achieved. The Contractor shall remove the item,then clean, restore and permanently stabilize all disturbed areas. �� Trapped sediment shall be removed or stabilized on site. Dewaterinq Construction Sites Dewatering devices shall discharge into a sediment trap or sediment pond. The rate of dewatering discharge shall not exceed the design capacity of the sediment trap or pond. If required in the project's special provisions a dewatering plan shall be submitted for approval before implementation. In the event that the contractor shall encounter areas that require dewatering no work, except the erosion control measures as needed to remedy unforeseen water quality problems, shall commence or continue until a dewatering plan approved by City of Renton, is obtained. The Developer shall be responsible for preparing, submitting, and obtaining approval for dewatering plans in such situations. Maintenance All temporary and permanent erosion control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. LANGLEYRIDGE SUBDIVISION 5 Final Storm Drainage Report October 11,2006 Temporary Erosion and Sediment Control BMPS This section presents the temporary BMPs that were selected to control erosion and sediment during construction of this project. The BMPs selected include Source Control BMPs, Sediment Control BMPs, and Structural Erosion Control Bt�1Ps. The type and location of TESC BMPs used during canstruction may vary from those presented below. This plan may be modified by the Developer in the field as necessary to controi erosion and the migration of sediments at the project site. The proposed locations of the selected TESC BMPs are presented on the TESC Plan Sheets. Source Control BMPS Source control BMPs selected for this project inc(ude seeding and mulching. Sediment Control BMPS The BMPs selected for the controi of sediment include filter fence, check dams, storm drain iniet protection, and sediment traps. Structural Erosion Contral BMPS Structurai Erosion Control BMPs selected include stabilized construction entrance and interceptor swale. Water Quality Monitoring The City of Renton may determine that water quality monitoring is warranted. If needed, the Developer shall measure turbidity, pH and temperature at all of the identified site discharge points after each 24-hour rainfall events of 0.5 inches or greatar. If turbidity at any of the site discharge points exceeds the water quality standards (WAC 173-201A), then the De�eloper shall make appropriate adjustments to the TESC plan. Turbidity will be measured with a HACH 2100P portable turbidity meter or equivalent and reported in Nephelometric Turbidity Units (NTUs}. Core Requirement No. 6 — Maintenance and Operations See Appendix D for the Maintenance and Operaiions Manual for the �angleyridge Subdivision. Core Requirement No. 7 — Financial Guarantees and Liability The Financial Guarantees and Liabilities wiil be required prior to the project being finalized by City of Renton. Core Requirement No. 8 —Water Quality The project will provide basic water quality prior to discharge to the infiltration pond on the project site. Water quality will be accomplished in a #ined water quality pre-settling pand. See Appendix C far`vater quality calculations. Special Requirement No. 1 — Other Adopted Area-Specific Requirements The project is located within the Ceuar River! Lake Washington Watershed, in the Cedar-Sammamish Water Resource Inventory Area (WRIA}8. Special Requirement No. 2 — Floodplain/Floodway Delineation This requirement daes not apply. LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report 6 October 11,2006 Special Requirement No. 3 - Flood Protection Facilities This requirement does not apply. Special Requirement No. 4- Source Controls This requirement does not appiy because the project is located in the basic water qua{ity treatment area. Special Requirement No. 5 - Oil Control This requirement does not appiy. LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report 7 October 11,2006 APPENDIX A - FIGURES Vicinity Map 1 Existing Topography 2 Proposed Site Layout 3 Soils Map 4 FIRM Map 5 WELMAN SUBDIVISION Level One Downstream Analysis �� �� x -�- • ' r �!cr� G Od, p � `s�: ^ _ — _ '�j, €�, •""" � ^f � h A , � a a�u»t� � � I 'ri x � � j � v. a.`°� ! y . "na� I rs � s �� 1.' � r 2� M �1�HiS�i � ° �, LiJ � �ur>t � � 5 �, ��.., � � ,� �o �� �,V, /. f'' ��� r��.v 1 ..-�` - .�Pt�,� � ,� ,u � � W I ;� �R S . ���s�; ,y�T' �ni � � N ��I�� � .�y r `M �e`H� f,�� .3N AY . 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'�� 1�� i.- ��ll �s . o I � WPH N NK�9" � � � LANGLEY RIDGE N.T.S. _ Drewn Scele � 2006-03-17 Site Development Associates, LLC oeta ,��,�W�,N��,�.W�,����,�„ soi�s 4 0 107-012-05 omce:�as.�av.� r� azs.�.ssvs www�a��#»en.com � Project No. MAP Figure No. � APPROXIMATE SCALE IN FEET 500 0 500 Mqy �A�LEY � ROqa RM215 P Q � � m Q�' '9 � "' N N � RM216 ^ � Q � NATIONAL FLOOD INSURANCE PR06RAM IIIIIIIIIIIIII v'p� o c� r�j E AC o,0 � a ' , �y '�', Q,` `� �i9� 743RD A�� S� � � � FIRM 2�2 � � � FLOOD INSURANCE RATE MAP N � Q ' -� � 1� �E � ,, KING COUNTY, WASHINGTON AND .,�`'�;',€ INCORPORATED AR,EAS `T "� PANEL 669 OF fl25 iSEE MAP INDEX FOR PANELS NOT PRINTEDI � P� � _ � corvraNs S t T� g c:OMMUNItt NUMBEfl PANEI SUFFIX RING COUNiV. UNINCOflPOMiED AREAS 5700T ObCO f S�U7'HE/�ST aFNtnrv,r,m ov a�ro�e nam r � SE 100TH STREET 100TH STRFET KING COUNTY CITY OF RENTON MAP N0M8ER NE 23FD STREET � 53033C0669 f � � � � o = �� ,. -� MAP REYISED: N � = v �_�^� .� MAY 16,1995 z Jw ` o NF � �, m � �� Q 2 21ST STREET m I W p ¢ Pederal Emergency Management Agency � w x NE 20TH � PLACE � � This is an of�cial coF�y of a portlon of the abooe referenced flood map. tt wea extracted usinfl F-MIT On-Line. This map does nd rellect chanpes or amendments which may have been made suhnequent to the date on the tltle Wock. For the letest product informatlon about Netlonal Flood Ineurance (n Proqram 11ootl maps check the FEMA Flood Map Store at wwvv.msc.fema.gov October 11,2006 APPENDIX B - DOWNSTREAM ANALYSIS Downstream Analysis Basin Map 1 Drainage System Table 2 Drainage Key Map 3 WELMAN SUBDIVISION Level One Downstream Analysis October 11,2006 DOWNSTREAM ANALYSIS BASIN MAP LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report � � � � Page 1 of 1 '�' NCing C��nty iMAP - Kin Coun Water Features �;��' �'� z Legend �'� . . � y" �, �/ County 8oundery , , ... , .� ..— • ti � � • � * �� � . � � 1 ,,� �� � ;t ' ' Ifgnvxaqs . � � `1 �, � IAYegnsory�l�y lYWeb9f t�9souroe �,; ,. z ,, � �' � �i� �� � � `�� �-r' � ICing C�nunty Orainage �`. ��r�' s2o . BBaifls _- ,�•.,. � , � �� ��' ��r Lek6s and Lalge F3"�t�ra � l '� � o � � �;� � ' � ,� ,� 4 j � ;t � � w� . �� ,�� `- -, ^ �"'""'� Inbotporei�d Area - , � � Ar , - � jr�' ,' I �;g.^f A...�,�i �����kq'� ' ��, a�'a, u ``�•�C . -� � �',� k hi�+ - .��,.� �,.. � �j � p�� �, �� M� 1 G�Dh�R•5►1►r+Mh�+t sH wR�A .�� ,�.��,���� _ �� � � sw DR ; ; f. :,�� ��f�� 187 �,18 4't` �1�.,-.. ,7. � � Y4" �,� �1F'�.. i.. � ��. _ .� .��� ...� Jf��. } ,� ��� �, '� .. .4i � � � f r "�i.,,"y,. ,�,. IiF � 1 � ��' 4 16 xq r�' 187 `4}, ,r. u�'�.i � ��� I� � � �v 4 �nm.,,�. �. O ' 1512 ���' � ,�"'� '4 �'�����,/v �C)Ydd6 N�in+p,Coumiy� ci..r� i —"" ` ^• �-� � ` 4 Counry. Date:4-5-2006 Source:King County iMAP-Stormwater (http://www.metrokc.govlGlS/iMAP) COMMENTS:Draina e Basin Ma http://��-ww5.metrokc.gov/servlcUcom.esri.esrimap.Esrimap?ServiceName=overview&ClientVersion=4.0&Fornl=True&Encode=.. 4/5/�(1(l� October 11,2006 DRAINAGE SYSTEM TABLE LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report LANGLEYRIDGE - OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT#2 Basin: May Creek Subbasin Subbasin Name: Number: - -__ —_—____ -- --.__ __ _�__ Symbol Drainage Drainage Slope Distance Existing Potential Observations of field Component Type, Component from site Problems Problems inspector, resource Name, and Size Descri tion dischar e reviewer, or resident see map Type:sheet flow,swale, drainage basin,vegetation, % Y<ml=1,320 ft. constrictions,under capacity,ponding, tributary area,likelihood of problem, stream,channel, pipe, cover,depth,type of sensitive overtopping,flooding,habitat or organism overflow pathways,potential impacts pond; Size:diameter, area,volume destruction,scouring,bank sloughing, surface area sedimentation,incision,other erosion _--- _ _.-- ---. A Driveway Sheet Flow Flows from the driveway sheet 2% 1,000' None None None Observed flow to the pond. g Driveway Sheet Flow Flows from the driveway sheet 2% 1,000' None None None Observed flow to the pond. C Existing Pond /Sheet Existing residence and garage 0 1,000' None None None Observed FIOw sheet flow to the pond. Pond flows overland to the parcel below. Pond is approximately 4'dee and 42'in diameter. p Driveway Sheet Flow Flows from the driveway <2% 1,300' None None None Observed sheetflow to the pond. E Plateau Slopes/ Runoff from the plateau sheet >�o°io 1,000 None None None Observed Sheet Flow flows down this heavily forested slope and through the dense undergrowth towards Ma Creek. F Plateau Slopes/ Runoff from the plateau sheet io-zo% 800' None None None Observed Sheet Flow flows down this heavily with forested slope and through the some dense undergrowth towards areas Ma Creek. over 40°/a G Plateau Slopes/ Runoff from the plateau sheet �o-2o°io 700' None None None Observed Sheet Flow flows down this heavily with forested slope and through the some dense undergrowth towards areas Ma Creek. over 40% �-{ Plateau Slopes/ Runoff from the plateau sheet �0-20% 600' None None None Observed Sheet Flow flows down this heavily with forested slope and through the some dense undergrowth towards areas May Creek. over 40% cAprojccts\107(offc)�012-05(langlcyridge)Areport\appendixb\drainagc system table.duc -- __ __ _ _ . __ ._. �._ -- - -- - __ _ _�-�_ _ Symbol Drainage Drainage Slope Distance Existing Potentiai Observations of field I Component Type, Component from site Problems Problems inspector, resource Name, and Size Descri tion dischar e reviewer, or resident see map Type:sheet flow,swale, drainage basin,vegetatfon, % Y,ml=1,320 ft. constrictions,under capacity,ponding, tributary area,likelihood of problem, stream,channel,pipe, cover,depth,type of sensitive oveRopping,flooding,habitat or organism overflow pathways,potential impacts pond;Size:diameter, area,volume destruction,scouring,bank sloughing, surface area sedimentation,incision,other erosion � Plateau Slopes / Runoff from the plateau sheet 11% 550' None None None Observed Sheet Flow flows down this heavily forested slope and through the dense undergrowth towards Ma Creek. � Sheet Flow Runoff from plateau flows <s°iodi 65' None None Flow must be directed around through this residence the new residence to avoid construction site and into May creek. excess runoff entering this ro ert . K Sheet Flow Runoff from the plateau flows <3°io 150' None None None Observed along the east property line and into Ma Creek. � Sheet Flow Runoff from the plateau flows <3% 320' None None None Observed along the east property line and into Ma Creek. M May Creek Runoff from project site enters <2°io 0' None None None Observed May Creek and flows to the west. Creek channel width is a roximatel 5 to 20 feet. N May Creek Runoff from project site enters <2% 0' None None None Observed May Creek and flows to the west. Creek channel width is a roximatel 5 to 20 feet. r:\projectsV 07(offe)\012-OS(langleyridge)�report�appendixb\drainage system table.doc October 11, 2006 . � i � _ � DRAINAGE KEY MAP II I , � � ._,, ; ,_� ;") _ ��� �� � � �_; � , , 1 I , ) \i � ; J �� , LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report - � - ---_ _ - ��� �--- - _. _ �� _ � 3 @., � � I ___,�c�"p �, I � �°� � � - - - - - - � I` 3�0 I ` I ( � � 3l� I I � � N 5 01'22'33"W `�f2 8.00' �-� — I eu.aMc — — — -- — — — — — � I ew:w S 88'37'27" E — — — I � '� '� - 130.67 4 � � Q 3� I � �j 314 I � O �/^ 3,8 'p� � �.m . I � � � V; � �� � I I I � � � � � � � i i - i a � �' - 3K I I � 0 1 II� � 318 �,<r ��.:`� � I . � � I 320 � .: ,+. 3�0�I �n � I �� � I � I � 33,~ 322 � ' � �0 29'', 3 , :=�'�;: � I � � 3�. 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I � � I � I' f ICICLE CREEK ENGINEERS Dail Field Re ort Prepared by: Colin B Turnbull Project No: 0133-012 Date:9/17/OS Location: East of the 62nd Ave SE/SE 326 St Arrival:0900 Signa ture: � Intersection,Aubum,King County Weatlier:Cloudy/60's °F Project: Langley Ridge at May Valley Deparnue: 14�0 King County Parcel Nos.0332305- 9002,9071,9073,9247 and 9248 Reviewed by: Brian Beaman Client: Langley Development Group,Inc. Page: 1 of 1 Report No: 1 Distribution: Attachments: C.Thomas Foster, Langley Development Group,Inc. Site Plan,Test Pit Logs (Photos-ICE File) At the request of C. Thomas Foster, Langley Development Group, Inc.(LDG), Colin Turnbull of Icicle Creek Engineers (ICE) conducted a site visit to excavate test pits and conduct infiltration testing at the project site within the proposed infiltration pond area. The project site currently referred to as"Langley Ridge at May Valley,"consists of about 25 acres and is located north of the intersection of SE 100th Place and 140th Avenue SE. ICE previously completed a preliminary geotechnical evaluation of the property as referenced below together with the current design plans. • Hanson Surveying,June 29,2005,"Preliminary Plat of Langley Ridge at May Creek",prepared for LDG, 10 sheets. • ICE, June 20, 2005, "Report, Preliminary Geotechnical Engineering Senrices, Langley Ridge at May Valley," prepared for LDG, 12 pages and attachments. 'i According to regional geologic mapping by the University of Washington(UW)(Booth,D. B., Cox,B. F., Troost,K. G., and Shimel S.A.,2004, "Composite Geologic Map of the Sno-King Area, Washington," Seattle-Area Geologic Mapping Project, ' scale 1:24,000), the infiltration pond area is mantled with recessional outwash (medium dense sand and gravel), and is underlain by older,glacially-overridden sediments(hard silt and dense sand and gravel). Subsurface conditions within the proposed infiltrarion pond area were explored by excavating three test pits on September 17, 2005 using a track-mounted excavator(Yutani MD140)owned and operated by R.A. Holmes Construction Co. and contracted by LDG. The test pits were completed to depths ranging from 16 to 17.5 feet below the existing ground surface. The test pit locations were based on existing site conditions, access and the proposed stormwater infiltration pond locarion. The approximate test pit locations as shown on the attached Site Plan. The test pits were logged by an engineering geologist from our fum and visually classified in general accordance with the classificarion system. The logs of the test pits are attached Two infiltration tests were conducted at the elevation of the proposed pond bottom. The infiltration tests were conducted in general accordance with the 1998 King County Surface Water Design Manual (King County SWDM, Chapter 5.4) using the U.S. Environmental Protection Agency's (EPA's) Falling Head Percolation Test procedures. The test sites were prepared by carefully excavating a hole approximately 1 foot deep then placing a 12-inch diameter pipe(riser)vertically into the ground. The sides of the pipes were sealed with excavated soil. Water was provided using a hose connected to a nearby hose-bib. The tests sites were soaked for a maximum of 20 minutes. During the soaking period«-ater was applied a rate of I S gallons-per-minute in order to achieve a"standing water"condition(at least one foot of water)within the pipe riser. Subsurface condirions at the site were explored by excavating three test pits along the north-south centerline of the proposed infiltration pond bottom. Soil conditions observed in Test Pits TP-12 and TP-14��•ere similar and encountered a surficial layer of about 4 inches of topsoil overlying about 2.7 to 3.2 feet of�y�eathered soil consisting of inedium dense silty sand with occasional gravel and a trace of roots. The weathered soil was underlain by recessional ourivash consisting of inedium dense sand and gravel with occasional cobbles and a trace of silt to the completion depth of the test pits at 17.5 and 16.5 respectively. Soil conditions observed in the Test Pit TP-13 encountered a surficial layer of about 7 inches of topsoil overlying about 8.4 feet of���eathered soil consisting of inedium dense silty sand overlying medium stiff to stiff, silt, overlying medium dense sand with occasional gravel and a trace of silt. The weathered soil was underlain by recessional ouhvash consisting of inediurn dense sand with gravel and occasional cobbles to the completion depth of the test pit at 16 feet. Icicle Creek Engineers,Inc.,230 NE Juniper Street,Suite 101,Issaquah,W'ashington 9802? Telephone:(425)427-818? Fax: (42�)427-6629 5.4.1 GENERAL REQUIREMENTS FOR INFILTRATION FACILITIES � of less than 1 acre,the groundwater modeling requirement may be replaced with use of the simplified analysis method described below along with full-scale testing of the completed facility to verify performance. Groundwater modeling(mounding analysis)of the proposed infiltration faciliry shall be done using the design infiltration rate and the estimated maximum groundwater elevation detemiined for the proposed facility location. MODRET or an equivalent model must be used unless DDES approves an alternative analytic technique. Developed condition hydrographs should be exported from the KCRTS model of the project site for the groundwater mounding analysis. Test hydrographs should include at a minimum the full year 8 synthetic record and at least one other runoff event that is the highest volwne,peak-flow event identified through KCRTS analysis of the infiltration facility. Note that an iterative process may be required beginning with an estimated design rate,KCRTS sizing,then groundwater model testing. Simplified Method A simplified method may be used for determining the preliminary design infiltration rate by applying � correction factors to the measured infiltration rate. The correction factors account for uncertainties in testing,depth to the water table or impervious strata,infiltration receptor geometry, and long-term reductions in permeability due to biological activiry and accumulation of fines. Equation 5-9 has been developed to account for these factors. This equation estimates the maacimum design infiltration rate �Id�:gn);additional reduction in rate beyond that produced by the equation may be appropriate. Note that the design infiltration rate Id�;g„must not exceed 20 inches/hour. ---_ , Idesign — Imeasured X�`!esling X Fgeometrv X Fp(ugging � �5-1�� Correction factor F1PS1;,,g accounts for uncertainties in the testing methods. For the EPA method,Fresrtng = 0.30; for the ASTM D3385 method or large-scale testing�Fr���ng=0.50 Fgeome,ry accounts for the influence of facility geometry and depth to the water table or impervious strata on the actual infiltration rate. A shallow water table or impervious layer will reduce the effective infiltration rate of a large pond,but this will not be reflected in a small scale test. Clearly,a large pond built over a thin pervious stratum with a shallow water table will not function as well as the same pond built over a thick pervious stratum with a deep water table. FgeO,,fer,y must be between 0.25 and 1.0 as determined by the following equation: FgeO1„e!ry=4 D/W+0.05 (5-12) where D = depth from the bottom of the proposed facility to the maximum wet-season water table or nearest impervious layer,whichever is less Y3' = width of the facility Fprugg;,,g accounts for reductions in infiltration rates over the long term due to plugging of soils. This factor is: • 0.7 for loams and sandy loams • 0.8 for fine sands and loamy sands • 0.9 for medium sands • 1.0 for coarse sands or cobbles,or any soil type in an infiltration facility preceded by a water qualit}� facility. ' 2005 Surface VJater Design Manual l;'24i2U0� 5-59 0133-012 09/19/OS Page 2 of 2 No ground water was observed in the test pit explorations. Ground water may be present in the early Spring months and should be evaluated at that rime. INFILTRATION POND—FIELD INFILTRATION TEST RESULTS The results of our field infiltration tests indicate an minimum infiltrarion rate of 428 inches-per-hour(iph)in Test Pits TP- 12 and TP-14. This value should be reduced by a factor of 8, based on recent recommended guidelines by King County Department of Development and Environmental Sen�ices on other projects, to allow for scaling up from a small-scale test to a large scale test. Therefore, in our opinion, a field infiltration rate of 54 iph should be used for designing the infiltrarion pond if infiltrarion pond footprint is adjusted to the north away from the area around TP-13. TP-12 TP-13 TP-14 IT-1 mid-section IT-2 south end IT-3 north end Water Level Time Water Level Time Water Level Time feet secs inches secs inches secs 2.0 0 1.9 9 1.8 12 1.7 19 1.6 26 1.5 31 1.4 40 13 44 1.2 50 1.1 69 1.0 75 0.9 83 0.8 96 0.7 105 0.6 120 0.5 135 0.4 156 03 164 0.2 176 0.1 190 0.0 202 202 seconds for 24 inches Poor infiltration Equal or greater than flow =428 inches per hour —test abandoned rate of 780 inches per hour (3-inches of standing water) ��,eGSwQa Icicle Creek Engineers,Inc.,230 NE Juniper Street,Suite 101,Issaquah,Washington 98027 Telephone:(425)427-8187 Fax:(425)427-6629 ICE File No. 0133-012 CBT:03/30/05 . �.� v, � , _ N �„ _...- ^ ,.TM �as - __,-'-, ��,;; �Ni�r � 4 ,, ,� May Creek � w i - , �'� �. or� .n� _ __ �.', , � , " `�, + '1 �,� �3 u� � �;� �,, ----� „�i s: , �R,�v _�....... _ . ..� .;�,G"`.. ``;._�r Parcel Boundary % :,,, _ ,. ���✓�5. Proposed Stormwater �� �.-yrt Infiltration Area (approximate) �` N`` — � ,�.. � w...._ ��—� Ere�_ '�Q � ��-��"�� ,,�1;''��' , � yN�( r_ _ - ,�: w _ . ^ , r . .� �,t' - —..- Y/ �' 7 � �F� i.� F+y 1 .� . . _ * � }-� /� �-„ 4J1 ' i- �.._._�� \V`iY���(i� i shF�� '�. �4 �'1�Z.(' ,I' � ��� �� ..�� — � ' �.y V Y � . 1 —__ ` ' ` ,�• __ -,._ _ � ____�� , r � . �---__ ' _ __ Elev,�410' _ �a�M �;_ _ � __ _. .....,. _ ` ,.,� r ,,_-_. _ _- �-�—•---� �_ - � . �. �.�1i ,, �� � {j.�..r . `'' ` '! i .. .. } ...'� "`;�., . r�m. a �I�� y _,. ...,i I'... [II._....,_..l�`�i / I�i +v. / ' " - , �—�— � � _ � �—� , �� � _ s , : , , _. � -�� I .-,'�.�.• �TP 3 i `� � � • ��;I�" � ��, � �_ ...i � _m. `�/' _ . � ,� � � � y x'�'J ' __ . 'c�7 , - _.� �__�f. -- __-- r �" � �' - - � „� � � _ ,. ��' � a Existing --•---�-_�,._.,�{ SE 99th Court _ .. �"� � � Houses � y�. C e __ __�_�---�-_. y ;.�. . �1 � a 2 -�- ; , � ,�- --- ;--_-_��----� TP-2 � ' � , P-� �-�- � Explanation: __�TP-7 � ; ", p�� � � TP-5 , � /� �TP-12 — _______.._�---_. _..._�_.�.._.._..---.�_ / Test Pit Location Proposed PnvateAccess Road , Y ._:' (ICE September'05) �.��,_......_.._. � TP-6 Z �..,m�__... ...__.�_.__..,_._ __....._, t1 ' - _...__ ' . i ' �� � __.__._. ..__j Test Pit Location � -{�- � _ � � � TP_8 � j (ICE March'05) ; : � � , � ,,,,.____ . TP Protected Slope ` { � ! Easement � � (40%or greater siope) w �� w � Proposed Lot Boundaries �, � � � a� � Sensitive Slope r- � � � �i rea � (25 to 40%slope) Q � > Q F SE 100th Place Notes: 0 200 400 1)Lot boundaries provided by Hanson Consulting,undated. 2)Topographic data provided by Offe Engineers,dated June 30,2005,titled"Preliminary Plat of Langley Ridge at May Creek, Approximate Scale in Feet Conceptual Drainage and Utility Plan". 3)Parcel boundary obtained from Interactive Mapping(iMAP)King County(http://www.metrokc.gov/gis),dated 2002. 4)Elev.=Elevation in feet. Icicle Creek En ineers Site Plan Test Pit TP-12 CLIENT Lanqlev Development Group, Inc. PROJECT NAME Proposed Residential Plat. Lanqlev Ridqe at Mav ValleY PROJECT NUMBER 0133-012 PRO.IECT LOCA710N North of 140th Ave SE and 141st Ave SE DATE EXCAVATED 9/17/05 TOTAL DEPTH 17.5 ft GROUND ELEVATION 327 ft(approx.) LOGGED BY CBT EXCAVATION CONTRACTOR R.A.Holmes Construction Co. GROUND WATER None observed CHECKED BY BRB EXCAVATION EQUIPMENT Yutani MD140 track-mounted excavator NOTES Stormwater infiltration site ' w 2 � � a0 �w ai w� MATERIAL DESCRIPTION �� a p �� �� � REMARKS o w � �� QZ � 0 � 3 Dark brown SILT with abundant roots�ver�soft1moistLLesoil)___�� 327 -- ML , �Light brown silty fine to medium SAND with occasional grave�and a trace of SM � ��_ 3.0 roots medium dense moist weathered soil 32a .-.— �---L-----1--��-----�-----------� - �_-.-�. - Brown and gray medium to coarse SAND and GRAVEL with occasional p:::: cobbles and a trace of silt(medium dense,moist) (recessional outwash) �'�` a: .:a.. Sp_ �:?.'.�.��'. v., GP 10 ,;a:;;; '::o- 1 o.: 13.0 --- 314 ';�:: Brown and gray silty medium to coarse SAND and silty GRAVEL with — occasional cobbles(medium dense,moist) (recessional outwash) �YT� SM- _-� GM 17.5 310 r— Test pit completed at 17.5 feet on 9l17/05 Moderate cavin of sidewalls below 3.0 feet o groun water seepage observe Test Pit TP-13 'I CLIENT La_ngley Development Group. Inc. PROJECT NAME Proposed Residential Plat, LanqleV Ridqe at May Vallev PROJEC7 NUMBER 0133-012 PROJECT LOCATION North of 140th Ave SE and 141st Ave SE DATE EXCAVATED 9/17/05 TOTAL DEPTH 16.0 ft GROUND ELEVATION 329 ft(approx.) LOGGED BY CBT EXCAVATION CONTRACTOR R.A.Holmes Construction Co. GROUND WATER None observed CHECKED BY BRB EXCAVATION EQUIPMENT Yutani MD140 track-mounted exqvator NOTES Stormwater infiltration site w p U a� }� � a� MATERIAL DESCRIPTION Q� =C9 �O �w cn w.� >� a O �� �� � REMARKS o W � �,� QZ g o � .fi Dark brown SILT with abundant roots�ver�soft�moistL(topso�___,, 328 ML Light brown silty fine SAND(medium dense,moist) (weathered soil) =— a — -' SM � � 6.0 323 _ — � 7,5 Light gray mottled orange SILT(medium stiff to stiff,moist) (weathered soil) 322 = ML 2 � g p Gray medium to coarse SAND with occasional gravel and a trace of silt g20 SP 0 10 �_(medium dense�moistL(weathered soilZ____________�� — -_=_ � Brown and gray silty medium to coarse SAND with gravel and occasional -' � cobbles(medium dense,moist) (recessional outwash) _� SM 3 a -- e- � --- -�. � q 160 313 .-" - � Test pit completed at 16.0 feet on 9/17/05 � Moderate caving of sidewalls from 7.5 to 9.0 feet � No ground water seepage observed x a � w U Icicle Creek Engineers Test Pit TP-14 CLIENT Lanqlev Development Group. Inc. PROJECT NAME Proposed Residentiai Plat, Lanqlev Ridqe at Mav Vallev PROJECT NUMBER 0133-012 PROJECT LOCATION North of 140th Ave SE and 141st Ave SE DATE EXCAVATED 9/17/05 TOTAL DEPTH 16.5 ft GROUND ELEVATION 326 ft(approx.) LOGGED BY CBT EXCAVATION CONTRACTOR R.A.Holmes Construction Co. GROUND WATER None observed CHECKED BY BRB EXCAVATION EQUIPMENT Yutani MD140 track-mounted excavator NOTES Stormwater infiltration site w Z c� � a� � a� MATERIAL DESCRIPTION Q� � � w � � = n'O W,� ]" a p O�� w� � REMARKS o W � c,� QZ g o �' 3 Dark brown SILT with abundant roots�ver�soft�moistLLpsoil)___�� 326 =— ML �Light brown silty fne to medium SAND with occasional gravel and a trace of � SM 3.5 roots medium dense moist weathered soil 323. '-�T ----L-----1--ZL-----�------------ ���. — Brown and gray medium to coarse SAND and GRAVEL with occasionah y:�. cobbles and a trace of silt(medium dense,mast) (recessional outwash) ::.ia. :o:: �'�''�::v.. P...O 10 :a:::: SP- �::a: GP :fl.:; ;:.�::. '.ai:.o :o:': 16.5 310 : Test pit completed at 16.5 feet on 9/17/05 Moderate caving of sidewalls below 3.5 feet No round water see a e observed � 0 a N , ai H 0 (� � N � 0 J W U � a [7 N Q � c'1 O �N X a � w U Icicle Creek Engineers - i Langley Ridge Renlon, WA 2005 KCSWDM Proposed irnpervious Main access road Area= 58,906 sf 1.35 acres Pond access road Area= 21,479 sf 0.49 acres Existin houses to remain Area = 34,496 sf 0.79 acres Area= 33,783 sf 0.78 acres Ponds Area = 25,105 sf 0.58 acres Pro osed lot area Designation Total lot area 2 110,488 sf 11 129,841 sf 3 89,794 sf 4 63,990 sf TOTAL 394,113 sf 35%allowable impervious per lot 137,940 sf , 3.17 acres � Total impervious = 7.16 acres Proposed pervious Till forest 50%of lot to reamin undisturbed 197,057 sf 4.52 acres Till lawn Landscaping for homes 15%allowable landscaping 59,117 sf Pond Area 26,348 sf Landscaping for existing homes 40,559 sf 77,342 sf 203,366 sf Total outwash lawn = 4.67 acres Detention 10/11/2006 __ __ � - - ----_ I `' -- --_- - I-� ' _'_-- - ---� '�� '� - __ � _--- - ! --—-- ��--� ____—�� � , -—�:.,�.,�'-- i- ' _ ��� -_ _- � i � 'V�— �; ' " --- - � ___ i� �1 i . �Py 5✓AG� � � t� , ; Sp � � ( � �c� � -- - - ._— - _—_ _ _ ._ �, , _ \ � � ,.._. a��=_..: � I �� ; t �� � ���� . . ' `' �� l�� ���: � , , „ _ _ - - ; , - -_. - � '���� , �� . `, _ _ _ , - _ � __ � , .� �.�,`�� , *�. ` - - �, , - _���_ .�. _ - -- ,s - - - ; . � � -c �-'� ` ' ' . 1 3 �� .��� l . � �i `�\,4 Y'� \ '\ �\ ����.�� '-- j � 3�°'33 . f� " � � -t - �.� � � �� \ ��`,\```���' f i'� `� ;6 - t� _ � �` ��L��'� � 1-t ' , , �-�_, 1 -,���._ =� `33,783 Sq. ft. - ; ., �--r , � \�����`=—ye%�a�" --� �. � - '- - �\ t`��-=",�,.� ��`, -V . acres _ j � o�s _ ,- ,�;�✓��y �- ,i -�_ \\;�..��� ---.__ , .. _ - .. '' �` 5 .y� �.:%_�-��� --.__�. 1---,, ; ``-�L•�- _���:� =._ 111,12�5 sq ft } ` � . ��;� 2.55 Qctes r - ��-� �—._��- \�� f,� �a --�'/� 13 � _ �" �, � l � __ 51�45� sq:r��ft,�� , �\'�'�,�',.�.-��:----� ;,,�- --_ ___ 1:18 acres��; _ 7 f, `; � � , � • �- , � ft i �;�. . ,�- �-- � : - ," ' - ,,,.----/�: �.:-- - �� , �� ;_ � 1 479 sq. . , J ,r-----�-��- _ _._ �.`\�.�.�„�_� �� �-__ 1� � 2 0.49 acres �: �� ;����1�- _. ,r--�- :�._ ____-.. ��� ;. _ _. � ;��----� ._�`��"��� 25,105 sq. fit.= - -_, .�_ � ��-�;--�`��.___-'�-�, : �----�__._�\' ���,�, � � ' �,i�-"�i� � �------._�- - �., -- _ __ -���� �� _ _ 0,58 itcres -=- _---_ � � -- -- _ - _ -�- �. _ ' ___ -- -� - -_ � 2„p - `- F `_._�-..-� '��.�1?i�� --�y`"�-�..�� �.y�_ '„� - .._ ... , . . _ .. __ ___- ! ....,i �� . �' � '. ''�. . _ __ ' ,* .` . .. � �. '_ --....-�-`� � .` .� � �. .. A.-_ , ..__ . . .. � �-..-' � �,\ ,. ; > _ � � ��-� _ - - , __ �.� % - 12 �_�-�-� �`\\� ,-ti.\� i�`---- -,_=--� �,=- ��'� � �.r__�"�-�' _ - _ -_ _ __ _ _ - -z2s+� � ` . � - . �1 _ __ � -- , , � . . -..< __ -`. • �-��` ��� 73,055 sq. ft _._; - ,� `\� �;�� ,`��� � , � -� ����,;, � - . � -.- �.� \���..� - . , . �-. - _ . . ��� � - �__ � � .�! !l . .,._ 1.68 acres � ,�,� \ ' J 6�` ;� 1,a�' � � �._ - � � �,_r._ ,.; __ . � _ ` ' t _ '�; _- �. _ ,\, ��\ a �`��`�\�� ��"` 4 , ��l � '� L. .. \ Sq � � __ _ � i��`�* z ;`� �� 63,�90 . ---- �``� _ - - . �� � _ ; : , � - �.�.� .`�.�� �` ��o � � _.. 1. adres �.., ,. - r>, ; ����\ . . � 4� -- - � . � � , ae � ,� ,. � - ^---�-�.j�, _. ; � f i : �'�\\\�'��\'�,�a�,� �`��,�\'"4�5�`�. - _ ' __ � t'I._ �rs--z" �, I .- t�� ����� `\�� �\• \�`' t �� : ; � � �- �._ i �-���1 I---- V �6��'`��\��\\� �\�\`.`�\���\�_ _'�. ��r -- �� � �. , . � , ., '' . �\` `` :�-.�_-._� , . --. ,..�,r. `� ,...��` ; � __. � , ��., ��,, `-r _ � Z ` _•. , � �. ° "+z_ � ,, � - 1.1 -- - - - �, \ �. . �_ '.. t� ! . 129,841 sq.f,tt. 8 ' \ `� ' n� � J`'.�i> = 2.98 acres g 32;496 sq. ft. .. � _ ,, , - ` 0:75 ,acres . ,, 2.60 q.`ft. � : 0.06 cres . { - �.`-�`',`�l'-1 , _ :�_ . ,. ,� . �8,906 sq.b . „ , - M a, o . _ � cres �� . ,� ,.�.~ ' 3 o -:-s_.. ,_ , ._-89,794 sq. .ft: _ - ,..�, ._ . � _. 2.06'' acres �� i •�� `r �- _��� � � 2 � _ � , . r _- " i - �. � ti3\,� '� � `; � r:�� ��,`, '_'110,488��sq. ft. � '.�' ',; _ � � . _ . ,. ._ , , ,. _ � � -.,. � � � 2.54 acres , ": `., ( - , f Y � f_.V'. i�. , : i . . 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I -_.� r Are a-_... ----; ? � � Tiil Forest� 16.35 acres; � �i Till Pasturel 0.00 acresi II �� Till Grass 0.00 acres; i Outwash Forest� U.00 acresj ii +. ; ; � Outwash Pasture; Q-00 acresi � � Outwash Grass; 0.00 acres; � � ; i Wetlandl D.00 acres' i Impervious� O.OU acres' ;j r Total-- � I i � ; 16.35 acres; ij Scale Factor : 1.00 Hourly Reduced Time Series: prede+� » '� �� Compute Time Series � �,' Modiiy User Input � i' — �a File for camputed Time Series [.TSF] +� ' predev Flow Frequency Analysis Time Series File:predev.tsf Project Location:5ea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 1.03 2 2/09/O1 18:00 1.32 1 100.00 0.990 0.280 7 1/06/02 3:00 1.03 2 25.00 0.960 0.764 4 2/28/03 3:00 0.792 3 10.00 0.900 0.027 8 3/24/04 20:00 0.764 4 5.00 0.800 0.454 6 1/05/05 8:00 0.668 5 3.00 0.667 0.792 3 1/18/06 21:00 0.454 6 2.00 0. 500 0.668 5 11/24/06 4:00 0.280 7 1.30 0.231 1.32 1 1/09/08 9:00 0.027 8 1.10 0.091 Computed Peaks 1.22 50.00 0.980 Page 1 �f COHV V,��J{Y�611Q . �. _. .� 7 ��) �Area— --; � ' � ,i Till Forest� 4.52 acres� '' � Till Pasturel �.00 acres� I, li ! Till Grass' 4•6� acres� Ouiwash Forest 0.00 acresj � � � i Ouiwash Pasture� 0.00 acres; Outwash Grassl 0.00 acres � Wetland� 0.00 acres� � � i !m ervi 7.16 acres� P ous � 1 � �Totai � ; ; 16.35 acres� , � Scale Factor : 1.00 Hourly Reduced ;; i; Time Series: dev{ » I Compute Time Series ; Modiiy User Input � � File for computed Time Series [.TSF] � � i ; � �� dev Flow Frequency Analysis Time series File:dev.tsf Project Location:5ea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow ttate Rank Time of Peak - - Peaks - - ttank Return Prob (CFS) (CFS) Period 2.33 5 2/09/O1 2:00 4.70 1 100.00 0.990 1.82 8 1/OS/02 16:00 2.77 2 25.00 0.960 2.77 2 2/27/03 7:00 2.72 3 10.00 0.900 1.87 7 8/26/04 2:00 2.48 4 5.00 0.800 2.26 6 10/28/04 16:00 2.33 5 3.00 0.667 2.48 4 1/18/06 16:00 2.26 6 2.00 0. 500 2.72 3 10/26/06 0:00 1.87 7 1.30 0.231 4.70 1 1/09/08 6:00 1.82 8 1.10 0.091 Computed Peaks 4.05 50.00 0.980 ,_ i .�=� _-� . �,��` . ( �.` � .: . (� � �:. '�� ' �F ��.:� - .. . . . � � . . . 'e�_ . � .. - . Page 1 l _-���,�--_ \ �`�t'�,,,�;------ ---- -_\ —t��'�—_ --� /�— \ i � \ / � � \ / �� \_ �� `-0��— � � � ��`,. �. I � �\ � B�F� � \ `-� __, 6 g£� �\ � \ � �� � �� �' I � �� �����\`\\ � I � ` 8c'f, \\` �'� � \ �` 9�� \ \ . I� NN `� \ � ��� � � \� o a, � � � I ��`�N� /�� ��,` \�\,\ • �� � � � 1�'�� / / _\ �`�...__ �\ � � � �,'� ���� \.� \ � � I / / � — � / / � � � � � � � � ut I ���� � � � � � � , �� N � / / �� .��'�� /� / / �� `�� � ���� � // I � / q� ,�,C" c�, � � � ���� �'�' ti�"/cN I � � ��� � / / / / �. � � '-� / / / �_ � ' -- - = � `� � I � � /�/ °)�/ ___ �� �v ( --_- � ,� ;� ---- ___ - - , __ _ _ _ _ 9Z�'-� � Langley Ridge Pond Volume Calcs (for input to KCRTS single outflow table) Infiltration rate= 3 min/inch 0.000462963 ft/sec Total Incremental Stage Discharge Volume Area Volume (ft) (cfs) (c� (s� (c fl 0 1.90 0 4,106 0 2 1.90 10,238 6,132 10,238 4 1.90 24,885 8,515 14,647 6 1.90 44,571 11,171 19,686 �,II i � � infil-pond.rsl j One Outlet Reservoir Routing File Sta e Dischar e Stora e Perm-Area (Ft� (CFS� (Cu-Ft� (Sq-Ft) 0.00 0.000 0. 4106. 2.00 0.000 10238. 6132. 4.00 0.000 14647. 8515. 6.00 0.000 19686. 11171. 0.00 Ft : Base Reservoir Elevation 3.0 Minutes/Inch: Average Perm-Rate I� I Page 1 infil-pond-out Flow Frequency Analysis Time series File:infil-pon-out.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.000 5 2/09/O1 4:00 0.000 4.14 1 100.00 0.990 0.000 7 10/O1/O1 0:00 0.000 0.61 2 25.00 0.960 0.000 2 2/27/03 9:00 0.000 0.49 3 10.00 0.900 0.000 8 10/O1/03 0:00 0.000 0.43 4 5.00 0.800 0.000 6 10/28/04 17:00 0.000 0.31 5 3.00 0.667 0.000 3 1/18/06 17:00 0.000 0.22 6 2.00 0.500 0.000 4 10/26/06 1:00 0.000 0.00 7 1.30 0.231 0.000 1 1/09/08 9:00 0.000 0.00 8 1.10 0.091 Computed Peaks 0.000 4.00 50.00 0.980 Page 1 October 11,2006 WATER QUALITY CALCULATIONS LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report WETPOND DESIGN Project Name: Langley Ridge By: wph Project Number: 107-012-05 Date: 3/17/2006 DRAINAGE CRITERIA: Ciry of Renton-King County Standards RAINFALL METHOD: King County Runoff Time Series(KCRTS) METHOD OF ANALYSIS: {Section 6.4.1.1 KCSWDM) Step 1) Determine volume factor f. f = 3 Basic:f=3, Large:f=4.5 Step 21 Determine rainfall R for mean annual storm R= 0.039 ft See Figure 6.4.1.A Step 31 Calculate runoff from mean annual storm Vr=(0.9Ai +0.25Atg +0.10 Atf+0.01 Aog)'R Ai = Area of impervious surface 286,625 sf 6.58 acres Atg = Area of till grass 176,854 sf 4.06 acres AtF= Area of till forest 196,891 sf 4.52 acres Aog = Area of outwash grass 0 sf R= Rainfall from mean annual storm 0.039 ft From Step 2 Vr= Vol. runoff from mean annual storm 12553 cf Step 4)Calculate wetpool volume Vb= f Vr f= Volume factor 3 From Step � Vr= Vol. runoff from mean annual storm 12553 cf From Step 3 Vb= Volume of wetpool 37658 cf Step 51 Determine wetpool dimensions a) Determine geometry of first cell �� Volume in first cell 1 1297 cf 25-35%of total vol.,try 30% Depth h(1 st cell,excl.sed. storage) 6.0 ft 3 to 6 feet Required surface area 1883 sf Provided 1st cell dimensions: width 42 ft length 50 ft Provided 1 st cell surface area 2100 sf Aprov'd>Areq'd b) Determine geometry of second cell Volume in second cell 26361 cf 65-75%of total vol.,try 70% Depth h(2nd cell, excl. sed.storage) 6.0 ft 3 to 6 feet Required surface area 4393 sf Provided 2nd cell dimensions: width 40 ft length 73 ft Provided 2nd cell surface area 2920 sf Aprov'd>Areq'd c) Length to width ratio 3.08 :1 Must exceed 3:1 WATER QUALITY POND VOLUME WQ volume= 37,658 cf � 120 ft I 84 ft Area= 78 ft 42 t 3,528 sf Area= 9,360 sf I Volume= 38,664 cf i � October 11,2006 CONVEYANCE CALCULATIONS � � , ., , . -� � _� I�, � . � i i , � � ' ; LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report ` _ '\ �-.�cAUEr �f�' �t��� i����YA�� ���5 � � � � ; So � � --� — ���G��4PGF. i I �- � �=' � � aP�- : / � / ' � i �� ��r�:`''c,p': - � � C3}� ` � ' � ' � �� - -, � � �t� � I ����� � � , , i � _ �� �, � ,- , ; - - - - ' /' ' ( � \ { \y , � � �'r � �� t � I �� i- ; i � s %` _ ' � o a� sq. n. � I ...��'/~/ e � O�C}f.G9 . ___...�_.'_"'._— . ��' � f � �j'�' Ff� 6��� - 1 i I � �. 4,.,» �. f�. ��_ i i ` : � .�J k ! ' � 0.95 acres � \ ---� _. o � � � 4 ' �"- � ! : .-- . . `, I -, ' ' I I ; "f� * 'S �\ ��,\ �' T -- , — ---- —_ _ � ` f ` � � , `, ;F4� ; ; � ; � _ \ � i f . � ,,� � 38.321�sq. ft. ( � � � � , � � 5.562 sq. ft. + 0.88 acres i ` .� � ''�� ;:n�' ' " � 0.13 acres ( - � •1 � : � i , ' -. .` �jfy.� � ,� �� fi 7 �\ v�� �- 12.927 eq. ft. � � 14 7 3�' __ 0.30 ocres \ '10,314;s�. H. 13,361 . ft. — _. � . � Q $Q ' -- '�b � � — �__. --- � , -- —_z— - , ,N« ___ — `� C3�°► ' --- _,a — -- _-- — — — -- 0 r . res - -----� - --�ZfT. ___— � , _ —__-- -'---- �. �s.t y� : : - � -� _':� -„ � ' - -- � ------- 18.742 sq. ft. ._—` - ---- - - --'- � - -�- .� -. :._.1B__ _;_-- •..s. �� . __—__ _ ....�.._ ._..__— ._.__- �'1 ! 24 pc a.� 0 31 ac , i �1 ' � -' . 9.057 sq. ft. � — - ... ____.'_ _.. - ----•u - -=`- ._ �: . Z i ; ; - - --— �]�y. � i i,� � '°'� - �,Y_ 1 1,086 eq. ft. _ �-- - 6;5 sq. ft. � �� C V R' � . � 3 � � `-D�� a ! ,4 ; '` � � 10.203 sq. ft. �� 8 ��9.��� t. , ' 29.453 sq. ft. � p rt �� � � g ( � g - .� -_ . r� � 0.2J acres �� � 1 0.6Q acres '. l.l> >s,iss �q. n. CB� . � = C�� {��8 '' � i -- � - o.3s a«�s �o.oa�,gq. rt. i� �LL � � L �.`-� I' 0.23'xree ' � 14,971 sq. tt. I �t 4 ClJ K I� � � I � ' i .- J € ... - ` \_ � ;t 0.34 acres i � .r � ,� . 1 D :, ' ,-��,. , u �:� il I ' � `" ' � - '� :' � I l . 35-:sq.: � ._ ( � � �. �.. � ,,� ' I : .. �11'ocr' ' ! a: � � i ! � � � .. . I � i i Langleyridge Storm Water Conveyance Calculations Catch basin tributary areas Area Impervious Pervious Receiving Designation Area Area catch basin acres (acres 1 0.065 0.065 CB#8 2 0.440 0.440 CB#7 3 0.190 0.000 CB#8 4 0.340 0.340 CB#7 5 0.185 0.185 CB#7 6 0.475 0.475 CB #5 7 0.150 0.150 CB#6 8 0.175 0.175 CB#6 9 0.115 0.115 CB#5 10 0.110 0.000 CB #5 11 0.170 0.170 CB#4 12 0.115 0.115 CB#2 13 0.155 0.155 CB#2 14 0.120 0.120 CB#4 15 0.250 0.000 CB#5 16 0.210 0.000 CB#6 17 0.430 0.000 CB#7 18 0.160 0.000 CB #4 TOTAL 3.855 2.505 Impervious Pervious Receiving Area Area catch basin acres acres) 0.255 0.065 CB#8 1.395 0.965 CB #7 0.535 0.325 CB#6 0.950 0.590 CB#5 0.450 0.290 CB#4 0.270 0.270 CB #2 3.855 2.505 area calcs 10/11/2006 3.2.1 RATIONAL METHOD TABLE 3.2.1.A R[;NOFF COEFFICIEl�TS- "C" !'ALGES FOR THE RATI0IAL h�ETHUD General Land Covers Single Family Residentiai Areas� Land Cover C Land Cover Density C Dense forest 0.10 0.20 DU/GA(1 unit per 5 ac.) 0.17 Light forest 0.15 0.40 DU/GA(1 unit per 2.5 ac.) 02� Pasture 0.20 0.80 DU/GA (1 unit per 1.25 ac.) 0.27 Lawns 0.25 1.00 DU/GA 0.30 Playgrounds 0.30 1.50 DU/GA 0.33 Gravel areas 0.80 2.00 DU/GA 0.36 Pavement and roofs 0.90 2.50 DU/GA 0.39 Open water(pond, lakes, 1.00 3.00 DU1GA 0.42 wetlands) 3.50 DU/GA 0.45 4.00 DU/GA 0.48 4.50 DU/GA 0.51 5.00 DU/GA 0.54 5.50 DU/GA 0.57 6.00 DU/GA 0.60 � Based on average 2,500 square feet per lot of impervious coverage. For combinations of land covers listed above, an area-weighted "C�:x A," sum should be computed based on the equation C�: x A,_ (Cr x A,)+ (C2 x AZ)+ ...+(C�x A„),where AB= (Ar+AZ+ ,,,+A„), the total drainage basin area. TABLE 3.2.1.B COEFFICIENTS FOR TFiE RaT10NAL ?4iETHOD "ik" EQUA'TION Design Storm Return Frequency aR bR 2 years 1.58 0.58 5 years 2.33 0.63 10 years 2.44 0.64 25 years 2.66 0.65 50 years 2.75 0.65 100 years 2.61 0.63 �� TABLE 3.2.1.0 kR VALUES FOR T,USING THE RATtOnAL METHOD �`� Land Cover Category kR Forest with heavy ground litter and meadow 2.5 Fallow or minimum tillage cultivation 4.7 Short grass pasture and lawns 7.0 Nearly bare ground 10.1 Grassed waterway 15.0 Paved area (sheet flow)and shallow gutter flow 20.0 200� Surface�'ater Design�ianual ]/24/2005 3-13 \ �__\ I � � Scenario: Base � `°'� ! � � � � � '� � �. , i :�,� � ; �� � ' , � � i � � � i I i — - � . i ! ' , � ' ' � ��G�P� i i I se o�`� I � I. � OUTLET j i ' ! ��` CB#1A !�— i j � � Q� � � i i A� ' I I � 3 i E i i " /-- i � � / —�. P�SecE i I � 1 � / I 1 -.. '��NSQP � �'��CB#�J � :i : , . /� ' o`- I � � I I �°SQ�.�� /i I ' i i s + I j � � i` -- I ��� � I i j " � � ,� I i j � i � � I I f ; �—__, N i � � i i ! j � � ` a ; ; , , ,-, : , - i i -� , -, i i —� f i :� " -- .�, � i I i� — —. ' v: j j i � � — -- ; j � ; �- j � ; i ! n i � ,. I ! i I � ` i - � \` \� � � �, � B#2 ; ; j I - ., � ��� _ ' I >�--- ' �� � I ` ' � _i I ' � ,, _ __. : � C B#9 ; I P- - -- -_ - -- --- _ - _-\-�= _� j �'` - ' •------ - - - ___ -- -_ � � �'-. - -- _ _ ,. ,, _ - _ ____..._ � ,�: _� . : --__�_-- - _ ---- - ----=_ - , ., : _ -- - - - - � � i , f __ � _ ��_Q__ � I �. ., � ' � (QB#7 � -- I_=—��- j .�� j - CB#3 j � � ' C�#4 CB#10 ' � I � I �� i " i „ i _ i " � � `; � i I I .. _ I � i ' , I i j ? -. :; i ' -- --------- � ; �i ! i i - -------- � i i i i i Title: Langleyridge Project Engineer:Site Development Associates r:1...\calcslstormcad\Iangieyridge.stm StormCAD v5.6[05.G6.012.00] 10/11/06 11:01:12 AM O Bentley Systems, Inc. Haestad h9ethods Solution Center Watertown,CT 06795 USA +�-Z03-755-1666 Page 1 of 1 Scenario: Base SDA INLET Label Rim Area Inlet Inlet Time dditiona Rim Hydraulic Elevation(acres) C CA of Flow Elevation Grade , (ft) (acres oncentratio (cfs) (ft) Line Out (min) (ft) CB#4 387.79 0.74 0.65 0.48 5.00 0.00 387.79 386.38 CB#5 400.23 1.54 0.65 1.00 5.00 0.00 400.23 397.86 CB#6 421.15 0.86 0.65 0.56 5.00 0.00 421.15 409.32 CB#7 421.11 2.36 0.63 1.50 5.00 0.00 421.11 412.41 CB#2 371.70 0.54 0.57 0.31 5.00 0.00 371.70 369.49 CB#3 384.51 0.00 0.00 0.00 0.00 0.00 384.51 382.30 CB#8 457.22 0.32 0.77 0.25 5.00 0.00 457.22 453.56 CB#9 458.51 0.00 0.00 0.00 0.00 0.00 458.51 453.56 CB#1 457.33 0.00 0.00 0.00 0.00 0.00 457.33 453.98 Title: Langleyridge Project Engineer.Site Development Associates r.\...\calcs\stonrcad\langleyridge.stm StormCAD v5.6[05.06.012.00] 10/11/06 11:02:48 AM c�Bentley Systems, Inc. Haestad Methods Solution Center WateRown,CT 06795 USA +1-203-755-1666 Page 1 of 1 Scenario: Base SDA PIPE Upstrea ownstrea pstrea ownstrea Length onstructe Section Manning Total Full Node Node Invert Invert (ft) Slope Size n System Capaciry Elevation Elevation (fUft) Flow (cfs) (ft) (ft) (cfs) CB#1 CB#1A 330.84 327.79 169.00 0.018047 18 inch 0.012 10.22 15.29 CB#3 CB#2 381.31 368.50 128.00 0.100078 12 inch 0.012 9.56 12.21 CB#5 CB#4 396.87 384.43 144.00 0.086389 12 inch 0.012 8.43 11.34 CB#4 CB#3 384.43 381.31 66.00 0.047273 12 inch 0.012 9.59 8.39 CB#7 CB#6 409.49 408.37 216.00 0.005185 12 inch 0.012 4.60 2.78 CB#6 CB#5 408.37 396.87 275.00 0.041818 12 inch 0.012 5.96 7.89 CB#2 CB#1 368.50 331.34 250.00 0.148646 12 inch 0.012 10.30 14.88 CB#1A OUTLET 327.79 326.65 10.00 0.114000 18 inch 0.012 10.11 38.42 CB#9 CB#S 453.36 453.06 58.00 0.005254 12 inch 0.012 0.00 2.80 CB#10 CB#9 453.98 453.36 89.00 0.006964 12 inch 0.012 0.00 3.22 CB#8 CB#7 453.22 409.49 443.00 0.098713 12 inch 0.012 0.67 12.13 Title Langleyridge Project Engineer. Site Development Associates r:\...\calcs\stormcad\langleyridge.stm StormCAD v5.6[05.06.012.00] 10/11/06 11:02:42 AM �Bentley Systems, Inc. Haestad Methods Solution Center Watertown,CT 06795 USA +1-20&755-1666 Page 1 of 1 Rainfall Table Retum Periods Durations 25 year 100 year 5 min 2.70 3.40 15 min 1.80 2.10 30 min 1.00 1.30 60 min 0.60 0.80 Rainfall Intensities are in(in/hr) Title: Langleyridge Project Engineer:Site Development Associates r:\...\calcs\stormcad\langleyridge.stm StormCAD v5.6[05.06.012.00] 10/�1/06 11 03:21 AM O Bentley Systems, Inc. Haestad Methods Solution Center Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 1 Calculation Results Summary --------------------- Scenario: Base »» Info: Subsurface Network Rooted by: OUTLET »» Info: Subsurface Analysis iterations: 3 »» Info: Convergence was achieved. CALCULATION SUMMARY FOR SURFACE NETWORKS � Label I Inlet � Inlet � Total � Total � Capture � Gutter � Gutter � � � Type � � Intercepted � Bypassed � Efficiency � Spread � Depth � � � � Flow � Flow � (�) � (ft) � (ft) � I I I I ccfa) � (cts> I I I I � -------- �--------------- �----------------------�-------------�----------� ------------� --------�-------- � � CB #4 � Generic Inlet � Generic Default 100� � 1.30 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #5 � Generic Inlet � Generic Default 100� � 2.73 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #6 � Generic Inlet � Generic Default 100� � 1.53 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #7 � Generic Inlet � Generic Default 100� � 4.07 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #2 � Generic Inlet � Generic Default 100$ � 0.85 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #3 � Generic Inlet � Generic Default 100$ � 0.00 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #8 � Generic Inlet � Generic Default 100� � 0.67 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #9 � Generic Inlet � Generic Default 1008 ( 0.00 � 0.00 � 100.0 � 0.00 � 0.00 � � CB #10 � Generic Inlet � Generic Default 100� � 0.00 � 0.00 � 100.0 � 0.00 � 0.00 � - - -- ----------------------------------------------------------------------------------------- CALCULATION SUMMARY FOR SUB;UHFACE NETWORK WITH ROOT: OUTLET � Label � Number � Section � Section � Length I Total � Average I Hydraulic I HydrauliC � � � of � Size � Shape � (ft) � System � Velocity � Grade � Grade � � � Sections � � � � Flow � (ft/s) � Upstream � Downstream � � � � � ( � (cfs) � � (ft) � (ft) � I -------�---------- �---------�----------�--------�--------�----------�-----------�------------� � P-14 � 1 � 18 inch � Circular � 10.00 � 10.11 � 18.33 � 329.01 � 327.39 � � P-13 � 1 � 18 inch � Circular � 169.00 � 10.22 � 9.27 � 332.07 � 328.69 � � P-12 � 1 � 12 inch � Circular � 250.00 � 10.30 � 20.45 � 369.49 � 331.95 � � P-il � 1 � 12 inch � Circular � 128.00 � 9.56 � 17.20 � 382.30 � 369.49 � � P-10 � 1 � 12 inch � Circular � 66.00 � 9.59 � 12.21 � 386.38 � 382.30 � � P-7 � 1 � 12 inch � Circular � 144.00 � 8.43 � 15.82 � 397.86 � 386.38 � � P-6 � 1 � 12 inch � Circular � 275.00 � 5.96 � 11.04 � 409.32 � 397.86 � � P-5 � 1 � 12 inch � CirCular � 216.00 � 4.60 � 5.86 � 412.41 � 409.32 � � P-3 � 1 � 12 inch � Circular � 443.00 � 0.67 � 8.28 � 453.56 � 412.41 � � P-2 � 1 � 12 inch � Circular � 58.00 � 0.00 � 0.00 � 453.56 � 453.56 � � P-1 � 1 � 12 inch � Circular � 89.00 � 0.00 � 0.00 � 453.98 � 453.56 � Title:Langleyridge Project Engineer:Site Development AssoCiates r:\...\calcs\stormcad\langleyridge.stm StormCAD v5.6[05.06.012.00J 10/11/06 11:02:30 AM O Bentley Systems, Inc. Haestad Methods Solution Center Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Calculation Results Summary � Label � Total � Ground � Hydraulic � Hydraulic � � � � System � Elevation � Grade � Grade � � I Flow I (ft) � Line In � Line Out � � � (cfs) � � (ft) � (ft) � � -------- �--------� -----------� -----------�-----------� � OUTLET I 10.11 � 330.12 � 326.00 � 326.00 I � CB #lA � 10.11 � 331.16 � 329.01 � 329.01 � � CB #1 � 10.22 � 334.15 � 332.07 � 332.07 � � CB #2 � 10.30 � 371.70 � 369.49 � 369.49 � � CB #3 � 9.56 � 384.51 � 382.30 � 382.30 � � CB #4 � 9.59 � 387.79 � 386.36 � 386.38 � � CB #5 � 8.43 � 400.23 � 397.86 � 397.86 � � CB #6 � 5.96 � 421.15 � 409.32 � 409.32 � � CB #7 � 4.60 I 421.11 � 412.41 I 412.41 I � CB #8 � 0.67 � 457.22 � 453.56 � 453.56 � � CB #9 � 0.00 � 458.51 � 453.56 � 453.56 � � CB #10 � 0.00 I 457.33 � 453.98 � 453.98 � . Compler_ed: 10/11/2006 11:01:31 F�M Title: Langieyridge Project Engineer:Site Development Associates r:\...\calcs\stormcad\langleyridge.stm StormCAD v5.6[05.06.012.00] 10/11/06 1 1:02:30 AM O E3entley Systems, Inc. Haestad Methods Solution Center Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Profile Scenario: Base LANGLEYRIDGE 25 YEAR STORM cB#s Rim:458.51 ft CB�$ CB#10 �E IN:453.36 ft Rim:457.22 ft Rim:457.33 ft �E OUT:453.36 ft IE IN:453.06 ft IE OUT:453.22 ft IE OUT:453.98 ft _ _ _ ______ _ ------ . ,___ _-_ _�_ _ ---- _-- , _ _ __ ,- - , _ _ _- -_ __ 460.00 _. _ - - -_: . __- ' -- - _ -- -�- ' - - -- - - -- ---- --- 55.00 4 L:89.00 ft- --......_.: _.:_.- '. ' -' : _ ` _ __-- --- 50.00 4 Size: 12 inch ; S:0.00696q ft/�_ L:58.00 ft ' ! ; ' _ 5.00 �ize:-��-fi�-�- __ -- ; � 44 S:O.OU5254 fVft ---_=-----__- _ ; ; ; - 0.00 44 �. { !_ ,__ --= -- __ __- __ 35 0a , -- . . _ ,., ; _ - 3 ' , 4 � i- �. � i ` ---T --�.'-O?io. =-- _�CByi7- -T-- --�-�-- --- 30 00 - � 4 . ; ; •O•y"O '' Rim:421 '11 ft : --..-.- : �-98�`'.;y�F - -- I E I N: _409 49 ft_ _ -__ -- - - - - - 425.00 ! j�,o,� IE OUT:409.49 ft . Cg� ' ' �__..�� ;__ -- ---- � - Rim:421.15 ft; - - �, 420.00 --IETF7:408�Tii `lE�UT:408.37 ft ' ' ` --- ; '--- - ''._ _ _- �-=--- -' 15.00 __ ` ` ' ' ` _ 4 - - - - 410.00 ; ; � L:216'00 ft ' - --Size;�2 incF�-- - --_ - -- ---- 405.00 ' S 0.005185 fVft �2�S � � Rm.�40-0.23 ft ' ' - --- _- - - S.Si�.' .�, I E I N:396.87 ft _ -- - 400.00 ; ; ` 6Q4772��� �. IE OUT:396.87 ft ; ; 78 - • - --- _- -- -_ G�-#d---.. _ - - 395.00 ' � Rim 387.79 ft : S.S;��r I E I t�( 384.43 ft; -- 390.00 Elevation(ft) ' - -- �0 - . $d.d ` -�O�e. �E OOT•3 ` ; ' ! 6'�'2.o_�O�' �C_B#3 - -- € ;_ ; - -- -- - - 85.00 ��6 i `���h im;-38d3i-if'' , 3 �if, IE IN:381.31 ft ', - -- ---IEQLiT:-38'1_31--fi- - 380.00 ; ; ; -�OO- : S.�e . � ---� =-- ' -- - -- _ --���j�h -- - --- - 375.00 3�h � �S�£ ` ' �h��`'m��'8 - � � ; __ - _--- - - _- 70.00 Ri�n:371.70 h . IE.1I�I:368_5Q ft- . 3 ; ' ` p�o��04� UT 36 0 ft ' ' _ ! ___ _ �- - ` --=---- ' - - -- - - 65 00 �� IEO 85 �� 3 . - ' --------- � --- ' ' �_.--- � -- ----- -- 60.00 -- --- 3 , ..--- -- --- -- 55.00 -- 3 __ - __ -- - 50.00 ; ; s s� �o;�s� ; s ` , ' --_ _ A��r���F _.._--- --- - -- -- - ----- -- -- _ -- - 5.00 ' ', ; ; , __ - opp ; �� CB#1 � _._ ,_ _ _ , _:_ _ _.....- - -` -- - ---_ _------ ; ; ; � ! i � ; , ; ` T. im:334. �B�}� � Rim:3�3t.�T6 ft ' _._..---T-_ :- -----+------_...._- ----..___ ;----- ' - ` -- -- --- . -- - ; ; IE OU33330. ----_. , ; ftIE ry:327J9 _____ -:--._ IE OLA3�B0.79 ft --- � -�---- �.-. ' ` ; - -- -- - , 30.0 __`_ _ _ s ; i ; ' - - - - ' 3 0 OUTLET --- ` ` ' � --- - - - 25 00 im.330.12 ft ; - 88�Och s cS�.. . l:� R• . 5 p0 3 ; �4�� p��� ' __.... _ _ ' _ _- _ - - �s�a 320.00 _ __--.- _ _ -- - _ ---__ . _. _ _.. _ O+pp 1+00 .2+p0 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+pp 12+00 13+00 14+00 15+00 16+00 17+00 18+00 ppo�00 0 0� � � Station(ft) Title: Langleyridge Project Engi�eer:Site Development Associates r�._\calcs\stormcadllangleyridge.stm StormCAD v5.6[05.06.012.00] 10r11/06 11:09:23 AM O Bentley Systems. Inc. Haestad Methods Solution Center Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 1 October 11,2006 APPENDIX D - MAINTENANCE AND OPERATIONS MANUAL LANGLEYRIDGE SUBDIVISION Final Storm Drainage Report October 11,2006 Operation & Maintenance Manual N0. 1 -INFILTRATION Maintenance Defect Conditions When Maintenance Results Expected When Component Is Needed Maintenance is Performed General Trash&Debris See"Ponds"Standard No. 1 See"Ponds"Standard No. 1 Poisonous Vegetation See"Ponds"Standard No. 1 See"Ponds"Standard No. 1 Poilutio� See"Ponds"Standard No. 1 See"Ponds"Standard No. 1 Unmowed Grass/ See"Ponds"Standard No. 1 See"Ponds"Standard No. ' Ground Cover Rodent Hoies See"Ponds"Standard No. 1 See"Ponds"Standard No. 1 Insects See"Ponds"Standard No. 1 See"Ponds"Standard No. ? Storage Area Sediment A percolation test pit or test of facility indicates Sediment is removed and/or facility facility is oniy working at 9�°!0 of its designed is cleaned so that infiltration system capabilities. if two inches or more sediment is works according to design. present,remove. Sheet Cover(if Sheet cover is visible and has more that three Sheet cover repaired or replaced. Applicable) 114-inch hales in it. Surnp Fiiled with Any sediment and debris filling vauit to 10%of Clean out sump to design depth. Sediment and Debris depth from sump bottom to bottom of outlet pipe (If Applicable) or obstructing flow into the connector pipe. Filter Bags Filled with Sediment Sediment and debris fill bag more than 1/2 fuli. Repiace filter bag or redesign and Debris system. Rock Fiiters Sediment and Debris By visuai inspection.little or no water flows Replace gravei in rock filter. through filter during heavy rain storms. Side Slopes of Pond Erosion See"Ponds"Standard No. � See"Ponds"Stan�ard No. 1 Emergency Rock Missing See"Ponds"Standard No. ? Overfiow Spiliway Settling Ponds 2nd Sediment Remove�vh:en 6"or more. Vaults Note: Sediment accumulation of more 2han.25 rnches per year rnay indicate excessfve erosion is occurnng upstream of fhe facilrty or that conveyance syste�»s are not being properiy maintained. The contributing drainage area silould be checked(or erosion problems or i�iadequate maintenance of conveyance systems if excessive sedimentation is noted in an infrltration tacitify. Check twice a year during firsf 2 years of operation;once a year thereaffe�. Clean manho/es/catch basins, repair damaged irrlets/outlets,clean trash racks. LANGLEYRIDGE SUBDIVISION D.1 Final Storm Drainage Report October 11,2006 NO. 2 -CONTROL STRUCTURElFLOW RESTRICTOR Maintenance Defect Condition When Maintenance is Needed Resuits Expected When Component Maintenance is Performed Generai Trash and Debris Distance between debris build-up and bottom of RII trash and debris removed. (Includes Sediment) orifice piate is less than 1-1!2 feet. Structural Damage Structure is not securely attached to manhole wali Structure securely attached to and outlet pipe structure should support at least wall and outlet pipe. 1,�00 Ibs of up or down pressure. Structure is not in upright position(allow up to Structure in correct position. 10%from p�umb). Connections to outlei pipe are noi watertight and Connections to outtet pipe are show signs of rust. water tight;structure repaired or replaced and works as designed. Any holes--other than designed holes—irt the Structure has no holes other structure. than designed holes. Cieanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and wrorlcs as designed. Gate cannot be moved up and down by one Gate moves up and down easily maintenance person. and is watertight. Chain leading to gate is missing or damaged. Chain is in place and worics as designed. G��'?is rusted ove�5C�°��f its surface area. Gate is repaired or replaced to meet design standards. Ori`:ce 'a;e Dar,c:�;,e� c P::�ss�rg Con;roi device is nci<vor�:ing properly due ro Plate is in place and works as rr�ssinG,��:u±of:la��e. c'�r`.�ent c�ifire plete. de�iened- C�'�;!rt,;<<ens �;��v. �_ _.... r' ��1 r;,r - e::e'a::o�i =1at� 's`_ee �f a�i c`.,s'r�ct����s �;ccking the plate. and works as designed. Over:low Fipe Ol;str„ctiors „ry trash or debris bfocking(or having the Pipe is free of ali obstructions pctentiai of blocking)the overfiow pipe. and works as designed. �vi�n'P,G�E; S�P �,'c7S�d e�CtiOn S}'�tEf"�.'SI?^.E'o'dS ''v��_ 1 588'��OSBd D6t@fltl0(t SySt21T1S� S,andards No. 1 Cat � Bas�o See �� �c-� ��� �', s' S. .��_��r�s ��°Jc � See'Catch Basins'Standards ��0 3 LANGLEYRIDGE SUBDIVISION p 2 Final Storm Drainage Report October 11,2006 N�. 3 -CATCH BASINS Maintenance Defect Conditions When Maintenance is Needed Results Expected When Compo�ent Maintenance is performed Generai Frash&Debris Trash or debris of more than 1/2 cubic foot which is !Vo Trash or debris located {Includes Sediment) iocated immediately in front of the catch basin immediately in front of catch opening or is b(ocking capacity of the basin by basin opening. more than 10% Trash or debris(in the basin)that exceeds 1/3 the No trash or debris in the catch depth from the bottom of basin to invert the lowest basin. pipe into or out of the basin. Trash or debris in any iniet or outlet pipe b#ocking Inlet and outlet pipes free of more than 1/3 of its height. trash or debris. Dead animals or vegetation that could generate No dead animals or vegetation odors that couid cause compiaints or dangerous present within the catch basin. gases(e.g.,methane). Deposits of garbage exceeding 1 cubic foot in No condition present which volume would attract or support the breeding of insects or rodents. Structure Darnage to Comer of frame extends more than 3t4 inch past Frame is even with curb. Frame and/or Top Slab curf�face into the street(If applicable). Top siab has holes larger than 2 square inches or Top slab is free of holes and cracks wider than'l/4 inch(intent is to make sure cracks. ail materiai is running into basin}. Frame not sitting flush on top slab,i.e.,separation Frame is sitting flush on top of more than 314 inch of the frame from the top siab. siab. Cracks in Basin Wails! Cracks wider than 1/2 inch and longer than 3 feet, Basin repiaced or repaired to Bottom any evidence of soil particles entering catch basin design standards. through cracks,or maintenance person judges that structure is unsound. Cracks wider than 1/2 inch and longer than 1 faot No cxacks more than 1/4 inch at the joint of any inlet!outlet pipe or any evidence wide at the joint of inleVoutlet of soii particies entering catch basin through pipe. cracks. SedimenU Basin has se#tied more than 1 inch or has rotated Basin replaced or repaired to Misalig«ment more than 2 inches out of alignment. design standards. LANGLEYRIDGE SUBDIVISION D.3 Final Storm Drainage Report October 11,2006 i I�i NO. 3-CATCH BASINS (ContinuecQ Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is performed Fire Hazard Presence of chemicais such as naturai gas,oii and No flammable chemicals gasoline. present. Vegetation Vegetation growing across and biocking more than No vegetation biocking opening 10%of the basin opening. to basin. Vegetation growing in inleL`outiet pipe joints that is No vegetation or root growth more than six inches tali and less than six inches present. apart. Poilution Nonflammable chemicals of more than i/2 cubic foot No poilution present other than per three feet ofi basin length. surface film. Catch Basin Cover Cover Not in Place Cover is missing or only partially in place.Any open Catch basin cover is closed catch basin requires maintenance. locking Mechanism Mechanism cannot be opened by an maintenance Mechanisrn opens with proper Not Working person with proper tools.Bolts into frame have less toois. tfian 1!2 inch of thread. Cover Difficult to One maintenance person cannot remove lid af#er Cover can be removed by one i Ftemove apptying 80 fbs.of lift;intent is keep cover from maintenance person. sealing off access to maintenance. Ladder Ladder Rungs Ladder is unsafe due to missing rungs.misalignment, Ladder meets design standards Unsafe rust;cracks,ar sharp edges. and allows maintenance person safe access. Metal Grates Grate with opening tivider than 718 inch. Grate opening meets design (If Applicabie) standards. Trash and Debris Trash and debris that is blocicing more than 20%of Grate free of trash and debris. grate surface. Damaged or Grate missing or broken member(s)of the grate. Grate is in place and meets Missing. design standards. NO. 4 DEBRIS BARRIERS (e.g.,Trash Racks) Maintenance Defect Condition When Maintenance is Needed Resuits Expected When Components Maintenance is Performed. General Trash and Debris Trash or debris that is piugging more than 20%of Barrier ciear to receive capacity the openings in the barrier. flow. Metal Damagedt Missing Bars are bent out of shape more than 3 inches. Bars in place with no bends more Bars. than 3/4 inch. Bars 2re missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50°io deterioration Repair or replace barrier to to any pa�t of barrier. design siandards. LANGLEYRIDGE SUBDIVISION D.4 Final Storm Drainage Report � October 11,2006 NO. 5-ENERGY DISSIPATERS Maintenance Defect Conditions When Maintenance is Needed Results Expected When Components Maintenance is Performed. _ Externai: Rock Pad Missing or Moved Only one layer of rock exists above native soil in Replace rocks to design Rock area five square feet or larger,or any exposure of standards. native soil. Dispersion Trench Pipe Plugged with Accumulated sediment that exceeds 20%of the Pipe cieaned/flushed so that it Sediment design depth. matches design. Not Discharging Visuai evidence of water discharging at Trench must be redesigned or Water Properly concentrated points along trench(normai condition rebuilt to standards. is a`sheet flow"of water along trench). Intent is to prevent erosion damage. i Perforations Over 112 of perforations in pipe are plugged with Ciean or replace perforated pipe. Plugged. debris and sed+ment. Water Fiows Out Maintenance person observes water flowing out Facility must be rebuilt or Top of'Distributo�' during any storm less than the design storm or its redesigned to standards. Catch Basin. causing or appears likely to cause damage. Receiving Area Water in receiving area is causing or has poYential No danger of landsiides. Over-Saturated of causing landsiide problems. Internal: � Manhole?Chamber Wom or Damaged Structure dissipating flow deteriorates to 1/2 or Replace structure to design Post. Baffies,Side original size or any concentrated worn spot standards. of Chamber exceeding one square foot which wouid make structure unsound. Qther Defects See"Catch Basins"Standard No.2 See"Catch Basins"Standard No. 3 LANGLEYRIDGE SUBDIVISION D.5 Final Storm Drainage Report October 11,2006 � NO. 6 -FENCING Maintenance Defect Conditions When Maintenance is Needed Results Expected When Components Maintenance is Performed Generai Missing or Broken Any defect i�the fence that permits easy entry Parts in place to provide adequate Parts to a facility. security. Erosion Erosion more than 4 inches high and 12-18 No opening under the fence that inches wide pem�itting an opening under a exceeds 4 inches in height. fence. Wire Fences Damaged Parts Post out of plumb more than 6 inches. Post plumb to within 1-1/2 inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence(inGuding post,top raiis,and Fence is aligned and meets design fabric)more than 1 foot out of design alignment. standards. Missing or Ioose tension wire. Tensioa wire in place and holding fabric. Missing or loose barbed wire that is sagging Barbed wire in place with less than more than 2-1/2 inches between posts. 3/4 inch sag between post. Extension arm missing,broken,or bent out of Extension arm in place with no shape more than i 1r2 inches. bends larger than 3/4 inch. Deteriorated Paint or Part or parts that have a rus6ng or scaling Structurally adequate posts or Protective Coating condition that has affected structural adequacy. parts with a uniform protective coating. Openinqs in Fzbric Openings in fabric are such that an 8-inch- No openings in fabric. diameter ba;i COUIt�flt thrcuUn. NO. 7 - GATES Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed General Damaged or!�.-lissi:�y Missing gate or locking devices. Gates and Locking devices in 5•:';emhe�s place. Broken or missing hinges such that gate cannot Hinges intact and lubed.Gate is be easily opened and closed by a maintenance working freely. person. Gate is out of plumb more than 6 inches and Gate is aligned and vertical. �nore than 1 foot out of desigrl alignment. Missing stretcher bar,stretcher bands,and ties. Stretcher bar, bands and ties in place. ".;:r ".... ._ �ee..Fencind'S`.and?rd��0 5 S�e"Fencina"S`.2r�'ard No.E LANGLEYRIDGE SUBDIVISION D.6 Final Storm Drainage Report October 11,2006 NO. 8 -CONVEYANCE SYSTEMS (Pipes& Ditches) Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed I Pipes Sediment&Debns Accumulated sediment that exceeds 2�4�0 of the Pipe cieaned of all sediment I diameter of the pipe. and debris. Vegetation Vegetation that reduces free movement of water All vegetation removed so water through pipes. flows freely through pipes. Damaged Protective coating is damaged;rust is causing Pipe repaired or replaced. more than 50°io deterioration to any part of pipe. I ` Any dent that decreases the cross section area of Pipe repaired or replaced. pipe by more than 20°/a. Open Ditches Trash&Debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20%of the Ditch Geaned/flushed of all design depth. sediment and debris so that it matches design. I Vegetation Vegetation that reduces free movement of water Water flows freely through through ditches. ditches. Rock Lining Out of Maintenance person can see native soii beneath Replace rocks to design Piace or Missing(If the rack lining. standards. Applicable). Catch Basins See"Catch Basins:Standard No.2 See"Catch Basins'Standard No.3 Debris Barriers See'Debris Barriers"Standard No.3 See"Debris Barriers"Standard I (e.g., Trash Rack) No.4 � NO. 9-GROUNDS (Landscaping) Maintenance Defect Conditions When Maintenance is Needed Results Expected When Component Mainfenance is Performed General Weeds Weeds growing in more than 20%of the(andscaped Weeds present in less than 5% (Nonpoisonous) area(trees and shrubs only). of the landscaped area. Safety Hazard Any presence of poison ivy or other poisonous No poisonous vegetation vegetation. present in landscaped area. Trash or�itter Paper;cans,bottles,totaling more than 1 cubic foot Area clear of litter. �n�thin a landscaped area(trees and shrubs only)of 1.fl00 square feet. Trees and Shrubs Da�naged Limbs ar parts of trees or shrubs that are sp(it or Trees and shnibs with less than broken which affect more lhan 25°!0 of the total 5%of total foliage with split or foliage of tfie tree or shrub. broken limbs. Trees or shrubs that have been blown down or Tree or shrub in place free of knocked over, injury. Trees or shrubs which are not adequately supported Tree or shrub in place and or are leaning over, causing exposure of the roois. adequately supported:re«ove anv dead or diseased trees. LANGLEYRIDGE SUBDIVISION p � Final Storm Drainage Report October 11,2006 NO. 1D-ACCESS ROADSI EASEMENTS Maintenance Defect Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed General Trash and Debns Trash and debns exceeds 1 cubic foot per 1,000 Roadway free of debris which ' square feet i.e.,trash and debris would fiil up could damage 6res. one standards size garbage can. Blocked Roadway Debris which could damage vehide tires(glass Roadway free of debris which or metai). could damage tires. Any obstruction which reduces clearance above Roadway overhead ciear to 14 feet road surface to less than 14 feet. high. Any obstnic[ion restricGng the access to a 1Q to Obstruction removed to allow at 12 foot width for a distance of more than 12 feet least a 12 foot access. or any point restricting access to less than a 10 foot width. Road Surface Settlement,Potholes, When any surface defect exceeds 6 inches in Road surface uniformly smooth Mush Spots,Ruts depth and 6 square feet in area.In general,any with no evidence of settlement, surface defect which hinders or prevents potholes,mush spots,or ruts. maintenance access. Vegetation in Road Weeds growing in the road surface that are Road surface free of weeds taller Surface more than 8 inches tail and less than 6 inches than 2 inches. tall and less than 6 inches apart within a 400- square foof area. Modular Grid Build-up of sediment mildly contaminated with Removal of sediment and disposai Pavement petroleum hydracarbons. in keeping with Heaith Depariment " recommendations for mildiy oontaminated soi�s or catch basir� sediments. Shouiders and Erosion Damage Erosion within 1 foot of the roadway more than 8 Shoulder free af eros:on and Ditches inches wide and 6 inches deep. matching the surrounding road. � Weeds and Brush Weeds and brush exceed 18 inches in height or Weeds and brush cut to 2 inches hinder maintenance access. in height or cleared in such a way as to allow maintenance access. �� zr7. ` ,Nr-..'-' . . �. .�' l ,` LANGLEYRIDGE SUBDIVISION p 8 Final Storm Drainage Report October 11,2006 N0. 11 -WATER QUALITY FACILITIES D.} Wetponds Maintenance Defect or Problem Condition When Maintenance is Recommended Maintenance to Correct Component Needed Problem Wetpond Water level First ceil empty,doesn't hold water. Line the first cell to maintain at least 4 feet of water. Although the second celi may drain,the first celi must remain full to control turbulence of the incoming flow and reduce sediment resuspension. I Vegetation Vegetation such as grass and weeds Vegetation should be mowed to 4 to 5 need to be mowed when it starts to inches in height. Trees and bushes impede aesthetics of pond.Mowing is shouid be removed where they are generally required when height exceeds interfering with pond maintenance 18-inches.Mowed vegetation should be activities:that is,at the inlet,outlet and removed from areas where it could enter near engineered structures. the pond,either when the pond level rises, or by rainfail runoff. Trash and Debris Accumuiation that exceeds 1 CF per Trash and debris removed from pond. 10d0-SF of pond area. InIeU Outlet Pipe InIeU Ouflet pipe dogged with sediment No ciogging or biockage in the inlet and andl or debris material. outlet piping. Sediment Sediment accumulations in pond bottom Removal of sediment from pond bottom. Accumula6on in Pond that exceeds the depth of sediment zone r3ottom plus 6-inches.usually in the first cell. 0il Sheen on Wafer Prevalent and vicibie oil sheen_ Remove oil from water by use of oil- sorbant pads or by vactor truck. Refer probiem to locate source and correct. If chronic low leveis of oii persist,piant 4�etland plants such as Juncus effusus (soft rush)which can uptake small concentrations of oil. �rosor� Erosion of ihe poi�d s side slopes andr"or Slopes should be stabilized by using scouring of the pond bottom,that exceeds proper erosion control measures,and 6-inches,or where continued erosion is repair methods. prevalent. Set���ment o�?ord �ny part of these components that has Dike/berm is repaired to specificaGons. Diker E3erm �ettied 4-inches or lower than the design eievation,or inspector determines dike! �erm is unsound. I �e�r.� t��r 3errr d�v�ding ce'is should be levei Build up low areas of berm or lower high areas so that the berm surface is level and v�ater flows evenly over the entire length ot tf�e berm from the first cell to the second. � .-,.. :�.F�i�;�.t'El�p� POCI�.- r ;��.fl,�' , 501�I E��.pC'S 1 ?f l:;� �gpla�2 f0:'kS 10 Si-BGifIC2fIO�S, �_f��i�P,va�d c, -:':s de s���r�. LANGLEYRIDGE SUBDIVISION p 9 Final Storm Drainage Report Page 1 of 2 Nlichael Dotson - Langley Ridge Comments ,.� ,:<<:, :, . . .. . . ... . . �-3- ,.l�t,-�:i'w .{.t;i-i 3n�.� �„s.,3,3.s, ..i;lF3 �.�#.,x.�e .3Ax..x.},z,r,ar-z'"is'6`�fW�Pv 4�s_r,-:�-'.� From: "Offe Engineers" <darrell.offe�comcast.net> To: "Mike Dotson" <Mdotson@ci.renton.«-a.us> Date: 12/OS/2006 1:50 PM Subject: Langley Rid�e Comments � _ __. _ __ _ _ .. __. ___ _ _ _._._ Mike - in response to your earlier comments - Surface Water: Two minor items; 1. An overflow spillway and route/path will need to be provided in the pond to control where the water goes if I overtopping does occur (design storm exceeded or plugging). The engineer will need to identify the down stream , drainage path for flows that overtop the pond. The pond overflow must discharge in a controlled manner in a � defined channel such as a road or natural drainage swale and not impact downstream properties. We propose I to uti/ize the fire access road(which has been graded to a "v"shape)a//owing any pond overtlow to flow noith towards Tract D. Tract D wi//be an Open Space dedicated as permanent open space, The overflow water wi//then sheet flow across Tract D(continuing north)towards May Creek- p/ease see attached proposed overf/ow roufe.pdf. The grading p/an shows the "v"shape of the fire access road. 2. Per my Comment #1, the engineer will mitigate flow control and water quality for Lot 33; however, I don't see on the plans how the lot runoff is to be direded to the pond. The plans will need to show a runoff collection system from the lot to the infiltration/WQ pond. Also, the drainage report will need to identify this area in the proposed developed impervious and pervious areas table and KCRTS model input so I know it was accounted for in the model. The proposed Lot 33 is an existing deve%ped/ot by the previous property owner (Andrew's). The house and the severa/out bui/dings were constructed in the ear/y 1970's In 2003 a re-mode/was performed on the existing house. This wou/d have been done within King County and work performed and drainage review done under KC review of the re-mode% Neverthe%ss, the property is NOT p�oposed to be re-developed or any furthe�impervious proposed on Lot 33. A note to this affect rvi//be added to the fina/p/at-as been ea�/ier proposed during the pre/iminary p/at process Further, discussions dwring pre/iminary p/at review, Nei/Watts had agreed to not requiring those properties previous/y developed before annexation to be induded within the futur�e detention faci/ity. We do not propose to connect or size the infiltration faci/ity for this Lot 33 since(I)the existing impervious areas were present prior to Jan. 2001 and(2)no further development (impervious) wi//be a/Iowed on this/ot based upon notes added to the fina/p/at. Water: 1. Show meter for lot 34. P/ease refer to Sheet 20 for the added water service for Lot 34. 2. Add Airvac assembly for high point (see sheet 18; approximately Sta 11+02). A 2"Air-!/achas been added to the water p/ans at sta. 11+20 just beyond the fire hydrant P/ease refer to Sheet 18 for /ocation. I will deliver the mylars to you either LATE today or first thing tomorrow morning. Let me know if you need anything further. Darrell Offe Engineers 13932 SE 159th Place Renton, Washington 98058-783� file:'/C:ADocuments and Settings`,mdotsonlLocal Settin�s\Temp`,G�'�'}00OO1.HTM 12/06/2006 Page 2 of 2 Business: (425) 260-3412 Fax: (425) 988-0292 Email: darrell.offe@comcast.net file:/iC:lDocuments and Settings�rrldotsonlLocal Settings\Temp`,.G���}00OO1.HTM 12/06/2006 _ _ _--__ __ __—____ _ _ -- — _ _ _---- _ Michael Dotson - LR-Overflow Route.pdf Page 1 ,,,\ �t �,� �do _. _ .. `��� ">,I� �,�dds1�d�' � y\� `� � _ . � ° �� � I � /� �. ( j i/ ``` � ��/� 1 ��� ' �� _ f � �`� II �'° �; �� 1 �r i , � �� I/ , � �I '�� �"° / ��; I �, �j ,! t � 1 I` %% , i � � 1 1 �� � ;-�_.;; ! r i i� , ; ' '\ �" �` � �� � , •� - ' �� � a `r'i ' _�' ' - —J \ i i �� ( � � � i , , �r , i ��� � , k ����. i ' i � � i i '�.�..�.��;:, �� i � � � ;` � �� :u ; � �„� ;� �� � � � � � '`� ��. . 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