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Home My WebLink About02791 - Technical Information Report JAEGER ENGINEERING 9419 S. 204 PLACE - KENT, WASHINGTON 98031 PHONE (253) 850-0934 FAX (253) 850-0155 2:11 / R April 18, 1999 APR 2 6 RECD PLAN REVIEW DRAINAGE ANALYSIS AND TECHNICAL REPORT FLYNN SHORT PLAT 9 LOTS NE 6th PLACE and BLAINE AVE. NE RENTON, WA. CITY FILE NO. LUA-96-106 PREPARED FOR: Joe Singh (206) 919-6066jetvS J. JAS' . • 0 ti .0 PREPARED BY: "� James J. Jaeger, P.E. ?-5`,.7.41;751t-R� PNALF 4-I1A ;;ti :. 3/'I/ Zoov 4 TABLE OF CONTENTS I. OVERVIEW II. CONDITIONS OF APPROVAL III. OFFSITE DRAINAGE IV. PREDEVELOPED DRAINAGE V. DEVELOPED DRAINAGE VI. DETENTION POND DESIGN � , VII. CONVEYANC-E SYSTEM I ' VIII. EROSION CONTROL ' '� Page 1 of 2 � Ki�g Counly Building and Land Development Divlston ' TECHNICAL INFORMATION REPORT (TIR) WORKSHEET - . . � - . . . . � . . . Project Owner �ri�n�� r►� Projc�ct Name �L 12 S o/'� c �f_ p1ddress �3?.O �' �tle�S�T_iL'�v��l_ Location . Phone ___ ' _ N�R. 9�4a Township-.�_ d __ Project Engineer �A es' �- Range _ �ction __� Company_S °-r' � _ ��1,_� Projocl Size __2�35.--- AC I� Address Phone 4' �.��SdtC�� Upstream Drainaga�asin Size __ AC _._ ��-'�) �SO - 0434 0c�r ---- - -- . . . 0 Subdivision � OOF/G HPA [� Shoreline Management ��i [[�{ Short Subdivision [� COE 404 ��-� -,�{ ��efY � Grading L] DOE Dam Satety lY� Structural Vaults Q Commeraal � FEMA Floodplain L_J Other , Q Other —___ n COE Wotlands l__� HPA • . . - � Community — �--�� ------ Drainage Basin . /� n [� I� L '� \ ------ C�P-dl(7-�- 11-�1�S/' --— ��Y� �0.S_f!I Y1!j 1Y� U � {7iver - , --- ---- �] Floodplain -- ----. -- � Slream . ______ (�J Wetlands � Critical Slream Reach (_] SeepslSprings � Depressions/Swales (� I ligh Groundwater Tabla (� Lake ____ -__-_. - _ -.--_ (� Groundwaler Recharge � SteepSl�s — -- ----- ( _� Other ----------- _ _ --- -- � Lakeside/Erosion Hazard - . S�pil Type Slo�s Erosion F'otontial Erosive Velocilies ps�d�uxs�Q�_ —5Jo- 20,°(�----- - modtur��-e.. ._ _ . . .__S'£��"-�'-----__ --A�-D ----- - ---- ----- - -- - -- - ------ . ( l Additional Sheols Jlttatched .. 1/�N) 4 Pags 2 of 2 King County Buliding and Land Development Dtvlsion � TECHNICAL INFORMATI�N REPORT (TIR) WORKSHEET .� � . • . REFERENCE LIMITATIOWSITE CONSTRAINT [� Ch.4_Oownstream Analysis ��.�'�� P�Y�..��e0 v�_r�. CJ -_ ir O _.__ O -- - -- -- - � o -- --- - r� --- �- -- [� Additiona!Sheets Ariatched • � • MINIMUM ESC REDUIREMENTS MINIMUM ESC REOUIREMENTS _ DURING CONSTRUCTION FOLLOWING CONSTRUCTION � Sedimentation Faalities � Stabilize Exposed Surfaoe dStabilized Construction Entranoe � Remove and Restore Temporary ESC Faalities [/�Perimeter Runoff Control [] Cloan and Remove All Silt and Dobris �Clearing and Grading Restrictions � Ensure Operation ot Permanent Facilities (�Cover Practioes (� Flag Limits of NGPES onsiructian Sequence - 0 Other (�� Other • , • ' - • -- ------- ------- - -`I � � Grass Lined Chan�el � Tank � Intillration Moihod of Malysis � Pipe System �Vauli [] Depression ,_._�R U H (� Open Channel C] Energy Dissapator 0 Flow Dispersal ComponsatioNMitigatlon � �„ Dry Pond � Wetland [� Waiver o(Eliminated Site Siorage � Wet Pond • � Stream � Regional Detention N J�`�" ' Brie(Description of System Operation _�i ��n �`�t'o _�e.'4'2�'�w� Vd.0 �'f" � UJ�� 1�1_I t'. D r�v c..c., r2 s'f'h_� Y'e e�r� � e�s'�t n� _�D�1 Facility Related Site Limitations [� Additional Sheets Attatched Reference Facility Umitation � - � ' (�Drainago Easoment Cast in Plaoe Vault �] Othor � �_� Aocoss Eas�mont 0 Reiaining Wall [ ] Nativo Growth Protection Easement �Rockery>4'High [_�raci � 0 Structural on Steep Slope L__� Olhar • � • • • • � I o�a civfl engi�eer under my�uperviston havo visitod the sita. Actual �Ite conditions e�observed were lncorporatod Into this worlcsheot a�d the � attatchment9. To ft�a best of my knowtodge tho Inlormation provided _ _ here is eccurate. • � 1/90 .� I. OVERVIEW , The proposed short plat consists of one existing residential lot with a total area of 2.35 acres. The proposed short plat will subdivide this lot into 9 single family residential lots. There are no existing structures or other improvements currently on the lot. There are no wetlands, streams, ditches or other water courses on this property. The properfy is bordered on the north and the south (the "long" sides) by existing medium sized residential lots. The southwest corner us near the right-of-way for Sunset Ave. NE. This is the low corner and all utilities will exit the site at this corner and proceed towards Sunset Ave. NE through a new easement from the adjacent property owner. There are no utilities currently on the site. Water and power/phone can be accesses from Blaine Ave. NE at the southeast corner of the properfy. There are no existing driveways or vehicle access to the lot. The lot has frontage at the southeast corner along Blaine Ave. NE. This will be the location of a new cul-de-sac road that will connect to Blaine Ave. NE and run along the norfh side of the properfy to service all of the proposed lots. There will be a standard paved bulb and the end of the cul-de-sac. The new internal street will be a public road and will be called NE bth Court. There will be a sidewalk on one side, the south side, of the new road. There will also be a short private road that will service new ►ots # 7, #8 and #9 from the end of the cul-de-sac. The road layout was reviewed and approved during the preliminary approval process. The short plat received preliminary approval on October 28, 1996. The conditions of approval are attached to this report for reference. The internal road will be constructed to City standards with asphalt surfacing and vertical curbs. , The properfy in its current state has a fairly young second growth forest throughout the site. The trees or groups of trees are shown on the erosion control plan. There is a moderate understory of wild grasses dnd some brambles. The site slopes down from the northeast corner to the southwest corner at an average grade of approx. 15%. The western half is slightly steeper than the eastern half. The proposed drainage will be � collected by catch basins within the new road and routed to a detention vault. The vault will also serve as a water quality enhancement facility by providing dead storage volume under the detention volume as allowed for ca wet vault. The site soils are of the Alderwood series as mapped by the SCS soils survey. � -- _,��: (,/+ � .� t .� �. '«. . �c � a�r �� TI'�'�� - �/ ..._.,. 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Y�-. - ':.`,-yr--�-^e�--- r+i' 'i - �- -- --\_. -y - -- � . - - ��. -'?! ^-- - � %J Y�. � / B - _ _- _ _ _ �o -�--- --. .. ,�, • • _ j6-_ �� --� r ' ' �, I R s rvoir , �° -' - -� � �PC -- � � �f', ' ; - �� ,)�� - - - - --- - - - N � _ � _ So 1� � : •• .-�� Q ,r 2 , � _ - ,1 � � �� 9 A C n�fi Pu �, 1 . . C \. ` ;k T� ; _. - . �� ..� _ - SOl[,.S M� o -{�• q�aM 29". ' !69 i203 �� - _ 2 � � , '•T� � ��c�e.r W o o� SM � �• � � �' _ � i , ,,r- -- `A�.0 ` � � Tu �y/_�� I � n B = �� "-•':� -- InC ) .` �� - � ( I �Q_l;:,; ;( n,.�, . /.:_' � \\_ �•; .��. �.,�t : , '{ � � I ,i �. . r� � , - � - Cot��nc�r�s e� �PPRfl�[�-- �� —/ .3 �' � � , October 28, 1996 OFFICE OF THE HEARING EXAMINER CITY OF RENTON REPOftT AND DECISION APPLICANT: Gregg Kappers,Triad Associates 'I Flynn Short Piat File No.: LUA-9b-106,ShPl L.00�TION: South of NF.6th Ptace,Norkh of � ' Blaine Ave. NE, East of Sunset Blvd. SUMMARY OF REQUEST: To subdivide 2.35 acre parcel into nine lots for development of single family homes. SUMMARY OF ACTION: Development Secvices Recommendation: Approve with � conditions ' , - I DEVELOPMENT SERVICES REPORT: The Development Services Report was received by the �' Examiner on October 8, 1996. PUBLIC HEARING: After reviewing the Development Services Report, examining available information on file with the application, field checking the property and surrounding area; the Examiner � conducted a public hearing on the subject as follows: , � MINU'I'ES The jollowing nrinut�s are a summary of the Oetober 15, 1996 hearing. The/egal reeord�s recorded on tap� The hearing opened on Tuesday,October 15, 1996,at 9:04 a.m. in the Counci) Chambers on the second floor of the Renton Municipal Building. Parties wishing to t,estify were afiirtned by the Examiner. The following exhibits were entered into the record: E�[6ibit No. 1: Yellow file containing the original Exhibit No. 2: Vicinity map applicallon, proof vf posting, proof of publication and other documentation pertinent to this request. Es6ibit No.3: Short plat map ' The hearing opened with a presentation of the stafl'report by MARK PYWELL, Pmject Manager, Development Services, City of Renton, 200 Mill Avenue South, Renton, Washington 98055. The applicant seeks to subdivide approximately 2.3 acres into nine single family lots. The lot sizes would range from approximately 5,800 square feet to over 14,000 square feet. The short plat is located east of Sunset Boulevard and the I-405 ' comdor, with NE 6th Place to the north and I31�ine Avenue NE to the south. Short plats arc exempt from ' !� SEPA review in accordance with both the City's environmenta) review ordinance and the SrPA RCW. I t . Gregg K�ppers, Triad Associates � Flynn Short Plat File No.: LUA-96-106,ShPl October 28, 1996 Page 2 The Comprehensive Plan(CP)designates tl�is area of the City as Residential Single Family. Tl�e short plat would allow for the construction of nine single family homes, one for each of tlie nine proposed Iots. Development densities in this area are S units per acro with a range of 5 to 8 dwelling units being acceptable. There are l.8 net developable acres on U�is site after tl�e road area is subtracted from tl�e gross acreage which was 2.3 acres. Net density would allow for a range of single family homes of 9 to 14 lats. Tlie applicant is t�equesting nine lots due to the shape and configuration of the parcel. Tl�e CP also indic�tes that the minimum lot area for the single family rtsidential zone is 4,500 square feet. As noted, the pmposed lots would range from approximately 5,800 to 14,600 square feet. Again,the lot sizes have bcen dictated by d�e existing shape ' of the lot that is being subdivided and the need to provide adequate access to eacl�of those lots. Minimum dimensions are SO by 65 fcet except for cuf-de-sac blocks whero the frontage is allowed to be reduced, and again the lots have been designcd.to comply with the City's regulations. Aooess to the lots will be from Blaine Avenue NE onto the cul-de-sac road. The cul-de-sac road will traverse across the north side of the subject property. There will also be a short private road coming off the end of the cul-de-sac in accordancx with the City's road standards, and that will provide access to the westerly three lots, Lob 7, 8 and 9. Lot 6 could potentially get its access either from the private road or directly from the end of the cul-de-sac. The E:amieer asked if it would be possible to extend the road to the west and then to tl�e north to provide sooess to what looks like larger lots along Sunset that eventually could be subdivided. Mr. Pvwell responded ' that staff did not feel that was necessary at this time,and that thera were topographical constraints to be considerod. The Examieer stated his concem that the location of the proposed cul-de-sac road would mean that lots fronting on NE 6th Place would have a road in front of and immediately behind U�em. What used to be one single family Iot is now going to provide 90 vehicle trips on the average per day along the rear lot line of lots that usod to have private rcar yards. Mr. Pywel) statod that staf�'did look at that potential, but one of the problems wes if a road was brought in directly along the south property line it would make for a very sharp angk just beforo the intersection between where Blaine Avenue NE makes the corner. Also between NE 6th Place and what is being identified as NE 6th Court on the north side of the subject property there are some topaigraphical changes so those lots would not have direct access onto both streets which is one of the concerns staff usually has with a configuration of this sort. The high point of the Ibt is around the Blaine Avenue area. lt generally slopes downward towards the west and then�there is a drop-off in the southwest corner where it leads down to Sunset Boulevard. In order to get the flows from both the drainage and the sanitary sewer,they will need to connect out with Sunset Boulevard. Frorti discussions with other City staf�', it is notod that in order to bring the sewer back up towards Blaine Avenue, it would most likely require some sort of lift station. Bringing it out lhrough the southwest corner to Sunset Boulevard is a more acceptable solution to the City. Staff is recommending that fencing be installed along the rear portion of the proposed lots, and again either fencing or a landscape buffer between the road end the existing residences along NE 6th Place,and also to the east. Police and Fire have indicated they have adequate resources to furnish services to the proposed development, subject to the applicable code requiremcnts. There is a fire mitigation fce of S4R8.00 for all ncw single family sUvetures. 7�ere are several recreation parks in the vicinity of this subject property and tl�ere is also a � Gregg Kappers, Triad Associates Flynn Short Plat � File No.: LUA-96-l06,SI�P1 October 28, 1996 Page 3 recreation mitigation fee of 5530.76 per single family home. The Renton School District has identified the schools d�at the students would attend,and tl�ey feel they have the capacity in those scl�ools to handle the students. It should be noted thst airoraft accessing the Renton Municipal Airport do over-fly this area and tl�at they sometimes are at (ower elevations; less tl�an 1,000 feet above ground level in this particular are�as they approach the airport. For street improvements, staffwould also note that the Transportation Division has establishod a mitigation fee of�75 per new net trip generated by each of tl�e nine lots. Concerning the stortn water,the preliminary design has been found acceptable, but the final design will need to be approved by the City. At this time thero are no easements for the storm water nor the sanitary sewer across the adjscent property. Without some assurance that the sl�ort plat will be approved, the easements would not do the City any good. �, At this time staf�'would tecommend approval of the short plat, subject to the conditions contained in the staf�' t+epott. �EFF COX,Triad Associates, 11814 I 15th Avenue NE, Kirkland, Washington 98034, applicant reprcsentative herein, statod there were ongoing discussions with the adjacent property owners rogarding easements of this paroel. There is also an existing power pole easement that runs along the west property line which is being � investigatod. ' He explaine�the different reasons for locating the proposed detention system at the lowest portion of the site, and that, if necessary, service can be accessed from down below through the utility easements that must be obtained for water and sewer. �tOBERT SCHALKLE, 664 Sunset Boulevard NE, Renton, Washington 98056, stated that he owns the large piax of property to the south of Mr. Sokolsky's, who is the owner vf the adjacent property to the south of the subject site. He statod that Mr. Sokolsky does not own enough property on Sunset to do what the applicant is talking about as far as running across Mr. Sokolsky's property with a sewer line, but that he does. He feels there hes boen a lack of communication between the applicant and the adjacent property owners. He esked on behalf of Mr. Sokolsky if there was going to be a fence on the south side. Because of the contour of the land, part of the property is level witli Mr. Sokolsky's,then it goes up and then down into a gully. He was also concerned about the water drainage from this site. .IOHN W[LLENBORG, 2205 NE 6th Place, Renton, Washington 98056, spoke as an adjncent landowner. He exprr.ssed his concern that proper notice ottlie heating was not given. Mr. Pywell responded that it was his understanding that the notice went out properly. 71�e applicant provides tl�e mailing address labels and the postage,but the City dces the mailing. Mr. Willenborg felt the Iarge Iot sizes of 14,000 square feet were not comratible with tl�e adjacent smaller lots. Ne als,o asked if he could access the new public road at the back of his property, and was told he could if he obta�ntd the proper curb cut permit. He also commented regarding the ownership of the rroperty, assessments , which might be owing by adjacent owners, and any new tax assessments. [�e stated that he would like to go on I � Gregg K��crs, 7'riad Associatcs ', � . Flynn Short f'lat , I File No.: LUA-96-106,ShPl Octobcr 28, 1996 Page 4 public record in opposition to the proposed short plat because he would be adversely affected by having a road both in front and back pf his property. KENT CORREA, 670 Sunset Boulevard NI;, Renton, Wasl�ington 98056, stated tl�at {�e owned the triangle parcel at t{�e corner on Sunset Boulevard wliere the qucstion is about tl�e easements. I le asked if tl�ere would be ' feneing on the west side of the subject site, to which Mr. Pywell responded that there would be. Mr. Correa explained his position regarding the utility easements across his property. �iEIL WATTS. Plan Review Supervisor, Ucvelopment Scrvices Division, City of Rcnton, 200 �4ill Avenue � South, Renton, Washington 98055, addressed the issue of street location on tl�e subject site and best access for � the proposed lots. He also addressod the concerns of the drainage for tliis project,as well as landscaping and maintenance agreements for its upkcep. � � The Eaaminer called for further testimony regarding this project. 7here wns no one else wishing to speak, and f no further comments from stat�: Tl�e liearing closed at 10:10 a.m. � I FINDINGS.CONCLUSIONS& DECISION I � Having reviewed the record in this matter,the Examiner now makes and enters tl�e following: � 1. The applicant, Grogg Kappers,Triad Associates, filcd a request for approval of a 9-lot short plat. 2. The yellow file containing the stati'report, the State Environmenta) Policy Act(SEPA)documentation � snd othu pertinent materials was entered into the record as Exhibit#I. 3. The Environmenta)Review Committee(ERC), the City's responsible official, determined that the , proposa) is exempt from an environmental assessment. 4. The subject proposal was reviewed by alt deparht�ents with an interest in the matter. 5. ' The subjoct sit4 is located east of the 600 block of Sunset Boulevard NE The site has no frontage along ' Sunset. Blaine Avenue NE ends at tt�e southeast comer of the site. Tl�e site is located north of NE 6th CouK and South of NE 7th Strect. 6. The subject site is a roughly triangular parcel approximately 2.35 acres in size. The westem property � line is approximately 299.22 feet long. The southern property line is approximately 567.23 feet long. 7. The subjxt site slopes downward generally from east to west from approximately 240 feet to !b0 fcet. The area north of the site also rises. 8. City maps incorrectly show the property located abutting the southwest corner of the site as part of the Sunset Boulevard right-of-way. 'il�e property is in private ownership. Thc parccls south of the subject site achieve access to Sunset througl�either pipestem driveways or easements. 9. Tl�e applicant proposes dividing the subject site into nine single family lots varying in size from 5,842 '�, square feet to 14,662 square fect. Tl�e lots would generally n�n in one tier from Proposed Lot 1 at the i� � southeast corner of the site to Proposed Lot 9 in the northwest corncr of the site. I Greg�g Kanrcrs, Triad Associatcs . Flynn Short Pl�t File No.: I.UA-96-I OG,SI�PI October 28, 1996 Page 5 10. 7�he following dimcnsions apply to ll�e lots proposcd for tl�e subject site. Proposed Lot� Anprox. Width Approx. Det►th Square FootaQe 1 69.26 109.52 7,021 2 5 8.00 120.90 6,6 89 3 55.00 120.90 6,G07 4 83.00 82.90 5,842 S 108.00 82.90 7,100 6 98.00 144.16 10,�133 . 7 75.00 243.38 14,G62 8 119.20 88.89 9,632 9 105.00 88.89 8,274 11. Utility lines for water,sewer and storm water aro located in the Sunset right-of-way. Domestic water is slso located in Blaine. NE 6th Place is uphill fmm the subject site and neither sewer nor storm water services are available in this street for this site. The applicant will require an easement from an abutting � property owner in order to extend sewer and storm water utilities to the subject site. The applicant has not achievod any easements at this time. 12. The subjeet site is loeated within tl�e Renton School District. Scl�ool assignments are made on a space available basis. The proposed plat will generate approximately 7 students distributed through the various grades. 13. The proposed plat witl generate approximately 90 vehicle trips per day. The applicant will be paying a trafTe mitigation fee. Staff has noted that the local roadways have capacity to handle this additional ' trafTic. 14. The applicant proposes a combination of a public cul-de-sac street and a pri�ate easement roadway o�' the cul-de-sac td provide access to tlie general site and to the interior lots. The public road would extend Blaine to the north. The public roadway would then turn west and run along the north property line. The public road would provide access to Proposed Lots 1 through 6 and possibly Lot 7. At the cul-de-sac a private 40 foot wide easement would provide access to Proposed Lots 7� 8 and 9. 15. The public ruad anJ easement roadway would create an unusual situation in wl�ich the tier ot lots to the north would have a public road adjacent to both the front yard and rear yard. This will subjoct these , homes to more traffic noise than is generally found where.a block of lots has a roadway on only one side. The roadway may be available to the residents of the northern homes but d�at wonld de�end � the topography of those parcels. 71�e topography was not available at the public 1�carir 16. In addition, the alignment of the roadway appears to create a small remainder parce) at edge of the parcel. The applicant proposes dedicating this parce) to the City but with U�c proviso u� the applicant or eventual homeowners'association maintain the landscaping. 17. Staf3'has recommended that die applicant scrcen the northern lots by the installation of a fence and landscaping as appropriate. 18. There have been drainage problems in the area in the past due to tl�e terrain. 71ie arplicant proposes creating a detention system in the southwest corner of the site. 7�I�e systern would straddle the common Gregg K�rpers, Triad Associatcs . Flynn Short Plat File No.: LUA-96-106,ShPl Octobcr 28, 1996 Page 6 19.' 7�he applicant wi11 be paying a Parks mitigation fee to offset the impacts on the park system of developing this site. 20. Two out-buildings belonging to otl�ers intrude on the subject site. Tliese structures will have to be removed prior to the approval of tl�e sl�ort plat mylar. CONCLUSIONS: 1. , The proposed plat generally anpcars to serve the public use and intcrest,althougli it appears that in � order to generate the apprupriate density, a roadway will be created abutting tl�e rear lot line of an � existing tier of single family I�omes. The subdivision will provide additional I�ousing choices in an area with urban services. The development should not tax either the ro�d system or tl�e existing utility infrastructure.�Development of the additional lots will also increase tl�e tax b�e of the City. 2. The proposed plat will also permit infill in an area with services and avoid urban sprawl. This site is just outside of downtown Renton and should serve as a good location t'or new single family homes. 3. The proposed lots are generally rcctangular although two are ratl�er narrow and deep. In any event, they do appear to provide reasonable building envelopes. 4. While the proposed madway ofi'ers a reasonable intersection, it does create a non-traditional situation where single family homes have roadways both in front and back of tl�c I�omes. It would appear that if additiona)consideration had been given to the impact on the northern homes, a difi'erent road arrRngement might have been achieved. The intersection might have been Icss than optimal or the applicant may have achieved fewer lots, but planning principles do involve occasional tradeoffs to ' lessen the impacts of new development on existing development. S� There is no question that the applicant needs to protect the northern homes from the impacts of having a � � second road abutting the rear of their homes. The applicant shall install landscaring and shall maintain I �; that landscaping. The owners of these northern homes shall hnve tlie option of being provided a i pedestrian fence, a driveway or continuous fence as they decide. The applicant shall work with these ' property owners to attempt to determine if curb cuts are desired as the street is designed and � constructed. Any subsequent curb cuts or alterations of tl�e abutting Inndscaping shall be the responsibility of these neighboring lots slthough the landscape maintenance shall remain with the ', subject site's homeowners association. I 6. The homeowners association shall also be responsible for maintaining the remainder parcel east of the Blaine extensibn. 7. Zhere are a number of easements that will be created on this prvperty including the storm water �I detention system, access to d�at system, as well as the easement roadway. 77�e homeowners shall be I , responsible as appropriate for the maintenance of these areas. • , 8. ln conclusion, the proposed Short Plat aprears acceptnble as long as the homes north of the site remain , protected by both landsca�ing and a fence and the a�plicant achieves en eascment for utility lines ' linking the site with utility lines in Sunset E3oulevard. i Gregg Karrcrs, Triad Associntes . Flynn St�ort 1'lat File No.: LUA-96-106,SIiPI October 28, 1996 Page 7 DECISION: The Flynn Short Plat is approved, subject to the following conditions: 1. The applicant will need to record an access easement to City of Renton standards on Lots 6, 7, 8 and 9 for the'private road. The easements will also need to note that tl�e maintenance of the private road is the responsibility of the landowners using the road. These documents wil) need to be prepared to the satisfaction of the Development Services Division and recorded prior to or at the time of the short plat. 2. , The applicant shall create and record a homeowners association that will be responsible for the � . maintenance ofall common areas, facilities, and structures except for the private road identitied in Condition 1 above. The documcnts creating the homeowners association shall be rrepared to the satisfaction of the Development Services Division and recorded prior to or at the time of the rocording of tl�e short plat. 3. The applicant shall be responsible for the removal of both sheds that are sliown in the rigl�t-of-way for the cul-do-sac. These sheds shall be removed prior to the recording of the short plat. 4. The applicant shall construct a wood fence along the rear property lines of Lots 1 through 9 inclusive and along the north and northwest property line of Lot 9. This fence will need to be installed prior to the recording of the short plat. S. The applicant shall install sight obscuring landscaping, consisting of a mixture of trees, shrubs,and ground cover along the north side of'the public road,the private drive and the cul-de-sac and also along , the east side of the cul-d�saa 71�e landscape plan will need to be approved by the Development Services Division prior to the recording of the short plat. In addition, a fence shall be installed elong , , the property line. The applicant shall work with these homeowners to determine if they want pedestrian or vehicular access fo'ihe nevii roadway. � i 6. A fire mitigation fee of�488.00 per new single family home is required prior to or at the time of the � recording of the short plat. 7. A parks and recreation mitigation fee of 5530.76 per new single family I�t is required prior to or at the , � time of recording the short plat. ' ' 8. A transportation mitigation fee of$75.00 per new trip generated is required at the time of or prior to the I�' recording of the short plat. It is anticipated that each lot will generate ten(10)trips per day. I � 9. The applicant shall obtain and provide all required utility easements across the adjacent parcels. Al) j utility easements will need to mcet City of Renton standards. The easements shall be recorded prior to or at the time of the recording of the short plat. � �I i � I I� Gregg K��pers, Triad Associaics Fiynn Short I'lat ' File No.: LUA-96-106,ShPl October 28, 1996 Page 8 ORDERED THIS 28th day of October, 1996. �, � � I'� FRCD J. KA MAN HEARING EXAMINER TRANSMITTED THIS 28th day of October, 1996 to the parties of record: Mark Pywell , Jeff Cox,Triad Assoc. Robert Schaike 200 Mill Avenue S• 11 S 14 115th Avenue NE 664 Sunset I31vd. I Renton, WA 98055 Kirkland, WA 98034 Renton, WA 98056 John Willenborg Kcnt Correa Neil Watts 2205 NE 6th Place G70 Sunset f31vd.NE 200 Mill Avenue S Renton, WA 98056 . Renton, WA 98056 Renton, WA 98055 Douglas Thornton Joyce Treadway Maxine Motor 672 Sunset 81vd.NE 2221 NE 6th Place 8301 20t1� NW Renton, WA 98056 - Renton, WA 98056 Seattle, WA 98117 Davs Petcrson Mnry Ann Flynn 679 Camas Avenue NE Sandra L.ee Ocha Renton, WA 98056 8320 84th Avenue SE Mercer Island, WA 98040 TRANSMITTED THIS 28th day of October, 1996 to the following: Ma�or Jesse Tanner , _ . Grcgg 7immerman, Plan/E3ldg/PW Administrator ' Members, Renton Planning Commission Jim Hanson, Development Services Director Art Larson, Fire Matshal Mike Kattermann, Technical Services Director Lawrence J. Warren, City Attorney James Chandler, I3uilding Official Transportation Systems Division Jay Covington, Mayor's Executive Assistant Utilities System Division Councilperson Kathy Keolker-Wheeler Valley Daily News Pursuant to Title IV,Chapter 8, Section l5 of the City's Code, request tor reconsideration must be fited in �vtitioe on or before S:OOp.m.. November 11. 1996. Any aggrieved person feeling th�t the decision of the � Examiner is ambiguous or based on erroneous procedure, errors of law or fact, error in judgment, or the discovery of new evidence which could not be reasonably available at tl�e rrion c�aring rnay make a written request for a review by the Examiner within fourteen (14)days frorn tl�e date of tl�e Examiners decision. This request shall set forth the specific ambiguities or errors discovered by sucl� appellant, and tt�e Examiner may, after review of the record, take further action as he deems proper. An appeal to the City Council is governed by�'itle IV, Chapter 8, Section 16, which req��ires that such appeal be ftled witli the City Clerk, accompanying a filing fee of$75.00 :�nd meeting other s�ecified requirements. � III. OFFSITE DRAINAGE A. UPSTREAM DRAINAGE The upstream drainage contribution to this site is negligible. The only upstream areas are along the north and east property lines. The east and norfh property lines have residential lots thot ore fairly shallow and will not � generate much runoff to the site becouse of their small ared. The lots along both properfy lines are fronted by NE 6th Place (north side) and Camas Ave. NE (east side) which are City roads that have curb and gutter that inter�ept any drainage that may flow towards the subject properfy. The south and west are downgradient from this plat. B. DOWNSTREAM DRAINAGE The drainage from the site will be discharged from the detention vault in the southwest corner of the shorf plat and into a new conveyance pipe within dn easement on the property to the southwest, between the site and Sunset Blvd. NE. This offsite conveyance pipe will run to the southwest and will connect to the existing drainage system that runs along the norfheast side of Sunset Blvd. NE. This existing system is 12" CMP pipe at a slope of 4.12%. This pipe runs under the road gutter to the southeast for approx. 40 ft. past the proposed new connection point. At this point it enters CB # G6-5 (per the City maps). The outlet from this catch basin flows to the southwest, across Sunset Blvd. NE and towards I-405. It is transported under I-405 in an 18" CMP pipe according to the WSDOT plans. Within the drginage system under I-405, there are several drainage pipes that enter from the east ond pass through to the west side of the freeway. West of I-405, there is a 30" concrete pipe outfall that discharges into the beginnings of a broad ditch that flows north between the railroad tracks and the extension of Houser Way. The ditch is opprox. 10 ft. wide and flows to the north. The ditch accepts additional pipes from under I-405 as it flows to the north. The pipe from the subject shorf plat appears to enter this ditch. South of N. 8th St. , the ditch enters two ' 36" concrete culverts that were installed by the City as part of the Houser � St. improvements. After leaving the culverts, the ditch travels approx. 100 ft. north where it enters the N. 8th St. drainage system. There is a 36" concrete pipe at this entry point. According to the City maps, this system then flows west in a 42" concrete pipe network under N. 8th St. The N. 8th St. piping flows to the west. � � � � � � � - - - -i w �� ;'��I�� r � 1 - ,r.'. •�/ �� ' ��' ..,�! - �!� ��. �'��. ' �,��__ �� . �. �.�„� ;� /.i��-� --- - - - -- -- ��__ _ �4 ��' ! .. � �, : • • � � a - Q o � � �� s �I!'��J��I►�►- �5�� ...� ;��.1 � , .� � __ �Q�� +��/ �� / �� ,��,� �� F�l�1 (� . �� . ■ •� � �i ��+ . � ��e � A � �j � � � �i►$ ��,�� ■ , �.� � �.!`�:� �� _ /i►,.� . ��1; �� - �.''�.7 �.:�� ..��i'ii�/f�l C -� �_ � P \ �� I�,��,�� ,`�,� ��i� •%�� .�.� �� p �� 1��; :�:� �i�� 1��r�� t`' �r�� 7�� Q� � ,�`:. , : . _____-_ � � � � e� ��ri�► �� •�� ■ - ,�. . ,,,,,,f�►�:�� i �-��>��1� � +� � �� .►~ ,� .,��,��j��-�1Q �� r i� . �. _ �i � � � �._�i�� ■� I�1 � r �� . � � � • s�� i� i��i�1 � . �� , ,\ �':�� '��o�'�•jI� c�i�� 1 fi�a�� . �A�O�� `\ �� Il� �' ��_.�'� �I �, ''�'�1 � A,� ��1�� r.� i, , .�l� _ �� ♦ ��i� ��r ��g� �, �� ;�,; _,�,��. �1�1� �� '��1� ►�� a � � �� \ �� R t�� * � `� '�� • r ' 1�� :!�\� ��r�� . ``` �� `•�� ♦J,�� `1 ( , !t!�:, � �� \1��y�� ,•.w �,,��► � '� • �� 1�� `� , `�� , , . � � �I] ♦ -� � �� ►, ��-� �� i �� 'i. , � � � , �� ,,.� �/ , ►r�� . ��,�� ,�o -�«' ��i�I; � , . , . .. �,�.�, ��•� �� ' , � ��j . . 1 �� , � ��. ■ . . i�� g , � , � I II� �v��..�me��aa�.��a��a��.so� �i � � � � ��1�r ��s , �� 1 '� � •�� `0��.�_� �� .� ♦ I ��. .. �, � � , • - � �. , ��,,�� ,�� ,.._�� lj�� .► �l�� ;� �1� �.. , I��l�!�M� � —�' �� ,��o�s� �.� ��.�� .��,. �� . �� . . � ; �,. _ _ _ •�•. , �3 ,r �� .� IV. PREDEVELOPED DRAINAGE The drainage from the existing site currently sheet flows to the southwest across the existing vegetated surtace. This surface is moderately dense , second growth trees, primarily deciduous trees, with a fairly dense understory of tall grosses, native shrubs and brambles. There are no drainage improvements on the site. The sheet flow eventually ends up within the north gutter of Sunset Blvd. NE. There is a catch basin and piping within the adjacent properfy to the west, but this CB is south of the site and may pick up a portion of the flow. It also discharges into the drainage system within Sunset Blvd. NE. The total site area of 2.35 acres , was used as the tributary drainage bosin. The existing droinage analysis was performed using the "Waterworks" hydrology software and its summdry tables and charts are attached for reference. The methods outlined in the King County Surface Water Droinage Manual were used as guidelines. Following this page are the data sheets used for the computer inp�t data. The computer summary sheets for peak flow and time of concentration calculations are also attached. Below is a brief description of the existing drainage characteristics: Time of concentration: 55.68 minutes � 2 year peak flow: 0.12 CFS , 10 year peok flow: 0.33 CFS 100 year peak flow: 0.66 CFS i total area: 2.35 acres pervious area: all acres curve number. 81 I impervious area: none curve number: � 98 �� S�'J ��1' 0 = oa t c� s� � '4 =01� S�J '2�'� � Z� . �,,,p�,�ro ' S�-a�$a r�}-{ w�-su� ) S IV�►� �}-sd�c3 I�� ' � --, . U� b, � _ �� •u� ►�• z = d � .U� a .Z : � �}� �3 �� .S.� . $,� � .W .cl •M,s'�'�() S 1�d I l� C1'1c14S� ' �7 � �I�S.5 � bE� � +� �Z�ZS - Z-�1 + '11, =�.�. C� -�� a�� ,S� i-a-�,c�u�W 6�' � = z,l� . ► c�5 Z Q/o 8 ' �1 - O�I - Z = ��S ''� •.s,s�a,,�,$ � .s�o pc� �a�p �oj.�. �au�r-o� �o�l-�s �052 = Z�`�- �9 ' ��5��-o�'�� s�,�r�t W bZ'ZS = '�-�-� 00� %o��b� "Z crz -- -b , - aJ�� •a� �ss� � s�oc�'� ,�►'an� rn o�. ,.�,.�a� �Qp� : �-�1) '�►� I'u'"°`�,J., �'� �. ��y� ry o�..,�N� �o �� - � � � .�— = C'��w��,W�N -�"� � gzs � I�'! a � �I d � �'F� Z�S �� °-� � ' ��w �,n��s�c1 �'�'� � � �`�"� �� ) . � c�c, -�YSc� �. �o v�-�vts�sro � ��c"�. '�" � sai S � ocn � �-� �rro� _..s �S �9 ��v_ c � �° -� � �� .ys�,� s�� o ��-�pu� :��8�� ow ',o .�'a�c� � ooc�n m� � �� tp � �'� �� ,-�o�-�,-a�v�� .�.t� ��,y,s�a a� � �� N�� : �'�9u1n111 �1�� (Y� z mm��9 �� ' s�'2 � �a� a{,-' s I�I-°.l � :�d=�2� � � � �� — --_ _ _ . --- - . _- ---s�-�- -'��lNl�i� i d 'S NN�.'1� . Jaeger Engineering • FLYNN SHORT PLAT DRAINAGE CALCULATIONS PREDEVELOPED HYDROGRAPH SUMMARIES 1____________________________________________________________________ BASIN SUMMARY BASIN ID: A10 NAME: PREDEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs �RAINFALL TYPE. . . . : USER1 PERVIOUS AREA . PRECIPITATION. . . . : 2 . 90 inches AREA. . : 2 .35 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 55 . 68 min IMPERVIOUS AREA ABSTR.ACTION COEFF: 0 .20 AREA. . : 0 . 00 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 300 .00 ns : 0 . 8000 p2yr: 2 . 00 s : 0 . 140o TcReach - Shallow L: 250 .00 ks : 3 . 00 s : 0 . 1680 PEAK RATE: 0 .33 cfs VOL: 0 . 24 Ac-ft TIME : 490 min BASIN ID: A100 NAME: PREDEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USSR1 PERVIOUS AREA �RECIPITATION. . . . : 3 . 90 inches AREA. . : 2 . 35 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 55 . 68 min IMPERVIOUS AREA ABSTR.ACTION COEFF: 0 .20 AREA. . : 0 . 00 Acres CN. . . . . 98 . 00 ' TcReach - Sheet L: 300 . 00 ns : 0 . 8000 p2yr: 2 . 00 s : 0 . 1400 TcReach - Shallow L: 250 . 00 ks :3 . 00 s : 0 . 1680 PEAK RATE: 0 . 61 cfs VOL: 0 .40 Ac-ft TIME : 490 min BASIN ID: A2 NAME: PREDEVELOPED, 2 YEAR � SBUH METHODOLOGY TOTAL AREA. .�. . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs '�� R.AINFALL TYPE. . . . : USER1 PERVIOUS AREA ' PRECIPITATION. . . . : 2 . 00 inches AREA. . : 2 . 35 Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 81 . 00 'I TIME OF CONC. . . . . : 55 . 68 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 00 Acres CN. . . . . 98 . 00 i TcReach - Sheet L: 300 . 00 ns : 0 . 8000 p2yr: 2 . 00 s : 0 . 1400 �� TcReach - Shallow L: 250 .00 ks : 3 . 00 s : 0 . 1680 PEAK RATE: 0 . 12 cfs VOL: 0 . 12 Ac-ft TIME : 520 min PR��D�U ELc�P�f/� �y�R'O C R�p�-� I, Sv,mm��r� � . File Basin Hydrograph Storage Discharge Level pool 3eee5�ee�ee�eeee��ee�eeeeeeeeeeeeeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeee ; eeeeeeeeee; 0 0 ' SHEET �LOW CALCULATOR - INITIAL 300 FEET o o , 0 0 0 0 °DES°Mannings Sheet Flow. . . . . . 0 . 8000 0 0 °ARE°FlOW Length (ft) . . . . . . . . . 300 . 00 T-r� °HOICES ° °RAI°2 yr 24 hr rainfall (in) : 2 . 00 ° ° °TIM°Land Slope (ft/ft) . . . . . . : 0 . 1400 ° ° °TIM° COMPUTED TRAVEL TIME (min) : 52 . 29 ° ° oRAIo TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° oABso 0 0 °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° ° °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . . 0 . 05 °Y o ° °Cultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° ° °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 ° ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° ° 0 oBermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 .41 o a 0 oRange (natural) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 13 0 0 °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 .40 0 ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 ° ° °TOT° o 0 °OF10Key: QUIT F5Key: CLEAR °ete ° ° Pgd�e��e�eeee��eeeeeeeeee��eeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° �e��e��eeee��e��eeee�eeeeee��eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef File Basin Hydrograph Storage Discharge Level pool 3e�eeeee�eeeeeeee��e��eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; , ° INPUT, MODIFY OR BROWSE DATA ° ° 5eee��eeeee��eeeeeeeeeeeeeeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeee�eeeeee ; ° ' °DES° SHALLOW CONCENTRATED FLOW CALCULATOR ° ° I °AREo . o o I oRAIoFlow Length (ft) . . . . 250 . 00 TT ° ° °TIM°Land Slope (ft/ft) . . 0 . 1680 2 ° ° °TIM°Kc, Velocity Factor: 3 .0 ° ° oR.AIo COMPUTED TRAVEL TIME (min) : 3 . 39 ° ° °ABS° TYPICAL VELOCITY FACTOR VALUES - R=0 . 1 0 0 °BASo 0 0 °STO°Forest with heavy ground litter and meadows (n=0 . 10) . : 3 ° ° ° °grushy ground with some trees (n=0 . 060) . . . . . . . . . . . . . . . 5 ° ° °PER°Fallow or minimum tillage cultivation (n=0 . 04) . . . . . . . : 8 0 ° °ARE°High grass (n=0 . 035) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 � � °CN °Short grass, pasture and lawns (n=0 . 030) . . . . . . . . . . . . . : 11 ° ° ° oNearly bare ground (n=0 . 025) . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ° ° ° °paved and gravel areas (n=0 . 012) . . . . . . . . . . . . . . . . . . . . . . 27 ° ° °PEAo 0 0 °PEA°F10Key: QUIT FSKey: CLEAR ° ° °TOT�e��Ceee��e��e�eeeeeeeeeee��eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee��eeef ° ° HOME END F1 :Find F2 :New F3 :Get F4 :Tc-Calc FS :Delete ° ° Pgup Pgdn F6 :Compute F7 : F8 :Method F9 :Template F10 :Exit ° ��eee�e��e�eeeeeeeeeeeeeeeeeeeeee�eeeeeeeeeeeeeeeeeeeee�e�eeeeeeef _ � _ '1�T, -�TTz � PR�pEv�—c��P� = 5S� (�� m,n , �r�cn� o� C�rs�T��o� V. DEVELOPED DRAINAGE , The developed project will include the new concrete detention vault and wet voult lo�ated in the southwest corner of the site. It will be located within drainage easements for the respective lots. The site drainage will be routed into the vault using catch bosins and pipes located within the new road. Each new lot will be furnishes with a piped drainage stub that will be connected to the street drainage system or piped directly into the vault. The areas used to calculate the flows were the same as those areas used in the predeveloped drainage calculations. The detention pond was sized to meet the performance criteria established by the City of Renton standards. This criteria is that the pond can only release at a rate not to exceed the 2 year predeveloped peak flow while retaining the 2 yeor developed peak flow. This is the same for the 10 year and 100 year peak flows. A 30� additional volume factor of safety is added to the , detention pond design volume that was calculdted for the 2 year and 10 yeor storms, as specified in the King County Manual. The 100 year storm volume is not subject to the additional volume factor. The site is too steep for a biofiltration swale to be constructed. Thus, a wet vault will be used to meet the water quality standards. The wet vault will utilize the detention vault and will provide the required dead storage below the detention live storage. The volume for the dead storage will equal the , volume of the water quality design storm, the 6 mos. storm. Per the King County Manual, the 6 mos. storm is calculated using 1/3 of the 2 year storm isopluvial. Similar to the existing condition, the SBUH hydrograph method was used to determine the peak flows for the various storm events. A level pool analysis was performed to evoluate the pond performance during the various required scenarios. The computer data sheets for the developed flows follow this page as well as the works sheets and the time of , concentration calculations. A brief summary of the developed drainage characteristics dre: time of concentration: 5.07 minutes 2 year peak flow: 0.75 CFS 10 year peak flow: 1 .28 CFS 100 year peak flow: 1.91 CFS total area: 2.35 dcres pervious area: 1.41 acres ' curve number: 86 impervious area: 0.94 acres curve number: 98 _ � , s� �� , � _ �� , _ .S`�'� �2 , � ; a�� S�J �L'p s Z� �''�°�'��..i,,.��„`.��''";�� 1 S�o� �-b�� d'�d C�r3Q ' � .,'�,�--., �y / u� 6 •£ - �d u� 6• Z �d = u, �.Z : zd `,,.o�,, '�;,v� �a�o ra ti-t�-a-I� a o�. �, a„�,c� � ; , S'�1�11!�<1"id G�SZ , � �,�u,ut �o S = �-b �o +-�� s Zl1-'►- `L.1. ='�,�. �� 'ro �'aS� s`'-},c`u`�,�, c-c�b 'O = ��.. 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Jaeger Engineering � FLYNN SHORT PLAT DRAINAGE CALCULATIONS DFs'VELOPED HYDROGRAPH SUMMARIES BASIN SUMMARY BASIN ID: B10 NAME: DEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 .35 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 1 .41 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 5 . 07 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 .20 AREA. . : 0 . 94 Acres CN. . . . . 98 . Q0 TcReach - Sheet L: 70 .00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1140 TcReach - Channel L: 365 . 00 kc:42 . 00 s : 0 . 1150 PEAK R.ATE: 1 .28 cfs VOL: 0 . 39 Ac-ft TIME: 470 min BASIN ID: B100 NAME: DEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 1 .41 Acres , TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 5 . 07 min IMPERVIOUS AREA ' ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 94 Acres � . CN. . . . . 98 . 00 ' ' TcReach - Sheet L: 70 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1140 ' TcReach - Channel L: 365 . 00 kc: 42 . 00 s : 0 . 1150 ; PEAK RATE: 1 . 91 cfs VOL: 0 . 58 Ac-ft TIME: 470 min ', BASIN ID: B2 NAME : DEVELOPED, 2 YEAR �I - SBUH METHODOLOGY ! TOTAL AREA. . . . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs I RAINFALL TYPE . . . . : USER1 PERVIOUS AREA I PRECIPITATION. . . . : 2 . 00 inches AREA. . : 1 .41 Acr�s � TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 0 ' TIME OF CONC. . . . . : 5 . 07 min IMPERVIOUS AREA I ABSTRACTION COEFF: 0 .20 AREA. . : 0 . 9 - -� CN. . . . . 98 . 00 � TcReach - Sheet L: 70 .00 ns : 0 . 150o p2yr: 2 . 0� s : 0 . 114 TcReach - Channel L: 365 . 00 kc:42 . 00 s : 0 . 1150 ' PEAK R.ATE: 0 . 75 cfs VOL: 0 .24 Ac-ft TIME: 470 m. ' i, � , File Basin Hydrograph Storage Discharge Level pool 3e��5��eeeeee" "eeeeeeeeeeee�eeeeee�eeeeeeeeeeeeee�eeeeeee ; eeee�eeeee; ° ° HEET FLO CALCULATOR - INITIAL 300 FEET o 0 0 0 0 0 °DES°Mannings Sheet Flow. . . . . . 0 . 1500 0 0 °ARE°Flow Length (ft) . . . . . . . . . 70 . 00 �r� °HOICES ° °RAI°2 yr 24 hr rainfall (in) : 2 . 00 ° ° °TIM°Land Slope (ft/ft) . . . . . . . 0 . 1140 ° ° °TIM° COMPUTED TR.AVEL TIME (min) : 4 . 64 ° ° o�Io TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° o�S o 0 0 °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° o °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . . 0 . 05 °y o ° oCultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° ° °PER°Cul�ivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 ° ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° ° 0 oBermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 .41 0 0 a oRange (natural) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 13 0 0 °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 . 4� ° ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 ° ° °TOT° o 0 ooFlOKey: QUIT F5Key: CLEAR °ete ° ° Pgdee��eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° �eee�ee�eeeeeeee�ee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeeeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; ee ; 0 o CHANNEL FLOW CALCULATOR o 0 °DES°Flow Length (ft) . . . : 365 . 00 ��PE �� o 0 °ARE°Land Slope (ft/ft) . : 0 . 1150 �TZ ° ° I °RAIoKc, Velocity Factor: 42 .0 ° ° °TIM° COMPUTED TRAVEL TIME (min) : 0 .43 ° ° °TIM° TYPICAL VELOCITY FACTOR VALUES ° ° j o�Io 0 0 !i °ABS° Intermittent Flow - R=0 . 2 ° ° �I °BAS°Forested swale w/ heavy ground litter (n=0 . 10) . . . . . . . . . . . . . . . . . . 5 ° ° °STO°Forested drainage course/ravine w/ defined channel bed (n=o . 50) : 10 ° ° ° °Rock-lined (n=0 . 035) . . . : 15 Grassed (n=0 . 030) . . . : 17 ° ° °PER°Earth-lined (n=0 . 025) . . : 20 CMP pipe (n=0 . 024) . . . 21 0 0 °ARE°Concrete pipe (n=0 . 012) . 42 other. . . . . . . . . . . 0 . 508/n ° ° o� o Continous Flow - R=0 .4 ° ° ° °Meandering stream w/ some pools (n=0 . 040) . . . . . . . . . . . . . . . . . . . . . . . 20 ° ° ° oRock-lined stream (n=0 . 035) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 0 ° °PEA°Grassed-lined stream (n=0 . 030) . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . 27 ° ° °PEA°Other streams, man-made channels and pipe . . . . . . . . . . . . . . . . . : 0 . 807/n ° ° °TOT° o 0 °OF10Key: QUIT FSKey: CLEAR ° o ° Pgdeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef ° �eeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef �� — Tl, `�"�T-z, � S�c�'1 rr,.n�fi�s � D�v�v�r� T,rnE oF C�ti�c F,r.�t-R�1-�o r� � � FLY N�! 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O�(nl I . 9 I t�, 44 ►�`7. t�3 File Basin Hydrograph Storage Discharge Level pool � J2eee�eeeeeeeeeeeeeeeeee; a a °Rectangular vault ° °Trapezoidal basin ° °Underground pipe ° °Sto list ° 3eeee�eeeeeeeeL�eeeeeeeeeeeeeeeeeeeeeeeeeeeeee; ° ° RFCTANGULAR VAULT o 0 ° STOR.AGE STRUCTURE ID: 1 0 0 � ' °eeeeef °Name. : DETENTIO VAULT ° °Length (ft) . . . . . . . . . 38 .46 ° �� °Width (ft) . . . . . . .•. . : • 26 . 00 ° °Starting Elevation. : 162 . 00 ° � ��.,G °Max Elev of Vault . . : 167 . 50 ° °Stage-Sto Increment : 0 . 10 ° /`f�� \ °Structure Vol (cf) . : 5499 . 78 ° �, �� J ° Ac-ft . : 0 . 13 ° 0 0 °PGUP PGDN F3 : Get F6 : Delete F10 : Exit ° �c��c��eeeeee��ce��eeeeeeeeeeee�eeeeeeeeeeeeef There may not be enough memory to do large LPool routings Available Memory remaining: 27992 bytes Current Data Set Name : \FLYNN.bsn File Basin Hydrograph Storage Discharge Level pool 3��e��eeeeeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; ° MULTIPLE ORIFICE ° ° DISCHARGE STRUCTURE ID: 1 ° � 0 0 '� °Name: FLOW RESTRICTOR ° , °Peak Dsgn Release Rate: 0 . 00 cfs Orif /flow/elev ° I °Orifice Coefficient . . . : 0 . 62 Dia (in) /cfs/ ft ° °Lowest Orifice Dia (in)-: . : 1 . 55 1 . 55 0 . 15 cfs ° °hl : Outlet to 2nd Orifice: 3 . 60 165 . 60 ft ° ' � °Second Orifice Dia (in) . . . 2 .70 2 . 70 0 . 27 cfs ° °h2 : 2nd to 3rd Orifice. . . : 0 . 00 ° II °Third Orifice Dia (in) . . : 0 .00 ° ' ' °h3 : 3rd to 4th Orifice. . . : 0 .00 ° j °Fourth Orifice Dia (in) . . : 0 . 00 ��0� o �I °h4 : 4th to 5th Orifice . . . : 0 . 00 � oTop Orifice Dia (in) . . . 0 .00 (�E�1 �.�� I K °Elevation of Lowest Orifice. . . . . 160 . 00 ° °Outlet Elevation. . . . . . . . . . . . . . . . 162 . 00 S�.0 L�� °Max Elev Above Outlet . . . . . . . . . . . 167 . 50 ° � °Stage-Disch Increment . . . . . . . . . . . 0 . 10 ° Tn� � Av°PGUP PGDN F3 : Get F6 : Delete F10 : Exit ° Cu��e�e��eeeeeee��eeee�eeeeeeeeeeee��eeeeeeeeeeeeee�eeeeeeeeeeeeeeeeef . File Basin Hydrograph Storage Discharge Level pool Jaeger Engineering 2eeeeeeeeeeeeeeeee ; 3��eee�eee��e��eeeeeeeeee�eee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee; ° • ROUTING COMPARISON TABLE ° ° MATCH INFLOW STO DIS PEAK PEAK OUT ° ° DESCRIPTION PEAK PEAK No. No. STG OUT HYD ° �---------------------------------------------------------------------- � ---------------------------------------------------------------------- °2 YEAR/ 2YEAR 0 . 12 0 . 75 1 1 165 .46 0 . 12 11 ° °10 YEAR/ 10 YEAR 0 . 33 1 .28 1 1 166 . 50 0 . 33 12 ° 0 0 0 0 0 0 0 0 0 0 o , o 0 0 0 0 0 0 0 0 d��'�eee�e��eeeeeeeeeee��eeeee�e�eee�eeee�eeeeeee�eeeeeeee�ee��eef There may not be enough memory to do large LPool routings Available Memory remaining: 27992 bytes Current Data SPr Name: \FLYNN.bsn Jaeger Engineering FLYNN SHORT PLAT DR.AINAGS CALCULATIONS �LEVEL POOL ANALYSIS --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH INFLOW ST DI <-PEAK-> STOR.AGE <--------DESCRIPTION---------> (Cfs) (Cfs) id id <-STAGE> id VOL (Cf) ' ----------------------------------------------------------------------- ----------------------------------------------------------------------- 2 YEAR/ 2YEAR . . . . . . . . . . . . . . . . 0 . 12 0 . 75 1 1 165 . 46 11 3461 . 42 10 YEAR/ 10 YEAR . . . . . . . . . . . . . 0 . 33 1 . 28 1 1 166 . 50 12 4504 . 61 � �.��_�� Poo� �N�.��ss w�r�-c ��u�T �R�o2 � ( 3 ��ur�r �Nc��sE , File Basin Hydrograph Storage Discharge Level pool Jaeger Engineering 2eee�eeeeeeeeeee�e ; 3��e��eeeeeeeeeee��eeeeeeeeeeeeeee�eeeee�eeeeee��eeeeeee; ° ROUTING COMPARISON TABLE ° ° MATCH INFLOW STO DIS PEAK PEAK OUT ° ° DESCRIPTION PEAK PEAK No. No. STG OUT HYD ° , °______________________________________________________________________ ° °2 YEAR/ 2YEAR 0 . 12 0 . 75 2 1 164 . 94 0 . 11 11 ° °10 YEAR/ 10 YEAR 0 . 33 1 .28 2 1 166 . 09 0 . 27 12 ° °100 YBAR/100 YEAR 0 . 61 1 .91 2 1 167 . 63 0 . 44 13 ° 0 0 o _ o 0 0 0 0 0 0 0 0 0 0 0 0 ° ______====>Done<====_______= F10 to Exit ° ��e��eee�e�eeeeee��eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef There may not be enough memory to do large LPool routings Available Memory remaining: 27992 bytes Current Data Set Name: \FLYNN.bsn Jaeger Engineering FLYNN SHORT PLAT DR.AINAGF3 CALCULATIONS LEVEL POOL ANALYSIS WITH 130� STOR.AGE VOLUME --------------------------------------------------------------------- --------------------------------------------------------------------- , LEVEL POOL TABLE SUMMARY ' MATCH INFLOW ST DI <-PEAK-> STOR.AGE <--------pE�CRIPTION---------> (Cfs) (cfs) id id <-STAGE> id VOL (Cf) ----------------------------------------------------------------------- ----------------------------------------------------------------------- 2 YEAR/ 2YEAR . . . . . . . . . . . . . . . . 0 . 12 0 . 75 2 1 164 . 94 11 3826 . 05 10 YEAR/ 10 YLAR . . . . . . . . . . . . . 0 . 33 1 . 28 2 1 166 . 09 12 5319 . 94 100 YEAR/100 YEAR . . . . . . . . . . . . 0 . 61 1 . 91 2 1 167 . 63 13 7320 . 04 LEU��- P�o�- t�Nl��-`( SI S W�r�-t �tit c�r As� S�+R t� c-� p�n�l� I D� Y F.�2 STv(Z�1 . . Jaeger Engineering FLYNN SHORT PLAT DR.AINAGE CALCULATIONS WATER QUALITY HYDROGRAPH SUMMARY BASIN SUMMARY BASIN ID: C2 NAME: WATER QUALITY STORM, 6 MOS. SBUH METHODOLOGY TOTAL ARFsA. . . . . . . : 2 . 35 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . : : 0 . 67 inches AREA. . : 1 . 41 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 5 . 07 min IMPERVIOUS AREA 'ABSTR.ACTION COEFF: 0 .20 AREA. . : 0 . 94 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 70 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1140 TcReach - Channel L: 365 . 0 kc :42 . 00 s • . 1150 PEAK R.AT�S: 0 . 13 cfs OL: . c-ft TIME : 470 min 1�IET� �A��.T- Cf�LCS ( . 2 yr. ISo �Iuv�c�,f : Pz = 2 �� v� a.l�ou�, (� �no . � Tv�luv�a_t : 2,o = o ,(�7 � 3 Z . V o �u m�. c� �rr�, ; Q, D 4 �c- �l-. = I 7�-z F-�3 . = V o��. R�,r-e.�l 3 . �lo L �r� {'�v�dt.cd � L: So ' , W = zc�� , o�� ' Il�� , o ' - Ito� , 5' � I S ► ' vol , � so(z.c,� �• � � I � 5� I�r`� �� . . , �1�n , �r�, o�xe� = I % o� �- � 6��/ 1��2x' V i o us c�r'eo� � P e,+r k-.r CO . I��a..�� a,� �Y`nQe.rv . o.�-e-c�.� o ,�t 4 �4�- = 4c��r 4(o s� '�� a.x� t-,�� = 4c�r 4c� (.c�> = 409. � � c.'� c�-e.� �r�o v i cJ�-c� = �o(�co� = � 3 0 o sF q�.. VII. CONVEYAN.CE SYSTEM The piping was sized to accommodate the 100 year developed flows as identi�ed in this section of the report. The modified rational method was used as shown in the King County Drainage Manual. The pipes for this shorf plat are a minimum 12" diameter and all have a fairly steep slope. The 100 year storm flow for the entire site wos calculated. It was checked that each main pipe segment could handle the entire site's 100 year peak flow. __ VIII. EROSION CONTROL SYSTEM The erosion control system was designed to eliminate any onsite runoff ' from entering the adjacent properties or right-of-way. In order to accomplish this, an interceptor swale will be constructed along a portion south and west properfy lines. This swale will discharge into a sediment trap located in the southwest corner. The permanent detention vault will eventually be constructed at the location of the sediment trap. The trap , will have a discharge pipe that is connected to the drainage system that is within Sunset Blvd. NE. This will become the permanent discharge pipe. � Additionally, silt fencing will installed along a portion of the west and south property lines outside of the interceptor trench. These ore the downgradient property lines and is the most sensitive regarding neighboring lots. The proposed grading for this plat is well-defined and limited to the road and utility areas. The area disturbed will be minimized. The existing vegetation will be left on the ground as m�ch as possible during the site work. The erosion control plans also show the clearing limits and the locations I for rock pad construction access points. A tree plan has been prepared , for this site. 'I � � APp�oix l► CH�►FtT3, T�9LE9, GRAPH3 FRON KING COUNTY SWM liANUl�I, .a ,...�..�i.._ ._ - . , ,. . - - ....w . ,. .. , . �� ' ' '� I INO COUNTY. W.ASHINt3TON. SURFAC ,� WATER DES10N MANUAL t�:' — — II �` ap�a� ' Sectim�.S �iectlon 7.3.2 Runof'f Pu*mean Hrdrolo�ie Malyd• ' }1y6o�nph Mahod TABLE 3.S.2A 1�YDROLOCIC SOIL GROUP OF Tl1E SOILS IN K�NC COUNTY HY�ROLOGIC SOII GAOUP OF THE SOILS IN KING COUNTY I NYOROIOGIC HYOROIOGIC � SOII GiiOUP GROUP• SOIL GROUP GROUP• I ,�� C O�cas Peat O en-71r ts � Oridta O BeausRe C Ova►1 C I Beltin�ham 0 P�chuck C I 8�tsc,ot � Pu9et 0 BucWey 0 Puyatlup 8 Coastat 6eaches Variable RaQnar 6 j Earlmor�t SIt loam D Rento� U Ed9ewkk C Rtvervvash Variable Evefett __. A Salal . C I Indlanda A $ammamish O lasap , C Searoe o lOaus . C Shacar D Mbced Mwiaf land VarlaWe SI S�t C Ne�ton A Snohomish O Newberp • C Sultan C Nooksadc • C Tukwia 0 � Notmal Sandy l,aam � B/C Urban Va�ade WoodlmrMle D � HYOAOIOGIC SOIL GROUP Cl/1SSIFICJITIONS Il (law nx�oR potentlaf�. SoAs havinp h19h Int�tratlon rates, even wfien ttwrauqNy wetteA, erd cons�st�nq � chlelly d deep,we�-to-excess�vely dralned sands o�qravels. These sds have a hlph rate d vrrater lransmtssbn. 8. (Moderately low runoff potenttan. SoAs havin� moderale Inl�tratbn ratas when thorou9t�ty wetted, and ' eauslstinp chtefly d moderately 8ne to moderately coarse lextures. These sols have a moderato rate d water lransmisslon. C. (Mode�ately h19h runo(f potentiaJ). SoAs havinfl slow Inlllralbn ra�es when IhoroupNy wened, and consistiny chlelly d so13 with e layer that Impedes dowrtward movement d water, or sols wRh moderately , An�lo fine teztures. These sols have a slvw rate d water transmiubn. D. (Hiph runof!potenttal). SoAs havinq vAry slow Inlitratto� rates wt�n thorouqhty wettod and crns�stlny chk�y d day sots wlth e ht�h awel�lnq pdenttal, sols wMh � permanent hiqh water tabte, so wRh� hardpan or day layer et a near the surtace, and shanow sons ove� nea�y knpen�ous ma�er�al. These sons hsw a very stow rate d water trensm�ssbn. • F�om SCS. TR-SS, Second Editbn, June 1986. ExhibM A•1. „ --- -..-----�-- --— -�-------.. .------- -- -- ------- ------ ---�------------ ...�__ ---�-- � - s�u DRAFI' �..... . .,..— .. . - _....... – .,............_ » .. _ _... . `��:- ��' ING COUNTY� WASli1NGTON� SURFACE WATER DES [ GN MANUAL .�� '--''� � TABLE 3.S.2B SCS WESTERN WASHINGTON RUNOFF CURVE NURIDERS - � SCS WESTERN WIISHINGTON RUNOFF CURVE NUMBEFiS (Publlshed by SCS In 1982). . . Rtx�oH curve numbefs for setected aflrkultural, suburban and urban land use for Type IA talnlalf dlstributlon, 2�•hotx storm duratlo�. CURVE NUMBERS BY HYDROIOGIC SOIL GfiOUP ' IJWD USE QESCRIPTION A B C D � Cuttivated land(1): " winter condillon 86 91 S� 95 Mountal� open area�: low p►owlnq txush and �rasslands 74 82 89 92 Meado�w or pasture: 65 78 85 69 Wood or lorest Ittnd: undisiurbed �2 61 81 Wood or lorest land: youny second qrowth or brush 55 72 et 86 Orchard: wRh cover crop 81 88 94 Open spaces,lawns. parks, yd(courses, cemeteries, Iandscapiny. qood condRbtt: Qrass cover on 759G ��e�«a�� o � lak condltlon: grass cover on 5096 l0 7596 of the area 77 85 90 92 Gravet roads and parkt�q lots 76 85 89 91 OIR roads and parkiny lots 72 82 87 89 (mpervbus surfaces, paveme�t, roofs, elc. 98 99 98 98 Open waler bodles: lakes,wetlands. por►ds, etc. 100 100 100 Sir�qle Famiy ResideMial (2) Owellf� UnM/Grpss Ac.�e 96 Impervlous (3) - - 1.0 DU/GA IS Separate curve numbcr 1.5 �u/GA 2o shan be selccced � 2.0 OU/GA 25 lor pervbus and 2.5 DU/GA 30 Impervbus pohton , 9.0 ou/GA 34 0l tne ane or bas�� . . 3.5 OU/GA . 38 4.0 OU/GA • �2 ' 4.5 OU/GA� 48 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 bU/GA 54 � 7.0 OU/GA 56 � Planned unit developments, 96 impervious . condominlums, apartments, must be computed cOmmerclal busMess and kxlustrial areas. (1) For a more detaeed descript{o�d agricultural land use curve numbers reter to National Engineerinp Nandbook. Sectlon�1, Nydrdogy, Chapter 9, August 1972. (2� Assume�roof and drNeway n�noH Is dlrected Into street/storm system. 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