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Home My WebLink About03822 - Technical Information Report I ^ ' S628 Airport Way 5,Suite 144 lV � ' Seattle,WA 98706 lV P t2o614zo-»30 /y� F(206)457-4469 � tONSULTiNG plogconsulting.com ..� Survey-Civil-Structural 1 � 'G� �,� f� �,j3 c��1 � � �'�E�� = Highlands Park �hort �lat 6200 SE 2nd PI, Renton, Washington Storm Drainage Design Technical Information Report & Level 1 Analysis For: Vann Lanz 11610 80�h Ave N E Kirkland, WA MXP Project No. 12-024 , , _ . _ , . 3-1-2013 Ready for Submittal Q`n x'�� .:� �.,� 7-31-13 Revised per comments , �' w i s(� ' �; .t 1x 11-1-2Q13 Revised per Comments I, 'f+ �'•�,��trw�`�s'S�.�t;� �--_-.____-------�.�.___—___._�_�_� �_-'i ''CtSy�� "' � �" � s . ',`.U-.�v'�If i t�:�',�..��_ i`':1'��:t!T';:T.P�?`�. ,, ��1. 7� i � �'i�� ._�___�.��.� �„_—__—'—'_—'—____- '�.�._.—'--. L..-��-.-T-.-�..�-__.,._..,._-... ,.2 . ._n ._;ti`L � ..-. . : � : . ..1;`?`Si-1}:i .. Pre�?�e� �.,. ,,'rar�:,`�:.. �_,��: . . :. R@VISi011's; High�ands�3;ic 4t:o;-=�:I,:t-?IF, �.,•_;: , :_,� t, 2/20120�; 3822 5628 Airport Way 5,Suite 144 � ' Seattle,WA 98t08 P(206)420-7130 f(206)457-4-0b9 CA W S U L."�'1 N G plogconsuiting.com SUrvey-Civif-Structural Table of Contents Section 1 — Project Overview Section 2 —Conditions and Requirements Summary Section 3 —Off-site Analysis Section 4— Flow Control and Water Quality Facility Analysis and Design Section 5 — Conveyance System Analysis and Design Section 6 — Special Reports and Studies Section 7 — Other Permits Section 8 — ESC Analysis and Design Section 9 — Bond Quantities Section 10 — Operations and Maintenance Manual Figure 1 TIR Worksheet Figure 2 Vicinity Map Figure 3 NRCS Soils Map Figure 4 Existing Site Conditions Figure 5 Developed Site Conditians Figure 6 Contributing Basin Map & Existing Conditoons Highlands Park Snort Plat—TIR Page 2 of 16 2/20/2015 r � GOfdSUl.TiNG FIGURE 1 -TECHNICAL INFORMATION REPORT TIR WORKSNEET � . � � � � � ' 1 ' 1 1 Proizct U��n�r: Vann Lanz �� Proje�t'�.ainc: 13ighland�Park Shurt Plat Address 4118 96'"Ave SE,Ivlercer[sland,W.4 98040 Location: 6200 SE Z°�Pl,Renton,WA ContactTelephone 206-499-1277 � Township:23N Project Engineer:�iark X.Plog, PE i Range:05E i Section: NW'/a '4 � Suhdivision � DFW FIP:1 � Shor�line M.u�a,<_�'mc.��t � Short Plat r COE 404 r Rockery � Grading � DOE Dam Safety r Stnictural Vauks �Cocmixrcial r FE1�fA Floodplam r Other � Other � COE Wetlands 1 1 . Communtitv Renton Draina e Basin Lower Cedar River � River r Floudplain r Stream r �V`etlands Cateeon II buffer r Critical Stream Reach r Sec�}�s.-Sprines y r Depressions.5wales [� HigU Ground�-ater Table r Lake ------- r Ground�ata Recharge � Steep Slopes � Otlier Soil Type Slopes Erosion Pntential Erosi�c�'elocities Aldenvood 6-li 4�� Slight � FPS � Additional Sheets.Attachad Highlands Park Short Plat-TIR Page 3 of 16 2/20/2015 ' i c��asv�.r��v� FIGURE 1 -TECHNICAL INFORMATION REPORT (TIR) WORKSHEET � REFEREI�CE LIMITATI0I�SITE COI��TRAIi��I' � �Downstream Anal sis �' � Additional Sheets Attached � �SIT�I�iL`M ESC REQUIRE'�1E\TS �1IhI1iL�4 ESC RF,QL:IRr:�lEI�TS DURII�G CONSTRUCTIO?� AFTER COnSTKLCTIOI� � Sedunentation Facilities � Stabilize Fa�osad Surfacz r Stabilized Construction Fa�trancz � Remove and Restore T�nporary ESC Facilities �Paimeter RunofFControl � Clean and Remove All Silt&Debris �Clearing&Grading Restrictions � Faisure Opzration of Pem�az�ent Facilities � Cover Practices r Flag Limits of S.AO and Open Space Preservation Areas r Construction Sequence � Other r Other � Grass Linu3 Cha�uiel � Taik � Infiltmtion \-lethod of Analysis � � Pipe SVstc�n r Vault � Depression r Open Channel �EnerQy Dissipater � Flow Dispc3sal KCRTS � Drv Pond r Wetlazxl r �'�'aiver r Wet Pond � Strc�m � Keeioual Be[ention Brief Description of System Operation: Surface flow will be collected in a series of catch basins in the right of way and pipe then conveyed to an existing downstream system.A detention pipe is provided for flow control. Faciliri-Related Site Limitations Reference Faci�ity Limitation r Cast u�Place��ault � Drainage F.��nent � Retau�ing Wall � .Access Eas�ixnt �Rockery>4'Hi� ��Native Crrow�th Protection Faseii�ent '� Stnu-tural on Steep Slope r Tract r Retaining��'all �Other [or a c:vi;engineer under mr s:pervi�ion have visitzd the site. actual�ite conditions as obszrved were incor�orated:nto this u�orksheet and the attachments. "io the best of my�kno�i�ledge the information procided here is accurate. Si ned,�Date Highlands Park Short Plat—TIR Page 4 of 16 2/20/2015 ' i canisu�T��u� Sectian 1 —Project Overview The Highlands Park Short Plat consists of subdi�iding one single family lot into three single-family lots all with direct access onto SE 2nd PI. The existing parcel (#142305-9117) is approximately 43,118 square feet(0.989 acres) in size and contains an existing house and driveway all of which will remain. Please refer to Figure 4, Existing Conditions. The site is considered rolling with relatively gentle slopes (less than 15%). The parcel is zoned R4 {4du/ac) and is located in the NW Quarter of Section 14, Township 23 N, Range 5 E, W.M. King County,Washington. The project site is shown in the vicinity map below. F 4� Q � r iT.^. � tVE 1st St r�ir tst 5: N s n `Oi m ,:; ,;: * _ >_. � � —� tA �� !r� Tyi R,t'a^ 3 w SE:nd St SE 2rad Si D .. t �: � � F.:� �M T 3 j ,�� C a a � Pr�i�c� Site {=�_ =-� �;�; SE 2hd Pf �c 2n4 PI �2nd R! �'� 3 L� � � � � < c 6 S IYe 4� � -_ .. �. � d�` a � � g..� se i 3�,t,s. �' � � r� s _ � � ,� � �n A . �A ... � . 1��5_ � at,;E � �� SE 137+,�P; SE 3rd Pt U• r� � Figure 2 —Vicinity �11�p Highlands Park Short Plat—TIR Page 5 of 16 2/20201 5 ' i co�vsue.�rrni� The Existing soils on the site are mapped by the NRCS as being type AgC—Alderwood Gra�elly Sandy Loam. Please refer to Figure 3, NRCS Soils Map below. The Hydrologic Group of AgC is Till for surfacewater modeling purposes. �"`�;' �� i � �'s– — – � ' �:. � _ _ �� 'r.:�i ��- �'+��C'� �'s!$E.' �� : �.` �: � 'I � �.��e.�'�,'� I �a^ y. .� _ '� � ��,� � � `¢ � � � � ��= � �.� • �t� .� -.:s r�, .. �c �� , sti� ks �j�' - a �t`" ,t. ^� y, ;". _ .,. . . . .', ,_� '".t`"1"' .. .- ^�'k '�$':^. - . -,r:�Y„ . � .xw �`;�ro 5.?-� .- � � �` - -- — � �—:- ' �� , � �'� � ,, � � ..��r s.. . �, �_ �° �., � n � :�*�'�i�.. :i "` - 'fi ��. ,�. /$ � �a .- 9'` �: " - ;�µ, �#'' :f; ,�;- S`�.. - �fi ' .'�'Y�" �' ..A � �$ I�I�;� 5t'� �ry� a- .�'�4 > �!';ww�49i a"# 'd �` .��§* ��,�,.. �t+ �a * 'f. . . '� k� �,� �-� ` � - ,�t �yr ' . ,r� �u � r� i , � ,.,r � '..� ..,� i�; � .. a '� `' ^�Y3� K. } � 'N :b ' ' p.:.� y'_i .Ar _ -_ i-k;-� �...� . -. , � .�. ' _'� Figure 3— NRCS Soil Map Section 2 —Conditions and Requirements Summary The following summary describes how this project will meet the eight"Core Requirements°and the 'Special Requirements°that apply: Core Requirements �. Discharge at the natural location: This site currently sheet flows to the south and collects in a roadside ditch. From this ditch, surtace water is conveyed to the west and into a tightline conveyance system. The proposed drainage system for this project will continue to collect surface flow and then convey it in a new piped system and discharge to the same location. Discharge is proposed at the natural location. 2. Off-site Analysis: A Level 1 off-site analysis was completed for this project and is included in Section 3 of this Technical Information Report. No significant dovvnstream drainage problems were found. Highlands Park Short Plat–TIR Page 6 of 16 I� 220/2015 � r , tc�n�su�.Y�ni� 3. Flow control: This site is in a Flow Control Duration Standard Area (forested conditions). Flow control BMP's per Appendix C will be pro�ided. Limited infiltration will be provided for all new impervious surfaces on the project site. Overflows from the infiltration will be connected to the street conveyance system. 4. Conveyance system: Flows will be conveyed using catch basins and tight line culverts. 5. Erosion and sedimentation control:A Temporary Erosion and Sedimentation Control plan, notes and details are included in this engineering submittal. 6. Maintenance and Operations: The smaller diameter storm drainage collection system to be installed on the proposed lots will be privately owned and maintained. The remainder of the stormwater collection, conveyance and treatment facilities will be owned and operated by the City of Renton. Special maintenance and operation is not required. 7. Financial guarantees and liability: The owneNcontractor will be required to post construction ', perFormance and one year maintenance bonds for the proposed roadway and utility work associated ' with this short plat. A bond quantities spreadsheet for the proposed development will be prepared as required upon Renton approval of the engineering plans for construction. 8. Water Quality: The new impervious surface subject to vehicular traffic(PGIS) is less than 5,000 square feet for this project. As a result,the project will not be providing water quality treatment. Special Requirements 1. Other adopted area-specific requirements: Not applicable. 2. Floodplain/Floodway delineation: Not applicable. 3. Flood protection facilities: Not applicable. 4. Source controls: Not applicable. 5. Oil Control: Not applicable. 6. Aquifer Protection Area: Not applicable. Highlands Park Short Plat—TIR Page 7 of 16 2/20/2015 ' i CONSU�TING Section 3 — Off-site Analysis This Level 1 Downstream Analysis is submitted as required by Core Requirement#2, Section 1.2.2, of the 2009 KCSWDM and Renton SWDM. Core Requirement#2 requires a qualitative analysis of upstream and downstream drainage conditions with an initial project submittal. Task 1: Studv Area Definition and Maps: See Section-1 Proiect Overview of this report for a detailed Study Area Definition. Task 2: Resource Review: A sensitive areas review shows no critical areas on or near the project site. There were a few official drainage complaint records on file with King County. None of the complaints within '/4 mile of the property were downstream from the subject property. Below is a map depicting Drainage Complaints within'/< mile property. l�� _ {g t , li4 Mile Area � Y� � .' f \( � \.�. Y .. �,� .. '� ` r„t 3 .fy � .� i a "L"r at :��a*:o' _ .. �} 3`',t 7.L<].A ., .: Gf �a8.5� �� :� -�� . � /.«.� T :'E 4�. �W i� t J�(i.kk?. +,b,�..rf k :'.�i* ��,t;�� . . .. ....... :�� . . � f�:' :I �^�� `'.. � ; `'fif�"�"�. r M . . . .;i ''+ `.� >.r t :� �, ,p� ., ir � �� '�.r y r y -� 'r '' `r_; .._. . i�� ... e..; '�� S.�` 't� �' a� i ti a 'r ��' __ " " _ _ . . � . ,,a `�-"`-t' `�,, .:� #? i: f .�J �f > ,{+ = s �' �'? .. . .. � � .�� ., . � � . � �� s y�.�-�' " ,.��.,� s ...dt -'t a� a�t�.'�2f'"`��.i..'�:�� r �Mt fi.. a:S'£�Ytt's '� , +Jc'ti0y tKc�,>�4:'�_aA'.s,�r - . f � ky`,, `' RF F`fr'�5t �'v'�'` Y �',�'� �.��4'�'^�u� 9 .uS�i.� �1 � ). �.�K.'°£t �r -,._ ,�^ ..x j'�GT .�'`t''"�"'` '�'u.�"kF.. x.: µ t �.�`' ��'��f i>��,. S"�,' ��rt+.� �r`�Y '� ;� �'� ,{;, :: r r 'ia r� �� ' t: �ti ul�?i ,:t� � �,> � °�.i�.,ax��"t. . . �7' Y �< �f M� _�.+.a a'�•�p 1 � ,6.. ,y„d .� ' t.�� t� � , �r1x ,,'�+., c^ �r3 .�< k, f ._ p t}� . '�; .. . � 1� � t =. 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Complamt is�]}}��.�� . . _ .. .o-vt a t;d f� .^Vi'a le�r � : - . 1 � � ;x .:� °�.,� . ��hs0. `-�; �s-.:� r si� r. � �. .. �� ::'- � ' . -i!t _. .}n:��R"A�.��n�' a.l�'t . -� . . '�'!^.:� _�..'.. . .� -....... .. ... T.f H_� ,� , .. ':. . ..� �. . . ' Highlands Park Short Plat-TIR Page 8 of 16 2/20/2015 ' i COM5ULTtNG The other drainage complaints within'/ mile were not in the drainage path or were upstream of the facility with no downstream impact. Task 3: Field lnspection: A field observation of the site and Y4 mile downstream analysis were performed on March 11, 2011. The weather was overcast. Field observations are noted under Task 4. Task 4: Drainaqe Svstem Description anci Problem Descriptions: Upstream: There are no upstream drainage conditions, because all surrounding subdivisions have been graded to drain away from the site or the discharge from those developments is conveyed via tight line around this site. The undeveloped property to the east possibly discharges some sheet flow towards this site at the northeast corner but the flow path is heavily vegetated and there was no evidence of any flow. Downstream: The downstream drainage system is shown in the following photos and descriptions: E ,� �, • - r�- � � � �� "��;�.� �� ?��'� �'�' �;'+ `°�' - � �' '�`,, �`��`� �py�_,�, > � �!� f� � � K �� Y�v'iF , � �� - .f �u'_,�4qyT�- �'FE�,y � �,�{� � _ _ �.4�tl1� P„� "�"'_"t' �� "- �:. .+..t -��:� ' �hr?n KF`. - 2r.a- .��„� { '�'s i�g.'- ��"�- . �f .�� :� � s s" ��t �� '��I �. '� � ,; 7��'�c _ - �' ,.t�.. .-k - �� .�� t S �, `..� � �� '� 9 , a ' _ t �i �� ya g � y ��., �_ ��: � � � ' #` ` �� , l� '�R � k E'� _ ? ,Ai: � �� ( ' �A1"�. 1�� `�?-. t f'Y' � 3 ti� t�§ .Mi �..� � ��. .� ,l�.. :- ; . - i� �3 .�,`��, ' � � �: ��k vt t'° '�.a, �.�^t�,o- �;.a� Y �� . �� ;Y�. "� ��fs �N„ �� .. � x � z ,� �� „ T � c�r` A ' `� ��r. 7 �+".,�q� � _)c�n I �� n� aYr � � � >.. ��,�wr,� �u .__ .it�r Ir.. s �� . �� r� � ,� � -� � �: - �� ;,� :U-: -:�" ;4 — �.. W a�,�.t�., ': ��x`�:�-,,��:�,�. �. ;�� F �'`�4�� wt. �r�aq'�e, , u. iffw� � �r��. s. �„ � t �� u z � `�'g��- 8 � - � i. � � ,,,�� ,:aFG" ��q1� 3 1 .... �s�FJ+c3:,��., � aY,a, 4 � L ^ I � �I � � 'A N.Y S�d��:'h,. S�. Yd '�..�"°'k ��y it�i I i I I .y�� 3 iS:. � ii1�;G3.,r'�V� 1 = �� a $�S�� Y` 9 �� C3t 6 �, � ��,� �'= �o'�� .�? � �g , . � � '�� .eEx: ��. � ��-..:urcd,. �;� '�. �. : � � �. �: �. � � �� . , ��. .� �� F !. � .. � _. .. � Yp.fi! y�.�y ,�'9��1tl��G":��G.' W �� Solid lines indicate � � . ��"��`�� .,� '�� ;onveyance syster� �°r, �$�¢��:;, '�� .. *�. :;a ; `Ir,.v �� AZ°&��'�`I��;.. Y{ �� r`��u'S�a h st+c '.o �� "�� ' � .�. �.$ : �..� � .�� t t Mati.-. i� y?�. ��i �T`►f�[c#y�� }�yip��€� . vr; .,�dSN"'�yW ��'`t��` �� J�t�ie �bb 4��1i> �?�' Gt3a�.A�l:��Ts�c � ��j . Y.�r��`_��'Rw':��e��b:�v...i-a. .. Highlands Park Short Plat—TIR Page 9 of 16 2/20/207 S � � CONSULTfNG Photo Photo Description # Open ditch �r�' Runoff from project site sheet flows to �: �� ? �, ,; the south and enters an open ditch & �` �r` ::�'"`. .:F�-.��" with 12°ductile iron culverts under � the driveway. Looking east at the project site. Onsite � _ �.<. � � , � w, , � ,�T�.. . - _.a-. i ) � � �FG=:h ♦T`y'�- .. �., '�'.�,�'! W 4ta'.'s''7b�P'., �,� � i r:�f�.`_ :�tQ ... • . �� Tr;�h rack � �: �,_ �� y.Y.1F..=_ . 3 "iQ i y�y�.,�.'..' , ,`+�5 '3,5��.4�� . irj�Y- �:�'�`r'�= �� ? Ditch flow enters the tightline system. "�t �� . = 4 �� 2 ��.. � - ' , �#�. ; t Looking west. � r� � �:, � �'�i�. �� r. ;.:�� :s ��,� � ' Onsite � �t �,n, ��'"r`� �' xe`� .�� s �� / ��"�` s,µ,�s�up �'�'��,��,� ��. � A ' �`�-"� "a� � `� s�'r ti��,,� `;° �. � ,;,y�� ' ` .�"�'''� ��`` �a' ' 4 . '`f. :. �k� �7 . � � .. x .,�, �:n. � � ��d� �' '¢�., 4 ��Y�,,,, . h I, II I � I Highlands Park Short Plat—TIR Page 10 of 16 2/20/2015 � , t011i5UL71NG � g ,�r � . � ��r, { �;� �t s, ��: �, � � � `�"> `� �,'��'�� '. t ' Detention pond � � r di�chare: � �r,' '� ,� -��' �i ,f -�,��"�` x „��; , Y "�'�;.�;, �� . !� , . k, n'�s�i( .. i }t �" � � :�� " ;� }� .:; , r�n``� r The tightline picks up the discharge , �'� flow from the Highlands plat. 3 �� - �' ; � � � � `� � ��'f 100 feet downstream. � 4,,: Jy �}t' ��.. �1 I �� 1- ' ; � _ ��'. T�q,� IJIII �. •��'� �.. A�'�k � �� , ,�-.�� ;. F �k �` �f+�� 3 z�.�:,�y,'�Td;�-- _��"ti - �#, ��,� The conveyance continues to a catch � �:, �'* � ��. � ,�� ., basin in 152"d A�e SE where it tums 4 ' ��..� south. � b � _, '„��, �:� �a :��`$�a�',�� ? This hoto is taken lookin east about y � ,f.. Q�,� � ,, ` P 9 r 250 feet west of the subject property. ; �;;,..,�.:;:_` Highlands Park Short Plat-TIR Page 11 of 16 2l20/2015 r i con�su�.�r�ru� � Y;. ;t y:�; r� The flow is conveyed south where it .� ,Y�:,�-§. _ outFalls to the park property. Conveyance flows south 5 and discharges just beyond This photo is taken looking south this brush. about 300 feet west of the subject property. ,i � f Flow is not verv channelized and ' �;.., - ,,;�,z. no sienificant erosion�vas noted. �.<,� .�� ' - 3 h � �`� � �� . � �� '�""��h ' This photo is taken looking North 6 about 800 feet south west of the � . `"� ; .d � ! subject property. , � d +�� -C�,.��r c�;+,^�� s �r �; �' E i � yk'_# f k ti� f� �,�; �' � :e a , . ., I � �.+�:� ¢� '�'.< `S s �� ;� . s `." "� �' ��"',� �� •� ��. � `� t_� �Ty..�� 'Y� �. �� .. 'r��.F�aa..�h� C. � � ��' '� y"��ry4� ' ` . a� . . „�,� ��-i _ F '� #3�" � �s,�.-� L �' ro4",�3�Y� { ,_�� ,.E 5 �� ..� y ,. ^it. � �Y �� : Y � , t.� � 'Lc �-i �.� ,,.-� �} i .�y��_ t y�� . �� °`� �� .,�� °� '`�:,��.�"6�' ,Q`' � The flow continues through the park � � ,� y� � property in a very shallow ditch that ;� �� '�^��-�'` often fans out into the surrounding 7 �,� ` ;'�a ��'�,�� brush. I! `� �1` �. ,x "' This picture was taken about 1/8 of a ' �� ' ,� -� mile from the subject property. �' �` Y ` �� a � x� � � � ` �` �°`� � �. � �e � ��1 �,,; s �``�-d. ��,�. Highlands Park Short Plat-TIR Page 12 of 16 2/20/2015 ! , conisu�r��v� ' r F �r 'I ��hl �� .�( � �e "` � At'/4 mile downstream the surFace � ; �;��.�r` flow re-enters a conveyance system -- • I at 148`h PI SE where it continues to �, ' the south. This photo was taken '/<mile from the � property looking south. =;t _ :; �r � ', The trash rack an headwall are clear ��*�';_ �'° 1 � ', and well maintained with no signs of -��;;�, . � �r-�-�. ' ` ��`� } ' overtopping or blockage. � .�� "��v = � ,��: ,�._ � T,a>h r::ck �� . ,.' '�,�'-'�" '` a :.- �i ""� 't�;� 4r �.'; ' ' :,�-�. �-. _-� � 8 �� , - . # � � '. � �',�,r ,�- i z�" �^. �.�, � ` ; �' Y:� I} � t Z�r �. _ ��`��'' The drainage path, as described and photographed, appears to have adequate capacity and no current problems were observed during our field investigation. Task 5— Mitigation of Existing or Potential Problems: None required. Highlands Park Short Plat—TIR Page 13 of 16 zizoizoi s ' i G C3 NS U LT!!V G Section 4— Proposed Site Conditions and Design Parameters �, Flow Control Anatysis and Design 'i Based on the City's flow control map, this site falls within the Flow Control Duration Standard, Forested ' Conditions. This project consists of a Parcel Redevelopment project. Offsite(roadway)Areas The proposed redevelopment of the roadway includes the following target surfaces: 1,160 SF (0.02 acres)of New Impervious Total Offsite Area: 1,160 SF(0.02 acres) Parcel (onsite)Areas The developed site conditions include the two new lots with an assumed impervious coverage(55%) based on the allowable coverage per the zoning. Lots: Lot 1: 0.55 x 10,998 SF=6,049 SF(Restrict to 3,100 s� Lot 2: 0.55 x 11,OQ0 SF= 6,050 SF (Restrict to 3,1a0 s� Parcel Totals Impervious: 6,20Q SF(0.14 Acres) Pervious: 15,798 SF(0.37 Acres) Total: 21,998 SF (0.51 Acres) Parcel Modeling Totals: Impervious: 3,850 SF(0.07 Acres)—using 50% sizing credit for limited infiltration BMP Pervious: 18,148 SF{0.44 Acres) �, Total: 21,998 SF (0.51 Acres) Project Totals Impervious: 0.09 acres Pervious: 0.44 acres TOTAL: 0.53 acres Pre-developed condition , F=ow Frequency Ana�-ys-s i--1e Series F_le:hig�n?x.t;f ?roje�t Loca�_c�:Sea-I'ac ---Annual Peak Flcw Ra�es--- -----Flow Frecuen�y Ana=ysis----- �'1ow Ra�e Zank I'irie of Peak - - Peaks - - Rank Return Prcb (CF4) (CF5) ?er'_od O.u3� 2 2/oal��1 15:00 0.044 1 100.00 ��.990 0.010 7 1/OE/��2 3:00 0.035 2 2�.��0 ��.960 0.026 4 2/28/��3 3:0�� a.027 3 10.00 0.9��0 0.00_ 8 3i2�/Q4 =9:0�� a.026 � �.00 0.8��0 0.0_5 6 -i05i0� 8:0�� .022 � 3.00 0.66? 0.027 3 _/19/06 20:0�� 0.a15 b 2.00 0.��0 ' (�.�LL rJ 1_�2'��E 4:�'1 17.1�1� 7 1.31� �.ZJ� � 0.044 _ _i09/08 9:00 0.��01 8 l.l�� 0.091 �o:-iputed Peaks O.Q41 50.00 0.980 Highlands Park Short Plat-TIR Page 14 of 16 , 2/20/201 S ! � +COlUSUL.TIIVG Developed condition F-ow Freauen�v ti�alvs-s 7_�n� Series F=1e:n'ghpr.tst ?roje�t Locat_on:Sea-'='a� ---Annual Pea:{ Flow Ra�es--- ----F1c:�.� Freque�cy A7alysis------ Flow Rate 3an:t Time of Pea:t - - Peaks - - �azk Re�urn ?reb (CFS) (�FS) P2r_od 0.06� � 2i 0?i Ql 2:0�� 0.144 - =�7�7.00 0.990 p_��cc '7 _;0�/��2 :6:0�� O.Q8= 2 2�.00 0.960 0.081 2 2i27�03 ?:OQ 0.068 3 "_Q.00 o.aoo 0.��36 8 8/26i0� 2:00 0.066 4 �.OQ 0.800 0.��6 6 1'J/2H�O� -S:O�� 0.0�4 5 3.00 0.667 O.��e8 3 -/18/06 _6:00 0.��5 6 2.00 0.�00 0.06� 5 1_/24i 06 3:0�� 0.��4 7 _.30 0.23- 0._c4 _ =/09/08 6:00 0.��36 fi _.10 0.09- Compu�ed Peaks 0."�23 5��.00 0.980 The net increase in the 100yr runoff flow from the predeveloped to developed condition is 0.144 CF-0.044 CFS= 0.1 CFS. Based on these figures this portion of the project meets the requirements for exemption under the City of Renton 2009 Surface Water Design Manual Amendment Section 1.2.3.1 (B)on page 1-35. Water Quality Analysis and Design New PGIS is 4,225 SF <5,a00 SF. Water quality facilities are not required. Section 5- Conveyance �ystem Analysis and Design This project provides a single conveyance pipe to replace an existing roadside ditch. This ditch serves the 4 properties north of the road that include the subject property and three lots to the east. The drainage basin including the adjacent roadway totals 4.3 acres. Utilizing this area and using a conservative 50% impervious coverage the 25 year storm flow to this ditch and the new culvert are calculated using KCRTS as follows: F=o�a Freq�er_c. Fna=_+sis Time Ser`_es F=12:=arzc�nvevance.tsf Project ��cat_or:Sea-Tac --Arr�a_ Peak F1ow Rates--- ----?_�c,� Frequer.cy Aralysis------ Flc�a Rate ?.ank Ti'ne of Peak - - F'e7k� - - Ra�k Returr Frob (CFS� (C,Sj Per-oc D.713 . 2;`C9;'Ol :�C _. _, 1 1CD.00 0.99D 0.55? 8 _(C5/02 lE:^vG �.Sn3 � ZS.00 0.960 0.863 � 2%2%/03 7:��C �.336 .i lO.00 0.9D0 0.576 � 8i26/04 2:OC ,.755 9 S.00 0.8D0 0.700 � 10%23/04 16:DC ��.713 5 3.00 0.66% 0.755 4 _%13/06 16:DC ��.7C� 6 2.00 0.5•��0 C.836 3 10/26/06 0:00 �.5%6 =.3D 0.�3_ _.9% 1 _%09/02 6:��0 0.55% g _.10 0.�9" The proposed pipe is a 12"CPEP @ 2% Using the nomograph on page 4-22 (Figure 4.2.1.F)of KCSWDM this pipe can easily convey 2.75 CFS which is greater than the 0.86 CFS design flow. Highlands Park Short Plat-TIR Page 15 of 16 2/20/2015 � � COM5UL7tNG Section 6 — Special Reports and Studies We are not aware of any Special Reports or Studies associated with the property proposed to be subdivided or in the near vicinity. Section 7—Other Permits None Section 8 — ESC Analysis and Design Per section D.3.3 of the KCSWDM on a site with slopes of 10%or less and flow paths that do not exceed 250 feet, perimeter protection may be used as the primary treatment. This site meets that criteria and no further analysis or design is required. Section 9 — Financial Guarantees See the attached Bond Quantity Worksheet for this project. Section 10 —Operations and Maintenance Manual The individual dry well BMP's will be maintained by the individual lot owners. The maintenance of the dry wells shall be in accordance with the following: Your property contains a stormwater management flow control BMP (best management practice}called "limited infiltration,"which was installsd to mitigate the stormwater quantity and quality impacts of some or all of the impervious surfaces on your property. Limited infiltration is a method of soaking runoff from impervious area (such as paved areas and roofs) into the ground. Infiltration devices, such as gravel filled trenches, drywells, and ground surface depressions,facilitate this process by putting runoff in direct contact with the soil and holding the runoff long enough to soak most of it into the ground. To be successful, the soil condition around the infiltration device must be able to soak water into the ground for a reasonable number of years. The infiltration devices used on your property include dry wells as indicated on the flow control BMP site plan. The size, placement, and composition of these devices as depicted by the flow control BMP site plan and design details must be maintained and may not be changed without written approval either from the King County Water and Land Resources Division or through a future development permit from King County. Infiltration devices must be inspected annually and after major storm events to ident'rfy and repair any physical defects. Maintenance and operation of the system should focus on ensuring the system's viability by preventing � sediment-laden flows from entering the device. Excessive sedimentation will result in a plugged or non- functioning facility. If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly basis or more frequently if necessary. Prolonged ponding around or atop a device may indicate a plugged facility. If the device becomes plugged, it must be replaced. Keeping the areas that drain to infiltration devices well swept and clean will enhance the longevity of these devices. For roofs, frequent cleaning of gutters will reduce sediment loads to these devices. Lots 1 &2 of this short plat are restricted to 3,100 SF of new impervious area. Highlands Park Short Plat—TIR Page 16 of 16 2/20/2015 � —' s��lj��ffl�'`� RECORDING REQUESTED BY AND WHEN RECORDED MAIL TO: CITY CLERK'S OFFICE CITY OF RENTOAI 1055 SOUTH GRADY WAY RENTON WA 98057 DECLARATION OF CUVENANT '� FOR MAINTENANCE AND INSPECTION QF FLOW C4NTROL BMPS I Grantor: Grantee: City of Renton Legal Description: Additional Legal(s)on: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton(check one of the fotlowing)0 residential building permit,0 comrnercial building permit, 0 clearing and grading permit,❑ subdivision permit,or 0 sl�ort subdivision permit for Application File No. LUA/SWP relating to the rea!praperty("Property")described above,the Grantor{s),the owrter(s}in fee of that Propei�ty,hereby covenants(covenant}with City or Renton,a political subdivision of t}�e state of Washington,that helshe(they}wil] observe,cansent tq and abide by the conditions and obligations set farth and described in Paragraphs 1 through 8 below with regard to the Property. Grantar(s)liereby grants(grant), covenants(co�enant),and agrees(agree)as follows: I. Grantar{s)or his/her{iheir)successors in interest and assigns("Owners"}shall retain,uphold, and protect tiie stormwater management devices,features,pathways, limits,and restrictions,known as flow contro[best management practices{"BMPs"),shown on ti�e approved Flow Cantrol BMP Site Plan for tl�e Property attaclied hereto and incorparated herein as Exhibit A. 2. The Owners shall at their own cost,operate,maintain,and keep in good repair,the Property's BMPs as described in the approved design and Maintenance Details for eacl�BMP at#ached hereto and incorporated herein as Ext�ibit B. 3. City or Renton shall provide at ieast 30 days tivrittett notice to tlte Owners tl�at entry on the Property is planned E'or d�e inspection of the BMPs. After ti�e 30 days,the Owners shall allaw the City of Renion to enter for the so(e purpose of inspecting the BMPs. In lieu of inspection by the Caty,the Owners may elect to engage a licensed civsi engineer registered in tlie state of Washington wha has expertise in drainage to inspect tlSe BMPs and provide a written report describing their coi�dition. If the engineer option is chosen,the O�vners shall provide written notice to the City of Renton tivithin fifteen days of receiving the City's notice of inspection. Within 3Q days of giving this notice,the�wners,or the I engineer on behalf of t1�e Owners,stiail provide tlie engineer's report to the City of Renton. If the report is not provided in a timely manner as sgecified above,the County may inspect the BMPs witliout furtl�er notice. 4. If the City determines from its inspection,or from an engineer's report provided in accordance «rith Paragrapli 3,t}�at maintenance,repair,restoration,andlor mi#igation wvrk is required for d�e BMPs, The City s3�all notify the Owners of the specific maintettance,repeir,restoration,andlor mitigation work (Woi-k)required under RMC 4-6-430. "1'f3e City shail also set a reasonable deadline for completing t13e Work or providing an engineer's report ihat verifes completion of Ehe Work. After tlre deadline has passed,the tJwners shall allow the Cify access to re-inspect the BMPs unless an engineer's report has been provided verifying completion of tiie Work. If tlie�vark is not completed propecly within the tiine frame set by die City,tlie City may initiate an enforcement action. Faitcare to proper(y mai��tain tl�e BMPs is a violation of RMC 4-6-030 and may subject the�wners to enforcement under tiie RMC f-3, including fines and penalEies. 5. Apa�t f:om performing routine la«dscape maintenance,the Owners are hereby required to obta'sn written approval from the City or Renton before performing any alteratians or modif cations to tl�e BMPs. 6. Any notice or approval required to be given by o�e party to tlie other under the provisions of this Declaration of Covenant st�all be effective upon personal delivery to the otl�er garEy,or a#ter three�3} days from tlie date t6at the notice or appro�af is mailed witli delivery confirmation to the current address on record witl�each Party. Tl�e pat-ties shall notify each ather of any change to their addresses. 7. This Declaration of Covenant is intended to promote the efficient and effective management af surface water drainage on the Praperty,and it shall inure to the beneCt of a[1 tl�e citizens of the City of Renton and its successors and assigns. Ttiis Declaration of Covenant shall run with the land and be binding upan Grantor{s},and Grantor's{s')sueeessors in interest and assigns. 8. This Declaration of Covenant rnay be teiminated by executian of a tvritten agreemant by tl3e Qwners and the City of Renton that is recorded by King County in its real groperty recards. iN WITNESS WHEREOF,this Dec[aration of Covenant for the Maintenance and lnspectivn of Flow Control BMPs is executed this day of ,20 GRAN?OR,owner of the Property GRANTOR,owner of the ProFerty STATE OF WASHINGTON } COUNTY OF KING )ss. On this day personaily appeared before me: ,to me known ta be Ehe individual(s)described in and�vho executed tfie within and foregoing instrument and acknowledged that tliey signed the snrne as their free and voluntary act and deed,for the uses and purposes dierein stated. Given under my hand and offcial seal this day of ,2� Printed name Notary PubIic in and for the StaEe of Washington, residing at My appointment expires � ' EXHIBIT A — DRY WELL MAINTENANCE INSTRUCTIONS Your property contains a stormwater management flow control BMP (best management practice) called "limited infiltration," which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious surfaces on your property. Limited infiltration is a method of soaking runoff from impervious area (such as paved areas and roofs) into the ground. Infiltration devices, such as gravel filled trenches, drywells, and ground surface depressions, facilitate this process by putting runoff in direct contact with the soil and holding the runoff long enough to soak most of it into the ground. To be successful, the soil condition around the infiltration device must be able to soak water into the ground for a reasonable number of years. The infiltration devices used on your property include dry wells as indicated on the flow control BMP site plan. The size, placement, and composition of these devices as depicted by the flow control BMP site plan and design details must be maintained and may not be changed without written approval either from the King County Water and Land Resources Division or through a future development permit from King County. Infiltration devices must be inspected annually and after major storm events to identify and repair any physical defects. Maintenance and operation of the system should focus on ensuring the system's viability by preventing sediment-laden flows from entering the device. Excessive sedimentation will result in a plugged or non-functioning facility. If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly basis or more frequently if necessary. Prolonged ponding around or atop a device may indicate a plugged facility. If the device becomes plugged, it must be replaced. Keeping the areas that drain to infiltration devices well swept and clean will enhance the longevity of these devices. For roofs, frequent cleaning of gutters will reduce sediment loads to these devices. Lots 1 & 2 of this short plat are restricted to 3,100 SF of new impervious area. i 1 ' . . � . . � ..�: � . . � .. . ..�.._ _ � . .. ... � N88'0�'33'iY 274.25 . � . . . , .. . .. ... . .,,.... .�..:: .. ... ....v' ��!.. ,� . �r:�.:. -..,.,..I .. ��: . �a.�»�� ..:,, ,., . „ `,. -,. AN � y 4�.5^i .. �..� f. � �C � -__..... . .. �..--5 __... ._"'.___........__..� ..._ � '�� . R l5'49Bi. -� ..._.. � � . ' t . i'3-�Et�f.ii " _._._.�__ r . . - . 1 "-i _...._.�._.. ...�'� , .� ....�.._ _ _.�_ � � � I 4�i1501._�....._"_.'_.__._...,..._�. �, � � . � . . .. 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