HomeMy WebLinkAbout03243 - Technical Information Report � .1AEC ER �l`IC Il`IEEF�INC '?
9419 S. 204 PI..ACE - KE[�'T, WASHINGTON 98031 ✓���
� PHor�[E (253) 850-0934 Fa►ac (253) 850-0 i 55
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February 4, 2005
Revised May 4, Z005
TECHNICAL INFORMATION REPORT
SUNSET CREST SHORT PLAT
8 LOTS
NE 19th ST.
RENTON, WA.
PREPARED FOR:
.���.'�
J & M Land Development, Inc. '���v�t�,�G'�.
Marc Rousso f����`' � �
:� ;��
P.O. Box 2566 . `''' .,�„
Renton, WA. 98056 'y�; �
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(206) 948-8899 ::� �,.: <. .
4�� ����r.�":` D�
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PREPARED BY: <;.",.",�-�� �,a�__
James J. Jaeger, P.E.
,�,2 y3
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TABLE OF CONTENTS
i
I. OVERVIEW
II. CORE DRAINAGE REQUIREMENTS i
111. OFFSITE DRAINAGE �
IV. PREDEVELOPED DRAINAGE I�
V. DEVELOPED DRAINAGE
VI. DETENTION VAULT DESIGN
Vii. CONVEYANCE SYSTEM
VIII. EROSION CONTROL
/
I. OVERVIEW '',
The proposed Sunset Crest Short Plat is an 8 ►ot single family residential I
short subdivision situated on an existing lots large residential lot with an
area of 3.85 acres. It is located on the south side of NE 19+h St., between
Queen Ave. NE and Redmond Ave. NE {if extended). This project has j
received preliminary pfat approval and a SEPA determination by the City '�
of Renton. The site is zoned R-8, residential. All of the proposed lots will be 'I
single family detached residences. The surrounding properties are also !,
similarly zoned R-8. The site is currently has and existing residence and 3 ,
accessory storage buildings. All of the existing structures/sheds will be ',
removed. The existing house has a driveway that is connected to NE 191h '�,
St. �
The southern half of the site has steep slopes that slope down to the
southeast, to the Honey Creek drainage corridor. There is an un-named
stream within the site, near the southeast property corner that flows into
Honey Creek just south of the property. Honey Creek is located
approximately 100 ff. south of the properfy. The stream and the steep
slopes will constitute a sensitive area. 8oth of these features will be
placed in a sensitive area Tract that will be owned by the Homeowners
Assoc. The steepest slope is approx. 50% near the edge of the stream at
the southeast property corner. The sloped area of the site will not be
developed. The soils on the site are a fine sand with some gravel. The
norfhern half (upper area) of the site displays a typical residential
landscaping with few trees, tall grass, many shrubs. The landscaping has
not been well maintained. The southern half of the site, on the steep
slopes, is undisturbed forest. The existing drainage sheet flows across the
properfy to the southeast. It flows down the steep slopes and into the un-
named stream. The proposed drainage system will use a surface-placed
"driscopipe" to carry the runoff down the slopes and into the stream.
The proposed use of the property as an 8 lot residential short subdivision
will be consistent with the surrounding developments. All of the
surrounding properties are developed, except for the stream corridor to
the south and the high-tension power line easement to the west. The
proposed lots wilt range in size from the minimum of 4500 SF to a maximum
of 6640 SF. The density of the plat is 5.44 units per acre in the R-8 zone.
Access to the new lots will be from a new internal public street that runs
north/south and is connected to NE 19ih St. This street will be a dead-end
public street that terminates with a turnaround bulb. The new street is
proposed to be 28' wide residential half-street with a 35' right-of-way. The
reduced ROW will be wide enough to accommodate the street and
� �,I
sidewalk on the plot side. The reduced ROW width is needed to keep the
net plat area at a maximum and to allow a reasonable minimum density.
NE 19�h St. will be improved with additional rood paving, curb, gutter and �
sidewalk along the frontage. A new water main and sewer main will be
installed in the new street. The water main will end at the cul-de-soc bulb.
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- Page 1 oi 2
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King County Bullding and Land Development Divlslon
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
. . . �- � - . . .
- . � i »• � . «-a • .
Project Owner �� r^ t��•e+ L�esJ P.j�P-��� Project Name �►!N� ���o��m'� �
Address •d �� Z�o �� w� Localion S ,
Phone��� q�" �4 9 � Township �
Projed Eng neer �OJ+�1'P S �4-�.�— Ran9e Z3
Company Sect�on �-- �
9 S. L• � Project Size 3��S AC i
Address Phone Upstream Orainage Bas;n S¢e �J AC �
W t� . �031
z � �so- 04�-
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� SuSdi��ision � pOF/G HPA � Shore(ine�!ar.age�^�e�t
�Shorl SuSdivision 0 CpE�p.a � Rodcey
� 0 Grading 0 pOE Dam Safey � Swct�r�J Vauf:s I
� � Commercial � FEN,A Flood�lain 0 ���� �i
� � Other I � COE 1"Jetla�ds � H�A I
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�Sl�e�m � ti'Jet!ands �
I 0 Cri;ic21 Stream Reach �^' SeepsrSprings
I '_,l Gepressions�S�.�ales �� High Groundwa;er Table !
, � ^
; � L-�ce i; Grcund�.ti�ater Recharge
; �S'eep Slopes �i Other __
; � Lakesice trosion Haz�:d
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Page 2 ot ✓'"t-'=
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King County Bullding and Land Oevelopment Division ' �
TECHNICAL INFORMATION REPORT (T1R) WORKSNEET
� � . • � � �.� .
REFERENCE LIMITATIOWSITE CONSTRAIt�lT
(� Ch.4-Downstream Analysis
� � � �Ts �
o -
0
0
a s �
Q Addition�S.tieets Attatched
. � i�
MlhlMUFJI ESC REQUIREIJ,ENTS f.d(NIMUM ESC REQUIREMEh'TS
DURING CONSTRUCTION FOLLOWING CONSTRUCTION �
�Sedimentation Faalities j�S'.�h+l¢e Expcsed Surtace I I
,�Stabilized Conslruclion En;ra�ce �Re;nove and Restare Temponry ESC Fadlities �
�Perimeter Runotf ConVol � C1ea�and Remove All Silt and Deb�s �
�Clearing and Grading Restric;ions Ens�re O�eratio�ot Permanent Fadlities �
�'Cover Prac;ices �Flag Umils oi�GPES
�Consiructicn Sequenoe � OLtier i
� Other �
� � « � �•
0 Grass Unec Cha�nel C TanK U lr,f,�!irat�on �'�;ho�of r'.nalysis
�Pipe System O vau�t � Dep�ess�on �iRT� �e-� 2 ;
� O�n Channel �Er�ercy D;ss�.tcr � F�ew Dis�ersaf Com�ns�:�on:?:i;ica?�cn '
� Dry Pond � ',�e,(�^�d 0 1;'�iver of Elimi;ite�d Site Siorage
��'�'et Pond �S:rean � Region�J Deten;ion f"
i �
8rief Descri�;ion c!System O,�ra;�on P�11 t� S �'1S;
a 6 v�, �- -�-,v�, � S�o �s�'o�
I Facifty Rela d Site Limil�tiors � Additienal Sh��s At;a'ched
Re`e:ence Faciii.y Vr,.;a;�on n
o s c��'�1 �' apwJ� S� �
� '
�_ _
�;.. �_ ,� ��,i� ,.s�.�x, `
11. _ � � _�r.i �f «l I .I
' -- �Drainage Easemer�t
I � Cast in P;ace Vau�t � G1`�r ' �Access Easement '
i
� Ret�ining VJall � �'t��ativo Grov✓th Frotect:on Easement
0 Rockery>4'H�gh �ract
�� Struclur�J o��S:eEp Slope ' � Other
. . �..-.: . c-1 I��'
I or a civii engineer under my supervision havo visiferl the sife. Adual
sito eondi�ons as cbserved were irc�r�ra;c� into Lhis worksheet �nd ihe
ariatchments. To Lhe best of my kncv.leCge L�e information providcyJ �
here is accura;e. S �•'•
r
January 20, �005
OFFICE OF'THE HE.�RING E.�A1�9I1'ER
CITY OF RENTON
1�Tinutes
APPLICANT: A4ark Rousso
J&M Land De��elopment, lnc.
PO Box 2566
Renton,VVA 98056
Sunset Crest Sliort Plat
LUA 04-119, SHPL-H, ECF
LOCATIO'�l: 37]5I�'E 19`hStreet
SUMI�9ARY OF REQUEST: Hearing Examiner Short Plat appro��al for an eight lot
subdi��ision of a 3.55 acre site.
SU1�4A1ARY OF ACTION: De��elopment Ser�ices Recommendation: Appro�e subject to
conditions
DEVELOP?�1ENT SERVICES REPORT: Tl�e De��elopment Sen•ices Report��•as recei��ed by the
E�aminer on December 14, �004.
PL'BLIC HEARP,�'G: Afier re��ie��in�the De�•elopment Sen•ices Report, examinine
available information on file ���ith the application, field
cl�eckino tl�e property and surrounding area;the E�aminer
conducted a public hearing on the subject as fo11o���s:
1iI\UTES
Tlre jo!lox�ilrg minutes are a sumnrnry of rhe Decenrber 28, 2004 Jrerrrirra.
The leaa!record is recorded on CD.
The hearing opened on Tuesday, t�ecember�8, 2004, at 9:01 a.m. in the Council Chambers on tl�e se��enth floer
of the Renton City Hal). Parties ���ishin�to testify���ere affirmed by the Examiner.
The follo�ving exhibits���ere entered into the record:
Eahibit:�'o. 1: Yellow file containing the original Eahibit No. 2: Neighborhood Detail ;�7ap
application, proofofpostin2, proofofpublication and
other documentation ertinent to this re uest.
Exhibit No. 3: Preliminary Short Plat Plan ( Ezhibit No. 4: Preliminary Draina e and Utili Plan
Exhibit No. 5: Zonin Ma
?he hearing opened��-ith a presentation of the staff report by Susan Fiala, Senior Planner, De��elopment
Services, City of Renton, 10» S Grady\'��ay, Renton, 1��asl�ington 98055. TI�e subject plat consists of 3.53
acres ���l�ich are proposed to be divided into eight lots. Tl�e site is located norih of I�E Sunset Boule��ard, access
Sunset Crest Sl�ort Plat
File No.: LUA-Oa-] 19, SI-IPL-H, ECF
January 20, �005
Page 2
to the site �+�ould be from Union A��enue NE to?�E 19 Street. A utility easement is located on tlie���esterl}�
portion of the site. There are steep slopes on the site that encompass a si�nificant amount of the south�.ast
portion of tl�e site. There are tuo gas pipelines tl�at cross the���estern portion of the property and f:�rther to tlie
��+-est are the o��erhead transmission lines. Also located on the site is an unnamed tributary that tra�erses the
southeast portion of the site and drains into Honey Creek, approximately 75-feet to the south of the site. �
There are t���o tracts proposed,Tract A the sensiti��e area tract��hich �+�ould contain all the sensiti��e and I
protected slopes as�vell as the tributary and Tract B ��hich is proposed for tl�e drainage ���et pond located in the
���estern corner of tlie site.
Tl�is subject land is��ested to the R-8 de�elopment regulations tl�at���ere in effect prior to the ne�v code effecti��e
date of No�ember ]0, 200�. '
The En�ironmental Re��ie���Committee issued a Determination of;�'on-Sienificance—?�9iti�ated ��ith nine
mitigation measures. I�'o appeals ��ere filed. � �
The subject site is desienated Residential Sinele Family on the Comprehensi��e Plan Land Use 1�9ap. All land ,
use elements, housing, en��ironmental elements of the comprehensi��e plan are in compliance. The net��as '
calculated to �.4 d��•eUing units per acre ��hich complies ��ith the density requirements for the R-8 zone. The
proposal's compliance ���ith all bui)din�ctandards ��ould be ��erified prior to tlie issuance of indi�idual buildin;
pennits.
All lots comply��ith arran�ement and access requirements of the Subdi�ision Regulations. The propo�ed lots
appear to have sufficient buildin�area tor the de��elopment of detached sin�le-farnilv homes.
.access to Lots 1 throu�h 3 is directiv to;�'E 19'h Street, lots 4 throu_h 3 ��ould ha�•e access from the ne�v public
road (Road ,�). Sireet impro�ements alons the fronta�es of\'E 19'�' Street and Road A are required, includin�
pa��ement, side��alks, Citv of Renten streetlightc, and sireet name si�ns. .A dedication of ten feet of ri�ht-of-��a�
is required for;�E 19'h Street. Tl�e applicant sho��s six feet, the additional four feet appears tl�at it cot�ld be
gained by reducin�the size of Lots-� and � and still meet lot size and ��idth and depth.
Staff recommends the establishment of a maintenance a�reement for all common ir»pro�ements.
The steep slopes ��ould be ]ocated ��ithin Tract A. The north portion of the property is veQetated ���ith grass and
several medium to large trees. A �ro��e of fruit trees are in the south���est portion. The ���estern edge of the
property is cleared for the lar�e overhead po�+�er lines. All ��egetation in the sensitive areas���ould 'oe
maintained.
To protect the privacy of an abuttina nei�hbor���est of the proposed development staff is requiring that a six-foot
high fence be placed along the entire���est property line of the proposed development. The staff further
recommends that the applicant be required to plant t��o ornamental trees ��•ithin the 20-foot front yard setback
area for all lots���ithin the short plat. .
Fire, Traffic and I�litiaation Fees are proposed.
The site is located ��ithin the beundaries ofthe Renton School Dictrict. The School District has inc:icated that
they can accommodate tl�e additional students.
The project»-ould include the development of a new detention pond and a ���etpond located near the west
property line of the cite ���ithin Tract Ei. Staff recommends that Tract B be fenced along its entire perimeter.
Sunsei Crest Short Plat
File T'o.: LUA-0�-1 19, SHPL-}i, ECF
� January 20, �005
Page 3
The site is located ���ithin the City of Renton ���ater sen�ice area. An 8-inch ���ater main and service lines are
required to be installed, including fire h�drants. There is an 8-inch sanitary se���er main in I�'E 19`h Street. The '
se�+ler needs to be moved to the east side of the centerline. Each lot must be served ��•ith an indi�•idual side
sewer. '�
Staff reconunends approval of this short plat subject to fi�•e conditions. ��,
James Jae�er,Jae�er EngineerinQ, 9419 S 204'h Place, Kent, VJA 98031 stated that they ha��e been �rorking���ith I,
staff and a�ree ���ith the conditions mentioned. Re�arding the Ol��mpic Gas Pipeline, it is��ithin the Defense �i
Department Easement,the common easement���ith the pipeline and the PSE po���er lines. Tl�ey ha�e been
sun�e��ed, they are 80 to ]00-feet from the edee of the easement. ln respect to the steep slopes, there ��-as a ,
geotechnical report prepared that addressed the steep slopes, building setbacks for houses and the draina�e plan. I
The recomrnendations from the report�+ere that an�-structures be l 0-feet a���ay from the ed�e of the 30% slopes. ��,
The pond is actually over 30-feet from the top of the 30% slopes and 20-feet from the ed�e of the pip�;ine. 'i
In the staff report, item G, Department �nal��sis Description, in the first paragraph, Tract A and Tract B are
re�ersed.
On pa�e 7. ,-�ccess and Street lir.pro�ements, ;t tal4:s r�bout the additional ;0-feet that ��ill be necessan� alon�'�E
]9'h Street as additional ri�ht-of-»av. Lots l, 2 and 3 can be slid an additional four feet in order to pro�ide the
10 feet and take that space a��•ay from Lots-� and �, it does upset the buildins envelope on Lot 5, more
significantly than Lot 4. Ri�ht no�� there is I S-feet of riRht-of-���ay on their half right-of-��ay on ?�E ]9'�' Street,
a 16-foot read ���ill fit to the curb plus a �-foot side�+alk in a 21-foot half right-of-�va��. A -�2 foot ri�ht-of-��a� is
the minimum and fairly common in ne��r short plats.
The Examiner acked if Lots 1. 2 and 3 could be shertened? �tr. Jae�er stated that Lots 1 and ? ���ere at th�
minimum area no«�. ]t could be accommodated ��ith Lets � and 5. but it seems that there `�otild he four ��'ra
feet of ri�ht-of-���a� t':et �.•cu;d ��:e, �e u���.
Regarding the six-foot ',,�=h �,��o:�d f.nce al��r��the r-i�ti-e «�est ��rc��er7�� line, the��-���euJd 'i}�:e to �,r�di;;� ;l,;at te the
���est property line of road���av and e�en Lot S and possibly the north line of Tract B, up to a point ��here the
pond fencing���ould intersect��ith it. 1'l'ith the pond fence, it states"no chain link, if possible`'. lf we used vin�I
coated chain link��-ithin the easement area that did not front Lot 8 or the offsite propert`�to the north, it seems it
�j�ould not present any aesthetic problem because there is nothir,��hzt ��ou!d �ie��� the fe-;ce.
Ro�er Allan, 3629 I�E l9'�Street, Renton, A�VA stated that he resides to the ���est cf t��e pr�po�ed si'��, o�� t:�e
drainage pond area. They had concerns about the fence to keep people from driving into the house as �.�,�I' :.>
noise and lights. He stated that he did not ha��e any problems ���ith the fencing that��+�as proposed tod;:�.
Arneta Henninaer, City of Renten, Plan Ret�iew Section stated that on page 7 of the staffreport it ment:�-- �'- _
dedication of]0-feet of right-of-�i�ay. The City code requires that road��+-ays be a minimum of�0-feet for ;
right-of-�vay,the code also allo��+�s for ne�v de��elopment, if the applicant submits a letter requesting a
modification, the internal roads may be modified do���n to 42 feet. The question here is NE 19'h Street an,:
is an existing right-of-�vay, that is ����h�.� ��� �d!iti�n��l l� feet'�a��e heen -ec�_�es'ed. It c�:n he 1�:���:ed a± r��r
adjustment, but�vith no promi<<
TlieExaminercalled forfurthe� ,._.,.,,_ ,.;. .;, ,� ". , ,,.,. . �, ,,,. �,,, _,__ ,,., �:_
� � t � - �
no further comments from staff. The hearine closed at 9:48 a.m.
�
Sunset Crest ShoR Plat
, FileNo.: LUA-04-119, SI�PL-H. CCF
January 20, 2005
Page 4
FINDINGS, CO:�CLUSIONS & RECOniA9E�DATIO:V
Having re��ie��ed tl�e record in this matter,the Examiner no�+�makes and enters tl�e follo���ing:
FINDINGS:
]. The applicant, Mark Rousso,J1LA9 Land De��elopment, Inc, filed a request for an 8-lot Short �lat.
2. The��ello�v file containino the staff report,tl�e State Em ironmental Policy Act (SEPA)documentation
and other pertinent materials���as entered into the record as Exhibit#l.
3. The Em•ironmental Re��ie���Committee (ERC), the City's responsible official issued a Detennination of
;�'on-Si`nificance- �1iti�ated (D;`S-1�1).
4. The subject proposal ��as re��ie��•ed by all departments���ith an interest in the matter.
5. The subject site is located at 37]� �E 19th Street. The subject site is located south of?�'E ]9th Street
and immediatelv ��est of Redmond .Avenue \E if it ��ere e�tended to the south. A single f:imil��home
and outbuildin�s �+ere de�eloped on the site.
6. The map element of the Comprehensire Plan desisnates the area in ���hich the subject site is located as
suitable for the development of sinele-famih� uses, but does not mandate such de��elopment ��ithout
consideration of other policies of the Plan.
7. The suhject site is currentl��zoned R-8 (Sin�le Family- 8 d�+�elling units./acre).
8. The subject site ���as anne�ed to the City��itll the adoptic�n of Ordinance 4337 enacted in February ]991.
9. Tl�e subject site is approximatel�•3.5� acres or 167,622 square feet. Tlie parcel is an "L" s�:aped lot tl�at
is appro�imately 640 feet lon�(north to south) by approximately 328 feet��ide at its �+ide:�t and 190 feet
at iis narro��est (frontage along;�E l9th).
]0. A 200-foot���ide transmission po���er line corridor runs at a slight north���est to southeast diagonal along
the ��estern half of the subject site. An Ol�mpic gas pipeline is also located in that comdor.
1]. A tributary of Honey Creek runs at an east to���est diagonal across the southeast corner of the site.
Slopes in the area of the creek range from 35 to 40 percent and extend to the north and north���est. The
topography in the northeast portion of the site is more gentle and is the area ��°here the applicant
proposes developina the plat. The steeper slopes «-ould be set aside and protected as sensiti�e areas in
proposed Tract A.
12. With the exception of the protected areas of Tract A, all vegetation ���ould be remo�-ed from the site to
allow the development of the road,access and lots.
]3. A ne���north-south road ��ould run south along the���estern edge ofthe subject site. It���ould enter from
NE l9th Street and end in a cul-de-sac. The road ���ould provide access to the interior lots. Staff noted I
that the applicant�vould ha�e to dedicate 10 feet of property to permit the���idening of ivE ]9th Street.
The current plans only sho�v a 6-foot dedication.
�
Sunset Crest Shor1 Plat
File No.: LUA-04-1 l9, SI�PL-H, ECF �
' January 20, 2005 �
Page 5 I
l4. The applicant proposes di��iding the non-critical acreage and the acrea�e not encumbered t�y the large 'i
po���er line or gas pipeline into eieht (8) single family lots. Proposed Lots l,2 and 3 would be located I,
along NE l9th Street ���ith Proposed Lot 3 a corner lot. Proposed Lots 4 and 6 throu�h 8 would front I
directly along the new nonh-south street. Proposed Lot 5 ���ould be a pipestem located to the rear or east ,
of Proposed Lot 4. A small portion at the south�+�est corner of Proposed Lot 8 �vould be crossed by the I
power line easement and the subject site's drainage easement. Staffrecommended that Proposed Lots� I
and S be reduced to allow the four(4) additional feet needed for the 19th Street dedication. I
]5. Tract A,the steep slope, sensiti��e area, at approximately 88,020 square feet,accounts for almost half of �I
the square !'ootaee of the subject site. It �vould dominate the south and southeast corner of the subject �,
site. �
16. Tract B «�ould sen�e to hold the storm���ater detention pond. Jt���ould be located in the�vest central area I
of the site and ��ould lie��ithin the po��er line transmission corridor. �,
17. The density for the plat �+�ould be 5.4 d���elling units per acre after subtracting sensiti��e areas (steep I
slopes)and road���ays. I
18. The subject site is located ��ithin the Renton School District. The project is expected to eenerate I
approximately 3 to 4 school a�e children. These students ���outd be spread across the�*rades and �+ould �I
be assi�ned on a space a��ailable basis. i
19. The de��elopment��il l increase traffic by approximately 10 trips per unit or approximately �0 trips for
the 7 ne�j�sin�le-famil��homes (an e�istino l�ome ���ould ha��e �enerated 10 trips). .approximately ten
percent of tlie trips, or approximately 7 additional peak hour trips ���ill be Qenerated in the tnorninQ and
evenino.
�0. �s noted, storm���ater�jould be contained on 1'ract B. It ��ould drain into the tributary creek by a
"driscopipe" that��•ould be placed across the steep slope to offer the least disturbance of that slope. The
��ater's eneray���ould be dissipated as it entered the stream to prevent erosion or scouring at the creek.
21. Staff has recommended ttiat tlie detention s��stem be screened �vith landscaping and fencing. Tl�ey also
recommended tl�at the entire �vestern perimeter be fenced. Staff also recommended that t���o trees be
planted in each lot to restore the aesthetics of the subject site.
22. The subject site is ser��ed by City ���ater and se���er.
23. The south��esterly neiohbor��•as concerned about screening and fencing but accepted staffs
recommendation.
24. The applicant sua�ested that a narro��er road section or smaller dedication might l�elp�i ith its lot layout.
COi�'CLUSIOnS:
I. Tlie proposed sliort plat appears to serve the public use and interest. T']ie applicant has made provision
to protect the sensiti�-e areas on the subject site; actually, half the acreage. The development also«-orks
around not only those sensiti��e areas but the constraints imposed by the large po���er]ine and gas line
easements that are also located on the su6ject site.
Sunset Crest Sl�ort i'I�t
� File No.: LUA-Oa-1 19, SHPL-H, ECF
January 20, �00�
Page 6
2. The de��elopment���ill create additional lots in an area ��ith urban ���ater and se�rer sen�ices. The
de��elopment��il) also increase the tax base of the site and help achie��e the Cit�'s housing objecti��es by
increasin�housing opportunities in the City.
3. The site's sensiti��e south slopes and creek ���ill be protected and storm���ater controls���ill l�elp pre�ent
erosion and scouring of the creek. The detention s��stem should be screened both in terms of the ne�v
lots near it and for the adjacent properlies south and ���est of it. Staffs recommendations on fencing and
landscaping appear appropriate.
4. The applicant ���ill have to dedicate property to allow the ��•idening of NE 19th Street as �►�ell as the ne���
north-south riel�t-of-���ay. Tlie applicant may seek cl�anges to the dedication ��l�ich staff in its sole
discretion may determine appropriate or not. The lots may be shifred or shortened as necessary to
pro�•ide sufficient room for tt�e dedication but all lots must meet the required lot dimensions.
5. 1'�'hile the steeper slopes are beine protected, the new lots should pro��ide some internal landscapine as
su�£ested bv staff to help a�oid the ra�v appearance that ��ill be caused by clearing and �rading the
entire site.
6. lt appears that �i�en the constraints found on and around the subject site that the pmposed short plat is
an appropriate method ofrede�elopin�the subject site.
DECISIO`+:
The short plat for ei`ht(8) lots is appro�ed subject to the rollo��ing conditions:
l. The a�plicant shall compl����ith the conditions imposed by the ERC.
2. The applicant shall present all dedications of pmpert�� to the City Council. Tlie applicant shall dedicate
pmpert��to allo���the ��ideninQ of;�E ]9th Street as ��ell as the new north-south rioht-of-��ay. The
applicant may seek chan�es to street ��idths ��hich staff in its sole diecretion may detennine appropriate
or not.
3. Tl�e lots may be shifred or shortened as necessary to pro��ide sufficient room for tl�e dedication but all
lots muct meet tl�e required lot dimensions.
4. The applicant sliall obtain a demolition permit and complete all necessary inspections and approvals for
the remo��al of all buildings on tl�e site prior to recording of the short plat. The satisfaction of this
requirement is subject to the review and approval of Development Services.
5. A maintenance agreement shall be created concurrently�vith the recording of the short piat in order to
ectablish maintenance responsibilities for all shared improvements. The agreement shall be placed on
tlie face of tl�e final sl�ort plat prior to recording.
6. A six-feot hi�h solid fence(no chain link���ith slats) shall be installed along the entire�a�est property line
of tl�e proposed short plat. A11 fencing shall be located and designed to not interfere�vith sight distances
required at intersections and dri�e���ays. The fence shall be installed prior to recording the short plat.
The satisfaction of this requirement is subject to the rer•ie�v and appro��a1 of Development Services.
7. The applicant shall be required to plant n�o new appro�•ed trees�vithin the 20-foot front yard setback
area of all lots ��ithin the short plat. The applicant shall be required to record a restricti�e covenant
Sunset Crest Short Plal
File No.: LU.4-0-�-1 19, SI�PL-li, CCF
� January 20, �00�
Pa�e 7
against the property prior to final short plat recording,���hich indicates that t���o trees are required to be
planted ��ithin tl�e front ��ard setback area of each ne�+-lot. Tl�is condition shall be subject to the re��ie�v
and appro�•al of the De��elopment Sen�ices Di�•ision and the trees shall be planted prior to final building
permit inspection.
8. Tract B (storm draina�e) shall be fenced along its perimeter. The portions of the tract that abut Lot 8,
the existing parcel to the north and third party property to the ���est, shall include a landsca�ed visual
barrier��ith plant materials that ��•ould provide a��ear-round dense screen ���ithin three(3)}�ears from the
time of planting. All fencing shall be located and designed to not interfere ��ith sight distances required
at intersections and drive��a��s. Tl�e applicant shall submit a fandscape plan and fence desien to tl�e
City's Development Sen•ices Di�ision for re��ie���and appro�•al prior to installation. All fences and
landscaping shall he installed prior to recordin�of the final short plat.
nnnr=r. �r� Tuic ' 1 ':; . _� �-
��� �
FRED J. }CA '�1AN �
HEARI'�G E�CAl�91'�ER
TRANST9ITTED T1�IS 20'h da��of lanuary?005 to the parties of record:
Susan Fiala James Jae�er
1055 S Gradv �'l'av 9-�19 S 204'h Place
Renton, \�'A 9S0>j Kent. \1�A 9S031
Arneta Hennin�er Ro�er.�llan
]OSS S Grad�� \1'av :6�9;�E ]9'"Street
Renton, \'V,4 9805� Renton, 1'JA 9S0�6
TRANSI�'IITTED THIS 20`�'day of January 2005 to the follo„ing:
Mayor Kathy Keolker-Vvheeler Stan Engler, Fire
Jay Covington,Chief Administrative Officer Larry A'Ieckling, Building Official
Julia A'Iedzegian, Council Liaison Planning Commission
Larry Warren, City Attorney Transportation Division
Gregg Zimmerman, PBP\�� Administrator Utilities Division
Alex Pietsch, Ecenomic De��elopment T�'eil 1'�atts, De��elopment Services
Jennifer HenninQ, Development Sen�ices Janet Conklin, Development Services
Stacy Tucker, Development Sen�ices King County Journal
Pursuant to Title IV, Cl�apter 8, Section ]OOGoftl�e City's Code, request Tor reconsideration must be filed in
���ritinQ on or before 5:00 �.m..Februarv 3, 200�. Any aegrieved person feeling that the decision of the
Examiner is arnbi�uous or based on erroneous procedure, errors of law or fact, error in judgment, or the
discovery of new evidence��hich could not be reasonably available at the prior hearing may make ^ �.ritten
request for a revie��� by the E�aminer��ithin fourteen (14)days from the date of the Examiner's der;sion. This
` ,
Sunset Crest Short Plat
� File No.: LUA-04-119, S}iPL-H, ECF
January 20, �005
Page 8
request shall set forth the specific ambieuities or errors disco��ered by such appellant, and the Examiner may,
after revie�v of the record, take further action as lie deems proper.
An appeal to the Ciry Council is governed by Title IV,Chapter 8, Section I]0, ��hich requires that such appeal
be filed w�ith the Ciry Clerk, accompan��ing a filing fee of$75.00 and meeting other specified requirements.
Copies of this ordinance are available for inspection or purchase in the Finance Department, first floor of City
Hall. An appeal must be filed in���riting on or before�:00 p.m., Februarv 3,2005.
If the Examiner's Recommendation or Decision contains the requirement for Restricti�•e Co�-enants, the
executed Co��enants K�ill be required prior to appro��al bv Citv Council or final processino of the file. You
may conlact this office for information on formatting co��enants.
The Appearance of Fairness Doctrine pro��ides that no ex parte(pri��ate one-on-one) communications may occur
concernins pending land use decisions. This means that parties to a land use decision may not communicate in
private ��ith any decision-maker concerning the proposal. Decision-makers in the land use process include both
the Hearin� Examiner and members of the Cit}� Council.
All communications concerninQ the proposal must be made in public. This public communication perTnits all
interested parties to kno�� the contents of the communication and ��ould allow them to openly rebu! t�ie
evidence. Any�iolation otthis doctrine ���ould result in tl�e in�=alidation of the request b}�the Couit.
Tlie Doctrine applies not only to tl�e initial public l�earin�but to all Requests for Reconsideration as ��ell as
Appeals to the Citv Council.
' A POR710N
or
ths S,E, 1/�, SECTION � TO
. WNSHIP
23 N., RANGE 5
E., W,M.
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ORAINACE DETENTION: ,I '. �' - M"' �r� 1 r,�.0��`�- �% .:� ----c�u ••" `�" ��`
� �l/''�..,� � , � ---�---�-,7. ����
�CVfI 2 DETCTiOn ST�NOMO � �� � � i• NOT�� K� cX'SirNC ,t�
� � ��r" f t.�� //��� � �/ SfRVC1VNCS SMALL BC _- �_^��e w O�
FEN�EO POND WITH 2:� SIDE SlOPES � ��-^�� � _ - ` 1 �� � acuovtu - ��� �
EICVATIONS: ' M,�;���. �YP�G+ / l ��l�, o.00 �.ou Z
TOP: 1�9.0 I ` ,�._. _ $CMSIf��{�� /� �. �.00
�' l �•��r�,�/����, �..«>, �� �
SU YEM WATER �EVEL: 126,0, AREA�4416 SC � 1 f-�-_,.�� � / � ��/• %'.S;""
BOttOM: ♦2J,0 �RE�• i --- �' PROFILE - INTERNAL PUBLIC STREET 4
, 978 SP II 11 ` �.-• r • i i �������
/ // �vac„ronia� r.�o' u
VOLVA1E PROVIOED: 15980 Cf 1 '1 1 ���,-�- � =����//�/. nnr.� i•..� �
VOIUME REOUiEO: 1�554 Cf � � i��i�/i i��/��� �
C� 1 �
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WATER QUALITY: . -����:'� h�.'%i r r ir
� ''%'% ,YY�ii�i��� � � �
wErvpr�0 BEIOw OE�ENnON STORACE ' '����• ��,- i rri K .h
toP WE�PONO ELEv: a27.0. �tEw. �976 5� �"�`.�`"�����n�;rr�i La• � �
BOiTOu wETPONO EIEv: 4t9.0, aREA-600 SF �1, 1 �� � �__�� �������/� Z�;g�
vOIUtiE PROwOED: 5152 Ci . --- �� �� ������,� S� ��
vOLUME REOWRED: 5127 CF - - � '���
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A PORTION of the S.E. 1/4, SECTION 4, TOWNSHIP 23 N., RANGE 5 E., W.M.
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' �
II. CORE DRAINAGE REQUIREMENTS
1. Discharge at Natural Location:
The existing site currently sheet flows across the property to the southeast
and over the steep siopes down to the stream near the southeast properfy
corner. There is a public drainage system within Edmonds Ave. NE that
consists of catch basins, piping, man holes and a storm drain main. The
proposed drainoge system will collect the runoff into the pond located
along the west property line and discharge into a surface-placed HDPE
(driscopipe) outfall that will terminate with a gabion energy dissipator and
into the un-named stream. This is the same stream into which the existing
site runoff discharges.
2. Off-Site Analysis:
An upstream and downstream drainage analysis has been performed
and is detailed in section III of this report.
3. Runoff Control:
This project is providing a 1998 King County level 2 standard flow control.
This matches storm duration for the half 2 year through the 50 year storm
event. It matches peak flows for the half 2 year event. The flow control
will be accomplished using a detention pond with an orifice type flow
restrictor.
4. Conveyance System:
The project will provide conveyance piping for the street drainage and
the lot roof downspouts. The piping will be sized to handle the 100 year
developed storm event.
5. Erosion and Sedimentation Control Plan:
An erosion control plan will be prepared and will be included with the
engineering plans. This erosion control system will include silt fencing
along the west and porfions of the north and south property lines,
construction entrance, seeding 8� mulching and clearing limits. A
sediment pond will be designed as parf of the initial grading and
development of the site.
6. Mointenance and Operation:
The improvements to this site will dedicated to the City and will be
maintained by the City. The private driveways and drainage piping will
be maintained jointly by the applicable lots.
7. Bonds and Liability:
The appropriate bonding and insurance forms will be secured prior to any
construction on the site.
SPECIAL DRAINAGE REQUIREMENTS
There are 12 special drainage requirements that may apply to any
project. In this case, none of them apply to this project.
III
III. OFFS{TE DRAINAGE
A. UPSTREAM DRAINAGE
There is no upstream off-site drainage tributary area for this project. The
highest property line is along the north property line, which is also the NE
19th St. ROW. This street has a CB 8� piping drainage system that intercepts
any runoff from the north and directs it to the east within the public ROW.
The existing lot along the east properfy line and the west property line are
generally at the same eievation as the subject site and would not flow
onto the site. The south property line is the top of the slope and the site
drains to this direction.
B. DOWNSTREAM DRAINAGE
The drainage from the site will be collected into the detention
pond/wetpond located near the west property line, within the power line
easement. The detention pond will discharge, vio a flow restrictor, into a
12" high density polyethylene pipe (HDPE). This HDPE pipe, commonly
called "driscopipe" will be placed on the surface of the steep slopes and
run down the slope to a determined location at the bank of the un-
named stream. A gabion basket energy dissipator structure will be
located at the outfall to disperse the pipe discharge into the stream. An
HPA may be required, depending upon the State DFG category of this
stream.
This stream is a well-defined stream channel located at the toe of a deep
ravine. It has the typical stream characteristics and appears to flow
during most of the year. After leaving the properfy, the stream travels
approx. 120 ft. to its confluence with Honey Creek.
Honey Creek is a class 2 stream with salmonids. The flows to the norfhwest
and comes within 75' of the southwest corner of the property. The steep
slope sensitive area tract will restrict all development to approx. 200' away
from the creek, at the top of the slope. Honey Creek flows to the
northwest and discharges into May Creek approx. 4000 ft. from the site.
There are no road crossings between the site and May Creek.
With the King County level 2 detention requirement in place for this ,
project, the developed runoff from the site should not have an impact on 'i
the downstream drainage system, which is Honey Creek. I understand
that the level 2 requirement is a result of problems within the May Creek
Basin.
IV. PREDEVELOPED DRAINAGE
The drainage from the existing site currently sheet rlows towards the top o�
the slope to the south and southeast. The siopes in turn drain down into
the un-named stream. The existing site area to be developed is
characterized by lawn, tall grass and shrubs, with a few trees. The denser
and Iarger trees are located along the steep slopes, which will not be
disturbed.
The project drainage area used the total site area less the sensitive area '
tract, that will not be developed. A porfion of the frontage ROW was also
added to the drainage area. This frontage area consists of the half ROW
area that is south of the centerline. There are no drainage improvements
on the site itself. The existing frontage a�ong NE 19t" St. has an existing
drainage system that picks up the existing pavement. This existing
drainage system will be abandoned when the new curb 8� gutter is
installed. The project drainage area of 1.69 acres was used as the
tributary drainage basin for the detention pond/wetpond. Calculations
used to determine this area are attached.
The existing drainage analysis was performed using the "KCRTS" hydrology
software and its summary tables and charfs are attached for reference.
The methods outlined in the 1998 King County Surface Water Drainage
Manual were used as guidelines. Following this page are the data sheets
used for the computer input 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:
2 year peak flow: 0.07 CFS
10 year peak flow: 0.13 CFS
100 year peak flow: 0.25 CFS
total area: 1.69 acres
pervious area: 1.56 acres
ground cover: till pasture
impervious area: 0.13 acres
ground cover: impervious
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_ `.1 __ --��-L�_-r - - - __ _ _ _-- ____---
SUNSET CREST SHORT PLAT
RCRTS PEAK FLOW SIJI�II�iRY
PRE-DEVELOPED CONDITION
DRAINAGE BASIN AREA: 1. 69 ACRES
IMPERVIOUS SURFACE: 0. 13 ACRES
PERVIOUS SURFACE: 1 . 56 ACRES
TILL, PASTURE
Fiow Frequency Analysis
T�me Series File:pre.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
clow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.132 3 2/09/O1 15:00 0.250 1 100.00 0.990
0.069 7 1/05/02 16:00 0.133 2 25.00 0.960
0.133 2 2/28/03 3:00 0.132 3 10.00 0.900
0.039 8 8/26/04 2:00 0.127 4 5.00 0.800
0.076 6 1/05/05 8:00 0.121 5 3.00 0.667
0.127 4 1/18/06 16:00 0.076 6 2.00 0.500
0.121 5 11/24/06 4:00 0.069 7 1.30 0.231
0.250 1 1/09/08 6:00 0.039 8 1. 10 0.091
Computed Peaks 0.211 50.00 0.980
i
V. DEVELOPED DRAINAGE II
The developed project will include the new detention pond 8� wetpond
located near the west property line of the site. It will be located within a
drainage tract that will be landscaped as recommended by the City. The
site drainage will be routed into the pond using catch basins and pipes
located within the new road. Each new lot will be furnished with a piped
drainage stub that will be connected to the street drainage system or with
a pipe in the rear yards of the lots. The areas used to calculate the flows
were the same as those areas used in the predeveloped drainage
calculations. It should be noted that the frontage improvements include
the new and existing pavement that were south of the right-of-way
centerline.
The detention pond was sized to meet the performance criteria
established by the King County Level 2 detention standard. This criteria is
that the pond can only release at a rate not to exceed 50% of the 2 year
pre-developed peak flow while retaining 50% of the 2 year developed
peak flow. This is the same for the 25 year peak flows. Additionally, the
storm event duration for the developed site conditions must match are be
less than the pre-developed storm duration, for the 50% of the 2 year flow
through the 50 year storm flow. This is the level 2 standard as specified in
the 1998 King County Manual. A wetpond will be used to meet the water
quality standards. The wetpond will utilize the detention pond area and
will provide the required dead storage below the detention live storage.
The volume for the dead storage is based on the area of the impervious
and pervious surfaces that drain into the pond.
Similar to the existing condition, the KCRTS method was used to determine
the peak flows for the various sfiorm events. A duration curve comparison
was performed to evaluate the vault performance. 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 are:
2 year peak flow: 0.32 CFS
10 year peak flow: 0.39 CFS
100 year peak flow: 0.65 CFS
total area: 1 .69 acres
pervious area: 0.57 acres
ground cover: till grass
impervious area: 1 .12 acres
ground cover: impervious
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SUNSET CREST SHORT PLAT
RCRTS PEAR FLOW Si)I�lARY
DEVELOPED CONDITION
DRAINAGE BASIN AREA: 1. 69 ACRES
IMPERVIOUS SURFACE: 1. 12 ACRES
PERVIOUS SURFACE: 0. 57 ACRES
TILL, GRASS
Flow Frequency Analysis
Time Series File:dev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob ',
(CFS) (CFS) Period
0.323 6 2/09/O1 2:00 0. 650 1 100.00 0.990 'i
0.265 8 1/OS/02 16:00 0.421 2 25.40 0. °6G �',
0.387 3 2/27/03 7:00 0.387 3 10.00 0. 9'= � �I
0.290 7 8/26/04 2:00 0.398 4 5.00 0.� " " i
0.398 4 10/28/04 16:00 0.343 5 3.00 O. E
0.393 5 1/18/06 16:00 0.323 6 2.00 0.5
0.421 2 10/26/06 0:00 0.290 7 1.30 0.�
0.650 1 1/G9/08 6:00 0.265 8 1.10 0.0�_
Computed Peaks 0.574 50.00 0.980
SUNSET CREST SHORT PLAT
KCRTS LEVEL 2 DETENTION
POND DE S I GN SZJNIl�?ARY
Retention/Detention Facility
Type of Facility: Detention Pond
Side Slope: 2.00 H:1V
Pond Bottom Length: 70.00 ft
Pond Bottom Width: 32.00 ft
Pond Bottom Area: 2240. sq. ft
Top Area at 1 ft. FB: 5085. sq. ft
0.117 acres
Effective Storage Depth: 9 .70 ft
Stage 0 Elevation: 423.30 ft
Storage Volume: 15588. cu. ft
0.358 ac-ft
Riser Head: 9.70 ft
Riser Diameter: 12.00 inches
Number of orifices: 2
Full Head Pipe '
Orifice # Height Diameter Discharge Diameter �
(ft) {in) (CFS) (in) �i
1 0.00 0.92 0.050 �
2 3.20 1.40 0.065 9.0 I
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation Surf Area �
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft)
0.00 923.30 0. 0.000 0.000 0.00 2240.
0.01 923.31 22. 0.001 0.002 0.00 2244 .
0.02 423.32 45. 0.001 0.003 0.00 2248 .
0.03 423.33 67. 0.002 0.004 0.00 2252.
0.04 423.34 90. 0.002 0.004 0.00 2256.
0.05 423.35 113. 0.003 0.005 0.00 2260.
0.06 923.36 135. 0.003 0.006 0.00 2265.
0.07 923.37 158. O.004 0.006 0. 00 2269.
0.08 423.38 181. 0.004 0.006 0.00 2273.
0.09 923.39 203. 0.005 0.007 0.00 2277.
0.19 923.49 433. 0.010 0.010 0.00 2318.
0.29 423.59 667. 0.015 0.012 0.00 2360.
0.39 423.69 905. 0.021 0.014 0.00 2402.
0.49 423.79 1147. 0.026 0.016 0.00 2449.
0.59 423.89 1394. 0.032 0.018 0.00 2486.
0. 69 423.99 1645. 0.038 0. 019 0.00 2529.
0.79 424.09 1900. 0.049 0.020 0.00 2572.
0.89 924.19 2159. 0.050 0.022 0.00 2616.
0.99 924.29 2923. 0.056 0.023 0.00 2660.
1.09 424.39 2691. 0.062 0.024 0.00 2709.
1.19 929.99 2969. 0.068 0.025 0.00 2748.
1.29 429.59 3241. 0.074 0.026 0.00 2793.
1.39 424.69 3522. 0.081 0.027 0.00 2838.
1.49 424.79 3808. 0.087 0.028 0.00 2883.
1.59 424.89 4099. 0.094 0.029 0.00 2929.
1.69 924.99 9399. 0.101 0.030 0.00 2975.
1.79 425.09 4699. 0.108 0.031 0.00 3022.
1.89 425.19 9998. 0.115 0.032 0.00 3068.
1.99 925.29 5308. 0.122 0.032 0.00 3115.
, 2.09 925.39 5621. 0.129 0.033 0.00 3163.
2.19 925.49 5940. 0.136 0.034 0.00 3210.
2.29 425.59 6263. 0.194 0.035 0.00 3258.
2.39 425.69 6592. 0.151 0.035 0.00 3307.
2.49 425.79 6925. 0.159 0.036 0.00 3355.
2.59 925.89 7263. 0.167 0.037 0.00 3404.
2.69 425.99 7606. 0.175 0.038 0.00 3953.
2.79 926.09 7953. 0.183 0.038 0.00 3503.
2.89 926.19 8306. 0.191 0.039 0.00 3553.
2. 99 926.29 8669. 0.199 0.040 0.00 3603.
3.09 426.39 9027. 0.207 0.040 0.00 3653.
3.19 426.49 9395. 0.216 0.091 0.00 3704.
3.20 426.50 9432. 0.217 0.041 0.00 3709.
3.21 426.51 9469. 0.217 0.092 0.00 3715.
3.23 426.53 9543. 0.219 0.043 0.00 3725.
3.24 426.54 9581. 0.220 0.095 0.00 3730.
3.26 426.56 9655. 0.222 0.098 0.00 3740.
3.27 426.57 9693. 0.223 0.052 0.00 3745.
3.29 926.59 9768. 0.224 0.056 0.00 3756.
3. 30 926. 60 9805. 0.225 0.059 0.00 3761.
3.32 426.62 9881. 0.227 0.060 0.00 3771 .
3.92 926.72 10260. 0.236 0.067 0.00 3823.
3.52 926.82 10645. 0.249 0.073 0.00 3874 .
3.62 426.92 11035. 0.253 0.078 0.00 3927. ;
3.72 427.02 11930. 0.262 0.082 0.00 3979.
3.82 427.12 11831. 0.272 0.087 0.00 4032. �
3. 92 427.22 12237. 0.281 0.090 0.00 9085.
4.02 427.32 12648. 0.290 0. 094 0.00 4139. �
4 .12 427.42 13065. 0.300 0.097 0.00 4193. ,
4.22 927.52 13487. 0.310 0.101 0.00 9247. I
4.32 427. 62 13919. 0.319 0.104 0.00 4301.
4.42 927.72 14397. 0.329 0.107 0.00 4356. I
4.52 427.82 14785. 0.339 0. 110 0.00 4411.
4.62 927. 92 15229. 0.350 0.113 0.00 4466.
4.70 428.00 15588. 0.358 0.115 0.00 4511.
4.80 428.10 16092. 0.368 0.426 0.00 4567.
4.90 428.20 16502. 0.379 0. 991 0.00 4623.
5.00 428.30 16967. 0.390 1.720 0.00 4680.
5.10 428.40 17438. 0.400 2.520 0.00 4737.
5.20 428.50 17914. 0.911 2.800 0.00 4794 .
5.30 428.60 18396. 0.422 3.060 0.00 4852.
5.40 428.70 18884. 0.934 3.300 0.00 9910.
5.50 428.80 19378. 0.945 3.520 0.00 4968.
5. 60 428.90 19878. 0.456 3.720 0.00 5027.
5.70 429.00 20384. 0.968 3. 920 0.00 5085.
5.80 429.10 20895. 0.980 9.110 0.00 5195.
5.90 429.20 21413. 0.492 9 .290 0.00 5204.
6.00 929.30 21936. 0.504 4.460 0.00 5264.
6.10 429.90 22465. 0.516 4. 620 0.00 5324 .
6.20 429.50 23001. 0.528 4.780 0.00 5385.
6.30 429.60 23592. 0.590 4. 940 0.00 5945.
6.40 429.70 24090. 0.553 5.080 0.00 5507.
6.50 429.80 24644. 0.566 5.230 0.00 5568.
6. 60 429.90 25204. 0.579 5.370 0.00 5630.
6.70 430.00 25770. 0.592 5.510 0.00 5692.
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 0.65 ******* 0.42 4.80 428.10 16036. 0.368
2 0.42 0.13 0.09 3.15 426.45 9252. 0.212
3 0.39 ******* 0.09 3.85 427.15 11962. 0.275
4 0.35 ******* 0.03 1.92 425.22 5083. 0.117
5 0.34 ******* 0.09 3.92 427,22 12253. 0.281
6 0.32 ******* 0.11 9 . 68 427.98 15506. 0.356
7 0.29 ******* 0.03 2.09 425.39 5967. 0.126
8 0.27 ******* 0.04 2.49 925.74 6742. 0.155
Duration Comparison Anaylsis
Base File: pre.tsf
New File: rdout.tsf
Cutoff Units: Discharge in CFS
-----Fraction of Time----- ---------Check of Tolerance-------
Cutoff Base New �Change Probability Base New �Change
0.039 I 0.71E-02 0.41E-02 -41.3 I 0.71E-02 0.039 0.035 -9. 6
0.096 I 0.52E-02 0.21E-02 -60.1 I 0.52E-02 0.046 0.038 -17.8
0.054 � 0.38E-02 0.20E-02 -97.4 � 0.38E-02 0.059 0.039 -26.2
0.061 I 0.28E-02 0. 18E-02 -35.1 I 0.28E-02 0.061 0.090 -33. 9
0.068 I 0.19E-02 0.16E-02 -17.9 I 0.19E-02 0.068 0.059 -13. 1
0.075 I 0. 14E-02 0.13E-02 -4 .7 I 0. 14E-02 0.075 0.073 -2.7
0.083 � 0. 11E-02 0.85E-03 -21.2 I 0.11E-02 0.083 0.079 -9 .8
0.090 I 0.82E-03 0.44E-03 -46.0 I 0.82E-03 0.090 0.089 -6.6
0.097 I 0.65E-03 0.29E-03 -55.0 I 0. 65E-03 0. 097 0.087 -10. 6
0.105 � 0.41E-03 0.21E-03 -48.0 I 0.41E-03 0.105 0.091 -13.5
0. 112 I 0.23E-03 0.65E-04 -71.4 I 0.23E-03 0.112 0.103 -7.8
0.119 I 0.15E-03 O.00E+00 -100.0 I 0. 15E-03 0.119 0. 108 -9.2
0. 127 I 0.98E-04 O.00E+00 -100.0 I 0.98E-09 0. 127 0. 112 -11.9
There is no positive excursion
Maximum negative excursion = 0.029 cfs (-37.1$} �
occurring at 0.065 cfs on the Base Data:pre.tsf
and at 0.041 cfs on the New Data:rdout.tsf
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VII. CONVEYANCE SYSTEM
The piping was sized to accommodate the 100 year developed flows as
identified in this section of the report. The modified rational method was
used as shown in the King County Drainage Manual. The pipes for this
plat are a minimum 12" diameter and all will be corrugated polyethylene,
double-walled pipe such as ADS-N12 or equal. The 100 year storm flow for
the entire site was calculated. It was checked that each main pipe
segment could handle the entire site's 100 year peak flow.
�
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r SECT70N D.4 ESC MF.ASURES ,
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D.4.5.2 SEDIlViENT POND
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Code: sP S��mbol: U
� Purpose
Sediment ponds remove sodiment from runoff originating from disrurbed areas of the site. Sediment
ponds are rypically designed to only remo��e sedimcnt as small as medium silt(0.02 mm). As a
conscquence,they usually r�duce turbidiry only slightly.
Conditions of Use
A sediment pond sball be us�d a�here the conuibuting drainaee area is 3 acres or more.
Design and Installation Specifications
l. Sa Fgure D.4.I,Fgure D.4J,and Figure D.4.K for dctails. -
2. If permanent runoff control farilities are part of tbe project,they should be used for sediment retention �.
(set"Use of Perraanent Drainage Farili�es'on page D-25).
Determining Pond Geometry
l. Obtain tha discharge from t�e hydrolo�ic calcularions of the pealc flow for tbe 2-year runoff event
(Q�. The 10-year p-.,ak flow sha11 be used if tbe project siie, expected tirning and duraDon of
conswction,or doR�nsuram coadi�ons a��rnnt a highcr lcvel of protccdon. If no hvdroloeic anaJ}zis
is roquired,the Rarional Method may be used(Section 3.2.1 of the Surface Water Design Mar.u�. �
2. Determine the requ.ired surface a.rea at:be top of the riser pipe �7th the eauaDo�: -
SA = 2 x Q�/0.0�?96 or 2GE0 squ�.�-e feet per cfs of inflow
See Secaon D.4.5.1 (p.D-26)for more i;iformation on the deriv�ion of the su�ace area c�lcula�on.
3. 'I�e basic geome�ry of the pond ca.n now be determined using the following design criteria:
• Required surface zrea SA (from Step 2 zbo�•e)at top of riser
• Minimum 3.5-foot dep;�from top of riser to bo�tom of pond
• Maximum 3:1 inurior side slopes and maximum 2:1 exterior slopes. The interior slopes czn be
increased to a maximum of 2:1 if fencing is pro�•ided at or above the maximum a�ater surface
• One foot of freeboard bet��een the top of Lhe riser and the crest of the emergency spill��ay
• Flat bottom
• Minimum one foot deep spillwa��
� • I.ength-to-width rztio between 3:1 and 6:1.
Sizing of Discharge Mechanisms
Principal SpilIwa�:Deterrnine the required dizmeter fer the principal spillway(riser pipe). The diameur
shall be the minimum necessary to pass the pre-developed 10-year peak flow(Q�o). Use Figure 5.3.4.H
(Sl�'D.'vl Chapter 5)to determ:ne this diuneter(h=one foot). Nore:A pernzanent connol strucru�e may be �
used instead of a remporary riser.
9/1/9S Erosion and Sedi:nent Convo!Stxndzrds
D-28
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EmerEency Overflow Spillway;Detrsmine the required size and duign of the emergency o��ow'T' =
spillway for the developed 100-year peak flow using the procedure in Sxdon 5.3.1 ("Emergen�y - ' � .�
� Overtlow Spillway"subsection)of the Surface Waser Dcsign Manual. -
Dewatering Orifice:Determine the si2e of the dewatering orifice(s)(minimum 1-inch diameter)using a
modifiad version of the discharge equation for a vertical orifice and a b�sic equarion for the area of a
circular orifice.
1. Decerrnine the required area of the orifice with the following equation:
A,(2h)os
A° 0.6x3600Tg o.s
where Ao = orifice area(square feet)
AS = pond surface area(square feet)
h . = head of water above orifice (height of riser in feet)
T = dewauring tirne(24 hours)
g - accelention of gra�lry(32.2 feeVsecond2) �
2. Convect the requirod si:rface area ro t�e required diameter p of the orifice: 'I
D=24x A° =13.54x A,
n
3. The vertical,perforated tubing connected to the dew•atering orifice must be at least 2 inches larger in
� diameter than the orifice to unprove flow characteristics._The size and number of perforations in the
- tubing should be large enouv,h so that the tubing does not restrict flow. The flow nte s5ould be
controlled by the orifice.
Additional Design Specifications
• I�e pond shall be di`zded into two roughly equal volume cells by a penneable di�zder that will
reduce turbulence while allowing movernent of water between cells. The divider shall be at least one-
half che height of t6e riser and a minimum of one foot below the top of the riser. Wire-backed,2-to
3-foot high,ex�a s�ength filter fabric(see Section D.4.3.1)supported by veated 4"x4"s can be used
as a divider. Alternarively,staked straw bales wrapped�zch filur fabric(geotexule)cnay be used.
If the pond is more than 6 feet deep,a different mechanism must be proposed. A riprap embanl�nent
is one acceptable method of separarion for deeper ponds. Other designs that satisfy the intent of this
provision are 2llowed as long as the di��der is permeable, strucn:rally sound,and desi;ned to prevent
erosion under or uound the barrier.
• To aid in deterrnining sediment depth,one-foot intervals shall be prominently rnarked oa the riser.
• If an emban�ent of more than 6 feet is proposed, [he pond must comply wzth the criteria under
"Embankments"in Secdon 5.3.1 of[6e Surface Wa:er Design Mar.ual.
Maintenance Standards
l. Sediment shall be removed from the pond when it reaches 1 foot in depth.
2. Any damage to the pond embanlanenu or slopes shzll be repaired.
� �
Y��' ,
Flosion and Sediment Control Standards 9/1�8
D-29
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- � Earth G�nsultants, Inc.
c�o,�,�;�i�,g,,,�,c�ao�s&�,«a,m�r,r�i s�,,;� Established t975
GofisttLdion Tcsti�lg&ICBO/N'ABO Ins{�ec�tion Sen�Ces
June 16, 2005 E-11352
J & M Land Development
P.O. Box 2566
Renton, Washington 98056
Attention: Mr. Marc Rousso
Subject: Geotechnical Engineering Study Addendum
Detention Pond and Driscopipe Outfall Recommendations
Sunset Crest Short Plat
3715 Northeast 19"' Street
Renton, Washington
Reference: Earth Consultants, Inc.
Geotechnical Engineering Study
E-1 1352, dated September 2, 2004
� Dear Mr. Rousso:
In accordance with your request, Earth Consultants, Inc. (ECI) is pleased to present this
letter providing detention pond and Drisco pipe outfall �ecommendations for the Sunset
Crest Short Plat development located at 3715 Northeast 19th Street in Renton. We
previously prepared the referenced geotechnical engineering study for this project. In
preparing this letter, we reviewed the proposed storm drainage plans and our previous work.
The irregular shaped site, located at 3715 Northeast 19"' Street in Renton, Washington, is to
be developed with eight single-family residence lots. Stormwater runoff from the proposed
development is to be diverted to a stormwater control pond to be located in Tract B near
the southwest corner of the site. The stormwater control pond is to contain two cells,
each with a bottom elevation of approximately 218 feet. Excavations of up to 12 feet
below existing grade are expected to reach this proposed elevation. The proposed
stormwater pond will be bordered immediately to the south by a south-facing slope that
descends south to Honey Creek at gradients of around 30 percent or greater. The walls of
the pond are to be sloped at a gradient of 2H:1 V (Horizontal:Vertical). An approximately
five-foot high soil berm is to be constructed with structural fill on the south side of the
pond and is to include a 12-inch thick clay liner.
1805136th Place N.E.,Suite 201,Bellevue,WA 98005 Other Locations
Bellevue(425)643-3780 FAX(425)746-0860 Toll Free(888)739-6670 Fife
J & M Land Development E-1 1352
June 16, 2005 Page 2
Outflow from the pond is to be diverted to the centerline of an unnamed tributary of Honey
Creek, located east of the pond. The outflow is to be tightlined down an east-facing steep
slope to the tributary through a Drisco pipe outfall pipe. The slope descends east at
gradients of 20 to 50 percent. The outfall pipe is to lie on the surface of the slope and will
be anchored with two pipe anchors. �
A total of six test pits were excavated at the subject site on August 18, 2004, to
determine subsurface soil conditions. At our test pit locations, we generally encountered
six to eight inches of topsoil and duff. Underlying the topsoil and duff layers, we
encountered a surficial layer of loose silty sand with gravel to depths ranging from 2 to 3.5
feet below existing grade. Underlying the surficial soils, we encountered silty sand with
gravel, which we classified as glacial till. As such, we anticipate glacial till may be
encountered in the proposed pond excavation.
It has been our experience that steep slopes such as those occupying the southeastern
portion of the site are often mantled with a surficial layer of loose, weathered soils. These
soils are typically three to four feet thick.
Conclusions and Recommendations
In our opinion, construction of the pond and Drisco pipe outfall as shown should be feasible
from a geotechnical standpoint. However, it has been our experience that the relatively
impermeable glacial till encountered at depth can contain lenses of highly permeable sand.
Due to the proximity of the pond to the slope and the potential for encountering a relatively I
permeable sand lens in the pond excavation, which could provide a conduit for water seepage
between the pond and slope, it is our opinion that the proposed pond should be lined with a
low permeability soil liner. Instead of the proposed 12-inch thick clay liner, the soil liner �
should be at least 18 inches thick and meet the following gradational requirements. -
Gradational Requirements
Sieve Size Percent Passing
6-inch 90
I 4-inch 100
No. 4 70 — 100
No. 200 20 — 100
Earth Consultants, Inc.
• �
J & M Land Development E-1 1352
June 16, 2005 Page 3
The pond liner may consist of a glacial till derived fill. Based on laboratory testing of test pit
samples, there are soils within the site that meet these gradational requirements. '
The liner materials should be placed in six-inch thick loose lifts and each lift should be
compacted to 95 percent of maximum dry density per ASTM D-1557, Modified Proctor. A
representative from ECI should be on site during the compaction operation and liner
placement to observe soils encountered, sample and test the liner materials, and test the
relative compaction of the soil liner.
The Drisco pipe outfall pipe anchor footings should extend into native soil. A
representative from ECI should be on site during the anchor installation to verify bearing
soil conditions. I
We trust this information meets your needs. If you have any questions, please call.
�
Respectfully submitted,
EARTH CONSULTANTS, INC.
Eric L. Woods
Staff Geologist
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P�Sed Ge°� /
Scott Dinkelrnan
Scott . Dinkelman, LEG
Principal
ELW/SDD/lap
Distribution: Jaeger Engineering
Attention: Mr. James Jaeger, PE
Earth Consultants, Inc.