HomeMy WebLinkAbout02848 - Technical Information Report - Drainage�
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��������'H PLACE
I)�AINAGE REPORT
FOR: ARC aRIUS HO�IES
P.O. BOX 257
NEW CASTLE, WASHNGTON
(-���) �-�6-�471
BY: LEROY SLRVEYORS & ENGIN�EERS, I�;C.
1103 SHAW RO AD
PUYALLtiP, �VASHII�GTON 98372
(2�3) 845-6605 � �
D_�TE: October 23, 1999 �
RE�.�ISED: ti'Iarch 14, 2000
�pril 1�'. ?000
JOB NO.: ���l
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F�vG[�`E}�R: PAUL E. G1ZEE\�, P.E.
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T:�BL.E OF CONTENTS ..................................................................................................... 2
APPE�,'DICES..............................................................................................................................................2
Section 1 - Project Overview �
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S:.ction 2—Conditions and Requirements Summary...........................................................4
Section3 — Offsite Analysis................................................................................................. 5
Section 4 —Flow Control and Water Quality Facility!�nalysis and Design........................ 6
PartA—Ehisting Site Hydrology.....................................................................................................................6
` Pan B—Developed Site Hydrology..................................................................................................................7
Part D—Fiow Control Svstem..........................................................................................................................8
PartE—�Vater Quality System.........................................................................................................................8
Section 5 —Conveyance System Analysis and Design......................................................... 9
' Section 6—Special Reports and Studies............................................................................... 9
Section7—Other Permits..................................................................................................... 9
Section S —ESC Analysis and Design................................................................................ 10
ClearingLimits...............................................................................................................................................10
Co�rer\�Ieasures..............................................................................................................................................10
PerimeterProtection.......................................................................................................................................10
TrafficArea Stabilization...............................................................................................................................10
SedimentRetention.........................................................................................................................................10
Surface«%ater Controls...................................................................................................................................10
DustControl....................................................................................................................................................10
Section 9—Bond Quantities, Faciliry Summaries, and Declaration of Covenant.............. 11
:�PPENDICES
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Appendix A Figures
Fi�ure 1 —TIR `Vorksheet
Fi;ure 2 — Site Location
Figure 3 —Drainage Basins
Figure 4—Soil Vlap
Fi�ure 5 —Flow Control System &Presettling Basin Sketch
��ppendix B Detention Tank Calculations
Appendix C Wetpond Calculations
Appendix D Conve_yance System Analysis Results
Appendix E Sediinent Trap Calculations ,
��ppendix F Interceptor Swale Calculations ���
AppendiY G Infiltration Trench�'alculations �
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�e��:c�n � - ��-�ject �vea-�-x��v
Tlie project site consists ot a 1.6 acre parcel located at the northwest quadrant of the
intersection of NE 12`h Street and Edmonds Avenue. See Figure 2 for site location. The site
is currently utilized as a single family residence. Improvements include a house with
associated carport, driveway, and lawn all in the northeast portion of the site. The remainder
of the site is vacant with overgrown blackberry bushes, and small alder and fruit trees. The
existing topography of the site includes slopes ranging from 10 to �0 percent to the west.
The majority of the site has slopes from 10 to 15 percent, but fill, and rockeries have created
�teeper slopes to 50 percent near the south central portion of the site.
After development, the site will consist of 17 single family residential lots and one tract for
stoim drainage. The existin� drainage patterns�vill be maintained with the site sloping to
the west. After grading, the slopes will be limiied to a maYimum of approximately 25
percent with the road and front yard areas generally less than 1� percent.
� limited geotechnical report for this project has been prepared by AGRA Earth &
Environmental, Inc. Based on the soil data obtained for and presented in this report, the
soils onsite can be generally classified as a fine or medium sand (Hydrologic Soil Group A.)
The degree of fine particles varies on the project site. Fewer fines are present in the
southwest corner of the site resulting in an infiltration rate of 1� minutes per inch as
determined by AGRA. This area will be utilized for the proposed infiltration pond. The
remainder of the site has an infiltration rate of 30 minutes per inch as determined by AGRr�.
Tlle analysis appears to confirm the SCS soil mapping for the site of Indianola loamy fine
sand. No evidence of ground�vater was found in the test pit nea�the proposed runoff control
facilities to a depth of 10 feet. Additional data on soils may be found in the above
referenced report prepared by AGRA. Also see Figure 4 for the SCS soil mapping of the
site and surrounding area. I
Runoff from the site, if any, ctu-rently travels as sheet flow across the site from east to west I
�i-ith no well defined drainage course. Roadside ditches in Edmonds Avenue intercept
offsite runoff. This offsite runoff is transported by curbin� and a roadside ditch in Edmonds �
Avenue southerly and�TE 12`° Street westerly into an eYisting closed conveyance system
near the south���est corner of the project site. Under developed conditions, runoff from roof �
drains�vill be directed to individual lot infiltration trenches. Runoff from drive�vays, roads '�
and yards graded to the public roads will be collected in catch basins in the street and
conveyed to public storm drainage facilities near the southwest corner of the site. Flow ,
control will be maintained with a detention tank designed to maintain release rates of the '
predeveloped 2 and 10-year storm events. Additional information reaardinQ drainage basins I
and site characteristics can be found in Fi�ure 3. � I
�_:���.�o�th 1'1.ac;: 1}�ri,,_ � , �-UQL' Pa�e = c� i_
uraina��_=e I��por?
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�+��tiom ? — �onditions a�� �ltec�ui�-ements S�,��masv
�3ased on the requirements of t11e City of Re�-:..:.n and the King County Suriace ���%ater
Vlanagement Design Manual (hereinafter"the manual") this project will be required to meet
Core Requirements 1-5 & 8, and Special Requirements 1-�. Following is a summary of
these requirements and how they will be addressed for this project:
• Core Requirement#1,Discharge at the natural location.
o As required by the Ciry of Renton, dischar�e from the proposed quantity
control facility will be routed to the existing public storm drainage system.
Runoff from some rear yards will follo��natural drainage patters as overland
flow to the west.
• Core Requirement#2, Offsite Analysis
c Because from the site will be controlled by a detention facility and individual
lot do�vnspout infiltration trenches, there will be no significant adverse '
impact on the drainage basin.
• Core Requirement#3, Flow Control '
c This project will meet the Level 1 flow control requirements.
c Based on Table 1.2.3.A, for Level 1 flo��v control, ���ith no downstream
problems identified, this project��ill be required to match 2 year and 10 year
peak nmoff rates for existing and developed conditions. The proposed design
��-i11 provide detention storage and restricted release rates to meet these
requirements. Other requirements of Chapters 3 & � of the manual will be
rnet.
o Runoff from roofs and some drive«ays will be dischar�ed to individual lot I
downspout infiltration trenches designed based on Small Site DrainaQe
Requirements.
o Runoff from the shared drivevvay for Lots 10-12 will be discharged into an
infiltration trench sized for the 10 year event. Overflow will discharge into
the bypass system.
o Bypass system will consist of a grass lined s�vale��hich will intercept runo r�i,
from lawns not graded to the roads. The swale will tie int� the clos;:d
conveyance system downstream of the detention tanl..
� Core R�quirement +4, Conveyance System
� The conveyance is required to be desianed to handle the �� �e:_n- �tor:n �.;�ent
using the rational method. The system will be desi�ned to handle the 1�����i
vear event and the rational method will be used. Other requirements o��
Chapters 3 and 4 will be met.
a Core Requirement#5, Erosion & Sediment Control
o As required, an ESC plan will be prepared as part of the e���ineeriil� ��'�_�:�,�.
T',ie ESC plan will provide clearing limits, cover measures, perimeteT.
protection in the form of silt fencing, traffic area stabilization, sedimr
retention in the form of a sediment tr,
,t..._�:;�_��� i<�. _.
• r�re R�q�_iir��ller.t = �, �Vate.r Quality �
o vv ater quality will be provided b�� a u-etpcnd made up of dead storage in the I
proposed detention tank. Due to topo�raphic constraints, the driveways for ,
Lots 10, 11, & 12 will not be a aded towards the proposed roadway. As '
allowed in Section 1.2.8.2 runoff from this area will be released untreated.
The driveway area in question v�,�ill likely be less than 2300 square feet.
There is 650 square feet of existing drive�vay surfaces that qualify as a
treatment trade area. The remaining area is less than 5000 square feet and
therefore will meet the requirements of tintreated Discharges. To prevent
impacts on downstream properties, runoff from the shared driveway will be
discharged to an infiltration trench beneath the driveway.
• Special Requirement#1, Other adopted area-specific requirements
o To our knowledge, the project site is not in an area with additional specific
requirements. '
• Special Requirement#2, Floodplain/Floodway delineation ,,
o The project site does not contain or is adjacent to a stream, lake, wetland, or I
closed depression, and therefore is required to have a floodplain/floodway
delineation. '
• Special Requirement#3, Flood protection facilities
o No flood protection facilities either eYist near the site, or are required.
� Special Requirement #4, Source Controls ���
o The project is neither a commercial, industrial, or multifamily site
development and therefore does not require water quality source controls.
• Special Requirement#5, Oil Control
c The project will not constitute a high use site, and therefare does not require
oil control.
Section 3 — �ffsite Anaivsis
Because roof runoff���ill be directed to individual lot downspout infiltration trenches, and '
dischar�e from the proposed detention tanlc will limit discharge to the predeveloped 2 and ',
�0 year runoff rates, the project will not have a significant adverse impact on the ,
downstream and/or upstream drainage system. Therefore, this project should be exempt '�
1i-oin Core Re�uirem�nt��2 as listed i.1 section 1.%.Z of the manual, item rl.
F.lizaheth Place a��r:? 1�, _'�?00 � - . •� !:
ll;:iina,e Repo.:
Section -� — Flo`�� Cont�-ol and `�'�ter Qualitv �'��,il�*� ���l,ys�� �r��i Desi�n
Part A—EXisting Site Hydrology
The entire 1.6 acres of the project site currently drains as one sub-basin to the west. The
existing topography of the site includes slopes ranging from 10 to 50 percent to the west.
The majority of the site has slopes from 10 to 15 percent, but fill, and rockeries have created
steeper slopes to 50 percent near the south central portion of the site. Runoff from the site, ,
if any, currently travels as sheet flow across the site from east to west with no well defined
drainage course. Offsite runoff is intercepted by roadside ditches in Edmonds Avenue. This �
offsite runoff is transported by curbing and a roadside ditch in Edmonds Avenue southerly ,
and NE 12th Street westerly into an existing closed conveyance system near the southwest �
corner of the project site.
A limited geotechnical report for this project has been prepared by AGRA Earth &
Environmental, Inc. Based on the soil data obtained for and presented in this report, the
soils onsite can be generally classified as a fine or medium sand (Hydrologic Soil Group A.)
The degree of fine particles varies on the project site. Fewer fines are present in the
south�vest corner of the site resulting in an infiltration rate of 1� minutes per inch as
determined by AGRA. This area will be utilized for the proposed infiltration pond. The
remainder of the site has an infiltration rate of 30 minutes per inch as determined by AGRA.
The analysis appears to confirm the SCS soil mapping for the site of Indianola loamy fine
sand. No evidence of groundwater was found in the test pit near the proposed runoff control
facilities to a depth of 10 feet. Additional data on soils may be found in the above
referenced report prepared by AGRA. Aiso see Figure 4 for the SCS soil mapping of the
site and surrounding area. For the KCRTS analysis, the entire project site is classified as
out�vash.
Ctlrrently, cover on the site is mostly brush and small trees. E�isting impervious areas '�
include a house, carport, and drive��-ay. A small la��-n exists in the vicinity of the house. ,
See Figure 3 for additional detail regardin� draina�e characteristics of the site. Because no
off-site� flo���s ent�r the site no pre-developed sub-basins for the site�have been identified. ��
F;i_�betl, piacc .�,'�il =_ ,�J�ii,� Pag� G ot 11
Draina�e Reporl
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, F��rt B —Des eioped Site Hydrology
:a�ter development, the site«�ill consist of 17 single family residential lots and one tract for
storm drair�age. The existing drainaje patterns«�ill be maintained��vith the site sloping to
the west. After grading, the slopes will be limited to a ma�cimum of approximately 25
percent ��rith the road and front yard areas generally less than 1� percent.
� Under developed conditions, runoff from roof drains will be directed to individual lot
� infiltration trenches. Runoff from driveways, roads and yards graded to the public roads
��rill be collected in catch basins in the street and conveyed to a detention tank near the
� south�vest corner of the site. Runoff from the shared drive��vay for Lots 10-12 will be
discharged into an infiltration trench. Roof ninoff will drain to individual lot downspout
� infiltration systems. The remainder of the site«�ill consist of la«ns draining westerly to an
� interceptor trench which�vill prevent runoff from crossing into adjacent properties. This
� runoff«ill be directed to the closed conveyance system downstream of the detention tank.
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` The detention tank drainage basin is broken dow-n by ground cover as follo��vs: �'�
Total Area= 0.763 acres '
�rea of road, curb, and sidewalks = 15,�94 sf
( Area of drive«�ays = 6,490 sf
Total impervious area =22,08� sf '�
=0.507 acres �
Remaining area is classified as ourivash grass for the KCRTS analysis= 0.256 acres '',
h See Fi�ure 3 for map of basin area and site �haracteristics.
The remainder of the parcel is classified as followJs:
Total Parcel Area= 1.60 acres
Det. Tank Drain Area= 0.763 acres
Remaining Area= 0.837 acres
Roof Area= 0.585 acres
Roof Area will be infiltrated via individual lot infiltration trenches
Shared Driveway Area= 0.053 acres (assumed)
� Driveway Area will be infiltrated by infiltration trench
Lawn Area= 0.199 acres
Che area not draining to the detention tank will be classified as 0.837 acres ounvash pasture I
in existing conditions and as 0.199 acres ourivash grass in developed conditions. Runoff
«�ill be comp�ared to e:�su�;. rat.s do rlot e�ceed predeeelc�ped conditions.
._..�:�rrt.������ a�;�.l �,, �000 P��t � �;� 1 _
Draina��e I?eport ��
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� Part C —Perforr�ance Standards
The propcsed caetzntion tan�: ���ill l:��e: the L,:vei 1 ��o�-. centrel s�ar���.rds c�me�ii.�� the
predeveloped runoff rates for the 2 and 10 year storms in developed conditior�s.
Section 12.4 of the manual requires that the conveyance system be designed to handle
runoff from the 25 yeax event. The conveyance system will be designed to handle the 100
year event, exceeding the requirements of the manual.
The water quality components of the project are designed to meet the standards from the
basic «�ater quality lnenu.
Pai-t D —Flo��� Control System
See Figure 5 for a sketch of the flow control system. The detention tank will consist of three
runs of 142 Y 91 corrugated aluminum pipe with a total length of 120 feet. The total
required length is broken down into three sections dt�e to site constraints. This arrangement
simplifies tank access and reduces depth requirements �.vhile meeting the design
requirements and limitations of the site. The bottom portions of the first two runs provide
the required wetpond volume as described belo���.
See Appendix B for detention tank calculations.
Runoff from the shared driveway will be disposed of in an infiltration trench 20 feet long, 4 '�
feet deep and 4 feet wide. See AppendiY G for infiltration trench calculations.
Roof runoff will be directed to individual lot downspout infiltration systems. Per section
�.1.1 of the manual, based on the soil classification of fine sand, 75 lineal feet of infiltration
irench ����11 be required per 1000 square feet of roof surf�lce.
Pa; . 1: — ���ater (�ualit�� S��stem
Dea�i storage ��-i11 be provided in �lie detention tank to act as a ��,etponc�. In the tirst run of
pipe, the bottoin foot will allow for sediment retention, the next four feet of depth malces up
a portion of the required wetpond volume. In the second tank, the bottom foot will allow for
sediment retention, and the neYt 1.5 feet provides the remainder of the required wetpond
��olume.
See Appendi� C for�vetpond calculations.
1::.zaL::th P1ace ,��r.- -=. -�;(�(i Pa��� � ot� i 1
Ur:ii;;.i�e IZer�ort - —
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��e�tio� a -- �C'=ar�;���-���p �vsteBn '�.na+��si� �nd Design
� d::taiieci convey�anc;, system analysis can be fo�ind in Appendix D.
The storm drainage conveyance system consists of a total of 5 catch basins and
approximately 342 lf of 12 inch diameter pipe. The system will collect runoff from the
street and convey it to the proposed detention tank. A delineation of the draina�e area to
� each catch basin can be found at the back of this report. Due to the short travel length to
each catch basin, a minimum time of concentration of 6.3 minutes will be used in the
'� Rational Method analysis of the conveyance system. The rational method analysis will be
far the 100-year storm event. Based on Figure 3.2.1.D, the 100-year, 24-hour precipitation
' depth for the project site is 3.9 inches. Far the runoff coefficient determination, the ,
M impervious areas will be assigned a c of 0.90 and all other areas ��ill be considered lawns 'i
with a c of 0.25. Runoff coefficient calculations can be found in Appendix D. The
Temnodel CAD program utilized for design and drafting of the proj ect includes a module
utilized for a rational method based analysis of the drainage to and performance of the
closed conveyance system. The resulting calculated hydraulic arade liiie can be fotmd on
the engineering plans.
� Bypass runoff will be collected in an interceptor s«ale sized for the lU0 year e��ent based on
a rational method analysis. A detailed analysis can be found in Appendix F.
Section 6 — S�ecial Reports and Studies
A limited �eotechnical report for this project has been pr�pared b�� AGRa Earth &
` Environmental, Inc.
� Section 7 — Other Pei•mits
�Io other pei�nits are lalo«n to bc raluired.
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-_]izabrtl; P:ace .�:�ri: :�. ?UJO P�• 9 �_;; . 1
Cir;:in:��, R:,�ort �
Section 8 — ESC �nalvsis and T�esian
Clearing Limits
Clearing limits will be delineated on the west by silt fence with survey flagging and on the
north�vith a continuous length of survey flagging on posts. Existing public roads to the east
and south will naturally limit clearing and grading.
Cover Measures
Temporary cover will be installed if an area is to remain unworked for more than seven days
during the dry season (Nlay 1 to September 30) or for more than ri�ro days during the wet
season (October 1 to Apri130.) Mulch will be utilized for temporary cover. Permanent
cover will be installed in any area that will remain unworked for more than 30 days.
� Permanent cover will consist of seeding.
Perimeter Protection
� Silt fence will be installed along the west boundary of the grading limits to provide
E perimeter protection. Surface water controls will ensure that only runoff from narrow
f portions along the western and northern grading limits will drain directly to the silt fence.
Traffic Area Stabilization
' A temporary construction entrance of 4"-8" quarry spalls 12" thick will be provided at each ,
proposed access to existing public roads in order to reduce the amount of sediment tracked
� offsite by co�struction vehicles. j
� Sediment Retention
� I�early all drainage from the grading limits wi'1 be directed to a sediment retention device.
' The exceptions are noted above in the perimeter protection description. Since the drainage
( area is less than 3 acres, a sediment trap«-i11 be utilized to prevent sediment laden runoff
` from leavin� the project site. The proposed detention tank«rill be utilized as the sediment
� trap. The design storm for the sediment trap is the 2 year storm in developed conditions.
i See Appendix E for sediment trap sizing �alculations.
� Surface Water Controls
i Int�rceptor ditches will be installed in order to intercept runoff and direct it to the sediment
� trap. One ditch �vill be installed alon�the silt fence line. The other will be constructed on
tile east side of the proposed presettling basin in order to prevent runoff from bypassing the
sediment trap.
Dust Control
If it is determined that wind transport of soil is likely, during construction, water will be
used to control dust on the project site.
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F1i;-_ai;ct:i Place :�_�rii ._, �C;CG Pagc 1�J of 1 i
I���ain�a�e Report
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` Covenant
Bond quantity requirements ti�-il1 be determine� after revie�v of the project by the Cit�� of
Renton. Necessary estimates will be provided upon request by the Citv.
Facility summaries, if required by the City, will be submitted upon plan approval. I,
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A declaration of covenant, as required by the City, will be submitted upon request. I
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FiQures
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� Kir�� �.:�unty �epartr-:�r�: ��r aeveic,p���ent and �nvironmer�tal Servic�s
°���HI�;CA►L l�F���AT�OfV RE�C�RT �TIR) VIJ�DR�:S�iE�� ;
� Part 1 PROJECT OWNER AND � Part2 PROJECT LOCATION AND '
PROJECT ENGINEER I DESCRIPTION
Project Owner Project Name
Arcarius Homes Elizabeth Place ;
�
Address Location
� ' P.O. Box 257 Township 25N '
, Phone (425) 746-5471 Range 5E ,
Project Engineer .............Section 5 �
Paul E. Green '
Company LeRoy Surveyors & Enqineers, Inc. '
Address/Phone 1103 Shaw Road
Pu allup, WA 98372 ;
Part 3 TYPE OF PERMIT I Part 4 OTHER REVIEWS AND PERMITS
APPLICATION �
I� DFW HPA Shoreline Management
Subdivison I i
COE 404 Rockery
,: Short Subdivision DOE Dam Safety Structural Vaults �i,
',i Grading FEMA Floodplain Other '
' Commercial
il COE Wetlands
Other
: Part 5 SITE COMMUNITY AND DRAINAGE BASIN ' '
Community '
i City of Renton �
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I Drainage Basin i
I` East Lake Washinqton
Part 6 SITE CHARACTERISTICS
River Floodplain �
� Stream � Wetlands
Critical Stream Reach SeepslSprings
,' Depressions/Swales High Groundwater Table !
Lake Groundwater Recharge
t Steep Slopes Other �
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� �=i��ure 1 �?pri: 12,2000 Pa�e 1 of�
,-'v�. � , �raina��e Report
r,.�.ab::t;; _ ...�
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Part 7 SOlLS - — — --- --�
� Soii Type Slopes Erosion Potential Erosive Velcoties I
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' InC 4-15°/o stight to moderate 0.0018 ft/sec
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', InD 15-30% moderate to severe 0.0018 ft/sec
_ Additional Sheets Attached
Part 8 DEVELOPMENT LIMITATIONS
` REFERENCE LIMITATION/SITE CONSTRAINT
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❑ Additional Sheets Attached
Part 9 ESC REQUIREMENTS '
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS
, DURING CONSTRUCTION AFTER CONSTRUCTION
dimentation Facilities ilize Exposed Surfa
, tabilized Construction Entranc ove and Restore Temporary ESC Facilitie
erimeter Runoff Control lean and Remove All Silt and Debris
I Clearing and Grading Restrictions nsure Operation of Permanent Facilities
over Practices Flag Limits of SAO and open space preservation
onstruction Sequence areas
I ther Other
Fi�,ure 1 �,�ril '.�. 'OOU Pa��e ' 01,
Elizab�th Place Draina��� ?e�ort
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' ;'art 10 SURFA�� �rJATER SYS t Ef4'1 __-- ---- ------ ---- —'I
Grass Lined Channel Tank inriltra rc � Niethod of Analysis ,
ipe System Vault Depressior, Tank-KCRTS. Conveyance - ,
I Open Channel Energy Dissapator Flow Dispersai Rational method
Dry Pond Wetland Waiver Compensation/Mitigation of i
Eliminated Site Storage
Wet Pond Stream Regional Detention N�A
, Brief Description of System Operation Runoff from roof downspouts and some driveways will be ;
', controlled b�individual lot downspout infiltration system. Runoff from all other impervious surfaces and
portions of lots graded to streets wiil drain to the proposed pubiic road Surface runoff will drain alonq
curb and clutter to catch basins and then through a closed conveyance system into a detention tank/ '
I wetpond Runoff will discharge into the existinq closed conveyance in 12 St. restricted to predeveloped 2 ',
and 10 year runoff rates. '
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' Facility Related Site Limitations �,
Reference Facility Limitation
�: Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTS/TRACTS
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'; Cast in Place Vault i Drainage Easement
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Retaining Wall ' Access Easement
Rockery > 4' High Native Growth Protection Easement
Structural on Steep Slope ' act
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U Othec � Other ;
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Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I
I or a civil engineer under my supervision my supervision have visited the site. Actual site
conditions as observed were incorporated into this worksheet and ihe attachments. To the best of
my knowledge the information provided here is accurate.
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f
� ��PENllIX B
f
I
� Detention Tank Calculations
(
appendi�B a rrii ':�. =J�,i) Pa;e B 1 of-�
Elizabeth Place Drainagc R��:�����
Detenti«n Tank:�nalvsis
For t:ze KCRTS anaiysis of the detertion t�n1c, the drainage basin is delineated as follows:
Predeveloped Conditions:
Total Area=0.763 acres
�` Irnpervious area= 0.060 acres
` Out�vash Pasture= 0.703 acres
�
� Developed Conditions:
� Total Area=0.763 acres
� Impervious area= 0.507 acres
� Outwash grass =0.2�6 acres
i
The project site is located in the Sea-Tac rainfall region with a 1.0 scale factor. An hourly time
step and reduced record is used. ,
The resulting peak runoff rates for the predeveloped condition:
Flow Frequency Analysis
T�me Series File:lizpre.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- ----^low Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Pzob
(CFS) (CFS) Period
0 .022 2 2/09/O1 2 :00 0.032 1 �00 . 00 0.990
C . 013 8 1/05/02 16:00 0 .022 2 25 .00 0. 96C
C . 020 4 2/27/03 7:00 0. 022 3 10. 00 0.900
0 . 015 7 8/26/04 2 :00 0. 020 4 5.00 0.800
0 .018 5 10/28/04 16:00 0. 018 5 3 . 00 0.667
0.015 6 1/18/06 16:00 0.015 6 2 . 00 0.500
0 .022 3 10/26/06 0:00 0.015 7 1.30 0.231
:i . 032 _ 1/n9/p8 5:C0 n . G'3 8 1. 10 0. 091
�or�.�;�uted Peaks 0 . �?9 50 . 00 0 . 980
The resultin�peak nuloffrates for the developed condition:
Flow Frequency Aralysis
Time Series File:lizdev.tsf
?�o-ect Location:Sea-Tac
---P.r_nual Peak Flow Ra:es--- -----Flow Freauency Analysis-------
rio�.J Rate Rank Time of Peak - - Peaks - - Rank Peturn Prob
ICFS) (CFS) Period
0.131 6 2/09/O1 2 :00 0.258 1 100 . 00 0. 990
0. 108 8 1/05/02 16:00 0.184 2 25 . 00 0.960 '
0 , 158 3 2/27/03 7 :00 0.158 3 10 .00 0.900
� .126 7 8/26/04 2 :00 0.150 4 5 .00 0.800
� .150 4 10/28/04 16:00 0.132 5 3 .00 0. 667
0 .132 5 1/18/06 16:00 0.131 6 2 .00 0. 500
�. 184 2 10/26/06 0:00 0.126 7 1.30 C.231
Q.258 1 1/09%OB 6:00 0.108 8 1.�0 0.091
Ccmputed Peaks 0.233 50.00 0.980
_�ppendis B April 12,ZOOQ Page B2 of 4
Elizabeth Piace Draina2e Report
Decention Tanl:Analysis
i
The detentien tank is configured to provide adequate dead stora�e far �':1z �vet��._d :�::iuirenierts.
An orifice diameter of 0.042 is utilized. The resulting stage, storage, d:scharge data for�he t�:lc
is:
� One Outiet Reservoir Routing File
�
E Stage Discharge Storage Per;:1-Area
� (Ft) (CFS) (Cu-Ft) (Sq-Ft)
` 0.00 0 .000 0. 0 .
j 0.50 0 .005 166. 0 .
M 1.00 0.007 361. 0 .
I 1.50 0.008 574 . 0 .
` 2.00 0.010 796. 0 .
E 2.50 0 .011 1252 . 0.
3 . 00 0.012 1713 . 0 .
3.50 0.013 2170 . 0 .
4.00 0.014 2618 . 0 .
4.50 0.015 3049. G .
�.00 0. 015 3664. 0 .
5 .50 G . 016 4238 . G .
a.00 0.017 4763 . G.
0.50 0.018 5224. 0 .
7.17 0.018 5705 . 0 .
7.67 0. 019 5847 . 0 .
0 . 00 Ft : Base Reservoir Ele-�atior_
0 .0 Minutes/Inch: Average Perm-Rate
The developed runoff data is routed throuQh the tank �vith the resulting dischal��e data:
Flow Frequency Analysis
Ti-�e Series File:liztar_ko.tsf
Project Location:Sea-'�ac
---Frnual Peak Flo:•; Ra�es--- -----�'_c�.� Fre�ke.�c�•,- �_r_a-_ysis------
=icvr Rate Rank Time of Peak - - Peaks - - Rank Returr Prob
(CrS) (CFS) (ft} Period
v. 025 2 2/09/O1 20:00 0 .028 11.93 1 I00.00 0.590
0 . 014 8 12/28/O1 17:00 0 .025 10.7'0 2 25.00 0.9�0
O . C17 5 2/28/03 19:00 0 .018 7 .02 3 10 .00 0. 9U0
0 .014 7 8/26/04 6:00 0.017 6.24 4 5 .00 0. 8G0
0 .015 6 1/05/05 15 :C0 0. 017 6. 06 5 3 .00 O. Eo'?
0 .017 4 1/18/06 23 :00 0.015 4 . 85 6 2 .00 0.5�C
0.018 3 11/24/C6 5 :00 0. 014 3 .82 7 1.30 0 .23�
0.028 1 1/09/08 15:00 0.014 3 .77 8 1. 10 0 .091
Comp;:ted Peaks � .G�^ �� .51 �O . CO 0 . 980
The discharge rates far the 2 year and 10 �-ear storm events are at or beloti�� the prede��elope�d
runoff rates, as required.
�ppet]dis B :Arv�1i i- �'u:i�;1 Pa��,e f3� of=t
Eiizabeth Place Drainage Report
Detention Tanl::lnalvsis
f
i To ensure the total site di�char�-e does not exceed predeveloped conditions, runoff not draininQ
� to the detention tank was also caiculat�d. For exist:,zg conditiens, the remainde:-of the site is
� classified as O.S37 acres outwash pasture. W�hen runeff from thi� area is added to the
predeveloped runoff for the detention tank calculated above the results are:
Flow Frequency Ar_alysis
'�'ime Series File:predev.ts=
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 .031 2 2/09/O1 2 :00 0.042 1 100.00 0.990
� . 013 8 1/05/02 16:00 0.031 2 25.00 0.960
� .024 3 3/06/03 18 :00 0.024 3 10.00 0. 900
0. 015 7 8/26/04 2 :00 0.022 4 5 .00 0. 800
0 . 017 5 10/28/04 16:00 0.017 5 3 .00 0 .667
0 . 015 6 1/18/06 16:00 0 .015 6 2_00 0 .500
0 . 022 4 10/26/06 0:00 0.015 7 1.30 0.231
0. 042 1 1/09/08 9:00 0.013 8 i.10 0.09�
Computed Peaks 0.038 50.00 0.980
For developed conditions, 0.585 acres of roof area will be infiltrated by individual do�vnspout
infiltration trenches and 0.053 acres of drive��ay area«�ill be infiltrated by an infiltration trencll.
"Ihe remaining 0.199 acres is classified as outwash grass for the runoff calculations. The runoff
trom tl�is area is aci�ied to the discharge from the detention tank with the follo���in� results:
F--o�fr F-ecueac-, __�a_-✓sis
Time Series File:develop.tsf
?roject Location:Sea-Tac
---�nnual Peak Flow Rates--- -----rlow �requency l-�nal-ysi�-- ---
,low Rate Rank Time of Peak - - Peaks - - Rank Reti:r� Fro�
(CFS) (CFS) Per�od
0 .026 2 2/09/O1 20:00 0 .033 1 100.00 0. 9a0
0 . 013 7 12/28/O1 15 :00 0.026 2 25.00 O. �oO
0. 022 3 2/28/03 3 :00 0.022 3 lO.OG O. �Ou
0. 013 8 8/26/04 4 :00 0.018 4 5.00 0. 8�C
� . 015 6 1/05/05 9:00 0.017 5 3. 00 O.Go?
0 .017 5 1/18/06 21:00 0.015 6 2 . 00 0.5CC
0.018 4 11/24/06 5:00 0.013 7 1.30 0.2��
0 . 033 1 1/09/OS 9:00 0.013 8 1.10 0.091
Co:r,tiuted Peaks 0 . 031 5� .00 0 . 5�0
For the 2-year and lU-vear e��ents, the� total runotf f:om the site ec�uals rtinoff in e�isting
conditions, as required.
=`.��p�nd.:� B �pril �_'. =Ui;O }'��� B� o:-1
;_!izabeth Place Drainage Repo.t
i�r:�t��„���on T:_,ilcAnalvsis
� i
� A�'�ENDI� � I
�
�lVetpond Calculations
,
�
�
Appendix C Ae;`•i i�, ''GOQ Pa�7e C'' of 2
Eli�abeth Place
��Netpond Calcul�ticns
_ _ _
I
I
Section 6.4.1 describes the calculatiors and reGuirements for a wetpond used to provide w�ter
quality for runo�f. The foliowing calculatio�s�Nere done tc determine the required volume or
storage for the wetpond.
Wecpond volume factcr. f:_�
Rainfall depth, mean annual storm R :=0.-�7 incres
� Impervious Area: A;:=22085 square feet
� Outwash Grass Area: Ao:= 13416 square feet
R
Runoff from mean annual storm: �'_:_�0.9•.�: + 0.01�.A��•—
12
�" - ,�� ,�i :ubic feet
� Wetpool volume: �`�,:_'�,���r' ;
, V� = 2��i cubic feet
The wetpond will be made up of dead storage in the proposed detention tank. Of the three runs
of pipe that make up the tank, a total of 5 feet of dead storage will be provided in the first pipe
and 3.5 feet of dead storage in the second pipe. The bottom foot of dead storage in each pipe is
not included in the wetpond volume as this depth is provided for sediment storage. The dead
storage is created by placing the connecting pipes at the appropriate elevations to prevent runoff
from passing into the next run of tank. The total wetpond storage volume provided with the
proposed arrangement is 2387 cubic feet.
P,pF;endc: C April 12. 2COC Page C2 of 2
E�izabeth F;ace
�,Netoond Calculations
I
�
�
��PENI)IX D
S��rm Dra�� Report
=��pp�ndi�D ;1pri1 1�.'00(i P� ;� Di oi i-
i:lizabeth Place
Pipe Repor:
f -
E_Yi I.AN�TION OF STOR\�1 SEWER:'.tiALYSIS tc�PORT ���
TerraModel will create a report for storm%sanitary sewers which shows a?1 of the input and caiculated data
regarding flow in the se«er systems. A report is gen.erated for each branch. The data far each pipe segrnent is
� displayed over tt�o sheets. The branch name and pipe segment are displa}�ed at the top of each sheet. 1'he
� se;ments are displayed beginning at the downstream segment. Terratifodel completes all the calcularions,
including cumulative effects of intersecting branches. Generally,the flow data is calculated for the peak flo«- ,,
for the 100-year,24-hour storm event using the rarional method(Q=CIA)and the appropriate rainfall database !
for the region in which the project is located. Flo«�rates can be directly entered at each node if desired. �i
The first data sheet for a pipe segment consists of the data input for that pipe segment: downsiream node data,
pipe data,and upstream node data.
�ODE DATA: Informarion input by the user for nodes includes: rim elevation, floor elevarion, type and size of
node, area draining to the node, time of concentration, and the runoff coefficient for that drainage area. As
discussed above, TerraModel then calculates the flo���into the node using the rational method based on the input
data. '
PIPE DATA: Information input by the user for pipes includes: entrance and outlet elevarions,pipe type, shape, ,
and size, and entrance and outlet coefficients. From tables in the program,Terrai�lodel deterrnines the
�lanning's n for the type of pipe. The pipe len�th is deterniined by the location of the nodes. TerraModel
calculates the slope of the pipe and the flow configuration based on all the data input and calculated flows. This
data is printed on the second data sheet for the pipe segment.
Following is an explanation of the various pieces of data shown on the second sheet for each pipe segment: ,
Discharge: Cumulative discharee from the pipe outlet for that branch in cubic feet per second.
Total Area: Cumularive area draining into the pipe branch in acres. '
T� (max): Maximum time of concentration for the entire pipe branch in minutes.
Ho: Total head @ outlet from pipe segment in feet.
`t'o: Water surface elevation @,outlet from pipe segment in feet.
I'o: Water depth C outlet from pipe segment in feet.
\'o: Average velocity @ outlet from pipe segment in feet per second.
Y'n: Normal depth in feet.
�"c: Critical depth in feet.
Q max critical: Maximum discharge for a critical flow section in cubic feet per second.
V full flow(avg.): Velocity of flow through pipe��hen flowing full.
Flow Configuration type: See Terra�iodel Sew�er Design and Analysis manual for different flow configuration
codes.
��eighted C,'CT;: Runoff coefficient(for rational method)calculated for the cumularive drainage area.
Rainfall Intensiry: From storm database at rime of concentration in inches per hour.
Iie: Total head @ entrance of pipe seement in feet.
��:e: Water surface elevation @ entrance of pipe segment in feet. ,
T"e: �'Vater depth @ entrance of pipe segment in feet. '
�"e: Average velocity @ entrance of pipe segment in feet per second.
�-n: Average velocity @ a normal depth section in feet per second.
�%c: Critical velocity in feet per second.
Q ma:c normal: Maximum discharge for a normal depth section in cubic feet per second.
Yipe Flo�v time: Time of flow through pipe segment.
.� �vater surface profile beginning at the do«nstream end is also printed on the second data sheet far each pi��� '
s.;ment. This can be used to plot the H;�draulic Grade Line.
Sc�:t1-: _�-�a��Iodel.<�e�ver D?�:o,: a�;d_�.:al��si�"n�un:r;; for additional information.
:�pp:.�idir :, _�pri'i i', ?�J00 Pa��e D� ur 1-1
Llizaueth I'?ac=
Pt . iZ���i�� :i
i -------------- ------------ ----.---- --- -------
, .
�torm/Sanitary Sewer tir�alys�s Repo.rt
--------—-----------------------------------------------------------
� ?ranch name: STORM A PiFe: 1 of 3 I�
i',o�,J:zstream Node data: !
Node name: Node: 1 of 4
Node size: Transition P7ode shape: RECT/CONCRETE '
Node type: trans_tion Point number: 2433
Rim inlet elev: 298.409 ft Floor elev: 279.720 ft
C/Cn factor: 0.00 Drainage area: 0. 00000 acres
Rainfall intensity: 0.00 in/hr Q into node: 0.00 cfs
Node K factor: 0.00 Basin Tc: 0.00
Hi 287.910 ft Wi 287 .910 ft '
`�i ******** ft Vi 0.000 fps
Pipe data:
From point: 2433 To point: 243Q
Station: 60t00.40 To Station: 60+18 .78
Pipe name: STORM A-P1 Pipe shape: CIR/CMP
Pipe size: 12" Dia. Manning's n 0.024
Pipe length: 18.779 ft Pipe slope 19.969 % '
�ntrance elev: 290.250 ft Outlet elev: 286.500 ft
Sub. entrance coef. : 0.50 Sub. outlet coef . : 1.00
Free entrance coef. : 0.35 Free outlet coef. : 0.75 '
L;pstream Node data:
^�ode name: CB 1 Node: 2 of 4
�7ode size: TYPE 1 Node sha�e: RECT/CONCRETE
��ode type: box Point number: 2430
R_m inlet elev: 298.509 ft Floor elev: 288 .750 ft
C/Cn factor: 0.73 Drainage area: 0.09000 acres
Rainfall intensity: 3 .08 in/hr Q into node: 0. 00 cfs
`�ode K factor: 0 .00 Basin Tc: 6.30
I:i 291.082 ft Wi 291.081 ft
'_✓i � .3?1 �t Vi 0 .320 f�s
--�Pper.di� D �pril 1Z, 'O1;0 Fz���L: or_ :-- ',
Elizabeth Place I
:'ipe Repur[ I
` . _
�
Branch name: STCRM A Pipe: 1 �f 3
Discharge: 1.617 cfs Flow conf-guration ty�e: S36
Tctal area: 0.76800 acres Weighted C/CN: 0 .68
Tc (max) : 6.70 min Rain=all intensity: 3 .054 in/hr
i Ho 287.976 ft He 29�.007 ft
, Wo 287.910 ft We 290.790 ft
Yo 0.000 ft Ye 0 .540 ft
Vo 2 .059 fps Ve 3 .737 fps
Yn 0.293 ft Vn 8.434 fps
Yc 0.540 ft Vc 3 .737 fps
Q max critical 4.704 cfs Q max normal 9.301 cfs
` V full flow (avg. } : 6.691 fps Pipe flow time 0 .05 min
, Water surface profile
i ---------------------------------------------------------------------
, Distance depth Elevation Distance depth Elevation
(ft) (ft) (ft) (ft) (ft) (ft)
0 .00 ****** 287.910
0.10 1.410 287.930 9.21 0.300 288.675
0.56 1.321 287.934 9.67 0.301 288.769
� 1.01 1.231 287.936 10.12 0 .302 288. 863
� 1.47 1.142 287.940 10.58 0 .303 288.956
1. 92 1.052 287 .943 11. 03 0.304 289.050
2 .38 0.960 287 .944 11.49 0 .306 289.145
( 2 . 83 0 .294 287 .370 11. 94 0.308 289.240
` 3 .29 0.294 287.463 12.40 0 .310 289.334
� 3 .74 0.294 287.556 12.85 0 .313 289.430
4 .20 0.295 287.650 13 .31 0 .316 289.526
4 .65 0.295 287.742 13 .76 0. 320 289. 623
5 .11 0.295 287.835 14.22 0 . 324 289.719
5 .57 0.295 287.928 14.68 0. 330 289.818
� 6. 02 0.296 288.022 15 .13 0.336 289.91?
6.48 0.296 288.115 15.59 0.345 290.019
6. 93 0.297 288.208 16. 04 0.355 290 .121
7.39 0.298 288.302 16.50 0.369 290 .228
7.84 0.298 288.395 16.95 0 .389 290.341
8.30 0.299 288.489 17.41 0 .422 290 .467
8 .75 0.299 288 .581 17. 86 0 . 540 290 .677
-8. 78 2 . 331 29=. 08�
E
E
�
Appendi�D :1�ri: 1'. �OCO Page Da o:1-1 I
� Elizabeth Place
Pipe Reporr
�
�
Bra:!ch name: �'`CRi�I F Fipe: 2 ..� .,
' Downstream Node data:
Ncde name: CB 1 Node : � c- _
i•Iode sizz: ^YPE 1 Node shape: R.=CT/�G�TCRE';'E
� Node type: box Point r_umber: 2430
?im inlet elev: 298.509 �t Floor eiev: 288 .750 ft
C/Cn factor: 0.73 Drair_age area: 0.09000 acres
� �ainfall intensity: 3 .Q8 in/hr Q into node: 0.00 cts
Node K factor: O.GO Basin Tc: 6.30
I 3i 291.082 ft Wi 291. 081 ft
Yi 2.331 ft Vi 0.320 fps
Pipe data:
From point: 2430 To point: 2450
S�ation: 60+18.78 To Station: 60+37.51
Pipe name: STORM A-P2 Pipe shape: CIR/ADS (N-12)
Pipe size: 12" Dia. Manning's n 0.013
Pipe length: 18.731 ft Pipe slope 1.335 %
Entrance elev: 290.500 ft Outlet elev: 290.250 ft
Sub. entrance coef. : 0.50 Sub. outlet coef. : 1.00
Free entrance coef. : 0.35 Free outlet coef. : 0.75
Upstream Node data:
�dode name: CB 2 Node: 3 of 4
Dlode size: TYPE 1 Node shal�e: RECT/CONCRET�
Node type: box Point number: 2450
?im inlet elev: 296.573 ft Floor elev: 289.000 ft
C/Cn factor: 0.71 Drainage area: 0 .02000 acres
�ainfall intensity: 3 . 13 in/hr Q into node: O. CO cfs
'Iode K factor: 0. 00 Basin Tc: 6.30
�i 291. 132 ft Wi 291.132 ft
Yi 2 .132 tt Vi 0 . 139 fps
.��ppendix D April l-. „�U(i i'^,c�: �:�� _�f : �
}:�lizabeth Place
Pip�Rrpu:i
r
3ranc:: na*nP: STCiu�I � ri�e: � �� �
Disc_zarg2: G.0'43 cfs Flc:v conf-guration t�e: S20 I
`_'or.al area: 0.36800 acres Trleighted C/CN: 0.56 ',
�'_'c (max) : 6.0'S min Raintall �.nter:sity: 3 .130 inj"r_r I
� Ho 291.091 ft He 291.123 f�
Wo 291. 078 ft 'de 291.096 ft
` Yc 0. 828 ft Ye C .596 ft
� �io 0. 925 fps Ve 1.318 fps
`�n 0.267 ft Vn 3 .821 fps
, Yc 0.334 ft Vc 2 .799 fps
� max critical 4.704 cfs Q max normal 4.440 cfs
� V full flow (avg. ) : 1.089 fps P�pe flow time 0.26 min
�later surface profile
'� -------------------------------------------------------------------
Distance depth Elevation Distance depth Elevation
(�t) (ft) (ft) (ft) (ft} (ft)
0.00 2.331 291. 081
C.92 0. 828 291. 090 9.58 0.711 291.089
i.35 0. 822 291. 090 10 .02 0.705 291.089
1.78 0.816 291.090 10.45 0. 699 291.088
2 .22 0.811 291.091 10.88 0. 693 291.088
2 .65 0.805 291.090 11.32 0.687 291.088
3 .08 0.799 291. 090 11.75 0.681 291. 088
3 .52 0. 793 291. 090 12 . 18 0.675 291. 088
3 . 95 0.787 291.090 12 .62 0.669 291.087
4.38 0.781 291.089 13 . 05 0.663 291.087
4. 82 0.776 291.090 13 .48 0.657 291.087
5.25 0 .770 291.090 13 .92 0.651 291.087
5.68 0 .764 291.090 14 .35 0.645 291.087
0'.12 0 .758 291.090 14 .78 0.639 291.086
6.55 0 .752 291.089 15.22 0.633 291.086
6.98 0_746 291.089 15.65 0.627 291.086
7 .42 0.740 291. 089 16. 08 0.621 291.086
7 .85 0. 734 291. 089 16 .52 0.615 291.085
8.28 0.729 291. 090 16 .95 0.609 291.085
8.72 0. 723 291. 089 i7 .38 0.603 291.085
9. 15 0 . 717 LCJ'l. OHQ 17 . 82 C. 59o' 291.084
l� . ?� 3 . 132 �9= . i32 �
:Appendix D �_�ri1 1�. .__ '���J P�a��e D6 or 1-�
t�liaabeth Plac:-
Pipe Report
Branch name: STOP.M A Pipe: 3 of 3 I�
Downstream Node da�a:
Node name: C3 2 Ncde: � 3 cf a
Node size: TYPE 1 �ode shape: RECT/CO�I�RET�
� Node type: box ?c�_nt numoer: 2450
Rim inlet elev: 296.573 ft Floor elev: 289 .000 ft
C/Cn factor: 0.7i Drainage area: 0.02000 acres
� Rainfall intensity: � .13 in/hr Q into node: �'; .00 cfs
Node K factor: 0.00 Basin Tc: 6.30
Hi 291.132 ft Wi 291.1 2 ft i,
Yi 2.132 ft Vi 0 .139 fps
� Pipe data:
� From point: 2450 To point: 2426
� Station: 60+37.51 To Station: 60+70.03
Pipe name: S^_'ORM A-P3 Pipe shape: CIR/P�S (N-12)
Pine size: 12" Dia. Manning's n 0.013
Pipe lAngth: 32.518 ft Pipe slope 6.888 �
Entrance elev: 292 .740 ft Outlet elev: 290 .500 ft
Sub. entrance coef. : 0.50 Sub. outlet coef. : 1.00
Free entrance coef. : 0.35 Free outlet coef. : 0 .75
Upstream Node data:
rdode name: CB 3 Node: 4 of 4
Node size: TYPL 1 Node shape: RECT/CONCRETE
rdode t�pe: box Point number: 2426
3im inlet elev: 295 .740 ft Floor elev: 291.240 ft
CjCn factor: 0 .55 Drainage area: 0.34800 acres ,
P,ainfall intensity: 3 .15 in/hr Q into node: 0.00 cfs i,
Pdode K faccor: 0.00 Basin Tc: 6.30
Fii 293 .221 ft Wi 293 .221 ft
'si 1.981 ft vi 0 . 140 fps
,��pendis D April 12, 2;iG0 Ya�e D; cf 1-4
't=iizabeth Place
-i:� Repo,._
�'--....... :7ct"'.2 . ..._.'1.�:� -' =_�c� . _. C= ?
Discnarge: 0.602 cfs Flow configuration type: S_�
Total area: 0.34800 acres Weignted C/CN: C .5�
Tc (max) : 6.39 min Rain'ali intensity: 3 _ "��5 ir_,�r.--
Fo 291.148 ft fie 293 . 180 =t
Wo 291.127 ft We 293 . 063 it
Yo 0.627 ft Ye 0.323 it
�To 1.162 fps Ve 2.746 fps
Yn 0.172 ft Vn 6.701 fps
Yc 0.323 ft Vc 2 .746 fps
Q max critical 4.704 cfs Q max normal 10.08E cts i�
h V fuil flow (avg. ) : � . ?88 -ps Fipe 'low t-me 0 . 09 mir_ ,I
Water surface profile
--------------------------------------------------------------
Distance depth Elevation Distance depth Elevation
� (ft) (ft) (ft) (ft) (ft) {ft)
0.00 2 .132 291.132
0 .92 0.627 291.190 16.65 0.177 291.827
1.70 0.567 291.184 17.44 0.177 291.881 �i
2 .49 0.172 290.844 18.23 0.178 291.936 I
3 .28 0.172 290.898 19.01 0.179 291.992 ',
=� .06 0.172 290. 952 19. 80 0.180 292.047 �i
4 . 85 0.172 291. 007 20.59 0.181 292.102 I
5.64 0.172 291. 061 21.37 0. 182 292.158 '
6.42 0.173 291.116 22 . 16 0. 184 292.214
7.21 0.173 291.171 22. 95 0 . 185 292.269
8. 00 0 .173 291.225 23 .73 0 . 187 292.326
3.78 0 .174 291.280 24.52 0. 190 292.383
9.57 0 .174 291.335 25.31 0. �92 292.439
�0.36 0 .174 291.369 26 .10 C . 196 292.498
11.14 0 .17a 291.543 26.88 0.200 292.556
11.93 0_175 291.499 27.67 0.205 292.615
,_2 .72 0.175 291.553 28.46 0 .212 292.677 ,
13 .51 0.175 291. 607 29.24 0.220 292.739
14 .29 0.175 291.662 30.03 0.232 292 .805
15. 08 0.176 291.717 30. 82 0.252 292 .880
15 . 87 0 .176 291. 771 31.60 0 . 323 293 . 005
32 .52 1. 981 �53 .22,_
appendiY i _'•;�ril :'. ��JUi` Pa�e D� of 1� ''
Elizabeth Pla:e
r i�e Ret ort '
�eRoy Su�-veyors & Enaineers,
Inc.
1103 Shaw Road
nuyallup, Wash,�zgtcn 983;2
i
253-848-6608
� `�cr. Mar 13 13 :21 :19 2 0 C 0
�
� Name of Project FROJECT:
i ��:\Jobs\5351\tmwin\LI20313 .prc
--------------------------------------------------------------------------
Storm/Sanitary Sewer Analysis Report
----------------------—------------------------------------------—-
Branch name: STORM B Pipe: 1 of 2
Downstream Node data:
Node name: CB 1 Node: 1 of 3
tiode size: TYPE 1 Node shape: RECT/CONCRETE
_�ode type: box Point nu[nber: 2430 '
Rim inlet elev: 298.509 ft F1cor elev: 288.750 ft
CjCn factor: 0.73 Drainage area: 0 . 09000 acres
Rainfall intensity: 3 .08 in/hr Q into node: 0. 00 cfs
_'Jode K factor: 0.00 Basin Tc: 6.30
Ei 291.082 ft Wi 291.081 ft
Yi 2.331 ft Vi 0.320 fps
=ipe data:
rrom point: 2430 To point: 2451
Station: 70+00.00 To Station: 70+95. 83
�ipe name: STORM B-P1 Pipe shape: CIR/CONCRET�
Pipe size: 12" Dia. Manning' s n 0.013
Pipe length: 95 .828 ft Pipe siope 17 .198 %
3ntrance elev: 306.730 ft Outlet elev: 290 .250 ft
�ub. entrance coef . : 0.50 Sub. outlet coef. : 1.00
Free entrance coef. : 0.35 Free outlet coef. : 0 .75
LTpstream Node data:
::cde name: CB 4 Node: 2 of 3
'_;ode size: TYPE 1 Node shape: RECT/CONCRETE
`dode type: box Point number: 2451
Rim inlet elev: 311.730 ft Flcor elev: 305.230 ft
C;Cn factor: 0.78 Drainage area: 0.20000 acres
Rainfall intensity: 3 .11 in/hr Q into node: 0 .00 cfs
tdode K factor: 0.00 Basin Tc: 6.30
��i 307 .28b =t '�Vi 3a7 .285 ft
'i'i � . �55 =t -. _. � .175 f-'�s
tippendi��D �pril 1�?, 2000 Yaee D9 of l�l ��
�lizabeth Place �
Pi:;:R� _. '
3r��c: r_am;: . ST�F:. �, _ - . 1 �f �
Discharge: 0.?87 c�s Flow ccnriguration t-_v-pe: S22
Total area: 0.31000 acr2s Weighted C/CN: 0.81
Tc (ma:c) : 6.66 min 3ainfall intensity: 3 .112 in;%hr
Ho 291. 096 ft He 307 .238 fL
Wo 291.076 ft We 307 .101 ft
Yc 0. 826 ft Ye 0 .371 f�
Vo 1.134 fps Ve 2 .971 fps
Yn 0.157 ft Vn 10. 009 fps
Yc 0.371 ft Vc 2 .971 fps
Q max critical 4 .704 cfs Q max normal 15 . 936 cfs
;� V full flow (avg. ) : 9.377 fps Pipe flow t_me 0 . 17 min
Water surface profile
I! ------------------------------------------ - -
� Distance depth Elevation Distar_ce depth Elevation �
(ft) (ft) (ft) (fti {ft) (fti ,
0 .00 2 . 331 291.081 '
0 .92 0. 826 291.233 49.12 0.156 298 . 975 ,
3 .33 0.156 290.984 51.53 0.156 299.396 I
5 .74 0.156 291.405 53 .94 0 .156 299. 816 ,
8 .15 0 .156 291.825 56.35 0 .156 300.237
10 .56 0.156 292.246 58.76 0 .157 300.658
12.97 0.156 292.666 61.17 0 . 157 301.079 I
15.38 0 .156 293 .087 63 .58 0.157 301.499 'i
17 .79 0.156 293 .507 65.99 0 . 158 301. 921 I
20.20 0.156 293 .928 68.40 0. 158 302 .342 �
22.61 0.150' 294.349 70.81 0. 158 302 .762 ��
25. 0� 0 . 156 294.769 73 .22 0. 158 303 .183
27.43 0 .156 295. 190 75.63 O. i59 303 _604
29.84 0 .156 295. 610 78.04 0.160 304 .026
32 .25 0 .156 296. 031 80.45 0.162 304 .448
�4.66 0.156 296.451 82. 86 0_164 304 . 871
37.07 0. 156 296.872 85.27 0.169 305.297
39.48 0. �56 297.293 87 .68 0.175 305.723
41. 89 0 ."_56 297.713 90 .09 0.187 306.156
44 .30 0.156 298 .134 92 .50 0.213 306.602
46.71 0 . 156 298 .55: 94 .91 � .371 307.181
95 .83 2 .055 307 .285
:lppendi�.D �pril 1�. ��;i��C' Page D10 0= 't=1
Elizabeth Pi«ce
oit,c R�por.
Branch name: STORP9 B Pi,e: 2 of �
Downstream Node data:
� _T7ode name: CB Y Ncd�: � o: 3
`dode size:. TYPL � P7<�de shap2: BE�T/CONCREi�
`dode type: box Point number: 245�
Rim inlet elev: 311.730 ft Floor e=ev: 305 .230 ft
C/Cn ractor: 0.78 Drainage area: 0.20000 acres
Rainfall intensity: 3. 11 in/hr Q into node: 0.00 cfs ,
Dlode K factor: 0. 00 Basin Tc: 6.30
Hi 307.286 ft Wi 307 .285 ft �
Yi 2. 055 ft Vi 0 .176 fps
Pipe data:
From point: 2451 To point: 2452
Station: 70+95.83 To Station: 71+26. 02
Pipe name: STORM B-P2 Pige shape: CIR/CONCRETE
Pipe size: 12" Dia. Manning' s n 0.013
Pipe length: 30 .197 ft Pipe s'lope 2 .186 %
Entrance elev: 307.390 ft Outlet elev: 306.730 ft
Sub. entrance coef. : 0.50 Sub. outlet coef. : 1.00
Free entrance coef. : 0.35 Free outlet coef. : 0 .75
Upstream Node data:
"dode name: CB 5 Node: 3 of 3
�dode size: TYPE 1 Node shape: RECT/CONCRETE
Node type: box Point number: 2452
Rim inlet elev: 312 .394 ft Floor elev: 305 . 890 ft
C/Cn factor: 0.88 Drainage area: 0. 11000 acres
Rainfall intensity: 3.15 in/hr Q into node: 0.00 cfs
_7ode Y: factor: 0.00 Basin Tc: 6.30
Hi 3�7.725 ft Wi 307.725 ft
Yi 1. 835 ft tTi 0 . 0?6 f�s
�ppendis i; �pr:l :%. �OQO 1'a��z D1� oC 1-1
Elizabeih F+ace
i'i,.,e:tZ�rort
Branch name: STGRM B Pipe: 2 of 2
Discharge: 0.30a cfs rlow con=iguration t�,rpe: S22
Total area: 0.11000 acres Weighted C/CN: 0.88
Tc (max; : 6.49 min Rainfall intens�ty: 3.145 in/hr
( �0 307.291 f} He 307.697 ft
?�10 307.283 f� We 307.617 ft
io 0.553 ft Ye 0.227 ft
Vo 0.682 fps Ve 2.268 fps
Yn 0.163 ft Vn 3 .655 fps
Yc 0.227 ft Vc 2.268 fps
Q max cr�tical 4.704 cfs Q max normal 5.681 cfs
V full flow (avg. ) : 2.482 fps Pipe flow time 0.19 min
�vater surface profile
---------------------------------------------------------------------
�istance depth Elevation Distance depth Elevation
lft) (ft) (ft) (ft) (ft) (ft)
0 . 00 2.055 307.285
0 . 92 0.553 307.303 15.46 0.165 307.233
1 .64 0.537 307.303 16.19 0.165 307.249
? .37 0.521 307.303 16.92 0 . 165 307.265
3 . 10 0.504 307.302 17 .64 0.165 307.281
S . B2 0.488 307.302 18.37 0.165 307.297
4 .55 0.471 307.301 19.10 0.166 307.314
5 .28 0.454 307.299 19.83 0 .166 307.329
6. 01 0.438 307.299 20 .55 0 .167 307.346
5 . 73 0.4"�1 307.298 21.28 0. 168 307.363
7 .46 0.403 307.296 22 . 01 0. 168 307. 379
8 19 0.386 307.295 22 .74 0. 169 307.390'
8 92 0.368 307.293 23 .46 0. 171 307 .414
9 . 64 0.350 307.291 24.19 0.172 307 .431
10 .37 0.331 307.288 24.92 0. 174 307.449
�1.10 0.311 307.284 25.65 0. 176 307.467
�1 . 83 0 .164 307.153 26.37 0. 179 307.486
'�2 .55 0 .164 307.168 27.10 0.163 307.505
13 .28 0.164 307.184 27.83 0. 188 307.526
14.01 0.165 307.201 28 .55 0.197 307.551
14 .?3 C . lES 3C'7.217 29.28 0.227 307.597
�0 .20 1. �35 307.725
Appendix D April 1?, ?000 Pa��e D'�_� o�I1
Llizabeth Plac::
Pipe Report
Followii�g is the intensiry-duration data table utiiized�y Te:ramcdel to determine the rainfall
intensity for the rational method calculations.
� -------------------------------------------------------------------
I File: PCZONE4.RNF
� Description: This file contains t':e Pierce County Zone 4 rainfall
� I database for use with HYDRO in terraMODE�.
�
I LeRoy Surveyors & Engineers, Inc.
� 510 East Main, Suite H
� Puyallup, Washington
� �
� � (206) -848-6608
� ----------------------------------------------------- -----------
i
STORM FREQUENCY (Years)
T�ME -------------------------------------------------------------
2 5 10 25 50 100
( ----------------------------------------------------------------------
5 .0 1.34 1. 94 2 .27 2.73 3 .05 3.40
6 . 0 1.27 1.80 2.15 2.56 2.84 3 .20
7 . 0 1.21 1.70 2 .02 3.42 2 .69 3 .03
8 . 0 1. 14 1.61 1.91 2.29 2 .53 2 . 87
9. 0 1. 09 1.53 1.83 2.16 2 .43 2 .74
10 . 0 1.05 1.46 1.75 2.10 2 .32 2 .60 �
11. 0 0 .99 1.39 i. 'o5 1.98 2.20 2 .47 I
12 .0 0.94 1.32 �..56 1.93 2.09 2 .34
1.3 .0 0.90 1.26 1.49 1.79 2 .00 2 .24 '
1� .0 0.86 1.20 1.42 1.70 1.91 2 .15
15 .0 0.82 1.15 1.35 1.62 1.82 2 . 05 I
::C .O 0.69 0.96 1.14 1.37 1.52 1.72 I
25 .0 0 .59 0. 84 0.98 1.18 1.32 1.49 '
30 .0 0 .52 0.74 0.87 1.04 1.17 1.32 I
40 . 0 0 .44 0.62 0.73 0 .87 0.98 1.10 I��
50 .0 0 .38 0.53 0.62 0 .74 0.83 0 .93 '
60 .0 0.34 0.47 0.55 0 .65 0.73 0 .82 i
120 ,0 0.21 0.29 0.30 0.35 0.41 0.47 �
180 .0 0. 16 0.22 0.25 0.30 0.33 0.38 '
240.0 0 . 13 0.18 0.21 0.24 C.27 0.31
�00. 0 0. 11 0.15 0.17 0.21 0.23 0.2E
360. 0 0 . 09 0 .13 0.15 0.18 0.20 0.�2
480. 0 0.07 0 .10 0.12 0.14 0.16 0 .12
E00. 0 0.06 0 .08 0.10 0.12 0.13 0.15
720. 0 0.05 0 .07 0.08 0.10 0.11 0 . 12
�CSO . 0 0 .04 0 . 05 Q. 06 0. �? 0 . 08 0 . 0�
,i��C . 0 0 . 03 0 . 04 i; . 05 0. �5 � . Oo 0 . 07
� The fc_i�•,rina is �_e _��a� �a;_nfal,� foY � and ? _ :�ours
�OT�L
o . � _ . 5C 1 . �� � . �., � . RC 3 .C� 3 .4G
'' = 0 2 . � � _ .4� � . 8� 3 .�G _ .�� 3 .9C
=�PPendil_ :1.,:il ?? =COC . �D 1� o t 1 :
L:lizabeth P?a,e
;�;nc,".�r.o.t
��::�e foi?����:n� table sii:�r_arizes the�veiahted runoff coefiici•�nt calcuiatio^�s for each catc�
basin. Irnpen�ious surfaces a:e assi�ned a value of 0.90 whi?e la�y�r.s are assigned a value «f
0.2j. �ome draira�e areas do not include the roof area of certain lots. Roof areas will be
� routed to individual lot do�vnspout infiltration trenches.
�
ELIZABETH PLACE STORM DRAIN '
3/9I00
CP 0.900 CR 0.9 CL 0.250
CB DRAINAGE NUM. SUBTRACT SUB. TOTAL ROAD DRIVE- LANDSCP'D IMP. AVG. Tc
AREA LOTS ROOFLOTS ROOFAREA AREA AREA WAY AREA AREA C
C61 0.09 2 0 0.000 a.090 0.043 0.023 0.024 0.066 0.726 6.30
C62 0.02 0 0 0.000 QA20 0.014 0.000 0.006 0.014 0.705 6.30 i
CB3 0.52 5 5 0.172 0.348 0.103 0.057 0.187 0.160 0.550 6.30 I,
CB4 0.2C 5 0 0.000 0.200 Q.107 0.057 0.036 0.164 0.784 6.30 '
CBS 0.14 1 1 0.034 0.106 0.091 0.011 0.003 0.102 0.881 6.30 I�
SUBTOTAL 0.97 13 6 0.207 0.763 0.358 0.149 0.256 0.507 0.682 -1
���_pp�ndit D April i_', =i)CQ P�c��D 1;� c� i-,
i'lizabeth Place
Pi��e Renort
I
�
� APPENDIX E
�
i
Sediment Trap Calculations
Apperdix E Anr i �z, 2000 Page -' of 2
E�izabeth PIacE Craio:�ge �-,epo�`
S�d+ment Trap Calcuie�.lcr,s
In order to prevent sedimen; laden runcff from leaving the project site while
under construction, a sediment trap will be installed. Nearly all runoff will be
directed to the sediment trap either by natural drainage or via interceptor
swales. The sediment trap design is based on requirements in section
, D.4.5.1. The surface area of the trap is based on the settling velocity of
F suspended solids in the runoff and the peak runoff Yata for the two year storm
event in developed conditions. The drainage analysis for quantity control did
not include the rear yard areas for Lots 7-17. During construction these
areas will be routed to the se��;iment trap, so a separate KCRTS analysis is
made to determine the design runoff rate. The sediment trap drainage area
has been delineated as 0.507 acres impervious and 0.738 acres outwas
grass in developed conditions. The resulting peak flows are:
Flow Frequency Analysis
Time Series File:lizsed.tsf
Project Location:Sea-Tac
--Annual Peak Flow Rates�-- �----Flow Frequency Analysis�------
F.ow Rate Rank Time of Peak � - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.146 5 2/09/O1 2:00 0.292 1 100.00 0.990
0.108 8 1/05/0216:00 0.184 2 25.00 0.960
0.181 3 2/27/03 7:00 0.181 3 10.00 0.900
0.126 7 8/26/04 2:00 0.150 4 5.00 0.800
0.150 4 10/28/0416:00 0.146 5 3.00 0.667 ;
0.133 6 1/18/0616:00 0.133 6 2.00 0.500
C.184 2 10/26/06 0:00 0.126 7 1.30 0.231
0.292 1 1/09/O8 6:00 0.108 8 1.10 0.091
Computed Peaks 0.256 50.G0 0.980 '
2-year peak runoff rate per KCRTS analysis: Q, :-�.133 cfs
Settling velocity required by D.4.5.1: VS:=0.00096 ft/sec
Safety Factor: FS:=2
,
Requirea surface area, equation: 5:�, :- k S �- SA= 277 square feet
�'-
The surface area at the �cp of dead storage in the detenticn tank is
approximately 870 square feet. Therefore, the detention tank meets the
design requirements for a sediment trap as required by D.4.5.1 .
P,;�?endix E April i 2. 2000 Pace .�2 0`?
E'iz�betn place Cr�.ir.uge Re�ort
SeJiment Trap Calculations
APf'ENDI)C F
�
i��ercept�r Swale �alc����a�ns
�
�
�
�
ru»e�cix F �.ii`i i�, _ ,� Page . i ci�
Eii�abeth Place Drainage Reoc;:
Interceptor Swale Calcuiations
In order to ensure that runof�from the site does not impact a.djacent properties, an
interceptor s��ale will be constructed along the�vest property line. This s��ale will
collect runoff from the site that does not drain into the proposed detention system.
The bypass drainage area will consist of the rear yards not draining to the roads and
the driveway for Lots 10, 11, and 12 as explained in section 2 of the drainage report.
' The proposed swale will discharge into the proposed closed conveyance system
� downstream of the outlet control structure. The follo�ving calcalations were made to
� size the interceptor s�vale.
TIME OF CONCENTRATION - Develoqed Conditions
The following calculation was made to determine the time of concentration to the interceptor swale
for the rationai analysis.
245 feet of flow over lawns
L: :=24� S1 :=0.113 kR1 :=7.0
LI
T :_
� �60•kR� Si� T� = 1.74 minutes
260 feet of flow thrcugh grassed swale
I:, :=�60 Sz :=0.04 k�, :=15.0 �I
L,
�I-, :_ -
- ���.�a` �1 T, = 1.44 minutes
v ,�
1: := L, - L, L =- �OS Feet
T,:—T: + T, T� _ ,.':� ���linutes
Tor Tc val��es calculated to be less thail 6.� mu�utes, a minimum value of 6.�
r;.inutes is assumed to be the time of concentration.
�f�.:=6.� Nlinutes
�
' 12, �JCO Pa�,�� F�of-1
�,-��en i;� - A.�r!,
!_:i�aueth Placa CrGinage Repo�t
:nt��rccptor Swale Caiculations
� NeYt, the unit�eak ra:nfall intensity factor is determined. The factors below are
rrom Table 3.2.1.B and are based or�a 100 ��ear storn frequency.
a,; :_�.51 bR:=a.63
llt•-3R�� rc �y��
�R = �.81y
Equation 3-3 is used to determine the peak rainfall intensity. Total precipitation for
the 100-year, 24-hour storm event is faund on Figure 3.2.1.D.
Ptoo�=3.9 inches
I:oo�=Pioo'�R
I;��o— 3.192 inches
The rational formula (Equation 3-1) is used to determine the peak flo�;� for the design
storm event. The drainage area consists of 0.199 acres of lawns and 0.053 acres of ,
drive��ay. '�
AL:=0.199 acres lawn area
AI:=0.053 acres driveway area
A:=AL+ A�
CL:=0.25 for lawns, from Table 3.2.1.A
C :=0.90 for impervious, from Taole 3.2.1.A
1-�:.���,. - _�:���)
C := � C = 0?�b;
A
Q�oo�=C'I�oo�.�
Q;,;�= 0.31 1 cfs
npperciX F /',Cr�' 1�. 20'.:��� F��e F3 Cf 4
�=!i�abe:i; p'��e Drairage Recor.
Interc�::;t��Sv��ale Calc.�la!ions
� SWALE DESIGN AND ANALYS3S
� The following calculations, based on�lanning's formula, are made based on the
� peak flow rate above to determine the required bottom width for a trapezoidal s��Tale
with 3 to 1 side slopes and a longitudinal slope of 4%.
d :=0.21 depth of flow in bioswale in feet
z :=3 1 side slopes of bioswale
b :=0 width of base of bioswale
a :_(b + z•d)•d Area of flow a = 0.132
p :=b + 2•d• 1 + z'` Wetted perimeter p — 1328
(b + z•d)•d
R := Hydraulic Radius R = 0.1
b + 2•d• l + z�
n :=U.027 Mannings Coefficient (short grass, from Table 4.4.1.6)
s :=0.�?-� Slope of swale
_ �
�.-�s� —
Q:=a� �R'�sZ Mannings equation for flow
t:
C� — 0.;13 Cubic Feet Per Second
_ i
` ._ I.��b R' s'" Mannings equation for velocity
I]
� _ =.;6� Feet Per Second
"I`herefore, a "v" shaped channel 0.21 feet deep is adequate to convey runoff from
tlle rear yards of the project. An additional half foot of freeboard ���ill be added for a
total s���ale d�pth of 0.;1 ie�t.
A,,.��n:"-: - !�pnl 1�, 2GU0 Pace F�l oi 4
_�._^.L6r�! " ..�6 �I'dIi'2C.; r�@DCf:
�,i��"•,.:,-.r0��'.!',liEi L,�d!CU�c"li:Of1S
i
C
APPENDIX G
Infiltration Trench Calculations
:lapendi:�G :�pril 1?. �0(��� pa�;: G I uf�
Elizabeth Place Drainage Report
Infutra:io�i Trench Calculations
I
For the KCRTS analysis of the infiltration trench, the drainage basin is delineated as
� follows:
� ^
Assumed Driveway Area= 2�00 square feet:
Impervious area= 0.053 acres
The project site is located in the Sea-Tac rainfall region with a 1.0 scale factor. An hourly
time step and reduced record is used.
Tlie resultin�peak runoff rates:
Floca Freai.:ency �r_alysis
Time Series F��e:dri•�reway.tsf
Project Location:Sea-Tac
---F,nr.ual Peak Flow Rates--- -----Flow Frequency Analysis-----—
Flo�r1 Rate Rank Time of Peak - - Peaks - - Rank Return Prob '
(CFS) (CFS) Period
0 . 013 7 2/09/O1 2 :00 0.025 1 100.00 0 .990
0 . 011 8 1/05/02 16 :00 0.019 2 25.00 0.960
0 . 016 3 12/08/02 18:00 0.016 3 10.00 0 . 900
�� . 013 6 8/26/04 2 :00 0.015 4 5.00 0 .800 '
0 . 015 4 10/28/04 16:00 0 .013 5 3 .00 0 .667
C.� . 013 5 1/18/06 16:00 0 .013 6 2 .00 0.500
0 . 019 2 10/26/06 0:00 0.013 7 1.30 0 .231
0 . 025 1 1/09/OS 6:00 0.011 8 1. 10 0 .091 I
Co:~.�Lted Peaks 0 . 0?3 50 . 00 C• . 98G
:�.p��:i�ii��G :�pt�il lZ, ?UU�J �'a��e G' ut;
i:lizabeth Place Dra;nage Report
!��;f;iYratio�:� i:ench Culcu?a*.:c;���.
The �.aiomati� sizing function of KCRTS is �.sed�o desi�:�the infiltratio�i trer,ch. �'iie ��
documen�ation file follows:
Retentior./Detention Facility
Type of Facility: Gravel Ir_filtration Trench
Facility Length: 39. 98 ft
Facility Width: 2 . 00 ft
Facility Area: 80. sq. ft
Effective Storage Depth: 4 .00 ft
� StGge 0 Elevation: 0 .00 ft ,
Storage Voiume: 96. cu. ft
"ertical Permeability: 30.00 min/in
Permeable Surfaces : Bottom
Riser Head: 4 . 00 ft
Riser Diameter: 12 .00 inches
Top Notch Weir: None
C�stflow Rating Curve: None
Stage Eleva�ion Storage Discharge Percolation
ft) {ft) (cu. ft) (ac-ft} (cfs) (cfs)
0.00 0.00 0. 0.000 0.000 0. 00
C .06 0.06 1. 0.000 0.000 0. 00
C .16 0.16 4. 0.000 0.000 0.00
0 .26 0.26 6. 0 .000 0. 000 0.00
0 .36 0.36 9. 0 .000 0. 000 0 . 00
0 .46 0.46 11. C.000 0. 000 0 . 00
C .56 0 .56 13 . C .000 0.000 0. 00
C .66 0.66 lo'. 0.000 0.000 0 . 00
G .76 0.75 18. d.000 0.000 0.00
G .86 0.86 21. 0 .000 0.000 0 .00
0 .96 0.96 23. 0.001 0.000 0 .00
_.06 1.06 25. 0.001 0.000 0 .00
i. 16 1.16 28. 0.001 0.000 O . CG
� .26 1.26 30. 0.001 0.000 0 . 00
1 .36 1.3'0 33 . 0.001 0.400 0. 00
_.-'_6 1.46 35. 0.001 0.000 0 .00 '
1.�6 1.56 37. 0 .001 0. 000 0 .00
1 . �6 1.66 4C . 0 .001 0 .000 0 .00
1 .76 1.76 42. 0 . 001 0 .000 0.00
1 . 86 1.86 45. 0.001 0 .000 0.00
1 . 96 1.96 47. O .001 0 .000 0.00
� . 06 2 . 06 49. 0.001 0 . 000 0.00 �',
� . 16 2 .16 52. 0.001 0. 000 0 .00 �
2 .26 2 .26 54. 0.001 0. 000 0 .00
2 .36 2 .36 57. 0.001 0. 000 0 .00 '
� .'6 2 .46 59. 0 .001 0. 000 O .00
? . 50 2 . 56 61. 0 .001 0.000 O .00
- . 66 2 . 66 64. 0 .001 0.000 O.00
: . 76 2 . 76 66. 0 .002 0.000 O .00
2 . 86 2 .36 69. C .002 0. 000 0 . 00
2 . �6 2 .56 71. 0 .002 0.000 O . GO
� . 06 3 .06 73. O.Q02 0. 000 0 .00
_`.ppenditi G �pril 12,2000 ,,� e _:_' ci�
Elizabeth Place Drainaee Repe�t
Infiltration Tr�nch Calculatiotls
3 .�6 3 . "_c �6. � . 002 _ . �UC C . CC
I 3 .26 3 .26 78. 0.002 0.000 O.CG
' 3 .36 3 .36 81. 0.002 0.000 O. OG
3 .40' 3 .46 83. 0.042 O. 00Q O. CC
3 .56 3 .50 85. 0 .002 0. 000 O.00
,� 3 .66 3 .66 88. 0.002 0.000 O.00
3 .76 3 .76 90. 0.002 0.000 0. 00
3 .86 3 .86 93 . 0.002 0.000 0. 00
3 .96 3 .96 95. 0 .002 0.000 0. 00
4 .OQ 4.00 96. 0.002 0.000 0.00
4 .10 4.10 96. 0.002 0.308 O.OG
4 .20 4.20 96. 0. 002 0.871 O. 00
� .30 4.30 96. 0. 002 1.600 O. 00
= .40 4.40 96. 0 . 002 2 .390 0. 00
� .50 4.50 96. 0 .002 2 .670 0. 00
4 .60 4.60 96. 0.002 2.930 0. 00
� .70 4.70 96. 0.002 3 .160 0.00
4 .80 4 .80 96. 0. 002 3 .380 0.00
� . 90 4.90 96. 0.002 3.590 0.00
5 .00 5.00 96. 0 .002 3.780 0.00
5 .10 5 .10 96. 0 .002 3 .970 0.00
5 .20 5 .20 96. 0.002 4.140 0. 00
5 .30 5.30 96. 0.002 4.310 0. 00
5 .40 5.40 96. 0.002 4.470 0.00
5 .50 5.50 96. 0 .002 4.630 0 .00
� . '00 5.60 96. 0 .002 4 .780 0. 00
5 .70 5.70 95. 0.002 4.930 0. 00
5 . 80 5. 80 96. 0.002 5.070 0. 00
5 . 90 5.90 95. 0. 002 5 .210 0.00
0 . 00 6.00 95. a .002 5 .350 0.00
�•_-d Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft?
1 0 .02 ******* 0. 01 4 .00 4. 00 96. O . CG2
2 0 . 01 ******* 0.01 4.00 4. 00 96. 0 .002
3 0. 02 0 .00 0.01 4.00 4. 00 96. 0 .002
1 0. 02 ******* 0.01 4.00 4.00 96. O .Q02
5 0. 01 F****** 0.00 2 .63 2.63 63 . 0.00,�
6 0.01 ******* 0.00 3 .16 3 .16 76. 0.002
7 0.01 ******* 0.01 4.00 4.00 96. 0.002
� 0 . 02 ******* C .02 � .Ol 4 . 01 96 . 0 .00?
A facilit}� area of SO �quarz feet is rec�uired for the infiltration trench. .�n in;iltration trench
?�) fcct lon�. -� teet��i�ie a�.d -� feet d2ep ���ill be illstalle�.
:�ppendi:�G _�prii 12,?000 Pa�e ��-� of�
Elizabeth Place Drainage Report
Irfiltratiot:TrencL Ca::,�:l::tio;:s
To ensure the total sit-� dischar�e dces not exceed predeveloped conditions, runoff not
draining to the detent:on tank was also calculated. For existing condition� the remainder of
the site i� classified as 0.�3; acres ouri�vash pasture. �Vhen runoff from this area is added to
j the prede���eioped runof+fo.•the detention tank calculated above the results are:
( Flow Frequency Analysis
! Time Series File:predev.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 .031 2 2/09/O1 2 :00 0. 042 1 100.00 0.990
0_013 8 1/05/Q2 16:00 0. 031 2 25.00 0.960
0. 024 3 3/06/03 18:00 0. 024 3 10.00 0.900
0. 015 7 8/26/04 2 :00 0.022 4 5 .00 0 .800
0. 017 5 10/28/04 16:00 0.017 5 3 .00 0.667
0. 015 6 1/18/06 16:00 0.015 6 2.00 0 .500
0. 022 4 10/26/06 0:00 0.015 7 1.30 0 .231
0. 042 1 1/09/08 9:00 0. 013 8 1.10 0 .091
Computed Peaks 0. 038 50 . 00 0.980
For developed conditions, 0.585 acres of roof area will be infiltrated by individual
downspout infiltration trenches and 0.053 acres of driveway area will be infiltrated by an
infiltration trench. The remaining 0.199 acres is classified as outwash grass for the runoff
calculations. The runoff from this area is added to the discharge from the detention tank
w:�h the follo��-ing results:
:low Freauency Ar_alysis
Time Series rile:develop.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
='-_o�v Ra�e Rank Time of Peak - - Peaks - - Rank Return Prob
(CrS) (CFS} Period
`�� . 026 2 2/09/O1 20:00 0.033 1 100. 00 0. 990
0 . 013 7 12/28/O1 15:00 0.026 2 25.00 0 . 960
0 . 022 3 2/28/03 3 :00 0.022 3 10.00 0. 900
0 .013 8 8/26/04 4 :00 0 .018 4 5 .00 0. 800
0 .015 6 1/05/05 9:00 0 .017 5 3 .00 0.667
0. 017 5 1/18/06 21:00 0 .015 6 2 .00 0.500
0.018 4 11/24/06 5 :00 0 .013 7 1.30 0.231
0. 033 1 1/d9/OS 9:00 0 .013 S 1.10 0.091 '
�cmputed Peaks 0 . 031 50 .00 � .98C
For tl�� �-year anc; :0-�;ear eveilts, the `�tal rui�otl fron� tl�e site equals runoff in elistiil�,
conditions, as required.
:�pp�nci� � �pril 1�, �OUO Fa�>e G� o;�_
E;izabeth Place Drainage Report
?•�'tiltr��io,i Trench Calculations