HomeMy WebLinkAbout03351 - Technical Information Report - Drainage ! �
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�T�RMA SHORT PLAT
2216 EDMONDS AVE NE
` RENTON, ,WAu�HZNGTON
FILE NO. 917-001-051 �
PRE PARE D BY
TOUMA ENGINEERS
6632 SOUTH 191ST PLACE , SUITE E-102
KENT, WA. 98032
(425) 251-0665
July 17 , 2006
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�il TABLE OF CONTENTS
I. PROJECT OVERVIEW
IL CONDITIONS & REQUIRiti1ENT SUSNiMARl' �
IIL Of�l�-51�1'E ANALYSIS I�
IV. FLOW CONTROL ANll WATER QU;�LI`I'l I
V. CONVEYANCE SYSTENI ANALY�1�
VI11. OTHER PERMITS
IX. ERO510N/SEDMINTATION CONTROL DESIGN
X. BOND QUANITIES WORKSHEET
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1. PROJECT OVERVIEW
This project consists of two parcels of land approximately 0.74acres. The project is situated in the
northeast end of the City of Renton. It is located within southeast quarter of Section 4 Townstiip
23 North, Range 5 East W. M. The proposal is to create a total of 4 lots, "Fill in" subdivision.
Access to the proposed project will be via from NE 23rd Street situated north of the property.
There are two existing homes on the property to remain.
The soils on the site are composed of Alderwood (AgC) gravelly and loom fine sand per the King
County Soil Survey. The Alderwood series is made up of somewliat moderate drained soils that
formed under conifers in sandy, recessional and stratified glacier drift. This type of soil is
designated by King County as Type C soil and is good for infiltration systems.
The site is flat with an average slope of 2 to 4 percent. There are no steep slopes present on the
site. The flow consists of sheet flow from north to south and to the west toward Edmonds
Avenue. There exists storm system on Edmonds Avenue NE and NE 23"�Street consisting of
underground pipes, which will serve portion of the proposed short plat
The proposed development of the property is considered as "infill" project and it is located in a
Single Family (SF) zone. The City of Renton designates the site with the Sf zoning. The SF
zoning allows for a rninimum lot size of 5000 square feet and a maximum density of 8 units per
acre. The setbacks allowed in the SF zone are as follows: front _yard setbacks, 20 feet; rear _yard
setbacks, 20 feet, and side yards setbacks, 5 feet on all interior lots, and I S feet on corner lots.
The City of Renton Comprehensive Plan designates the site as Single-Family Residence, which is
consistent with present zoning.
The density for the developed portion calculates at 5.65 dwelling unit per net developed acre.
Approximately 0.03 acres (1399 square feet) of right of wil] be dedicated for widening NE 23"�
Street. Off-site improvements are required along the property frontage.
Majority of trees will be retained except for few deciduous which fall within the building envelope
of the proposed new lots.
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II. PRELIMINARY CONDITIONS SUMMARY
CORE REQUIREMENTS 1-5
CORE REQUIREMENT #1: DISCHARGE AT NATURAL LOCATION
The allowable outflows from the site will be discharged to its natural locations. The level I flow
control is calculated to match the developed peak discharge rate to the existing site condition
peak discharge for the 2-year and 10-year.
CORE REQUIREMENT #2: OFF-SITE ANALYSIS
A level one downstream analysis is a portion of this report. See the analysis later in this report ��,
below.
CORE REQUIREMENT #3: RUNOFF CONTROL
The increased peak runoff, due to any change in pervious conditions and increase of impervious
areas, will be attenuated using peak rate runoffcontrol in accordance with KCSWM , 2005
Edition. Initial calculation indicates there is no detention facility required. Please refer to attached
calculation.
CORE REQUIREMENT #4: CONVEYANCE SYSTEM
Conveyance system is minimal for this proposed short plat. Runoff from new homes will be
directed to existing storm system on adjacent streets. No new storm conveyance system is
anticipated for this project.
CORE REQUIREMENT #5: EROSION/SEDIMENTATION CONTROL PLAN
The erosion control plan will be designed using the King County storm manual. Silt fences will be
used to intercept silt laden material resulting from clearing and/or c�nstruction of short plat
improvements. These facilities will be adhered to minimize any impact to downstrea�l� or offsite
areas.
CORE REQUIREMENT #6 - MAINTENANCE AND OPERATION
i
N/A
CORE REQUIREMENT #7 -FINANCIAL QUARANTEES AND LlAF3[l,l I'Y
N/A
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CORE REQUIREMENT #8 —WATER QUALITY
The additional impervious surfaces subject to vehicular traffic added to this proposed short plat is
less than 5000 square feet, tlius exempted from design and installation of water quality tank or
pond or siinilar facilities.
SPECIAL REQUIREMENTS: THOSE APPLICABLE TO PROJECT
1. Critical Drainage Area - N/A
2. Compiiance with existing Master Drainage Plan - N/A
3. Conditions Requiring Master Drainage Plan - N/A
4. Adopted Basin or Community Plans - N/A
5. Special Water Quality Controls— N/A
6. Coalescing Plate Oil/Water Separators—N/A
7. Closed Depressions - N/A I
8. Use of Lakes, Wetlands, or Depressions for Detention - N/A
9. Delineation of 100 Year Flood Plain - N/A
10. Flood Protection for Type 1 and 2 Streams - N/A
1 1. Geotechnical Analysis and Report — N/A
12. Soils Analysis and Report — N/A
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IV. FLOW CONTROL AND WATER QUAL[TY
The following calculations conclude that the 100-year peak flow difference between the
pre-developed flow and post-developed flow is less than 0.1 cfs. ln accordance with 2005
King Count Surface Water Drainage Manual detention is not required.
The following calculations include:
Basin areas
Time series Computation
Flow frequency analysis.
CREATE a new Time Series
------------------------
Production of Runoff Time Series
Project Location: Sea-Tac
Computing Series : predev.tsf
Regional Scale Factor : 1.00 '
Data Type: Reduced
Creating Hourly Time Series File
Loading Time Series File:C:1KC_SWDM�KC_DATA\STTG60R.rnf ',
Till Grass 0.53 acres
Loading Time Series File:C:�KC_SWDMIKC_DATAISTEI60R.rnf : �,i
lmpervious 0.18 acres '
Total Area: 0.71 acres �
Peak Discharge: 0.197 CFS at 6:00 on Jan 9 in Year 8 II
5toring Time Series File:predev.tsf :
Time Series Computed
�I.
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KCRTS Command '
CREATE a new Time Series
------------------------
Production of Runoff Time Series
Project Location: Sea-Tac
Computing Series: dev.tsf '
Regional Scale Factor: 1.00
Data Type: Reduced
Creating Hourly Time Series File
Loading Time Series File:C:�ICC_SWDMIKC_DATA\STTG60R.rnf :
Till Grass 0.47 acres
Loading Time Series File:C:\KC_SWDMIKC_DATA\STEI60R.rnf :
lmpervious 0.24 acres
Tota1 Area: 0.71 acres
Peak Discharge: 0.213 CFS at 6:00 on Jan 9 in Year 8
Storing Time Series File:dev.tsf :
Time Series Computed
- 7
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
0.091 4 2/09/O1 2:00 0. 197 1 100.00 0. 990
0.063 7 1/OS/02 16:00 0. 112 2 25. 00 0. 960
0. 112 2 2/27/03 7:00 0. 095 3 10. 00 0_900
0.055 8 8/26/04 2:00 0.091 4 5. 00 0. 800
0. 069 6 10/28/09 16:00 0.088 5 3.00 0. 667
0.095 3 1/18/06 16:00 0. 069 6 2. 00 0.50��
0.088 5 11/29/06 3:00 0. 063 7 1. 30 0.231 i
0.197 1 1/09/08 6:00 0. 055 8 1. 10 0. 091 ,
Computed Peaks 0. 169 50.00 0. 98��
Flow Frequency Analysis
Time Series File:dev.tsf
Project Location:Sea-Tac
I
---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- `
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0. 100 9 2/09/O1 2:00 0.213 1 100. 00 0_ 990
0.073 7 1/OS/02 16:00 0. 122 2 25. 00 0. 960
0. 122 2 2/27/03 7:00 0. 105 3 10. 00 0. 900
0.069 8 6/26/04 2:00 0. 100 9 5. 00 0. 800
0.085 6 10/28/04 16:00 0. 100 S 3. 00 0.667
0. 105 3 1/18/06 16:00 0. 085 6 2. 00 0.500
0. 100 5 10/26/06 0:00 0. 073 7 1 . 30 0.231.
0.213 1 1/09/08 6:00 0. 069 8 1 . 10 0. 097
Computed Peaks 0. 183 Sn . nO 0. 98n
There is no detention required.
DifT�erence between 100-yr devel�ped and pre-developed conditions is less than 0. 1 cf's
Q= .213 - 0. 197 -- Olbcfs < .lOcfs
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V. CONVEYANCE SY5TEM ANALYSIS
The proposed storm system consists of roof drains from new and existing homes
extended to existing storm system on Edmonds Avenue NE. one 12-inch pipe
(double wall pipe) conveying runoff from the site.
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IX EROSION & SED(MENTATION CONTROL
T'he contractor shall instaU silt fences along the perimeter of the site as indicated on the
Temporary Erosion Sedimentation Control Plan
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LEVEL 1 ANALYSIS
FOR
VARMA SHORT PLAT
2216 NE 23aD STREET
RENTON, WASHINGTON
FILE NO. 917-001-051
pREPARED BY
TOUMA ENGINEERS '
6632 50UTH 191ST PLACE , SUITE E-102
KENT, WA. 98032
(425) 251-0665
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March 11 , 2006 ,����� ��,`�"��-,,
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I. PROJECT OVERVIEW
This project involves two single parcels of approximately 0 . 74
acres . The project is situated in the northeast end of the City
of Renton. It is located within northwest quarter of Section 4
Township 23 North, Range 5 East W. M. The proposal is to create
4 lots, "Fill in" subdivision. Access to the proposed project
will be from existing streets NE 23`r' Street . Ther_e exists two
homes, one on each of the subject parcels, and both homes will be
retained. The site is bounded on the west by Edmonds Ave NE, and
on the south and east with developed single family residence .
The soils on the site are composed of Indianola ( InC) loamy fine
sand per the King County Soil Survey. The Indianola series is
made up of somewhat excessive drained soils that formed under
conifers in sandy, recessional and stratified qlacial drift . "T `
type of soil is designated t
good for infiltration systen
The site is flat for most o� �_.�� ���� �Y ., L �:� r:� :� � . � ,:�;::. _;�._�:�� ,. ,_ �
percent . There are no steep slopes greater than 40 percent noted
on the site. A ridge exists at approximately the existing
boundary line between two parcel considered in this short plat .
The easterly portion of the site drains to the east and surfacP
runoff is picked by existing underground storm system in NE 23 '
Street directing the flow to the east . The westerly portion of
the site drains to the west, and surface runoff is picked up hy
existing storm system in NE 23`' Street directing the flow to
storm system in Edmonds Avenue NE.
The proposed development of the property is considered as
"infill" project and it is located in a Single Family (SF) zone .
The City of Renton designates the site with the SF zoning. The �F
zoning allows for a minimum lot size of 5000 square feet and a
maximum density of 8 units per acre. The setbacks allowed in the
SF zone are as follows: front yard setbacks, 20 feet; rear yard
setbacks, 20 feet, and side yards setbacks, 5 feet on al1
interior lots, and 15 feet on corner lots . The City of Rerztoi�
Comprehensive Plan designates the site as Single-Farni ]_��%
Residence, which is consistent with present zoning.
The density for the developed portion calculates at 5 . 65 dweltinq
unit per net developed acre. Additional 5-foot right of way will
be dedicated. This dedication will provide 25-foot right widtt�
measured from the existing centerline on NE 23' ' Street to the
south margin of street. The dedicated area has been deducted frr�m
calculating he density. The proposed lots will be served by
existing NE 23�' Street. Off-site street improvements on NE �3 '
Street adjoinging the site will consist of curb, gutter and
sidewalks . Street widening will be built in accordance with City
Code requirements . Grading is very limited to construction of two
additional homes. The quantities of excavation for these homes
and roadway improvements on NE 23`� Street is estimated at 90 to
100 cu. Yd.
Several deciduous trees scattered within the west parcel . Those
trees that fall within the building envelope of the proposed new
lots will be retained.
- 3
I1. PRELIMINARY CONDITIONS SUMMARY
CORE REQUIREMENTS 1-5
CORE REQUIREMENT#1: DISCHARGE AT NATURAL LOCATION
The allowable outflows from the site wiii be discharged to its natural locations.
CORE REQUIREMENT#2: OFF-SITE ANALYSIS
A level one downstream analysis is a portion of this report. See the analysis later in
this report below.
CORE REQUIREMENT #3: RUNOFF CONTROL
The increased peak runoff, due to any change in pervious conditions and increase of
impervious areas, will be attenuated using peak rate runoff control in accordance with
KCSWM , 1998 Edition. Initial calculation indicates there will no detention facility
required. Please refer to attached calculation.
CORE REQUIREMENT#4: CONVEYANCE SYSTEM
Conveyance system is minimal for this proposed short plat. Storm runoff from the two
new homes will be directed to existing storm system located in NE 24th Street.
Infiltration systems may be used for the new homes.
CORE REQUIREMENT#5: EROSION/SEDIMENTATION CONTROL PLAN
The erosion control plan will be designed using the King County storm manual. Filter
fabric fences will be used to intercept silt-laden flow to protect downstream areas
- � "
SPECIAL REQUIREMENTS: THOSE APPLICABLE TO PROJECT
1. Critical Drainage Area - N/A
2. Compliance with existing Master Drainage Plan - N/A
3. Conditions Requiring Master Drainage Plan - N/A
4. Adopted Basin or Community Plans - N/A
5. Special Water Quality Controls— N/A
6. Coalescing Plate OiI/Vl/ater Separators —N/A
7. Closed Depressions - N/A
8. Use of Lakes, Wetlands, or Depressions for Detention - N/A
9. Delineation of 100 Year Flood Plain - N/A
10. Flood Protection for Type 1 and 2 Streams - N/A
11. Geotechnical Analysis and Report -N/A � I
12. Soils Analysis and Report -N/A
- 5
III. OFF-SITE ANALYSIS
CORE REQUIREMENT#2: OFF-SITE ANALYSIS
LEVEL 1 ANALYSIS
A: UPSTREAM ANALYSIS �
This ro osed sho�t lat does not have a reciable off-site runoff enterin the site.
P P P PP 9
B: DOWNSTREAM ANALYSIS
The flow from the site is oriented either east or north to existing underground storm
system exists in NE 23nd Street`. There exists a ridge along the existing boundary line
between the two existing parcels. The surface runoff for the easterly portion of the site
flows east and directed to existing storm system in the roadway. The flow is directed
east Duvall Avenue NE system. The surface runoff from the westerly portion of the site
flows west and directed to existing storm system in the roadway. The flow is directed
into Edmonds Avenue NE storm system which is then directed north.
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VARMA SHORT PLAT
Flow Frequency Analysis
Time Series File:predev.tsf
Project Location:Sea-Tac
r
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-�-----
� Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
� {CFS) {CFS) Period
0.093 4 2/09/O1 2:00 0.204 1 100.00 0.990
0.064 7 1/05/02 16:00 0.116 2 25.00 0.960
0.116 2 2/27/03 7:00 0.098 3 10.00 0.900
0.055 8 8/26/04 2:00 0.093 9 5.00 0. 800
0.070 6 10/28/04 16:00 0.091 5 3.00 0. 667
0.098 3 1/18/06 16:00 0.070 6 2.00 0.500
0.091 5 11/24/06 3:00 0.064 7 1.30 0.231
0.204 1 1/09/08 6:00 0.055 8 1. 10 0.007
Computed Peaks 0.174 50.00 0.9�3'i
Flow Frequency Analysis
Time Series File:dev.tsf
ProjecY_ Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0. 115 5 2/09/O1 2:00 0.240 1 100.00 O.Q9n
0.087 7 1/05/02 16:00 0.140 2 25.00 0.96n
0. 140 2 2/27/03 7:00 0.127 3 10.00 0. 90��
0.087 8 8/26/04 2:00 0.121 4 5.00 0.800
0.107 6 10/28/04 16:00 0.115 5 3.00 0.667
0. 121 4 1/18/06 16:00 0.107 6 2.00 0.50�
0.127 3 10/26/06 0:00 0.087 7 1.30 0.231
0.240 1 1/09/08 6:00 0.087 8 1. 10 O. OQ1
Computed Peaks 0.207 50.00 0. 990
The 100-yr storm difference is 0.2_4 - 0.204 = 0.09 cfs < 0. 1 cfs.
The is no detention required