HomeMy WebLinkAboutRS_TIR_Tran_190506_v1.pdfTechnical Information Report
Drainage Report
16654 113th Ave SE
Renton, Washington 98055
King County
P/N 0088000930
April 15, 2019
prepared for:
Sang Tran
16654 113th Ave SE
Renton, Washington 98055
(206) 680-5568
prepared by:
Migizi Group, Inc.
PO Box 44840
Tacoma, Washington 98448
(253) 537-9400
MGI Project P1239-T18
Technical Information Report
Drainage Report
16654 113th Ave SE
Renton, Washington 98055
P/N 0088000930
April 15, 2019
P1239-T18
Prepared For:
Sang Tran
16654 113th Ave SE
Renton, Washington 98055
206-680-5568
Prepared By:
Migizi Group, Inc.
PO Box 44840
Tacoma, WA 98448
253-537-9400
i
TABLE OF CONTENTS
Page No.
CERTIFICATION ........................................................................................................................................................ 1
INTRODUCTION/PROJECT REVIEW .................................................................................................................... 2
SECTION 1 .................................................................................................................................................................. 2
Existing Conditions ........................................................................................................................................... 2
Proposed Conditions ......................................................................................................................................... 2
SECTION 2 .................................................................................................................................................................. 3
Conditions and Requirements Summary ....................................................................................................... 3
SECTION 3 .................................................................................................................................................................. 3
Offsite Analysis .................................................................................................................................................. 3
SECTION 4 .................................................................................................................................................................. 3
Flow Control and Water Quality Facility Analysis Design ......................................................................... 3
Existing Site Hydrology .................................................................................................................................... 4
Water Quality System ....................................................................................................................................... 5
SECTION 5 .................................................................................................................................................................. 5
Conveyance System Analysis and Design ..................................................................................................... 5
SECTION 6 .................................................................................................................................................................. 5
Special Reports ................................................................................................................................................... 5
SECTION 7 .................................................................................................................................................................. 6
Other Permits ..................................................................................................................................................... 6
SECTION 8 .................................................................................................................................................................. 6
CSWPPP Analysis and Design ......................................................................................................................... 6
SECTION 9 .................................................................................................................................................................. 6
Bond Quantities ................................................................................................................................................. 6
SECTION 10 ................................................................................................................................................................ 6
Operation and Maintenance Manual .............................................................................................................. 6
List of Figures
Figure 1: TIR Worksheet
Figure 2: Topographic and Location Map
Figure 3: Basin Map
Figure 4: Soils Map
APPENDICES
APPENDIX A - Hydrology/Flow and WQ Drainage Design
APPENDIX B - Special Reports
APPENDIX C - Maintenance Manual and Summary
APPENDIX D - Bond Estimate
APPENDIX E - References
APPENDIX F - Grading and Drainage Plan
APPENDIX G - Construction Stormwater Pollution Prevention and Spill Plan
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
Technical Information Report – Drainage Report P1239-T18
Migizi Group, Inc. Page 2 of 6
INTRODUCTION/PROJECT OVERVIEW
This report is intended to meet the stormwater requirements of King County for the Tran Short
Plat dividing one lot with a home and detached garage into three separate lots with frontage
improvements.
The subject property is located at 16654 113th Ave SE in Renton in King County, Washington as
shown on the attached Topographic and Location Map, Figure 2. The Parcel Number is
0088000930. The Technical Information Report Worksheet is attached as Figure 1 of this report.
Legal Description:
THE WEST 140.07 FEET OF TRACT 3, BLOCK 11, AKER'S FARM NO. 9, ACCORDING TO THE
PLAT THEREOF RECORDED IN VOLUME 42 OF PLATS, PAGE 15, IN KING COUNTY,
WASHINGTON;
EXCEPT THE NORTH 50.0 FEET AND EXCEPT THAT PORTION CONVEYED TO KING
COUNTY FOR ROAD UNDER RECORDING NUMBER 6726885;
SITUATE IN THE CITY OF RENTON, COUNTY OF KING, STATE OF WASHINGTON.
SECTION 1
Existing Conditions
The project site is an approximately 0.5 acre rectangular shaped parcel. The property has an
existing home, shed, and detached garage with mowed lawn and several small trees. There is a
12 foot sewer easement on the southern boundary and a small easement on the west boundary
for a Quest facility. The lot slopes to the south at 5 to 10 percent. Migizi Group, Inc. has
previously prepared a Geotechnical Engineering Report for this project dated January 24, 2019.
The site is in the Soos Creek drainage basin and Duwamish-Green River watershed as shown on
the attached Figure 3.
The site soils are mapped as Alderwood gravelly sandy loam on 8 to 15 percent slopes, as shown
on the attached Figure 4.
Proposed Conditions
Plans call for the existing structures to be demolished and frontage improvements including
sidewalks, driveway entrances, and utilities for each new lot.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
Technical Information Report – Drainage Report P1239-T18
Migizi Group, Inc. Page 3 of 6
Existing Impervious Areas (to be removed)
On-Site sf acres %
Driveway 1,079 0.025 5.00%
Detached Garage 685 0.016 3.17%
Home 1,148 0.026 5.31%
Sidewalks 235 0.005 1.09%
Shed 100 0.002 0.46%
Total 3,247 0.075 15.03%
Off-Site
Sidewalk 1,097 0.025
Driveway Entrance 405 0.009
Total 1,502 0.034
Proposed Impervious Areas
Curb, Gutter, Sidewalk 2,172 0.050
Driveway Entrances 699 0.016
Total 2,871 0.066
Site 21,600 0.496
10 ft Property Dedication 1,279 0.029
Based on the total new and replaced impervious surfaces of approximately 2,871 sf, Minimum
Requirements #1 through #8 and all 5 special requirements apply to this project based on the
potential that the combined possible impervious area that may be added to the lot after it is
platted will be approximately 10,334 sf. Each new lot shall mitigate runoff from that lot onsite at
the time of construction utilizing dispersion.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
Technical Information Report – Drainage Report P1239-T18
Migizi Group, Inc. Page 4 of 6
SECTION 2
Conditions and Requirements Summary
Groundwater is shallow on site and was encountered at approximately 18 inches below existing
grades. Heavy mottling was also observed in the soils indicating poor drainage of onsite soils.
SECTION 3
Offsite Analysis
During our offsite analysis, we found no potential problems. Our analysis included the
following:
• Capacity Problems: We propose to fully disperse all stormwater runoff on site for each
lot at the time of construction. Offsite improvements will flow to the city storm system as
it currently does. No capacity problems exist due to the large amount of open space.
• Flooding: The site does not have a history of flooding and is mapped outside of the 100 yr
flood plain.
• Upland Erosion/Landslide Hazards: The site is relatively level with a low erosion risk.
• Channel Erosion/Outfall Location: None noted.
• Violations of surface quality water standards: None noted.
• No drainage systems were noted nearby other than roadside ditches. No known capacity
or other problems exist at this time.
• There are no stream inlets or outlets in the project area.
• No groundwater was encountered during our explorations. In our opinion, the
development will not affect groundwater levels in the area.
SECTION 4
Flow Control and Water Quality Facility Analysis Design
Planned improvements are shown below:
Proposed Impervious Areas
Curb, Gutter, Sidewalk 2,172 0.050
Driveway Entrances 699 0.016
Total 2,871 0.066
Site 21,600 0.496
10 ft Property Dedication 1,279 0.029
Existing Site Hydrology
Site hydrology currently sheet flows to the south on the majority of the parcel. The surface water
currently sheet flows across the property or infiltrates into the ground.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
Technical Information Report – Drainage Report P1239-T18
Migizi Group, Inc. Page 5 of 6
We propose limited or full dispersion on site based on the proposed buildings at the time of
construction permitting for each lot. Dispersion details are shown on the attached plans to assist
builders at that time.
Each lot was run with preexisting conditions of forest with Type C soils and the mitigated was
run with the expected amount of impervious area dispersed and the appropriate vegetative cover.
Expected increases in the 100-yr storm event can be considered de minimus. Each lot will increase
the expected flows during the 100 yr storm event by less than 0.1 cfs. The difference in the 100 yr
storm event on each lot totals less than 0.1 cfs for the entire plat and can be considered de
minimus. The calculations can be found in the appendix of this report.
Mitigated 100 yr storm
event flows (cfs)
Predeveloped 100 yr storm
event flows (cfs)
Difference
(cfs)
Lot 1 0.037568 0.01207 0.025498
Lot 2 0.06431 0.0204 0.04391
Lot3 0.037221 0.01207 0.025151
Total 0.094559
The proposed sidewalks and driveway entrances will flow as they currently do to the City storm
system.
Water Quality System
The project site is located in a basic water quality area. The amount of pollution generating
impervious surface (PGIS) is below the threshold of 5,000 sf.
In our opinion, the site does not pose a water quality issue.
SECTION 5
Conveyance System Analysis and Design
We propose an 18 inch ductile iron pipe sloped at 5.7 percent to replace the existing 18 inch ductile
iron pipe and ditch system along the frontage of 113th Ave SW. We propose no piping along the
frontage of SE 168th St.
SECTION 6
Special Reports
A Geotechnical Engineering Report was previously prepared for this project dated January 24,
2019 by Migizi Group, Inc.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
Technical Information Report – Drainage Report P1239-T18
Migizi Group, Inc. Page 6 of 6
SECTION 7
Other Permits
No special permits are required to our knowledge at this time other than a right-of-way permit.
SECTION 8
CSWPPP Analysis and Design
A CSWPPP has been prepared for this project and can be found in Appendix H of this report.
SECTION 9
Bond Quantities
A bond estimate can be found in Appendix E of this report. The total estimated bond amount is
90,823.70
SECTION 10
Operation and Maintenance Manual
An operation and maintenance manual has been prepared for this project and can be found in
Appendix C of this report. A King County maintenance covenant can be found in Appendix D.
APPROXIMATE SITE
LOCATION
P.O. Box 44840
Tacoma, WA 98448
Location Job Number Figure
DateTitle
16654 113th Ave SE
Renton, Washington 98055
Topographic and Location Map
2
04/15/19
P1239-T18
APPENDIX A
HYDROLOGY/FLOW AND WQ DRAINAGE
DESIGN
APPENDIX B
SPECIAL REPORTS
Geotechnical Engineering Report dated January 24, 2019 is incorporated by reference
APPENDIX C
MAINTENANCE MANUAL AND SUMMARY
C-1
APPENDIX C
MAINTENANCE MANUAL AND SUMMARY
POLUTION SOURCE CONTROL PROGRAM
What are pollution source controls and why are they needed?
Pollution source controls are actions taken by a person to reduce the amount of pollution reaching
the surface and groundwater. Controls are also called “best management practices” (BMPs).
For this site, we recommend that the owners prevent any oils or grease from entering the system.
It is also recommended that any oil spills or other chemical spills be cleaned up immediately and
any contaminated water should be prevented from entering the dispersion system to the extent
practical.
By preventing any pollutants from entering the system, they will be protecting the environment
and the drinking water supply.
Most pollution sources in residential areas are from vehicles. It is recommended that regular
maintenance be performed on any vehicles that will be kept on site to prevent any unnecessary
fluid leaks.
The best means of prevention is to not let the pollutants enter the system at all.
C-2
Stormwater Maintenance Manual
16654 113th Ave SE
Renton, Washington 98055
P/N 0088000930
April 15, 2019
P1239-T18
Prepared For:
Sang Tran
16654 113th Ave SE
Renton, Washington 98055
206-680-5568
Prepared By:
Migizi Group, Inc.
PO Box 44840
Tacoma, WA 98448
253-537-9400
C-3
Manual Purpose:
The purpose of this manual and the enclosed inspection sheets is to provide a maintenance plan
to ensure the continued proper operation of all stormwater facilities associated with your
property. Lack of maintenance could lead to local flooding, water damage, and costly repairs or
replacements of these or other infrastructure.
Project Description:
The stormwater system that serves this site was designed to accommodate runoff from single
family home impervious areas.
Stormwater System Description:
The stormwater system consists of the following items that are labeled on the enclosed site
drawing with the following symbols:
Catch Basins
Dispersion Trench
Landscaping
Maintenance Intervals:
Minimum twice per year or after each large rain event (April and September are recommended).
Project Construction Information:
Installation Contractor:
Name:
Address:
Phone:
Date of Construction:
Average annual cost estimate of maintenance: $100/yr
APPENDIX D
BOND ESTIMATE
APPENDIX E
REFERENCES
F-1
APPENDIX E
REFERENCES
• 2016 King County Surface Water Design Manual
• King County Website
• King County Assessor Website
• King County IMAP
APPENDIX F
GRADING AND DRAINAGE PLAN
APPENDIX G
CSWPPP
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
CSWPPP P1239-T18
Migizi Group, Inc.
Element 1: Marking Clearing Limits
The clearing limits for this project shall be flagged as shown on Sheet 1 of the TESC Plan
(attached). The clearing limits shall be marked with flagging or silt fencing. The area to be cleared
is approximately 21,600 sf.
Element 2: Establish Construction Access
Construction vehicle access will be limited to one route, the construction entrance/existing gravel
driveway.
If sediment is tracked off site, the public roads shall be cleaned thoroughly at the end of each day,
or more frequently should conditions require it.
Element 3: Control Flow Rates
The flow rates from this property will not be significantly increased due to the construction of
this project. The site soils have a low to moderate runoff potential due to shallow restrictive layer
and being relatively level. Temporary ditches may be constructed if runoff occurs.
Element 4: Install Sediment Controls
The following Best Management Practices (BMPs) are specified for this project:
• Temporary and Permanent Seeding, BMP C120
Element 5: Stabilize Soils
All exposed soils will be stabilized according to the following schedule:
• October 1 through April 30: No soils shall remain exposed and unworked for more than
2 days.
• May 1 through September 30: No soils shall remain exposed and unworked for more than
7 days.
BMPs used to stabilize soils shall be:
C120: Temporary and Permanent Seeding
All soils exposed shall be seeded by October 1 and reseeded if disturbed during the wet months.
Temporary erosion control seed mix shall consist of:
40% Chewing or annual blue grass
50% Perennial Rye
5% Redtop or colonial bent grass
5% White Dutch clover
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
CSWPPP P1239-T18
Migizi Group, Inc.
Permanent Seeding shall consist of: % weight % Purity % Germination
Perennial rye blend 30 98 90
(lolium perenne)
Chewing and Red fescue blend 70 98 90
(festuca rubra var. commutate or festuca rubra)
All disturbed soils must be amended and re-vegetated.
C140: Dust Control
In the event that dust control is needed, irrigation shall be used to wet soils and prevent wind
blown transport of soils.
Element 6: Protect Slopes
There are no steep slopes in the project area.
Element 7: Protect Drain Inlets
All grated catch basins within 500 feet of the site shall be protected with a catch basin insert.
Element 8: Stabilize Channels and Outlets
No channels or outlets exist in the project area or near it.
Element 9: Control Pollutants
Onsite fueling of equipment will not be permitted on this project.
Maintenance and repair of equipment or vehicles will not be permitted on this project.
Element 10: Control Dewatering
Dewatering is not anticipated on this project.
Element 11: Maintain BMPs
All BMPs will be inspected, maintained, and repaired to assure their continued performance. The
inspection schedule, maintenance, and repairs shall be conducted in accordance with industry
standards and/or manufacturer’s recommendations.
All sediment control BMPs shall be inspected weekly or after a runoff producing event during
the dry season and daily during the wet season. All temporary erosion and sediment control
BMPs will be removed within 30 days after final stabilization.
Sang Tran, phone number 206-680-5568, shall be responsible for the maintenance and inspection
of all BMPs or a suitable representative of his choosing.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
CSWPPP P1239-T18
Migizi Group, Inc.
Element 12: Manage the Project
The clearing and grading will occur only as necessary to permit the construction activities, i.e.,
construction phasing. A Certified Professional in Erosion and Sediment Control, Casey Lowe,
P.E., C.P.E.S.C., (cell: 253-229-8320), will be on call at all times.
Sang Tran, phone number 206-680-5568, shall be responsible for the maintenance and inspection
of all BMPs or a suitable representative of his choosing.
Element 13: Protect LID BMPs
All vegetated areas shall be protected from compaction or amended prior to final approval to
allow for the vegetated flow paths to function properly.
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
CSWPPP P1239-T18
Migizi Group, Inc.
ESC MAINTENANCE REPORT
Performed By:
Date:
Project Name:
Clearing Limits
Damage OK Problem
Visible OK Problem
Intrusions OK Problem
Other OK Problem
Mulch
Rills/Gullies OK Problem
Thickness OK Problem
Other OK Problem
Nets/Blankets
Rills/Gullies OK Problem
Ground Contact OK Problem
Other OK Problem
Plastic
Tears/Gaps OK Problem
Other OK Problem
Seeding
Percent Cover OK Problem
Rills/Gullies OK Problem
Mulch OK Problem
Other OK Problem
Sodding
Grass Health OK Problem
Rills/Gullies OK Problem
Other OK Problem
Silt Fence
Damage OK Problem
Sediment Build-up OK Problem
Concentrated Flow OK Problem
Other OK Problem
Brush Barrier
Damage OK Problem
Sediment Build-up OK Problem
Concentrated Flow OK Problem
Other OK Problem
Vegetated Strip
Damage OK Problem
Sediment Build-up OK Problem
Concentrated Flow OK Problem
Other OK Problem
Construction Entrance
Dimensions OK Problem
Sediment Tracking OK Problem
Vehicle Avoidance OK Problem
Other OK Problem
Tran – 16654 113th Ave SE, Renton, WA April 15, 2019
CSWPPP P1239-T18
Migizi Group, Inc.
Construction Road
Stable Driving Surf OK Problem
Vehicle Avoidance OK Problem
Other OK Problem
Sediment Trap/Pond
Sed. Accumulation OK Problem
Overtopping OK Problem
Inlet/Outlet Erosion OK Problem
Other OK Problem
Catch Basin Protection
Sed. Accumulation OK Problem
Damage OK Problem
Clogged Filter OK Problem
Other OK Problem
Interceptor Dike/Swale
Damage OK Problem
Sed. Accumulation OK Problem
Overtopping OK Problem
Other OK Problem
Pipe Slope Drain
Damage OK Problem
Inlet/Outlet OK Problem
Secure Fittings OK Problem
Other OK Problem
Ditches
Damage OK Problem
Sed. Accumulation OK Problem
Overtopping OK Problem
Other OK Problem
Outlet Protection
Scour OK Problem
Other OK Problem
Level Spreader
Damage OK Problem
Concentrated Flow OK Problem
Rills/Gullies OK Problem
Sed. Accumulation OK Problem
Other OK Problem
Miscellaneous
Wet Season Stockpile OK Problem
Other OK Problem
Comments:
Actions Taken:
Problems Unresolved:
Recommended Construction Sequence